title: Core-collapse, GRBs, Type Ia Supernovae, and Cosmology

abstract:
  Type Ia Supernovae (SNe) have been used by many to argue for an accelerated
expansion of the universe. However, high velocity and polarized features in
many nearby SNe Ia, and their inverse relation to luminosity, particularly for
polarization, are consistent with an extreme version of the axisymmetry seen in
SN 1987A, which could be the result of double degenerate merger-induced
core-collapse. This could be the correct paradigm for many SNe Ia and Ic, where
Ia's are both thermonuclear and core-collapsed objects, which leave
weakly-magnetized, rapidly spinning (~2 ms) pulsars. In this paradigm Ia/c is
produced from the merger of two degenerate cores of common envelope WR stars,
or of two CO white dwarfs. Its polar blowouts produce the observed high
velocity and polarized spectral features in Ia's, and its equatorial bulge is
much brighter in Ia's, due to the greater fraction of 56Ni contained within it.
These become classified as Ia's when viewed from the merger equator, and Ic's
when viewed from the poles, where a hypernova signature and a gamma-ray burst
(GRB) will be observed for lines of sight close to the merger axis. Thus
cosmology determined strictly from Ia's alone may be flawed because the local
sample is selectively biased. Finally, all GRBs start as the short-duration,
hard-spectrum variety (sGRBs), after which some are modified to the
long-duration, soft-spectrum variety (lGRBs) by interaction with the merger
common envelope and previous polar ejection. Thus the initial photon spectrum
of all GRBs is known.


title: Comet 162P/Siding Spring: A Surprisingly Large Nucleus

abstract:
  We present an analysis of thermal emission from comet 162P/Siding Spring
(P/2004 TU12) measured during its discovery apparition in 2004 December. The
comet showed no dust coma at this time, so we have sampled emission from the
comet's nucleus. Observations using the Mid-Infrared Spectrometer and Imager
(MIRSI) were performed at NASA's Infrared Telescope Facility, where the peak of
the comet's spectral energy distribution was observed between 8 and 25 microns.
In combination with the three near-IR spectra presented by Campins et al.
(2006, Astron. J. 132, 1346) that show the Wien-law tail of the thermal
emission, the data provide powerful constraints on surface properties of the
nucleus. We find that the nucleus's effective radius is 6.0+/-0.8 km. This is
one of the largest radii known among Jupiter-family comets, which is unusual
considering that the comet was discovered only recently. Its geometric albedo
is 0.059+/-0.023 in the H band, 0.037+/-0.014 in the R band, and 0.034+/-0.013
in the V band. We also find that the nucleus of 162P has little IR beaming, and
this implies that the nucleus has low thermal inertia. Including all near-IR
spectra yields a beaming parameter of 1.01+/-0.20. This result is in agreement
with others showing that cometary nuclei have low thermal inertia and little IR
beaming. If confirmed for many nuclei, the interpretation of radiometry may not
be as problematic as feared.


title:
Zenith-Distance Dependence of Chromatic Shear Effect: A Limiting Factor
  for an Extreme Adaptive Optics System

abstract:
  Consider a perfect AO system with a very fine wavefront sampling interval and
a very small actuator interval. If this AO system senses wavefront at a
wavelength, lambda_{WFS}, and does science imaging at another wavelength,
lambda_{SCI}, the light paths through the turbulent atmosphere at these two
wavelengths are slightly different for a finite zenith distance, z. The error
in wavefront reconstruction of the science channel associated with this
non-common path effect, or so-called chromatic shear, is uncorrectable and sets
an upper bound of the system performance. We evaluate the wavefront variance,
sigma^2(lambda_{WFS},lambda_{SCI},z) for a typical seeing condition at Mauna
Kea and find that this effect is not negligible at a large z. If we require
that the Strehl ratio be greater than 99 or 95%, z must be less than about 50
or 60 deg respectively, for the combination of visible wavefront sensing and
infrared science imaging.


title: Blueprint for a rotating Univers

abstract:
  A solution of the vacuum Einstein equations with a cosmological constant is
exhibited which can perhaps be used to describe the interior of compact
rotating objects, and may also provide a description of our universe on length
scales approaching the size of the de Sitter horizon.


title: Phase-space distribution of unbound dark matter near the Sun

abstract:
  We resolve discrepancies in previous analyses of the flow of collisionless
dark matter particles in the Sun's gravitational field. We determine the
phase-space distribution of the flow both numerically, tracing particle
trajectories back in time, and analytically, providing a simple correct
relation between the velocity of particles at infinity and at the Earth. We use
our results to produce sky maps of the distribution of arrival directions of
dark matter particles on Earth at various times of the year. We assume various
Maxwellian velocity distributions at infinity describing the standard dark halo
and streams of dark matter. We illustrate the formation of a ring, analogous to
the Einstein ring, when the Earth is directly downstream of the Sun.


title: Microlensing of Lensed Supernovae

abstract:
  Given the number of recently discovered galaxy-galaxy lens systems, we
anticipate that a gravitationally lensed supernova will be observed within the
next few years. We explore the possibility that stars in the lens galaxy will
produce observable microlensing fluctuations in lensed supernova light curves.
For typical parameters, we predict that ~70% of lensed SNe will show
microlensing fluctuations > 0.5 mag, while ~25% will have fluctuations > 1 mag.
Thus microlensing of lensed supernova will be both ubiquitous and observable.
Additionally, we show that microlensing fluctuations will complicate
measurements of time delays from multiply imaged supernovae: time delays
accurate to better than a few days will be difficult to obtain. We also
consider prospects for extracting the lens galaxy's stellar mass fraction and
mass function from microlensing fluctuations via a new statistical measure, the
time-weighted light curve derivative.


title:
Multivariate characterization of hydrogen Balmer emission in cataclysmic
  variables

abstract:
  The ratios of hydrogen Balmer emission line intensities in cataclysmic
variables are signatures of the physical processes that produce them. To
quantify those signatures relative to classifications of cataclysmic variable
types, we applied the multivariate statistical analysis methods of principal
components analysis and discriminant function analysis to the spectroscopic
emission data set of Williams (1983). The two analysis methods reveal two
different sources of variation in the ratios of the emission lines. The source
of variation seen in the principal components analysis was shown to be
correlated with the binary orbital period. The source of variation seen in the
discriminant function analysis was shown to be correlated with the equivalent
width of the H$\beta$ line. Comparison of the data scatterplot with
scatterplots of theoretical models shows that Balmer line emission from T CrB
systems is consistent with the photoionization of a surrounding nebula.
Otherwise, models that we considered do not reproduce the wide range of Balmer
decrements, including "inverted" decrements, seen in the data.


title:
Tracing high energy radiation with molecular lines near deeply embedded
  protostars

abstract:
  Submillimeter lines of CN, NO, CO+ and SO+, and upper limits on SH+ and N2O
are observed with the James Clerk Maxwell Telescope in two high-mass and up to
nine low-mass young stellar objects and compared with chemical models. Constant
fractional abundances derived from radiative transfer modeling of the line
strengths are x(CN) ~ a few x 10^{-11}-10^{-8}, x(NO) ~ 10^{-9}-10^{-8} and
x(CO+) ~ 10^{-12}-10^{-10}. SO+ has abundances of a few x 10^{-11} in the
high-mass objects and upper limits of ~ 10^{-12}-10^{-11} in the low-mass
sources. All abundances are up to 1-2 orders of magnitude higher if the
molecular emission is assumed to originate mainly from the inner region (< 1000
AU) of the envelope. For high-mass sources, the CN, SO+ and CO+ abundances and
abundance ratios are best explained by an enhanced far-ultraviolet (FUV) field
impacting gas at temperatures of a few hundred K. The observed column densities
require that this region of enhanced FUV has scales comparable to the observing
beam, such as in a geometry in which the enhanced FUV irradiates outflow walls.
For low-mass sources, the required temperatures within the FUV models of T >
300 K are much higher than found in models, so that an X-ray enhanced region
close to the protostar (r < 500 AU) is more plausible. The observed abundances
imply X-ray fluxes for the Class 0 objects of L_X ~ 10^{29}-10^{31} erg s^{-1},
comparable to those observed from low-mass Class I protostars. Spatially
resolved data are needed to clearly distinguish the effects of FUV and X-rays
for individual species.


title:
Unveiling the nature of INTEGRAL objects through optical spectroscopy.
  V. Identification and properties of 21 southern hard X-ray sources

abstract:
  Optical spectroscopic identification of the nature of 21 unidentified
southern hard X-ray objects is reported here in the framework of our campaign
aimed at determining the nature of newly-discovered and/or unidentified sources
detected by INTEGRAL. Our results show that 5 of these objects are magnetic
Cataclysmic Variables (CVs), 4 are High-Mass X-ray Binaries (HMXBs; one of
which is in the Large Magellanic Cloud) and 12 are Active Galactic Nuclei
(AGNs). When feasible, the main physical parameters for these hard X-ray
sources are also computed using the multiwavelength information available in
the literature. These identifications further underscore the importance of
INTEGRAL in the study of the hard X-ray spectrum of AGNs, HMXBs and CVs, and
the usefulness of a strategy of catalogues cross-correlation plus optical
spectroscopy to securely pinpoint the actual nature of the X-ray sources
detected with INTEGRAL.


title:
A mid-infrared study of very low mass stars and brown dwarfs in Upper
  Scorpius

abstract:
  We report the results of mid-IR observations with VISIR at the VLT of 10
ultracool dwarfs members of the nearby Upper Scorpius OB association in four
filters ranging between 8.59 (PAH1) to 12.8 $\mu$m (Ne II), and one brown dwarf
with Spitzer between 3.6 and 24 $\mu$m. Seven of our targets are detected in at
least one of the bands, and we derive upper limits on the fluxes of the
remaining 4. These results combined with previous studies from the literature
lead to an improved disk frequency of 50$\pm$12%. This frequency is
significantly higher than that of accretors (16.3%$\pm$6.2%). Only one object
showing mid-IR excess also has H$\alpha$ emission at a level indicating that it
must be accreting. Four of the detected targets are multiple system candidates.
The observed disk frequency for sub-stellar objects in the Upper Scorpius
association is similar to that of stars, consistent with a common formation
scenario. It is also similar to the disk fractions observed in younger
clusters, suggesting that the disk lifetimes might be longer for ultracool
dwarfs than for higher-mass stars.


title:
The HARPS search for southern extra-solar planets. IX. mu Ara, a system
  with four planets

abstract:
  The mu Ara planetary system is rather complex: It contains two already known
planets, mu Ara b with P=640 days and mu Ara c with P=9.64 days, and a third
companion on a wide but still poorly defined orbit. Even with three planets in
the system, the data points keep anomalously high dispersion around the fitted
solution. The high residuals are only partially due to the strong p-mode
oscillations of the host star. We have therefore studied in this paper the
possible presence of a fourth planet in the system. During the past years we
have carried out additional and extremely precise radial-velocity measurements
with the HARPS spectrograph. We provide in this paper a full orbital solution
of the planetary system around mu Ara. It turns out to be the second system
known to harbor 4 planetary companions. Thanks to the new data points acquired
with HARPS we can confirm the presence of mu Ara c at P=9.64 days, which
produces a coherent RV signal over more than two years. The new orbital fit
sets the mass of mu Ara c to 10.5 M_Earth. Furthermore, we present the
discovery of mu Ara d, a new planet on an almost circular 310 days-period and
with a mass of 0.52 M_Jup. Finally, we give completely new orbital parameters
for the longest-period planet, mu Ara e. It is the first time that this
companion is constrained by radial-velocity data into a dynamical stable orbit,
which leaves no doubt about its planetary nature. (Abridged).


title:
The RR Lyrae Period - K Luminosity relation for Globular Clusters: an
  observational approach

abstract:
  The Period - metallicity - K band luminosity (PLK) relation for RR Lyrae
stars in 15 Galactic globular clusters and in the LMC globular cluster
Reticulum has been derived. It is based on accurate near infrared (K)
photometry combined with 2MASS and other literature data. The PLK relation has
been calibrated and compared with the previous empirical and theoretical
determinations in literature. The zero point of the absolute calibration has
been obtained from the K magnitude of RR Lyr whose distance modulus has been
measured via trigonometric parallax with HST. Using this relation we obtain a
distance modulus to the LMC of (m-M)_0 = 18.54 \pm 0.15 mag, in good agreement
with recent determinations based on the analysis of Cepheid variable stars.


title: Warping and precession in galactic and extragalactic accretion disks

abstract:
  The Bardeen-Petterson general relativistic effect has been suggested as the
mechanism responsible for precession in some accretion disk systems. Here we
examine separately four mechanisms (tidally-induced, irradiation-induced,
magnetically-induced and Bardeen-Petterson-induced) that can lead to warping
and precession. We use a sample of eight X-ray binaries and four Active
Galactic Nuclei (AGNs) that present signatures of warping and/or precession in
their accretion disks to explore the viability of the different mechanisms. For
the X-ray binaries SMC X-1 and 4U 1907+09 all four mechanisms provide
precession periods compatible with those observed, while for Cyg X-1 and the
active galaxies Arp 102B and NGC 1068, only two mechanisms are in agreement
with the observations. The irradiation-driven instability seems incapable of
producing the inferred precession of the active galaxies in our sample, and the
tidally-induced precession can probably be ruled out in the case of Arp 102B.
Perhaps the best case for a Bardeen-Petterson precession can be achieved for
NGC 1068. Our results show that given the many observational uncertainties that
still exist, it is extremely difficult to confirm unambiguously that the
Bardeen-Petterson effect has been observed in any of the other sources of our
sample.


title: Is there a problem with low energy SN1987A neutrinos?

abstract:
  (abridged) We study the low energy events observed by Kamiokande-II. We focus
on the event 6 of 6.3 MeV and also on the other events that at 1 sigma fall
below the energy threshold: events 3,4,10,12. The volume distribution is not a
uniform distribution at 3 sigma, that suggests the presence of background
events close or at the border of the volume used for the analysis, including
the events 3,4,10. We checked the expected energy distribution assuming that
the signal is due to nubar(e)p-->e+n and that the average antineutrino energy
is 14 MeV. The agreement with the observations is not perfect but it is
acceptable at the 11 % confidence level if we include the peak of low energy
background events; otherwise, we face a 2.9 sigma problem. The expected energy
distribution implies that the evidence for supernova neutrinos is at 10 sigma
and that 1-3 background events are plausible. This conclusion does not change
strongly when we model the time distribution of the signal taking into account
the presence of an initial luminous phase of neutrino emission. This suggests
however that some of the early events are due to supernova neutrinos and not to
background. In summary, we formulate the hypothesis that some of the observed
low energy events are due to background and that some among them belong to a
peculiar phase of emission, that could be further characterized by low energy
neutrinos. Such an interpretation diminishes to a minimum the postulated number
of background events and thus improves the agreement between the a priori and
the a posteriori expectations on the number of background events. We argue on
these grounds that there is no significant disagreement between the average
energy of the supernova neutrinos seen in Kamiokande-II and the conventional
expectations.


title: Modeling Eclipses of the Novalike Variable TT Triangulum

abstract:
  Multicolor (BVRI) light curves of the eclipsing novalike variable TT Tri are
presented and analyzed with a parameter-fitting eclipse model. The mass ratio
of TT Tri is poorly constrained, but must lie roughly in the range
0.3<q(=M_2/M_1)<0.9. Models characterized by mass ratios of q=0.3 (i=76.1 deg),
q=0.6 (i=72.6 deg), and q=0.9 (i=70.4 deg) were all capable of providing
acceptable fits to the data, although the best fits were achieved for mass
ratios near the upper end of the permitted range. The values of the remaining
fitting parameters were found to be insensitive to the adopted mass ratio and
rim thickness. The accretion disk was found to extend to ~50-60% of the
distance to the inner Lagrangian point in all models, but came closer to
reaching the tidal limit in the higher mass ratio models. The same behavior was
found for the radial temperature profile of the disk, which increased with mass
ratio, becoming more consistent with that expected for steady state accretion
in the q=0.6 and q=0.9 models. Models with a truncated inner disk (R_in>>R_1)
generally resulted in a higher white dwarf temperature, and a steepening of the
disk temperature profile, but were not required to achieve a viable
steady-state disk solution. No evidence was found for a luminous bright spot in
the system, which is not surprising given the lack of a pre-eclipse "hump" in
the light curve. A total of 22 eclipse timings were measured for the system,
which yielded an ephemeris for the times of mid-eclipse given by HJD =
2,453,618.953(3) + 0.1396369(4) E. A comparison of the observed brightness and
color at mid-eclipse with the photometric properties of the best-fitting model
suggests that TT Tri lies at a distance of ~400-500 pc. (abstract abridged)


title:
Cosmic ray diffusion near the Bohm limit in the Cassiopeia A supernova
  remnant

abstract:
  Supernova remnants (SNRs) are believed to be the primary location of the
acceleration of Galactic cosmic rays, via diffusive shock (Fermi) acceleration.
Despite considerable theoretical work the precise details are still unknown, in
part because of the difficulty in directly observing nucleons that are
accelerated to TeV energies in, and affect the structure of, the SNR shocks.
However, for the last ten years, X-ray observatories ASCA, and more recently
Chandra, XMM-Newton, and Suzaku have made it possible to image the synchrotron
emission at keV energies produced by cosmic-ray electrons accelerated in the
SNR shocks. In this article, we describe a spatially-resolved spectroscopic
analysis of Chandra observations of the Galactic SNR Cassiopeia A to map the
cutoff frequencies of electrons accelerated in the forward shock. We set upper
limits on the electron diffusion coefficient and find locations where particles
appear to be accelerated nearly as fast as theoretically possible (the Bohm
limit).


title:
Growing hydrodynamic modes in Keplerian accretion disks during secondary
  perturbations: Elliptical vortex effects

abstract:
  The origin of hydrodynamic turbulence, and in particular of an anomalously
enhanced angular momentum transport, in accretion disks is still an unsolved
problem. This is especially important for cold disk systems which are
practically neutral in charge and therefore turbulence can not be of
magnetohydrodynamic origin. While the flow must exhibit some instability and
then turbulence in support of the transfer of mass inward and angular momentum
outward, according to the linear perturbation theory, in absence of
magnetohydrodynamic effects, it should always be stable. We demonstrate that
the three-dimensional secondary disturbance to the primarily perturbed disk,
consisting of elliptical vortices, gives significantly large hydrodynamic
growth in such a system and hence may suggest a transition to an ultimately
turbulent state. This result is essentially applicable to accretion disks
around quiescent cataclysmic variables, in proto-planetary and star-forming
disks, the outer region of disks in active galactic nuclei, where the gas is
significantly cold and thus the magnetic Reynolds number is smaller than 10^4.

categories: astro-ph cond-mat.other cond-mat.soft physics.flu-dyn


title: Mapping Luminosity-Redshift Relationship to LTB Cosmology

abstract:
  We derive a direct general map from the luminosity distance D(z) to the
inhomogeneous matter distribution M(r) in the Lemaitre-Tolman-Bondi (LTB)
cosmology and compute several examples. One of our examples explicitly
demonstrates that it is possible to tune the LTB cosmological solution to
approximately reproduce the luminosity distance curve of a flat FRW universe
with a cosmological constant. We also discuss how smooth matter distributions
can evolve into naked singularities due to shell crossing when the
inhomogeneous ``spatial curvature'' E(r) is a function which changes sign.


title: An unusual precursor burst with oscillations from SAX J1808.4-3658

abstract:
  We report the finding of an unusual, weak precursor to a thermonuclear X-ray
burst from the accreting millisecond pulsar SAX J1808.4-3658. The burst in
question was observed on Oct. 19, 2002 with the Rossi X-Ray Timing Explorer
(RXTE) proportional counter array (PCA). The precursor began approximately 1 s
prior to the onset of a strong radius expansion burst, lasted for about 0.4 s,
and exhibited strong oscillations at the 401 Hz spin frequency. Oscillations
are not detected in the approximately 0.5 s interval between the precursor and
the main burst. The estimated peak photon flux and energy fluence of the
precursor are about 1/25, and 1/500 that of the main burst, respectively. From
joint spectral and temporal modeling, we find that an expanding burning region
with a relatively low temperature on the spinning neutron star surface can
explain the oscillations, as well as the faintness of the precursor with
respect to the main part of the burst. We dicuss some of the implications of
our findings for the ignition and spreading of thermonuclear flames on neutron
stars.


title: CMB Anomalies from Relic Anisotropy

abstract:
  Most of the analysis of the Cosmic Microwave Background relies on the
assumption of statistical isotropy. However, given some recent evidence
pointing against isotropy, as for instance the observed alignment of different
multipoles on large scales, it is worth testing this assumption against the
increasing amount of available data. As a pivot model, we assume that the
spectrum of the primordial perturbations depends also on their directionality
(rather than just on the magnitude of their momentum, as in the standard case).
We explicitly compute the correlation matrix for the temperature anisotropies
in the simpler case in which there is a residual isotropy between two spatial
directions. As a concrete example, we consider a different initial expansion
rate along one direction, and the following isotropization which takes place
during inflation. Depending on the amount of inflation, this can lead to broken
statistical isotropy on the largest observable scales.


title:
The Mass of the Black Hole in the Seyfert 1 Galaxy NGC 4593 from
  Reverberation Mapping

abstract:
  We present new observations leading to an improved black hole mass estimate
for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign
conducted at the MDM Observatory. Cross-correlation analysis of the H_beta
emission-line light curve with the optical continuum light curve reveals an
emission-line time delay of 3.73 (+-0.75) days. By combining this time delay
with the H_beta line width, we derive a central black hole mass of M_BH =
9.8(+-2.1)x10^6 M_sun, an improvement in precision of a factor of several over
past results.


title: A direct empirical proof of the existence of dark matter

abstract:
  We present new weak lensing observations of 1E0657-558 (z=0.296), a unique
cluster merger, that enable a direct detection of dark matter, independent of
assumptions regarding the nature of the gravitational force law. Due to the
collision of two clusters, the dissipationless stellar component and the
fluid-like X-ray emitting plasma are spatially segregated. By using both
wide-field ground based images and HST/ACS images of the cluster cores, we
create gravitational lensing maps which show that the gravitational potential
does not trace the plasma distribution, the dominant baryonic mass component,
but rather approximately traces the distribution of galaxies. An 8-sigma
significance spatial offset of the center of the total mass from the center of
the baryonic mass peaks cannot be explained with an alteration of the
gravitational force law, and thus proves that the majority of the matter in the
system is unseen.


title:
Strong and weak lensing united III: Measuring the mass distribution of
  the merging galaxy cluster 1E0657-56

abstract:
  The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for
addressing outstanding issues in both galaxy evolution and fundamental physics.
We present a reconstruction of the mass distribution from both strong and weak
gravitational lensing data. Multi-color, high-resolution HST ACS images allow
detection of many more arc candidates than were previously known, especially
around the subcluster. Using the known redshift of one of the multiply imaged
systems, we determine the remaining source redshifts using the predictive power
of the strong lens model. Combining this information with shape measurements of
"weakly" lensed sources, we derive a high-resolution, absolutely-calibrated
mass map, using no assumptions regarding the physical properties of the
underlying cluster potential. This map provides the best available
quantification of the total mass of the central part of the cluster. We also
confirm the result from Clowe et al. (2004,2006a).


title: Multicolour CCD photometry of the variable stars in globular cluster M3

abstract:
  We present time series data on the variable stars of the galactic globular
cluster Messier 3 (M3). We give BVI light curves for 226 RR Lyrae, 2 SX Phe and
1 W Vir type variables, along with estimated fundamental photometric parameters
such as intensity and magnitude-averaged brightness and pulsation periods. In
some cases the periods we have found significantly differ from the previously
published ones. This is the first published light curve and period
determination for variable V266. The I-band light curve has not been observed
previously for numerous (76) variables. Three new RR Lyrae variables have been
discovered. Groups of RR Lyrae variables that belong to different evolutionary
stages and have been separated previously on the basis of V data were found
here for all colours and colour indices by cluster analysis. The I-band period
-- luminosity relation is also discussed. From the 66 modulated (Blazhko type)
RR Lyrae stars we investigated, six are newly identified and two of them are
first overtone pulsators. In the case of 13 RR Lyrae, the period of Blazhko
cycle has been estimated for the first time. V252 is identified as a new RRd
variable. Amplitude ratio of RRd stars have been investigated to search
possible mode content changes. In contrast to previous publications no changes
have been found. Problems with the sampling of the time series of typical
cluster variability surveys is demonstrated.


title: Measuring Chemical Abundances in Extragalactic Metal-Rich HII Regions

abstract:
  The analysis of metal-rich HII regions has a profound impact on the
calibration of abundance diagnostics widely used to measure the chemical
content of star-forming galaxies, both locally and at high redshift. I review
the main difficulties that affect direct abundance determinations from
temperature-sensitive collisionally excited lines, and briefly discuss
strong-line methods, in particular their empirical calibration. In the near
future it will be possible to calibrate strong-line methods using metal
recombination lines, providing abundances that are virtually insensitive to
uncertainties on the nebular temperature structure.


title:
Radioactive Probes of the Supernova-Contaminated Solar Nebula: Evidence
  that the Sun was Born in a Cluster

abstract:
  We construct a simple model for radioisotopic enrichment of the protosolar
nebula by injection from a nearby supernova, based on the inverse square law
for ejecta dispersion. We find that the presolar radioisotopes abundances
(i.e., in solar masses) demand a nearby supernova: its distance can be no
larger than 66 times the size of the protosolar nebula, at a 90% confidence
level, assuming 1 solar mass of protosolar material. The relevant size of the
nebula depends on its state of evolution at the time of radioactivity
injection. In one scenario, a collection of low-mass stars, including our sun,
formed in a group or cluster with an intermediate- to high-mass star that ended
its life as a supernova while our sun was still a protostar, a starless core,
or perhaps a diffuse cloud. Using recent observations of protostars to estimate
the size of the protosolar nebula constrains the distance of the supernova at
0.02 to 1.6 pc. The supernova distance limit is consistent with the scales of
low-mass stars formation around one or more massive stars, but it is closer
than expected were the sun formed in an isolated, solitary state. Consequently,
if any presolar radioactivities originated via supernova injection, we must
conclude that our sun was a member of such a group or cluster that has since
dispersed, and thus that solar system formation should be understood in this
context. In addition, we show that the timescale from explosion to the creation
of small bodies was on the order of 1.8 Myr (formal 90% confidence range of 0
to 2.2 Myr), and thus the temporal choreography from supernova ejecta to
meteorites is important. Finally, we can not distinguish between progenitor
masses from 15 to 25 solar masses in the nucleosynthesis models; however, the
20 solar mass model is somewhat preferred.


title:
Effect of charge on negative-phase-velocity propagation of
  electromagnetic waves in the ergosphere of a rotating black hole

abstract:
  The presence of charge promotes the propensity of a rotating black hole to
support the propagation of electromagnetic plane waves with negative phase
velocity (NPV) in its ergosphere, whether the Kerr-Newman or the Kerr-Sen
metric descriptions of spacetime are considered. Striking differences in the
NPV characteristics for the Kerr-Newman and Kerr-Sen metrics emerge from
numerical studies, particularly close to the outer event horizon when the
magnitude of the charge is large.


title: Destiny: A Candidate Architecture for the Joint Dark Energy Mission

abstract:
  Destiny is a simple, direct, low cost mission to determine the properties of
dark energy by obtaining a cosmologically deep supernova (SN) type Ia Hubble
diagram. Operated at L2, its science instrument is a 1.65m space telescope,
featuring a grism-fed near-infrared (NIR) (0.85-1.7micron) survey
camera/spectrometer with a 0.12 square degree field of view. During its
two-year primary mission, Destiny will detect, observe, and characterize ~3000
SN Ia events over the redshift interval 0.4<z<1.7 within a 3 square degree
survey area. In conjunction with ongoing ground-based SN Ia surveys for z<0.8,
Destiny mission data will be used to construct a high-precision Hubble diagram
and thereby constrain the dark energy equation of state from a time when it was
strongly matter-dominated to the present when dark energy dominates. The
grism-images simultaneously provide broad-band photometry, redshifts, and SN
classification, as well as time-resolved diagnostic data for investigating
additional SN luminosity diagnostics. Destiny will be used in its third year as
a high resolution, wide-field imager to conduct a multicolor NIR weak lensing
(WL) survey covering 1000 square degrees. The large-scale mass power spectrum
derived from weak lensing distortions of field galaxies as a function of
redshift will provide independent and complementary constraints on the dark
energy equation of state. The combination of SN and WL is much more powerful
than either technique on its own. Used together, these surveys will have more
than an order of magnitude greater sensitivity than will be provided by ongoing
ground-based projects. The dark energy parameters, w_0 and w_a, will be
measured to a precision of 0.05 and 0.2 respectively.


title: GRBs with the Swift satellite

abstract:
  I touch upon some of the discoveries made by the Swift Team during the first
18 months of operation focusing on a few critical points. In addition to the
early afterglows and complete coverage of the light curves, we mention the
discovery of the location of Short bursts, the statistics on flares that is
under completion and refer to their explanation as due to internal shocks. The
full understanding of the connection with supernovae and the study of high z
flares will ultimately lead to the detailed understanding of the mechanism of
explosion both for GRBs and for Supernovae.


title: General Relativistic Self-Similar Solutions in Cosmology

abstract:
  We present general relativistic solutions for self-similar spherical
perturbations in an expanding cosmological background of cold pressure-less
gas. We focus on solutions having shock discontinuities propagating in the
surrounding cold gas. The pressure, $p$, and energy-density, $\mu$, in the
shock-heated matter are assumed to obey $p=w\mu$, where $w$ is a positive
constant. Consistent solutions are found for shocks propagating from the
symmetry center of a region of a positive density excess over the background.
In these solutions, shocks exist outside the radius marking the event horizon
of the black hole which would be present in a shock-less collapse. For large
jumps in the energy-density at the shock, a black hole is avoided altogether
and the solutions are regular at the center. The shock-heated gas does not
contain any sonic points, provided the motion of the cold gas ahead of the
shock deviates significantly from the Hubble flow. For shocks propagating in
the uniform background, sonic points always appear for small jumps in the
energy-density. We also discuss self-similar solutions without shocks in fluids
with $w<-1/3$.


title: Iron in Hot DA White Dwarfs

abstract:
  We present a study of the iron abundance pattern in hot hydrogen-rich (DA)
white dwarfs. The study is based on new and archival far ultraviolet
spectroscopy of a sample of white dwarfs in the temperature range 30,000 K <
T_eff < 64,000 K. The spectra obtained with the Far Ultraviolet Spectroscopic
Explorer along with spectra obtained with the Hubble Space Telescope Imaging
Spectrograph and the International Ultraviolet Explorer sample FeIII to FeVI
absorption lines enabling a detailed iron abundance analysis over a wider range
of effective temperatures than previously afforded. The measurements reveal
abundance variations in excess of two orders of magnitude between the highest
and the lowest temperatures probed, but also show considerable variations (over
one order of magnitude) between objects with similar temperatures and surface
gravities. Such variations in cooler objects may be imputed to accretion from
unseen companions or so-called circumstellar debris although the effect of
residual mass-loss and selective radiation pressure in the hottest objects in
the sample remain dominant.


title: Planetesimals To Brown Dwarfs: What is a Planet?

abstract:
  The past 15 years have brought about a revolution in our understanding of our
Solar System and other planetary systems. During this time, discoveries include
the first Kuiper Belt Objects, the first brown dwarfs, and the first
extra-solar planets. Although discoveries continue apace, they have called into
question our previous perspectives on planets, both here and elsewhere. The
result has been a debate about the meaning of the word ''planet'' itself. It
became clear that scientists do not have a widely accepted or clear definition
of what a planet is, and both scientists and the public are confused (and
sometimes annoyed) by its use in various contexts. Because ''planet'' is a very
widely used term, it seems worth the attempt to resolve this problem. In this
essay, we try to cover all the issues that have come to the fore, and bring
clarity (if not resolution) to the debate.


title:
Hard X-ray luminosity function and absorption distribution of nearby
  AGN: INTEGRAL all-sky survey

abstract:
  We use the INTEGRAL all-sky hard X-ray survey to perform a statistical study
of a representative sample of nearby AGN. Our entire all-sky sample consists of
127 AGN, of which 91 are confidently detected (>5 sigma) on the time-averaged
map obtained with the IBIS/ISGRI instrument and 36 are detected only during
single observations. Among the former there are 66 non-blazar AGN located at
|b|>5 deg, where the survey's identification completeness is ~93%, which we use
for calculating the AGN luminosity function and X-ray absorption distribution.
In broad agreement with previous studies, we find that the fraction of obscured
(log NH>22) objects is much higher (~70%) among the low-luminosity AGN
(Lx<10^43.6 erg/s) than among the high-luminosity ones (Lx>10^43.6 erg/s),
\~25%, where Lx is the luminosity in the 17-60 keV energy band. We also find
that locally the fraction of Compton-thick AGN is less than 20% unless there is
a significant population of AGN that are so strongly obscured that their
observed hard
  X-ray luminosities fall below 10^40-10^41 erg/s, the effective limit of our
survey. The constructed hard X-ray luminosity function has a canonical,
smoothly broken power-law shape in the range 40<log Lx<45.5 with a
characteristic luminosity of log L*=43.40+/-0.28. The estimated local
luminosity density due to AGN with log Lx>40 is (1.4+/-0.3) 10^39 erg/s/Mpc^3
(17-60 keV). We demonstrate that the spectral shape and amplitude of the CXB
are consistent with the simple scenario in which the NH distribution of AGN
(for a given
  Lx/L*(z) ratio has not changed significantly since z~1.5, while the AGN
luminosity function has experienced pure luminosity evolution.


title:
The Chandra, HST, and VLA View of the Circumnuclear Extended Emission in
  the Narrow Emission Line Galaxy NGC 2110

abstract:
  We present results from new Chandra and archival HST and VLA imaging
observations of the circumnuclear extended emission in the nearby Type 2
Seyfert galaxy NGC 2110. We find resolved soft-band X-ray emission 4'' (~160
pc) north of the nucleus, which is spatially coincident with [OIII] emission,
but lies just beyond the northern edge of the radio jet in the source. We find
that shock-heating of multi-phase gas clouds can successfully account for this
extended emission, although we cannot rule out alternative models, such as the
scattering of nuclear radiation by ionized material, or pure photoionization
from the nucleus. In addition, we detect kpc-scale (~30'') extended soft-band
X-ray emission south of the nucleus. Finally, we compare our results for NGC
2110 with the prototypical Type 2 Seyfert galaxy NGC 1068, and suggest that
different physical processes could produce extended circumnuclear X-ray
emission in Seyfert galaxies.


title: X-ray Variability in the Young Massive Triple theta2 Ori A

abstract:
  Massive stars rarely show intrinsic X-ray variability. The only O-stars
credited to be intrinsically variable are theta1 Ori C due to effects from
magnetic confinement of its wind, and theta2 Ori A suspected of similar
activity. Early Chandra observations have shown that the most massive star
system in the Orion Trapezium Cluster, theta2 Ori A, shows rapid variability on
time scales of hours. We determine X-ray fluxes and find that the star shows
very strong variability over the last 5 years. We observed a second large X-ray
outburst in November 2004 with the high resolution transmission grating
spectrometer on-board Chandra. In the low state X-ray emissivities indicate
temperatures well above 25 MK. In the high state we find an extended emissivity
distribution with high emissivities in the range from 3 MK to over 100 MK. The
outburst event in stellar terms is one of the most powerful ever observed and
the most energetic one in the ONC with a lower total energy limit of 1.5x10^37
ergs. The line diagnostics show that under the assumption that the line
emitting regions in the low states are as close as within 1 -- 2 stellar radii
from the O-star's photosphere, whereas the hard states suggest a distance of 3
-- 5 stellar radii. The two outbursts are very close to the periastron passage
of the stars. We argue that the high X-ray states are possibly the result of
reconnection events from magnetic interactions of the primary and secondary
stars of the spectroscopic binary. Effects from wind collisions seem unlikely
for this system. The low state emissivity and R-ratios strengthen the
predicament that the X-ray emission is enhanced by magnetic confinement of the
primary wind. We also detect Fe fluorescence indicative of the existence of
substantial amounts of neutral Fe in the vicinity of the X-ray emission.


title:
The One-dimensional Fourier Representation and Large Angular Scale
  Foreground Contamination in the 3-year Wilkinson Microwave Anisotropy Probe
  data

abstract:
  We employ the one-dimensional Fourier representation (1DFR) to analyze the
3-year WMAP de-biased internal linear combination (DILC) map and its possible
contamination by galactic foregrounds. The 1DFR is a representation of the
spherical harmonic coefficients for each l mode using an inverse Fourier
transform into one-dimensional curves. Based on the a priori assumption that
the CMB signal should be statistically independent of, and consequently have no
significant correlation with, any foregrounds, we cross-correlate the 1DFR
curves of 2 <= l <= 10 modes, which are claimed by the WMAP team to be free of
contamination and suitable for whole sky analysis. We find that 8 out of the 9
modes are negatively cross correlated with the foreground maps, an event which
has a probability of only 9/512 ~ 0.0176 for uncorrelated signals. Furthermore,
the local extrema of the 1DFR curves between the DILC and those of the
foregrounds for l=2 and 6 are correlated with significance level below 0.04. We
also discuss the minimum variance optimization method and use the properties of
the measured cross-correlation to estimate the possible level of contamination
present in the DILC map.


title: CANGAROO-III Observations of the supernova remnant RX J0852.0$-$4622

abstract:
  Sub-TeV gamma-ray emission from the North-West rim of the supernova remnant
RX J0852.0$-$4622 was detected with the CANGAROO-II telescope and recently
confirmed by the H.E.S.S. group. In addition, the H.E.S.S. data revealed a very
wide (up to two degrees in diameter), shell-like profile of the gamma-ray
emission. We have carried out CANGAROO-III observations in January and February
2005 with three telescopes and show here the results of three-fold coincidence
data. We confirm the H.E.S.S. results about the morphology and the energy
spectrum, and find the energy spectrum in the NW-rim is consistent with that of
the whole remnant.


title:
A statistically-selected Chandra sample of 20 galaxy clusters -- I.
  Temperature and cooling time profiles

abstract:
  We present an analysis of 20 galaxy clusters observed with the Chandra X-ray
satellite, focussing on the temperature structure of the intracluster medium
and the cooling time of the gas. Our sample is drawn from a flux-limited
catalogue but excludes the Fornax, Coma and Centaurus clusters, owing to their
large angular size compared to the Chandra field-of-view. We describe a
quantitative measure of the impact of central cooling, and find that the sample
comprises 9 clusters possessing cool cores and 11 without. The properties of
these two types differ markedly, but there is a high degree of uniformity
amongst the cool core clusters, which obey a nearly universal radial scaling in
temperature of the form T \propto r^~0.4, within the core. This uniformity
persists in the gas cooling time, which varies more strongly with radius in
cool core clusters (t_cool \propto r^~1.3), reaching t_cool <1Gyr in all cases,
although surprisingly low central cooling times (<5Gyr) are found in many of
the non-cool core systems. The scatter between the cooling time profiles of all
the clusters is found to be remarkably small, implying a universal form for the
cooling time of gas at a given physical radius in virialized systems, in
agreement with recent previous work. Our results favour cluster merging as the
primary factor in preventing the formation of cool cores.


title: Accessing the innermost regions of Active Galactic Nuclei

abstract:
  Very-long-baseline interferometry can image the parsec-scale structure of
radio jets, but the accretion disk close to the black hole remains invisible.
One way to probe this accretion flow is provided by X-ray flux density
monitoring and spectroscopy. Here we report on preliminary results of a
multi-band campaign on NGC1052 with the goal of combining both approaches to
access to the innermost regions of this active galaxy and to establish a
connection between the relativistic jets and the accretion region.


title: Radiative pressure feedback by a quasar in a galactic bulge

abstract:
  We show that Eddington-limited black hole luminosities can be sufficient to
deplete a galaxy bulge of gas through radiation pressure, when the ionization
state of the gas and the presence of dust are properly taken into account. Once
feedback starts to be effective it can consistently drive all the gas out of
the whole galaxy. We estimate the amount by which the effect of radiation
pressure on dusty gas boosts the mass involved in the Eddington limit and
discuss the expected column density at which the gas is ejected. An example is
shown of the predicted observed nuclear spectrum of the system at the end of an
early, obscured phase of growth when the remaining column density NH ~ f * 1e24
cm^-2 where f is the gas fraction in the bulge.


title:
Asymmetry of $^{56}$Ni ejecta and polarization in type IIP supernova
  2004dj

abstract:
  I study a problem, whether the asymmetry of a $^{56}$Ni ejecta that results
in the asymmetry of the H$\alpha$ emission line at the nebular epoch of the
type IIP supernova SN 2004dj is able also to account for the recently detected
polarization of the supernova radiation. I developed a model of the H$\alpha$
profile and luminosity with a nonthermal ionization and excitation taken into
account adopting an asymmetric bipolar $^{56}$Ni distribution. On the
background of the recovered distribution of the electron density I calculated
the polarized radiation transfer. It is demonstrated that the observed
polarization is reproduced at the nebular epoch around day 140 for the same
parameters of the envelope and $^{56}$Ni distribution for which the luminosity
and profile of H$\alpha$ are explained.


title: Pinwheels in the Quintuplet Cluster

abstract:
  The five enigmatic Cocoon stars after which the Quintuplet cluster was
christened have puzzled astronomers since their discovery. Their extraordinary
cool, featureless thermal spectra have been attributed to various stellar types
from young to highly evolved, while their absolute luminosities places them
among the supergiants. We present diffraction-limited images from the Keck 1
telescope which resolves this debate with the discovery of rotating spiral
plumes characteristic of colliding-wind binary "pinwheel" nebulae. Such elegant
spiral structures, found around high-luminosity Wolf-Rayet stars, have recently
been implicated in the behavior of supernovae lightcurves in the radio and
optical.


title: Extremely red objects in the UKIDSS Ultra Deep Survey Early Data Release

abstract:
  We construct a sample of extremely red objects (EROs) within the UKIDSS Ultra
Deep Survey by combining the Early Data Release with optical data from the
Subaru/XMM-Newton Deep Field. We find a total of 3715 objects over 2013 sq.
arcmin with R-K>5.3 and K<=20.3, which is a higher surface density than found
by previous studies. This is partly due to our ability to use a small aperture
in which to measure colours, but is also the result of a genuine overdensity of
objects compared to other fields. We separate our sample into
passively-evolving and dusty star-forming galaxies using their RJK colours and
investigate their radio properties using a deep radio map. The dusty population
has a higher fraction of individually-detected radio sources and a higher mean
radio flux density among the undetected objects, but the passive population has
a higher fraction of bright radio sources, suggesting that AGNs are more
prevalent among the passive ERO population.


title:
An Exact, Three-Dimensional, Time-Dependent Wave Solution in Local
  Keplerian Flow

abstract:
  We present an exact three-dimensional wave solution to the shearing sheet
equations of motion. The existence of this solution argues against transient
amplification as a route to turbulence in unmagnetized disks. Moreover, because
the solution covers an extensive dynamical range in wavenumber space, it is an
excellent test of the dissipative properties of numerical codes.


title: Distance estimate and progenitor characteristics of SN 2005cs in M51

abstract:
  Distance to the Whirlpool Galaxy (M51, NGC 5194) is estimated using published
photometry and spectroscopy of the Type II-P supernova SN 2005cs. Both the
Expanding Photosphere Method (EPM) and the Standard Candle Method (SCM),
suitable for SNe II-P, were applied. The average distance (7.1 \pm 1.2 Mpc) is
in good agreement with earlier SBF- and PNLF-based distances, but slightly
longer than the distance obtained by Baron et al. for SN 1994I via the Spectral
Fitting Expanding Atmosphere Method (SEAM). Since SN 2005cs exhibited low
expansion velocity during the plateau phase, similarly to SN 1999br, the
constants of SCM were re-calibrated including the data of SN 2005cs as well.
The new relation is better constrained in the low velocity regime (v_{ph}(50) ~
1500 - 2000$ km/s), that may result in better distance estimates for such SNe.
The physical parameters of SN 2005cs and its progenitor are re-evaluated based
on the updated distance. All the available data support the low-mass (~ 9
M_\odot) progenitor scenario proposed previously by its direct detection with
the Hubble Space Telescope.


title: On the dynamics of radiative zones in rotating stars

abstract:
  In this lecture I try to explain the basic dynamical processes at work in a
radiative zone of a rotating star. In particular, the notion of baroclinicity
is thoroughly discussed. Attention is specially directed to the case of
circulations and the key role of angular momentum conservation is stressed. The
specific part played by viscosity is also explained. The old approach of
Eddington and Sweet is reviewed and criticized in the light of the seminal
papers of Busse 1981 and Zahn 1992. Other examples taken in the recent
literature are also presented; finally, I summarize the important points.


title:
Photometric and spectroscopic evolution of the type IIP supernova SN
  2004et

abstract:
  We present optical photometry and spectroscopy of the type IIP supernova SN
2004et that occurred in the nearby galaxy NGC 6946. The observations span a
time range of 8 days to 541 days after explosion. The late time bolometric
luminosity and the H$\alpha$ luminosity in the nebular phase indicate that
$0.06\pm0.02{M_\odot}$ of $^{56}$Ni was synthesised during the explosion. The
plateau luminosity, its duration and the expansion velocity of the supernova at
the middle of the plateau indicate an explosion energy of $E_{\rm{exp}}=
1.20^{+0.38}_{-0.30} \times 10^{51}$ ergs. The late time light curve and the
evolution of the [OI] and H$\alpha$ emission line profiles indicate the
possibility of an early dust formation in the supernova ejecta.
  The luminosity of [OI] 6300, 6364 \AA doublet, before the dust formation
phase, is found to be comparable to that of SN 1987A at similar epochs, impling
an oxygen mass in the range $1.5 - 2{M_\odot}$, and a main sequence mass of
$20{M_\odot}$ for the progenitor.


title: The intracluster magnetic field power spectrum in Abell 2255

abstract:
  The goal of this work is to constrain the strength and structure of the
magnetic field in the nearby cluster of galaxies A2255. At radio wavelengths
A2255 is characterized by the presence of a polarized radio halo at the cluster
center, a relic source at the cluster periphery, and several embedded radio
galaxies. The polarized radio emission from all these sources is modified by
Faraday rotation as it traverses the magnetized intra-cluster medium. The
distribution of Faraday rotation can be used to probe the magnetic field
strength and topology in the cluster. For this purpose, we performed Very Large
Array observations at 3.6 and 6 cm of four polarized radio galaxies embedded in
A2255, obtaining detailed rotation measure images for three of them. We
analyzed these data together with the very deep radio halo image recently
obtained by us. We simulated random 3-dimensional magnetic field models
characterized by different power spectra and produced synthetic rotation
measure and radio halo images. By comparing the simulations with the data we
are able to determine the strength and the power spectrum of the intra-cluster
magnetic field fluctuations which best reproduce the observations. The data
require a steepening of the power spectrum spectral index from n=2, at the
cluster center, up to n=4, at the cluster periphery and the presence of
filamentary structures on large scales. The average magnetic field strength at
the cluster center is 2.5 muG. The field strength declines from the cluster
center outward with an average magnetic field strength calculated over 1 Mpc^3
of about 1.2 muG.


title:
The precession of Mercury and the deflection of starlight by special
  relativity alone

abstract:
  I show that the precession of the orbit of Mercury and the deflection of
starlight by the Sun are effects of special relativity alone when the
gravitational field of a particle is treated in the same way as the electric
field of a charged particle . General relativity is not needed to explain them.


title: Radio evidence on the mass loss bi-stability jump

abstract:
  We present the results of a first campaign of radio continuum observations
toward supergiants with spectral types in the range O8 - B3. Three targets out
of twelve were detected with the ATCA and the VLA. The measured fluxes and the
upper limits yielded values of the stellar mass-loss rates dM/dt and the wind
efficiencies. The comparison of predicted and derived values of dM/dt shows a
good agreement.


title: The Chemical Evolution of Helium

abstract:
  We report on measurements of the 4He abundance toward the outer Galaxy HII
region S206 with the NRAO Green Bank telescope. Observations of hydrogen and
helium radio recombination lines between 8-10 GHz were made toward the peak
radio continuum position in S206. We derive 4He/H = 0.08459 +/- 0.00088
(random) +/- 0.0010 (known systematic), 20% lower than optical recombination
line results. It is difficult to reconcile the large discrepancy between the
optical and radio values even when accounting for temperature, density, and
ionization structure or for optical extinction by dust. Using only M17 and S206
we determine dY/dZ = 1.41 +/- 0.62 in the Galaxy, consistent with standard
chemical evolution models. High helium abundances in the old stellar population
of elliptical galaxies can help explain the increase in UV emission with
shorter wavelength between 2000 and 1200 Angstrom, called the UV-upturn or UVX.
Our lower values of dY/dZ are consistent with a normal helium abundance at
higher metallicity and suggest that other factors, such as a variable red giant
branch mass-loss with metallicity, may be important. When combined with 4He
abundances in metal poor galaxy HII regions, Magellanic cloud HII regions, and
M17 that have been determined from optical recombination lines including the
effects of temperature fluctuations, our radio 4He/H abundance ratio for S206
is consistent with a helium evolution of dY/dZ = 1.6. A linear extrapolation to
zero metallicity predicts a 4He/H primordial abundance ratio about 5% lower
than that given by the Wilkinson Microwave Anisotropy Probe and standard Big
Bang nucleosynthesis. The measured 4He abundances may be systematically
underestimated by a few percent if clumping exists in these HII regions.


title: Time resolved spectroscopy of GRB 021004 reveals a clumpy extended wind

abstract:
  High resolution spectroscopy of GRB 021004 revealed a wealth of absorption
lines from several intermediate ionization species. The velocity structure of
the absorber is complex and material with velocity up to >3000 km/s is
observed. Since only the blueshifted component is observed, the absorber is
very likely to be material closely surrounding the gamma-ray burst. We use a
time-dependent photoionization code to track the abundance of the ions over
time. Thanks to the presence of absorption from intermediate ionization states
at long times, we can estimate the location and mass of the components of the
absorber. We interpret those constraints within the hypernova scenario showing
that the mass loss rate of the progenitor must have been ~10^{-4} solar masses
per year, suggestive of a very massive star. In addition, the wind termination
shock must lie at a distance of at least 100 pc, implying a low density
environment. The velocity structure of the absorber also requires clumping of
the wind at those large distances.


title:
Variability in red supergiant stars: pulsations, long secondary periods
  and convection noise

abstract:
  We study the brightness variations of galactic red supergiant stars using
long-term visual light curves collected by the American Association of Variable
Star Observers (AAVSO) over the last century. The full sample contains 48 red
semiregular or irregular variable stars, with a mean time-span of observations
of 61 years. We determine periods and period variability from analyses of power
density spectra and time-frequency distributions. We find two significant
periods in 18 stars. Most of these periods fall into two distinct groups,
ranging from a few hundred to a few thousand days. Theoretical models imply
fundamental, first and possibly second overtone mode pulsations for the shorter
periods. Periods greater than 1000 days form a parallel period-luminosity
relation that is similar to the Long Secondary Periods of the Asymptotic Giant
Branch stars. A number of individual power spectra shows a single mode resolved
into multiple peaks under a Lorentzian envelope, which we interpret as evidence
for stochastic oscillations, presumably caused by the interplay of convection
and pulsations. We find a strong 1/f noise component in the power spectra that
is remarkably similar in almost all stars of the sample. This behaviour fits
the picture of irregular photometric variability caused by large convection
cells, analogous to the granulation background seen in the Sun.


title: Scalar-field-dominated cosmology with a transient accelerating phase

abstract:
  A new cosmological scenario driven by a slow rolling homogeneous scalar field
whose exponential potential $V(\Phi)$ has a quadratic dependence on the field
$\Phi$ in addition to the standard linear term is discussed. The derived
equation of state for the field predicts a transient accelerating phase, in
which the Universe was decelerated in the past, began to accelerate at redshift
$z \sim 1$, is currently accelerated, but, finally, will return to a
decelerating phase in the future. This overall dynamic behavior is profoundly
different from the standard $\Lambda$CDM evolution, and may alliviate some
conflicts in reconciling the idea of a dark energy-dominated universe with
observables in String/M-theory. The theoretical predictions for the present
transient scalar field plus dark matter dominated stage are confronted with
cosmological observations in order to test the viability of the scenario.


title:
The Calibration of the O/H Abundance Indicators for Extragalactic H II
  Regions Based on O II Recombination Lines

abstract:
  Based on O II recombination lines we present a new calibration (called O
II[RL]) of Pagel's O23 indicator to determine the O/H abundance ratio in
extragalactic H II regions and emission line galaxies. The O II(RL) calibration
produces O/H abundances about a factor of two higher than those derived from
the T(4363) method with t2 = 0.00. The O II(RL) calibration has implications
for the study of different properties of emission line galaxies such as their
metallicity, star formation rate, and initial mass function. The O II(RL)
calibration also affects the abundance determinations based on other O/H
indicators, that include collisionally excited lines, like those known as O3N2,
N2, S23, Ar3O3, and S3O3. We argue that the controversy between the T(4363)
method and the photoionization models method to derive O/H values is mainly due
to temperature variations inside the observed H II regions.


title:
GRB060614 is at High Redshift, So No New Class of Gamma-Ray Bursts is
  Required

abstract:
  Long duration Gamma-Ray Bursts (GRBs) have been strongly connected with core
collapse supernovae, so it was surprising when the recent GRB060614 (with a
reported redshift of 0.125) was found to have no visible supernova to deep
limits. Three separate groups have reached the same conclusion that this event
forces the existence of a new previously-unsuspected class of GRBs. The problem
with this conclusion is that the redshift is not secure, as the measured galaxy
emission lines simply give the redshift of the brightest galaxy near the
line-of-sight to the GRB afterglow. Fortunately, eight different luminosity
indicators are known which can give the luminosity (and hence redshift) of the
GRB itself. In combination, these luminosity indicators have already proven to
give redshifts with average one-sigma errors of 26% as based on 69 GRBs with
spectroscopic redshifts. For GRB060614, the luminosity indicators all uniformly
give a high luminosity for the burst which implies a high redshift. This can be
seen by the spiky many-peaked light curve, the high E_{peak} value, the
near-zero spectral lag, and the timing of the jet break. Quantitatively, we
derive a redshift of 1.97 (1.44<z<2.81 one-sigma) from the eight luminosity
indicators. Additional information from the detection of the afterglow in all
Swift UVOT bands further constrains the redshift to be <1.71, so the final
range of allowed redshift is 1.44<z<1.71, which readily explains why no
supernova was visible. Thus, GRB060614 is at high redshift and is certainly not
evidence for a new class of GRBs.


title:
The Turn-On of Mass Transfer in AM CVn Binaries: Implications for RX
  J0806+1527 and RX J1914+2456

abstract:
  We report on evolutionary calculations of the onset of mass transfer in AM
CVn binaries, treating the donor's evolution in detail. We show that during the
early contact phase, while the mass transfer rate, $\Mdot$, is increasing,
gravity wave (GW) emission continues to drive the binary to shorter orbital
period, $\Porb$. We argue that the phase where $\Mdot > 0$ and $\nudot > 0$
($\nu = 1/\Porb$) can last between $10^3$ and $10^6$ yrs, significantly longer
than previously estimated. These results are applied to RX J0806+1527 ($\Porb =
321$ s) and RX J914+2456 ($\Porb=569$ s), both of which have measured $\nudot >
0$. \emph{Thus, a $\nudot > 0$ does not select between the unipolar inductor
and accretion driven models proposed as the source of X-rays in these systems}.
For the accretion model, we predict for RX J0806 that $\ddot{\nu} \approx
\ee{1.0-1.5}{-28}$ Hz s$^{-2}$ and argue that timing observations can probe
$\ddot{\nu}$ at this level with a total $\approx 20$ yr baseline. We also place
constraints on each system's initial parameters given current observational
data.


title:
Large-scale horizontal flows in the solar photosphere I: Method and
  tests on synthetic data

abstract:
  We propose a useful method for mapping large-scale velocity fields in the
solar photosphere. It is based on the local correlation tracking algorithm when
tracing supergranules in full-disc dopplergrams. The method was developed using
synthetic data. The data processing the data are transformed during the data
processing into a suitable coordinate system, the noise is removed, and finally
the velocity field is calculated. Resulting velocities are compared with the
model velocities and the calibration is done. From our results it becomes clear
that this method could be applied to full-disc dopplergrams acquired by the
Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory
(SoHO).


title:
Spitzer IRAC confirmation of z_850-dropout galaxies in the Hubble Ultra
  Deep Field: stellar masses and ages at z~7

abstract:
  Using Spitzer IRAC mid-infrared imaging from the Great Observatories Origins
Deep Survey, we study z_850-dropout sources in the Hubble Ultra Deep Field.
After carefully removing contaminating flux from foreground sources, we clearly
detect two z_850-dropouts at 3.6 micron and 4.5 micron, while two others are
marginally detected. The mid-infrared fluxes strongly support their
interpretation as galaxies at z~7, seen when the Universe was only 750 Myr old.
The IRAC observations allow us for the first time to constrain the rest-frame
optical colors, stellar masses, and ages of the highest redshift galaxies.
Fitting stellar population models to the spectral energy distributions, we find
photometric redshifts in the range 6.7-7.4, rest-frame colors U-V=0.2-0.4,
V-band luminosities L_V=0.6-3 x 10^10 L_sun, stellar masses 1-10 x 10^9 M_sun,
stellar ages 50-200 Myr, star formation rates up to ~25 M_sun/yr, and low
reddening A_V<0.4. Overall, the z=7 galaxies appear substantially less massive
and evolved than Lyman break galaxies or Distant Red Galaxies at z=2-3, but
fairly similar to recently identified systems at z=5-6. The stellar mass
density inferred from our z=7 sample is rho* = 1.6^{+1.6}_{-0.8} x 10^6 M_sun
Mpc^-3 (to 0.3 L*(z=3)), in apparent agreement with recent cosmological
hydrodynamic simulations, but we note that incompleteness and sample variance
may introduce larger uncertainties. The ages of the two most massive galaxies
suggest they formed at z>8, during the era of cosmic reionization, but the star
formation rate density derived from their stellar masses and ages is not nearly
sufficient to reionize the universe. The simplest explanation for this
deficiency is that lower-mass galaxies beyond our detection limit reionized the
universe.


title: Interstellar abundances in the neutral and ionized gas of NGC604

abstract:
  We present FUSE spectra of the giant HII region NGC604 in the spiral galaxy
M33. Chemical abundances are derived from far-UV absorption lines and are
compared to those derived from optical emission lines. We derived the column
densities of HI, NI, OI, SiII, PII, ArI, and FeII, fitting the line profiles
with either a single component or several components. Our net results, assuming
a single component, show that N, O, Si, and Ar are apparently underabundant in
the neutral phase by a factor of 10 or more with respect to the ionized phase,
while Fe is the same. However, we discuss the possibility that the absorption
lines are made of individual unresolved components, and find that only PII,
ArI, and FeII lines should not be affected by the presence of hidden saturated
components, while NI, OI, and SiII might be much more affected. If N, O, and Si
are actually underabundant in the neutral gas of NGC604 with respect to the
ionized gas, this would confirm earlier results obtained for the blue compact
dwarfs. However, a deeper analysis focused on P, Ar, and Fe mitigates the above
conclusion and indicates that the neutral gas and ionized gas could have
similar abundances.


title:
Spectroscopic Identification of Massive Galaxies at z~2.3 with Strongly
  Suppressed Star Formation

abstract:
  We present first results of a spectroscopic survey targeting K-selected
galaxies at z=2.0-2.7 using the GNIRS instrument on Gemini-South. We obtained
near-infrared spectra with a wavelength coverage of 1.0-2.5 micron for 26
K-bright galaxies (K<19.7) selected from the MUSYC survey using photometric
redshifts. We successfully derived spectroscopic redshifts for all 26 galaxies
using rest-frame optical emission lines or the redshifted Balmer/4000 Angstrom
break. Twenty galaxies have spectroscopic redshifts in the range 2.0<z<2.7, for
which bright emission lines like Halpha and [OIII] fall in atmospheric windows.
Surprisingly, we detected no emission lines for nine of these 20 galaxies. The
median 2 sigma upper limit on the rest-frame equivalent width of Halpha for
these nine galaxies is ~10 Angstrom. The stellar continuum emission of these
same nine galaxies is best fitted by evolved stellar population models. The
best-fit star formation rate (SFR) is zero for five out of nine galaxies, and
consistent with zero within 1 sigma for the remaining four. Thus, both the
Halpha measurements and the independent stellar continuum modeling imply that
45% of our K-selected galaxies are not forming stars intensely. This high
fraction of galaxies without detected line emission and low SFRs may imply that
the suppression of star formation in massive galaxies occurs at higher redshift
than is predicted by current CDM galaxy formation models. However, obscured
star formation may have been missed, and deep mid-infrared imaging is needed to
clarify this situation.


title:
AEGIS: A Panchromatic Study of IRAC-selected Extremely Red Objects with
  Confirmed Spectroscopic Redshifts

abstract:
  We study 87 Extremely Red Objects (EROs), selected both to have color redder
than R-[3.6] = 4.0, and to have confirmed spectroscopic redshifts. Together,
these two constraints result in this sample populating a fairly narrow redshift
range at 0.76 < z < 1.42. The key new ingredient included here is deep Spitzer
Space Telescope InfraRed Array Camera (IRAC) data. Based on [3.6]-[8.0] color,
we demonstrate that it is possible to classify EROs into early-type, dusty
starburst, or power-law (AGN) types. We present ultraviolet to mid-infrared
spectral energy distributions (SEDs) and Advanced Camera for Surveys (ACS)
images, both of which support our simple IRAC color classification.


title: Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions

abstract:
  We present five new satellites of the Milky Way discovered in Sloan Digital
Sky Survey (SDSS) imaging data, four of which were followed-up with either the
Subaru or the Isaac Newton Telescopes. They include four probable new dwarf
galaxies -- one each in the constellations of Coma Berenices, Canes Venatici,
Leo and Hercules -- together with one unusually extended globular cluster,
Segue 1. We provide distances, absolute magnitudes, half-light radii and
color-magnitude diagrams for all five satellites. The morphological features of
the color-magnitude diagrams are generally well described by the ridge line of
the old, metal-poor globular cluster M92. In the last two years, a total of ten
new Milky Way satellites with effective surface brightness mu_v >~ 28 mag/sq.
arcsec have been discovered in SDSS data. They are less luminous, more
irregular and appear to be more metal-poor than the previously-known nine Milky
Way dwarf spheroidals. The relationship between these objects and other
populations is discussed. We note that there is a paucity of objects with
half-light radii between ~40 pc and ~ 100 pc. We conjecture that this may
represent the division between star clusters and dwarf galaxies.


title: Population synthesis for symbiotic stars with white dwarf accretors

abstract:
  We have carried out a detailed study of symbiotic stars with white dwarf
accretors by means of a population synthesis code. We estimate the total number
of symbiotic stars with white dwarf accretors in the Galaxy as 1,200 - 15,000.
This range is compatible with observational estimates. Two crucial physical
parameters that define the birthrate and number of symbiotic stars are the
efficiency of accretion by white dwarfs (which greatly depends on the
separation of components after common envelope stage and stellar wind velocity)
and the mass of the hydrogen layer which the white dwarf can accumulate prior
to the hydrogen ignition. The theoretical estimate of the Galactic occurrence
rate of symbiotic novae ranges from about 1.3 to about 13.5 per year out of
which weak symbiotic novae comprise about 0.5 to 6.0 per year, depending on the
model assumptions. We simulate the distributions of symbiotic stars over
orbital periods, masses of components, mass-loss rates of cool components,
mass-accretion rates of hot components and luminosity of components. Agreement
with observations is reasonable.


title: The First Stars in the Universe and Cosmic Reionization

abstract:
  The earliest generation of stars, far from being a mere novelty, transformed
the universe from darkness to light. The first atoms to form after the Big Bang
filled the universe with atomic hydrogen and a few light elements. As gravity
pulled gas clouds together, the first stars ignited and their radiation turned
the surrounding atoms into ions. By looking at gas between us and distant
galaxies, we know that this ionization eventually pervaded all space, so that
few hydrogen atoms remain today between galaxies. Knowing exactly when and how
it did so is a primary goal of cosmologists, because this would tell us when
the early stars formed and in what kinds of galaxies. Although this ionization
is beginning to be understood by using theoretical models and computer
simulations, a new generation of telescopes is being built that will map atomic
hydrogen throughout the universe.


title: Sensitivity of Type I X-Ray Bursts to rp-Process Reaction Rates

abstract:
  First steps have been taken in a more comprehensive study of the dependence
of observables in Type I X-ray bursts on uncertain (p,gamma) reaction rates
along the rp-process path. We use the multizone hydrodynamics code KEPLER which
implicitly couples a full nuclear reaction network of more than 1000 isotopes,
as needed, to follow structure and evolution of the X-ray burst layer and its
ashes. This allows us to incorporate the full rp-process network, including all
relevant nuclear reactions, and individually study changes in the X-ray burst
light curves when modifying selected key nuclear reaction rates. In this work
we considered all possible proton captures to nuclei with 10 < Z < 28 and N <=
Z. When varying individual reaction rates within a symmetric full width
uncertainty of a factor of 10000, early results for some rates show changes in
the burst light curve as large as 10 percent of peak luminosity. This is very
large compared to the current sensitivity of X-ray observations. More precise
reaction rates are therefore needed to test current X-ray burst models,
particularly of the burst rise, with observational data and to constrain
astrophysical parameters.


title:
Pulsations detected in the line profile variations of red giants:
  Modelling of line moments, line bisector and line shape

abstract:
  Contents: So far, red giant oscillations have been studied from radial
velocity and/or light curve variations, which reveal frequencies of the
oscillation modes. To characterise radial and non-radial oscillations, line
profile variations are a valuable diagnostic. Here we present for the first
time a line profile analysis of pulsating red giants, taking into account the
small line profile variations and the predicted short damping and re-excitation
times. We do so by modelling the time variations in the cross correlation
profiles in terms of oscillation theory.
  Aims: The performance of existing diagnostics for mode identification is
investigated for known oscillating giants which have very small line profile
variations. We modify these diagnostics, perform simulations, and characterise
the radial and non-radial modes detected in the cross correlation profiles.
  Methods: Moments and line bisectors are computed and analysed for four
giants. The robustness of the discriminant of the moments against small
oscillations with finite lifetimes is investigated. In addition, line profiles
are simulated with short damping and re-excitation times and their line shapes
are compared with the observations.
  Results: For three stars, we find evidence for the presence of non-radial
pulsation modes, while for $\xi$ Hydrae perhaps only radial modes are present.
Furthermore the line bisectors are not able to distinguish between different
pulsation modes and are an insufficient diagnostic to discriminate small line
profile variations due to oscillations from exoplanet motion.


title:
Dense Molecular Gas and the Role of Star Formation in the Host Galaxies
  of Quasi-Stellar Objects

abstract:
  New millimeter-wave CO and HCN observations of the host galaxies of
infrared-excess Palomar Green quasi-stellar objects (PG QSOs) previously
detected in CO are presented. These observations are designed to assess the
validity of using the infrared luminosity to estimate star formation rates of
luminous AGN by determining the relative significance of dust-heating by young,
massive stars and active galactic nuclei (AGN) in QSO hosts and IRAS galaxies
with warm, AGN-like infrared colors. The HCN data show the PG QSO host IZw1 and
most of the warm IRAS galaxies to have high L_IR / L'_HCN (>1600) relative to
the cool IRAS galaxy population for which the median L_IR / L'_HCN ~
890(+440,-470). If the assumption is made that the infrared emission from cool
IRAS galaxies is reprocessed light from embedded star-forming regions, then
high values of L_IR / L'_HCN are likely the result of dust heating by the AGN.
Further, if the median ratio of L'_HCN / L'_CO ~ 0.06 observed for Seyfert
galaxies and IZw1 is applied to the PG QSOs not detected in HCN, then the
derived L_IR / L'_HCN correspond to a stellar contribution to the production of
L_IR of ~ 7-39%, and star formation rates ~ 2-37 M_sun/yr are derived for the
QSO hosts. Alternatively, if the far-infrared is adopted as the star formation
component of the total infrared in cool galaxies, the stellar contributions in
QSO hosts to their L_FIR are up to 35% higher than the percentages derived for
L_IR. This raises the possibility that the L_FIR in several of the PG QSO
hosts, including IZw1, could be due entirely to dust heated by young, massive
stars. Finally, there is no evidence that the global HCN emission is enhanced
relative to CO in galaxies hosting luminous AGN.


title: The WASP Project and the SuperWASP Cameras

abstract:
  The SuperWASP Cameras are wide-field imaging systems sited at the
Observatorio del Roque de los Muchachos on the island of La Palma in the Canary
Islands, and the Sutherland Station of the South African Astronomical
Observatory. Each instrument has a field of view of some ~482 square degrees
with an angular scale of 13.7 arcsec per pixel, and is capable of delivering
photometry with accuracy better than 1% for objects having V ~ 7.0 - 11.5.
Lower quality data for objects brighter than V ~15.0 are stored in the project
archive. The systems, while designed to monitor fields with high cadence, are
capable of surveying the entire visible sky every 40 minutes. Depending on the
observational strategy, the data rate can be up to 100GB per night. We have
produced a robust, largely automatic reduction pipeline and advanced archive
which are used to serve the data products to the consortium members. The main
science aim of these systems is to search for bright transiting exo-planets
systems suitable for spectroscopic followup observations. The first 6 month
season of SuperWASP-North observations produced lightcurves of ~6.7 million
objects with 12.9 billion data points.


title:
Analysis and Interpretation of Hard X-ray Emission from the Bullet
  Cluster (1E0657-56), the Most Distant Cluster of Galaxies Observed by RXTE

abstract:
  Evidence for non-thermal activity in clusters of galaxies is well established
from radio observations of synchrotron emission by relativistic electrons. New
windows in the Extreme Ultraviolet and Hard X-ray ranges have provided for more
powerful tools for the investigation of this phenomenon. Detection of hard
X-rays in the 20 to 100 keV range have been reported from several clusters of
galaxies, notably from Coma and others. Based on these earlier observations we
identified the relatively high redshift cluster 1E0657-56 (also known as RX
J0658-5557) as a good candidate for hard X-ray observations. This cluster, also
known as the bullet cluster, has many other interesting and unusual features,
most notably that it is undergoing a merger, clearly visible in the X-ray
images. Here we present results from a successful RXTE observations of this
cluster. We summarize past observations and their theoretical interpretation
which guided us in the selection process. We describe the new observations and
present the constraints we can set on the flux and spectrum of the hard X-rays.
Finally we discuss the constraints one can set on the characteristics of
accelerated electrons which produce the hard X-rays and the radio radiation.


title:
AEGIS: Infrared Spectroscopy of An Infrared Luminous Lyman Break Galaxy
  at z=3.01

abstract:
  We report the detection of rest--frame 6.2 and 7.7 \micron emission features
arising from Polycyclic Aromatic Hydrocarbons (PAH) in the Spitzer/IRS spectrum
of an infrared-luminous Lyman break galaxy at z=3.01. This is currently the
highest redshift galaxy where these PAH emission features have been detected.
The total infrared luminosity inferred from the MIPS 24 \micron and radio flux
density is 2$\times10^{13}$ L$_{\odot}$, which qualifies this object as a
so--called hyperluminous infrared galaxy (HyLIRG). However, unlike local
HyLIRGs which are generally associated with QSO/AGNs and have weak or absent
PAH emission features, this HyLIRG has very strong 6.2 and 7.7 \micron PAH
emission. We argue that intense star formation dominates the infrared emission
of this source, although we cannot rule out the presence of a deeply obscured
AGN. This LBG appears to be a distorted system in the HST ACS F606W and F814W
images, possibly indicating that a significant merger or interaction is driving
the large IR luminosity.


title: Morphological & Dynamical Properties of low redshift 2dFGRS Groups

abstract:
  We estimate the average group morphological and dynamical characteristics of
the Percolation-Inferred Galaxy Group (2PIGG) catalogue within z~0.08, for
which the group space density is roughly constant. We quantify the different
biases that enter in the determination of these characteristics and we devise
statistical correction procedures to recover their bias free values.
  We find that the only acceptable morphological model is that of prolate, or
triaxial with pronounced prolatness, group shapes having a roughly Gaussian
intrinsic axial ratio distribution with mean ~0.46 and dispersion of ~0.16.
After correcting for various biases, the most important of which is a redshift
dependant bias, the median values of the virial mass and virial radius of
groups with 4 to 30 galaxy members, is: Mv ~6 x 10^12 h_{72}^{-1} M_solar, Rv~
0.4 h^{-1}_{72} Mpc, which are significantly smaller than recent literature
values that do not take into account the previously mentioned biases. The group
mean crossing time is ~1.5 Gyr's, independent of the group galaxy membership.
We also find that there is a correlation of the group size, velocity dispersion
and virial mass with the number of group member galaxies, a manifestation of
the hierarchy of cosmic structures.


title:
Propeller activated resonances and the fate of short period cataclysmic
  variables

abstract:
  We show that the combination of a weak magnetic propeller and accretion disc
resonances can effectively halt accretion in short period cataclysmic variables
for large fractions of their lifetimes. This may help to explain the
discrepancy between the observed and predicted orbital period distributions of
cataclysmic variables at short periods. Orbital resonances cause the disc to
become eccentric, allowing material to fall back onto the donor star or out of
the system. A weak magnetic field on a rapidly spinning primary star propels
disc material outwards, allowing it to access these resonances. Numerical and
analytic calculations show that this state can be long lived (~10^11 yr). This
is because the magnetic propeller is required only to maintain access to the
resonances, and not to push matter out of the Roche lobe, so that the spin down
time-scale is much longer than for a classical propeller model.


title: Planetary Nebula Candidates in Extragalactic Young Star Clusters

abstract:
  During an analysis of optical spectra of 80 young star clusters in several
nearby spiral galaxies, [O III] and [N II] emission lines were noted in some
cases. Three of these emission line sources are identified as likely planetary
nebula (PN) candidates and may represent a rare opportunity to study PNe whose
progenitor stars are known to be of intermediate masses. This paper presents
and discusses basic properties of the PN candidates and their host clusters.
Based on the observed emission line fluxes, the excitation parameters and
luminosities of the nebulae are derived. This allows a crude placement of the
central stars in two of the objects on the H-R diagram, and their temperatures
and luminosities are found to be consistent with post-AGB model tracks for a
central star mass of about 0.60 Msun. Host cluster ages and masses are
estimated from broad-band colours and by comparison with model SSP spectra. One
of the host clusters has an age of 32-65 Myrs, corresponding to a main sequence
turn-off mass of M(TO) = 6.6-9.0 Msun. For the other cluster the age is 282-407
Myrs, corresponding to M(TO) = 3.2-3.6 Msun. By estimating the number of stars
evolving off the main sequence per year, a total of 6 PNe are expected in our
full sample of 80 clusters for aPN lifetime of 10000 years. The factor of two
disagreement with the actual observed number may be due, among other things, to
uncertainties in PN lifetimes. It is interesting to note that all three PN
candidates are associated with clusters which are more diffuse than average.
While PNe have previously been found in some old globular clusters, the
candidates identified here are among the first identified in young star
clusters.


title: Astrophysics of extreme mass ratio inspiral sources

abstract:
  Compact remnants on orbits with peri-apses close to the Schwarzschild radius
of a massive black hole (MBH) lose orbital energy by emitting gravitational
waves (GWs) and spiral in. Scattering with other stars allows successful
inspiral of such extreme mass ratio inspiral sources (EMRIs) only within small
distances, a < few \times 0.01 pc from the MBH. The event rate of EMRIs is
therefore dominated by the stellar dynamics and content in the inner few \times
0.01 pc. I discuss the relevant dynamical aspects and resulting estimated event
rates of EMRIs. Subjects considered include the loss-cone treatment of inspiral
sources; mass segregation; resonant relaxation; and alternative routes to EMRI
formation such as tidal binary disruptions, stellar formation in disks and
tidal capture of massive main sequence stars. The EMRI event rate is estimated
to be of order few \times 10^2/Gyr per MBH, giving excellent prospects for
observation by LISA.


title:
The nuclear regions of NGC 7582 from [NeII] spectroscopy at 12.8 microns
  - an estimate of the black hole mass

abstract:
  We present a high-resolution (R~16,000) spectrum and a narrow-band image
centered on the [NeII]12.8 micron line of the central kpc region of the
starburst/Seyfert2 galaxy NGC 7582. The galaxy has a rotating circum-nuclear
starburst disk, shown at great detail at a diffraction-limited resolution of
0.4 arcsec. The high spatial resolution allows us to probe the dynamics of the
[NeII] gas in the nuclear regions, and to estimate the mass of the central
black hole. We construct models of gas disks rotating in the combined
gravitational potential from the stellar bulge and a central black hole, and
derive a black hole mass of 5.5 x 10^7 solar masses with a 95% confidence
interval of [3.6,8.1] x 10^7 solar masses. The black hole mass combined with
stellar velocity dispersion measurements from the literature shows that the
galaxy is consistent with the local M-sigma relation. This is the first time
that a black hole mass in a galaxy except our own Milky Way system has been
estimated from gas dynamics in the mid-infrared. We show that spatially
resolved mid-infrared spectroscopy may be competitive with similar techniques
in the optical and near-infrared, and may prove to be important for estimating
black hole masses in galaxies with strong nuclear dust obscuration. The high
spectral resolution allows us to determine the heliocentric systemic velocity
of the galaxy to between 1614 and 1634 km/s. The mid-infrared image reveals
several dense knots of dust-embedded star formation in the circum-nuclear disk,
and we briefly discuss its morphology.


title: A current driven instability in parallel, relativistic shocks

abstract:
  Recently, Bell has reanalysed the problem of wave excitation by cosmic rays
propagating in the pre-cursor region of a supernova remnant shock front. He
pointed out a strong, non-resonant, current-driven instability that had been
overlooked in the kinetic treatments, and suggested that it is responsible for
substantial amplification of the ambient magnetic field. Magnetic field
amplification is also an important issue in the problem of the formation and
structure of relativistic shock fronts, particularly in relation to models of
gamma-ray bursts. We have therefore generalised the linear analysis to apply to
this case, assuming a relativistic background plasma and a monoenergetic,
unidirectional incoming proton beam. We find essentially the same non-resonant
instability noticed by Bell, and show that also under GRB conditions, it grows
much faster than the resonant waves. We quantify the extent to which thermal
effects in the background plasma limit the maximum growth rate.


title:
The 2004 Hyperflare from SGR 1806-20: Further Evidence for Global
  Torsional Vibrations

abstract:
  We report an analysis of the archival Rossi X-ray Timing Explorer (RXTE) data
from the December 2004 hyperflare from SGR 1806-20. In addition to the 90 Hz
QPO first discovered by Israel et al., we report the detection of higher
frequency oscillations at 150, 625, and 1,840 Hz. In addition, we also find
indications of oscillations at 720, and 2,384 Hz, but with lower significances.
The 150 Hz QPO has a width (FWHM) of about 17 Hz, an average amplitude (rms) of
6.8 %, and is detected in average power spectra centered on the rotational
phase of the strongest peak in the pulse profile. This is approximately half a
cycle from the phase at which the 90 Hz QPO is detected. The 625 Hz oscillation
was detected in an average power spectrum from nine successive cycles beginning
approximately 180 s after the initial hard spike. It has a width (FWHM) of 2 Hz
and an average amplitude (rms) during this interval of 8.5 %. We find a strong
detection of the 625 Hz oscillation in a pair of successive rotation cycles
begining about 230 s after the start of the flare. In these cycles we also
detect the 1,840 Hz QPO. When the 625 Hz QPO is detected we also confirm the
simultaneous presence of 30 and 92 Hz QPOs. The centroid frequency of the 625
Hz QPO detected with RXTE is within 1 Hz of the 626 Hz oscillation recently
found in RHESSI data from this hyperflare by Watts & Strohmayer. We argue that
these new findings provide further evidence for a connection of these
oscillations with global oscillation modes of neutron stars, in particular, the
high frequency signals may represent toroidal modes with at least one radial
node in the crust. We discuss their implications in the context of this model,
in particular for the depth of neutron star crusts


title: Search and analysis of blue straggler stars in open clusters

abstract:
  Aims: This paper presents a new homogeneous catalogue of blue straggler stars
(BSS) in Galactic open clusters. Methods: Photometric data for 216 clusters
were collected from the literature and 2782 BSS candidates were extracted from
76 of them. Results: We found that the anticorrelation of BSS frequency vs.
total magnitude identified in similar studies conducted on Galactic globular
clusters extends to the open cluster regime: clusters with smaller total
magnitude tend to have higher BSS frequencies. Moreover, a clear correlation
between the BSS frequency (obtained normalising the total number of BSS either
to the total cluster mass or, for the older clusters, to the total number of
clump stars) and the age of the clusters was found. A simple model is developed
here to try to explain this last and new result. The model allows us to
ascertain the important effect played by mass loss in the evolution of open
clusters.


title:
Triggered massive-star formation on the borders of Galactic HII regions.
  III. Star formation at the periphery of Sh2-219

abstract:
  Context. Massive-star formation triggered by the expansion of HII regions.
Aims. To understand if sequential star formation is taking place at the
periphery of the HII region Sh2-219. Methods. We present 12CO(2-1) line
observations of this region, obtained at the IRAM 30-m telescope (Pico Veleta,
Spain). Results. In the optical, Sh2-219 is spherically symmetric around its
exciting star; furthermore it is surrounded along three quarters of its
periphery by a ring of atomic hydrogen. This spherical symmetry breaks down at
infrared and millimetre wavelengths. A molecular cloud of about 2000\msol lies
at the southwestern border of Sh2-219, in the HI gap. Two molecular
condensations, elongated along the ionization front, probably result from the
interaction between the expanding HII region and the molecular cloud. In this
region of interaction there lies a cluster containing many highly reddened
stars, as well as a massive star exciting an ultracompact HII region. More
surprisingly, the brightest parts of the molecular cloud form a `chimney',
perpendicular to the ionization front. This chimney is closed at its south-west
extremity by H-alpha walls, thus forming a cavity. The whole structure is 7.5
pc long. A luminous H-alpha emission-line star, lying at one end of the chimney
near the ionization front, may be responsible for this structure. Confrontation
of the observations with models of HII region evolution shows that Sh2-219 is
probably 10^5 yr old. The age and origin of the near-IR cluster observed on the
border of Sh2-219 remain unknown.


title: Using Radio Bubbles to Constrain the Matter Content of AGN Jets

abstract:
  We revisit a method to obtain upper limits on the jet matter content
combining synchrotron self-absorption constraints and the large scale bubble
energy. We use both X-ray observations, which give limits on the jet power from
the energies and timescales of bubbles found in clusters of galaxies, and radio
observations, which give limits on the magnetic field in the jets. Combining
the two imposes constraints on the particle number density, and hence the jet
content. Out of a sample of clusters which have clear radio bubbles, there are
only two which have sufficient resolution in the radio images to give
significant constraints, under the assumption that the jets are fairly steady.
The results for M87 and Perseus indicate that the radio emitting region of the
jet is electron-positron dominated, assuming that the minimum of the electron
energy distribution, gamma_min~1.


title:
The Effects of Thermal Conduction on Radiatively-Inefficient Accretion
  Flows

abstract:
  We quantify the effects of electron thermal conduction on the properties of
hot accretion flows, under the assumption of spherical symmetry. Electron heat
conduction is important for low accretion rate systems where the electron
cooling time is longer than the conduction time of the plasma, such as Sgr A*
in the Galactic Center. For accretion flows with density profiles similar to
the Bondi solution (n[r] ~ r^[-3/2]), we show that heat conduction leads to
super-virial temperatures, implying that conduction significantly modifies the
dynamics of the accretion flow. We then self-consistently solve for the
dynamics of spherical accretion in the presence of saturated conduction and
electron heating. We find that the accretion rate onto the central object can
be reduced by ~1-3 orders of magnitude relative to the canonical Bondi rate.
Electron conduction may thus be an important ingredient in explaining the low
radiative efficiencies and low accretion rates inferred from observations of
low-luminosity galactic nuclei. The solutions presented in this paper may also
describe the nonlinear saturation of the magnetothermal instability in hot
accretion flows.