title:
The Fluorescence Detector of the Pierre Auger Observatory - A
  Calorimeter for UHECR

abstract:
  The Pierre Auger Observatory is a hybrid detector for ultrahigh energy cosmic
rays (UHECR) with energies above 10$^{18.5}$ eV. Currently the first part of
the Observatory nears completion in the southern hemisphere in Argentina. One
detection technique uses over 1600 water Cherenkov tanks at ground where
samples of secondary particles of extensive air showers (EAS) are detected. The
second technique is a calorimetric measurement of the energy deposited by EAS
in the atmosphere. Charged secondary particles of EAS lose part of their energy
in the atmosphere via ionization. The deposited energy is converted into
excitation of molecules of the air and afterwards partly emitted as
fluorescence light mainly from nitrogen in the wavelength region between 300
and 400 nm. This light is observed with 24 fluorescence telescopes in 4
stations placed at the boundary of the surface array. This setup provides a
combined measurement of the longitudinal shower development and the lateral
particle distribution at ground of the same event. Details on the fluorescence
technique and the necessary atmospheric monitoring will be presented, as well
as first physics results on UHECR.


title:
3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line
  profile morphologies

abstract:
  Using a Monte Carlo technique, we have developed a 3D lyman-alpha radiation
transfer code allowing for prescribed arbitrary hydrogen density, ionisation,
temperature structures, and dust distribution, and arbitrary velocity fields
and UV photon sources.
  We have examined the lyman-alpha line profiles predicted for several simple
geometrical configurations and their dependence on the main input parameters.
Overall, we find line profiles reaching from doubly peaked symmetric emission
to symmetric Voigt (absorption) in static configurations with increasing dust
content, and asymmetric red-(blue-) shifted emission lines with a blue (red)
counterpart ranging from absorption to emission (with increasing line/continuum
strength) in expanding (infalling) media.
  The following results are of interest for the interpretation of lya profiles
from galaxies. 1/ Standard lya absorption line fitting of global spectra of
galaxies may lead to an underestimate of the true hydrogen column density in
certain geometrical conditions. 2/ Normal (inverted) P-Cygni like lya profiles
can be obtained in expanding (infalling) media from objects without any
intrinsic lya emission, as a natural consequence of radiation transfer effects.
3/ The formation and the detailed shape of lya profiles resulting from
expanding shells has been thoroughly revised: for sufficiently large column
densities, the position of the main lya emission peak is redshifted by twice
the expansion velocity.This is in excellent agreement with the observations of
z~3 LBGs. This finding indicates also that large scale, fairly symmetric shell
structures must be a good description for the outflows in LBGs.(shortened
abstract)


title: Wolf-Rayet Populations at High Metallicity

abstract:
  Observed properties of Wolf-Rayet stars at high metallicity are reviewed.
Wolf-Rayet stars are more common at higher metallicity, as a result of stronger
mass-loss during earlier evolutionary phases with late WC subtypes signatures
of solar metallicity or higher. Similar numbers of early (WC4-7) and late
(WC8-9) stars are observed in the Solar neighbourhood, whilst late subtypes
dominate at higher metallicities, such as Westerlund 1 in the inner Milky Way
and in M83. The observed trend to later WC subtype within metal-rich
environments is intimately linked to a metallicity dependence of WR stars, in
the sense that strong winds preferentially favour late subtypes. This has
relevance to (a) the upper mass limit in metal-rich galaxies such as NGC 3049,
due to softer ionizing fluxes from WR stars at high metallicity; (b)
evolutionary models including a WR metallicity dependence provide a better
match to the observed N(WC)/N(WN) ratio. The latter conclusion partially rests
upon the assumption of constant line luminosities for WR stars, yet
observations and theoretical atmospheric models reveal higher line fluxes at
high metallicity.


title: 2.3 micron CO emission and absorption from young high-mass stars in M17

abstract:
  We are studying the extremely young cluster of M17 to investigate the birth
of high-mass stars and the initial mass function. Deep JHKL imaging and K-band
spectroscopy from the VLT of 201 stars toward the cluster is presented. The
majority of 104 stars show the CO band-head in absorption. Half of them emit
X-rays and/or have infrared excess, indicative of very young objects. Their
intrinsic IR luminosity is compatible with intermediate and high-mass pre-main
sequence stars. Nine additional stars have the CO feature in emission, while
sixty sources are lacking any stellar spectral feature due to veiling by
circumstellar dust. We suggest that CO absorption is - as in the case of
low-mass stars - also a common feature during the early evolution of stars with
higher masses. According to model calculations the observed CO absorption is
most likely a sign of heavily accreting protostars with mass accretion rates
above 10^-5 solar masses/yr.


title:
The Galactic WN stars: Spectral analyses with line-blanketed model
  atmospheres versus stellar evolution models with and without rotation

abstract:
  CONTEXT: Very massive stars pass through the Wolf-Rayet (WR) stage before
they finally explode. Details of their evolution have not yet been safely
established, and their physics are not well understood. Their spectral analysis
requires adequate model atmospheres, which have been developed step by step
during the past decades and account in their recent version for line blanketing
by the millions of lines from iron and iron-group elements. However, only very
few WN stars have been re-analyzed by means of line-blanketed models yet.
  AIMS: The quantitative spectral analysis of a large sample of Galactic WN
stars with the most advanced generation of model atmospheres should provide an
empirical basis for various studies about the origin, evolution, and physics of
the Wolf-Rayet stars and their powerful winds.
  METHODS: We analyze a large sample of Galactic WN stars by means of the
Potsdam Wolf-Rayet (PoWR) model atmospheres, which account for iron line
blanketing and clumping. The results are compared with a synthetic population,
generated from the Geneva tracks for massive star evolution. RESULTS: We obtain
a homogeneous set of stellar and atmospheric parameters for the Galactic WN
stars, partly revising earlier results.
  CONCLUSIONS: Comparing the results of our spectral analyses of the Galactic
WN stars with the predictions of the Geneva evolutionary calculations, we
conclude that there is rough qualitative agreement. However, the quantitative
discrepancies are still severe, and there is no preference for the tracks that
account for the effects of rotation. It seems that the evolution of massive
stars is still not satisfactorily understood.


title: Radio emission from shell-type supernova remnants

abstract:
  The evolution of the radio emission of shell-type Supernova remnants (SNRs)
is modeled within the framework of the simple and commonly used assumptions
that the mechanism of diffusive shock acceleration (DSA) is responsible for
generating radio emitting electrons and that the magnetic field is the typical
interstellar field compressed at the shock. It is considered that electrons are
injected into the mechanism in test-particle regime directly from the high
energy tail of the downstream Maxwellian distribution function. The model can
be applied to most of the observed SNRs. It is shown that the model
successfully explains the many averaged observational properties of evolved
shell-type SNRs. In particular, the radio surface brightness ($\Sigma$) evolves
with diameter as $\sim D^{-(0.3 \div 0.5)}$, while the bounding shock is strong
(Mach number is ${\mathcal M} \geq10$), followed by steep decrease (steeper
than $\sim D^{-4.5}$) for ${\cal M} <10$. Such evolution of the surface
brightness with diameter and its strong dependence on the environmental
parameters strongly reduce the usefulness of $\Sigma - D$ relations as a tool
for determining the distances to SNRs. The model predicts no radio emission
from SNRs in the late radiative stage of evolution and the existence of
radio-quiet but relatively active SNRs is possible. Our model easily explains
very large-diameter radio sources such as the Galactic Loops and the candidates
for Hypernova radio remnants. The model predicts that most of the observed SNRs
are located in a tenuous phase of the ISM. From the comparison of the model
results with the statistics of evolved shell-type SNRs, we were able to
estimate the fraction of electrons accelerated from the thermal pool in the
range $(3\div 11) \times 10^{- 4}$.


title:
A spectroscopic atlas of post-AGB stars and planetary nebulae selected
  from the IRAS Point Source Catalogue

abstract:
  Aims: We study the optical spectral properties of a sample of stars showing
far infrared colours similar to those of well-known planetary nebulae. The
large majority of them were unidentified sources or poorly known in the
literature at the time when this spectroscopic survey started, some 15 years
ago.
  Methods: We present low-resolution optical spectroscopy, finding charts and
improved astrometric coordinates of a sample of 253 IRAS sources.
  Results: We have identified 103 sources as post-AGB stars, 21 as ``transition
sources'', and 36 as planetary nebulae, some of them strongly reddened. Among
the rest of sources in the sample, we were also able to identify 38 young
stellar objects, 5 peculiar stars, and 2 Seyfert galaxies. Up to 49 sources in
our spectroscopic sample do not show any optical counterpart, and most of them
are suggested to be heavily obscured post-AGB stars, rapidly evolving on their
way to becoming planetary nebulae.
  Conclusions: An analysis of the galactic distribution of the sources
identified as evolved stars in the sample is presented together with a study of
the distribution of these stars in the IRAS two-colour diagram. Finally, the
spectral type distribution and other properties of the sources identified as
post-AGB in this spectroscopic survey are discussed in the framework of stellar
evolution.


title: CG Draconis, a particularly active dwarf nova

abstract:
  The dwarf nova CG Dra was intensively monitored during 2005 as part of the
Variable Star Sections Recurrent Objects Programme and seven outbursts were
detected. These observations were combined with others from the BAA and AAVSO
databases which confirmed that the star shows frequent outbursts with a period
of around 11 days. Two types of outburst have been detected. Short outbursts
lasting about 4 days and long outbursts lasting about 8 days.


title:
Determination of the superhump period of the dwarf nova V701 Tau during
  the 2005 December superoutburst

abstract:
  We report new measurements of the superhump period of the UGSU-type dwarf
nova V701 Tau during the 2005 December superoutburst. Using unfiltered time
series CCD observations on 3 nights, we determine a probable superhump period
Psh = 0.0690, plus or minus 0.0002d, but note that our data also permit a
possible shorter period of 0.0663, plus or minus 0.0002d. The longer period
agrees with the value measured during the first recorded superoutburst in 1995.


title:
Spitzer Observations of Var Her 04: Possible Detection of Dust Formation
  in a Super-Outbursting TOAD

abstract:
  We present four MIPS (24 \micron) and two IRAC (3.6, 4.5, 5.8, and 8.0
\micron) Spitzer observations of the newly discovered Tremendous Outburst
Amplitude Dwarf nova (TOAD) Var Her 04 during decline from super-outburst. The
four MIPS observations span 271 days and the two IRAC observations span 211
days. Along the line-of-sight to Var Her 04, there is a foreground M-star
within 1\arcsec of the variable; as a result, all of the Spitzer photometry
presented in this paper is a blend of the foreground M-star and Var Her 04. We
estimate the quiescent level of the TOAD to be $\Delta V=4-5$ magnitudes below
that of the M-star. Based upon the spectral energy distribution and the 2MASS
colors, we find the M-star to be an M3.5V dwarf at a distance of 80-130 pc.
Based upon its outburst amplitude and quiescent apparent magnitude, we estimate
the distance to Var Her 04 to be 200-400 pc, suggesting that the line-of-sight
foreground star is physically unrelated to the cataclysmic variable. All of the
Spitzer photometry is consistent with the photospheric emission of the
line-of-sight M3.5V star, except for one 24 \micron observation obtained after
the variable re-brightened. This 24 \micron flux density is 75 $\mu$Jy
($4\sigma$) above the preceding and following MIPS observations. We tentatively
suggest that the mid-infrared brightening of 75 $\mu$Jy may be associated with
a dust formation event in the super-outburst ejecta. Assuming a dust
temperature of 100-400 K, we have estimated the amount of dust required. We
find $10^{-13}-10^{-11}$ M$_\odot$ of dust is needed, consistent with amounts
of mass ejection in TOADs expected during super-outburst, and possibly making
TOADs important contributors to the recycling of the interstellar medium.


title: X-ray Spectral Variations of U Gem from Quiescence to Outburst

abstract:
  In this paper we report the discovery of a high energy component of the X-ray
spectra of U Gem, which can be observed while the source is in outburst. We
used Chandra and XMM-Newton observations to compare the quiescence and outburst
X-ray spectra of the source. The additional component may be the result of the
reflection of X-rays emitted from an optically thin plasma close to the white
dwarf, from the optically thick boundary layer during the outburst. Another
possible explanation is that some magnetically channeled accretion may occur
onto the equatorial belt of the primary causing shocks similar to the ones in
the intermediate polars as it was suggested by \citep{w2002}. We have also
found a timing structure at about 73 mHz ($\sim$13.7 s.) in the RXTE
observation, resembling dwarf novae oscillations (DNOs).


title: The intergalactic propagation of ultra-high energy cosmic ray nuclei

abstract:
  We investigate the propagation of ultra-high energy cosmic ray nuclei (A =
1-56) from cosmologically distant sources through the cosmic radiation
backgrounds. Various models for the injected composition and spectrum and of
the cosmic infra-red background are studied using updated photo-disintegration
cross-sections. The observational data on the spectrum and the composition of
ultra-high energy cosmic rays are jointly consistent with a model where all of
the injected primary cosmic rays are iron nuclei (or a mixture of heavy and
light nuclei).


title: The Spiral Host Galaxy of the Double Radio Source 0313-192

abstract:
  We present new Hubble, Gemini-S, and Chandra observations of the radio galaxy
0313-192, which hosts a 350-kpc double source and jets, even though previous
data have suggested that it is a spiral galaxy. We measure the bulge scale and
luminosity, radial and vertical profiles of disk starlight, and consider the
distributions of H II regions and absorbing dust. In each case, the HST data
confirm its classification as an edge-on spiral galaxy, the only such system
known to produce such an extended radio source of this kind. The Gemini near-IR
images and Chandra spectral fit reveal a strongly obscured central AGN, seen
through the entire ISM path length of the disk and showing X-ray evidence of
additional absorption from warm or dense material close to the central object.
We consider several possible mechanisms for producing such a rare combination
of AGN and host properties, some combination of which may be at work. These
include an unusually luminous bulge (suggesting a black hole of mass 0.5-0.9
billion solar masses), orientation of the jets near the pole of the gas-rich
disk, and some evidence of a weak gravitational interaction which has warped
the disk and could have enhanced fuelling of the central engine. An X-ray
counterpart of the kiloparsec-scale radio jet emerges to the south;
jet/counterjet limits in both radio and X-ray allow them to be symmetric if
seen more than 15 degrees from the plane of the sky, still consistent with the
jet axes being within ~30 degrees of the poles of the gas-rich galaxy disk. A
linear or disklike emission-line structure is seen around thenucleus, inclined
by ~20 degrees to the stellar disk but nearly perpendicular to the jets; this
may represent the aftermath of a galaxy encounter, where gas is photoionized by
the nuclear continuum.


title: The Energy Transfer Process in Planetary Flybys

abstract:
  We illustrate the energy transfer during planetary flybys as a function of
time using a number of flight mission examples. The energy transfer process is
rather more complicated than a monotonic increase (or decrease) of energy with
time. It exhibits temporary maxima and minima with time which then partially
moderate before the asymptotic condition is obtained. The energy transfer to
angular momentum is exhibited by an approximate Jacobi constant for the system.
We demonstrate this with flybys that have shown unexplained behaviors: i) the
possible onset of the "Pioneer anomaly" with the gravity assist of Pioneer 11
by Saturn to hyperbolic orbit (as well as the Pioneer 10 hyperbolic gravity
assist by Jupiter) and ii) the Earth flyby anomalies of small increases in
energy {\it in the geocentric system} (Galileo-I, NEAR, and Rosetta, in
additioon discussing the Cassini and Messenger flybys). Perhaps some small, as
yet unrecognized effect in the energy-transfer process can shed light on these
anomalies.


title: A relativistic model of the radio jets in 3C 296

abstract:
  We present new, deep 8.5-GHz VLA observations of the nearby, low-luminosity
radio galaxy 3C 296 at resolutions from 0.25 to 5.5 arcsec. These show the
intensity and polarization structures of the twin radio jets in detail. We also
derive the spectral-index and rotation-measure distributions. We apply our
intrinsically symmetrical, decelerating relativistic jet model to the new
observations. An optimized model accurately fits the data in both total
intensity and linear polarization. We infer that the jets are inclined by 58
deg to the line of sight. On-axis, they decelerate from a (poorly-constrained)
initial velocity of 0.8c to approximately 0.4c around 5 kpc from the nucleus,
the velocity thereafter remaining constant. The speed at the edge of the jet is
low everywhere. The longitudinal profile of proper emissivity has three
principal power-law sections and the emission is centre-brightened. Our
observations rule out a globally-ordered, helical magnetic-field configuration.
Instead, we model the field as random on small scales but anisotropic, with
toroidal and longitudinal components only. The ratio of longitudinal to
toroidal field falls with distance along the jet, qualitatively but not
quantitatively as expected from flux freezing, so that the field is
predominantly toroidal far from the nucleus. The toroidal component is
relatively stronger at the edges of the jet. A simple adiabatic model fits the
emissivity evolution only in the outer region after the jets have decelerated
and recollimated; closer to the nucleus, it predicts far too steep an
emissivity decline with distance. We also interpret the morphological
differences between brightness enhancements ("arcs") in the main and
counter-jets as an effect of relativistic aberration. (Abridged)


title: Discovery of twin kHz QPOs in the peculiar X-ray binary Circinus X-1

abstract:
  We report the discovery with the RXTE/PCA of twin kHz QPOs in Cir X-1. Eleven
cases of simultaneous double QPOs occurred, with significances of up to 6.3 and
5.5 sigma and centroid frequencies ranging between approximately 56-225 and
230-500 Hz for the two QPO peaks, respectively, i.e., for the most part at
frequencies well below those of other sources. The QPO properties clearly
indicate that these double peaks are the kHz QPOs known from low magnetic field
neutron stars, and not black-hole high-frequency QPOs, confirming that Cir X-1
is a neutron star. The kHz QPO peak separation varies over a wide range,
\~175-340 Hz, and increases with QPO frequency. This is contrary to what is
seen in other sources but agrees with predictions of the relativistic
precession model and Alfven wave models; beat-frequency models require
modification to accommodate this. In other observations single kHz QPOs can be
seen down to frequencies as low as ~12 Hz, as well as a strong low-frequency
(LF) QPO between 1 and 30 Hz. The relations between the frequencies of the kHz
QPOs and the LF QPO are in good agreement with those found previously in Z
sources, confirming that Cir X-1 may be a peculiar Z source. We suggest that
the low frequencies of the kHz QPOs in Cir X-1 and to a lesser extent in
(other) Z sources might be due to a relatively stronger radial inflow to the
neutron star than in other kHz QPO sources.


title: Upper Bound on the Dark Matter Total Annihilation Cross Section

abstract:
  We consider dark matter annihilation into Standard Model particles and show
that the least detectable final states, namely neutrinos, define an upper bound
on the total cross section. Calculating the cosmic diffuse neutrino signal, and
comparing it to the measured terrestrial atmospheric neutrino background, we
derive a strong and general bound. This can be evaded if the annihilation
products are dominantly new and truly invisible particles. Our bound is much
stronger than the unitarity bound at the most interesting masses, shows that
dark matter halos cannot be significantly modified by annihilations, and can be
improved by a factor of 10--100 with existing neutrino experiments.


title:
An Upper Limit to the Degree of Evolution Between Supermassive Black
  Holes and their Host Galaxies

abstract:
  We describe a model-independent integral constraint which defines an upper
limit to the allowed degree of evolution in the ratio of black hole (BH) mass
to host galaxy luminosity or mass, as a function of redshift. Essentially, if
the BH/host ratio is excessive at redshift z, then it would imply that the
total mass density in BHs above some M_BH(min) is larger at that redshift than
at z=0, which is impossible. This argument requires no knowledge of host or BH
properties, only a lower limit to the observed luminosity density in the
brightest galaxies at some z. We calculate this upper limit from a variety of
luminosity and mass functions in different bands from redshifts z=0-2. We show
that it is consistent with passive evolution of spheroid populations (with a
fixed M_BH/M_host relation) in all cases, and provides tighter constraints than
have generally been obtained previously, ruling out at >6 sigma observational
and theoretical estimates suggesting that M_BH/M_host was significantly larger
at high redshifts than locally, although relatively weak (factor ~2 by z=2)
evolution is still allowed. We discuss a variety of possible 'loopholes' or
changes in the BH/host populations and correlations, and show that they
typically lower the upper limits and strengthen our conclusions.


title:
Two-Photon Absorption by Hydrogen Molecules: Origin of the 2175 Angstrom
  Astronomical Band?

abstract:
  The near UV spectra of OB stars in our galaxy are often dominated by a very
broad extinction band peaking at ~2175 Angstroms. Forty years after its
discovery, the origin of this band remains unknown, although interstellar dust
particles are generally assumed to be the carriers. Here we report that
two-photon absorption by hydrogen molecules in gaseous clouds enveloping OB
stars can lead to a band peaking at ~2175 Angstroms. We present astronomical
spectral evidence supporting our proposal that this nonlinear absorption
mechanism accounts for the lambda2175 feature.


title:
Accurate M Dwarf Metallicities from Spectral Synthesis: A Critical Test
  of Model Atmospheres

abstract:
  We describe a method for accurately determining M dwarf metallicities with
spectral synthesis based on abundance analyses of visual binary stars. We
obtained high resolution, high signal-to-noise spectra of each component of
five visual binary pairs at McDonald Observatory. The spectral types of the
components range from F7 to K3 V for the primaries and M0.5 to M3.5 V for the
secondaries. We have determined the metallicities of the primaries
differentially with respect to the Sun by fitting synthetic spectra to Fe
\textsc{i} line profiles in the observed spectra. In the course of our analysis
of the M dwarf secondaries we have made significant improvements to the PHOENIX
cool-star model atmospheres and the spectrum analysis code MOOG. Our analysis
yields a RMS deviation of 0.11 dex in metallicity values between the binary
pairs. We estimate the uncertainties in the derived stellar parameters for the
M dwarfs to be 48 K, 0.10 dex, 0.12 dex, 0.15 km s$^{-1}$, and 0.20 km s$^{-1}$
for {T}$_{eff}$, log \textsl{g}, [M/H], $\xi$, and $\eta$ respectively.
Accurate stellar evolutionary models are needed to progress further in the
analysis of cool-star spectra; the new model atmospheres warrant recalculation
of the evolutionary models.


title: Atmospheres and Winds of PN Central Stars

abstract:
  The progress over the last years in modelling the atmospheres and winds of PN
central stars is reviewed. We discuss the effect of the inclusion of the
blanketing by millions of metal lines in NLTE on the diagnostics of
photospheric and stellar wind lines, which can be used to determine stellar
parameters such as effective temperature, gravity, radius, mass loss rate and
distance. We also refer to recent work on the winds of massive O-type stars,
which indicates that their winds are possibly inhomogeneous and clumped. We
investigate implications from this work on the spectral diagnostics of PN
central stars and introduce a method to determine wind clumping factors from
the relative strengths of Halpha and HeII 4686. Based on new results we discuss
the wind properties of CSPN.


title: Tidal Tails Test the Equivalence Principle in the Dark Sector

abstract:
  Satellite galaxies currently undergoing tidal disruption offer a unique
opportunity to constrain an effective violation of the equivalence principle in
the dark sector. Theories in which cold dark matter (CDM) couples to a light
scalar field naturally lead to a long-range force between dark matter
particles. An inverse-square-law force of this kind would manifest itself as a
violation of the equivalence principle in the dynamics of CDM compared to
baryons in the form of gas or stars. In a previous paper, we showed that an
attractive force would displace stars outwards from the bottom of the
satellite's gravitational potential well, leading to a higher fraction of stars
being disrupted from the tidal bulge further from the Galactic center. Since
stars disrupted from the far (near) side of the satellite go on to form the
trailing (leading) tidal stream, an attractive dark-matter force will produce a
relative enhancement of the trailing stream compared to the leading stream.
This distinctive signature of a dark-matter force might be detected through
detailed observations of the tidal tails of a disrupting satellite, such as
those recently performed by the Two-Micron All-Sky Survey (2MASS) and Sloan
Digital Sky Survey (SDSS) on the Sagittarius (Sgr) dwarf galaxy. Here we show
that this signature is robust to changes in our models for both the satellite
and Milky Way, suggesting that we might hope to search for a dark-matter force
in the tidal features of other recently discovered satellite galaxies in
addition to the Sgr dwarf.


title: Detecting sterile dark matter in space

abstract:
  Space-based instruments provide new and, in some cases, unique opportunities
to search for dark matter. In particular, if dark matter comprises sterile
neutrinos, the x ray detection of their decay line is the most promising
strategy for discovery. Sterile neutrinos with masses in the keV range could
solve several long-standing astrophysical puzzles, from supernova asymmetries
and the pulsar kicks to star formation, reionization, and baryogenesis. The
best current limits on sterile neutrinos come from Chandra and XMM-Newton.
Future advances can be achieved with a high-resolution x-ray spectrometry in
space.


title: HI in XMD Galaxies III. GMRT observations of BCG HS0822+3542

abstract:
  We present Giant Metrewave Radio Telescope (GMRT) HI 21-cm line data for the
smallest known eXtremely Metal Deficient (XMD) blue compact galaxy (BCG)
HS0822+3542. From HST imaging it has been suggested that HS0822+3542 actually
consists of two still smaller (~ 100pc sized) ultra-compact dwarfs that are in
the process of merging. The brighter of these two putative ultra compact dwarfs
has an ocular appearance, similar to that seen in galaxies that have suffered a
penetrating encounter with a smaller companion. From our HI imaging we find
that the gas distribution and kinematics in this object are similar to that of
other low mass galaxies, albeit with some evidence for tidal disturbance. On
the other hand, the HI emission has an angular size ~25 times larger than that
of the putative ultra-compact dwarfs. The optical emission is also offset from
the centre of the HI emission. HS0822+3542 is located in the Lynx-Cancer void,
but has a nearby companion LSB dwarf galaxy SAO0822+3545. In light of all this
we also consider a scenario where the optical emission from HS0822+3542 comes
not from two merging ultra-compact dwarfs but from multiple star forming
regions in a tidally disturbed galaxy. In this model, the ocular appearance of
the brighter star forming region could be the result of triggered star
formation.


title: Intrinsic short time scale variability of W3(OH) maser

abstract:
  We have studied the OH masers in the star forming region, W3(OH), with data
obtained from the Very Long Baseline Array (VLBA). The data provide an angular
resolution of $\sim$5 mas, and a velocity resolution of 106 m s$^{-1}$. A novel
analysis procedure allows us to differentiate between broadband temporal
intensity fluctuations introduced by instrumental gain variations plus
interstellar diffractive scintillation, and intrinsic narrowband variations.
Based on this 12.5 hours observation, we are sensitive to variations with time
scales of minutes to hours. We find statistically significant intrinsic
variations with time scales of $\sim$15--20 minutes or slower, based on the
{\it velocity-resolved fluctuation spectra}. These variations are seen
predominantly towards the line shoulders. The peak of the line profile shows
little variation, suggesting that they perhaps exhibit saturated emission. The
associated modulation index of the observed fluctuation varies from
statistically insignificant values at the line center to about unity away from
the line center. Based on light-travel-time considerations, the 20-minute time
scale of intrinsic fluctuations translates to a spatial dimension of $\sim$2--3
AU along the sight-lines. On the other hand, the transverse dimension of the
sources, estimated from their observed angular sizes of about $\sim$3 mas, is
about 6 AU. We argue that these source sizes are intrinsic, and are not
affected by interstellar scatter broadening. The implied peak brightness
temperature of the 1612/1720 maser sources is about $\sim2\times 10^{13}$ K,
and a factor of about five higher for the 1665 line.


title: 2MASS J05162881+2607387: A New Low-Mass Double-Lined Eclipsing Binary

abstract:
  We show that the star known as 2MASS J05162881+2607387 (hereafter J0516) is a
double-lined eclipsing binary with nearly identical low-mass components. The
spectroscopic elements derived from 18 spectra obtained with the High
Resolution Spectrograph on the Hobby-Eberly Telescope during the Fall of 2005
are K_1=88.45 +/- 0.48 km/s and K_2=90.43 +/- 0.60 km/s, resulting in a mass
ratio of$q=K_1/K_2 = 0.978 +/- 0.018 and minimum masses of M_1 sin^{3}i=0.775
+/- 0.016 solar masses and M_2 sin^{3}i=0.759 +/- 0.012 solar masses,
respectively. We have extensive differential photometry of J0516 obtained over
several nights between 2004 January-March (epoch 1) and 2004 October-2005
January plus 2006 January (epoch 2) using the 1m telescope at the Mount Laguna
Observatory. The source was roughly 0.1 mag brighter in all three bandpasses
during epoch 1 when compared to epoch 2. Also, phased light curves from epoch 1
show considerable out-of-eclipse variability, presumably due to bright spots on
one or both stars. In contrast, the phased light curves from epoch 2 show
little out-of-eclipse variability. The light curves from epoch 2 and the radial
velocity curves were analyzed using our ELC code with updated model atmospheres
for low-mass stars. We find the following: M_1=0.787 +/- 0.012 solar masses,
R_1=0.788 +/- 0.015 solar radii, M_2=0.770 +/- 0.009 solar masses, and
R_2=0.817 +/- 0.010 solar radii. The stars in J0516 have radii that are
significantly larger than model predictions for their masses, similar to what
is seen in a handful of other well-studied low-mass double-lined eclipsing
binaries. We compiled all recent mass and radius determinations from low-mass
binaries and determine an empirical mass-radius relation of the form R = 0.0324
+ 0.9343M + 0.0374M^2, where the quantities are in solar units.


title:
ASTE Observations of Warm Gas in Low-mass Protostellar Envelopes:
  Different Kinematics between Submillimeter and Millimeter Lines

abstract:
  With the ASTE telescope, we have made observations of three low-mass
protostellar envelopes around L483, B335, and L723 in the submillimeter CS
($J$=7--6) and HCN ($J$=4--3) lines. We detected both the CS and HCN lines
toward all the targets, and the typical CS intensity ($\sim$ 1.0 K in T$_{B}$)
is twice higher than that of the HCN line. Mapping observations of L483 in
these lines have shown that the submillimeter emissions in the low-mass
protostellar envelope are resolved, exhibit a western extension from the
central protostar, and that the deconvolved size is $\sim$ 5500 AU $\times$
3700 AU (P.A. = 78$^{\circ}$) in the HCN emission. The extent of the
submillimeter emissions in L483 implies the presence of higher-temperature
($\gtrsim$ 40 K) gas at 4000 AU away from the central protostar, which suggests
that we need to take 2-dimensional radiative transfer models with a flattened
disklike envelope and bipolar cavity into account to explain the temperature
structure inside the low-mass protostellar envelope. The position-velocity
diagrams of these submillimeter lines in L483 and B335 exhibit different
velocity gradients from those found in the previous millimeter observations. In
particular, along the axis of the associated molecular outflow the sense of the
velocity gradient traced by the submillimeter lines is opposite to that of the
millimeter observations or the associated molecular outflow, both in L483 and
B335. We suggest that expanding gas motions at the surface of the flattened
disklike envelope around the protostar, which is irradiated from the central
star directly, are the origin of the observed submillimeter velocity structure.


title:
Characteristics of geomagnetic cascading of ultra-high energy photons at
  the southern and northern sites of the Pierre Auger Observatory

abstract:
  Cosmic-ray photons above 10^19 eV can convert in the geomagnetic field and
initiate a preshower, i.e. a particle cascade before entering the atmosphere.
We compare the preshower characteristics at the southern and northern sites of
the Pierre Auger Observatory. In addition to a shift of the preshower patterns
on the sky due to the different pointing of the local magnetic field vectors,
the fact that the northern Auger site is closer to the geomagnetic pole results
in a different energy dependence of the preshower effect: photon conversion can
start at smaller energies, but large conversion probabilitites (>90%) are
reached for the whole sky at higher energies compared to the southern Auger
site. We show how the complementary preshower features at the two sites can be
used to search for ultra-high energy photons among cosmic rays. In particular,
the different preshower characteristics at the northern Auger site may provide
an elegant and unambiguous confirmation if a photon signal is detected at the
southern site.


title: Extremely Red Objects in Two Quasar Fields at z ~ 1.5

abstract:
  We present an investigation of the properties and environments of bright
extremely red objects (EROs) found in the fields of the quasars TXS 0145+386
and 4C 15.55, both at z ~ 1.4. There is marginal evidence from Chandra ACIS
imaging for hot cluster gas with a luminosity of a few 10^44 ergs/s in the
field of 4C 15.55. The TXS 0145+386 field has an upper limit at a similar
value, but it also clearly shows an overdensity of faint galaxies. None of the
EROs are detected as X-ray sources. For two of the EROs that have
spectral-energy distributions and rest-frame near-UV spectra that show that
they are strongly dominated by old stellar populations, we determine
radial-surface-brightness profiles from adaptive-optics images. Both of these
galaxies are best fit by profiles close to exponentials, plus a compact nucleus
comprising ~30% of the total light in one case and 8% in the other. Neither is
well fit by an r^1/4-law profile. This apparent evidence for the formation of
massive ~2 X 10^11 disks of old stars in the early universe indicates that at
least some galaxies formed essentially monolithically, with high star-formation
rates sustained over a few 10^8 years, and without the aid of major mergers.


title: Relaxed constraints on neutrino oscillation parameters

abstract:
  We study the cosmological constraints on active-sterile neutrino oscillations
nu_e <-> nu_s for the case when nu_s is partially filled initially, i.e. 0 <
delta N_s < 1. We provide numerical analysis of the cosmological production of
He-4, in the presence of nu_e <-> nu_s oscillations, effective after neutrino
decoupling, accounting for all known oscillations effects on cosmological
nucleosynthesis. Cosmological constraints on oscillation parameters
corresponding to higher than 5% He-4 overproduction and different non-zero
initial populations of the sterile state delta N_s < 1 are calculated. These
generalized cosmological constraints corresponding to delta N_s > 0 are relaxed
in comparison with the delta N_s = 0 case and the relaxation is proportional to
delta N_s.


title: If Gauss-Bonnet interaction plays the role of dark energy

abstract:
  Gauss-Bonnet-scalar interaction has been found to play a crucial role from
the beginning till the late time of cosmological evolution. A cosmological
model has been constructed where the Universe starts with exponential expansion
but with infinite deceleration (q), and infinite equation of state (w)
parameters. During evolution it passes through the stiff fluid era, q=2, w=1,
the radiation dominated era, q=1, w=1/3 and the matter dominated era, q=1/2,
w=0. Finally, deceleration halts, q=0, w=-1/3, and it then encounters a
transition to the accelerating phase. Asymptotically the Universe reaches yet
another inflationary phase as q and w go over to -1. Such evolution is
independent of the form of the potential and the sign of the kinetic energy
term ie., even a noncanonical kinetic energy is unable to phantomize (w<-1) the
model.


title:
Probing isotopic ratios at z = 0.89: molecular line absorption in front
  of the quasar PKS 1830-211

abstract:
  With the Plateau de Bure interferometer, we have measured the C, N, O and S
isotopic abundance ratios in the arm of a spiral galaxy with a redshift of
0.89. The galaxy is seen face-on according to HST images. Its bulge intercepts
the line of sight to the radio-loud quasar PKS 1830-211, giving rise at mm
wavelengths to two Einstein images located each behind a spiral arm. The arms
appear in absorption in the lines of several molecules, giving the opportunity
to study the chemical composition of a galaxy only a few Gyr old. The isotopic
ratios in this spiral galaxy differ markedly from those observed in the Milky
Way. The $^{17}$O/$^{18}$O and $^{14}$N/$^{15}$N ratios are low, as one would
expect from an object too young to let low mass stars play a major role in the
regeneration of the gas.


title:
A high-resolution spectral analysis of three carbon-enhanced metal-poor
  stars

abstract:
  We present results of an analysis of high-resolution spectra obtained with
the Subaru Telescope High Dispersion Spectrograph, of two Carbon-Enhanced
Metal-Poor stars, HE 1305+0007 and HE 1152-0355, and of the classical CH star
HD 5223. All of these stars have relatively low effective temperatures
(4000-4750 K) and high carbon abundances. The stellar atmospheric parameters
indicate that they all have surface gravities consistent with a present
location on the red-giant branch, and metallicities of [Fe/H] = -2.0 (HE
1305+0007, HD 5223) and [Fe/H]= -1.3 (HE 1152-0355). In addition to their large
enhancements of carbon all three stars exhibit strong enhancements of the
s-process elements relative to iron. HE 1305+0007 exhibits a large enhancement
of the 3rd-peak s-process element lead, with [Pb/Fe] = +2.37, as well as a high
abundance of the r-process element europium, [Eu/Fe] = +1.97. Thus, HE
1305+0007 joins the growing class of the so-called ``Lead Stars'', and also the
class of objects that exhibit the presence of both r-process and s-process
elements, the CEMP-r/s stars. The large enhancement of n-capture elements
exhibited by HE 1152-0355 and HD 5223 are more consistent with the abundance
patterns generally noticed in CH stars. The elemental abundance distributions
observed in these stars are discussed in the light of existing theories of CH
star formation, as well as the suggested formation scenarios of the CEMP-r/s
group.


title: Determination of the atmospheric neutrino fluxes from experimental data

abstract:
  The precise knowledge of the atmospheric neutrino fluxes is a key ingredient
in the interpretation of the results from any atmospheric neutrino experiment.
In the standard atmospheric neutrino data analysis, these fluxes are
theoretical inputs obtained from sophisticated numerical calculations. In this
contribution we present an alternative approach to the determination of the
atmospheric neutrino fluxes based on the direct extraction from the
experimental data on neutrino event rates.


title:
The "Principes de Asturias" nebula: a new quadrupolar planetary nebula
  from the IPHAS survey

abstract:
  The Isaac Newton Telescope Photometric H-alpha Survey (IPHAS) is currently
mapping the Northern Galactic plane reaching to r'=20 mag with typically 1"
resolution. Hundreds of Planetary Nebulae (PNe), both point-like and resolved,
are expected to be discovered. We report on the discovery of the first new PN
from this survey: it is an unusual object located at a large galactocentric
distance and has a very low oxygen abundance. The nebula shows an intricate
morphology: there is an inner ring surrounding the central star, bright inner
lobes with an enhanced waist, and very faint lobular extensions reaching up to
more than 100". We classify it as a quadrupolar PN, a rather unusual class of
planetary showing two pairs of misaligned lobes. From long-slit spectroscopy we
derive Te[NII] =12800+-1000K, Ne = 390+-40 cm-3, and chemical abundances
typical of Peimbert's Type I nebulae (He/H =0.13, N/O =1.8) with an oxygen
abundance of 12 + log(O/H)=8.17+-0.15. A kinematic distance of 7.0 kpc is
derived, implying an unusually large size of >4 pc for the nebula. The
photometry of the central star indicates the presence of a relatively cool
companion. This, and the evidence for a dense circumstellar disk and
quadrupolar morphology, all of which are rare among PNe, support the hypothesis
that this morphology is related to binary interaction.


title:
Solar Mean Magnetic Field Near the Surface and its Variation During a
  Cycle

abstract:
  The unsigned mean magnetic field characterizes the magnetic energy settled in
the region near the solar surface. It is one of the determinant ingredients
that govern the turbulence in the photosphere, and the magnetic heating of
upper layers. The acoustic eigenmodes are directly sensitive to this mean
magnetic energy, via the magnetic pressure, and thanks to their trajectories
sweeping entirely this region. We use the local-wave formalism to calculate the
p-mode frequencies of the Saclay seismic solar model. Then, by comparing them
to the LOWL observed frequencies, the l-independent differences (up to 40
microHz) can be attributed to the existence of a magnetic pressure that
modifies the pressure, the density and the sound speed, taking also into
account the additional Alfven speed. A profile of unsigned mean magnetic field
is deduced, increasing from zero at the surface to 2.5e4 G, 5600 km deeper.
Next, by applying the same method, the l-independent variations in frequency
due the solar cycle (up to 0.4 microHz) is used to deduce the change of the
magnetic profile. This change presents two distinctive parts: a plateau of only
2-3 G from the surface down to 2100 km, and a very narrow peak of 55 G, 220 km
thick, right at the surface. Due to the non-linear effect of the magnetic
field, comparing only the frequencies between minimum and maximum activity is
not sufficient to deduce the magnetic variation. The additional knowledge of
the magnetic field at minimum activity is necessary. If the latter is ignored,
an extra variation of up to 130 G would be found. Finally, our results are
compared to magnetic field estimates by other helioseismic and spectroscopic
methods.


title:
A Simple Analytic Treatment of the Intergalactic Absorption Effect in
  Blazar Gamma-ray Spectra

abstract:
  We derive a new and user friendly simple analytic approximation for
determining the effect of intergalactic absorption in the energy range 0.2-2
TeV and the redshift range 0.05-0.4. In these ranges, the form of the
absorption coeeficient is approximately logarithmic in energy. The effect of
this energy dependence is to steepen intrinsic source spectra such that a
source with an approximate power-law intrinsic spectrum in this energy range
with spectral index $\Gamma_{s}$ is steepened to a power-law with an observed
spectral index $\Gamma_{o} = $\Gamma_{s} + $\Delta \Gamma (z)$ where $\Delta
\Gamma (z)$ is a linear function of z in the redshift range 0.05-0.4. We apply
this approximation to the spectra of seven TeV blazars.


title:
The Unusual Cataclysmic Binary Star RBS 0490 and the Space Density of
  Cataclysmics

abstract:
  RBS (Rosat Bright Source) 0490 is a cataclysmic variable star (CV) with
unusually strong emission lines. The strength of the emission lines led to a
suggestion that the object is intrinsically faint and correspondingly nearby
(approx. 33 pc), which, if true, would strongly affect estimates of the CV
space density. Here we report astrometry, filter photometry, and time-series
spectroscopy of this object. The astrometry gives an absolute parallax pi(abs)
= 4.5 +- 1.5 mas and a relative proper motion of 102 mas/yr. A Bayesian
procedure gives a very uncertain distance estimate of d approx. 300 pc, and the
small parallax alone implies d > 133 pc (at two standard deviations). The mean
V magnitude is 17.4, which implies M_V = 10.9 - 5 log (d/200 pc), neglecting
extinction. At 200 pc, the space velocity would be over 90 km/s with respect to
the LSR. The time-series spectroscopy shows a possible emission-line
radial-velocity period near 46 min. This would be unusually short for an
orbital period and it may represent some other clock in the system.


title:
First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor
  stars

abstract:
  From high-resolution VLT/UVES spectra (R~43,000), we determine abundances or
upper limits for Li, C, N, O, and other important elements, as well as 12C/13C
isotopic ratio for three Carbon enhanced metal poor stars. All three stars have
-3.30 <= [Fe/H] <= -2.85 and moderate to high CNO abundances. CS 22958-042 is
one of the most carbon-rich CEMP stars known ([C/Fe] = +3.2), while CS
29528-041 (one of the few N-enhanced metal-poor stars known) is one of the most
nitrogen rich ([N/Fe] = +3.0). Oxygen is very high in CS 31080-095 ([O/Fe] =
+2.35) and in CS 22958-042 ([O/Fe] = +1.35). All three stars exhibit [Sr/Fe] <
0; Ba is not detected in CS 22958-042 ([Ba/Fe] < -0.53), but it is moderately
enhanced ([Ba/Fe] ~ 1) in the other two stars. CS 22958-042 displays one of the
largest sodium overabundances yet found in CEMP stars ([Na/Fe] = +2.8). CS
22958-042 has 12C/13C = 9, similar to most other CEMP stars without enhanced
neutron-capture elements, while 12C/13C <= 40 in CS 31080-095. CS 31080-095 and
CS 29528-041 have A(Li) ~ 1.7, below the Spite Plateau, while Li is not
detected in CS 22958-042. CS 22958-042 is a CEMP-no star, but the other two
stars are in no known class of CEMP star and thus either constitute a new class
or are a link between the CEMP-no and CEMP-s classes, adding complexity to the
abundance patterns for CEMP stars. We interpret the abundance patterns in our
stars to imply that current models for the presumed AGB binary progenitors lack
an extra-mixing process, similar to those apparently operating in RGB stars.


title:
The Diffuse Interstellar Bands: A Major Problem in Astronomical
  Spectroscopy

abstract:
  A critical review of the very long-standing problem of the diffuse
interstellar bands is presented with emphasis on spectroscopic aspects of
observational, modelling and laboratory-based research. Some research themes
and ideas that could be explored theoretically and experimentally are
discussed. The article is based on the Journal of Molecular Spectroscopy Review
Lecture presented at the 60th Ohio State University International Symposium on
Molecular Spectroscopy, June 2005.


title: The Correlation Dimension of Young Stars in Dwarf Galaxies

abstract:
  We present the correlation dimension of resolved young stars in four actively
star-forming dwarf galaxies that are sufficiently resolved and transparent to
be modeled as projections of three-dimensional point distributions. We use data
in the Hubble Space Telescope archive; photometry for one of them, UGCA 292, is
presented here for the first time. We find that there are statistically
distinguishable differences in the nature of stellar clustering among the
sample galaxies. The young stars of VII Zw 403, the brightest galaxy in the
sample, have the highest value for the correlation dimension and also the most
dramatic decrease with logarithmic scale, falling from $1.68\pm0.14$ to
$0.10\pm0.05$ over less than a factor of ten in $r$. This decrease is
consistent with the edge effect produced by a projected Poisson distribution
within a 2:2:1 ellipsoid. The young stars in UGC 4483, the faintest galaxy in
the sample, exhibit very different behavior, with a constant value of about 0.5
over this same range in $r$, extending nearly to the edge of the distribution.
This behavior may indicate either a scale-free distribution with an unusually
low correlation dimension, or a two-component (not scale-free) combination of
cluster and field stars.


title:
A Deep Proper-Motion Survey in Kapteyn Selected Areas: I. Survey
  Description and First Results for Stars in the Tidal Tail of Sagittarius and
  in the Monoceros Ring

abstract:
  We describe a high-precision, deep (to V ~ 19-21) absolute proper-motion
survey that samples ~50 lines of sight in the Kapteyn Selected Areas along
declination zones -15, 0 and 15 degrees. In many fields the astrometric
baseline reaches nearly a century. We demonstrate that these data provide
typical per star precisions between ~ 1 and 3 mas/yr to the above magnitude
limits, with the absolute reference frame established by numerous extragalactic
sources in each survey field. Combined with existing and ongoing photometric
and radial velocity surveys in these fields, these astrometric data will
enable, among other things, accurate, detailed dynamical modeling of satellite
interactions with our Galaxy. In this contribution we describe the astrometric
part of our survey and show preliminary results along the trailing tail of the
Sagittarius dwarf galaxy, and in the Monoceros ring region.


title: The isocurvature fraction after WMAP 3-year data

abstract:
  I revisit the question of the adiabaticity of initial conditions for
cosmological perturbations in view of the 3-year WMAP data. I focus on the
simplest alternative to pure adiabatic conditions, namely a superposition of
the adiabatic mode and one of the 3 possible isocurvature modes, with the same
spectral index as the adiabatic component.
  I discuss findings in terms of posterior bounds on the isocurvature fraction
and Bayesian model selection. The Bayes factor (models likelihood ratio) and
the effective Bayesian complexity are computed for several prior ranges for the
isocurvature content. I find that the CDM isocurvature fraction is now
constrained to be less than about 10%, while the fraction in either the
neutrino entropy or velocity mode is below about 20%. Model comparison strongly
disfavours mixed models that allow for isocurvature fractions larger than
unity, while current data do not allow to distinguish between a purely
adiabatic model and models with a moderate (ie, below about 10%) isocurvature
contribution.
  The conclusion is that purely adiabatic conditions are strongly favoured from
a model selection perspective. This is expected to apply in even stronger terms
to more complicated superpositions of isocurvature contributions.


title:
Hydrogen and helium line formation in OB dwarfs and giants. A hybrid
  non-LTE approach

abstract:
  Aims: Hydrogen and helium line spectra are crucial diagnostic features for
the quantitative analysis of OB stars. We compute synthetic spectra based on a
hybrid non-LTE approach in order to test the ability of these models to
reproduce high-resolution and high-S/N spectra of dwarf and giant stars and
also to compare them with published grids of non-LTE (OSTAR2002) and LTE
(Padova) models. Methods: Our approach solves the restricted non-LTE problem
based on classical line-blanketed LTE model atmospheres. State-of-the-art model
atoms and line-broadening theories are employed to model the H and He I/II
spectra over the entire optical range and in the near-IR. Results: The
synthetic spectra match almost all measurable hydrogen and helium lines
observed in six test stars over a wide spectral range from the Balmer limit to
the NIR, except for only a few well-understood cases. Our approach reproduces
other published non-LTE calculations, however avoids inconsistencies with the
modelling of the He I singlets recently discussed in the literature. It
improves on the published LTE models in many aspects: non-LTE strengthening and
the use of improved line-broadening data result in overall significant
differences in the line profiles and equivalent widths of the Balmer and helium
lines. Where possible, systematic effects on the stellar parameter
determination are quantified, e.g. gravities derived from the Hgamma wings may
be overestimated by up to ~0.2 dex at our upper temperature boundary in LTE.
(abridged)


title:
The Optimum Distance at which to Determine the Size of a Giant Air
  Shower

abstract:
  To determine the size of an extensive air shower it is not necessary to have
knowledge of the function that describes the fall-off of signal size from the
shower core (the lateral distribution function). In this paper an analysis with
a simple Monte Carlo model is used to show that an optimum ground parameter can
be identified for each individual shower. At this optimal core distance,
$r_\mathrm{opt}$, the fluctuations in the expected signal, $S(r_\mathrm{opt})$,
due to a lack of knowledge of the lateral distribution function are minimised.
Furthermore it is shown that the optimum ground parameter is determined
primarily by the array geometry, with little dependence on the energy or zenith
angle of the shower or choice of lateral distribution function. For an array
such as the Pierre Auger Southern Observatory, with detectors separated by 1500
m in a triangular configuration, the optimum distance at which to measure this
characteristic signal is close to 1000 m.


title:
The Advantage of Increased Resolution in the Study of Quasar Absorption
  Systems

abstract:
  We compare a new R = 120,000 spectrum of PG1634+706 (z_QSO = 1.337,m_V =
14.9) obtained with the HDS instrument on Subaru to a R = 45, 000 spectrum
obtained previously with HIRES/Keck. In the strong MgII system at z = 0.9902
and the multiple cloud, weak MgII system at z = 1.0414, we find that at the
higher resolution, additional components are resolved in a blended profile. We
find that two single-cloud weak MgII absorbers were already resolved at R =
45,000, to have b = 2 - 4 km/s. The narrowest line that we measure in the R =
120, 000 spectrum is a component of the Galactic NaI absorption, with b =
0.90+/-0.20 km/s. We discuss expectations of similarly narrow lines in various
applications, including studies of DLAs, the MgI phases of strong MgII
absorbers, and high velocity clouds. By applying Voigt profile fitting to
synthetic lines, we compare the consistency with which line profile parameters
can be accurately recovered at R = 45,000 and R = 120,000. We estimate the
improvement gained from superhigh resolution in resolving narrowly separated
velocity components in absorption profiles. We also explore the influence of
isotope line shifts and hyperfine splitting in measurements of line profile
parameters, and the spectral resolution needed to identify these effects. Super
high resolution spectra of quasars, which will be routinely possible with
20-meter class telescopes, will lead to greater sensitivity for absorption line
surveys, and to determination of more accurate physical conditions for cold
phases of gas in various environments.


title: Free-bound emission from cosmological hydrogen recombination

abstract:
  In this paper we compute the emission coming from the direct recombination of
free electrons to a given shell (n>=2) during the epoch of cosmological
hydrogen recombination. This contribution leads to a total of one photon per
recombined hydrogen atom and therefore a ~30-88% increase of the recombination
spectrum within the frequency range 1 GHz<=nu<=100 GHz. In particular the
Balmer-continuum emission increases the distortion at nu~ 690 GHz by ~92%. With
our 100 shell calculations for the hydrogen atom we find that a total of ~5
photons per hydrogen atom are emitted when including all the bound-bound
transitions, the 2s two-photon decay channel and the optically thin free-bound
transitions. Since the direct recombination continuum at high n is very broad
only a few n-series continuua are distinguishable and most of this additional
emission below nu<~30 GHz is completely featureless.


title: Enhanced density and magnetic fields in interstellar OH masers

abstract:
  Aims: We have observed the 6030 and 6035 MHz transitions of OH in high-mass
star-forming regions to obtain magnetic field estimates in both maser emission
and absorption.
  Methods: Observations were taken with the Effelsberg 100 m telescope.
  Results: Our observations are consistent with previous results, although we
do detect a new 6030 MHz maser feature near -70 km/s in the vicinity of W3(OH).
In absorption we obtain a possible estimate of -1.1 +/- 0.3 mG for the average
line-of-sight component of the magnetic field in the absorbing OH gas in K3-50
and submilligauss upper limits for the line-of-sight field strength in DR 21
and W3.
  Conclusions: These results indicate that the magnetic field strength in the
vicinity of OH masers is higher than that of the surrounding, non-masing
material, which in turn suggests that the density of masing OH regions is
higher than that of their surroundings.


title: Satellite Accretion Onto Massive Galaxies With Central Black Holes

abstract:
  Minor mergers of galaxies are expected to be common in a hierarchical
cosmology such as $\Lambda$CDM and have the potential to significantly affect
galactic structure. In this paper we dissect the case-by-case outcome from a
set of numerical simulations of a single satellite elliptical galaxy accreting
onto a massive elliptical galaxy. We take care to explore cosmologically
relevant orbital parameters and to set up realistic initial galaxy models that
include all three relevant dynamical components: dark matter halos, stellar
bulges, and central massive black holes. The effects of several different
parameters are considered, including orbital energy and angular momentum,
satellite density and inner density profile, satellite-to-host mass ratio, and
presence of a black hole at the center of the host. Black holes play a crucial
role in protecting the shallow stellar cores of the hosts, as satellites
merging onto a host with a central black hole are more strongly disrupted than
those merging onto hosts without black holes. Orbital parameters play an
important role in determining the degree of disruption: satellites on less
bound or more eccentric orbits are more easily destroyed than those on more
bound or more circular orbits as a result of an increased number of pericentric
passages and greater cumulative effects of gravitational shocking and tidal
stripping. In addition, satellites with densities typical of faint elliptical
galaxies are disrupted relatively easily, while denser satellites can survive
much better in the tidal field of the host. Over the range of parameters
explored, we find that the accretion of a single satellite elliptical galaxy
can result in a broad variety of changes, in both signs, in the surface
brightness profile and color of the central part of an elliptical galaxy.


title:
Accretion-Ejection Instability, MHD Rossby Wave Instability,
  diskoseismology, and the high-frequency QPO of microquasars

abstract:
  We present a possible explanation for the high-frequency Quasi-Periodic
Oscillations of microquasars by an MHD instability that combines the physics
developed, in different contexts, for the Accretion-Ejection Instability, the
Rossby-Wave Instability, and the normal modes of diskoseismic models (which
rely on the properties of the relativistic rotation curve in the vicinity of
the Marginally Stable Orbit). This instability can appear as modes of azimuthal
wavenumbers m=2, 3,... that have very similar pattern speeds \omega/m, while
the m=1 mode, which would appear as the fundamental of this discrete spectrum,
is less unstable. This would readily explain the 2:3 (and sometimes higher)
frequency ratio observed between these QPO. These instabilites form eigenmodes,
i.e. standing wave patterns at a constant frequency in the disk; they are
strongly unstable, and thus do not need an external excitation mechanism to
reach high amplitudes. Furthermore, they have the property that a fraction of
the accretion energy can be emitted toward the corona: this would explain that
these QPO are seen in a spectral state where Comptonized emission from the
corona is always present. Their existence depends critically on the existence
of a magnetic structure, formed by poloidal flux advected in the accretion
process, in the central region between the disk and the black hole.


title: Spectral Line Selection for HMI: A Comparison of Fe I 6173 and Ni I 6768

abstract:
  We present a study of two spectral lines, Fe I 6173 Angstroms and Ni I 6768
Angstroms, that were candidates to be used in the Helioseismic and Magnetic
Imager (HMI) for observing Doppler velocity and the vector magnetic field. The
line profiles were studied using the Mt. Wilson Observatory, the Advanced
Stokes Polarimeter and the Kitt Peak McMath telescope and one meter Fourier
transform spectrometer atlas. Both Fe I and Ni I profiles have clean continua
and no blends that threaten instrument performance. The Fe I line is 2% deeper,
15% narrower and has a 6% smaller equivalent width than the Ni I line. The
potential of each spectral line to recover pre-assigned solar conditions is
tested using a least-squares minimization technique to fit Milne-Eddington
models to tens of thousands of line profiles that have been sampled at five
spectral positions across the line. Overall, the Fe I line has a better
performance than the Ni I line for vector magnetic field retrieval. We selected
the Fe I spectral line for use in HMI due to its better performance for
magnetic diagnostics while not sacrificing velocity information.


title:
Performance Analysis of Direct N-Body Algorithms on Special-Purpose
  Supercomputers

abstract:
  Direct-summation N-body algorithms compute the gravitational interaction
between stars in an exact way and have a computational complexity of O(N^2).
Performance can be greatly enhanced via the use of special-purpose accelerator
boards like the GRAPE-6A. However the memory of the GRAPE boards is limited.
Here, we present a performance analysis of direct N-body codes on two parallel
supercomputers that incorporate special-purpose boards, allowing as many as
four million particles to be integrated. Both computers employ high-speed,
Infiniband interconnects to minimize communication overhead, which can
otherwise become significant due to the small number of "active" particles at
each time step. We find that the computation time scales well with processor
number; for 2*10^6 particles, efficiencies greater than 50% and speeds in
excess of 2 TFlops are reached.


title:
The Role of Sub-damped Lyman-alpha Absorbers in the Cosmic Evolution of
  Metals

abstract:
  Observations of low mean metallicity of damped Lyman-alpha (DLA) quasar
absorbers at all redshifts studied appear to contradict the predictions for the
global mean interstellar metallicity in galaxies from cosmic chemical evolution
models. On the other hand, a number of metal-rich sub-DLA systems have been
identified recently, and the fraction of metal-rich sub-DLAs appears to be
considerably larger than that of metal-rich DLAs, especially at z < 1.5. In
view of this, here we investigate the evolution of metallicity in sub-DLAs. We
find that the mean Zn metallicity of the observed sub-DLAs may be higher than
that of the observed DLAs, especially at low redshifts, reaching a near-solar
level at z <~ 1. This trend does not appear to be an artifact of sample
selection, the use of Zn, the use of N_{HI}-weighting, or observational
sensitivity. While a bias against very low metallicity could be present in the
sub-DLA sample in some situations, this cannot explain the difference between
the DLA and sub-DLA metallicities at low z. The primary reason for the
difference between the DLAs and sub-DLAs appears to be the dearth of metal-rich
DLAs. We estimate the sub-DLA contribution to the total metal budget using
measures of their metallicity and comoving gas density. These calculations
suggest that at z <~ 1, the contribution of sub-DLAs to the total metal budget
may be several times that of DLAs. At higher redshifts also, there are
indications that the sub-DLAs may contribute significantly to the cosmic metal
budget.


title: The nature of damped Lyman alpha and sub-damped Lyman alpha absorbers

abstract:
  We present arguments based on the measured abundances in individual damped
Lyman alpha systems (DLAs) and sub-damped Lyman alpha systems (sub-DLAs), and
also the average abundances inferred in large samples of QSO absorption line
systems, to suggest that the amount of dust in intervening QSO absorbers is
small and is not responsible for missing many QSOs in magnitude limited QSO
surveys. While we can not totally rule out a bimodal dust distribution with a
population of very dusty, metal rich, absorbers which push the background QSOs
below the observational threshold of current optical spectroscopic studies,
based upon the current samples it appears that the metallicity in QSO absorbers
decreases with increase in H I column densities beyond 10^{19} cm^{-2}. Thus
the sub-DLA population is more metal rich than the DLAs, a trend which may
possibly extend to the non-damped Lyman limit systems (NDLLS). Based on the
recently discovered mass-metallicity relation for galaxies, we suggest that
most sub-DLAs and possibly NDLLS, are associated with massive spiral/elliptical
galaxies while most DLAs are associated with low mass galaxies. The sub-DLA
galaxies will then contribute a larger fraction of total mass (stellar and ISM)
and therefore metals, to the cosmic budget, specially at low redshifts, as
compared to the DLAs.


title: Optical observations of Be/X-ray transient system KS 1947+300

abstract:
  ROTSE-IIId observations of the Be/X-ray transient system KS 1947+300 obtained
between September 2004 and December 2005 make it possible to study the
correlation between optical and X-ray activity. The optical outburst of 0.1 mag
was accompanied by an increase in X-ray flux in 2004 observations. Strong
correlation between the optical and X-ray light curves suggests that neutron
star directly accretes from the outflowing material of Be star. The nearly zero
time lag between X-ray and optical light curves suggests a heating of the disk
of Be star by X-rays. No optical brightening and X-ray enhancement was seen in
2005 observations. There is no indication of the orbital modulation in the
optical light curve.


title:
Cleaned Three-Year WMAP CMB Map: Magnitude of the Quadrupole and
  Alignment of Large Scale Modes

abstract:
  [Abridged] We have produced a cleaned map of the Wilkinson Microwave
Anisotropy Probe (WMAP) 3-year data using an improved foreground subtraction
technique. We perform an internal linear combination (ILC) to subtract the
Galactic foreground emission from the temperature fluctuations observed by the
WMAP. We divide the whole sky into hundreds of pixel groups with similar
foreground spectral indices over a range of WMAP frequencies, apply the ILC for
each group, and obtain a CMB map with foreground emission effectively reduced.
With the resulting foreground-reduced ILC map, we have investigated the known
anomalies in CMB maps at large scales. The quadrupole and the octopole powers
measured from our ILC map are \delta T_2^2 = 276_{-126}^{+94} uK^2 and \delta
T_3^2 = 952_{-83}^{+64} uK^2, respectively. The measured quadrupole power is
lower than the value expected in the concordance LCDM model (1250 uK^2), in
which the probability of finding a quadrupole power lower than the measured
value is 5.7%. We have confirmed that the quadrupole and the octopole are
strongly aligned with angle \theta_{23} = 11.8_{-8.0}^{+6.4} degree, and are
planar with high planarity parameters t=0.98_{-0.02}^{+0.02} for l=2 and
t=0.91_{-0.03}^{+0.02} for l=3. The observed angular separation \theta_{23} is
marginally statistically significant because the probability of finding the
angular separation as low as the observed value is 4.3%. However, the observed
planarity is not statistically significant. The probability of observing such a
planarity as high as the measured t values is over 18%. The ILC simulations
show that the residual foreground emission in the ILC map does not affect the
estimated values significantly.


title: Star formation rate in the solar neighborhood

abstract:
  This thesis develops a method for obtaining the star formation histories of a
mixed, resolved population through the use of color-magnitude diagrams (CMDs).
The method is applied to the derivation of the local star formation rate,
modeling observations of the Hipparcos satellite wigth synthetic CMDs computed
for different star formation histories with an updated stellar evolution
library. Parallax and photometric uncertainties are included explicitly and
corrected using the Bayesian Richardson-Lucy algorithm. We find that the solar
neighborhood star formation rate has a characteristic timescale for variation
of about 6 Gyr, with a maximum activity close to 3 Gyr ago. This suggests a
global, rather than local, star forming event. The summary and conclusions are
included here, the full thesis is available at the URL listed above.


title:
Stellar and gaseous velocity dispersions in type II AGNs at 0.3<z<0.83
  from the Sloan Digital Sky Survey

abstract:
  We apply the stellar population synthesis code by Cid Fernandes et al. to
model the stellar contribution for a sample of 209 type II AGNs at $0.3<z<0.83$
from the Sloan Digital Sky Survey. The reliable stellar velocity dispersions
($\sigma_{*}$) are obtained for 33 type II AGNs with significant stellar
absorption features. According to the $L_{\rm [O III]}$ criterion of $3\times
10^{8} \Lsolar$, 20 of which can be classified as type II quasars. We use the
formula of Greene & Ho to obtain the corrected stellar velocity dispersions
($\sigma_{*}^c$). We also calculate the supermassive black holes masses from
$\sigma_{*}^c$ in these high-redshift type II AGNs. The [O III] luminosity is
correlated with the black hole mass (although no correlation between the
extinction-corrected [O III] luminosity and the black hole mass), and no
correlation is found between the Eddington ratio and the [O III] luminosity or
the corrected [O III] luminosity. Three sets of two-component profile are used
to fit multiple emission transitions ([O III]$\lambda\lambda$4959, 5007 and [O
II]$\lambda\lambda$3727, 3729) in these 33 stellar-light subtracted spectra. We
also measure the gas velocity dispersion ($\sigma_{g}$) from these multiple
transitions, and find that the relation between $\sigma_{g}$ and $\sigma_{*}^c$
becomes much weaker at higher redshifts than in smaller redshifts. The
distribution of $<\sigma_{g}/\sigma_{*}^c>$ is $1.24\pm0.76$ for the core [O
III] line and $1.20\pm0.96$ for the [O II] line, which suggests that
$\sigma_{g}$ of the core [O III] and [O II] lines can trace $\sigma_{*}^c$
within about 0.1 dex in the logarithm of $\sigma_{*}^c$. For the secondary
driver, we find that the deviation of $\sigma_{g}$ from $\sigma_{*}^c$ is
correlated with the Eddington ratio.


title: The Onset of Gamma-Ray Burst Afterglow

abstract:
  We discuss the reference time t_0 of afterglow light curves in the context of
the standard internal-external shock model. The decay index of early afterglow
is very sensitive to the reference time one chooses. In order to understand the
nature of early afterglow, it is essential to take a correct reference time.
Our simple analytic model provides a framework to understand special
relativistic effects involved in early afterglow phase. We evaluate light
curves of reverse shock emission as well as those of forward shock emission,
based on full hydrodynamic calculations. We show that the reference time does
not shift significantly even in the thick shell case. For external shock
emission components, measuring times from the beginning of the prompt emission
is a good approximation and it does not cause an early steep decay. In the thin
shell case, the energy transfer time from fireball ejecta to ambient medium
typically extends to thousands of seconds. This might be related to the shallow
decay phases observed in early X-ray afterglow at least for some bursts.


title:
Silicon Monoxide Observations Reveal a Cluster of Hidden Compact
  Outflows in the OMC1 South Region

abstract:
  We present high angular resolution ($2\rlap.{''}8 \times 1\rlap.{''}7$) SiO
J=5$\to$4; $v=0$ line observations of the OMC1S region in the Orion Nebula made
using the Submillimeter Array (SMA). We detect for the first time a cluster of
four compact bipolar and monopolar outflows that show high, moderate and low
velocity gas and appear to be energized by millimeter and infrared sources
associated with this region. The SiO molecular outflows are compact ($<$ 3500
AU), and in most of the cases, they are located very close to their exciting
sources. We thus propose that the SiO thermal emission is tracing the youngest
and most highly excited parts of the outflows which cannot be detected by other
molecules. Moreover, since the ambient cloud is weak in the SiO line emission,
these observations can reveal flows that in other molecular transitions will be
confused with the ambient velocity cloud emission. Analysis of their
positional-velocity diagrams show that some components of these outflows may be
driven by wide-angle winds very close to the exciting object. Finally, we find
that some of these SiO outflows seem to be the base of powerful Herbig-Haro
jets and large-scale molecular flows that emanate from a few arcseconds around
this zone. In particular, we find a strongly excited SiO bipolar outflow with a
P.A. of $\sim$ 100$^{\circ}$, that is likely energized by the luminous ($\sim$
3 $\times$ 10$^3$ L$_{\odot}$) infrared protostar "B" and could be the base of
the remarkable object HH269.


title:
The magnetic Bp star 36 Lyncis, II. A spectroscopic analysis of its
  co-rotating disk

abstract:
  We report on the physical properties of the disk-like structure of B8 IIIp
star 36 Lyncis from line syntheses of phase-resolved, high resolution spectra
obtained from the IUE archives and from newly obtained ground-based H$\alpha$
spectra. This disk is highly inclined to the rotational axis and betrays its
existence every half rotation cycle as one of two opposing sectors pass in
front of the star. Although the disk absorption spectrum is at least ten times
too weak to be visible in optical iron lines during these occultations, its
properties can be readily examined in a large number of UV "iron curtain" lines
because of their higher opacities. The analysis of the variations of the UV
resonance lines brings out some interesting details about the radiative
properties of the disks: (1) they are optically thick in the C IV and Si IV
doublets, (2) the range of excitation of the UV resonance lines is larger at
the primary occultation ($\phi$ = 0.00) than at the secondary one, and (3) the
{\bf relative strengths of the absorption peaks} for the two occultations
varies substantially from line to line. We have modeled the absorptions of the
UV C IV resonance and H$\alpha$ absorptions by means of a simulated disk with
opaque and translucent components. Our simulations suggest that a gap separates
the star and the inner edge of the disk. The disk extends radially out to
$\geq$10 R$_{*}$. The disk scale height perpendicular to the plane is
$\approx$1R$_{*}$. However, the sector causing the primary occultation is about
four times thicker than the opposite sector. The C IV scattering region extends
to a larger height than the H$\alpha$ region does, probably because it results
from shock heating far from the cooler disk plane.


title: The magnetic Bp star 36 Lyncis, I. Magnetic and photospheric properties

abstract:
  This paper reports the photospheric, magnetic and circumstellar gas
characteristics of the magnetic B8p star 36 Lyncis (HD 79158). Using archival
data and new polarised and unpolarised high-resolution spectra, we redetermine
the basic physical properties, the rotational period and the geometry of the
magnetic field, and the photospheric abundances of various elements.}{Based on
magnetic and spectroscopic measurements, we infer an improved rotational period
of $3.83475\pm 0.00002$ d. We determine a current epoch of the longitudinal
magnetic field positive extremum (HJD 2452246.033), and provide constraints on
the geometry of the dipole magnetic field ($i\geq 56\degr$, $3210 {\rm G}\leq
B_{\rm d}\leq 3930$ G, $\beta$ unconstrained). We redetermine the effective
temperature and surface gravity using the optical and UV energy distributions,
optical photometry and Balmer line profiles ($T_{\rm eff}=13300\pm 300$ K,
$\log g=3.7-4.2$), and based on the Hipparcos parallax we redetermine the
luminosity, mass, radius and true rotational speed ($L=2.54\pm 0.16 L_\odot,
M=4.0\pm 0.2 M_\odot, R=3.4\pm 0.7 R_\odot, v_{\rm eq}=45-61.5$ \kms). We
measure photospheric abundances for 21 elements using optical and UV spectra,
and constrain the presence of vertical stratification of these elements. We
perform preliminary Doppler Imaging of the surface distribution of Fe, finding
that Fe is distributed in a patchy belt near the rotational equator. Most
remarkably, we confirm strong variations of the H$\alpha$ line core which we
interpret as due to occultations of the star by magnetically-confined
circumstellar gas.


title:
Cosmic Rays at the Highest Energies -- First Data from the Pierre Auger
  Observatory --

abstract:
  The southern Pierre Auger Observatory, presently under construction in
Malarg"ue, Argentina, is nearing completion. The instrument is designed to
measure extensive air-showers with energies ranging from $10^{18}$-$10^{20}$ eV
and beyond. It combines two complementary observation techniques; the detection
of particles at ground and the coincident observation of associated
fluorescence light generated in the atmosphere above the ground. This is being
realized by employing an array of 1600 water Cherenkov detectors, distributed
over an area of 3000 km$^{2}$, and operating 24 wide-angle Schmidt telescopes,
positioned at four sites at the border of the ground array. The Observatory
will reach its full size only in 2007 but data are routinely recorded already
and have started to provide relevant science results. This talk will focus on
the detector characterizations and presents first results on the arrival
direction of extremely-high energy cosmic rays, their energy spectrum, and on
the upper limit of the photon fraction.


title:
Performance and Fundamental Processes at Low Energy in a Two-Phase
  Liquid Xenon Dark Matter Detector

abstract:
  We extend the study of the performance of a prototype two-phase liquid xenon
WIMP dark matter detector to recoil energies below 20 keV. We demonstrate a new
method for obtaining the best estimate of the energies of events using a
calibrated sum of charge and light signals and introduce the corresponding
discrimination parameter, giving its mean value at 4 kV/cm for electron and
nuclear recoils up to 300 and 100 keV, respectively. We show that fluctuations
in recombination limit discrimination for most energies, and reveal an
improvement in discrimination below 20 keV due to a surprising increase in
ionization yield for low energy electron recoils. This improvement is crucial
for a high-sensitivity dark matter search.


title: Deflation at Turnaround for Oscillatory Cosmology

abstract:
  It is suggested that dark energy in a brane world can help reconcile an
infinitely cyclic cosmology with the second law of thermodynamics. A cyclic
cosmology is described, in which dark energy with constant equation of state
leads to a turnaround at finite future time, when entropy is decreased by a
huge factor equal to the inverse of its enhancement during the initial
inflation. Thermodynamic consistency of cyclicity requires the arrow of time to
reverse during contraction. Entropy reduction in the contracting phase is
infinitesimally smaller than entropy increase during expansion.


title: Status of IceCube in 2005

abstract:
  IceCube is a kilometer scale neutrino observatory now in construction at the
South Pole. The construction started in January 2005 with the deployment of 76
sensors on the first string and four surface detector stations. Nine strings
and 32 surface detectors are in operation since February 2006. The data based
on calibration measurements, muons and artificial light flashes are consistent
with performance expectations. This report focuses on design, construction
experience and first data from the sensors deployed in January 2005.


title: IceCube: The state of the art

abstract:
  In this paper we describe the performance of the 9 instrumented IceCube
strings and 16 surface IceTop stations taking data at the Geographical South
Pole after 2 deployment seasons. We will focus on the description of the array
and on the construction and data analysis status. The expected full array
performance is discussed and compared to other results for the relevant physics
studies using high energy neutrinos for astrophysical neutrino searches.


title:
Dynamical Zodiacal Cloud Models Constrained by High Resolution
  Spectroscopy of the Zodiacal Light

abstract:
  We present simulated observations of the Doppler shifts of the solar Mg I
Fraunhofer line scattered by asteroidal, cometary, and trans-Neptunian dust
particles. The studies are based on the results of integrations of orbital
evolution of particles under the gravitational influence of planets, the
Poynting-Robertson drag, radiation pressure, and solar wind drag. The derived
shifts in the centroid and profile of the line with solar elongation are
different for different sources of dust. A comparison of the velocities of
zodiacal dust particles based on these numerical integrations with the
velocities obtained from WHAM observations shows that the fraction of cometary
dust particles among zodiacal dust particles is significant and can be
dominant. A considerable fraction of trans-Neptunian dust particles among
zodiacal dust particles also fits different observations. The mean eccentricity
of zodiacal dust particles is estimated to be about 0.5.


title:
The SuperWASP wide-field exoplanetary transit survey: Candidates from
  Fields 23hr < RA < 03hr

abstract:
  Photometric transit surveys promise to complement the currently known sample
of extra-solar planets by providing additional information on the planets and
especially their radii. Here we present extra-solar planet (ESP) candidates
from one such survey called, the Wide Angle Search for Planets (WASP) obtained
with the SuperWASP wide-field imaging system. Observations were taken with
SuperWASP-North located in La Palma during the April to October 2004 observing
season. The data cover fields between 23hr and 03hr in RA at declinations above
+12. This amounts to over $\approx$400,000 stars with V magnitudes 8 to 13.5.
For the stars brighter than 12.5, we achieve better than 1 percent photometric
precision. Here we present 41 sources with low amplitude variability between
$\approx$ 1 and 10 mmag, from which we select 12 with periods between 1.2 and
4.4 days as the most promising extrasolar planet candidates. We discuss the
properties of these ESP candidates, the expected fraction of transits recovered
for our sample, and implications for the frequency and detection of
hot-Jupiters.


title:
Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. II. 2MASS J
  17072343-0558249AB

abstract:
  We present IRTF SpeX observations of the M/L binary system 2MASS
J17072343-0558249. SpeX imaging resolves the system into a 1"01+/-0.17 visual
binary in which both components have red near infrared colors. Resolved
low-resolution (R~150) 0.8-2.5 micron spectroscopy reveals strong H2O, CO and
FeH bands and alkali lines in the spectra of both components, characteristic of
late-type M and L dwarfs. A comparison to a sample of late-type field dwarf
spectra indicates spectral types M9 and L3. Despite the small proper motion of
the system (0"100+/-0"009 yr^{-1}), imaging observations over 2.5 yr provide
strong evidence that the two components share common proper motion. Physical
association is also likely due to the small spatial volume occupied by the two
components (based on spectrophotometric distances estimates of 15+/-1 pc) as
compared to the relatively low spatial density of low mass field stars. The
projected separation of the system is 15+/-3 AU, similar to other late-type M
and L binaries. Assuming a system age of 0.5-5 Gyr, we estimate the masses of
the binary components to be 0.072-0.083 and 0.064-0.077 M_sun, with an orbital
period of roughly 150-300 yr. While this is nominally too long a baseline for
astrometric mass measurements, the proximity and relatively wide angular
separation of the 2MASS J1707-0558AB pair makes it an ideal system for studying
the M dwarf/L dwarf transition at a fixed age and metallicity.


title: Soft X-ray emissions of Si IX in Procyon

abstract:
  An analysis of $n=3 \to 2$ transition lines of carbon-like silicon reveals
that some ratios of line intensities are sensitive to the electron density. The
ratio between two group of $3d\to2p$ transition lines at 55.246 \AA and 55.346
\AA is a good $n_{\rm e}$-diagnostic technique, due to its insensitivity to the
electron temperature. Using this property, a lower limit of the density of
0.6$\times10^8$cm$^{-3}$ is derived for Procyon, which is consistent with that
constrained by C V and Si X emissions. Significant discrepancies in ratios of
$3s\to2p$ lines to $3d\to2p$ lines between theoretical predictions and observed
values, are found, by the spectral analysis of Procyon observed with the {\it
Chandra} High Resolution Transmission Grating spectra. The difference exceeding
a factor of 3, cannot be explained by the uncertainty of atomic data. The
opacity effect is also not a choice as reported by Ness and co-workers. For the
$3s\to2p$ line at 61.611 \AA, present work indicates that the large discrepancy
may be due to the contamination from a S VIII line at 61.645 \AA . For the
lines at 61.702 and 61.846 \AA, we suggest that the discrepancies may be
attributed to contaminations of unknown lines.


title:
Quasi Periodic Oscillations (QPOs) and frequencies in an accretion disk
  and comparison with the numerical results from non-rotating black hole
  computed by the GRH code

abstract:
  The shocked wave created on the accretion disk after different physical
phenomena (accretion flows with pressure gradients, star-disk interaction etc.)
may be responsible observed Quasi Periodic Oscillations (QPOs) in $X-$ray
binaries. We present the set of characteristics frequencies associated with
accretion disk around the rotating and non-rotating black holes for one
particle case. These persistent frequencies are results of the rotating pattern
in an accretion disk. We compare the frequency's from two different numerical
results for fluid flow around the non-rotating black hole with one particle
case. The numerical results are taken from our papers Refs.\refcite{Donmez2}
and \refcite{Donmez3} using fully general relativistic hydrodynamical code with
non-selfgravitating disk. While the first numerical result has a relativistic
tori around the black hole, the second one includes one-armed spiral shock wave
produced from star-disk interaction. Some physical modes presented in the QPOs
can be excited in numerical simulation of relativistic tori and spiral waves on
the accretion disk. The results of these different dynamical structures on the
accretion disk responsible for QPOs are discussed in detail.


title: The central elliptical galaxy in fossil groups and formation of BCGs

abstract:
  We study the dominant central giant elliptical galaxies in ``Fossil groups''
using deep optical (R-band) and near infrared (Ks-band) photometry. These
galaxies are as luminous as the brightest cluster galaxies (BCGs), raising
immediate interest in their link to the formation of BCGs and galaxy clusters.
However, despite apparent similarities, the dominant fossil galaxies show
non-boxy isophotes, in contrast to the most luminous BCGs. This study suggests
that the structure of the brightest group galaxies produced in fossil groups
are systematically different to the majority of BCGs. If the fossils do indeed
form from the merger of major galaxies including late-types within a group,
then their disky nature is consistent with the results of recent numerical
simulations of semi-analytical models which suggest that gas rich mergers
result in disky isophote ellipticals.
  We show that fossils form a homogeneous population in which the velocity
dispersion of the fossil group is tightly correlated with the luminosity of the
dominant elliptical galaxy. This supports the scenario in which the giant
elliptical galaxies in fossils can grow to the size and luminosity of BCGs in a
group environment. However, the boxy structure of luminous BCGs indicate that
they are either not formed as fossils, or have undergone later gas-free mergers
within the cluster environment.


title: Dwarf galaxies in Hickson Compact Groups

abstract:
  We observed 5 Hickson Compact Groups with the ESO/MPI 2.2m telescope and WFI
to investigate the dwarf galaxy content and distribution in these galaxy
groups. Our deep imaging and careful selection of the candidate galaxies
revealed a rich population of mainly passively evolving dwarf galaxies, which
is spatially much more extended than the originally defined Hickson Compact
groups. The composite luminosity function of the 5 groups shows a bimodal
structure with a very steep rise in the low luminosity regime. The faint end
slope is close to the predictions of CDM theory for the slope of the Dark
Matter halo mass function.


title:
The Spitzer c2d Survey of Nearby Dense Cores: II: Discovery of a Low
  Luminosity Object in the "Evolved Starless Core" L1521F

abstract:
  We present Spitzer Space Telescope observations of the "evolved starless
core" L1521F which reveal the presence of a very low luminosity object (L <
0.07 Lsun). The object, L1521F-IRS, is directly detected at mid-infrared
wavelengths (>5 micron) but only in scattered light at shorter infrared
wavelengths, showing a bipolar nebula oriented east-west which is probably
tracing an outflow cavity. The nebula strongly suggests that L1521F-IRS is
embedded in the L1521F core. Thus L1521F-IRS is similar to the recently
discovered L1014-IRS and the previously known IRAM 04191 in its substellar
luminosity and dense core environment. However these objects differ
significantly in their core density, core chemistry, and outflow properties,
and some may be destined to be brown dwarfs rather than stars.


title: GRI: the gamma-ray imager mission

abstract:
  Observations of the gamma-ray sky reveal the most powerful sources and the
most violent events in the Universe. While at lower wavebands the observed
emission is generally dominated by thermal processes, the gamma-ray sky
provides us with a view on the non-thermal Universe. Here particles are
accelerated to extreme relativistic energies by mechanisms which are still
poorly understood, and nuclear reactions are synthesizing the basic
constituents of our world. Cosmic accelerators and cosmic explosions are the
major science themes that are addressed in the gamma-ray regime.
  With the INTEGRAL observatory, ESA has provided a unique tool to the
astronomical community revealing hundreds of sources, new classes of objects,
extraordinary views of antimatter annihilation in our Galaxy, and fingerprints
of recent nucleosynthesis processes. While INTEGRAL provides the global
overview over the soft gamma-ray sky, there is a growing need to perform
deeper, more focused investigations of gamma-ray sources. In soft X-rays a
comparable step was taken going from the Einstein and the EXOSAT satellites to
the Chandra and XMM/Newton observatories. Technological advances in the past
years in the domain of gamma-ray focusing using Laue diffraction and
multilayer-coated mirror techniques have paved the way towards a gamma-ray
mission, providing major improvements compared to past missions regarding
sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow
to study particle acceleration processes and explosion physics in unprecedented
detail, providing essential clues on the innermost nature of the most violent
and most energetic processes in the Universe.


title:
The Fundamental Plane in RX J0142.0+2131: a galaxy cluster merger at
  z=0.28

abstract:
  We present the Fundamental Plane (FP) in the z = 0.28 cluster of galaxies RX
J0142.0+2131. There is no evidence for a difference in the slope of the FP when
compared with the Coma cluster, although the internal scatter is larger. On
average, stellar populations in RX J0142.0+2131 have rest-frame V-band
mass-to-light ratios (M/L_V) 0.29+-0.03 dex lower than in Coma. This is
significantly lower than expected for a passively-evolving cluster formed at
z_f=2. Lenticular galaxies have lower average M/L_V and a distribution of M/L_V
with larger scatter than ellipticals. Lower mass-to-light ratios are not due to
recent star formation: our previous spectroscopic observations of RX
J0142.0+2131 E/S0 galaxies showed no evidence for significant star-formation
within the past ~4 Gyr. However, cluster members have enhanced alpha-element
abundance ratios, which may act to decrease M/L_V. The increased scatter in the
RX J0142.0+2131 FP reflects a large scatter in M/L_V implying that galaxies
have undergone bursts of star formation over a range of epochs. The seven
easternmost cluster galaxies, including the second brightest member, have M/L_V
consistent with passive evolution and z_f = 2. We speculate that RX
J0142.0+2131 is a cluster-cluster merger where the galaxies to the east are yet
to fall into the main cluster body or have not experienced star formation as a
result of the merger.


title:
Exploring Halo Substructure with Giant Stars X. Extended Dark Matter or
  Tidal Disruption?: The Case for the Leo I Dwarf Spheroidal Galaxy

abstract:
  We present a wide-field (4.5 deg^2) photometric and spectroscopic survey of
the Leo I dwarf spheroidal (dSph) galaxy to explore its extended morphology and
dynamics. As in previous papers in this series, we take advantage of photometry
in the M, T_2, and DDO51 filter system to select LeoI red giant branch star
candidates, and, so far, this selection technique has proven 100% reliable in
selecting actual Leo I members among more than 100 M < 21.5 Leo I giant
candidates having previous or new Keck DEIMOS spectroscopy to a radius >1.3
times the limiting radius of the fitted, central King profile. The
two-dimensional distribution of all similarly-selected Leo I giant candidates
is well fitted by a central single-component King profile of limiting radius
13.3 arcmin, but many giant stars are found outside this newly derived King
limiting radius. The density profile thus shows a break at a major axis radial
distance of ~10 arcmin produced by an excess of stars at and beyond the King
limiting radius (spectroscopically confirmed to be made of true Leo I members),
and primarily along the major axis of the main body of the rather elongated
satellite. This spatial configuration, a rather flat velocity dispersion
profile and an asymmetric radial velocity (RV) distribution among the Leo I
members at large radii together support a picture where Leo I has been tidally
disrupted on at least one, but at most two, perigalactic passages of a massive
Local Group member. (abridged)