title: Enhancing the tensor-to-scalar ratio in simple inflation

abstract:
  We show that in theories with a nontrivial kinetic term the contribution of
the gravitational waves to the CMB fluctuations can be substantially larger
than that is naively expected in simple inflationary models. This increase of
the tensor-to-scalar perturbation ratio leads to a larger B-component of the
CMB polarization, thus making the prospects for future detection much more
promising. The other important consequence of the considered model is a higher
energy scale of inflation and hence higher reheating temperature compared to a
simple inflation.


title:
Testing the Self-Consistency of MOND With Three-Dimensional Galaxy
  Kinematics

abstract:
  We propose a technique to test the idea that non-standard dynamics, rather
than dark matter halos, might be responsible for the observed rotation curves
of spiral galaxies. In the absence of non-luminous matter, a galactic disk's
rotational velocity and its vertical velocity dispersion can be used jointly to
test the self-consistency of the galaxy's dynamics. A specific illustrative
example, using recent measurements of the disk kinematics of M33, shows this to
be a promising approach to assess the viability of Modified Newtonian Dynamics
(MOND).


title: Meridional Transport in the Stratosphere of Jupiter

abstract:
  The Cassini measurements of C$_2$H$_2$ and C$_2$H$_6$ at $\sim$5 mbar provide
a constraint on meridional transport in the stratosphere of Jupiter. We
performed a two-dimensional photochemical calculation coupled with mass
transport due to vertical and meridional mixing. The modeled profile of
C$_2$H$_2$ at latitudes less than 70$^\circ$ follows the latitude dependence of
the solar insolation, while that of C$_2$H$_6$ shows little latitude
dependence, consistent with the measurements. In general, our model study
suggests that the meridional transport timescale above 5-10 mbar altitude level
is $\gtrsim$1000 years and the time could be as short as 10 years below 10 mbar
level, in order to fit the Cassini measurements. The derived meridional
transport timescale above the 5 mbar level is a hundred times longer than that
obtained from the spreading of gas-phase molecules deposited after the impact
of Shoemaker-Levy 9 comet. There is no explanation at this time for this
discrepancy.


title: Infrared Luminosity Function of the Coma Cluster

abstract:
  Using mid-IR and optical data, we deduce the total infrared (IR) luminosities
of galaxies in the Coma cluster and present their infrared luminosity function
(LF). The shape of the overall Coma IR LF does not show significant differences
from the IR LFs of the general field, which indicates the general independence
of global galaxy star formation on environment up to densities $\sim$ 40 times
greater than in the field (we cannot test such independence above $L_{ir}
\approx 10^{44} {\rm ergs s}^{-1}$). However, a shallower faint end slope and a
smaller $L_{ir}^{*}$ are found in the core region (where the densities are
still higher) compared to the outskirt region of the cluster, and most of the
brightest IR galaxies are found outside of the core region. The IR LF in the
NGC 4839 group region does not show any unique characteristics. By integrating
the IR LF, we find a total star formation rate in the cluster of about 97.0
$M_{\sun}{\rm yr}^{-1}$. We also studied the contributions of early- and
late-type galaxies to the IR LF. The late-type galaxies dominate the bright end
of the LF, and the early-type galaxies, although only making up a small portion
($\approx$ 15%) of the total IR emission of the cluster, contribute greatly to
the number counts of the LF at $L_{ir} < 10^{43} {\rm ergs s}^{-1}$.


title: A survey of weak MgII absorbers at redshift <z>=1.78

abstract:
  The exact nature of weak MgII absorbers (those with W_r(2796) < 0.3 A) is a
matter of debate, but most are likely related to areas of local star formation
or supernovae activity outside of giant galaxies. Using 18 QSO spectra obtained
with the Ultra-Violet Echelle Spectrograph (UVES) on the Very Large Telescope
(VLT), we have conducted a survey for weak MgII absorbers at 1.4 < z < 2.4. We
searched a redshift path length of 8.51, eliminating regions badly contaminated
by atmospheric absorption so that the survey is close to 100% complete to
W_r(2796) = 0.02 A. We found a total of 9 weak absorbers, yielding a number
density of absorbers of dN/dz = 1.06 +/- 0.12 for 0.02 <= W_r(2796) < 0.3 A.
Narayanan et al. (2005) found dN/dz = 1.00 +/- 0.20 at 0 < z < 0.3 and
Churchill et al. (1999) found dN/dz = 1.74 +/- 0.10 at 0.4 < z < 1.4.
Therefore, the population of weak MgII absorbers appears to peak at z~1. We
explore the expected evolution of the absorber population subject to a changing
extragalactic background radiation (EBR) from z = 0.9 to z = 1.78 (the median
redshift of our survey), and find that the result is higher than the observed
value. We point out that the peak epoch for weak MgII absorption at z~1 may
coincide with the peak epoch of global star formation in the dwarf galaxy
environment.


title: Breaking the Degeneracies Between Cosmology and Galaxy Bias

abstract:
  Adopting the framework of the Halo Occupation Distribution (HOD), we
investigate the ability of galaxy clustering measurements to simultaneously
constrain cosmological parameters and galaxy bias. Starting with a fiducial
cosmological model and galaxy HOD, we calculate spatial clustering observables
on a range of length and mass scales, dynamical clustering observables that
depend on galaxy peculiar velocities, and the galaxy-matter cross-correlation
measurable by weak lensing. We then change one or more cosmological parameters
and use chi^2-minimization to find the galaxy HOD that best reproduces the
original clustering. Our parameterization of the HOD incorporates a flexible
relation between galaxy occupation numbers and halo mass and allows spatial and
velocity bias of galaxies within dark matter halos. Despite this flexibility,
we find that changes to the HOD cannot mask substantial changes to the matter
density Omega_m, the matter clustering amplitude sigma_8, or the shape
parameter Gamma of the linear matter power spectrum -- cosmology and bias are
not degenerate. With the conservative assumption of 10% fractional errors, the
set of observables considered here can provide ~10% (1 sigma) constraints on
sigma_8, Omega_m, and Gamma, using galaxy clustering data ALONE. The
combination sigma_8*Omega_m^0.75 is constrained to ~5%. In combination with
traditional methods that focus on large scale structure in the "perturbative"
regime, HOD modeling can greatly amplify the cosmological power of galaxy
redshift surveys by taking advantage of high-precision clustering measurements
at small and intermediate scales (from sub-Mpc to ~20Mpc/h). At the same time,
the inferred constraints on the galaxy HOD provide valuable tests of galaxy
formation theory.


title:
The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models
  for Active and Inactive Solar-Type Stars

abstract:
  (Abridged) We present spectroscopic and photometric observations of the
eclipsing system V1061 Cyg (P = 2.35 days). We show that it is a hierarchical
triple in which the third star is visible in the spectra. We combine the radial
velocities for the three stars, times of eclipse, and intermediate astrometric
data from the HIPPARCOS mission (abscissa residuals) to establish the elements
of the outer orbit (P = 15.8 yr) and accurate values for the masses and radii
(1-2% errors) and the effective temperatures of the binary components. Both
stars are rotating rapidly and have their rotation synchronized with the
orbital motion. There are signs of activity including strong X-ray emission and
possibly spots. Current stellar evolution models agree well with the properties
of the primary, but show a very large discrepancy in the radius of the
secondary: the predicted values are about 10% smaller than observed (a 5-sigma
effect). Also, the temperature is cooler than predicted by some 200 K. These
discrepancies are quite remarkable given that the star is only 7% less massive
than the Sun, the calibration point of all stellar models. We identify the
chromospheric activity as the likely cause of the effect. Inactive stars agree
very well with the models, while active ones such as V1061 Cyg Ab appear
systematically too large and too cool. Theory provides an understanding of this
in terms of the strong magnetic fields commonly associated with stellar
activity, which tend to inhibit convective heat transport.


title:
The Effect of Gravitational Recoil on Black Holes Forming in a
  Hierarchical Universe

abstract:
  Galactic bulges are known to harbour central black holes whose mass is
tightly correlated with the stellar mass and velocity dispersion of the bulge.
In a hierarchical universe, mergers of subgalactic units are accompanied by the
amalgamation of bulges and the likely coalescence of galactocentric black
holes. In these mergers, the beaming of gravitational radiation during the
plunge phase of the black hole collision can impart a linear momentum kick or
``gravitational recoil'' to the remnant. If large enough, this kick will eject
the remnant from the galaxy and populate intergalactic space with wandering
black holes. Using a semi-analytic model of galaxy formation, we investigate
the effect of black hole ejections on the scatter in the relation between black
hole and bulge mass. We find that although not the dominant source of the
measured scatter, they do make a significant contribution and may be used to
set a constraint, v_kick<500 km/s, on the typical kick velocity, in agreement
with values found from general relativistic calculations. Even for the more
modest kick velocities implied by these calculations, we find that a
substantial number of central black holes are ejected from the progenitors of
present day galaxies, giving rise to a population of wandering intrahalo and
intergalactic black holes whose distribution we investigate in high-resolution
N-body simulations of Milk-Way mass halos. We find that intergalactic black
holes make up only ~2-3% of the total galactic black hole mass but, within a
halo, wandering black holes can contribute up to about half of the total black
hole mass orbiting the central galaxy. Intrahalo black holes offer a natural
explanation for the compact X-ray sources often seen near the centres of
galaxies and for the hyperluminous non-central X-ray source in M82.


title: Adaptive Binning of X-ray data with Weighted Voronoi Tesselations

abstract:
  We present a technique to adaptively bin sparse X-ray data using weighted
Voronoi tesselations (WVTs). WVT binning is a generalisation of Cappellari &
Copin's (2001) Voronoi binning algorithm, developed for integral field
spectroscopy. WVT binning is applicable to many types of data and creates
unbiased binning structures with compact bins that do not lead the eye. We
apply the algorithm to simulated data, as well as several X-ray data sets, to
create adaptively binned intensity images, hardness ratio maps and temperature
maps with constant signal-to-noise ratio per bin. We also illustrate the
separation of diffuse gas emission from contributions of unresolved point
sources in elliptical galaxies. We compare the performance of WVT binning with
other adaptive binning and adaptive smoothing techniques. We find that the CIAO
tool csmooth creates serious artefacts and advise against its use to interpret
diffuse X-ray emission.


title: Three-Body Affairs in the Outer Solar System

abstract:
  Recent observations (Burnes2002,Veillet2002,Margot2002a) have revealed an
unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that
populate the Kuiper Belt. The TNO binaries are strikingly different from
asteroid binaries in four respects (Veillet2002): their frequency is an order
of magnitude larger, the mass ratio of their components is closer to unity, and
their orbits are wider and highly eccentric. Two explanations have been
proposed for their formation, one assuming large numbers of massive bodies
(Weidenschilling2002), and one assuming large numbers of light bodies
(Goldreich2002). We argue that both assumptions are unwarranted, and we show
how TNO binaries can be produced from a modest number of intermediate-mass
bodies of the type predicted by the gravitational instability theory for the
formation of planetesimals (Goldreich and Ward1973). We start with a TNO binary
population similar to the asteroid binary population, but subsequently modified
by three-body exchange reactions, a process that is far more efficient in the
Kuiper belt, because of the much smaller tidal perturbations by the Sun. Our
mechanism can naturally account for all four characteristics that distinguish
TNO binaries from main-belt asteroid binaries.


title: Supernovae constraints on dark energy and modified gravity models

abstract:
  We use the Type Ia Supernova gold sample to constrain the parameters of dark
energy models namely the Cardassian, Dvali-Turner (DT) and generalized
Chaplygin gas (GCG) models. In our best fit analysis for these dark energy
proposals we consider flat and the non-flat priors. For all models, we find
that relaxing the flatness condition implies that data favors a positive
curvature; moreover, the GCG model is nearly flat, as required by Cosmic
Microwave Background (CMB) observations.


title: Challenges in Non-Linear Gravitational Clustering

abstract:
  This article addresses some issues related to statistical description of
gravitating systems in an expanding backgrounds. In particular, I describe (a)
how the non linear mode-mode coupling transfers power from one scale to another
in the Fourier space if the initial power spectrum is sharply peaked at a given
scale and (b) what are the asymptotic characteristics of gravitational
clustering that are independent of the initial conditions. The analysis uses a
new approach based on an integro-differential equation for the evolution of the
gravitational potential in the Fourier space. I show how this equation allows
one to understand several aspects of nonlinear gravitational clustering and
provides insight in to the transfer of power from one scale to another through
nonlinear mode coupling. Numerical simulations as well as analytic work shows
that power transfer leads to a universal power spectrum at late times, somewhat
reminiscent of the existence of Kolmogorov spectrum in fluid turbulence.


title: Far-flung Filaments of Ejecta in the Young Supernova Remnant G292.0+1.8

abstract:
  New optical images of the young SNR G292.0+1.8, obtained from the 0.9-m
telescope at CTIO, show a more extensive network of filaments than had been
known previously. Filaments emitting in [O III] are distributed throughout much
of the 8 arcmin diameter shell seen in X-ray and radio images, including a few
at the very outermost shell limits. We have also detected four small complexes
of filaments that show [S II] emission along with [OIII]. In a single long-slit
spectrum we find variations of almost an order of magnitude in the relative
strengths of oxygen and sulfur lines, which must result from abundance
variations. None of the filaments, with or without [S II], shows any evidence
for hydrogen, so all appear to be fragments of pure SN ejecta. The [S II]
filaments provide the first evidence for undiluted products of oxygen burning
in the ejecta from the supernova that gave rise to G292.0+1.8. Some oxygen
burning must have occurred, but the paucity of [S II]-emitting filaments
suggests that either the oxygen burning was not extensive or that most of its
products have yet to be excited. Most of the outer filaments exhibit radial,
pencil-like morphologies that suggest an origin as Rayleigh-Taylor fingers of
ejecta, perhaps formed during the explosion. Simulations of core-collapse
supernovae predict such fingers, but these have never before been so clearly
observed in a young SNR. The total flux from the SNR in [OIII] 5007 is 5.4 *
10**-12 ergs/cm**2/s. Using a distance of 6 kpc and an extinction correction
corresponding to E(B-V) = 0.6 (lower than previous values but more consistent
both with our data and radio and X-ray estimates of NH), this leads to a
luminosity of 1.6 * 10**35 ergs/s in the 5007 Ang. line.


title:
Cluster magnetic fields from large-scale-structure and galaxy-cluster
  shocks

abstract:
  The origin of the micro-Gauss magnetic fields in galaxy clusters is one of
the outstanding problem of modern cosmology. We have performed
three-dimensional particle-in-cell simulations of the nonrelativistic Weibel
instability in an electron-proton plasma, in conditions typical of cosmological
shocks. These simulations indicate that cluster fields could have been produced
by shocks propagating through the intergalactic medium during the formation of
large-scale structure or by shocks within the cluster. The strengths of the
shock-generated fields range from tens of nano-Gauss in the intercluster medium
to a few micro-Gauss inside galaxy clusters.


title:
A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV: Discovery
  of Seven Additional Quasars

abstract:
  We present the discovery of seven quasars at z>5.7, selected from ~2000 deg^2
of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new
quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a
complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger
photometric errors and are not part of the complete sample. One of the new
quasars, SDSS J1335+3533 (z=5.93), exhibits no emission lines; the 3-sigma
limit on the rest-frame equivalent width of Ly alpha+NV line is 5 A. It is the
highest redshift lineless quasar known, and could be a gravitational lensed
galaxy, a BL Lac object or a new type of quasar. Two new z>6 quasars, SDSS
1250+3130 (z=6.13) and SDSS J1137+3549 (z=6.01), show deep Gunn-Peterson
absorption gaps in Ly alpha. These gaps are narrower the complete Gunn-Peterson
absorption troughs observed among quasars at z>6.2 and do not have complete Ly
beta absorption.


title:
GRB 050408: An Atypical Gamma-Ray Burst as a Probe of an Atypical
  Galactic Environment

abstract:
  The bright GRB 050408 was localized by HETE-II near local midnight, enabling
an impressive ground-based followup effort as well as space-based followup from
Swift. The Swift data from the X-Ray Telescope (XRT) and our own optical
photometry and spectrum of the afterglow provide the cornerstone for our
analysis. Under the traditional assumption that the visible waveband was above
the peak synchrotron frequency and below the cooling frequency, the optical
photometry from 0.03 to 5.03 days show an afterglow decay corresponding to an
electron energy index of p_lc = 2.05 +/- 0.04, without a jet break as suggested
by others. A break is seen in the X-ray data at early times (at ~12600 sec
after the GRB). The spectral slope of the optical spectrum is consistent with
p_lc assuming a host-galaxy extinction of A_V = 1.18 mag. The optical-NIR
broadband spectrum is also consistent with p = 2.05, but prefers A_V = 0.57
mag. The X-ray afterglow shows a break at 1.26 x 10^4 sec, which may be the
result of a refreshed shock. This burst stands out in that the optical and
X-ray data suggest a large H I column density of N_HI ~ 10^22 cm^-2; it is very
likely a damped Lyman alpha system and so the faintness of the host galaxy (M_V
> -18 mag) is noteworthy. Moreover, we detect extraordinarily strong Ti II
absorption lines with a column density through the GRB host that exceeds the
largest values observed for the Milky Way by an order of magnitude.
Furthermore, the Ti II equivalent width is in the top 1% of Mg II
absorption-selected QSOs. This suggests that the large-scale environment of GRB
050408 has significantly lower Ti depletion than the Milky Way and a large
velocity width (delta v > 200 km/s).


title:
Constraining the Evolution of the Ionizing Background and the Epoch of
  Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars

abstract:
  We study the evolution of the ionization state of the IGM at the end of the
reionization epoch using spectra of a sample of nineteen quasars at 5.74<z<6.42
discovered in the SDSS. Three methods are used to trace IGM properties: (a) the
evolution of the Gunn-Peterson optical depth in the Ly alpha,beta, and gamma;
(b) the distribution of dark absorption gaps, and (c) the size of HII regions
around quasars. We find that the evolution of the IGM accelerated at z>5.7: the
optical depth evolution changes from tau ~ (1+z)^{4.3} to (1+z)^{>11}, and the
average length of dark gaps with tau>3.5 increases from <10 to >80 comoving
Mpc. The dispersion of IGM properties along different lines of sight also
increases rapidly, implying fluctuations by a factor of >4 in the UV background
at z>6, when the mean free path of UV photons is comparable to the correlation
length of galaxies. The mean length of dark gaps shows the most dramatic
increase at z~6, as well as the largest varianace. We suggest using dark gap
statistics as a powerful probe of the ionization state of the IGM at yet higher
redshift. The sizes of HII regions around quasars decrease rapidly towards
higher redshift, suggesting that the neutral fraction of the IGM has increased
by a factor of >10 from z=5.7 to 6.4. The mass-averaged neutral fraction is
1-4% at z~6.2 based on the GP optical depth and HII region sizes. The
observations suggest that z~6 is the the end of the overlapping stage of
reionization, and are inconsistent with a neutral IGM at z~6, as indicated by
the finite length of dark absorption gaps.


title: Cannonballs in the context of Gamma Ray Bursts: Formation sites ?

abstract:
  We investigate possible formation sites of the cannonballs (in the gamma ray
bursts context) by calculating their physical parameters, such as density,
magnetic field and temperature close to the origin. Our results favor scenarios
where the cannonballs form as instabilities (knots) within magnetized jets from
hyperaccreting disks. These instabilities would most likely set in beyond the
light cylinder where flow velocity with Lorentz factors as high as 2000 can be
achieved. Our findings challenge the cannonball model of gamma ray bursts if
these indeed form inside core-collapse supernovae (SNe) as suggested in the
literature; unless hyperaccreting disks and the corresponding jets are common
occurrences in core-collapse SNe.


title:
Testing Rotational Mixing Predictions with New Boron Abundances in Main
  Sequence B-type Stars

abstract:
  (Abridged) New boron abundances for seven main-sequence B-type stars are
determined from HST STIS spectroscopy around the BIII 2066A line. Boron
abundances provide a unique and critical test of stellar evolution models that
include rotational mixing since boron is destroyed in the surface layers of
stars through shallow mixing long before other elements are mixed from the
stellar interior through deep mixing. Boron abundances range from 12+log(B/H) =
1.0 to 2.2. The boron abundances are compared to the published values of their
stellar nitrogen abundances (all have 12+log(N/H) < 7.8, i.e., they do not show
significant CNO-mixing) and to their host cluster ages (4 to 16 Myr) to
investigate the predictions from models of massive star evolution with
rotational mixing effects (Heger & Langer 2000). Only three stars (out of 34)
deviate from the model predictions, including HD36591, HD205021, and HD30836.
These three stars suggest that rotational mixing could be more efficient than
currently modelled at the highest rotation rates.


title: Large-scale galaxy correlations as a test for dark energy

abstract:
  We have shown earlier that, contrary to popular belief, Einstein--de Sitter
(E--deS) models can still fit the {\sl WMAP} data on the cosmic microwave
background provided one adopts a low Hubble constant and relaxes the usual
assumption that the primordial density perturbation is scale-free. The recent
{\sl SDSS} measurement of the large-scale correlation function of luminous red
galaxies at $z \sim 0.35$ has however provided a new constraint by detecting a
`baryon acoustic peak'. Our best-fit E--deS models do possess a baryonic
feature at a similar physical scale as the best-fit $\Lambda$CDM concordance
model, but do not fit the new observations as well as the latter. In particular
the shape of the correlation function in the range $\sim 10-100 h^{-1}$ Mpc
cannot be reproduced properly without violating the CMB angular power spectrum
in the multipole range $l \sim 100-1000$. Thus, the combination of the CMB
fluctuations and the shape of the correlation function up to $\sim 100
h^{-1}$Mpc, if confirmed, does seem to require dark energy for a homogeneous
cosmological model based on (adiabatic) inflationary perturbations.


title: New evidence for strong nonthermal effects in Tycho's supernova remnant

abstract:
  For the case of Tycho's supernova remnant (SNR) we present the relation
between the blast wave and contact discontinuity radii calculated within the
nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. It is
demonstrated that these radii are confirmed by recently published Chandra
measurements which show that the observed contact discontinuity radius is so
close to the shock radius that it can only be explained by efficient CR
acceleration which in turn makes the medium more compressible. Together with
the recently determined new value $E_{sn}=1.2\times 10^{51}$ erg of the SN
explosion energy this also confirms our previous conclusion that a TeV
gamma-ray flux of $(2-5)\times 10^{-13}$ erg/(cm$^2$s) is to be expected from
Tycho's SNR. Chandra measurements and the HEGRA upper limit of the TeV
gamma-ray flux together limit the source distance $d$ to $3.3\leq d\leq 4$ kpc.


title: GMRT Observations of Microquasar V4641 Sgr

abstract:
  We report the GMRT observations of V4641 Sgr during the May 2002 outburst at
radio frequencies of 610 and 244 MHz. This is the lowest frequency radio
detection of this source. The present low frequency radio observations clearly
showed spectral evolution from the optically thick to thin state. This behavior
is broadly consistent with the expanding bubble model. However, the flux
densities observed at lower frequencies are much higher than predicted by this
model. In the conical jet model, this discrepancy could be reconciled.


title:
Nonideal strongly magnetized plasmas of neutron stars and their
  electromagnetic radiation

abstract:
  We study the equation of state, polarization and radiation properties for
nonideal, strongly magnetized plasmas which compose outer envelopes of magnetic
neutron stars. Detailed calculations are performed for partially ionized
hydrogen atmospheres and for condensed hydrogen or iron surfaces of these
stars. This is a companion paper to astro-ph/0511803


title: Exact Wave Propagation in a Spacetime with a Cosmic String

abstract:
  We present exact solutions of the massless Klein-Gordon equation in a
spacetime in which an infinite straight cosmic string resides. The first
solution represents a plane wave entering perpendicular to the string
direction. We also present and analyze a solution with a static point-like
source. In the short wavelength limit these solutions approach the results
obtained by using the geometrical optics approximation: magnification occurs if
the observer lies in front of the string within a strip of angular width $8\pi
G\mu$, where $\mu$ is the string tension. We find that when the distance from
the observer to the string is less than $ 10^{-3} {(G \mu)}^{-2}\lambda \sim
150 {\rm Mpc} (\lambda/{\rm AU}) (G\mu/10^{-8})^{-2}$, where $\lambda$ is the
wave length, the magnification is significantly reduced compared with the
estimate based on the geometrical optics due to the diffraction effect. For
gravitational waves from neutron star(NS)-NS mergers the several lensing events
per year may be detected by DECIGO/BBO.


title: Diffusion of Cosmic Rays in Expanding Universe. (I)

abstract:
  We present an analytic solution to diffusion equation for high energy cosmic
rays in the expanding universe. The particles are assumed to be
ultra-relativistic and they can have energy losses arbitrarily dependent on
energy and time. The obtained solution generalizes the Syrovatsky solution,
valid for the case when energy losses and diffusion coefficient are
time-independent.


title: Birth and fate of hot-Neptune planets

abstract:
  This paper presents a consistent description of the formation and the
subsequent evolution of gaseous planets, with special attention to
short-period, low-mass hot-Neptune planets characteristic of $\mu$ Ara-like
systems. We show that core accretion including migration and disk evolution and
subsequent evolution taking into account irradiation and evaporation provide a
viable formation mechanism for this type of strongly irradiated light planets.
At an orbital distance $a \simeq$ 0.1 AU, this revised core accretion model
leads to the formation of planets with total masses ranging from $\sim$ 14
$\mearth$ (0.044 $\mjup$) to $\sim$ 400 $\mearth$ (1.25 $\mjup$). The newly
born planets have a dense core of $\sim$ 6 $\mearth$, independent of the total
mass, and heavy element enrichments in the envelope, $M_{\rm Z,env}/M_{\rm env}
$, varying from 10% to 80% from the largest to the smallest planets. We examine
the dependence of the evolution of the born planet on the evaporation rate due
to the incident XUV stellar flux. In order to reach a $\mu$ Ara-like mass
($\sim$ 14 $\mearth$) after $\sim $ 1 Gyr, the initial planet mass must range
from 166 $\mearth$ ($\sim$ 0.52 $\mjup$) to about 20 $\mearth$, for evaporation
rates varying by 2 orders of magnitude, corresponding to 90% to 20% mass loss
during evolution. The presence of a core and heavy elements in the envelope
affects appreciably the structure and the evolution of the planet and yields
$\sim 8%-9%$ difference in radius compared to coreless objects of solar
composition for Saturn-mass planets. These combinations of evaporation rates
and internal compositions translate into different detection probabilities, and
thus different statistical distributions for hot-Neptunes and hot-Jupiters.


title: Analysis of ground-based differential imager performance

abstract:
  In the context of extrasolar planet direct detection, we evaluated the
performance of differential imaging with ground-based telescopes. This study
was carried out in the framework of the VLT-Planet Finder project and is
further extended to the case of Extremely Large Telescopes. Our analysis is
providing critical specifications for future instruments mostly in terms of
phase aberrations but also regarding alignments of the instrument optics or
offset pointing on the coronagraph. It is found that Planet Finder projects on
8m class telescopes can be successful at detecting Extrasolar Giant Planets
providing phase aberrations, alignments and pointing are accurately controlled.
The situation is more pessimistic for the detection of terrestrial planets with
Extremely Large Telescopes for which phase aberrations must be lowered at a
very challenging level.


title: On the Detection of Artefacts in Spectro-astrometry

abstract:
  We demonstrate that artificial bipolar structure can be detected using
spectro-astrometry when the point spread function (PSF) of a point source
suffers distortion in a relatively wide slit. Spectro-astrometry is a technique
which allows us to probe the spatial structure of astronomical sources on
milliarcsecond scales making it possible to detect close binaries and to study
the geometry and kinematics of outflowing gas on scales much smaller than the
seeing or the diffraction limit of the telescope. It is demonstrated that
distortion of the PSF, caused by tracking errors of the telescope or unstable
active optics during an exposure can induce artificial signals which may be
misinterpreted as a real-astrometric signal. Using simulations we show that
these may be minimised by using a narrow slit relative to the seeing. Spectra
should be obtained at anti-parallel slit position angles (eg. 0 and 180
degrees) for comparison in order to allow artificial signatures to be
identified.


title:
The low-mass pre-main sequence population of the stellar association LH
  52 in the Large Magellanic Cloud discovered with Hubble Space Telescope WFPC2
  Observations

abstract:
  We report on the serendipitous discovery of ~ 500 low-mass candidate PMS
stars in the vicinity of the stellar association LH 52 in the Large Magellanic
Cloud. We present evidence that the red faint sequence of these stars seen in
the CMD of LH 52 from HST/WFPC2 observations belongs only to the association
and follows almost perfectly isochrone models for PMS stars of masses down to ~
0.3 M_solar. We find that this feature has a Galactic counterpart and that the
mass spectrum of the candidate PMS stars in LH 52 seems to correspond to a
Salpeter IMF with a slope Gamma ~ -1.26 in the mass range 0.8 - 1.4 M_solar.


title:
Orbital phase spectroscopy of X-ray pulsars to study the stellar wind of
  the companion

abstract:
  High Mass X-ray Binary Pulsars (HMXBP), in which the companion star is a
source of supersonic stellar wind, provide a laboratory to probe the velocity
and density profile of such winds. Here, we have measured the variation of the
absorption column density along with other spectral parameters over the binary
orbit for two HMXBP in elliptical orbits, as observed with the Rossi X-ray
Timing Explorer (RXTE) and the BeppoSAX satellites. A spherically symmetric
wind profile was used as a model to compare the observed column density
variations. In 4U 1538-52, we find the model corroborating the observations;
whereas in GX 301-2, the stellar wind appears to be very clumpy and a smooth
symmetric wind model seems to be inadequate in explaining the variation in
column density.


title:
Spectropolarimetric investigation of the propagation of magnetoacoustic
  waves and shock formation in sunspot atmospheres

abstract:
  Velocity oscillations in sunspot umbrae have been measured simultaneously in
two spectral lines: the photospheric Silicon I 10827 A line and the
chromospheric Helium I 10830 A multiplet. From the full Stokes inversion of
temporal series of spectropolarimetric observations we retrieved, among other
parameters, the line of sight velocity temporal variations at photospheric and
chromospheric heights. Chromospheric velocity oscillations show a three minute
period with a clear sawtooth shape typical of propagating shock wave fronts.
Photospheric velocity oscillations have basically a five minute period,
although the power spectrum also shows a secondary peak in the three minute
band which has proven to be predecessor for its chromospheric counterpart. The
derived phase spectra yield a value of the atmospheric cut-off frequency around
4 mHz and give evidence for the upward propagation of higher frequency
oscillation modes. The phase spectrum has been reproduced with a simple model
of linear vertical propagation of slow magneto-acoustic waves in a stratified
magnetized atmosphere that accounts for radiative losses through Newton's
cooling law. The model explains the main features in the phase spectrum, and
allows us to compute the theoretical time delay between the photospheric and
chromospheric signals, which happens to have a strong dependence on frequency.
We find a very good agreement between this and the time delay obtained directly
from the cross-correlation of photospheric and chromospheric velocity maps
filtered around the 6 mHz band. This allows us to infer that the 3-minute power
observed at chromospheric heights comes directly from the photosphere by means
of linear wave propagation, rather than from non-linear interaction of 5-minute
(and/or higher frequency) modes.


title: Analytical r-mode solution with gravitational radiation reaction force

abstract:
  We present and discuss the analytical r-mode solution to the linearized
hydrodynamic equations of a slowly rotating, Newtonian, barotropic,
non-magnetized, perfect-fluid star in which the gravitational radiation
reaction force is present.


title: H2 active jets in the near IR as a probe of protostellar evolution

abstract:
  We present a NIR analysis of a sample of H2 outflows from young embedded
sources to compare the physical properties and cooling mechanisms of the
different flows. The sample comprises 23 outflows driven by Class 0 and I
sources having low-intermediate luminosity. We have obtained narrow band images
in H2 2.12um and FeII 1.64um and spectroscopic observations in the range
1-2.5um. H2 line ratios have been used to estimate the visual extinction and
average temperature of the molecular gas. Av values range from 2 to 15mag;
average temperatures range between 2000 and 4000K. In several knots a
stratification of temperatures is found with maximum values up to 5000K. Such a
stratification is more commonly observed in those knots which also show FeII
emission, while a thermalized gas at a single temperature is generally found in
knots emitting only in molecular lines. Combining narrow band imaging with the
parameters derived from the spectral analysis, we are able to measure the total
luminosity of the H2 and FeII shocked regions in each flow. H2 is the major IR
coolant with an average L(H2)/L(FeII) ratio of 10^{-2}. 83% of the sources have
a L(H2)/L(bol) ratio of 0.04, irrespective of the Class of the driving source,
while a smaller group of sources have L(H2)/L(bol) an order of magnitude
smaller.Such a separation reveals the non-homogeneous behaviour of ClassI,
where sources with very different outflow activity can be found. This is
consistent with other studies showing that among ClassI one can find objects
with different accretion properties and it demonstrates that the H2 power in
the jet can be a powerful tool to identify the most active sources of this
class.


title: Do fast winds dominate the dynamics of planetary nebulae?

abstract:
  A review of recent observations of the kinematics of six objects that
represent the broad range of phenomena called planetary nebulae (PNe) is
presented. It is demonstrated that Hubble-type outflows are predominant,
consequently it is argued that ballistic ejections from the central stars could
have dominated the dynamical effects of the fast winds in several, and perhaps
all, of these objects. An alternative possibility, which involves an extension
to the Interacting Winds model, is considered to explain the dynamics of
evolved planetary nebuale.


title: Recent developments of the ACS spectral extraction software aXe

abstract:
  The software package aXe provides comprehensive spectral extraction
facilities for all the slitless modes of the ACS, covering the Wide Field
Channel (WFC) grism, the High Resolution Channel (HRC) grism and prism and the
Solar Blind Channel (SBC) prisms. The latest developments to the package apply
to all ACS slitless modes leading to improved spectral extraction. Many
thousands of spectra may be present on a single deep ACS WFC G800L image such
that overlap of spectra is a significant nuisance. Two methods of estimating
the contamination of any given spectrum by its near neighbours have been
developed: one is based on the catalogue of objects on the direct image;
another uses the flux information on multi-filter direct images. An improvement
to the extracted spectra can also result from weighted extraction and the Horne
optimal extraction algorithm has been implemented in aXe. A demonstrated
improvement in signal-to-noise can be achieved. These new features are
available in aXe-1.5 with the STSDAS 3.4 release.


title: Calibration of ACS Prism Slitless Spectroscopy Modes

abstract:
  The Advanced Camera for Surveys is equipped with three prisms in the Solar
Blind (SBC) and High Resolution (HRC) Channels, which together cover the 1150 -
3500 A range, albeit at highly non-uniform spectral resolution. We present new
wavelength- and flux calibrations of the SBC (PR110L and PR130L) and HRC
(PR200L) prisms, based on calibration observations obtained in Cycle 13. The
calibration products are available to users via the ST-ECF/aXe web pages, and
can be used directly with the aXe package. We discuss our calibration strategy
and some caveats specific to slitless prism spectroscopy.


title: Slitless spectroscopy with the Advanced Camera for Surveys

abstract:
  The Advanced Camera for Surveys (ACS) enables low resolution slitless
spectroscopic imaging in the three channels. The most-used modes are grism
imaging with the WFC and the HRC at a resolution of 40 and 24 A/pixel,
respectively. In the far UV there are two prisms for the SBC and a prism for
the HRC in the near-UV. An overview of the slitless spectroscopic modes of the
ACS is presented together with the advantages of slitless spectroscopy from
space. The methods and strategies developed to establish and maintain the
wavelength and flux calibration for the different channels are outlined. Since
many slitless spectra are recorded on one deep exposure, pipeline science
quality extraction of spectra is a necessity. To reduce ACS slitless data, the
aXe spectral extraction software has been developed at the ST-ECF. aXe was
designed to extract large numbers of ACS slitless spectra in an unsupervised
way based on an input catalogue derived from a companion direct image. In order
to handle dithered slitless spectra, drizzle, well-known in the imaging domain,
has been applied. For ACS grism images, the aXedrizzle technique resamples 2D
spectra from individual images to deep, rectified images before extracting the
1D spectra. aXe also provides tools for visual assessment of the extracted
spectra and examples are presented.


title: Supernovae Ia observations in the Lemaitre--Tolman model

abstract:
  The aim of this paper is to check if the models with realistic inhomogeneous
matter distribution and without cosmological constant can explain the dimming
of the supernovae in such a way that it can be interpreted as an acceleration
of the Universe. Employing the simplest inhomogeneous model, i.e.
Lemaitre-Tolman model, this paper examines the impact of inhomogeneous matter
distribution on light propagation. These analyses show that realistic matter
fluctuations on small scales induce brightness fluctuations in the residual
Hubble diagram of amplitude around 0.15 mag, and thus can mimic acceleration.
However, it is different on large scales. All these brightness fluctuations
decrease with distance and hence cannot explain the dimmining of supernovae for
high redshift without without invoking the cosmological constant.This paper
concludes that models with realistic matter distribution (i.e. where variation
of the density contrast is similar to what is observed in the local Universe)
cannot explain the observed dimming of supernovae without the cosmological
constant.


title: Cluster Masses from CMB and Galaxy Weak Lensing

abstract:
  Gravitational lensing can be used to directly constrain the projected density
profile of galaxy clusters. We discuss possible future constraints from lensing
of the CMB temperature and polarization, and compare to results from galaxy
weak lensing. We model the moving lens and kinetic SZ signals that confuse the
temperature CMB lensing when cluster velocities and angular momenta are
unknown, and show how they degrade parameter constraints. The CMB polarization
cluster lensing signal is ~1 micro-Kelvin for massive clusters and challenging
to detect; however it should be significantly cleaner than the temperature
signal and may provide the most robust constraints at low noise levels. Galaxy
lensing is likely to be much better for constraining cluster masses at low
redshift, but for clusters at redshift z >~ 1 future CMB lensing observations
may be able to do better.


title: Multiplicity-Study of Exoplanet Host Stars

abstract:
  We carry out a systematic search campaign for wide companions of exoplanet
host stars to study their multiplicity and its influence on the long-term
stability and the orbital parameters of the exoplanets. We have already found 6
wide companions, raising the number of confirmed binaries among the exoplanet
host stars to 20 systems. We have also searched for wide companions of Gl86,
the first known exoplanet host star with a white dwarf companion. Our Sofi/NTT
observations are sensitive to substellar companions with a minimum-mass of 35
Mjup and clearly rule out further stellar companions with projected separations
between 40 and 670AU.


title: Probing dark matter with X-ray binaries

abstract:
  Low-mass X-ray binaries (LMXBs), which occur in old stellar populations, have
velocities exceeding those of their parent distribution by at least 20 km/s.
This makes them ideal probes for dark matter, in particular in dwarf
spheroidals (dSph), where the LMXBs should penetrate well outside the visible
galaxy. We argue that the most likely explanation of the observation of LMXBs
in the Sculptor dSph by Maccarone et al (2005) is the presence of a dark matter
halo of >~ 10^9 Msun, corresponding to a total-mass to light ratio of >~ 600
(M/L_V)_sun. In this case there should be an extended halo of LMXBs which may
be observable.


title: Frequency dependence of orthogonal polarisation modes in pulsars

abstract:
  We have carried out a study of the orthogonal polarisation mode behaviour as
a function of frequency of 18 pulsars, using average pulsar data from the
European Pulsar Network (EPN). Assuming that the radiation consists of two 100%
polarised completely orthogonal superposed modes we separated these modes,
resulting in average pulse profiles of each mode at multiple frequencies for
each pulsar. Furthermore, we studied the frequency dependence of the relative
intensity of these modes. We found in many pulsars that the average pulse
profiles of the two modes differ in their dependence on frequency. In
particular, we found that pulse components that are dominated by one mode tend
to increase in intensity with increasing frequency with respect to the rest of
the profile.


title:
The Space Interferometry Mission Astrometric Grid Giant-Star Survey. I.
  Stellar Parameters and Radial Velocity Variability

abstract:
  We present results from a campaign of multiple epoch echelle spectroscopy of
relatively faint (V = 9.5-13.5 mag) red giants observed as potential
astrometric grid stars for the Space Interferometry Mission (SIM PlanetQuest).
Data are analyzed for 775 stars selected from the Grid Giant Star Survey
spanning a wide range of effective temperatures (Teff), gravities and
metallicities. The spectra are used to determine these stellar parameters and
to monitor radial velocity (RV) variability at the 100 m/s level. The degree of
RV variation measured for 489 stars observed two or more times is explored as a
function of the inferred stellar parameters. The percentage of radial velocity
unstable stars is found to be very high -- about 2/3 of our sample. It is found
that the fraction of RV-stable red giants (at the 100 m/s level) is higher
among stars with Teff \sim 4500 K, corresponding to the calibration-independent
range of infrared colors 0.59 < (J-K_s)_0 < 0.73. A higher percentage of
RV-stable stars is found if the additional constraints of surface gravity and
metallicity ranges 2.3< log g < 3.2 and -0.5 < [Fe/H] < -0.1, respectively, are
applied. Selection of stars based on only photometric values of effective
temperature (4300 K < Teff < 4700 K) is a simple and effective way to increase
the fraction of RV-stable stars. The optimal selection of RV-stable stars,
especially in the case when the Washington photometry is unavailable, can rely
effectively on 2MASS colors constraint 0.59 < (J-K_s)_0 < 0.73. These results
have important ramifications for the use of giant stars as astrometric
references for the SIM PlanetQuest.


title:
The age of the main population of the Sagittarius dwarf spheroidal
  galaxy. Solving the "M giant conundrum"

abstract:
  We present a statistically decontaminated Color Magnitude Diagram of a 1 deg
X 1 deg field in the core of the Sagittarius dSph galaxy. Coupling this CMD
with the most recent metallicity distributions obtained from high resolution
spectroscopy we derive robust constraints on the mean age of the stellar
population that dominates the galaxy (Pop A). Using three different sets of
theoretical isochrones in the metallicity range -0.4<= [M/H]<= -0.7 and taking
into consideration distance moduli in the range 16.90<= (m-M)_0<= 17.20 we find
that the mean age of Pop A is larger than 5 Gyr, and the best-fit value is age
= 8.0 +/- 1.5 Gyr. Since Pop A provides the vast majority of the M giants that
traces the tidal stream of Sgr dSph all over the sky, our estimate resolves the
so called ``M giant conundrum'' (Majewski et al. 2003). The time needed by the
M giants that currently populates the Stream to diffuse within the main body of
Sgr and to reach the extremes of the tidal tails once torn apart from the
parent galaxy (~ 3-4 Gyr) can be easily accommodated into the time lapsed since
their birth (~ 5.5-9.5 Gyr).


title:
Massive stars and the energy balance of the interstellar medium. II. The
  35 solar mass star and a solution to the "missing wind problem"

abstract:
  We continue our numerical analysis of the morphological and energetic
influence of massive stars on their ambient interstellar medium for a 35 solar
mass star that evolves from the main sequence through red supergiant and
Wolf-Rayet phases, until it ultimately explodes as a supernova. We find that
structure formation in the circumstellar gas during the early main-sequence
evolution occurs as in the 60 solar mass case but is much less pronounced
because of the lower mechanical wind luminosity of the star. Since on the other
hand the shell-like structure of the HII region is largely preserved, effects
that rely on this symmetry become more important. At the end of the stellar
lifetime 1% of the energy released as Lyman continuum radiation and stellar
wind has been transferred to the circumstellar gas. From this fraction 10% is
kinetic energy of bulk motion, 36% is thermal energy, and the remaining 54% is
ionization energy of hydrogen. The sweeping up of the slow red supergiant wind
by the fast Wolf-Rayet wind produces remarkable morphological structures and
emission signatures, which are compared with existing observations of the
Wolf-Rayet bubble S308. Our model reproduces the correct order of magnitude of
observed X-ray luminosity, the temperature of the emitting plasma as well as
the limb brightening of the intensity profile. This is remarkable, because
current analytical and numerical models of Wolf-Rayet bubbles fail to
consistently explain these features. A key result is that almost the entire
X-ray emission in this stage comes from the shell of red supergiant wind swept
up by the shocked Wolf-Rayet wind rather than from the shocked Wolf-Rayet wind
itself as hitherto assumed and modeled. This offers a possible solution to what
is called the ``missing wind problem'' of Wolf-Rayet bubbles.


title: A model for the X-ray absorption in Compton--thin AGN

abstract:
  The fraction of AGN with photoelectric absorption in the X-rays ranging from
NH of 10^{22} up to about 10^{24} cm^{-2} (Compton-thin) appears
observationally to be anticorrelated to their luminosity Lx. This recently
found evidence is used to investigate the location of the absorbing gas. The
molecular torus invoked in the unified picture of AGN, while it can be regarded
as confirmed on several grounds to explain the Compton-thick objects, do not
conform to this new constraint, at least in its physical models as developed so
far. In the frame of observationally based evidence that in Compton-thin
sources the absorbing gas might be located far away from the X-ray source, it
is shown that the gravitational effects of the black hole (BH) on the molecular
gas in a disk, within 25-450 pc (depending on the BH mass, from 10^6 to 10^9
M_solar, leads naturally to the observed anticorrelation, under the assumption
of a statistical correlation between the BH mass and Lx. Its normalization is
also reproduced provided that the surface density, Sigma, of this gas is larger
than about 150-200 M_solar pc^{-2}, and assuming that the bolometric luminosity
is one tenth of the Eddington limit. Interestingly, the required values are
consistent with the value of the 300 pc molecular disk in our own galaxy,
namely 500 M_solar pc^{-2}. In a sample of nearby galaxies from the BIMA SONG
survey, it is found that half of the objects have central Sigma larger than 150
M_solar pc${-2}. Given the simplicity of the proposed model, this finding is
very encouraging, waiting for future higher resolution surveys in CO on more
distant galaxies.


title:
The integrated bispectrum as a test of CMB non-Gaussianity: detection
  power and limits on f_NL with WMAP data

abstract:
  We propose a fast and efficient bispectrum statistic for Cosmic Microwave
Background (CMB) temperature anisotropies to constrain the amplitude of the
primordial non-Gaussian signal measured in terms of the non-linear coupling
parameter f_NL. We show how the method can achieve a remarkable computational
advantage by focussing on subsets of the multipole configurations, where the
non-Gaussian signal is more concentrated. The detection power of the test,
increases roughly linearly with the maximum multipole, as shown in the ideal
case of an experiment without noise and gaps. The CPU-time scales as l_{max}^3
instead of l_{max}^5 for the full bispectrum which for Planck resolution
l_{max} \sim 3000 means an improvement in speed of a factor 10^7 compared to
the full bispectrum analysis with minor loss in precision. We find that the
introduction of a galactic cut partially destroys the optimality of the
configuration, which will then need to be dealt with in the future. We find for
an ideal experiment with l_{max}=2000 that upper limits of f_{NL}<8 can be
obtained at 1 sigma. For the case of the WMAP experiment, we would be able to
put limits of |f_{NL}|<40 if no galactic cut were present. Using the real data
with galactic cut, we obtain an estimate of -80<f_{NL}<80 and -160<f_{NL}<160
at 1 and 2 sigma respectively.


title: J0041+3224: a new double-double radio galaxy

abstract:
  We report the discovery of a double-double radio galaxy (DDRG), J0041+3224,
with the Giant Metrewave Radio Telescope (GMRT) and subsequent high-frequency
observations with the Very Large Array (VLA). The inner and outer doubles are
aligned within about 4 deg and are reasonably collinear with the parent optical
galaxy. The outer double has a steeper radio spectrum compared with the inner
one. Using an estimated redshift of 0.45, the projected linear sizes of the
outer and inner doubles are 969 and 171 kpc respectively. The time scale of
interruption of jet activity has been estimated to be about 20 Myr, similar to
other known DDRGs. We have compiled a sample of known DDRGs, and have
re-examined the inverse correlation between the ratio of the luminosities of
the outer to the inner double and the size of the inner double, l_{in}. Unlike
the other DDRGs with l_{in} larger than about 50 kpc, the inner double of
J0041+3224 is marginally more luminous than the outer one. The two DDRGs with
l_{in} less than about a few kpc have a more luminous inner double than the
outer one, possibly due to a higher efficiency of conversion of beam energy as
the jets propagate through the dense interstellar medium. We have examined the
symmetry parameters and find that the inner doubles appear to be more
asymmetric in both its armlength and flux density ratios compared with the
outer doubles, although they appear marginally more collinear with the core
than the outer double. We discuss briefly possible implications of these
trends.


title: Guidelines for axion identification in astrophysical observations

abstract:
  The origin of various celestial phenomena have remained mysterious for
conventional astrophysics. Therefore, alternative solutions should be
considered, taking into account the involvement of unstable dark-matter
particle candidates, such as the celebrated axions or other as yet unforeseen
axion-like particles. Their spontaneous and induced decay by the ubiquitous
solar magnetic fields can be at the origin of persisting enigmatic X-ray
emission, giving rise to a steady and a transient/local solar activity,
respectively. The (coherent) conversion of photons into axion(-like) particles
in intrinsic magnetic fields may modify the solar axion spectrum. The reversed
process can be behind transient (solar) luminosity deficits in the visible.
Then, the Sun might be also a strong source of ~eV-axions. Thus, enigmatic
observations might be the as yet missing direct signature for axion(-like)
particles in earth-bound detectors.


title:
Saturn's Icy Moon Rhea: a Prediction for Bulk Chemical Composition and
  Physical Structure at the Time of the Cassini Spacecraft First Flyby

abstract:
  I report a model for the formation of Saturn's family of mid-sized icy moons
to coincide with the first flypast of Rhea by the Cassini Orbiter spacecraft on
26 November 2005. It is proposed that these moons had condensed from a
concentric family of orbiting gas rings that were cast off some 4600 Myr ago by
the contracting proto-Saturnian cloud. Numerical and structural models for Rhea
are constructed on the basis of a computed bulk chemical mix of hydrated rock
(mass fraction 0.385), H2O ice (0.395), and NH3 ice (0.220). The large
proportion of NH3 in the ice mass inhibits the formation of the dense
crystalline phase II of H2O ice at the satellite's centre. This may explain the
absence of compressional features on the surface. The favoured model of Rhea
has a chemically uniform interior and is very cold. The satellite is nearly
isodense and the predicted value of the axial moment-of-inertia factor is
C/MR^2 = 0.399 +/- 0.004. NH3 is unstable at Saturn's distance from the Sun,
except near the polar regions of the satellite. Perhaps the Cassini Orbiter
will discover indirect evidence for NH3 through the sublimative escape of this
ice from the outer layers, especially near the equatorial zones. Wasting of NH3
would weaken the residual soil, so making the edges of craters soft and prone
to landslides. It will be exciting to learn what Cassini discovers.


title:
Adaptive Optics Imaging of Low-redshift Damped Lyman-alpha Quasar
  Absorbers

abstract:
  We have carried out a high angular resolution near-infrared imaging study of
the fields of 6 quasars with 7 strong absorption line systems at z < 0.5, using
the Hokupa'a adaptive optics system and the QUIRC near-infrared camera on the
Gemini-North telescope. These absorption systems include 4 classical damped
Lyman-alpha absorbers (DLAs), 2 sub-DLAs, and one Lyman-limit system. Images
were obtained in the H or K' filters with FWHM between 0.2"-0.5" with the goal
of detecting the absorbing galaxies and identifying their morphologies.
Features are seen at projected separations of 0.5"-16.0" from the quasars and
all of the fields show features at less than 2" separation. We find candidate
absorbers in all of the seven systems. With the assumption that some of these
are associated with the absorbers, the absorbers are low luminosity < 0.1 L*_H
or L*_K; we do not find any large bright candidate absorbers in any of our
fields. Some fields show compact features that are too faint for quantitative
morphology, but could arise in dwarf galaxies.


title: Chaplygin gas may prevent big trip

abstract:
  This paper deals with the study of the accretion of a generalized Chaplygin
gas with equation of state $p=-A/\rho^\alpha$ onto wormholes. We have obtained
that when dominant energy condition is violated the size of wormhole increases
with the scale factor up to a given plateau. On the regime where the dominant
energy condition is satisfied our model predicts a steady decreasing of the
wormhole size as generalized Chaplygin gas is accreted. Our main conclusion is
that the big trip mechanism is prevented in a large region of the physical
parameters of the used model.


title:
Kinematics and star formation activity in the z=2.03954 damped
  Lyman-alpha system towards PKS 0458-020

abstract:
  We present UVES observations of the log N(HI)= 21.7 damped Lyman-alpha system
at z=2.03954 towards the quasar PKS 0458-020. HI Lyman-alpha emission is
detected in the center of the damped Lyman-alpha absorption trough.
Metallicities are derived for MgII, SiII, PII, CrII, MnII, FeII and ZnII and
are found to be -1.21\pm0.12, -1.28\pm0.20, -1.54\pm0.11, -1.66\pm0.10,
-2.05\pm0.11, -1.87\pm0.11, -1.22\pm0.10, respectively, relative to solar. The
depletion factor is therefore of the order of [Zn/Fe]=0.65. We observe metal
absorption lines to be blueshifted compared to the Lyman-alpha emission up to a
maximum of 100 and 200 km/s for low and high-ionization species respectively.
This can be interpreted either as the consequence of rotation in a large
(~7kpc) disk or as the imprint of a galactic wind. The star formation rate
(SFR) derived from the Lyman-alpha emission, 1.6 solar masses/yr, is compared
with that estimated from the observed CII* absorption. No molecular hydrogen is
detected in our data, yielding a molecular fraction f<-6.52. This absence of H2
can be explained as the consequence of a high ambient UV flux which is one
order of magnitude larger than the radiation field in the ISM of our Galaxy and
originates in the observed emitting region.


title:
Objective Subclass Determination of Sloan Digital Sky Survey Unknown
  Spectral Objects

abstract:
  We analyze a portion of the SDSS photometric catalog, consisting of
approximately 10,000 objects that have been spectroscopically classified into
stars, galaxies, QSOs, late-type stars and unknown objects (spectroscopically
unclassified objects, SUOs), in order to investigate the existence and nature
of subclasses of the unclassified objects. We use a modified mixture modeling
approach that makes use of both labeled and unlabeled data and performs class
discovery on the data set. The modeling was done using four colors derived from
the SDSS photometry: (u-g), (g-r), (r-i), and (i-z). This technique discovers
putative novel classes by identifying compact clusters that largely contain
objects from the spectroscopically unclassified class of objects. These
clusters are of possible scientific interest because they represent structured
groups of outliers, relative to the known object classes. We identify two such
well defined subclasses of the SUOs. One subclass contains 58% SUOs, 40% stars,
and 2% galaxies, QSOs, and late-type stars. The other contains 91% SUOs, 6%
late-type stars, and 3% stars, galaxies, and QSOs. We discuss possible
interpretations of these subclasses while also noting some caution must be
applied to purely color-based object classifications. As a side benefit of this
limited study we also find two distinct classes, consisting largely of
galaxies, that coincide with the recently discussed bimodal galaxy color
distribution.


title: Critical revision of the ZEPLIN-I sensitivity to WIMP interactions

abstract:
  The ZEPLIN collaboration has recently published its first result presenting a
maximum sensitivity of $1.1 \times 10^{-6}$ picobarn for a WIMP mass of
$\approx$ 60 GeV. The analysis is based on a discrimination method using the
different time distribution of scintillation light generated in electron recoil
and nuclear recoil interactions. We show that the methodology followed both for
the calibration of the ZEPLIN-I detector response and for the estimation of the
discrimination power is not reliable enough to claim any background
discrimination at the present stage. The ZEPLIN-I sensitivity appears then to
be in the order of 10$^{-3}$ picobarn, three orders of magnitude above the
claimed 1.1 10$^{-6}$ picobarn.


title: The AGN tori sizes: a remark on astro-ph/0512025 by Moshe Elitzur

abstract:
  We point out that in Granato & Danese 1994 and Granato et al. 1997 we
predicted maximum observable sizes for the putative torus in NGC1068 of 10-20
pc, not "hundreds of parsecs" as stated by M. Elitzur in astro-ph/0512025.


title: CO J=6-5 observations of TW Hya with the SMA

abstract:
  We present the first images of the 691.473 GHz CO J=6-5 line in a
protoplanetary disk, obtained along with the 690 GHz dust continuum, toward the
classical T Tauri star TW Hya using the Submillimeter Array. Imaging in the CO
J=6-5 line reveals a rotating disk, consistent with previous observations of CO
J=3-2 and 2-1 lines. Using an irradiated accretion disk model and 2D Monte
Carlo radiative transfer, we find that additional surface heating is needed to
fit simultaneously the absolute and relative intensities of the CO J=6-5, 3-2
and 2-1 lines. In particular, the vertical gas temperature gradient in the disk
must be steeper than that of the dust, mostly likely because the CO emission
lines probe nearer to the surface of the disk. We have used an idealized X-ray
heating model to fit the line profiles of CO J=2-1 and 3-2 with Chi-square
analysis, and the prediction of this model yields CO J=6-5 emission consistent
with the observations.


title: The Role of Primordial Kicks on Black Hole Merger Rates

abstract:
  Primordial stars are likely to be very massive $\geq30\Msun$, form in
isolation, and will likely leave black holes as remnants in the centers of
their host dark matter halos in the mass range
  $10^{6}-10^{10}\Ms$. Such early black holes, at redshifts z$\gtsim10$, could
be the seed black holes for the many supermassive black holes found in galaxies
in the local universe. If they exist, their mergers with nearby supermassive
black holes may be a prime signal for long wavelength gravitational wave
detectors. We simulate formation of black holes in the center of high redshift
dark matter halos and explore implications of initial natal kick velocities
conjectured by some formation models. The central concentration of early black
holes in present day galaxies is reduced if they are born even with moderate
kicks of tens of km/s. The modest kicks allow the black holes to leave their
parent halo, which consequently leads to dynamical friction being less
effective on the lower mass black holes as compared to those still embedded in
their parent halos. Therefore, merger rates may be reduced by more than an
order of magnitude. Using analytical and illustrative cosmological N--body
simulations we quantify the role of natal kicks of black holes formed from
massive metal free stars on their merger rates with supermassive black holes in
present day galaxies. Our results also apply to black holes ejected by the
gravitational slingshot mechanism.


title:
Phantom-like behaviour in dilatonic brane-world scenario with induced
  gravity

abstract:
  The Dvali, Gabadadze and Porrati (DGP) model has a self-accelerating
solution, the positive branch, where the brane is asymptotically de Sitter. A
de Sitter space-time can be seen as a boundary between quintessence-like
behaviour and phantom-like behaviour. We show that in a 5D dilatonic bulk,
where the dilaton has an exponential potential, with an induced gravity term on
the brane, whose matter content corresponds only to vacuum energy, the positive
branch solution undergoes a phantom-like stage where it faces a curvature
singularity in its infinite future. The singularity can be interpreted as the
``big rip'' singularity pushed towards an infinite future cosmic time. The
phantom-like behaviour on the brane occurs without violating the null energy
condition. There is another solution, the negative branch, where the brane can
undergo an early-epoch (transient) inflationary phase induced by the dilaton
field.


title: Muon-Induced Background Study for Underground Laboratories

abstract:
  We provide a comprehensive study of the cosmic-ray muon flux and induced
activity as a function of overburden along with a convenient parameterization
of the salient fluxes and differential distributions for a suite of underground
laboratories ranging in depth from $\sim$1 to 8 km.w.e.. Particular attention
is given to the muon-induced fast neutron activity for the underground sites
and we develop a Depth-Sensitivity-Relation to characterize the effect of such
background in experiments searching for WIMP dark matter and neutrinoless
double beta decay.


title:
Polarization of light from warm clouds above an accretion disk: effects
  of strong-gravity near a black hole

abstract:
  We study polarization from scattering of light on a cloud in radial motion
along the symmetry axis of an accretion disk. Radiation drag from the disk and
gravitational attraction of the central black hole are taken into account, as
well as the effect of the cloud cooling in the radiation field. This provides
us with a self-consistent toy-model for predicted lightcurves, including the
linear polarization that arises from the scattering. Strong gravitational
lensing creates indirect images; these are formed by photons that originate
from the disk, get backscattered onto the photon circular orbit and eventually
redirected towards an observer. Under suitable geometrical conditions the
indirect photons may visibly influence the resulting magnitude of polarization
and light-curve profiles. Relevant targets are black holes in active galactic
nuclei and stellar-mass Galactic black-holes exhibiting episodic
accretion/ejection events.


title: Galaxies in SDSS and DEEP2: a quiet life on the blue sequence?

abstract:
  In the six billion years between redshifts z=1 and z=0.1, galaxies change due
to the aging of their stellar populations, the formation of new stars, and
mergers with other galaxies. Here I explore the relative importance of these
various effects, finding that while mergers are likely to be important for the
red galaxy sequence they are unlikely to affect more than 10% of the blue
galaxy sequence. I compare the galaxy population at redshift z=0.1 from the
Sloan Digital Sky Survey to that at z=1 from the Deep Extragalactic
Evolutionary Probe 2. Galaxies are bluer at z=1: the blue sequence by about 0.3
mag and the red sequence by about 0.1 mag, in redshift z=0.1 (u-g) color. I
evaluate the change in color and in the luminosity functions of the two
sequences using some simplistic stellar population synthesis models. These
models indicate that the luminous end of the red sequence fades less than
passive evolution allows by about 0.2 mag. Due to a lack of luminous blue
progenitors, ``dry'' mergers betweeen red galaxies then must create the
luminous red population at z=0.1, if stellar population models are correct. The
blue sequence colors and luminosity function are consistent with a reduction in
the star-formation rate since redshift z=1 by a factor of about three, with no
change in the number density to within 10%. These results restrict the number
of blue galaxies that can fall onto the red sequence by any process, and in
particular suggest that if mergers are catastrophic events they must be rare
for blue galaxies.


title:
The Duck Redux: An Improved Proper Motion Upper Limit for the Pulsar
  B1757-24 Near the Supernova Remnant G5.4-1.2

abstract:
  "The Duck" is a complicated non-thermal radio system, consisting of the
energetic radio pulsar B1757-24, its surrounding pulsar wind nebula G5.27-0.90
and the adjacent supernova remnant (SNR) G5.4-1.2. PSR B1757-24 was originally
claimed to be a young (~15 000 yr) and extreme velocity (>~1500 km/s) pulsar
which had penetrated and emerged from the shell of the associated SNR G5.4-1.2,
but recent upper limits on the pulsar's motion have raised serious difficulties
with this interpretation. We here present 8.5 GHz interferometric observations
of the nebula G5.27-0.90 over a 12-year baseline, doubling the time-span of
previous measurements. These data correspondingly allow us to halve the
previous upper limit on the nebula's westward motion to 14 milliarcseconds/yr
(5-sigma), allowing a substantive reevaluation of this puzzling object. We rule
out the possibility that the pulsar and SNR were formed from a common supernova
explosion ~15 000 yrs ago as implied by the pulsar's characteristic age, but
conclude that an old (>~70 000 yr) pulsar / SNR association, or a situation in
which the pulsar and SNR are physically unrelated, are both still viable
explanations.


title: Constraining the reionization history with QSO absorption spectra

abstract:
  We use a semi-analytical approach to simulate absorption spectra of QSOs at
high redshifts with the aim of constraining the cosmic reionization history. We
consider two physically motivated and detailed reionization histories: (i) an
Early Reionization Model (ERM) in which the intergalactic medium is reionized
by PopIII stars at $z\approx 14$, and (ii) a more standard Late Reionization
Model (LRM) in which overlapping, induced by QSOs and normal galaxies, occurs
at $z\approx 6$. From the analysis of current Ly$\alpha$ forest data at $z <
6$, we conclude that it is impossible to disentangle the two scenarios, which
fit equally well the observed Gunn-Peterson optical depth, flux probability
distribution function and dark gap width distribution. At $z>6$, however, clear
differences start to emerge which are best quantified by the dark gap and peak
width distributions. We find that 35 (zero) per cent of the lines of sight
within $5.7< z <6.3$ show dark gaps widths $>50$ Angstrom in the rest frame of
the QSO if reionization is not (is) complete at $z \gtrsim 6$. Similarly, the
ERM predicts peaks of width $\sim 1$ Angstrom in 40 per cent of the lines of
sight in the redshift range $6.0-6.6$; in the same range, LRM predicts no peaks
of width $>0.8$ Angstrom. We conclude that the dark gap and peak width
statistics represent superb probes of cosmic reionization if about ten QSOs can
be found at $z > 6$. We finally discuss strengths and limitations of our
method.


title: The First High-Resolution Spectra of 1.3 L Subdwarfs

abstract:
  We present the first high-resolution (R ~ 31,000) spectra of the cool sdL
2MASS0532, and what was originally identified as an early-type L subdwarf (sdL)
LSR1610-0040. Our work, in combination with contemporaneous work by Cushing and
Vacca, makes it clear that the latter object is more probably a mid-M dwarf
with an unusual composition that gives it some sub-dwarf spectral features. We
use the data to derive precise radial velocities for both objects and to
estimate space motion; both are consistent with halo kinematics. We measure the
projected rotational velocities, revealing very slow rotation for the old sd?M6
object \lsr. \twom exhibits rapid rotation of vsini = 65 +- 15km/s, consistent
with the behavior of L dwarfs. This means that the braking time for L dwarfs is
extremely long, or that perhaps they never slow down. A detailed comparison of
the atomic Rb and Cs lines to spectra of field L dwarfs shows the spectral type
\twom is consistent with being mid- to late-L. The Rb I and K I lines of \lsr\
are like an early-L dwarf, but the Cs I line is like a mid-M dwarf. The
appearance of the Ca II triplet in absorption in this object is very hard to
understand if it is not as least as warm as M6. We explain these effects in a
consistent way using a mildly metal-poor mid-M model. M subdwarfs have weak
metal-oxides and enhanced metal-hydrides relative to normal M dwarfs. \lsr\
exhibits metal-hydrides like an M dwarf but metal-oxides like a subdwarf. The
same explanation that resolves the atomic line discrepancy explains this as
well. We identify atomic lines of Ti around 9600 \AA and a small contribution
of FeH, but we cannot confirm a detection of TiH in the spectra of cool L
subdwarfs. High resolution spectroscopy has aided in beginning to understand
the complex molecular chemistry in metal-deficient and ultralow-mass objects.


title: UBVI CCD Photometry of the Old Open Cluster Berkeley 17

abstract:
  Photometric UBVI CCD photometry is presented for NGC 188 and Berkeley 17.
Color-magnitude diagrams (CMDs) are constructed and reach well past the
main-sequence turn-off for both clusters. Cluster ages are determined by means
of isochrone fitting to the cluster CMDs. These fits are constrained to agree
with spectroscopic metallicity and reddening estimates. Cluster ages are
determined to be 7.0+/-0.5 Gyr for NGC 188, and 10.0+/- 1.0 Gyr for Berkeley
17, where the errors refer to uncertainties in the relative age determinations.
These ages are compared to the ages of relatively metal-rich inner halo/thick
disk globular clusters and other old open clusters. Berkeley 17 and NGC 6791
are the oldest open clusters with an age of 10 Gyr. They are 2 Gyr younger than
the thick disk globular clusters. These results confirm the status of Berkeley
17 as one of the oldest known open cluster in the Milky Way, and its age
provides a lower limit to the age of the Galactic disk.


title:
Chemical Compositions of Red Giant Stars in Old Large Magellanic Cloud
  Globular Clusters

abstract:
  We have observed ten red giant stars in four old Large Magellanic Cloud
globular clusters with the high-resolution spectrograph MIKE on the Magellan
Landon Clay 6.5-m telescope. The stars in our sample have up to 20 elemental
abundance determinations for the alpha-, iron-peak, and neutron-capture element
groups. We have also derived abundances for the light odd-Z elements Na and Al.
We find NGC 2005 and NGC 2019 to be more metal-rich than previous estimates
from the Ca II triplet, and we derive [Fe/H] values closer to those obtained
from the slope of the red giant branch. However, we confirm previous
determinations for Hodge 11 and NGC 1898 to within 0.2 dex. The LMC cluster
[Mg/Fe] and [Si/Fe] ratios are comparable to the values observed in old
Galactic globular cluster stars, as are the abundances [Y/Fe], [Ba/Fe], and
[Eu/Fe]. The LMC clusters do not share the low-Y behavior observed in some
dwarf spheroidal galaxies. [Ca/Fe], [Ti/Fe], and [V/Fe] in the LMC, however,
are significantly lower than what is seen in the Galactic globular cluster
system. Neither does the behavior of [Cu/Fe] as a function of [Fe/H] in our LMC
clusters match the trend seen in the Galaxy, staying instead at a constant
value of ~0.8. Because not all [alpha/Fe] ratios are suppressed, these
abundance ratios cannot be attributed solely to the injection of Type Ia SNe
material, and instead reflect the differences in star formation history of the
LMC vs. the Milky Way. We conclude that many of the abundances in the LMC
globular clusters we observed are distinct from those observed in the Milky
Way, and these differences are intrinsic to the stars in those systems.


title: Roche Lobes in the Second Post-Newtonian Approximation

abstract:
  Close binary systems of compact stars, due to the emission of gravitational
radiation, may evolve into a phase in which the less massive star transfers
mass to its companion. We describe mass transfer by using the model of Roche
lobe overflow, in which mass is transferred through the first, or innermost,
Lagrange point. Under conditions in which gravity is strong, the shapes of the
equipotential surfaces and the Roche lobes are modified compared to the
Newtonian case. We present calculations of the Roche lobe utilizing the second
order post-Newtonian (2PN) approximation in the Arnowitt-Deser-Misner gauge.
Heretofore, calculations of the Roche lobe geometry beyond the Newtonian case
have not been available. Beginning from the general N-body Lagrangian derived
by Damour and Schaffer, we develop the Lagrangian for a test particle in the
vicinity of two massive compact objects. As an exact result for the
transverse-traceless part of the Lagrangian is not available, we devise an
approximation that is valid for regions close to the less massive star. We
calculate the Roche lobe volumes, and provide a simple fitting formula for the
effective Roche lobe radius analogous to that for the Newtonian case furnished
by Eggleton. In contrast to the Newtonian case, in which the effective Roche
radius depends only upon the mass ratio $q=m_1/m_2$, in the 2PN case the
effective Roche lobe radius also depends on the ratio $z=2 (m_1+m_2)/a$ of the
total mass and the orbital separation.


title: Turbulent magnetic dynamo excitation at low magnetic Prandtl number

abstract:
  Planetary and stellar dynamos likely result from turbulent motions in
magnetofluids with kinematic viscosities that are small compared to their
magnetic diffusivities. Laboratory experiments are in progress to produce
similar dynamos in liquid metals. This work reviews recent computations of
thresholds in critical magnetic Reynolds number above which dynamo
amplification can be expected for mechanically-forced turbulence (helical and
non-helical, short wavelength and long wavelength) as a function of the
magnetic Prandtl number $P_M$. New results for helical forcing are discussed,
for which a dynamo is obtained at $P_M=5\times10^{-3}$. The fact that the
kinetic turbulent spectrum is much broader in wavenumber space than the
magnetic spectrum leads to numerical difficulties which are bridged by a
combination of overlapping direct numerical simulations and subgrid models of
magnetohydrodynamic turbulence. Typically, the critical magnetic Reynolds
number increases steeply as the magnetic Prandtl number decreases, and then
reaches an asymptotic plateau at values of at most a few hundred. In the
turbulent regime and for magnetic Reynolds numbers large enough, both small and
large scale magnetic fields are excited. The interactions between different
scales in the flow are also discussed.


title: Dark Energy Anisotropic Stress and Large Scale Structure Formation

abstract:
  We investigate the consequences of an imperfect dark energy component on the
large scale structure. A phenomenological three parameter fluid description is
used to study the effect of dark energy on the cosmic microwave background
radiation (CMBR) and matter power spectrum. In addition to the equation of
state and the sound speed, we allow a nonzero viscosity parameter for the
fluid. Then anisotropic stress perturbations are generated in dark energy. In
general, we find that this possibility is not excluded by the present day
cosmological observations. In the simplest case when all of the three
parameters are constant, we find that the observable effects of the anisotropic
stress can be closely mimicked by varying the sound speed of perfect dark
energy. However, now also negative values for the sound speed, as expected for
adiabatic fluid model, are tolerable and in fact could explain the observed low
quadrupole in the CMBR spectrum. We investigate also structure formation of
imperfect fluid dark energy characterized by an evolving equation of state. In
particular, we study unified models of dark energy with dark matter, such as
the Chaplygin gas or the Cardassian expansion, with a shear perturbation
included. This can stabilize the growth of inhomogeneities in these models,
thus somewhat improving their compatibility with large scale structure
observations.


title: The Role of the Equation of State in Binary Mergers

abstract:
  Binary mergers involving black holes and neutron stars have been proposed as
major sources of gravitational waves, r--process nucleosynthesis, and gamma ray
bursters. In addition, they represent an important, and possibly unique,
observable that could distinguish between normal and self--bound neutron stars.
These two families of stars have distinctly different mass--radius
relationships resulting from their equations of state which can be revealed
during their mergers if stable mass transfer ensues. We consider two cases of
gravitational-radiation induced binary mergers: (i) a black hole and a normal
neutron star, and (ii) a black hole and a self-bound strange quark matter star.
We extend previous Newtonian analyses to incorporate the pseudo-general
relativistic Paczy\'nski-Wiita potential or a potential correct to
second--order post-Newtonian order in Arnowitt--Deser--Misner coordinates.
These potentials are employed to study both the orbital evolution of the binary
and the Roche lobe geometry that determines when and if stable mass transfer
between the components is possible. The Roche lobe geometry with pseudo-general
relativistic or post-Newtonian potentials has not heretofore been considered.
Our analysis shows that differences in the evolution of normal neutron stars
and strange quark matter stars are significant and could be detected in gravity
waves. Both the amplitude and frequencies of the wave pattern are affected. In
addition, details of the equation of state for either normal neutron stars or
strange quark stars may be learned. A single merger could reveal one or two
individual points of the mass-radius relation, and observations of several
mergers could map a significant portion of this relation.


title:
Numerical Simulations of the Onset and Stability of Dynamical Mass
  Transfer in Binaries

abstract:
  Hydrodynamical simulations of semi-detached, polytropic binary stars are
presented in an effort to study the onset and stability of dynamical mass
transfer events. Initial, synchronously rotating equilibrium models are
constructed using a self-consistent-field technique and then evolved with an
Eulerian hydrodynamics code in a fully self-consistent manner. We describe code
improvements introduced over the past few years that permit us to follow
dynamical mass-transfer events through more than 30 orbits. Mass-transfer
evolutions are presented for two different initial configurations: A
dynamically unstable binary with initial mass ratio (donor/accretor) $q_0 =
1.3$ that leads to a complete merger in $\sim 10$ orbits; and a
double-degenerate binary with initial mass ratio $q_0 = 0.5$ that, after some
initial unstable growth of mass transfer, tends to separate as the
mass-transfer rate levels off.


title:
The Phoenix Deep Survey: The star-formation rates and the stellar masses
  of EROs

abstract:
  We estimate the star-formation rates and the stellar masses of the Extremely
Red objects (EROs) detected in a 180arcmin2 Ks-band survey (Ks~20mag). This
sample is complemented by sensitive 1.4GHz radio observations (12micro-Jy;
1sigma rms) and multiwaveband photometric data (UBVRIJ) as part of the Phoenix
Deep Survey. For bright K<19.5mag EROs in this sample (I-K>4mag; total of 177)
we use photometric methods to discriminate dust-enshrouded active systems from
early-type galaxies and to constrain their redshifts. Radio stacking is then
employed to estimate mean radio flux densities of 8.6 (3sigma) and 6.4micro-Jy
(2.4sigma) for the dusty and early-type subsamples respectively. Assuming that
dust enshrouded active EROs are powered by star-formation the above radio flux
density at the median redshift of z=1 translates to a radio luminosity of
4.5e22W/Hz and a star-formation rate of SFR=25Mo/yr. Combining this result with
photometric redshift estimates we find a lower limit to the star-formation rate
density of ~0.02Mo/yr/Mpc^3 for the K<19.5mag dusty EROs in the range
z=0.85-1.35. Comparison with the SFR density estimated from previous ERO
samples (with similar selection criteria) using optical emission lines,
suffering dust attenuation, suggests a mean dust reddening of at least
E(B-V)~0.5 for this population. We further use the Ks-band luminosity as proxy
to stellar mass and argue that the dust enshrouded EROs in our sample are
massive systems, M>5e10Mo. We also find that EROs represent a sizable fraction
(~50%) of the number density of galaxies more massive than M=5e10Mo at z~1,
with almost equal contributions from dusty and early types. Similarly, we find
that EROs contribute about half of the mass density of the Universe at z~1
after taking into account incompleteness because of the limit K=19.5mag.


title: Source Extractor for Dummies v5

abstract:
  Source Extractor for Dummies is a user manual for the SEXtractor (Bertin and
Arnouts 1996) software package for the detection of astronomical sources in
fits-files of fields. It has seen much use as a quick tool and is constantly
updated with new features. This fifth installment of the user manual is to
catch up with these updates and improve explanations and illustration of SE
parameters.
  The manual was written by a user, not a developer and may be incomplete,
inaccurate or clearly copied from the official manual v2.3. In short: more
pages, more text, less spelling-errors and don't panic. full pdf at:
http://www-int.stsci.edu/~holwerda/se.html


title: Polarization transfer in pulsar magnetosphere

abstract:
  Propagation of radio waves in the ultrarelativistic magnetized
electron-positron plasma of pulsar magnetosphere is considered. Polarization
state of the original natural waves is found to vary markedly on account of the
wave mode coupling and cyclotron absorption. The change is most pronounced when
the regions of mode coupling and cyclotron resonance approximately coincide. In
cases when the wave mode coupling occurs above and below the resonance region,
the resultant polarization appears essentially distinct. The main result of the
paper is that in the former case the polarization modes become non-orthogonal.
The analytical treatment of the equations of polarization transfer is
accompanied by the numerical calculations. The observational consequences of
polarization evolution in pulsar plasma are discussed as well.


title:
Time-resolved observations of the short period CV SDSS
  J123813.73-033933.0

abstract:
  We observed a new and poorly studied cataclysmic variable (CV) SDSS
J123813.73-033933.0 to determine its classification and binary parameters.
Simultaneous time-resolved photometric and spectroscopic observations were
carried out to conduct period analysis and Doppler tomography mapping. From
radial velocity measurements of the Ha line we determined its orbital period to
be 0.05592+/-0.00035$ days (80.53min). This period is longer than the first
estimate of 76 min by Szkody et al. (2003), but still at the very edge of the
period limit for hydrogen-rich CVs. The spectrum shows double-peaked Balmer
emission lines flanked by strong broad Balmer absorption, indicating a dominant
contribution by the white dwarf primary star, and is similar to the spectra of
short-period low-mass transfer WZ Sge-like systems. The photometric light curve
shows complex variability. The system undergoes cyclic brightening up to 0.4
mags, which are of semi-periodic nature with periods of the order of 8-12
hours. We also detect a 40.25 min variability of ~0.15 mag corresponding to
half of the orbital period. Amplitude of the latter increases with the cyclic
brightening of the system. We discuss the variable accretion rate and its
impact on the hot spot as the most probable reason for both observed processes.
SDSS J123813.73-033933.0 is preliminary classified as a WZ Sge-like short
period system with low and unstable accretion rate.


title: 12C/13C in atmospheres of red giants and peculiar stars

abstract:
  We determine the carbon isotopic ratios in the atmospheres of some evolved
stars in both globular clusters and the disk of our Galaxy. Analysis of 12CO
and 13CO bands at 2.3 micron was carried out using fits to observed spectra of
red giants and Sakurai's object (V4334 Sgr). The dependence of theoretical
spectra on the various input parameters was studied in detail. The computation
of model atmospheres and a detailed abundance analysis was performed in a
self-consistent fashion. A special procedure for determining the best fits to
observed spectra was used. We show, that globular cluster giants with [Fe/H] <
-1.3 have a low 12C/13C = 4 +/- 1 abundance ration. In the spectra of Sakurai's
object (V4334 Sgr) taken between 1997-98, the 2.3 micron spectral region is
veiled by hot dust emission. By fitting UKIRT spectra we determined 12C/13C = 4
+/- 1 for the July, 1998 spectrum. CO bands in the spectra of ultracool dwarfs
are modelled as well.


title:
Discovery of Counter-Rotating Gas in the Galaxies NGC1596 and NGC3203
  and the Incidence of Gas Counter-Rotation in S0 Galaxies

abstract:
  We have identified two new galaxies with gas counter-rotation (NGC1596 and
NGC3203) and have confirmed similar behaviour in another one (NGC128), this
using results from separate studies of the ionized-gas and stellar kinematics
of a well-defined sample of 30 edge-on disc galaxies. Gas counter-rotators thus
represent 10+/-5% of our sample, but the fraction climbs to 21+/-11% when only
lenticular (S0) galaxies are considered and to 27+/-13% for S0s with detected
ionized-gas only. Those fractions are consistent with but slightly higher than
previous studies. A compilation from well-defined studies of S0s in the
literature yields fractions of 15+/-4% and 23+/-5%, respectively. Although
mainly based on circumstantial evidence, we argue that the counter-rotating gas
originates primarily from minor mergers and tidally-induced transfer of
material from nearby objects. Assuming isotropic accretion, twice those
fractions of objects must have undergone similar processes, underlining the
importance of (minor) accretion for galaxy evolution. Applications of gas
counter-rotators to barred galaxy dynamics are also discussed.


title: Gaps below strange star crusts

abstract:
  The gap caused by a strong electric field between the quark surface and
nuclear crust of a strange star is studied in an improved model including
gravity and pressure as well as electrostatic forces. The transition from gap
to crust is followed in detail. The properties of the gap are investigated for
a wide range of parameters assuming both color-flavor locked and non
color-flavor locked strange star cores. The maximally allowed crust density is
generally lower than that of neutron drip. Finite temperature is shown to
increase the gap width, but the effect is significant only at extreme
temperatures. Analytical approximations are derived and shown to provide useful
fits to the numerical results.


title: The periods of the intermediate polar RX J0153.3+7446

abstract:
  We present the first optical photometry of the counterpart to the candidate
intermediate polar RX J0153.3+7446. This reveals an optical pulse period of
2333s +/- 5s. Reanalysis of the previously published ROSAT X-ray data reveals
that the true X-ray pulse period is probably 1974s +/- 30s, rather than the
1414 s previously reported. Given that the previously noted orbital period of
the system is 3.94 h, we are able to identify the X-ray pulse period with the
white dwarf spin period and the optical pulse period with the rotation period
of the white dwarf in the binary reference frame, as commonly seen in other
intermediate polars. We thus confirm that RX J0153.3+7446 is indeed a typical
intermediate polar.


title:
Interpreting the Hydrogen IR Lines - Impact of Improved Electron
  Collision Data

abstract:
  We evaluate the effect of variations in the electron-impact excitation cross
sections on the non-LTE line formation for hydrogen in early-type stars. While
the Balmer lines are basically unaffected by the choice of atomic data, the
Brackett and Pfund series members allow us to discriminate between the
different models. Non-LTE calculations based on the widely-used approximations
of Mihalas, Heasley & Auer and of Johnson fail to simultaneously reproduce the
observed optical and IR spectra over the entire parameter range. Instead, we
recommend a reference model using data from ab-initio calculations up to
principal quantum number n<=7 for quantitative work. This model is of general
interest due to the ubiquity of the hydrogen spectrum.


title:
Probing the evolution of the near-IR luminosity function of galaxies to
  z ~ 3 in the Hubble Deep Field South

abstract:
  [Abridged] We present the rest-frame Js-band and Ks-band luminosity function
of a sample of about 300 galaxies selected in the HDF-S at Ks<23 (Vega). We use
calibrated photometric redshift together with spectroscopic redshift for 25% of
the sample. The sample has allowed to probe the evolution of the LF in the
three redshift bins [0;0.8), [0.8;1.9) and [1.9;4) centered at the median
redshift z_m ~ [0.6,1.2,3]. The values of alpha we estimate are consistent with
the local value and do not show any trend with redshift. We do not see evidence
of evolution from z=0 to z_m ~ 0.6 suggesting that the population of local
bright galaxies was already formed at z<0.8. On the contrary, we clearly detect
an evolution of the LF to z_m ~ 1.2 characterized by a brightening of M* and by
a decline of phi*. To z_m ~ 1.2 M* brightens by about 0.4-0.6 mag and phi*
decreases by a factor 2-3. This trend persists, even if at a less extent, down
to z_m ~ 3 both in the Js-band and in the Ks-band LF. The decline of the number
density of bright galaxies seen at z>0.8 suggests that a significant fraction
of them increases their stellar mass at 1<z<2-3 and that they underwent a
strong evolution in this redshift range. On the other hand, this implies also
that a significant fraction of local bright/massive galaxies was already in
place at z>3. Thus, our results suggest that the assembly of high-mass galaxies
is spread over a large redshift range and that the increase of their stellar
mass has been very efficient also at very high redshift at least for a fraction
of them.


title: Viscosity in cosmological simulations of clusters of galaxies

abstract:
  The physics of the intracluster medium, in particular the values for the
thermal conductivity and the viscosity are largely unknown and subject to an
ongoing debate. Here, we study the effect of viscosity on the thermal state of
the intracluster medium using three-dimensional cosmological simulations of
structure formation. It is shown that viscosity, provided it is not too far off
from the unmagnetised Spitzer value, has a significant effect on cluster
profiles. In particular, it aids in heating the cool cores of clusters. The
central cooling time of the most massive clusters in our simulation is
increased by more than an order of magnitude. In large clusters, viscous
heating may help to establish an entropy floor and to prevent a cooling
catastrophe.