# Doppler Constraints on Planetary Companions to Nearby Sun-like Stars:
An Archival Radial Velocity Survey of Southern Targets for Proposed NASA
Direct Imaging Missions 111This paper includes data gathered with the 6.5
meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Katherine Laliotis Department of Physics, The Ohio State University, 191 West
Woodruff Ave., Columbus, OH 43210, USA  Jennifer A. Burt Jet Propulsion
Laboratory, California Institute of Technology, 4800 Oak Grove Drive,
Pasadena, CA 91109, USA  Eric E. Mamajek Jet Propulsion Laboratory, California
Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Department of Physics and Astronomy, University of Rochester, Rochester, NY
14627-0171, USA  Zhexing Li Department of Earth and Planetary Sciences,
University of California, Riverside, CA 92521, USA  Volker Perdelwitz  Kimmel
fellow, Department of Earth and Planetary Sciences, Weizmann Institute of
Science, Rehovot, 76100, Israel  Hamburger Sternwarte, Universität Hamburg,
Gojenbergsweg 112, D-21029 Hamburg, Germany  Jinglin Zhao Department of
Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab,
University Park, PA 16802, USA  R. Paul Butler Earth & Planets Laboratory,
Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC
20015, USA  Bradford Holden UCO/Lick Observatory, Department of Astronomy and
Astrophysics, University of California at Santa Cruz, Santa Cruz, CA, 95064,
USA  Lee Rosenthal Cahill Center for Astronomy & Astrophysics, California
Institute of Technology, Pasadena, CA 91125, USA  B. J. Fulton Cahill Center
for Astronomy & Astrophysics, California Institute of Technology, Pasadena, CA
91125, USA  IPAC-NASA Exoplanet Science Institute, Pasadena, CA 91125, USA
Fabo Feng Tsung-Dao Lee Institute, Shanghai Jiao Tong University, 800
Dongchuan Road, Shanghai 200240, People’s Republic of China  Department of
Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University, 800
Dongchuan Road, Shanghai 200240, People’s Republic of China  Stephen R. Kane
Department of Earth and Planetary Sciences, University of California,
Riverside, CA 92521, USA  Jeremy Bailey School of Physics, University of New
South Wales, Sydney, NSW 2052, Australia  Brad Carter University of Southern
Queensland, Centre for Astrophysics, USQ Toowoomba, QLD 4350, Australia
Jeffrey D. Crane The Observatories of the Carnegie Institution for Science,
813 Santa Barbara Street, Pasadena, CA 91101, USA  Elise Furlan NASA Exoplanet
Science Institute, Caltech/IPAC, Mail Code 100-22, 1200 E. California Blvd.,
Pasadena, CA 91125, USA  Crystal L. Gnilka NASA Ames Research Center, Moffett
Field, CA 94035, USA  Steve B. Howell NASA Ames Research Center, Moffett
Field, CA 94035, USA  Gregory Laughlin Department of Astronomy, Yale
University, New Haven, CT, 06511, USA  Stephen A. Shectman The Observatories
of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena,
CA 91101, USA  Johanna K. Teske  Earth & Planets Laboratory, Carnegie
Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015, USA
C. G. Tinney School of Physics and Australian Centre for Astrobiology,
University of New South Wales, Sydney 2052, Australia  Steven S. Vogt UCO/Lick
Observatory, Department of Astronomy and Astrophysics, University of
California at Santa Cruz, Santa Cruz, CA, 95064, USA  Sharon Xuesong Wang
Department of Astronomy, Tsinghua University, Beijing 100084, People’s
Republic of China  Robert A. Wittenmyer University of Southern Queensland,
Centre for Astrophysics, USQ Toowoomba, QLD 4350, Australia

###### Abstract

Directly imaging temperate rocky planets orbiting nearby, Sun-like stars with
a 6-m-class IR/O/UV space telescope, recently dubbed the Habitable Worlds
Observatory, is a high priority goal of the Astro2020 Decadal Survey. To
prepare for future direct imaging surveys, the list of potential targets
should be thoroughly vetted to maximize efficiency and scientific yield. We
present an analysis of archival radial velocity data for southern stars from
the NASA/NSF Extreme Precision Radial Velocity Working Group’s list of high
priority target stars for future direct imaging missions (drawn from the
_HabEx_ , _LUVOIR_ , and _Starshade Rendezvous_ studies). For each star, we
constrain the region of companion mass and period parameter space we are
already sensitive to based on the observational baseline, sampling, and
precision of the archival RV data. Additionally, for some of the targets we
report new estimates of magnetic activity cycle periods, rotation periods,
improved orbital parameters for previously known exoplanets, and new candidate
planet signals that require further vetting or observations to confirm. Our
results show that for many of these stars we are not yet sensitive to even
Saturn-mass planets in the habitable zone, let alone smaller planets,
highlighting the need for future EPRV vetting efforts before the launch of a
direct imaging mission. We present evidence that the candidate temperate
super-Earth exoplanet HD 85512 b is most likely due to the star’s rotation,
and report an RV acceleration for $\delta$ Pav which supports the existence of
a distant giant planet previously inferred from astrometry.

Exoplanet astronomy (486), Exoplanet systems (484), Radial velocity (1332)

††facilities: UCO/Lick: The APF (Levy spectrograph), Magellan: Clay (Planet
Finder Spectrograph), Keck:I (HIRES), Gemini North: ‘Alopeke, Gemini South:
Zorro

##  1 Introduction

In order to further push the boundaries of the search for life elsewhere in
the universe, astronomers must advance our capabilities to detect temperate,
terrestrial planets orbiting Sun-like stars and to characterize their
atmospheres. To detect and spectrally characterize many such planets in
reflected light, it is expected that future space-based direct imaging (DI)
missions will employ starlight suppression technologies such as coronagraphs
or starshades, and survey of order $\sim$100 of the nearest Sun-like stars
(National Academies of Sciences, Engineering, and Medicine, 2018, 2021).
Habitable Exoplanet Observatory (_HabEx_) and the Large Ultraviolet Optical
Infrared Surveyor (_LUVOIR_), two proposed space-based DI mission concepts
considered by the 2020 Decadal Survey on Astronomy and Astrophysics
(Astro2020222https://www.nationalacademies.org/our-work/decadal-survey-on-
astronomy-and-astrophysics-2020-astro2020), were designed to obtain direct
atmospheric spectra and enable atmospheric characterization of small,
temperate planets (Gaudi et al., 2020; The LUVOIR Team, 2019). Pathways to
Habitable Worlds was a priority science theme in the Astro2020 Decadal
Survey333Released November 2021, near the completion of this study, which
included a recommendation444“Recommendation: After a successful mission and
technology maturation program, NASA should embark on a program to realize a
mission to search for biosignatures from a robust number of about $\sim$25
habitable zone planets and to be a transformative facility for general
astrophysics. If mission and technology maturation are successful, as
determined by an independent review, implementation should start in the latter
part of the decade, with a target launch in the first half of the 2040s.” for
NASA to work 555NASA Administator Bill Nelson recently announced plans in
December 2022 to the National Academies on the 50th anniversary of the Apollo
17 mission to proceed with the Decadal mission concept for a large UV/Vis/IR
space telescope with the name Habitable Worlds Observatory. towards launching
a 6-m class UV/Visible/IR space observatory in the early 2040s to spectrally
search for biosignatures in the atmospheres of directly-imaged temperate rocky
planets orbiting nearby stars666We note that an alternative approach to
discovering and characterizing rocky temperate exoplanets via space-based mid-
infrared nulling interferometry is being pursued for the Large Interferometer
for Exoplanets (LIFE) concept for ESA’s Voyage 2050 program (Quanz et al.,
2022; Dannert et al., 2022; Konrad et al., 2022; Hansen et al., 2022).. The
scale of the proposed observatory is intermediate between the HabEx and
LUVOIR-B concepts, and will require further technology and science maturation
and trade studies to converge on an architecture before project implementation
later in the 2020s. To inform trade studies and simulate mission yields, and
ultimately to fulfill the Astro2020 Decadal goal of searching for
biosignatures in the atmospheres of $\sim$25 imaged exo-Earths, one requires a
prioritized and carefully vetted target list.

The stars that are chosen for a future DI mission must meet criteria related
to their $T_{\rm eff}$, brightness (e.g. $V_{\rm{mag}}$), luminosity,
multiplicity, and distance from Earth. Of primary importance is the maximum
separation that a potentially habitable planet can achieve in its orbit around
its star, as seen from Earth. The habitable zone annuli scale as the square
root of the luminosity, such that one can define the Earth Equivalent
Insolation Distance (EEID) as $\sqrt{L/L_{\odot}}$ au, or in angular
separation $\theta_{EEID}$ = $\sqrt{L/L_{\odot}}$ $D_{pc}^{-1}$ =
$\sqrt{L/L_{\odot}}$ $\varpi$, for a star at distance $D_{pc}$ (parsecs)
(=1/$\varpi$) and parallax $\varpi$ (arcseconds). For a planet to be visible,
at least part of its orbit must be outside the inner working angles (IWA) for
the observatory’s means of starlight suppression – usually either a
coronagraph or starshade777For LUVOIR’s ECLIPS instrument (a coronagraph with
imaging and imaging spectroscopy), IWA = 3.5$\lambda$/$D$ for wavelength
$\lambda$ (between 0.2-2.0 $\mu$m) and aperture size $D$ (15 m for LUVOIR-A, 8
m for LUVOIR-B) (The LUVOIR Team, 2019). For _HabEx_ ($D$ = 4 m), IWA =
2.4$\lambda$/$D$ for the coronagraph ($\lambda$ range 0.48-1.8 $\mu$m,
corresponding to 62 mas for 0.5 $\mu$m) and 58 mas for the starshade over
$\lambda$ = 0.3-1.0 $\mu$m. Astro2020 recommended an observatory with $D$
$\simeq$ 6 m, however since multiple architectures will likely be considered,
the IWA is not yet defined – but should ultimately be a low multiple of
$\lambda$/$D$. – so that the incoming starlight does not overwhelm the
planet’s signal. Instrumentation limits constrain the primary candidate stars’
locations to be within a range where a $\sim$1 AU orbit would have a minimum
on-sky separation of $\sim$40 mas for _LUVOIR_ (The LUVOIR Team, 2019) and
larger separations are required for _HabEx_ and _Starshade Rendezvous_. Given
the limited number of Sun-like stars in the solar neighborhood, and the sizes
of their habitable zones, this places tight limits on the distance ranges and
sample sizes of targets well suited to Earth-analog searches with a DI
mission. An ideal observation candidate must both exhibit Sun-like
characteristics and be close enough that its habitable zone would be
accessible to a direct imaging mission’s instruments.

The accuracy to which the properties of the exoplanets’ atmosphere can be
determined will rely on precise measurements of the planets’ surface
gravities, which in turn require precise planet mass measurements (Batalha et
al., 2019). There are two practical methods for the foreseeable future for
measuring the masses of temperate rocky exoplanets orbiting Sun-like stars –
radial velocity and astrometry – both of which would require considerable
advancement to achieve this goal (Lovis & Fischer, 2010; Quirrenbach, 2010;
National Academies of Sciences, Engineering, and Medicine, 2018). It is
generally acknowledged, however, that Extreme Precision Radial Velocity (EPRV)
measurements obtained via spectrographs with single measurement precisions <
10 c$\rm m\,s^{-1}$ are likely the most direct route to detecting Earth
analogs around Sun-like stars (National Academies of Sciences, Engineering,
and Medicine, 2018). The current generation of RV instruments are beginning to
demonstrate single measurement precisions at the 30-50 c$\rm m\,s^{-1}$ level
(see, e.g., Pepe et al., 2021; Brewer et al., 2020; Trifonov et al., 2021;
Seifahrt et al., 2018). Further improvements to reach the 10 c$\rm m\,s^{-1}$
level will require advances in sustained instrument stability, wavelength
calibration, and data extraction and analysis techniques with a focus on
methods for mitigating stellar variability.

Exploring solutions to these challenges that prevent mass measurements for
Earth analogs was the goal of the Extreme Precision Radial Velocity (EPRV)
Working Group chartered by NASA and the
NSF888https://exoplanets.nasa.gov/exep/NNExplore/EPRV/.. The EPRV Working
Group was charged with devising a path towards developing methods and
facilities that will be capable of accurately measuring the masses of
temperate terrestrial exoplanets orbiting Sun-like stars999The final NASA
concept study reports for the _HabEx_ , _LUVOIR_ , and _Starshade Rendezvous_
reports for the Astro 2020 Decadal Survey are posted at:
https://science.nasa.gov/astrophysics/2020-decadal-survey-planning. The
Working Group’s final report (Crass et al., 2021) includes recommendations for
advancements in stellar activity and telluric mitigation, instrument
efficiency and accuracy, and research and analysis techniques.

In parallel to these advancements in RV instrumentation and analysis, there
must also be a concerted effort to better understand the potential DI target
stars. One way to do this is by studying archival RV data sets taken using
previous, less precise ($\sigma_{\rm{RV}}$ < 5 $\rm m\,s^{-1}$), generations
of RV spectrographs. The EPRV Working Group curated a list of $\sim$100
nearby, Sun-like (F9-K7) stars that are promising candidates for a future DI
mission, many of which have already been included in multiple RV surveys over
the past three decades as the community’s interests have often been tied to
bright G and K dwarfs.

In this study, we analyze archival radial velocity and stellar activity data
from the _HARPS_ , _HIRES_ , _UCLES_ , _APF_ , and _PFS_ instruments for 49
southern hemisphere stars identified as promising future DI mission targets.
We perform planet injection and recovery tests to assess the completeness of
the existing RV data as a function of planet mass and orbital period, so as to
identify regions of mass/period parameter space in which planet signals might
still be hiding. Any mass/period gaps identified in this work can then be
filled by directed future observations, contributing to the completeness of
the target star list data. In preparing the RV data sets for the
injection/recovery analysis we first identify and remove significant signals
from the RV time series. This results in the detection of numerous, previously
confirmed exoplanets; a number of new planet candidates; and rotation and
magnetic activity cycles within the data.

The structure of this paper is as follows. In §2, we discuss the stars chosen
for this project and the types and sources of the data analyzed. In §3 we
detail the sources and treatments of the data sets used in this work. In §4,
we present the different methods of analysis used to characterize the stars’
existing RV sensitivity. In §5-7 we explain the results of our analysis. Each
star on the target list has a subsection including updates to parameters of
any known planets, evidence of strong stellar activity cycles, and any new
signals recovered. We address those targets which lacked any significant
signals in §7. §8 contains a general discussion of our results, including
highlights of the analysis carried out in this work and exploration of major
gaps we have identified in the archival RV data. Finally, in §9 we cover the
conclusions drawn from this work, and identify future work necessary before
any target list is finalized for a direct imaging mission concept. The full
set of figures for each target, including radial velocity, S-index,
completeness contour, and, if relevant, H$\alpha$ activity and speckle imaging
plots can be found in the online journal.

##  2 Stellar Target List

Our list of target stars is drawn from the EPRV Working Group, and a full
description of the selection process and criteria considered can be found in
its final
presentation101010https://exoplanets.nasa.gov/internal$\\_$resources/1556/ and
report (Crass et al., 2021). In brief, the Working Group cross-matched target
lists provided by the _HabEx_ , _LUVOIR-A_ , _LUVOIR-B_ , and _Starshade
Rendezvous_ teams (Gaudi et al., 2020; The LUVOIR Team, 2019; Seager et al.,
2018) to assemble a combined list of potential target stars. It then compiled
information on the stars’ effective temperatures, apparent magnitudes,
rotational velocities, metallicities, and surface gravities, among other
traits. From this catalog, they culled those stars with spectral types from
F7-K9, projected rotational velocities $v$sin$i$ $<$ 5 km s-1, and that appear
on at least two of the mission concept target lists. Stars were not eliminated
based on knowledge of their stellar activity levels as the characterization
and mitigation of stellar variability is an active field and we may yet
overcome the obstacles it presents. The resulting list includes 101 stars
(Figure 1).

For this work, we have chosen to focus primarily on the 53 stars from this
list located in the southern hemisphere111111It should be noted that this list
was assembled before the Astro2020 Decadal Survey was released, which
recommended a 6-m-class space telescope. From subsequent analysis and
literature survey (Mamajek & Stapelfeldt, in prep.), ten of the sample stars
in Table 1 may be undesirable targets for a survey for potentially habitable
exoplanets with a 6-m-class space telescope: 4 systems have habitable zones
prohibitively close to their stars (HD 85512 [EEID = 36 mas], HD 23356 [EEID =
40 mas], HD 125072 [EEID = 49 mas], HD 196761 [EEID = 36 mas]), 5 stars have
close ($<$3″) companions (HD 16160, HD 147584, HD 13445A, HD 160346), one has
high luminosity and its HZ rocky planets may have planet-star brightness
ratios that are prohibitive low (HD 188512). These ten stars will be omitted
from a NASA ExEP mission target list meant to inform precursor science for the
Habitable Worlds Observatory. (Figure 2) due to the recent publication of
archival HARPS RV data that is now available on the RVBank website (Trifonov
et al., 2020).

Table 1: Sample and Stellar Parameters

HD | GJ | $T_{\rm eff}$ | $\log g$ | $\left[{\rm Fe}/{\rm H}\right]$ | Ref. | Spec. Type | Ref. | $\log{L/L_{\sun}}$ | Ref.(L)
---|---|---|---|---|---|---|---|---|---
693 | 10 | 6169 | 4.07 | -0.34 | 1 | F8V Fe-0.8 CH-0.5 | 2 | 0.477 | 3
1581 | 17 | 5977 | 4.51 | -0.18 | 4 | F9.5V | 2 | 0.101 | 3
2151 | 19 | 5873 | 3.98 | -0.04 | 5 | G0V | 2 | 0.541 | 27
4628 | 33 | 5009 | 4.62 | -0.24 | 1 | K2V | 6 | -0.523 | 3
7570 | 55 | 6111 | 4.36 | 0.17 | 7 | F9V Fe+0.4 | 2 | 0.302 | 3
13445 | 86A | 5217 | 4.56 | -0.23 | 9 | K1V | 2 | -0.389 | 3
14412 | 95 | 5368 | 4.55 | -0.47 | 10 | G8V | 2 | -0.351 | 3
16160 | 105A | 4866 | 4.66 | -0.12 | 11 | K3V | 8 | -0.549 | 3
20766 | 136 | 5713 | 4.48 | -0.20 | 12 | G2V | 2 | -0.100 | 3
20794 | 139 | 5398 | 4.41 | -0.41 | 13 | G8V | 2 | -0.184 | 3
20807 | 138 | 5837 | 4.47 | -0.22 | 12 | G1V | 8 | 0.007 | 3
22049 | 144 | 5050 | 4.60 | -0.09 | 5 | K2V | 8 | -0.471 | 3
23249 | 150 | 5057 | 3.80 | 0.08 | 15 | K1IV | 6 | 0.500 | 16
23356 | … | 4960 | 4.60 | -0.09 | 9 | K2.5V | 2 | -0.515 | 3
26965 | 166A | 5128 | 4.37 | -0.37 | 17 | K0.5V | 2 | -0.364 | 3
30495 | 177 | 5870 | 4.54 | 0.04 | 18 | G1.5V CH-0.5 | 2 | -0.015 | 3
32147 | 183 | 4745 | 4.57 | 0.19 | 9 | K3+V | 6 | -0.537 | 3
38858 | 1085 | 5719 | 4.49 | -0.23 | 13 | G2V | 6 | -0.083 | 3
39091 | 9189 | 6003 | 4.42 | 0.09 | 4 | G0V | 2 | 0.186 | 3
50281 | 250A | 4758 | 4.92 | 0.14 | 11 | K3.5V | 6 | -0.658 | 3
69830 | 302 | 5390 | 4.39 | -0.05 | 12 | G8+V | 2 | -0.216 | 3
72673 | 309 | 5243 | 4.46 | -0.41 | 4 | G9V | 2 | -0.394 | 3
75732 | 324A | 5328 | 4.58 | 0.46 | 1 | K0IV-V | 6 | -0.197 | 3
76151 | 327 | 5776 | 4.54 | 0.11 | 19 | G2V | 8 | -0.013 | 3
85512 | 370 | 4400 | 4.36 | -0.26 | 13 | K6V(k) | 2 | -0.778 | 3
100623 | 432A | 5189 | 4.68 | -0.37 | 11 | K0-V | 2 | -0.432 | 3
102365 | 442A | 5629 | 4.44 | -0.29 | 4 | G2V | 2 | -0.074 | 3
102870 | 449 | 6083 | 4.08 | 0.24 | 5 | F8.5IV-V | 20 | 0.576 | 3
114613 | 9432 | 5672 | 3.95 | 0.12 | 15 | G4IV | 2 | 0.626 | 3
115617 | 506 | 5556 | 4.35 | -0.02 | 21 | G6.5V | 8 | -0.078 | 3
125072 | 542 | 4899 | 4.55 | 0.28 | 9 | K3IV | 2 | -0.466 | 3
131977 | 570A | 4744 | 4.76 | 0.12 | 11 | K4V | 8 | -0.653 | 3
136352 | 582 | 5664 | 4.39 | -0.34 | 4 | G2-V | 2 | 0.012 | 3
140901 | 599A | 5586 | 4.45 | 0.09 | 9 | G7IV-V | 2 | -0.088 | 3
146233 | 616 | 5808 | 4.44 | 0.04 | 18 | G2Va | 8 | 0.039 | 3
147584 | 624 | 6030 | 4.43 | -0.08 | 9 | F9V | 2 | 0.134 | 3
149661 | 631 | 5289 | 4.61 | 0.05 | 1 | K0V(k) | 2 | -0.335 | 3
156026 | 664 | 4600 | 4.70 | -0.34 | 9 | K5V(k) | 2 | -0.803 | 3
160346 | 688 | 4808 | 4.56 | -0.08 | 9 | K2.5V | 6 | -0.480 | 22
160691 | 691 | 5845 | 4.27 | 0.35 | 5 | G3IV-V | 2 | 0.278 | 3
165341 | 702A | 5314 | 4.51 | 0.05 | 1 | K0-V | 8 | -0.221 | 23
188512 | 771A | 5117 | 3.64 | -0.19 | 15 | G8IV | 8 | 0.780 | 16
190248 | 780 | 5566 | 4.24 | 0.32 | 13 | G8IV | 2 | 0.097 | 3
192310 | 785 | 5104 | 4.54 | 0.06 | 9 | K2+V | 2 | -0.394 | 3
196761 | 796 | 5415 | 4.43 | -0.31 | 4 | G7.5IV-V | 8 | -0.252 | 3
203608 | 827 | 6150 | 4.35 | -0.66 | 9 | F9V Fe-1.4 CH-0.7 | 2 | 0.166 | 3
207129 | 838 | 5937 | 4.49 | 0.00 | 4 | G0V Fe+0.4 | 2 | 0.082 | 3
209100 | 845 | 4649 | 4.63 | -0.19 | 9 | K4V(k) | 2 | -0.654 | 3
216803 | 879 | 4647 | 4.88 | 0.07 | 24 | K4+Vk | 2 | -0.707 | 3

Note. — References: (1) Takeda et al. (2005), (2) Gray et al. (2006), (3)
Stassun et al. (2019), (4) Sousa et al. (2008), (5) Jofré et al. (2014), (6)
Gray et al. (2003), (7) Ramírez et al. (2014), (8) Keenan & McNeil (1989), (9)
Ramírez et al. (2013), (10) Santos et al. (2004), (11) Valenti & Fischer
(2005), (12) Adibekyan et al. (2016), (13) Tsantaki et al. (2013), (14)
Gonzalez et al. (2010), (15) Maldonado & Villaver (2016), (16) Brewer et al.
(2016) (17) Montes et al. (2018), (18) Spina et al. (2016), (19) Mahdi et al.
(2016), (20) Gray et al. (2001), (21) Sousa et al. (2018), (22) Luck (2017),
(23) Schofield et al. (2019), (24) Santos et al. (2001), (25) Luminosity for
this star was calculated using the Virtual Observatory SED Analyzer version
7.0 (VOSA; Bayo et al., 2008) assuming zero extinction, $log(g)=4.0$, and BT-
Settl-AGSS2009 model spectra. This produced a best fit log(L/$L_{\sun}$) value
of $+0.5407\pm 0.0065$ for HD 2151.

Figure 1: Stars identified by the EPRV Working Group as potential targets for
future direct imaging missions such as HabEx and LUVOIR that would aim to
detect and characterize Earth analog exoplanets. This work focuses primarily
on the stars located in the southern hemisphere.  Figure 2: HR diagram
containing the target stars in this study. The dashed blue lines are MIST V1.2
evolutionary tracks from Choi et al. (2016) covering masses 0.7 - 1.4 M⊙ over
age range 100Myr - 14 Gyr. The tracks adopts protosolar mix (initial
$Y=0.2703$, $Z=0.0142857$, [$\alpha$/Fe]=0, $v/v_{crit}=0$). The Sun is
depicted using the $\odot$ symbol.

##  3 Data

###  3.1 Radial Velocities

In this work, we include data sets consisting of unbinned radial velocity
measurements from five different instruments: the High Accuracy Radial
Velocity Planet Searcher (HARPS, on the ESO 3.6m telescope, Mayor et al.,
2003), the HIgh REsolution Spectrometer (HIRES, on the 10m Keck I telescope,
Vogt et al., 1994), the Levy spectrometer (on the 2.4m Automated Planet Finder
(APF) telescope, Vogt et al., 2014), the Planet Finder Spectrometer (PFS, on
the 6.5m Magellan Clay telescope, Crane et al., 2006, 2008, 2010), and the
University College London Échelle Spectrograph (UCLES, on the 3.9m Anglo-
Australian Telescope, Diego et al., 1990). Table 2 lists the number of
archival RV epochs (binned at a 12 hour cadence) acquired by each facility.
All radial velocity and activity indicator measurements for each star will be
provided in a machine readable table alongside this paper in their original,
unbinned, form (Table 3).

The _HARPS_ instrument uses multiple observing fibers; one directed at the
stellar target, and one directed instead at a Th-Ar calibration lamp. The
calibration lamp serves as a wavelength reference for the stellar spectra.
_HARPS_ has a resolving power of $\sim$115,000 and a spectral grasp of
3800-6900 Å (Pepe et al., 2002; Cosentino et al., 2012). All _HARPS_ RV data
used in this work were downloaded from the _HARPS_ RVBank
archive121212https://www2.mpia-hd.mpg.de/homes/trifonov/HARPS$\\_$RVBank.html
(Trifonov et al., 2020). These RVBank velocities were generated using the
SERVAL pipeline (Zechmeister et al., 2020) which uses a template matching
approach (Zechmeister et al., 2018). For each star, SERVAL creates a high S/N
template spectrum by shifting and co-adding all individual spectra of that
star. The template is then used to derive RVs from the same observed spectra
by using a $\chi^{2}$-minimization approach. The final velocities were checked
for any nightly systematic errors that can be corrected in order to increase
the precision of the RV data set.

_HIRES_ , _APF_ , _UCLES_ , and _PFS_ are Iodine-based instruments, meaning
that they each include a cell of gaseous I2 within the converging beam of
their respective telescopes. Incoming stellar spectra are imprinted in a high-
density forest of I2 lines in the 5000-6200Å band pass. These lines act both
as a calibrator for the wavelengths of the stellar spectra and as a
representative for the point-spread function (PSF) of each instrument. After
extraction of the iodine region of the spectrum, the stellar spectrum must be
deconvolved from the I2 absorption lines such that the wavelengths, instrument
PSFs, and Doppler shifts may be extracted. This is accomplished by splitting
each iodine region into 2Å chunks, and then analyzing them via the spectral
synthesis technique outlined in Butler et al. (1996). A weighted mean of all
the Doppler velocities of the individual chunks is taken, and serves as the
final Doppler velocity for each individual observation. The standard deviation
of all the 2Å chunks ($\sim$800 for _PFS_ and $\sim$700 for the _APF_ and
_HIRES_ ) constitutes the total internal uncertainty for each velocity
measurement. The timestamps for each iodine-based RV are converted from their
pipeline produced MJD values to BJDTDB timestamps using the Pexo modeling
package (Feng et al., 2019b).

We note that three of the above spectrographs have undergone instrumental
upgrades since their deployment. The _HIRES_ detector was replaced with a new
mosaic CCD in August 2004, _HARPS_ moved to the use of an octagonal science
fiber in 2015 and in 2018, the _PFS_ detector was replaced with a smaller
pixel 10k$\times$10k detector and the slit used for I2 observations was
changed from 0.5” to 0.3”. In all three cases, we treat the data taken before
and after the upgrade as coming from two separate instruments, identified in
our RV data sets and figures as -Pre and -Post velocities.

The instruments cover spectral ranges of 3700-8000Å for _HIRES_ , 3700-9000Å
for _APF_ , 3900-6700Å for _PFS_ , and 4800-8400Å, for _UCLES_ , however the
radial velocity measurements are made using only the 5000-6200Å wavelength
region. The typical spectral resolutions for each instrument are: $R$ $\simeq$
90,000 for the _APF_ , 60,000 for _HIRES_ , 45,000 for _UCLES_ , and
80,000/130,000 for _PFS_ pre-/post-upgrade, respectively.

The _HIRES_ data was obtained from the public Earth Bound Planet Search
archive131313https://ebps.carnegiescience.edu/data/hireskeck-data, which
provides updates to the Butler et al. (2017) _HIRES_ data catalog. The final
HIRES data point included in this analysis was taken on 26 December 2017. The
_APF_ , _PFS_ , and _UCLES_ data were provided by the corresponding instrument
teams.

For each instrument’s data set for a given star, we apply a robust sigma
clipping where any points further than 5$\sigma$ from the mean are discarded
as outliers. We visually inspect the points identified as outliers in each
case, and find that in practice this analysis flags 1-3 data points per
instrument per star, which is generally a small percentage of the overall
data. Once each instrument’s outliers are removed, we combine the cleaned data
sets from each instrument into a single list. We include a column of data
tracking which instrument was used to generate each measurement, so that later
analysis can determine offsets between instruments.

Table 2: Number of Archival RV Epochs Analyzed for Each Target Star

HD |  aHARPS | HIRES | UCLES |  aPFS | APF | HD |  aHARPS | HIRES | UCLES |  aPFS | APF
---|---|---|---|---|---|---|---|---|---|---|---
HD693 | 16 [16/0] | 0 [0/0] | 0 | 0 [0/0] | 0 | HD85512 | 580 [517/63] | 7 [0/7] | 31 | 44 [38/6] | 0
HD1581 | 329 [262/67] | 0 [0/0] | 119 | 0 [0/0] | 0 | HD100623 | 4 [4/0] | 64 [16/48] | 104 | 40 [34/6] | 0
HD2151 | 34 [34/0] | 0 [0/0] | 163 | 0 [0/0] | 0 | HD102365 | 82 [78/4] | 13 [0/13] | 187 | 33 [22/11] | 0
HD4628 | 42 [37/5] | 117 [0/117] | 0 | 0 [0/0] | 71 | HD102870 | 8 [8/0] | 0 [0/0] | 0 | 0 [0/0] | 59
HD7570 | 19 [19/0] | 0 [0/0] | 60 | 0 [0/0] | 0 | HD104304 | 26 [0/26] | 42 [0/42] | 0 | 0 [0/0] | 14
HD13445 | 11 [0/11] | 0 [0/0] | 74 | 0 [0/0] | 0 | HD114613 | 20 [13/7] | 45 [0/45] | 244 | 39 [27/12] | 0
HD14412 | 26 [0/26] | 139 [24/115] | 28 | 12 [11/1] | 0 | HD115617 | 229 [224/5] | 157 [0/157] | 169 | 31 [28/3] | 0
HD16160 | 45 [45/0] | 76 [0/76] | 0 | 0 [0/0] | 83 | HD125072 | 74 [55/19] | 0 [0/0] | 86 | 0 [0/0] | 0
HD20766 | 26 [26/0] | 0 [0/0] | 58 | 0 [0/0] | 0 | HD131977 | 22 [22/0] | 0 [0/0] | 0 | 0 [0/0] | 0
HD20794 | 260 [187/73] | 0 [0/0] | 147 | 21 [18/3] | 0 | HD136352 | 249 [242/7] | 28 [0/28] | 169 | 24 [21/3] | 0
HD20807 | 99 [76/23] | 0 [0/0] | 99 | 16 [13/3] | 0 | HD140901 | 27 [27/0] | 0 [0/0] | 117 | 27 [23/4] | 0
HD22049 | 28 [24/4] | 89 [0/89] | 0 | 0 [0/0] | 0 | HD146233 | 177 [119/58] | 112 [28/84] | 81 | 15 [15/0] | 0
HD22484 | 26 [0/26] | 8 [0/8] | 0 | 0 [0/0] | 71 |  HD147584b | 1 [1/0] | 0 | 0 | 0 [0/0] | 0
HD23249 | 116 [76/40] | 55 [20/35] | 95 | 0 [0/0] | 29 | HD149661 | 12 [12/0] | 43 [31/12] | 14 | 0 [0/0] | 0
HD23356 | 14 [14/0] | 71 [12/59] | 0 | 0 [0/0] | 0 | HD156026 | 0 [0/0] | 27 [18/9] | 11 | 54 [35/19] | 59
HD26965 | 103 [82/21] | 163 [7/156] | 112 | 24 [20/4] | 13 | HD160346 | 34 [34/0] | 0 [0/0] | 0 | 0 [0/0] | 0
HD30495 | 44 [35/9] | 6 [0/6] | 0 | 0 [0/0] | 0 | HD160691 | 163 [161/2] | 0 [0/0] | 178 | 14 [12/2] | 0
HD32147 | 41 [37/4] | 157 [0/157] | 0 | 27 [22/5] | 65 |  HD165341b | 7 [7/0] | 0 | 0 | 0 [0/0] | 0
HD38858 | 103 [91/12] | 69 [16/53] | 0 | 0 [0/0] | 0 | HD188512 | 17 [17/0] | 57 [7/50] | 0 | 0 [0/0] | 0
HD39091 | 49 [42/7] | 0 [0/0] | 77 | 37 [0/37] | 0 | HD190248 | 391 [279/112] | 0 [0/0] | 236 | 0 [0/0] | 0
HD43834 | 26 [0/26] | 0 [0/0] | 140 | 24 [21/3] | 0 | HD192310 | 432 [348/84] | 137 [0/137] | 171 | 19 [19/0] | 0
HD50281 | 12 [12/0] | 52 [29/23] | 0 | 0 [0/0] | 33 | HD196761 | 37 [27/10] | 63 [30/33] | 49 | 29 [21/8] | 0
HD69830 | 273 [265/8] | 154 [0/154] | 24 | 29 [29/0] | 87 |  HD203608b | 7 [7/0] | 0 | 0 | 0 [0/0] | 0
HD72673 | 158 [115/43] | 77 [21/56] | 63 | 15 [15/0] | 0 | HD207129 | 111 [98/13] | 0 [0/0] | 123 | 22 [15/7] | 0
HD75732 | 2 [2/0] | 220 [23/197] | 0 | 0 [0/0] | 25 | HD209100 | 137 [100/37] | 0 [0/0] | 0 | 0 [0/0] | 0
HD76151 | 7 [7/0] | 0 [0/0] | 0 | 0 [0/0] | 0 | HD216803 | 11 [11/0] | 16 [6/10] | 15 | 0 [0/0] | 0

aafootnotetext: The total number of _HARPS_ _HIRES_ and _PFS_ RV epochs are
followed by a break down of how many data points were taken before and after
the instruments’ upgrades (see Section 3) as the pre- and post- upgrade time
series are treated as coming from two different instruments. bThese stars have
thousands of individual observations all taken over observational baselines
covering less than 1 week of time, making them incompatible with exoplanet
search and injection/recovery analyses. We therefore remove them from further
consideration in this paper.

Table 3: Full Timeseries Data for Each Target Star

Starname |  BJDTBD |  RV [$\rm m\,s^{-1}$ ] |  RVerr [$\rm m\,s^{-1}$ ] | Instrument | S-index |  S-indexerr |  H$\alpha$ |  H$\alpha_{err}$ | File Name
---|---|---|---|---|---|---|---|---|---
HD115617 | 2453026.86393 | -3.12 | 0.95 | HARPS-Pre | 0.1404 | 0.0026 | -1.0 | -1.0 | 2004-01-22T08:41:20
HD115617 | 2453026.86533 | -3.98 | 0.98 | HARPS-Pre | 0.1426 | 0.0032 | -1.0 | -1.0 | 2004-01-22T08:43:22
HD115617 | 2453026.86674 | -2.59 | 0.96 | HARPS-Pre | 0.1490 | 0.0028 | -1.0 | -1.0 | 2004-01-22T08:45:26
HD115617 | 2453026.86822 | -3.02 | 0.94 | HARPS-Pre | 0.1420 | 0.0027 | -1.0 | -1.0 | 2004-01-22T08:47:29
HD115617 | 2453026.86967 | -5.38 | 0.95 | HARPS-Pre | 0.1471 | 0.0025 | -1.0 | -1.0 | 2004-01-22T08:49:33
HD115617 | 2453026.87111 | -2.8 | 0.95 | HARPS-Pre | 0.1414 | 0.0028 | -1.0 | -1.0 | 2004-01-22T08:51:38
HD115617 | 2453026.87254 | -4.59 | 0.95 | HARPS-Pre | 0.1506 | 0.0026 | -1.0 | -1.0 | 2004-01-22T08:53:42
HD115617 | 2453026.87393 | -3.23 | 0.94 | HARPS-Pre | 0.1423 | 0.0025 | -1.0 | -1.0 | 2004-01-22T08:55:46
HD115617 | 2453026.87541 | -1.22 | 0.94 | HARPS-Pre | 0.1468 | 0.0025 | -1.0 | -1.0 | 2004-01-22T08:57:49
HD115617 | 2453026.87686 | -4.58 | 0.94 | HARPS-Pre | 0.1481 | 0.0024 | -1.0 | -1.0 | 2004-01-22T08:59:54
⋮ | ⋮ | ⋮ | ⋮ | ⋮ | ⋮ | ⋮ | ⋮ | ⋮ | ⋮

††footnotetext: This table contains, for each target, the full set of
observations of RVs, S-indices, and H-alpha from each instrument included in
this study. Complete time series data for each target in the format above can
be found in the online journal.

There are three stars that, despite having a significant number of _HARPS_
observations, cover time baselines incompatible with our science case. HD
203608 and HD 165341 were both observed over a single week, and HD 147584 was
observed over a single night. None of these stars have been targeted by the
other instruments in our study, and so we remove them from further
consideration.

###  3.2 S-index Measurements

A major challenge when classifying periodic signals seen in Doppler velocity
data is determining whether those signals are due to planetary companions or
the star itself. Stellar variability is produced by a variety of surface
phenomena that occur and evolve across a range of time scales, but they can be
grouped into four broad categories. Acoustic waves within the star cause
patches of the surface to rise and fall periodically, creating RV oscillations
at the few $\rm m\,s^{-1}$ level over timescales of minutes (Bouchy & Carrier,
2001; Nordlund et al., 2009). Granulation is due to motion within stellar
convective cells as hot plasma wells up to the surface before radiatively
cooling and sinking back down via intergranular lanes. This process takes
anywhere from 20 minutes to 1 day depending on the granule size and again
results in RV shifts at the few $\rm m\,s^{-1}$ level (Cegla et al., 2019;
Meunier et al., 2015; Meunier & Lagrange, 2019). Active regions are areas of
increased magnetic flux on the stellar surface such as star spots, plages, and
faculae that transit across the visible hemisphere of the star as it rotates.
They generally persist for multiple rotation periods and induce cyclic RV
variations at the 1-10 $\rm m\,s^{-1}$ level each time they pass over the
star’s face (Saar & Donahue, 1997; Lockwood et al., 2007; Haywood et al.,
2016). Finally, stellar magnetic cycles are driven by stellar dynamos, which
are maintained through differential rotation at the tachocline – the interface
between a star’s radiative and convective layers. These magnetic cycles vary
slowly, generally exhibiting periods of 5-15 years for Sun-like stars, and can
induce RV variations up to 20 $\rm m\,s^{-1}$ over that time span (Meunier et
al., 2010; Makarov, 2010; Dumusque et al., 2011). In our case of working
primarily with radial velocity data sets taken at relatively low cadence
(e.g., once per week or month) the latter two varieties, active regions and
magnetic cycles, produce the highest rate of false positive signals.

A well-established method for tracing a star’s variability level is the use of
stellar activity indicators, which compare the amount of flux inside activity
sensitive lines to the flux in nearby continuum regions. The most common
stellar activity indicators for Sun-like stars are derived from measurement of
the emission reversal at the cores of the Fraunhofer H and K lines of Ca II
located at at 3968 Å and 3934 Å, respectively, which trace chromospheric
activity. As the Ca II line core emission is generated in regions of
concentrated magnetic fields, these lines serve as a proxy for the number of
spots on the star, and often show variations with the star’s rotational
period. Because stars in the active phases of their magnetic cycles tend to
produce more sunspots (Schwabe, 1843), activity indicators based on the Ca II
lines can also act as a tracer of long-term magnetic cycles.

For Sun-like stars, the best known Ca II activity indicator is the S-index
which compares the flux in the cores of the H & K lines to two nearby
continuum regions denoted as the R and V filters (Wilson, 1968; Duncan et al.,
1991). The S-index generally takes the form:

$S_{\rm{index}}=\frac{H+K}{R+V}$ (1)

and is often calibrated to the original Mt. Wilson S-index survey which ran
from 1966-1983 (Duncan et al., 1991) to allow for comparisons between
facilities. Over the Mt. Wilson survey’s two-decade span, 111 F2-M2 stars were
monitored continuously from Mt. Wilson and 60% were seen to exhibit magnetic
cycles on a 5-15 year time scale (Baliunas et al., 1995). These time series
make clear that the range of variability exhibited by the continuously
monitored Mt. Wilson stars is much more diverse than what we observe in the
Sun.

To search for evidence of these long term magnetic cycles, in addition to
shorter term rotational periods, in our RV data sets we first derive an
S-index value from each RV spectrum. For the _HIRES_ _APF_ and _PFS_ data
sets, these S-index values are generated automatically as part of the data
reduction pipelines and further details can be found in Butler et al. (2017)
and Burt et al. (2021). We determine errors for each instrument’s S-index
values taking into account photon noise. The resulting uncertainty, by error
propagation, is:

$\sigma_{\rm{S}}=\rm{S}\cdot\sqrt{\frac{\sigma^{2}_{H}+\sigma^{2}_{K}}{(H+K)^{2}}+\frac{\sigma^{2}_{R}+\sigma^{2}_{V}}{(R+V)^{2}}}$
(2)

In each case we have used a set of overlapping target stars to calibrate the
instrument’s S-index measurements to the Mt. Wilson survey so that they can be
considered together without concerns for large scaling offsets. In some cases,
however, the Mt. Wilson calibration is based on a small number of stars and
may introduce non-astrophysical offsets between the instruments. To account
for this, our analysis allows us to fit for offsets between the S-index data
sets, as described more thoroughly in Section 4.1.

The _HARPS_ RVBank data does not yet provide S-index measurements, and so we
instead make use of the methodology described in Perdelwitz et al. (2021).
Specifically, we use a set of narrow bands close to the Ca II line cores,
along with PHOENIX synthetic spectra (Husser et al., 2013), to derive
$R_{\mathrm{HK}}^{\prime}$. We then convert these into S-Indices using the
prescription given by Gomes da Silva et al. (2021) and calibrate the results
to the Mount Wilson scale by cross matching with the mean S-indices derived by
Duncan et al. (1991). The S-index errors are calculated via a Monte Carlo
approach where, in each trial, the flux in each bin of the measured spectrum
is randomly displaced within a Gaussian distribution with width of the flux
error. The S-index is then evaluated for each trial, and the error is taken to
be the standard deviation of the resulting set. This approach yields S-indices
for $\sim 93.5\%$ of the _HARPS_ spectra present in the RVBank archives.

Attempts to use these Monte Carlo S-index errors for the HARPS data alongside
the photon-noise limited errors derived from the HIRES, PFS, and APF data
results in an uneven weighting in favor of the iodine-based instruments. While
we report all of these errors in the data tables that accompany this
publication for reference, in practice we adopt a third, alternative method
for determining S-index errors so that all four instruments’ data sets are
treated in the same way. We begin by selecting five stars (HD 69830, HD
196761, HD 114613, HD 4628, and HD 39091) all of which have at least two dozen
observations from at least two of the instruments. We assign all of the
S-index data for each star the same error bar of $\sigma_{S}$ = 0.01 and carry
out an initial uninformed fit with RVSearch. We then combine all of the
residual values from each instrument across all stars, measure the standard
deviation, and assign that as the global error for that instrument. Those
values are: HARPS-Pre : 0.010; HARPS-Post : 0.006; HIRES-Pre : 0.010; HIRES-
Post : 0.014; PFS-Pre : 0.005; PFS-Post : 0.009, APF : 0.007. As we expect the
S-index measurement to be systematics dominated (e.g. from the deblazing and
continuum normalization) rather than photon-noise dominated, this empirical
approach to measuring the uncertainty provides a more homogeneous error
estimate.

When summarizing the properties of our target stars below, we reference log
$R^{\prime}_{HK}$ values for stars where it has been reported in the
literature. This metric is also derived using the Ca II H&K absorption lines,
but log $R^{\prime}_{HK}$ removes the basal (rotation independent)
photospheric flux (Noyes et al., 1984; Schrijver, 1987; Mittag et al., 2013).
This photospheric flux, which can contaminate the S-index filters, introduces
a dependency on stellar effective temperature. By removing it, the log
$R^{\prime}_{HK}$ metric produces a measure of activity that can be compared
across spectral types.

###  3.3 H$\alpha$ Equivalent Width Measurements

The _UCLES_ spectrograph cannot simultaneously cover the Iodine region
necessary for precise wavelength calibration of the stellar spectra and the Ca
II H & K region necessary for extracting the S-index measurements. To provide
a stellar activity check on the RVs derived from the AAT dataset, we instead
make use of the H$\alpha$ absorption line, using measurements of the line’s
equivalent width (EW) to detect variations related to the long-term stellar
magnetic activity cycle. This EWHα analysis follows the methodology of
Wittenmyer et al. (2017) which is similar to that presented by Robertson et
al. (2014), except for the addition of an automated algorithm for continuum
normalization and telluric contamination identification near the H$\alpha$
line.

A visual comparison of the resulting EWHα time series reveals the presence of
very similar structured variations among each of the resulting data sets
(Figure 3). Given the shared trends between the stars, the source is likely
either instrumental or environmental in nature. One potential cause is
variations in the water content of the atmosphere. As our EWHα calculation
algorithm does not actively correct for the telluric lines, it is reasonable
to assume the EWHα measurements are subject to effects from atmospheric water
content. However, when compared to the historic precipitable water vapor
measurements from Siding Spring (e.g. those in Haslebacher et al. (2022)), no
strong correlation is evident.

While the exact cause of the variations is not clear, we note that the stacked
periodograms of a dozen stars (each with dozens of _UCLES_ H$\alpha$ data
points but no significant detections) all linearly interpolated onto the same
period grid shows prominent peaks at $\sim$1 year, $\sim$3000 day
(approximately half the _UCLES_ observation time span), and $\sim$6000 day
(approximately equal to the _UCLES_ observation time span) periods. We
therefore advise caution when interpreting the results of the H$\alpha$
RVSearchanalysis, especially in the case of long period signals. Shorter
period detections, those in the 10 - 100 day range where we generally look for
evidence of stellar rotation for these F - K dwarfs stars, seem to be
unaffected by these long period variations.

Figure 3: Top: EWHα time series for three stars observed with the _UCLES_
spectrograph, offset vertically from one another for ease of viewing. Similar
long term behavior is present in each of these three data sets, suggesting
that the cause is not stellar but rather instrumental or environmental.
Bottom: Stacked periodograms from 6 stars with at least 100 _UCLES_ H$\alpha$
measurements spread over the majority of the instrument’s $\sim$6000 day
observational baseline, where no significant signals were detected by
RVSearch. The long term structure seen in the top panel emerges as two humps
in this composite periodogram, one at _UCLES_ ’ observing baseline (6000 days)
and another at half that (3000 days). The impact of the monthly lunar cycle is
also evident via a narrow peak at 29.5 days. We therefore treat H$\alpha$
periods detected around any of these three periods with some degree of
caution.

###  3.4 Speckle Imaging

For a handful of the stars studied in this work, high resolution speckle
imaging observations to search for and/or rule out nearby stellar companions
were obtained. The speckle imaging observations were carried out using the
‘Alopeke and Zorro instruments at Gemini-North and Gemini-South, respectively
(Scott et al., 2021). These instruments observe simultaneously in two bands,
(832$\pm$40 nm and 562$\pm$54 nm) obtaining diffraction limited images with
inner working angles of 0″.026 and 0″.017, respectively. All targets were
observed using a sequence of short 60 ms exposures. These images were combined
using Fourier analysis techniques, examined for stellar companions, and used
to produce reconstructed speckle images (see Howell et al. (2011) and Horch et
al. (2021)). We summarize the observations and the resulting sensitivity to
companions in Table 8. and Figure Set 8 (available in the online journal).

##  4 Analysis

###  4.1 Overview of RVSearch

RVSearch (Rosenthal et al., 2021) is a recently released Python package based
on RadVel (Fulton et al., 2018), built specifically to perform uninformed
searches for Keplerian signals in RV data and to perform injection and
recovery analysis of RV time series data.

RVSearch ’s uninformed search function is used to identify candidate signals
in our compiled radial velocity, S-index, and H$\alpha$ data sets. For each
data set we bin the input velocities / activity measurements to nightly data
points to decrease the computational requirements and set a minimum search
period of 2 days and a maximum search period of three times the total
observational baseline days. In addition to any Keplerian signals, RVSearch
also fits for a constant offset between each instrument’s data set and for the
‘jitter’ of each instrument. This jitter term is used to address the unmodeled
instrumental effects or stellar variability that induce additional scatter in
the RV time series and encompasses uncorrelated signals that occur on
timescales shorter than the observational baseline.

RVSearch implements an iterative fitting approach when searching for periodic
signals in a time series. It first tests for the presence of a linear or
quadratic slope in the data, before beginning the Keplerian fitting process by
generating a single planet with undefined orbital parameters to become the
initial likelihood model. With the initial model in hand, RVSearch defines a
set of periods to test141414The periods are spaced such that the frequency
offset between adjacent grid points is 1/2$\pi\tau$, where $\tau$ is the
observational baseline of the full RV time series. and computes a $\Delta$BIC
goodness-of-fit periodogram by fitting a sinusoid to the data at each fixed
period. The Bayesian Information Criterion, or BIC, is used for model
selection when considering a finite set of models and is calculated as:

$\rm{BIC}=-2\ \rm{ln}\ \mathcal{L}_{\rm{max}}\ +\it{n}\ \rm{ln}\ \it{N}$ (3)

where $\mathcal{L}_{\rm{max}}$ is the maximum likelihood, _n_ is the number of
model free parameters, and _N_ is the number of data points (see, e.g., Kass &
Raftery, 1995, for details). Models with lower BIC values are generally
preferred. The $\Delta$BIC value at each period is the difference between the
best-fit, $n$+1-planet model with the given fixed period, and the $n$-planet
fit to the data.

Once the $\Delta$BIC periodogram has been calculated, a linear fit is applied
the data, and a histogram of periodogram power values is plotted on a log
scale. A detection threshold is then constructed such that only 0.1% of
periodogram peaks are expected to be high enough powered to exceed it. This
threshold is the empirical False Alarm Probability (FAP) of 0.1% (Rosenthal et
al., 2021). Any signal above a 0.1% empirical False Alarm Probability (FAP) is
considered significant. For our S-index search, we enforce an additional
requirement that the $\Delta$BIC value be at least 10 for a signal to be added
to the system’s model, even if that corresponds to a FAP value $<$1%. This
prevents the inclusion of a nonphysical number of short period signals in
sparse data sets, while still being a generous inclusion criteria as the field
standard for considering a signal worthy of consideration for publication is
more often $\Delta$BIC $>$ 25.

If a significant detection is made, RVSearch refines the fit of the signal’s
Keplerian orbit by performing a maximum a posteriori (MAP) fit with all model
parameters free, including eccentricity, and records the BIC of that best-fit
model. The search algorithm then adds an additional planet to the model and
repeats the fitting and evaluation process. In the n+1 planet fit, the signals
are treated simultaneously, so that the change in the BIC can again be
evaluated to compare the $n$-planet fit to the $n$+1-planet fit. We note here
that when analyzing our S-index and H$\alpha$ data sets, the ‘planet’
detections instead refer to activity-driven periodicities in the data sets. If
the new planet is supported by the data, the search continues. The uninformed
search continues to iterate on the time series until no additional significant
signals are present in the periodogram.

At this point, RVSearch returns the max-likelihood estimates of the orbital
model parameters the the dataset and the model posteriors are sampled via an
affine-invariant sampling that is implemented in RadVel using the emcee
package (Foreman-Mackey et al., 2013). The resulting parameter estimates and
uncertainties, reported as the median and $\pm$1$\sigma$ intervals are visible
on the summary figures produced by RVSearch and in our summary tables.

One complication encountered in the fitting process, across both the RV and
S-index applications, is the treatment of signals with periods on order or
greater than the total observational baseline. While the $\Delta$BIC
periodogram approach used in the first phase of RVSearch ’s process can only
fully resolve periods shorter than the observational baseline, the posterior
sampling is not subject to similar constraints. Thus in cases where there is a
prominent peak in the periodogram that has a peak close to or beyond the
observational baseline, the MCMC will sometimes suggest that the true period
is 2x the periodogram peak, or in some cases many times larger. In these
instances the traditional MCMC method fails to return a well-sampled model
posterior and the resulting period uncertainty is as large as, if not many
times larger than, the period itself. We note these types of detections as
long period signals (‘LPS’) in our summary tables and report just the initial
$\Delta$BIC periodogram peak instead of the final MCMC fit and its
corresponding uncertainties, as they are non-physical. For these signals, note
that additional data is required to fully reveal and constrain the underlying
signal.

###  4.2 Identification of Candidate Signals in the Radial Velocity data

An example RVSearch fit to the radial velocity data for HD 115617 is shown in
Figure 4. The HD 115617 planetary system was first published in Vogt et al.
(2010) using data from the _HIRES_ and _UCLES_ spectrographs. Three planets
were discovered with periods and RV semi-amplitudes of 4.215$\pm$0.0006 d and
$2.12\pm 0.23$ $\rm m\,s^{-1}$ $38.021\pm 0.034$ d and $3.62\pm 0.23$ $\rm
m\,s^{-1}$, and $123.01\pm 0.55$ d and $3.25\pm 0.39$ $\rm m\,s^{-1}$ for
planets b, c, and d, respectively. Revisiting the system with the available
archival data, we supplement the published data with an additional 275 _HIRES_
points, 159 _UCLES_ points, 1248 _HARPS_ points, and 11 _PFS_ points taken
between 2004 and 2020.

Figure 4: RVSearch results for HD 115617. Panel (a) shows the initial radial
velocity time series with the best-fit model plotted in blue and panel (b)
shows the RV residuals. Panels (c), (e), (g) show phased RV curves for the
three known planets in the system, and report the best-fit parameters for each
orbit. Panels (d), (f), and (h) show the periodograms associated with each
planet detection. The yellow horizontal dotted line marks the minimum
$\Delta$BIC for a 1% FAP, while the vertical dotted lines show monthly and
yearly aliases. Panels (i) and (j) show the periodogram and best fit curve to
a fourth, much longer and highly eccentric signal that is likely driven by
stellar variability. Panel (k) shows the RV significance of each signal
relative to the number of observations considered and is calculated using the
best-fit orbits shown in the left side panels above it, and panel (l) shows
the residual periodogram, indicating that no further planets are found in the
data set. The complete set of Radial Velocity summary plots (46 figures) can
be found in the online journal.

Fig. Set4. Radial Velocity Analysis Summary Plots

Figure 5: RVSearch results for the relative S-index measurements of HD 115617,
following the same plot image structure as in Figure 4. Panel (a) shows the
S-index time series with the best-fit model plotted behind them while panel
(b) shows the S-index residuals. Panel (c) would present the phase folded
curves for any signals identified by RVSearch, but as seen in panel (d) no
signals in the periodogram rise above the $\Delta$BIC $>$ 10 requirement
imposed on the S-index search (yellow horizontal dotted line). The red and
green vertical dotted lines show the one month and one year aliases of the
tallest peak in the periodogram. The complete set of S-Index summary plots (46
figures) can be found in the online journal.

Fig. Set5. S-Index Activity Summary Plots

Incorporating this additional RV data produces a fit consistent with the Vogt
et al. (2010) results. All three previously published planets are again
detected at statistically significant levels and at very similar period and
semi-amplitude values. The uncertainties on those values, however, are notably
improved in the updated fit; the RV semi-amplitude uncertainty decreases by a
factor of two, thereby doubling the detection significance, and the period
uncertainty decreases by factors of two to four across the three planets.

RVSearch also identifies a fourth, much longer period signal that rises above
the detection threshold, with $P=20565\pm 21000$ days (Figure 3 panel i). The
uncertainty on the best-fit orbital period is of order the period itself and
it overlaps broadly with a long period signal in the star’s activity data
(see: Section 4.3). Additionally, the strength of this fourth RV signal varies
quite noticeably as the number of data points increases. This suggests that
only specific clumps of data are providing additional power in the
periodogram, as compared to the roughly monotonic increase that is expected
for a Keplerian signal (similar to the Mortier & Collier Cameron (2017)
stacked periodogram technique). Finally, we note that the period of the peak
which is actually being fit by this signal is of approximately the same length
as the observation baseline for this target. As discussed in Section 4.1, this
results in unphysical MCMC fitting to the signal. These concerns, combined
with the fact that the best-fit model’s high eccentricity would produce a
semi-minor axis of $\sim$0.5 AU that would disturb the three shorter period
planets that have been robustly vetted, leads us to conclude the final signal
detected by RVSearch is not planetary in nature. This signal is classified as
LPS in Table 4.

For all previously discovered planetary systems, HD 115617 included, we report
our best-fit results as updates to the published orbital parameters in Section
5.

Table 4: Keplerian RV Signals Identified by RVSearch (Updated for
Resubmission)

ID | Period [days] | K [$\rm m\,s^{-1}$] | Ecc. | Msini [M⊕] | FAP | Interp
---|---|---|---|---|---|---
HD1581 I | 635.0$\pm$4.4 | 0.89$\pm$0.14 | 0.55$\pm$0.13 | 10.08${}^{+1.22}_{-1.17}$ | 7.24e-09 | SRC
HD1581 II | 15.653$\pm$0.005 | 0.662$\pm$0.096 | 0.106$\pm$0.097 | 2.56${}^{+0.37}_{-0.38}$ | 1.85e-05 | ACT-R
HD1581 III | 29.4661$\pm$0.0041 | 1.6$\pm$1.1 | 0.89$\pm$0.12 | 3.53${}^{+1.15}_{-0.85}$ | 8.26e-04 | ACT
HD2151 I | 5365$\pm$1400 | 3.21$\pm$0.58 | 0.54$\pm$0.15 | 81.41${}^{+12.95}_{-13.22}$ | 8.90e-07 | ACT
HD13445 I | 88080$\pm$46000 | 3117$\pm$750 | 0.68$\pm$0.12 | 201858.32${}^{+79293.94}_{-71306.73}$ | 2.28e-16 | Binary
HD13445 b | 15.764862$\pm$4.3e-05 | 377.58$\pm$0.77 | 0.0485$\pm$0.0018 | 1271.19${}^{+25.51}_{-25.72}$ | 3.56e-83 | KP
HD16160 I | 22999$\pm$1200 | 702.5$\pm$2.9 | 0.6075$\pm$0.0092 | 20304.22${}^{+434.82}_{-436.28}$ | 1.23e-26 | Binary
HD20766 I | 5643.5 | – | – | – | – | LPS
HD20794 b | 18.305$\pm$0.0052 | 0.807$\pm$0.089 | 0.17$\pm$0.11 | 2.83$\pm$0.31 | 2.20e-11 | KP
HD20794 d | 89.766$\pm$0.085 | 0.86$\pm$0.12 | 0.27$\pm$0.11 | 5.02${}^{+0.66}_{-0.64}$ | 7.38e-11 | KP
HD20807 I | 3180$\pm$130 | 2.9$\pm$0.4 | 0.23$\pm$0.11 | 62.48${}^{+8.81}_{-8.74}$ | 2.73e-07 | SRC
HD22049 b | 2832$\pm$120 | 11.1$\pm$1.2 | 0.09$\pm$0.08 | 211.16${}^{+23.57}_{-24.34}$ | 8.55e-11 | KP
HD23249 I | 596.6$\pm$2.6 | 3.0$\pm$1.1 | 0.65$\pm$0.14 | 33.33${}^{+7.89}_{-5.6}$ | 8.18e-08 | SRC
HD26965 I | 42.303$\pm$0.025 | 1.4$\pm$0.22 | 0.37$\pm$0.17 | 5.94$\pm$0.79 | 1.48e-08 | ACT*
HD26965 II | 37.33$\pm$0.02 | 1.17$\pm$0.19 | 0.14$\pm$0.12 | 5.14${}^{+0.84}_{-0.86}$ | 7.45e-05 | Alias
HD26965 III | 367.9$\pm$3.1 | 1.63$\pm$0.88 | 0.46$\pm$0.27 | 13.9${}^{+5.13}_{-2.95}$ | 1.37e-05 | FP
HD32147 I | 2866$\pm$140 | 1.8$\pm$0.21 | 0.34$\pm$0.13 | 32.02${}^{+3.54}_{-3.49}$ | 3.94e-12 | SRC
HD38858 I | 2893$\pm$150 | 2.8$\pm$0.3 | 0.19$\pm$0.12 | 58.15${}^{+6.19}_{-6.01}$ | 1.41e-13 | ACT-M
HD39091 b | 2089.05$\pm$0.46 | 196.5$\pm$0.6 | 0.6428$\pm$0.0017 | 3225.56${}^{+58.95}_{-59.18}$ | 1.10e-20 | KP
HD39091 d | 125.58$\pm$0.27 | 2.16$\pm$0.42 | 0.16$\pm$0.15 | 17.56${}^{+3.49}_{-3.31}$ | 4.26e-04 | KP
HD69830 b | 8.66897$\pm$0.00028 | 3.4$\pm$0.1 | 0.128$\pm$0.028 | 10.1${}^{+0.38}_{-0.37}$ | 2.15e-62 | KP
HD69830 c | 31.6158$\pm$0.0051 | 2.6$\pm$0.1 | 0.03$\pm$0.027 | 12.09${}^{+0.55}_{-0.54}$ | 1.47e-84 | KP
HD69830 d | 201.4$\pm$0.4 | 1.5$\pm$0.1 | 0.08$\pm$0.071 | 12.26${}^{+0.89}_{-0.88}$ | 1.89e-36 | KP
HD75732 b | 14.65157$\pm$0.00015 | 70.39$\pm$0.37 | 0.0069$\pm$0.0047 | 254.81${}^{+4.79}_{-4.81}$ | 4.13e-97 | KP
HD75732 d | 14951$\pm$5100 | 54$\pm$5 | 0.515$\pm$0.086 | 1686.0${}^{+229.11}_{-264.51}$ | 9.03e-20 | KP
HD75732 c | 44.39$\pm$0.01 | 9.95$\pm$0.37 | 0.22$\pm$0.041 | 50.78${}^{+2.05}_{-2.0}$ | 2.37e-34 | KP
HD75732 e | 0.736546$\pm$5e-06 | 6.26$\pm$0.34 | 0.039$\pm$0.035 | 8.35${}^{+0.48}_{-0.47}$ | 6.05e-28 | KP
HD75732 f | 260.88$\pm$0.36 | 5.68$\pm$0.48 | 0.585$\pm$0.057 | 43.4${}^{+3.61}_{-3.5}$ | 3..51e-14 | KP
HD85512 I | 3891 | – | – | – | 1.90e-16 | LPS
HD85512 II | 51.195$\pm$0.073 | 0.438$\pm$0.079 | 0.3$\pm$0.19 | 1.86${}^{+0.31}_{-0.3}$ | 6.98e-06 | ACT-R*
HD102365 b | 121.3$\pm$0.25 | 1.38$\pm$0.23 | 0.28$\pm$0.15 | 9.34${}^{+1.52}_{-1.5}$ | 1.58e-04 | KP
HD114613 I | 6622$\pm$270 | 7.29$\pm$0.45 | 0.291$\pm$0.061 | 239.94${}^{+13.54}_{-13.5}$ | 2.87e-34 | ACT-M*
HD114613 II | 73.141$\pm$0.056 | 2.54$\pm$0.45 | 0.51$\pm$0.14 | 16.72${}^{+2.38}_{-2.42}$ | 4.31e-04 | SRC
HD114613 III | 1954$\pm$39 | 2.98$\pm$0.52 | 0.6$\pm$0.11 | 54.01${}^{+7.59}_{-7.5}$ | 2.09e-04 | SRC
HD115617 b | 4.21498$\pm$0.00014 | 2.47$\pm$0.11 | 0.033$\pm$0.029 | 5.98${}^{+0.3}_{-0.29}$ | 5.01e-61 | KP
HD115617 c | 38.079$\pm$0.008 | 3.56$\pm$0.12 | 0.026$\pm$0.023 | 17.94${}^{+0.73}_{-0.7}$ | 2.93e-46 | KP
HD115617 d | 123.2$\pm$0.2 | 1.47$\pm$0.17 | 0.15$\pm$0.11 | 10.82${}^{+1.23}_{-1.03}$ | 5.63e-22 | KP
HD115617 I | 5910.9 | – | – | – | 1.22e-10 | LPS
HD136352 b | 11.5767$\pm$0.0015 | 1.65$\pm$0.11 | 0.05$\pm$0.045 | 5.5$\pm$0.38 | 3.67e-38 | KP
HD136352 c | 27.5845$\pm$0.0064 | 2.49$\pm$0.12 | 0.041$\pm$0.036 | 11.12$\pm$0.57 | 3.04e-24 | KP
HD136352 d | 107.5$\pm$0.14 | 1.44$\pm$0.12 | 0.072$\pm$0.061 | 10.08${}^{+0.87}_{-0.85}$ | 2.06e-23 | KP
HD136352 I | 121.66$\pm$0.26 | 0.68$\pm$0.13 | 0.22$\pm$0.19 | 4.69${}^{+0.87}_{-0.86}$ | 9.76e-04 | ACT
HD140901 I | 5084$\pm$1200 | 11.6$\pm$2.4 | 0.44$\pm$0.25 | 269.81${}^{+43.83}_{-42.02}$ | 7.32e-04 | SRC
HD146233 I | 2374$\pm$47 | 5.47$\pm$0.33 | 0.21$\pm$0.07 | 111.72${}^{+6.67}_{-6.59}$ | 1.31e-25 | ACT-M*
HD146233 II | 6256$\pm$370 | 4.96$\pm$0.57 | 0.59$\pm$0.06 | 114.86${}^{+12.0}_{-11.43}$ | 7.39e-14 | ACT-M
HD146233 III | 19.8777$\pm$0.0062 | 1.73$\pm$0.26 | 0.38$\pm$0.16 | 6.77$\pm$0.86 | 7.23e-09 | Candidate
HD160346 I | 83.7286$\pm$0.0005 | 5690.3$\pm$2.3 | 0.2048$\pm$0.0003 | 35280.0${}^{+706.83}_{-716.46}$ | 1.42e-15 | Binary
HD160691 b | 644.93$\pm$0.28 | 35.7$\pm$0.2 | 0.0499$\pm$0.0082 | 528.58${}^{+11.05}_{-11.13}$ | 2.16e-46 | KP
HD160691 c | 9.6394$\pm$0.0008 | 2.8$\pm$0.2 | 0.132$\pm$0.069 | 10.22$\pm$0.73 | 5.38e-98 | KP
HD160691 d | 308.4$\pm$0.23 | 12.7$\pm$0.3 | 0.074$\pm$0.016 | 147.23${}^{+4.63}_{-4.56}$ | 8.24e-131 | KP
HD160691 e | 4035$\pm$21 | 22.25$\pm$0.24 | 0.026$\pm$0.013 | 607.79${}^{+14.0}_{-13.99}$ | 2.84e-32 | KP
HD190248 I | 360.8$\pm$1.9 | 1.21$\pm$0.43 | 0.29$\pm$0.15 | 12.96${}^{+5.08}_{-3.76}$ | 5.14e-04 | FP
HD192310 b | 74.278$\pm$0.035 | 2.484$\pm$0.098 | 0.032$\pm$0.027 | 14.28${}^{+0.64}_{-0.63}$ | 8.11e-50 | KP
HD192310 c | 549.1$\pm$4.5 | 1.3$\pm$0.1 | 0.078$\pm$0.073 | 14.96${}^{+1.21}_{-1.18}$ | 3.64e-27 | KP
HD192310 I | 3836$\pm$240 | 1.48$\pm$0.11 | 0.34$\pm$0.15 | 29.3${}^{+3.33}_{-3.07}$ | 1.64e-49 | ACT-M
HD192310 II | 43.614$\pm$0.023 | 0.93$\pm$0.13 | 0.5$\pm$0.1 | 3.83$\pm$0.44 | 2.41e-13 | ACT-R
HD192310 III | 39.509$\pm$0.059 | 1.0$\pm$0.1 | 0.22$\pm$0.11 | 4.48$\pm$0.46 | 1.43e-09 | ACT-R
HD192310 IV | 24.559$\pm$0.016 | 0.6$\pm$0.1 | 0.16$\pm$0.12 | 2.46${}^{+0.39}_{-0.4}$ | 7.74e-06 | Candidate
HD207129 I | 1964$\pm$49 | 4.02$\pm$0.61 | 0.44$\pm$0.16 | 72.95${}^{+8.37}_{-8.07}$ | 3.88e-11 | ACT-M
HD209100 I | 13138.7 | – | – | – | 1.38e-37 | LPS

††footnotetext: This table contains, for each target, any significant signals
identified by RVSearch. We report the period, semi-amplitude, eccentricity,
minimum mass, False Alarm Probability (FAP), and a classification of each
signal (KP: Known Planet, Candidate: promising planet candidate signal,
Binary: Binary Star, SRC: Source Requiring Confirmation, ACT-R: Stellar
Rotation, ACT-M: Magnetic Activity Cycle, LPS: Long Period Signal that does
not return a well sampled posterior and therefore lacks a full orbital
solution prompting us to report only the initial $\Delta$BIC periodogram peak,
FP: False positive from aliasing or window function of another detection). *:
This signal was reported as a planet in other previous works but we believe it
to be stellar in nature, see corresponding discussion sections for details.

Table 5: Linear/Quadratic RV Trends

HD | Alias | RV Trend
---|---|---
100623 | 20 Crt | 0.00514923 $\rm m\,s^{-1}$ day-1
131977 | GJ 570A | -0.0116872 $\rm m\,s^{-1}$ day-1
188512 |  $\beta$ Aql | 0.00262165 $\rm m\,s^{-1}$ day-1
190248 |  $\delta$ Pav | -0.00055 $\rm m\,s^{-1}$ day-1

††footnotetext: Stars from our sample for which the preferred RVSearch model
included a linear and/or quadratic trend. All appear to be due to known
stellar companions except for $\delta$ Pav.

###  4.3 Identification of Candidate Activity Signals in the S-index Data

We also use RVSearch to carry out an uninformed search on each star’s combined
S-index measurements, similar to the RV fitting described above. By providing
RVSearch with data sets composed of the observation time stamp, S-index, and
the empirical instrument-by-instrument S-index errors described in Section 3.2
from each observation, we are able to determine whether the S-index data
contain significant periodic signals. Further, if the empirical errors are
underestimated, RVSearch ’s use of a jitter term will adjust them to more
accurately capture the scatter on a star-by-star basis. A list of all of the
detected S-index signals is provided in Table 6.

We then carry out a side-by-side comparison of the signals found in the
activity search to the signals found in the radial velocity search. In
instances of overlapping periods between the two search results, we assert
that the signal in the radial velocities is likely caused by stellar activity,
rather than by the gravitational effects of an orbiting exoplanet. New RV
signals that show evidence of this period overlap are reported in Table 4 as
‘Activity’. Instances where there is no overlap between the significant
periods detected in the RV and S-index data sets are treated on a more
individual basis. If the signal detected in the radial velocity periodogram
peak is well defined, the strength of the RV signal increases roughly
monotonically with the number of observations, and we do not find a correlated
activity signal, then we mark the signal as a ‘Candidate’ in Table 4.

For less obvious cases, where the RV signal is one of a set of numerous peaks
clustered in a narrow period range but we find no corresponding signal in the
activity data, we then consider the star’s spectral type and known activity
history to decide whether the signal is likely to be due to activity. These
cases are discussed in detail in each star’s subsection. We adopt the
classification Source Requiring Confirmation (’SRC’) for signals that do not
yet have enough evidence to be classified as either Candidate or Activity.
Signals marked as SRC in Table 4 require further followup analysis to
determine their nature.

Results for HD 115617’s RVSearch analysis of the S-index data are shown in
Figure 5. No significant detections are made, although we note that a strong
signal is present at $P=3995.5$ days in the periodogram. The strength of this
signal is limited by the time span of observations for this target; we expect
that given several more years’ worth of data, we would be able to state
conclusively whether this signal is physical or not.

When compared with the radial velocity analysis in Figure 4, we see no
overlapping periods between the three previously published planet signals the
S-index signal of growing strength in the periodogram. We thus affirm that the
planets HD 115617 b, c, and d are not false signals caused by activity, but
rather true exoplanets.

We include summary figures like Figure 5 from each star’s S-index data in a
figure set in the online journal. As referenced in 3.3, the _UCLES_
spectrograph does not cover a wide enough wavelength range for the Ca II H & K
lines to be observed simultaneously with the iodine region. For targets whose
RV signals are largely driven by _UCLES_ data, this causes the corresponding
S-index activity analysis to be less definitive as a planet vetting step.
Instead, we use EWHα measurements as an activity indicator for those stars.

Table 6: S-index Signals Identified by RVSearch

ID | Period [days] | S-index Amp. | ID | Period [days] | S-index Amp.
---|---|---|---|---|---
HD4628 I | 3699$\pm$310 | 0.0161$\pm$0.0016 | HD85512 VIII | 51.74$\pm$0.06 | 0.0152$\pm$0.0023
HD14412 I | 2312$\pm$73 | 0.013$\pm$0.0034 | HD100623 I | 3741$\pm$93 | 0.0228$\pm$0.0025
HD14412 II | 5686$\pm$1600 | 0.0191$\pm$0.0079 | HD114613 I * | 6722.80 | –
HD16160 I | 4232$\pm$310 | 0.0417$\pm$0.0073 | HD125072 I | 2989$\pm$100 | 0.098$\pm$0.011
HD16160 II | 3204$\pm$110 | 0.0253$\pm$0.0061 | HD125072 II | 40.49$\pm$0.04 | 0.0336$\pm$0.0072
HD20766 I * | 1553.62 | – | HD131977 I | 22.77$\pm$0.0 | 0.29$\pm$0.17
HD22049 I | 1086.7$\pm$7.1 | 0.0496$\pm$0.0048 | HD131977 II | 3.88$\pm$0.0 | 0.192$\pm$0.065
HD26965 I | 3177$\pm$84 | 0.0206$\pm$0.0018 | HD131977 III | 2.09$\pm$0.0 | 0.067$\pm$0.014
HD30495 I | 71.46$\pm$0.11 | 0.0303$\pm$0.0046 | HD146233 I | 2812$\pm$290 | 0.0094$\pm$0.0032
HD32147 I | 3774$\pm$250 | 0.063$\pm$0.016 | HD146233 II | 5272$\pm$1500 | 0.0116$\pm$0.0043
HD32147 II | 3204$\pm$310 | 0.043$\pm$0.016 | HD149661 I | 1649$\pm$55 | 0.0423$\pm$0.0065
HD32147 III | 381.7$\pm$2.4 | 0.0093$\pm$0.0019 | HD149661 II | 3874$\pm$1200 | 0.068$\pm$0.095
HD32147 IV | 343.2$\pm$2.7 | 0.0088$\pm$0.0018 | HD156026 I | 378.9$\pm$2.2 | 0.05$\pm$0.01
HD32147 V | 95.6$\pm$0.24 | 0.005$\pm$0.0016 | HD160346 I | 2975$\pm$600 | 0.0883$\pm$0.0094
HD50281 I | 2264$\pm$11 | 0.0748$\pm$0.0042 | HD160346 II | 392.6$\pm$3.2 | 0.05$\pm$0.013
HD50281 II | 2102$\pm$12 | 0.065$\pm$0.005 | HD160346 III | 7.96$\pm$0.01 | 0.0313$\pm$0.0093
HD50281 III | 139.42$\pm$0.05 | 0.0345$\pm$0.0039 | HD160346 IV | 2.54$\pm$0.0 | 0.0177$\pm$0.0081
HD50281 IV | 12.48$\pm$0.0 | 0.0266$\pm$0.0039 | HD190248 I * | 6810.18 | –
HD50281 V | 16.5$\pm$0.0 | 0.022$\pm$0.0036 | HD192310 I | 3817$\pm$60 | 0.0409$\pm$0.0013
HD50281 VI | 5.39$\pm$0.0 | 0.083$\pm$0.084 | HD192310 II | 345.34$\pm$0.48 | 0.0093$\pm$0.0058
HD50281 VII | 2.7$\pm$0.0 | 0.0169$\pm$0.0047 | HD192310 III | 44.01$\pm$0.11 | 0.0044$\pm$0.0011
HD69830 I | 3989$\pm$190 | 0.0146$\pm$0.0017 | HD192310 IV | 432.6$\pm$3.4 | 0.015$\pm$0.0031
HD69830 II | 731$\pm$31 | 0.0038$\pm$0.0018 | HD192310 V | 40.8$\pm$0.1 | 0.00383$\pm$0.00088
HD69830 III | 2530$\pm$180 | 0.008$\pm$0.002 | HD192310 VI | 34.6$\pm$0.03 | 0.00521$\pm$0.00082
HD72673 I | 3217$\pm$200 | 0.0097$\pm$0.0016 | HD192310 VII | 133.38$\pm$0.43 | 0.0069$\pm$0.0015
HD75732 I | 3801$\pm$130 | 0.0263$\pm$0.0015 | HD192310 VIII | 33.73$\pm$0.05 | 0.00563$\pm$0.00097
HD85512 I | 4245$\pm$52 | 0.2106$\pm$0.0029 | HD207129 I * | 1897.99 | –
HD85512 II | 1294$\pm$14 | 0.0443$\pm$0.0035 | HD209100 I | 2063$\pm$160 | 0.0588$\pm$0.0046
HD85512 III | 478.1$\pm$2.2 | 0.0324$\pm$0.0027 | HD209100 II | 32.87$\pm$0.07 | 0.045$\pm$0.036
HD85512 IV | 322.05$\pm$0.85 | 0.0351$\pm$0.0032 | HD216803 I | 3.89$\pm$0.0 | 0.066$\pm$0.008
HD85512 V | 45.52$\pm$0.04 | 0.0187$\pm$0.0021 | HD216803 II | 4.08$\pm$0.0 | 0.051$\pm$0.016
HD85512 VI | 44.18$\pm$0.03 | 0.0188$\pm$0.0016 | HD216803 III | 2.8$\pm$0.3 | 0.019$\pm$0.013
HD85512 VII | 104.3$\pm$0.15 | 0.022$\pm$0.0034 |  |  |

††footnotetext: This table contains all significant S-index signals identified
by RVSearch. We report the period and S-Index semi-amplitude (in units of the
Mt. Wilson S-index) of each signal. For signal interpretations, see each
star’s individual discussion section. Signals with a * designation failed to
return well constrained MCMC results, and so we instead report the MAP fits
for their orbital periods.

###  4.4 Identification of Candidate Activity Signals in _UCLES_ EWHα Data

Stellar variability in the _UCLES_ time series, which does not provide
coverage of the Ca II H & K lines, was instead assessed using measurements of
the equivalent width of the H$\alpha$ absorption line (EWHα). Although the
H$\alpha$ line is usually more informative for cooler, M dwarf stars (see,
e.g., Robertson et al., 2013) it is still sensitive to some activity
variations in hotter, Sun-like stars. We subjected the EWHα time series to the
same uninformed search process with RVSearch described for the S-index data
above, again beginning with the removal of any 5+$\sigma$ outliers within each
star’s data set. We run the cleaned time series through RVSearch and record
any significant periodicities so that they can be compared with the periods
(if any) detected in that star’s RV data. We find that the long term structure
present in EWHα is not sufficiently periodic to show up in the RVSearch
$\Delta$BIC periodograms, but caution that it may still obscure some lower
amplitude activity signals within the data. A list of all of the detected EWHα
signals is provided in Table 7.

Figure 6: RVSearch results for the relative EWHα measurements of HD 115617.
Panel (a) shows the EWHα time series with the best-fit model plotted behind
them while panel (b) shows the EWHα residuals. Panels (c), (e), and (g) show
phase folded curves for the signals identified by RVSearch, and panels (d),
(f), and (h) show the periodograms associated with each signal, with the
yellow horizontal dotted line marking the minimum $\Delta$BIC for a 1% FAP
significance and the red and green vertical dotted lines showing the one month
and one year aliases of the tallest peak. Panel (i) shows the effective
strength of each signal as a function of the number of observations, and panel
(j) shows the residuals periodogram, indicating that no further signals are
found in the data set. The complete set of ${H\alpha}$ activity summary plots
(31 figures) can be found in the online journal.

Fig. Set6. H$\alpha$ Activity Analysis Summary Plots

Figure 6 shows an example summary figure from H$\alpha$ analysis of HD 115617.
Our analysis returns three detections, only one of which we believe to be of
astrophysical causes. The first signal, with $P=346.3\pm 1.9$ d, is extremely
close to one year. Just as with _HARPS_ data, we expect to see yearly
systematics within the H$\alpha$ data caused by the observing cadence. This
signal is therefore attributed to systematics. H$\alpha$ signal II is close to
the rotation period predicted for this star. Because we have a longer
observation baseline and more precise measurements than were used for previous
rotation period estimates in the literature, we report H$\alpha$ signal II as
an update to the stellar rotation period. H$\alpha$ signal III is most likely
too long-period to be caused by differential rotation, though we discuss the
possibility in detail in §5.14. It also does not correspond to any peaks in RV
or S-index data. We leave it to future, more in-depth studies of stellar
activity to characterize the cause of this detection. The resulting summary
figures for all 31 stars in this study observed by _UCLES_ are available in a
figure set in the online journal.

Table 7: H $\alpha$ Signals Identified by RVSearch

ID | Period [days] | EWHα Amp. | ID | Period [days] | EWHα Amp.
---|---|---|---|---|---
HD20794 I | 2204$\pm$16 | 0.0057$\pm$0.0041 | HD115617 III | 44.93$\pm$0.07 | 0.00151$\pm$0.00026
HD20794 II | 1753$\pm$46 | 0.00283$\pm$0.00095 | HD125072 I * | 7137.76 | 0.00630685
HD20807 I * | 2859.91 | 0.00367565 | HD136352 I * | 376.779 | 0.00913149
HD23249 I | 49.57$\pm$0.1 | 0.00241$\pm$0.00049 | HD136352 II * | 7207.58 | 0.00537
HD26965 I | 43.5$\pm$0.07 | 0.00316$\pm$0.00054 | HD140901 I | 7161$\pm$2100 | 0.01205$\pm$0.00082
HD72673 I | 341.2$\pm$3.6 | 0.00508$\pm$0.00076 | HD140901 II | 19.99$\pm$0.02 | 0.0036$\pm$0.0007
HD100623 I | 3205$\pm$130 | 0.01136$\pm$0.00043 | HD160691 I * | 30888.2 [peak=5293.7] | 0.00379764
HD102365 I * | 369.144 | 0.00752353 | HD160691 II * | 362.611 | 0.00247693
HD102365 II * | 18549.80 [peak=7273.6] | 0.00322183 | HD190248 I | 352.9$\pm$1.5 | 0.00261$\pm$0.00032
HD102365 III * | 49.68 | 0.00130454 | HD190248 II | 1171$\pm$36 | 0.0021$\pm$0.00033
HD114613 I * | 27460.5 [peak=7652.9] | 0.00360532 | HD192310 I * | 13621.7 | 0.00676791
HD114613 II * | 365.429 | 0.00211492 | HD192310 II * | 363.678 | 0.00499708
HD115617 I | 346.3$\pm$1.9 | 0.00376$\pm$0.00027 | HD207129 I | 5455$\pm$1900 | 0.0036$\pm$0.00036
HD115617 II | 24.63$\pm$0.02 | 0.00152$\pm$0.00025 | HD207129 II | 1726$\pm$71 | 0.00309$\pm$0.00061

††footnotetext: This table contains all significant EWHα signals identified by
RVSearch. We report the period and EWHα semi-amplitude of each signal. For
signal interpretations, see each star’s individual discussion section. Systems
with a * designation failed to return well constrained MCMC results, generally
producing period uncertainties larger than the median period value, and so we
instead report their MAP orbital solutions. In three cases, even the MAP
period for the long period signal is more than 3x larger than the significant
peak in the $\Delta$BIC periodogram and so we note the period of the original
peak in brackets next to the MAP result.

###  4.5 Injection and Recovery Analysis

After conducting and analyzing the uninformed radial velocity and stellar
activity indicator searches, we use RVSearch to execute an injection/recovery
(I/R) analysis for each star’s residual RV data set. I/R analyses characterize
the completeness of each star’s RV time series, quantifying what combinations
of companion orbital periods and minimum masses we are currently sensitive to.
The results of these I/R efforts make clear what types of planets we would
expect to be able to detect in each star’s Habitable Zone given the current
data sets, and can help to prioritize future RV surveys that aim to push
sensitivity limits to lower mass temperate planets. While we are primarily
interested in the current RV sensitivity within each star’s Habitable Zone, we
use this exercise as an opportunity to quantify our planet sensitivity across
the entirety of the orbital period space covered by the combined RV data sets.

To accomplish this, 5000 synthetic planet signals are injected into the RV
residuals of each star’s uninformed search results. These “planets” are
assigned orbits and $m$ sin $i$ values drawn from log-uniform distributions.
The corresponding periods and RV semi-amplitudes span 2 to 10,000 days and 0.1
to 1,000 $\rm m\,s^{-1}$, respectively. Key properties of the data set such as
observation baseline, measurement values, and uncertainties are preserved.
Following the results of Kipping (2013), which examined the eccentricities of
the population of RV detected exoplanets, the synthetic planets have
eccentricities drawn from a $\beta$ distribution. The same planet search
algorithm used in the uninformed search is then run on these modified data
sets to determine whether the injected signals can be recovered. This
quantifies the planet sensitivity of the existing data, calculating the
probability that a planet of a given $m$ sin $i$ and orbital period would be
detected within the data.

A completeness contour plot is generated, demonstrating what regions of $m$
sin $i$ and orbital period space we are already sensitive to with the existing
data. Figure 7 shows an example of a completeness contour plot for HD 115617.
The three planets published in Vogt et al. (2010) and detected in the
uninformed search stage of our analysis are depicted as black circles, and lie
within the region of $m$ sin $i$ and semi-major axis space where we expect to
be sensitive to Keplerian signals. The three regions of red points above the
detected signals are remnants of the way the injection and recovery analysis
works. Once an injected planet is recovered, it is compared with the already-
fit model to see whether it would be in a reasonably stable orbit location
compared with what has already detected. If the injected planet has the same
orbit as an already-fit signal, RVSearch would not include the planet in the
model due to orbital stability constraints, and so the injected signal is “not
recovered.” This results in columns of non-recovered injected planets that
align with previously detected/removed Keplerian signals. The black circle
corresponding to the final candidate detected in the uninformed search, the
long period signal that overlaps with a period in the activity search, is
located in a regime with a much lower probability of detection. While the
probability of detecting a synthetic at this period and semi-amplitude is
$<$10% according to the figure, the False Alarm Probability (FAP) of this long
period signal detected in the RV time series is 1.22e-10, making it very
unlikely to be a result of random fluctuations in the data.

Figure 7: The RVSearch completeness contour plot for HD 115617. The large
black dots indicate the periodic signals identified by RVSearch in the
archival RV data (see figure 4). The colored points depict the synthetic
planets that were injected into the RV residuals – blue points represent
planets that were successfully recovered, while red points were not recovered.
The red contours display the probability of detection averaged over small
regions of semi-major axis and $m$ sin $i$ space. The black line is the 50%
detection probability contour. The complete set of Injection and Recovery
Analysis plots (46 figures) can be found in the online journal.

Fig. Set7. Injection and Recovery Analysis Contour Plots

Based on Figure 7, we would expect that for planets on a 0.1 AU orbit the
existing RV data would be sensitive down to planet masses of $m$ sin $i$ = 2.6
$M_{\earth}$, a mass that could include terrestrial planets. But when
considering planets on more temperate orbits near 0.914 AU (this star’s EEID)
the existing RV data is only sensitive to planets with masses of $\geq$15
$M_{\earth}$. Thus efforts to detect an Earth analog around HD 115617 would
not succeed with the existing data set. However, we can say with some
confidence that if a 15 $M_{\earth}$ or larger planet were orbiting the star
within its habitable zone, which would preclude the existence of an Earth-
analog on a similar orbit, that we would already be able to detect it. Thus,
at the moment, there is nothing to eliminate the possibility that HD 115617
could host an Earth-analog.

Table 12 describes the results of these injection and recovery tests. For each
star in the set, we report what regions of $m$ sin $i$ and period space we are
already sensitive to using the compiled archival data. We include minimum mass
values for several semi-major axes, marking the limits of sensitivity for each
star’s archival data set.

###  4.6 Speckle Imaging Analysis

In an attempt to identify any stellar companions from the speckle imaging
observations obtained for some of the target stars, reconstructed images
derived from the image reduction process were used (Howell et al., 2011; Horch
et al., 2011). Distribution of all local maxima and minima in the background
of the images as a function of separation were examined by drawing five
concentric annuli each with width of 0.2″ centered at radii of 0″.2, 0″.4,
0″.6, 0″.8, and 1″.0 from the primary star. Standard deviations of these
extrema from the mean background in each annulus were computed by averaging
the values obtained from both maxima and minima. A 5$\sigma$ detection limit,
which is five times brighter than the mean background within each annulus, was
then estimated. Any peak in the image that was above the 5$\sigma$ limit at a
specific angular separation was considered a companion candidate for further
study. For the 6 targets that had speckle imaging observations, no such peaks
were found and therefore no stellar companions were identified. For these non-
detections, 5$\sigma$ limits derived for each annulus in terms of instrumental
magnitude difference ($\Delta$mi, where $i$ is filter type) were used as a
conservative upper limit above which stars should be detected, thus providing
a constraint of the possible undetected low mass companions nearby. Since
$\Delta$mi varies as a function of separation from the primary where at
smaller separations $\Delta$mi is slightly smaller, we reported the estimated
$\Delta$mi at both 0″.1 and 1″.1 from the primary in Table 8. Figure 8
summarizes these results for HD 1581.

Figure 8: Speckle Imaging Analysis plot for HD 1581. Top right: the
reconstructed Speckle images for HD 1581 for each wavelength. Larger plot:
5$\sigma$ flux detection limit relative to image backgrounds, measured in
concentric circular annuli from the center of the image. The complete set of
Speckle Imaging Analysis plots (6 figures) can be found in the online journal.

Fig. Set8. Speckle Imaging Analysis Plots

Table 8: Speckle Imaging Results  HD | Instrument | Date (UT) |  $\Delta$m562 (0.1″) |  $\Delta$m562 (1.1″) |  $\Delta$m832 (0.1″) |  $\Delta$m832 (1.1″) | EWHα Correlation
---|---|---|---|---|---|---|---
1581 | Zorro | 2020 Oct 29 | 4.31 | 7.50 | 4.43 | 7.95 | N/A
20766 | Zorro | 2020 Oct 23 | 5.02 | 7.36 | 4.82 | 8.00 | -0.48
20807 | Zorro | 2020 Oct 23 | 4.80 | 6.29 | 4.70 | 8.22 | -0.17
140901 | Zorro | 2021 Jul 22 | N/A | N/A | 4.44 | 7.79 | -0.68
146233 | ‘Alopeke | 2021 Jun 27 | 4.66 | 6.56 | 4.74 | 9.33 | -0.06
196761 | ‘Alopeke | 2021 Jun 27 | 4.97 | 6.02 | 5.05 | 8.22 | N/A

##  5 Systems with updated parameters

In this section, we present results from targets for which we recover
previously published planetary systems, stellar companions, and activity
cycles. For the cases where we have additional data or increased precision, we
cite the current accepted values and report updates to these systems’
parameters. Table 9 contains former and new (this work) parameters for
previously reported exoplanet systems.

###  5.1 HD 13445 (GJ 86 A)

HD 13445 (GJ 86 A, HR 637, HIP 10138) is a nearby K1V star (Gray et al., 2006)
at $d$ = 10.76 pc ($\varpi$ = 92.9251 $\pm$ 0.0461 mas; Gaia Collaboration et
al., 2020). GJ 86A has both a known stellar companion (GJ 86B, WD 0208-510)
and an exoplanet (GJ 86Ab, HD 13445b). Farihi et al. (2013) characterize the
white dwarf companion GJ 86B and constrain its orbit – estimating a spectral
type of DQ6, mass = 0.59 $\pm$ 0.01 $M_{\sun}$, orbital period of $P=120-481$
yr, and adopted system age of 2.5 Gyr.

We detect two signals in the RVs. One is the known exoplanet, and the other
may be caused by the binary companion, but is too poorly constrained to say
for certain. Butler et al. (2001) published the planet with 15.76 day period.
We derive orbital parameters for GJ 86Ab of $P_{b}=15.764862\pm 0.000043$ d,
$K_{b}=377.58\pm 0.77$ $\rm m\,s^{-1}$, $e_{b}=0.0485\pm 0.0018$. The second
significant detection has a peak in the periodogram with $P=20504$ days.
Because this is much longer than the observation baseline for the target, the
MCMC fit for the signal is not physical. We categorize this signal as LPS and
note that more data would be required to constrain this signal further.
Further discussion of the LPS category of detection can be found in Section
4.1.

Finally, we note that H$\alpha$ analysis shows strength in the periodogram at
$P=2001.7$ days, though the detection does not cross the False Alarm
Probability threshold.

###  5.2 HD 16160 (GJ 105 A)

HD 16160 (GJ 105 A, HR 753, HIP 12114) is a nearby K3V spectral standard star
(Keenan & McNeil, 1989) in a triple system, located at $d=7.23$ pc
($\varpi=138.2084\pm 0.1436$ mas; Gaia Collaboration et al., 2018). The star
is a $5.1\pm 1.1$ Gyr-old thin disk (Ramírez et al., 2012), low-activity (log
$R^{\prime}_{HK}$= -4.87; Gomes da Silva et al., 2021) star with magnetic
activity cycle of $P_{\rm cyc}$ $\simeq$ 12.18 yr (Willamo et al., 2020) or
$12.7\pm 0.11$ yr (Boro Saikia et al., 2018). From analysis of the Mt. Wilson
survey data, Donahue et al. (1996) reports an average rotation period of
$P_{\rm rot}$ = 48.0 d over 5 seasons, with individual seasonal rotation
periods ranging from 42.2 d to 51.5 d (i.e, pronounced differential rotation).

GJ 105 A has a faint M7V companion GJ 105 C (HD 16160B, WDS J02361+0653B)
observed at separations between 1″.7 and 3″.3 (Golimowski et al., 1995, 2000;
Mason et al., 2001)151515References to the Washington Double Star (WDS)
catalog (Mason et al., 2001) are actually referring to the regularly updated
WDS table at Vizier (https://cdsarc.unistra.fr/viz-bin/cat/B/wds)., and the
M4.0V star GJ 105 B star on a very wide orbit at 164″ separation (Mann et al.,
2015; van Maanen, 1938). Astrometric perturbations attributed to a low-mass
stellar companion to GJ 105 A (BD+6∘ 398) were first reported by Lippincott
(1973), who measured photographic plate positions from the Sproul astrometric
program taken between 1937 and 1968 to estimated the orbit to have $P=50$ yr
and $e=0.6$, and predicted the companion to be a 0.10 $M_{\sun}$ star of type
M6.

Golimowski et al. (2000) concluded that the companion C first observed in 1993
with the Palomar 60” Adaptive Optics Coronagraph (Golimowski et al., 1995) was
consistent with (1) the astrometric perturbations with $\sim$50-60 yr
periodicities reported by Lippincott (1973) (and later refined by Ianna (1992)
and Heintz & Cantor (1994)), and (2) the 11 m s-1 yr-1 radial velocity trend
observed during the 1990s by Cumming et al. (1999). Ianna (1992) analyzed
photographic plate positions for GJ 105 A between 1915 and 1992 and estimated
$P=59.5$ yr, astrometric amplitude $\alpha$ = 0″.293, $e=0.35$, and companion
mass $M_{C}=0.13$ $M_{\sun}$. Our analysis of the archival RV data with
RVSearch yields a long-period signal with $P=22999\pm 1200$ d ($63.0\pm 3.3$
yr), $K=702.5\pm 2.9$ $\rm m\,s^{-1}$, and $e=0.6075\pm 0.0092$, which is
reasonable for the orbit of GJ 105 C.

These values are not far from the most recent astrometric-only orbital
analysis from Heintz & Cantor (1994), who estimated $P=61$ yr, $e=0.67$,
$i=49^{\circ}$ (consistent with companion mass $M_{C}=0.10$ $M_{\sun}$). They
also align well with the values reported in the recent Rosenthal et al.
(2021), who found $a=16.37\pm 0.28$ AU and $e=0.6427^{+0.0038}_{-0.0039}$.
Using the stellar mass adopted in this paper, we calculate the period to be
approximately $P=77$ years. This also aligns with the signal we recover,
though our detection is significantly less well constrained than in other
works. A joint analysis of the radial velocity, astrometric, and imaging data
over the past century could yield stronger orbital constraints and a more
accurate dynamical mass estimate, but is beyond the scope of this study.

Analysis of S-indices using RVSearch returns two significant activity
detections, with parameters: $P_{I}=4232\pm 310$ d, $e_{I}=0.17\pm 0.055$ and
$P_{II}=3204\pm 110$ d, $e_{II}=0.413\pm 0.092$. The first of these aligns
fairly well with the magnetic activity cycle reported by Willamo et al.
(2020). We recommend a more in-depth study of this star’s activity to fully
characterize the sources of these periodic signals in the S-indices.

###  5.3 HD 20794 (82 Eri)

82 Eri (GJ 139, HD 20794, HR 1008, HIP 15510) is a G8V star (Gray et al.,
2006) at $d=6.00$ pc ($\varpi=166.5242\pm 0.0784$ mas; Gaia Collaboration et
al., 2020). The star is somewhat cooler than the Sun ($T_{\rm eff}$$\,=5398$
K), metal poor ([Fe/H]$\,=-0.41$) (Tsantaki et al., 2013), and very inactive
(log $R^{\prime}_{HK}$ = -5.025) (Lovis et al., 2011). Lovis et al. (2011)
reported a magnetic activity cycle of $P_{\rm cyc}$ = 751${}_{-25}^{+290}$ d
($2.06^{+0.79}_{-0.07}$ yr) based on 197 log $R^{\prime}_{HK}$ measurements
over a span of 2694 d. The star was reported to host three planets by Pepe et
al. (2011), with orbital periods of $P_{b}=18.1$ d, $P_{c}=40.1$ d, and
$P_{d}=90.3$ d, based upon their analysis of 173 _HARPS_ RV data points taken
between 2003 and 2011. A reanalysis of the system was published in 2017, which
made use of an updated _HARPS_ data set containing 713 RV epochs obtained
between 2003 and 2013 (Feng et al., 2017b). The Feng et al. (2017b) results
confirm the Keplerian nature of the 18 and 90 day signals put forth in Pepe et
al. (2011) and identify two additional planet candidates with orbital periods
of 147 and 330 days. They find only weak evidence of the $\sim$40 day signal
reported by Pepe et al. (2011), however, and assert that more data are
necessary to determine the nature of this signal.

Our data set for HD 20794 contains 763 _HARPS_ epochs, spanning 2003 - 2016,
along with 549 _UCLES_ points, and 77 _PFS_ points. Running this combined RV
data set through RVSearch, we confirm HD 20794 b ($P_{b}=18.305\pm 0.0052$ d,
$K_{b}=0.807\pm 0.089$ $\rm m\,s^{-1}$ $e_{b}=0.17\pm 0.11$) and HD 20794 d
($P_{d}=89.766\pm 0.085$ d, $K_{d}=0.86\pm 0.12$ $\rm m\,s^{-1}$
$e_{d}=0.27\pm 0.11$) in Tables 9 and 4.

Similarly to Feng et al. (2017b), we do not register a detection of the
$\sim$40 day signal attributed to HD 20794 c, though we note that the
residuals periodogram shows significant power for a signal at 40.2 days, which
likely corresponds to the reported 40.1-day period of HD 20794 c in Pepe et
al. (2011). If the signal were Keplerian in nature, however, we would expect
its statistical significance to increase as more RV data points are added to
the analysis. This is especially true for a star that exhibits the low levels
of RV scatter we see in the HD 20794 RVs, where RMS = 1.99 $\rm m\,s^{-1}$ and
1.00 $\rm m\,s^{-1}$ for _HARPS_ and _PFS_ , respectively.

Another possibility is that the 40 day signal is tied to stellar variability.
The star’s low chromospheric activity (log $R^{\prime}_{HK}$= -5.03) is
consistent with a rotation period of $P_{\rm rot}$ $>$ 34 days for a star of
its color (using activity-rotation relations of Mamajek & Hillenbrand, 2008),
and so rotational modulation at a period of roughly 40 days would not be
surprising. Yet applying RVSearch to the star’s assembled S-index data does
not reveal significant power at or near a 40 day period. We also do not
significantly detect planet candidates e, f, or g, as reported by Feng et al.
(2017b). There is another peak in the RV residuals periodogram close to 330
days, the orbital period of candidate f, but similarly to the 40 day signal it
does not cross the threshold of being detected by RVSearch. Given the more
sophisticated treatment of stellar variability and correlated noise in the
that paper, however, we do not view our non-detections as a refutation of
these candidates.

S-index analysis returns no significant signals, but analysis of H$\alpha$ in
the _UCLES_ data yields two significant detections: $P_{I}=2204\pm 16$ d,
$e_{I}=0.886\pm 0.049$ and $P_{II}=1753\pm 46$ d, $e_{II}=0.68\pm 0.15$. The
high eccentricities fit to these signals are cause for skepticism regarding
their exactness, but we regard them as good evidence for the existence of an
approximately 7-8 year activity cycle for this star.

###  5.4 HD 22049 ($\epsilon$ Eri)

$\epsilon$ Eri (GJ 144, HD 22049, HR 1084, HIP 16537, Ran) is a young, active
K2V spectral standard star (Keenan & McNeil, 1989) at $d=3.22$ pc
($\varpi=310.5773\pm 0.1355$ mas; Gaia Collaboration et al., 2020) with a
candidate planet and debris disks (Mawet et al., 2019). Analysis of the Mt.
Wilson Ca II H & K data of $\epsilon$ Eri by Donahue et al. (1996) found
strong evidence for differential rotation, with season-averaged rotation
periods ranging from $P_{\rm rot}$ = 11.04 to 12.18 d over 9 seasons, with
average $P_{\rm rot}$ = 11.68 d. An archival analysis of 45 years of
chromospheric activity data by Metcalfe et al. (2013) identified two prominent
activity cycles for $\epsilon$ Eri at $P_{cyc1}=2.95\pm 0.03$ yr and
$P_{cyc2}=12.7\pm 0.3$ yr, at approximately 0.68$\times$ and 2.94$\times$
planet orbital period reported by Mawet et al. (2019).

We recover the one confirmed planet ($P=2690\pm 30$ d = $7.365\pm 0.082$ yr;
Mawet et al., 2019), but with a less certain period of $P_{b}=2832\pm 120$ d
($7.76\pm 0.33$ yr), and semiamplitude and eccentricity $K_{b}=11.1\pm 1.2$
$\rm m\,s^{-1}$, $e_{b}=0.09\pm 0.08$. The periodogram residuals show a signal
at 12.4 days, which agrees well with rotation periods reported by Donahue et
al. (1996).

We detect one S-index activity signal with parameters $P_{I}=1086.7\pm 7.1$ d
(2.98$\pm$0.02 years) and $e_{I}=0.268\pm 0.081$. This agrees with the 2.95
year activity cycle reported by Mawet et al. (2019).

We note that we do not detect the false positive $P=773.4^{+4.7}_{-4.8}$d
signal reported by Rosenthal et al. (2021).

###  5.5 HD 26965 (40 Eri A)

40 Eri A ($o^{2}$ Eri A, GJ 166 A, HD 26965, HR 1325, Keid) is a famous nearby
($d=4.98$ pc) ($\varpi=200.62\pm 0.23$ mas; van Leeuwen, 2007) K0.5V standard
star (Keenan & McNeil, 1989) in a triple system with a white dwarf (B) and M
dwarf (C) component. From time series analysis of chromospheric activity data
from the Mt. Wilson survey, the rotation period of the star has been
previously measured to be 43 d (Baliunas et al., 1996) and 42 d (Frick et al.,
2004), and predicted rotation periods (based on log $R^{\prime}_{HK}$ values
and correlations with rotation for other cool dwarfs) have been reported to be
37.1 d (Saar & Osten, 1997), $42.2\pm 4.4$ d (Lovis et al., 2011), and 43 d
(Isaacson & Fischer, 2010). Long term monitoring of Ca H & K emission from 40
Eri A has revealed a magnetic activity period with measured period
$P_{cyc}=10.1\pm 0.1$ yr (Baliunas et al., 1995), $10.4$ yr (3800 d; Frick et
al., 2004), $9.18^{+2.20}_{-1.48}$ yr (Lovis et al., 2011), and
$10(9.57-10.5)$ yr (Oláh et al., 2016), or $10.23\pm 0.07$ yr (Boro Saikia et
al., 2018).

Díaz et al. (2018) presented an extensive analysis of $\sim$1100 spectra taken
using _HIRES_ , _PFS_ , CHIRON, and _HARPS_ , and reported a strong signal at
$P=42.364\pm 0.015$ d, $K=1.59\pm 0.15$ $\rm m\,s^{-1}$, $e=0.017\pm 0.046$,
but found it challenging to distinguish this signal from the star’s rotation.
Shortly after, Ma et al. (2018) conducted a reanalysis of the Díaz et al.
(2018) data combined with 133 new spectroscopic observations taken with the
TOU instrument. Ma et al. (2018) found that while there were signals in the
star’s activity indices at $41.2\pm 0.9$ d and $39.2\pm 0.7$ d likely
corresponding to (differential) stellar rotation, the well-defined $P=42.38$ d
signal persisted over the seasons and between activity states – concluding
that the signal was most likely due to a planet. Rosenthal et al. (2021)
reported a signal at $P=42.305^{+0.015}_{-0.019}$ d ($K=1.82^{+0.43}_{-0.31}$
$\rm m\,s^{-1}$) and considered it a false positive attributed to the star’s
rotation, and another longer signal at $P=3560^{+200}_{-580}$ d
($K=1.89^{+0.37}_{-0.32}$ $\rm m\,s^{-1}$) attributed to long-period magnetic
activity cycle.

We detect a strong significant RV signal with $P_{I}=42.303\pm 0.025$ days,
$K_{I}=1.40\pm 0.22$ $\rm m\,s^{-1}$, $e_{I}=0.37\pm 0.17$, very similar to
that reported previously by Díaz et al. (2018) and Ma et al. (2018). Analysis
of H$\alpha$ data for this target returns a well-correlated detection with
$P=43.504\pm 0.066$ d, $e=0.37\pm 0.18$. The extreme proximity of these two
detections leads us to classify this RV detection conclusively as activity.
Additionally, we detect RV signals with $P_{II}=37.33\pm 0.02$ d,
$K_{II}=1.17\pm 0.19$ $\rm m\,s^{-1}$, $e_{II}=0.14\pm 0.12$, and
$P_{II}=367.9\pm 3.1$ d, $K_{III}=1.63\pm 0.88$ $\rm m\,s^{-1}$,
$e_{III}=0.46\pm 0.27$. Looking closely at the periodogram, we note that the
37-day period signal is extremely close to the yearly alias of the 42-day
signal, and report it as such. The 365-day signal is likely driven by the
window function of this star as the phase folded fit makes clear that a
significant (>25%) portion of the orbital phase space is unpopulated due to
seasonal observing constraints. We therefore classify this as a false positive
signal.

In the S-index activity analysis, we find a signal with $P_{I}=3177\pm 84$ d
($8.70\pm 0.23$ yr) and $e_{I}=0.059\pm 0.051$, which agrees well with
Rosenthal et al. (2021) and which we report as an update to the 10-year
magnetic cycles previously published.

###  5.6 HD 39091 ($\pi$ Men)

$\pi$ Men (GJ 9189, HD 39091, HR 2022, HIP 26394) is a G0V star (Gray et al.,
2006) at $d=18.28$ pc ($\varpi=54.6825\pm 0.0354$ mas; Gaia Collaboration et
al., 2020). $\pi$ Men has three published planets. $\pi$ Men b was first
published in Jones et al. (2002), and was discovered using radial velocity
data from the _UCLES_ instrument. We recover $\pi$ Men b in our radial
velocity data with $P_{b}=2089.05\pm 0.46$ d, $K_{b}=196.5\pm 0.6$ $\rm
m\,s^{-1}$ and $e_{b}=0.6428\pm 0.0017$. These parameters are comparable to
recent estimates by Huang et al. (2018), Gandolfi et al. (2018), and Xuan &
Wyatt (2020). Our analysis includes newly released _PFS_ data, building upon
the _HARPS_ \+ _UCLES_ orbital fits performed in the previous works, and so we
report our detection as an update to the orbital parameters of $\pi$ Men b.

$\pi$ Men c was the first new transiting planet discovered by NASA’s
Transiting Exoplanet Survey Satellite (TESS; Huang et al., 2018). The planet
was not robustly detected by RVSearch ’s uninformed search of the RVs,
although there is a well defined peak in the residuals periodogram at the
expected period of $P_{c}=6.2$ d.

$\pi$ Men d is a recently detected, sub-Neptune mass planet candidate reported
to have $P_{d}=124.64^{+0.48}_{-0.52}$ days, $K_{d}=1.68\pm 0.17$ $\rm
m\,s^{-1}$, and $e_{d}=0.22\pm 0.079$ (Hatzes et al., 2022). These parameters
are driven largely by observations taken as part of intensive _HARPS_ and
_ESPRESSO_ observing campaigns, the data for which is not included in this
analysis.

We detect a similar signal, consistent to within 1.5$\sigma$ on all
parameters, albeit with larger uncertainties on the planet’s RV semi-
amplitude. Our best fit results for this third signal are $P_{d}=125.58\pm
0.27$ d, $K_{d}=2.16\pm 0.42$ $\rm m\,s^{-1}$, and $e_{d}=0.16\pm 0.15$.

Activity analysis of both S-index and H$\alpha$ data for this target recovers
no significant signals.

###  5.7 HD 69830 (GJ 302)

HD 69830 (GJ 302, HR 3259, HIP 40693) is a well-studied star of type G8+V
(Gray et al., 2006) at distance $d$ = 12.58 pc ($\varpi$ = 79.4953 $\pm$
0.0400 mas; Gaia Collaboration et al., 2020), famous for hosting a planetary
system of three Neptunes (Lovis et al., 2006) and a dusty debris disk
(Beichman et al., 2005). The stellar rotation period has been estimated by
Isaacson & Fischer (2010) to be 42 days, while Simpson et al. (2010) report
$35.1\pm 0.8$ d.

With 1515 additional RV measurements since Lovis et al. (2006), we recover all
three of the same planets with slightly different periods and amplitudes (see
Table 9 for a full comparison). For HD 69830 b, we report $P_{b}=8.66897\pm
0.00028$ d, $K_{b}=3.4\pm 0.1$ $\rm m\,s^{-1}$, and $e=0.128\pm 0.028$. For HD
69830 c: $P_{c}=31.6158\pm 0.0051$ d, $K_{c}=2.6\pm 0.1$ $\rm m\,s^{-1}$, and
$e_{c}=0.030\pm 0.027$, and for HD 69830 d: $P_{d}=201.4\pm 0.4$ d,
$K_{d}=1.5\pm 0.1$ $\rm m\,s^{-1}$, and $e_{d}=0.080\pm 0.071$. The
uncertainties on our derived orbital periods are slightly smaller than those
recently reported by Rosenthal et al. (2021), which used data from _HIRES_ and
the _APF_ but not the other instruments included here, and appear to be the
most precise yet reported.

Rosenthal et al. (2021) find two false positives in their analysis with
periods of 201 and 382 days, which they attribute to systematic errors.
However, the $P=201$ d signal is in fact a detection of Lovis et al. (2006)’s
planet d, and its inclusion in Rosenthal et al. (2021)’s false positive table
(Table 7) is a typo. We do not recover the 382 day false positive reported by
Rosenthal et al. (2021), but our inclusion of multiple instruments’ data which
are not included in Rosenthal et al. (2021) may dilute individual facilities’
systematics.

Additionally, we recover three significant signals in the S-index activity
analysis. S-index signal I has $P_{I}=3989\pm 190$ d ($10.93\pm 0.52$ yr),
which is similar to the Sun’s own 11-year activity cycle (e.g. Hathaway,
2015). Lovis et al. (2011) reported a poorly constrained activity cycle period
of $P_{\rm cyc}$ = 5865${}_{-1235}^{+\infty}$ d, which is 1.46$\sigma$ longer
than our measured activity signal I, but they are likely detections of the
same long-term magnetic activity cycle. We report S-index activity signal I as
a magnetic activity cycle. S-index activity signal II has $P_{II}=731\pm 31$ d
($2.00\pm 0.08$ yr) which we note is almost twice the expected _HARPS_ yearly
systematic. Attribution of this signal to a _HARPS_ systematic is further
supported by the complete lack of corresponding signal in the _UCLES_
H$\alpha$ analysis for this target, which not only returns no significant
detections but shows almost no strength in the periodogram at this period.

Finally, S-index activity signal III has $P_{III}=2530\pm 180$ d ($6.93\pm
0.49$ yr). This may be another magnetic activity cycle, though we note that
there appears to be a minimum in the H$\alpha$ periodogram at this period. We
recommend further investigation by future work to understand this signal.

Comparison of the star’s rotation period and cycle periods with other nearby
Sun-like stars in Fig. 9 of Boro Saikia et al. (2018) indicate that HD 69830
may be a rare case of a slow-rotating star with two detected activity cycles
($10.93\pm 0.52$ yr and $6.93\pm 0.49$ yr, both of which are near the
“inactive branch” locus in $P_{rot}$ vs. $P_{cyc}$ space).161616A similar
example from Boro Saikia et al. (2018) is the K2V star HD 149661, with
activity cycles of $15.3\pm 0.4$ and $7.7\pm 0.12$ yr (see also Saar &
Brandenburg, 1999).

###  5.8 HD 75732 (55 Cnc)

55 Cnc ($\rho^{1}$ Cnc, GJ 324 A, HD 75732, HR 3522, HIP 43587, Copernicus) is
a famous, K0IV-V (Gray et al., 2003) exoplanet host star at $d=12.58$ pc
($\varpi=79.4482\pm 0.0429$ mas; Gaia Collaboration et al., 2020). 55 Cnc also
has a wide separation (85″, $\sim$1060 AU ) low-mass stellar companion 55 Cnc
B. Bourrier et al. (2018) presents an extensive review of the 55 Cancri system
and its five exoplanets (see also e.g., Fischer et al., 2008; Endl et al.,
2012; Fischer, 2018). Bourrier et al. (2018)’s analysis contains 1552 RV
measurements from a combination of both first generation and more modern
precise RV spectrographs spanning 25 years. In comparison, this work includes
only modern precise RV data sets and contains 837 RV measurements taken over
18 years. Our analysis does, however, have longer _HIRES_ and _APF_ baselines
than present in Bourrier et al. (2018). We recover signals corresponding to
all five reported planets around 55 Cnc and report updates to the parameters
of planets b, c, e, and f in Table 4.

Our detection of the long period planet 55 Cnc d suffers from our more limited
observational baseline and the months of time between the _HIRES_ -Pre and
-Post data sets. The $\Delta$BIC periodogram peak suggests a 4421 day period,
which is notably shorter than the Pd = 5574.2${}^{+93.8}_{-88.6}$ result from
Bourrier et al. (2018). After fitting the full system, RVSearch arrives at a
best-fit model of $P_{d}=14951\pm 5100$ d, $K_{d}=54\pm 5$ $\rm m\,s^{-1}$,
and $e_{d}=0.515\pm 0.086$ for this long period signal. This overly long,
poorly constrained result exhibits similar behavior to the other ‘LPS’ signals
in this work due to the lack of full orbital phase coverage. Due to the period
of the initial periodogram peak we attribute this signal to 55 Cnc d, but we
do not report this as an updated orbital parameter result.

Baluev (2015) report an activity cycle for 55 Cnc of period
$P_{cyc}=12.6^{+2.5}_{-1.0}$ yr, with a prediction that an activity minimum
would occur around 2014-2015. This correlates with our S-index detection at
$P=3801\pm 130$ d ($10.4\pm 0.36$ yr), so we report this signal as an update
to the previously published activity cycle. The activity cycle prediction from
Baluev (2015) also does not align with the signal reported in Rosenthal et al.
(2021).

###  5.9 HD 85512 (GJ 370)

HD 85512 (GJ 370, HIP 48331) is a nearby, somewhat metal poor ([Fe/H] = -0.26)
(Tsantaki et al., 2013), inactive (log $R^{\prime}_{HK}$= -4.976; Costes et
al., 2021) K6V(k) star (Gray et al., 2006) at $d=11.28$ pc ($\varpi$ = 461.446
mas; Gaia Collaboration et al., 2020). The star has one previously reported
planet at $P_{b}=58.43\pm 0.13$ days (Pepe et al., 2011), recovered through
radial velocity analysis of 185 _HARPS_ data points.

Our RVSearch analysis, run on an additional 1,127 data points, does not detect
a 58-day signal, but rather a shorter period signal with parameters:
$P_{b}=51.195\pm 0.073$ d, $K_{b}=0.438\pm 0.079$ $\rm m\,s^{-1}$, and
$e_{b}=0.3\pm 0.19$. This change, from $P_{b}=58.43\pm 0.13$ days in Pepe et
al. (2011) to $P_{b}=51.195\pm 0.073$ days in this study amounts to a
48$\sigma$ difference, well beyond any expected planetary orbit refinement.
The reported amplitudes are also somewhat inconsistent, with Pepe et al.
(2011) reporting $K_{b}=0.769\pm 0.090$ $\rm m\,s^{-1}$ a 2.8$\sigma$
difference from our RVSearch result.

Figure 9: Moving periodogram (MP) for the combined HD 85512 radial velocity
data sets. The colors encode the scaled MP power, which is truncated to
optimize the visualization of signals. The previously reported 58.43 day
planet is visible as a dark red horizontal band on the left side of the MP,
denoting its significance in the first half of the RV time series, but
bifurcates and then disappears in later years. A second signal at $P\simeq 51$
d takes over in the latter half of the time series, but does not exhibit a
tight enough period range to be seriously considered as a planet candidate.

We note that there is a suggestive similarity between the reported Doppler
periods from both Pepe et al. (2011) and our work and the predicted rotation
period for the star. Based on HD 85512’s chromospheric activity, Pepe et al.
(2011) predicted $P_{\rm rot}$ = $47.13\pm 6.98$ d, and Lovis et al. (2011)
predicted $P_{\rm rot}$ = $50.9\pm 7.0$ d – i.e. within 0.58$\sigma$ and
0.04$\sigma$ of the RV signal we measure ($P_{b}=51.195\pm 0.073$ d). Pepe et
al. (2011) searched for power in the log $R^{\prime}_{HK}$ activity indicator
and the CCF line bisector (BIS) but did not detect any excess power consistent
with stellar rotation between 50 and 100 days. Our analysis of the S-index
measurements detects significant periods at 44, 45, and 51 days, causing us to
suspect rotation as the cause of this signal.

To investigate the consistency of these two periods over time, we generated a
moving Bayes Factor Periodogram (BFP) using the AGATHA software suite (Feng et
al., 2017a). Since RV data are typically not measured in a uniform way,
especially when combining results from different surveys, the consistency of a
true Keplerian signal may depend on the sampling cadence even if the power is
normalized. Moving periodograms can help to identify false positives if a
signal is found to be inconsistent even during spans where data was taken at a
high cadence and over a number of nights comparable with or longer than the
signal period.

The moving periodogram results for HD 85512 (Figure 9) show a prominent peak
in the 58 day region when looking at the first half of the RV time series.
This signal, however, bifurcates in roughly 2017 (JD $\simeq$ 2458000) and
splits into two weaker periodicities of 59 and 57 days. At approximately the
same time a more prominent peak appears at the $P\simeq 51$ day period
identified by RVSearch, and becomes the most significant period for the
duration of our observational baseline.

As low-mass stars can manifest differential rotation (e.g. Donahue et al.,
1996), the reported 58 d and 51 d periods could be due to active regions
rotating at different latitudes. The trend in differential rotation among G/K
dwarfs from the Mt. Wilson survey shown by Donahue et al. (1996) (their Fig.
3) shows that K dwarfs with $P_{\rm rot}$ $\simeq$ 50 d could exhibit
differential rotation at the $\Delta P\,\simeq\,9$ d level. Indeed the
previously discussed K3V star HD 16160 (see Sec. 5.2) was the Mt. Wilson
survey poster child for such extreme differential rotation, exhibiting
seasonal mean rotation periods ranging from 42.2 to 51.5 d over five seasons.
So it is certainly reasonable for a slow-rotating mid-K dwarf like HD 85512 to
manifest differential rotation over $P_{\rm rot}$ $\simeq$ 44-58 d.

Given the lack of periodic consistency for both signals across the RV time
series, we assert that the reported companion HD 85512 b from Pepe et al.
(2011) is not caused by a physical planet, but rather that the signal is due
to the star’s rotation. We adopt the notation of calling this HD 85512 RV
Signal II (rather than HD 85512 b) in Table 4, since it is the second RV
signal fit by the RVSearch algorithm.

RVSearch finds one additional significant signal in the RV data, with an
initial $\Delta$BIC periodogram peak of 3891 days. The best fit period for RV
Signal I after running the RV data through RVSearch ’s MCMC analysis is
$P_{I}=9646\pm 5500$ days, which we categorize as a ‘LPS’ due to the large
error bars and period that stretches beyond the baseline of the combined RV
data.

While Pepe et al. (2011) presented time series log $R^{\prime}_{HK}$ data for
the star over a span of 2745 d, and sinusoidal-looking activity variability
was observed, they did not estimate a magnetic cycle period. By eye,
interpreting the Pepe et al. (2011) log $R^{\prime}_{HK}$ data near JD 2453000
as a minimum and JD 2454500 as a maximum, one can infer $P_{\rm cyc}$ $\simeq$
3000 d. And indeed, when analyzing the majority of the Pepe et al. (2011) data
set (175 of the 185 observations) Lovis et al. (2011) estimated an activity
cycle of $P_{\rm cyc}$ = $3793^{+806}_{-566}$ d ($10.38^{+2.21}_{-1.55}$ yr).

Here we compile in total 1312 S-index measurements taken over a baseline of
$\sim$7000 days. With this longer baseline, we see a subsequent activity
minimum around JD 2456600 and a maximum around JD 2458800 and RVSearch
identifies a significant S-index signal with $P=4245\pm 52$ d ($11.62\pm 0.14$
yr). This falls well within the 1$\sigma$ uncertainties of the Lovis et al.
(2011) activity cycle, and better constrains the period by a factor of 10. It
is also consistent with the $\Delta$BIC periodogram peak in the RV data, and
so we note that it is likely that the LPS in the RVs is caused by a magnetic
activity cycle, however more data is needed to definitively characterize the
nature of this signal.

Our S-Index analysis returns a multitude of additional signals falling between
the rotation period and magnetic activity cycle of HD 85512. To fully
characterize the significance of all these signals, a much more in depth study
of the system is required than is covered within the scope of this work. The
full list of signals can be found in the activity summary plot contained in
the figure set in the online journal. We leave further analysis of the
activity results from this target to future work.

###  5.10 HD 102365 (GJ 442A)

HD 102365 (GJ 442 A, HR 4523, HIP 57443) is a G2V star (Gray et al., 2006) at
$d=9.32$ pc ($\varpi=107.3024\pm 0.0873$ mas; Gaia Collaboration et al.,
2020). The star is just slightly cooler ($T_{\rm eff}$$\,=5618\pm 14$ K) and
of similar chromospheric activity to the Sun (log $R^{\prime}_{HK}$ = -4.94)
(Meunier et al., 2022), however the star is substantially more metal poor
([Fe/H]$=-0.31\pm 0.02$) compared to the Sun (Soubiran et al., 2022). Recent
age estimates for the star make it ancient: $11.3\pm 0.9$ Gyr (Nissen et al.,
2020), $12.46^{+1.04}_{-1.42}$ Gyr (Gaia Collaboration et al., 2021), $13.1\pm
1.5$ Gyr (Casali et al., 2020). The star has a low-mass stellar companion of
type M4V (Henry et al., 2002) at projected separation 22″.72 or 211 AU (Tian
et al., 2020). The masses of the stars A and B are $0.88^{+0.02}_{-0.03}$
$M_{\sun}$ (Aguilera-Gómez et al., 2018) and 0.192 $M_{\sun}$ (Mugrauer,
2019), respectively. Tinney et al. (2011) reported an exoplanet with orbital
period $P_{\rm orb}$$=122.1\pm 0.3$ d, $K=2.40\pm 0.35$ d, and eccentricity
$e=0.34\pm 0.14$, corresponding to a Neptune-like predicted mass of $16.0\pm
2.6$ $M_{\earth}$. No subsequent orbital solution has been reported over the
past decade.

We recover this same planet as (Tinney et al., 2011), with updated orbital
parameters thanks to our additional RV observations. We report parameters for
HD 102365 b of $P=121.3\pm 0.25$ d, $K=1.38\pm 0.23$ $\rm m\,s^{-1}$, and
$e=0.28\pm 0.15$. Note that our RV amplitude is only 58% of that reported by
Tinney et al. (2011), resulting in a significantly lower $m$ sin $i$ of
$9.34^{+1.52}_{-1.50}$ $M_{\earth}$ (Table 4).

We find no significant signals in analysis of the S-index data, but the
H$\alpha$ data analysis yields three periodic signals. The first has a period
of approximately one year, so we assert that it is most likely caused by the
seasonal availability of the star. The second H$\alpha$ signal is fit to a
periodogram peak of 7273.6 days, longer than the baseline of the _UCLES_ data.
This peak is most likely the same long-period trend present in most of the
_UCLES_ H$\alpha$ data as described in Section 3.3, and so we disregard from
consideration as astrophysical. The third H$\alpha$ peak has period
$P_{III}=49.68$ d and $e_{III}=0.08$. While the peak is sharp and well-
defined, and could reasonably correspond to the stellar rotation period for
this ancient star, it does not show any corroborating signal in the S-indices.
We note that the MCMC fit to the EWHα data settles on a solution for the
longest signal that is nonsensical ($P=36122\pm 64000$ days) and so we report
the MAP best fit solution in the summary table. Even the MAP result suffers
from the similarity between the long period signal and the total observational
baseline of the _UCLES_ data, however, and the resulting fit lands on an
orbital period of P=18549 days; clearly well beyond the scope of our data set.

###  5.11 HD 114613 (GJ 9432)

HD 114613 (GJ 9432, GJ 501.2, HR 4979, HIP 64408) is a G4IV star (Gray et al.,
2006) at $d=20.46$ pc ($\varpi=48.8691\pm 0.1058$ mas; Gaia Collaboration et
al., 2020). Brewer et al. (2016) finds that the star is more massive ($1.24\pm
0.17$ $M_{\sun}$) and metal-rich ([Fe/H] = 0.17) than the Sun, and also cooler
($T_{\rm eff}$ = 5641 K) and larger ($2.14\pm 0.06$ $R_{\sun}$) with lower
surface gravity ($\log g$ =3.87). Lovis et al. (2011) report the star to have
very low chromospheric activity (log $R^{\prime}_{HK}$ = -5.509) with a
magnetic activity cycle of $P_{\rm cyc}$ $=897_{-53}^{+61}$ d
(2.46${}^{+0.15}_{-0.17}$ yr).

Wittenmyer et al. (2014) reported a planet with $P_{\rm{b}}=3827\pm 105$ days
and a semi-amplitude of $K_{\rm{b}}=5.4\pm 0.4$ $\rm m\,s^{-1}$ . Our search
of the updated RV data set, which contains 980 additional velocities from
_HARPS_ , _HIRES_ , and _PFS_ , does not recover this planet but rather
reveals a much longer period signal at $P_{I}=6622\pm 270$ d ($18.13\pm 0.74$
yr) with a semi-amplitude of $K_{I}=7.29\pm 0.44$ $\rm m\,s^{-1}$, suggestive
of a planet candidate with $m$ sin $i$ $\simeq$ 0.74 $\,M_{\rm J}$.

However, both the S-index data and the EWHα periodograms identify significant
signals at similar periods to the RV periodogram, with the S-index peak
appearing at 7563 days and the EWHα peak at 7653 days. Both of these signals
struggle with similarity in duration to the baselines of their respective data
sets, however, as the lack of a single activity indicator that covers the full
8500 day span of radial velocities prevents a clean resolution of the activity
signals. Instead, both the S-index signal and the EWHα signal are pushed to
much larger and nonsensical values: 81942$\pm$190000 days for the S-index
data, and 29213$\pm$41000 days for the EWHα data. Because of this, we opt to
disregard the MCMC analyses and proceed with the signals evident in the
initial $\Delta$BIC periodograms. We take the agreement of these two activity
indicator periodogram peaks and their overlap with the RV signal (which is
well resolved) to be sufficient evidence that all three signals are
manifestations of the same underlying magnetic cycle.

Given this overlap, and the lack of a re-detection of the original 3827 day
signal in the radial velocities, we assert that the previously claimed HD
114613 b from Wittenmyer et al. (2014) is not in fact a planet, but may be
attributed to a long period magnetic cycle.

RVSearch detects two additional RV signals with period and semi-amplitude
pairings of $P_{II}=73.14\pm 0.06$ d, $K_{II}=2.54\pm 0.48$ $\rm m\,s^{-1}$
and $P_{III}=1954\pm 39$ d, $K_{III}=2.98\pm 0.52$ $\rm m\,s^{-1}$. There are
no corresponding signals in the S-index or EWHα periodograms, and so we label
each of these signals as SRC. As a subgiant star, we would expect HD 114613 to
exhibit higher levels of RV jitter (Luhn et al., 2020), which may drive some
of the scatter seen in the RV summary figure.

###  5.12 HD 115617 (61 Vir)

61 Vir (GJ 506, HD 115617, HR 5019, HIP 64924) is a G7V star (Gray et al.,
2006) at $d=8.53$ pc ($\varpi=117.1726\pm 0.1456$ mas; Gaia Collaboration et
al., 2020). The star is slightly less active than the Sun, with reported log
$R^{\prime}_{HK}$ values between -4.93 and -5.03 (e.g. Baliunas et al., 1996;
Hall et al., 2007; Isaacson & Fischer, 2010; Vogt et al., 2010; Wittenmyer et
al., 2006; Lovis et al., 2011; Brewer et al., 2016; Meunier et al., 2017).
Baliunas et al. (1996) report an average rotation period of $P_{\rm rot}$ = 29
d based on analysis of the Mt. Wilson survey data, while Lovis et al. (2011)
reported a chromospheric activity cycle of $P_{\rm cyc}$ =
$1548^{+266}_{-811}$ d and a predicted rotation period of $P_{\rm rot}$ =
$33.9\pm 3.6$ d. According to Vogt et al. (2010), 61 Vir is a three-planet
system with $P_{b}=4.21$ days, $P_{c}=38.021\pm 0.034$ days, and
$P_{d}=123.01\pm 0.55$ days.

We recover the same three planets as Vogt et al. (2010) with slightly updated
parameters: $P_{b}=4.21498\pm 0.00014$ d, $K_{b}=2.47\pm 0.11$ $\rm
m\,s^{-1}$, $e_{b}=0.033\pm 0.029$; $P_{c}=38.079\pm 0.008$ d, $K_{c}=3.56\pm
0.12$ $\rm m\,s^{-1}$, $e_{c}=0.026\pm 0.023$; $P_{d}=123.2\pm 0.2$ d,
$K_{d}=1.47\pm 0.17$ $\rm m\,s^{-1}$, $e_{d}=0.15\pm 0.11$. We report these
parameters as an improvement to the previously reported ones, due to an
additional 2473 RV observations since Vogt et al. (2010).

After analysis of residual signals, Rosenthal et al. (2021) report the 123-day
period signal as a yearly alias. We do not see similar evidence in our data as
they report, after examining an additional ten years of data. We therefore
report this signal as an update to the currently confirmed planet d.

We recover one additional RV signal, RV signal I, with parameters $P=20565\pm
21000$ d, $K=2.23\pm 0.46$ $\rm m\,s^{-1}$, and $e=0.97\pm 0.024$. The
original periodogram peak being fit by this Keplerian is at 5910.9 days, which
is close to the observation baseline, so the fit is poorly constrained. The
presence of the peak is evidence of a long-period trend which is not yet well
defined, so we classify this signal as LPS.

Analysis of the S-index activity does not yield any detections, but we note
that there is significant strength in the S-index periodogram at 3995 days.
This may be indicative of an approximately 11 year magnetic activity cycle,
but there is insufficient data to push this signal past the false alarm
probability threshold. Continued study of this target would allow for further
understanding of potential origins of this signal.

Analysis of H$\alpha$ data returns three detections. The first of these has
$P_{I}=346.3\pm 1.9$ d, which we attribute to observation cadence effects. The
second and third signals have $P_{II}=24.63\pm 0.02$ d and $P_{III}=44.932\pm
0.069$ d. The observed H$\alpha$ periodicities II and III are bit shorter and
longer, respectively, than the predicted rotation period ($P_{\rm rot}$ =
$33.9\pm 3.6$ d) from Lovis et al. (2011).

H$\alpha$ signal II is close to the rotation period reported by Baliunas et
al. (1996), though it is shorter by several days. Because the Lovis et al.
(2011) rotation period is predicted, and the Baliunas et al. (1996) $P_{\rm
rot}$ is 26 years old, we assert that it is possible that H$\alpha$ signal II
is due to stellar rotation.

H$\alpha$ signal III does not correlate with any periodicity in Ca H & K data
nor RV data, and is unlikely to be caused by differential rotation, as its
period is $\sim$20 d greater than signal II. However, we note that it is not
impossible that H$\alpha$ signal III is caused by differential rotation.
Quantifying the differential rotation in terms of
$\alpha=|P_{2}-P_{1}|/P_{max}=0.45$, this would suggest surface shear
approximately twice that of the Sun ($\alpha_{\odot}$ = 0.2; Reinhold et al.,
2013). The observed differential rotation trend for nearby solar-type stars
from Donahue et al. (1996) predicts that for a mean rotation period of
$\sim$35 days, one would predict observing $\Delta P$ $\simeq$ 7.6 d. However,
the data from Donahue et al. (1996) also show that there are cases for
rotators with $\sim$month-long periods of having $\Delta P$ as high as
$\sim$18 d! Because of this, we believe it is somewhat plausible that
H$\alpha$ signals II and III could be hinting at strong differential rotation,
but further observations would be needed to test this idea further.

###  5.13 HD 136352 ($\nu^{2}$ Lup)

$\nu^{2}$ Lup (HD 136352, GJ 582, HR 5699, HIP 75181) is a nearby G2-V (Gray
et al., 2006) star at $d=14.74$ pc ($\varpi=67.8467\pm 0.0601$ mas; Gaia
Collaboration et al., 2020). The star is similar to the Sun in temperature and
gravity, but considerably more metal poor: $T_{\rm eff}$$\,=5664\pm 14$ K,
$\log g$$\,=4.39\pm 0.02$, $[Fe/H]=-0.34\pm 0.01$ (Sousa et al., 2008). Given
its high velocity, low metallicity, and $\alpha$-element enhancement
([$\alpha$/Fe] $\simeq$ 0.17) (Soubiran & Girard, 2005), the star is widely
classified as a thick disk star (e.g. Ibukiyama & Arimoto, 2002; Soubiran &
Girard, 2005; Adibekyan et al., 2012; Hinkel et al., 2017; Kane et al.,
2020)171717The only known star brighter in $V$ and $G$ band than HD 136352
with transiting exoplanets in the NASA Exoplanet Archive is HD 219134, which
is an $\alpha$-poor thin disk star of approximately solar metallicity
(Mishenina et al., 2004; Ramírez et al., 2012). The only known star brighter
in $K_{s}$ band than HD 136352 is 55 Cnc, which is a metal-rich thin disk star
(Mishenina et al., 2004; Ramírez et al., 2012). Hence, HD 136352 ($\nu^{2}$
Lup) appears to be the brightest – either in visible or near-IR bands – thick
disk star known to have transiting exoplanets.. Lovis et al. (2011) report a
magnetic activity cycle of $P_{\rm cyc}$ = 1041${}_{-97}^{+581}$ d
($2.85^{+1.59}_{-0.27}$ yr), with a predicted rotation period of $P_{\rm rot}$
= $25.0\pm 3.1$ d based on the mean activity level (log $R^{\prime}_{HK}$ =
-4.986)181818Independently, Isaacson & Fischer (2010) predicts the rotation
period of HD 136352 to be 23 d based on log $R^{\prime}_{HK}$.. Udry et al.
(2019) reported three planet signals in _HARPS_ radial velocity observations
for HD 136352. Kane et al. (2020) present a detailed study of $\nu^{2}$ Lupi,