title: [O II] line ratios

abstract:
  Based on new calculations we reconfirm the low and high density limits on the
forbidden fine structure line ratio [O II] I(3729)/I(3726): lim_{N_ e} --> 0} =
1.5 and lim_{N_ e} --> \infty} = 0.35. Employing [O II] collision strengths
calculated using the Breit-Pauli R-matrix method we rule out any significant
deviation due to relativistic effects from these canonical values. The present
results are in substantial agreement with older calculations by Pradhan (1976)
and validate the extensive observational analysis of gaseous nebulae by Copetti
and Writzel (2002) and Wang et al (2004) that reach the same conclusions. The
present theoretical results and the recent observational analyses differ
significantly from the calculations by MacLaughlin and Bell (1998) and Keenan
et al (1999). The new maxwellian averaged effective collision strengths are
presented for the 10 transitions among the first 5 levels to enable
computations of [O II] line ratios.


title: Scale-dependent bias and the halo model

abstract:
  We use a simplified version of the halo model with a power law power spectrum
to study scale dependence in galaxy bias at the very large scales relevant to
baryon oscillations. In addition to providing a useful pedagogical explanation
of the scale dependence of galaxy bias, the model provides an analytic tool for
studying how changes in the Halo Occupation Distribution (HOD) impact the scale
dependence of galaxy bias on scales between 10 and 1000 Mpc/h, which is useful
for interpreting the results of complex N-body simulations. We find that
changing the mean number of galaxies per halo of a given mass will change the
scale dependence of the bias, but that changing the way the galaxies are
distributed within the halo has a smaller effect on the scale dependence of
bias at large scales. We use the model to explain the decay in amplitude of the
baryon oscillations as k increases, and generalize the model to make
predictions about scale dependent galaxy bias when redshift space distortions
are introduced.


title:
Discovery of a nearby halo white dwarf with proper motion mu=2.55
  arcsec/yr

abstract:
  We report the discovery of PM J13420-3415, a faint (V=17) white dwarf with a
very high proper motion mu = 2.55 arcsec/yr. The star was found in the southern
sky extension of the SUPERBLINK proper motion survey. A red spectrum shows the
classical signature of a DA white dwarf, with a weak H-alpha line in absorption
as the only prominent feature. The star is also found to have a large radial
velocity V_rad = +212+/-15 km/s. At the adopted distance of 18 pc, the star has
a very large space motion of 313 km/s relative to the Sun. An integration of
the space motion shows that the star is on a nearly polar Galactic orbit, and
is thus an unambiguous member of the Galactic halo. However, with an estimated
effective temperature 5,000K < T_eff < 5,500K, the white dwarf appears to be
much younger than expected for a denizen of the halo. The apparent paradox can
be explained if the white dwarf is the relatively young (~2 Gyr) remnant of a
longer-lived (10-14 Gyr) main sequence star, in which case the object is
predicted to be a low-mass white dwarf with M ~ 0.45 M_sun.


title: On the Correlations of Massive Black Holes with their Host Galaxies

abstract:
  We address the correlations of black hole (BH) mass with four different
host-galaxy properties from eleven existing data sets. To guide theoretical
understanding, we first try to quantify the tightness of the intrinsic
correlations. Given the estimated measurement errors, we evaluate the
probability distribution of the residual variance in excess of that expected
from the measurement errors. Our central result is that the current data sets
do not allow definite conclusions regarding the quality of the true
correlations because the obtained probability distributions for the residual
variance overlap for most quantities. We then consider which of the relations
offer the best inferences of BH mass when there is no direct measurement
available. As with the residual variances, we find that the probability
distribution of expected uncertainty in inferred BH masses overlaps
significantly for most of the relations. Photometric methods would then be
preferred because the data are easier to obtain, as long as bulge-disk
decomposition or detailed modeling of the photometric profile (as in
\citet{graham:01}) do not present problems. Determining which correlation
offers the best inferences requires reducing the uncertainty in the expected
error in the inferred BH masses (the ``error on the error''). This uncertainty
is currently limited by uncertainty in the residual variance for all of the
relations.


title:
Exploring uncharted territory in particles physics using pulsating white
  dwarfs: Prospects

abstract:
  Pulsating white dwarfs, especially DBVs, can be used as laboratories to study
elusive particles such as plasmon neutrinos and axions. In the degenerate
interiors of DBVs, plasmon decay is the dominant neutrino producing process. We
can measure the neutrino luminosity using asteroseismology and constrain
plasmon neutrino rates. In the same way, we can measure any additional loss of
energy due to other weakly interacting particles, such as axions. Depending
upon their (theoretically largely unconstrained) mass, axions could be a
significant source of energy loss for DAVs as well. We are looking at what the
uncertainties in the observables are, and what mass and temperature range
minimizes them.


title: Driving in ZZ Ceti stars - Problem solved?

abstract:
  There is a fairly tight correlation between the pulsation periods and
effective temperatures of ZZ Ceti stars (cooler stars have longer periods).
This seems to fit the theoretical picture, where driving occurs in the partial
ionization zone, which lies deeper and deeper within the star as it cools. It
is reasonable to assume that the pulsation periods should be related to the
thermal timescale in the region where driving occurs. As that region sinks
further down below the surface, that thermal timescale increases. Assuming this
connection, the pulsation periods could provide an additional way to determine
effective temperatures, independent of spectroscopy. We explore this idea and
find that in practice, things are not so simple.


title: The Frequency of Carbon Stars Among Extremely Metal-Poor Stars

abstract:
  We demonstrate that there are systematic scale errors in the [Fe/H] values
determined by the Hamburg/ESO Survey (and by inference by the HK Survey in the
past) for certain extremely metal poor highly C-enhanced giants. The
consequences of these scale errors are that a) the fraction of carbon stars at
extremely low metallicities has been overestimated in several papers in the
recent literature b) the number of extremely metal poor stars known is somewhat
lower than has been quoted in the recent literature c) the yield for extremely
metal poor stars by the HES Survey is somewhat lower than is stated in the
recent literature. A preliminary estimate for the frequency of Carbon stars
among the giants in the HES sample with -4 < [Fe/H] < -2.0 dex is 7.4 +-2.9%;
adding an estimate for the C-enhanced giants with [C/Fe] > 1.0 dex without
detectable C2 bands raises the fraction to 14 +-4$%.
  We rely on the results of an extensive set of homogeneous detailed abundance
analyses of stars expected to have [Fe/H] < -3.0 dex selected from the HES to
establish these claims. We have found that the Fe-metallicity of the cooler
(Teff < 5200K) C-stars as derived from spectra taken with HIRES at Keck are a
factor of ~10 higher than those obtained via the algorithm used by the HES
project to analyze the moderate resolution follow-up spectra, which is
identical to that used until very recently by the HK Survey. This error in
Fe-abundance estimate for C-stars arises from a lowering of the emitted flux in
the continuum bandpasses of the KP (3933 A line of CaII) and particularly the
HP2 (Hdelta) indices used to estimate [Fe/H] due to absorption from strong
molecular bands.


title: On The Origin of the Local Group's Peculiar Velocity

abstract:
  We aim to settle the debate regarding the fraction of the Local Group's
peculiar velocity that is induced by structures beyond the Great Attractor by
calculating the dipole anisotropy of the largest, all-sky, truly X-ray selected
cluster sample compiled to date. The sample is the combination of the REFLEX
catalog in the southern hemisphere, the eBCS sample in the north, and the CIZA
survey in the Galactic plane. The composite REFLEX+eBCS+CIZA sample overcomes
many of the problems inherent to previous galaxy and cluster catalogs which
limited their effectiveness in determining the origin of the Local Group's
motion. From the dipole anisotropy present in the cluster distribution we
determine that 44% of the Local Group's peculiar velocity is due to infall into
the GA region, while 56% is in the form of a large-scale flow induced by more
distant overdensities between 130 and 180 h^-1 Mpc away. In agreement with
previous analyses, we find that the Shapley supercluster is the single
overdensity most responsible for the increase in the dipole amplitude beyond
130 h^-1 Mpc, generating 30.4% of the large-scale contribution. We find that
numerous groupings and loose associations of clusters at roughly the same
distance as the Shapley region induce a significant acceleration on the Local
Group. These include the well known Horologium-Reticulum concentration, as well
as newly noted associations centered on Abell 3667 and Abell 3391 and a string
of CIZA clusters near C1410 which may trace an extension of the Shapley complex
into the Zone of Avoidance. We also note that the large-scale anisotropy
measured in the cluster distribution near 150 h^-1 Mpc may be due to an
observed underdensity of clusters in the northern hemisphere near this
distance. (abridged)


title: Why is the Zel'dovich Approximation so Accurate?

abstract:
  Why does the Zel'dovich approximation (ZA) work well to describe
gravitational collapse in the universe? This problem is examined by focusing on
its dependence on the dimensionality of the collapse. The ZA is known to be
exact for a one-dimensional collapse. We show that the ZA becomes progressively
more accurate in the order of three-, two-, and one-dimensional collapses.
Furthermore, using models for spheroidal collapse, we show that the ZA remains
accurate in all collapses, which become progressively lower dimensional with
the passage of time. That is, the ZA is accurate because the essence of the
gravitational collapse is incorporated in the ZA.


title: Properties of Stars in the Subaru Deep Field

abstract:
  We investigate the properties of objects in the Subaru Deep Field (SDF),
using public catalogs constructed from images in several optical passbands.
Using a small subset of objects most likely to be stars, we construct a stellar
locus in three-dimensional color space. We then compare the position of all
objects relative to this locus to create larger samples of stars in the SDF
with rough spectral types. The number counts of stars defined in this way are
consistent with those of current models of the Galaxy.


title: Trojan pairs in the HD 128311 and HD 82943 planetary systems?

abstract:
  Two nearby stars, HD 128311 and HD 82943, are believed to host pairs of
Jupiter-like planets involved in a strong first order 2:1 mean motion resonance
(MMR). In this work we reanalyze available radial velocity (RV) measurements
and demonstrate that it is also possible to explain the observed RV variations
of the parents stars as being induced by a pair of Trojan planets (i.e., in a
1:1 MMR). We show that these Trojan configurations reside in extended zones of
stability in which such systems may easily survive in spite of large masses of
the planets, large eccentricities and nonzero mutual inclinations of their
orbits. We also show that HD 82943 could harbor a previously unknown third
planet about of 0.5 Jupiter masses in 2.1 AU orbit.


title:
The afterglow of GRB050709 and the nature of the short-hard gamma-ray
  bursts

abstract:
  The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs)
centres on the origin of the short-hard class, suspected on theoretical grounds
to result from the coalescence of neutron star or black hole binary systems.
Numerous searches for the afterglows of short-hard bursts have been made,
galvanized by the revolution in our understanding of long-duration GRBs that
followed the discovery in 1997 of their broadband (X-ray, optical, and radio)
afterglow emission. Here we present the discovery of the X-ray afterglow of a
short-hard burst whose accurate position allows us to unambiguously associate
it with a star-forming galaxy at redshift z=0.160, and whose optical lightcurve
definitively excludes a supernova association. Together with results from three
other recent short-hard bursts, this suggests that short-hard bursts release
much less energy than the long-duration GRBs. Models requiring young stellar
populations, such as magnetars and collapsars, are ruled out, while coalescing
degenerate binaries remain the most promising progenitor candidates.


title:
Changes in the subsurface stratification of the Sun with the 11-year
  activity cycle

abstract:
  We report on the changes of the Sun's subsurface stratification inferred from
helioseismology data. Using SOHO/MDI (SOlar and Heliospheric
Observatory/Michelson Doppler Imager) data for the last 9 years and, more
precisely, the temporal variation of f-mode frequencies, we have computed the
variation of the radius of subsurface layers of the Sun by applying
helioseismic inversions. We have found a variability of the ``helioseismic''
radius in antiphase with the solar activity, with the strongest variations of
the stratification being just below the surface around 0.995$R_{\odot}$.
Besides, the radius of the deeper layers of the Sun, between 0.975$R_{\odot}$
and 0.99$R_{\odot}$ changes in phase with the 11-year cycle.


title: IGR J16393-4643: a new heavily-obscured X-ray pulsar

abstract:
  An analysis of the high-energy emission from IGR J16393-4643 (=AX
J1639.0-4642) is presented using data from INTEGRAL and XMM-Newton. The source
is persistent in the 20-40 keV band at an average flux of 5.1x10^-11
ergs/cm2/s, with variations in intensity by at least an order of magnitude. A
pulse period of 912.0+/-0.1 s was discovered in the ISGRI and EPIC light
curves. The source spectrum is a strongly-absorbed (nH=(2.5+/-0.2)x10^23
atoms/cm2) power law that features a high-energy cutoff above 10 keV. Two iron
emission lines at 6.4 and 7.1 keV, an iron absorption edge >7.1 keV, and a soft
excess emission of 7x10^-15 ergs/cm2/s between 0.5-2 keV, are detected in the
EPIC spectrum. The shape of the spectrum does not change with the pulse. Its
persistence, pulsation, and spectrum place IGR J16393-4643 among the class of
heavily-absorbed HMXBs. The improved position from EPIC is R.A.
(J2000)=16:39:05.4 and Dec.=-46:42:12 (4" uncertainty) which is compatible with
that of 2MASS J16390535-4642137.


title:
Formation and evolution of late-type dwarf galaxies. I. NGC 1705 and NGC
  1569

abstract:
  (Abridged.) We present one-zone chemical evolution models for two dwarf
starburst galaxies, NGC 1705 and NGC 1569. Using information about the past
star formation history and initial mass function of the systems previously
obtained from Hubble Space Telescope colour-magnitude diagrams, we identify
possible scenarios of chemical enrichment and development of galactic winds. In
order not to overestimate the current metallicity of the interstellar gas
inferred from H II region spectroscopy, we suggest that the winds efficiently
remove from the galaxies the metal-rich ejecta of dying stars. Conversely,
requiring the final mass of neutral gas to match the value inferred from 21-cm
observations implies a relatively low efficiency of interstellar medium
entrainment in the outflow, thus confirming previous findings that the winds
driving the evolution of typical starbursts are differential. These conclusions
could be different only if the galaxies accrete huge fractions of unprocessed
gas at late times. By assuming standard stellar yields we obtain a good fit to
the observed nitrogen to oxygen ratio of NGC 1569, while the mean N/O ratio in
NGC 1705 is overestimated by the models. Reducing the extent of hot bottom
burning in low-metallicity intermediate-mass stars does not suffice to solve
the problem. Localized self-pollution from stars more massive than 60 MSun in
NGC 1705 and/or funneling of larger fractions of nitrogen through its winds are
then left to explain the discrepancy between model predictions and
observations. Inspection of the log(N/O) vs. log(O/H)+12 diagram for a sample
of dwarf irregular and blue compact dwarf galaxies in the literature favours
the latter hypothesis.


title:
The observable effects of a photospheric component on GRB's and XRF's
  prompt emission spectrum

abstract:
  A thermal radiative component is likely to accompany the first stages of the
prompt emission of Gamma-ray bursts (GRB's) and X-ray flashes (XRF's). We
analyze the effect of such a component on the observable spectrum, assuming
that the observable effects are due to a dissipation process occurring below or
near the thermal photosphere. We consider both the internal shock model and a
'slow heating' model as possible dissipation mechanisms. For comparable energy
densities in the thermal and the leptonic component, the dominant emission
mechanism is Compton scattering. This leads to a nearly flat energy spectrum
(\nu F_\nu \propto \nu^0) above the thermal peak at ~10-100 keV and below
10-100 MeV, for a wide range of optical depths 0.03 <~ \tau_{\gamma e} <~ 100,
regardless of the details of the dissipation mechanism or the strength of the
magnetic field. At lower energies steep slopes are expected, while above 100
MeV the spectrum depends on the details of the dissipation process. For higher
values of the optical depth, a Wien peak is formed at 100 keV - 1 MeV, and no
higher energy component exists. For any value of \tau_{\gamma e}, the number of
pairs produced does not exceed the baryon related electrons by a factor larger
than a few. We conclude that dissipation near the thermal photosphere can
naturally explain both the steep slopes observed at low energies and a flat
spectrum above 10 keV, thus providing an alternative scenario to the optically
thin synchrotron - SSC model.


title:
Linear coupling and over-reflection phenomena of magnetohydrodynamic
  waves in smooth shear flows

abstract:
  Special features of magnetohydrodynamic waves linear dynamics in smooth shear
flows are studied. Quantitative asymptotic and numerical analysis are performed
for wide range of system parameters when basic flow has constant shear of
velocity and uniform magnetic field is parallel to the basic flow. The special
features consist of magnetohydrodynamic wave mutual transformation and
over-reflection phenomena. The transformation takes place for arbitrary shear
rates and involves all magnetohydrodynamic wave modes. While the
over-reflection occurs only for slow magnetosonic and Alfv\'en waves at high
shear rates. Studied phenomena should be decisive in the elaboration of the
self-sustaining model of magnetohydrodynamic turbulence in the shear flows.


title: On the origin of the circular polarization in radio pulsars

abstract:
  Properties of circularly polarized waves are studied in the pulsar
magnetosphere plasma. It is shown that some observational characteristics of
the circular polarization observed in the pulsar radio emission can be
qualitatively explained in the framework of the model based on anomalous
Doppler resonance. Performed analysis provides that if the difference between
Lorentz factors of electrons and positrons is relatively high, one of the
circularly polarized waves becomes super-luminal and therefore can not be
generated by cyclotron instability. We suggest that this case corresponds to
the pulsars with the domination of one hand of circular polarization through
the whole averaged pulse profile at all observed frequencies. For intermediate
values of the difference between Lorentz factors both circularly polarized
waves are generated, but the waves of one handness are much more effectively
generated for high frequencies, whereas generation of another handness
dominates for low frequencies. This should correspond to the pulsars with
strong frequency dependence of the degree of circular polarization. The case of
relatively small difference between Lorentz factors corresponds to the pulsars
with sign reversal of the circular polarization in the centre of averaged pulse
profiles.


title: MOND as Modified Inertia

abstract:
  I briefly highlight the salient properties of modified-inertia formulations
of MOND, contrasting them with those of modified-gravity formulations, which
describe practically all theories propounded to date. Future data (e.g. the
establishment of the Pioneer anomaly as a new physics phenomenon) may prefer
one of these broad classes of theories over the other. I also outline some
possible starting ideas for modified inertia.


title: Probing the bispectrum at high redshifts using 21 cm HI observations

abstract:
  Observations of fluctuations in the redshifted 21 cm radiation from neautral
hydrogen (HI) are perceived to be an important future probe of the universe at
high redshifts. Under the assumption that at redshifts z less than 6
(Post-Reionization Era), the HI traces the underlying dark matter with a
possible bias, we investigate the possibility of using observations of
redshifted 21 cm radiation to detect the bispectrum arising from non-linear
gravitational clustering and from non-linear bias. We find that the expected
signal is ~ 0.1 mJy at 325 MHz (z=3.4) for the small baselines at the GMRT, the
strength being a few times larger at higher frequencies 610 MHz (z=1.3).
Further, the magnitude of the signal from the bispectrum is predicted to be
comparable to that from the power spectrum, allowing a detection of both in
roughly the same integration time. The HI signal is found to be uncorrelated
beyond frequency separations of 1.3 MHz whereas the continuum sources of
continuum are expected to be correlated across much larger frequencies.
  This signature can in principle be used to distinguish the HI signal from the
contamination. We also consider the possibility of using observations of the
bispectrum to determine the linear and quadratic bias parameters of the HI at
high redshifts, this having possible implications for theories of galaxy
formation.


title:
ELODIE metallicity-biased search for transiting Hot Jupiters II. A very
  hot Jupiter transiting the bright K star HD189733

abstract:
  Among the 160 known exoplanets, mainly detected in large radial-velocity
surveys, only 8 have a characterization of their actual mass and radius thanks
to the two complementary methods of detection: radial velocities and
photometric transit. We started in March 2004 an exoplanet-search programme
biased toward high-metallicity stars which are more frequently host extra-solar
planets. This survey aims to detect close-in giant planets, which are most
likely to transit their host star. For this programme, high-precision radial
velocities are measured with the ELODIE fiber-fed spectrograph on the 1.93-m
telescope, and high-precision photometry is obtained with the CCD Camera on the
1.20-m telescope, both at the Haute-Provence Observatory. We report here the
discovery of a new transiting hot Jupiter orbiting the star HD189733. The
planetary nature of this object is confirmed by the observation of both the
spectroscopic and photometric transits. The exoplanet HD189733b, with an
orbital period of 2.219 days, has one of the shortest orbital periods detected
by radial velocities, and presents the largest photometric depth in the light
curve (~ 3%) observed to date. We estimate for the planet a mass of 1.15 +-
0.04 Mjup and a radius of 1.26 +- 0.03 RJup. Considering that HD189733 has the
same visual magnitude as the well known exoplanet host star HD209458, further
ground-based and space-based follow-up observations are very promising and will
permit a characterization of the atmosphere and exosphere of this giant
exoplanet.


title: Strong lensing, cosmology and lensing halos

abstract:
  With future wide and deep cosmological sky surveys, a large number of
gravitationally lensed, multiply imaged systems will be found. In addition to
multiply imaged galaxies and quasars, sources will include transient events
like supernovae and gamma ray bursts in which case very accurate time delay
measurements are possible. Also, large numbers of systems with several lensed
sources behind a single lens will be observed. In this paper, we review and
compare different possibilities of using future strong lensing data to probe
lens matter distributions and to determine the Hubble parameter and the matter
density of the universe. Specifically, we investigate the possibility to break
the well-known degeneracy between dark matter halo profiles and the Hubble
parameter using observed flux ratios. We also investigate how strong lensing
can provide useful constraints on the matter density of the universe
independently of the flux ratios and other cosmological probes.


title: On the evolution of the black hole:spheroid mass ratio

abstract:
  We present the results of a study which uses the 3CRR sample of radio-loud
active galactic nuclei to investigate the evolution of the black-hole:spheroid
mass ratio in the most massive early-type galaxies from 0<z<2. Radio-loud
unification is exploited to obtain virial (line-width) black-hole mass
estimates from the 3CRR quasars, and stellar mass estimates from the 3CRR radio
galaxies, thereby providing black-hole and stellar mass estimates for a single
population of early-type galaxies. At low redshift (z<1) the 3CRR sample is
consistent with a black-hole:spheroid mass ratio of M_bh/M_sph ~0.002, in good
agreement with that observed locally for quiescent galaxies of similar stellar
mass (M_sph ~5x10^11 M_sun). However, over the redshift interval 0<z<2 the 3CRR
black-hole:spheroid mass ratio is found to evolve as M_bh/M_sph \propto
(1+z)^{2.07\pm0.76}, reaching M_bh/M_sph ~0.008 by redshift z~2. This evolution
is found to be inconsistent with the local black hole:spheroid mass ratio
remaining constant at a moderately significant level (98%). If confirmed, the
detection of evolution in the 3CRR black-hole:spheroid mass ratio further
strengthens the evidence that, at least for massive early-type galaxies, the
growth of the central supermassive black hole may be completed before that of
the host spheroid.


title:
The energetics, evolution, and stellar depletion of Li6 in the early
  Galaxy

abstract:
  Motivated by the recent report of a high Li6 ``plateau'' extending to low
metallicities in Galactic halo stars, we study the energetics of an early
production of Li6 through the interaction of energetic particles with the
interstellar medium. We then explore the potential of various candidate sources
of pre-galactic energetic particles and show that, in general, they fail to
satisfy the observational and theoretical requirements (especially if the Li6
plateau is at a considerably higher level than observed). Succesful candidates
appear to be: supernova explosions with abnormally low metal yield; the massive
black hole in the Galactic center (provided that it was formed early on and
that it was then radiating much more efficiently than today); and, perhaps, an
early accretion phase of supermassive black holes in galaxies. Assuming that
Li6 is indeed pre-galactic, we study the galactic evolution of the light
isotopes Li7, Li6, and Be in a self-consistent way. We find that the existence
of a Li6 plateau is hard to justify, unless a fine-tuned and
metallicity-dependent depletion mechanism of Li6 in stellar envelopes is
invoked. The depletion of Li6 should be different, both in magnitude and in its
metallicity dependence, than the depletion required to explain current
observations of Li (mostly Li7) in halo stars. If the recently reported Li6
``plateau'' is confirmed, our analysis suggests important implications for our
understanding of the production, evolution, and stellar depletion of the Li
isotopes.


title: The Distribution of Dark Matter in Spirals

abstract:
  In the past years a wealth of observations allowed to unravel the structural
properties of the Dark Matter Halos around spirals. First, their rotation
curves follow an Universal profile (URC) that can be described in terms of an
exponential thin stellar disk and a dark halo with a constant density core,
whose relative importance increases with galaxy luminosity. Careful studies of
individual objects reveal that dark halos have a core, whose size $r_0$
correlates with the central density $\rho_0$.
  These properties are in serious discrepancy with the cuspy density
distribution predicted by N-body simulations in collisionless $\Lambda$CDM
Cosmology.


title:
A Search for Radio Gravitational Lenses, Using the Sloan Digital Sky
  Survey and the Very Large Array

abstract:
  We report on a novel search for radio gravitational lenses. Using the Very
Large Array, we imaged ten candidates with both dual redshifts in Sloan Digital
Sky Survey spectra and 1.4 GHz radio flux >2 mJy in the FIRST survey. The VLA
maps show that in each case the radio emission is associated with the
foreground galaxy rather than being lensed emission from the background galaxy,
although at least four of our targets are strong lenses at optical wavelengths.
These SDSS dual-redshift systems do not have lensed radio emission at the
sensitivity of current radio surveys.


title: Atomic hydrogen in AGB circumstellar environments. A case study: X Her

abstract:
  We report the detection of the HI line at 21 cm from the circumstellar shell
around the AGB star X Her using the position-switching technique with the
Nancay Radio Telescope. At the star position the line shows 2 components: (i) a
broad one (FWHM ~ 13 km/s) centered at -72.2 km/s, and (ii) a narrow one (FWHM
\~ 4 km/s) centered at ~ -70.6 km/s. Our map shows that the source associated
to the broad component is asymmetric with material flowing preferentially
towards the North-East. This source extends to ~ 10 arcmin. (~ 0.4 pc) from the
star in that direction. On the other hand, the narrow component is detected
only at the star position and indicates material flowing away from the
observer. The total mass of atomic hydrogen is ~ 6.5 10^{-3} solar mass which,
within a factor 2, agrees with the estimate obtained from IRAS data at 60
microns.


title:
Numerical stability of mass transfer driven by Roche lobe overflow in
  close binaries

abstract:
  Numerical computation of the time evolution of the mass transfer rate in a
close binary can be and, in particular, has been a computational challenge.
Using a simple physical model to calculate the mass transfer rate, we show that
for a simple explicit iteration scheme the mass transfer rate is numerically
unstable unless the time steps are sufficiently small. In general, more
sophisticated explicit algorithms do not provide any significant improvement
since this instability is a direct result of time discretization. For a typical
binary evolution, computation of the mass transfer rate as a smooth function of
time limits the maximum tolerable time step and thereby sets the minimum total
computational effort required for an evolutionary computation. By methods of
``Controlling Chaos'' it can be shown that a specific implicit iteration
scheme, based on Newton's method, is the most promising solution for the
problem.


title:
Reconciling the local galaxy population with damped Ly-alpha cross
  sections and metal abundances

abstract:
  A comprehensive analysis of 355 high-quality WSRT HI 21-cm line maps of
nearby galaxies shows that the properties and incident rate of Damped
Lyman-alpha (DLA) absorption systems observed in the spectra of high redshift
QSOs are in good agreement with DLAs originating in gas disks of galaxies like
those in the z~0 population. Comparison of low-z DLA statistics with the HI
incidence rate and column density distribution f(N) for the local galaxy sample
shows no evidence for evolution in the integral "cross section density" below
z~1.5, implying that there is no need for a hidden population of galaxies or HI
clouds to contribute significantly to the DLA cross section. Compared with z~4,
our data indicates evolution of a factor of two in the comoving density along a
line of sight. We find that dN/dz(z=0)=0.045 +/- 0.006. The idea that the local
galaxy population can explain the DLAs is further strengthened by comparing the
properties of DLAs and DLA galaxies with the expectations based on our analysis
of local galaxies. The distribution of luminosities of DLA host galaxies, and
of impact parameters between QSOs and the centres of DLA galaxies, are in good
agreement with what is expected from local galaxies. Approximately 87% of low z
DLA galaxies are expected to be fainter than L* and 37 per cent have impact
parameters less than 1'' at z=0.5. The analysis shows that some host galaxies
with very low impact parameters and low luminosities are expected to be missed
in optical follow up surveys. The well-known metallicity-luminosity relation in
galaxies, in combination with metallicity gradients in galaxy disks, cause the
expected median metallicity of low redshift DLAs to be low (~1/7 solar), which
is also in good agreement with observations of low z DLAs. (Abridged)


title:
The role of rotation on Petersen Diagrams. The $ Pi_{1/0}(Omega)$ period
  ratios

abstract:
  The present work explores the theoretical effects of rotation in calculating
the period ratios of double-mode radial pulsating stars with special emphasis
on high-amplitude delta Scuti stars (HADS). Diagrams showing these period
ratios vs. periods of the fundamental radial mode have been employed as a good
tracer of non-solar metallicities and are known as Petersen diagrams (PD).In
this paper we consider the effect of moderate rotation on both evolutionary
models and oscillation frequencies and we show that such effects cannot be
completely neglected as it has been done until now. In particular it is found
that even for low-to-moderate rotational velocities (15-50 km/s), differences
in period ratios of some hundredths can be found. The main consequence is
therefore the confusion scenario generated when trying to fit the metallicity
of a given star using this diagram without a previous knowledge of its
rotational velocity.


title: Luminosity segregation in three clusters of galaxies (A119, 2443, 2218)

abstract:
  We use deep wide-field V-band imaging obtained with the Wide Field Camera at
the prime focus of the Issac Newton Telescope to study the spatial and
luminosity distribution of galaxies in three low redshift (0.04<z<0.2)
clusters: Abell 119, Abell 2443 and Abell 2218. The absolute magnitude limits
probed in these clusters are M_{V} - 5logh_{0.7} = -13.3, -15.4 and -16.7mag
respectively. The galaxy population, at all luminosities, along the
line-of-sight to the clusters can be described by the linear combination of a
King profile and a constant surface density of field galaxies. We find that,
for these three clusters, the core radius is invariant with intrinsic
luminosity of the cluster population to the above limits and thus there is no
evidence for luminosity segregation in these clusters. The exception is the
brightest galaxies in A2218 which exhibit a more compact spatial distribution.
We find the total projected luminosity distribution (within 1Mpc of the cluster
centre) can be well represented by a single Schechter function with moderately
flat faint-end slopes: alpha=-1.22 (A119), alpha=-1.11 (A2443) and alpha=-1.14
(A2218). We perform a geometric deprojection of the cluster galaxy population
and confirm that no `statistically significant' evidence of a change in the
shape of the luminosity distribution with cluster-centric radius exists. Again,
the exception being A2218 which exhibits a core region with a flatter faint-end
slope.


title:
Detection of Six Transneptunian Binaries with NICMOS: A High Fraction of
  Binaries in the Cold Classical Disk

abstract:
  We have analyzed a homogeneous set of observations of eighty-one
transneptunian objects obtained with the NIC2 camera on the Hubble Space
Telescope with the goal of identifying partially resolved binaries. Using
PSF-fitting we have identified six likely binaries in addition to the three new
binaries already found in this data set. We find that 11% of transneptunian
objects are binaries at separation and brightness limits of the NIC2 camera.
The identification of these new binaries significantly increases the known
lower limit to the binary fraction among transneptunian objects. The origin of
such a high fraction of binaries remains to be determined. Most interestingly,
detectable binaries appear to be about four times more common among the cold
classical disk than in the dynamically excited populations.


title:
Chemical analysis of carbon stars in the Local Group: I. The Small
  Magellanic Cloud and the Sagittarius dwarf spheroidal galaxy

abstract:
  We present the first results of our ongoing chemical study of carbon stars in
the Local Group of galaxies. We used spectra obtained with UVES at the 8.2 m
Kueyen-VLT telescope and a new grid of spherical model atmospheres for cool
carbon-rich stars which include polyatomic opacities, to perform a full
chemical analysis of one carbon star, BMB-B~30, in the Small Magellanic Cloud
(SMC) and two, IGI95-C1 and IGI95-C3, in the Sagittarius Dwarf Spheroidal (Sgr
dSph) galaxy. Our main goal is to test the dependence on the stellar
metallicity of the s-process nucleosynthesis and mixing mechanism occurring in
AGB stars. For these three stars, we find important s-element enhancements with
respect to the mean metallicity ([M/H]), namely [s/M]$\approx$+1.0, similar to
the figure found in galactic AGB stars of similar metallicity. The abundance
ratios derived between elements belonging to the first and second s-process
abundance peaks, corresponding to nuclei with a magic number of neutrons N=50
(88Sr, 89Y, 90Zr) and N=82 (138Ba, 139La, 140Ce, 141Pr), agree remarkably well
with the theoretical predictions of low mass (M $<3$~M$\_\odot$) metal-poor AGB
nucleosynthesis models where the main source of neutrons is the
$^{13}$C$(\alpha,n)^{16}$O reaction activated duringthe long interpulse phase,
in a small pocket located within the He-rich intershell. The derived C/O and
$^{12}$C/$^{13}$C ratios are, however, more difficult to reconcile with
theoretical expectations. Possible explanations, like the extrinsic origin of
the composition of these carbon stars or the operation of a non-standard mixing
process during the AGB phase (such as the {\it cool bottom process}), are
discussed on the basis of the collected observational constraints.


title:
Common Proper Motion Search for Faint Companions Around Early-Type Field
  Stars - Progress Report

abstract:
  The multiplicity of early-type stars is still not well established. The
derived binary fraction is different for individual star forming regions,
suggesting a connection with the age and the environment conditions. The few
studies that have investigated this connection do not provide conclusive
results. To fill in this gap, we started the first detailed
adaptive-optic-assisted imaging survey of early-type field stars to derive
their multiplicity in a homogeneous way. The sample has been extracted from the
Hipparcos Catalog and consists of 341 BA-type stars within ~300 pc from the
Sun. We report the current status of the survey and describe a Monte-Carlo
simulation that estimates the completeness of our companion detection.


title: New stellar members of the Coma Berenices open star cluster

abstract:
  We present the results of a survey of the Coma Berenices open star cluster
(Melotte 111), undertaken using proper motions from the USNO-B1.0 and
photometry from the 2MASS Point Source catalogues. We have identified 60 new
candidate members with masses in the range 1.007<M<$0.269M_solar. For each we
have estimated a membership probability by extracting control clusters from the
proper motion vector diagram. All 60 are found to have greater than 60 per cent
probability of being clusters more than doubling the number of known cluster
members. The new luminosity function for the cluster peaks at bright
magnitudes, but is rising at K~12, indicating that it is likely lower mass
members may exist. The mass function also supports this hypothesis.


title: Emission From Rotation-Powered Pulsars and Magnetars

abstract:
  I will review the latest developments in understanding the high-energy
emission of rotation-powered pulsars and magnetically-powered Anomalous X-ray
Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs). These fields have been
extremely active in the last few years, both observationally and theoretically,
driven partly by new X-ray data from Chandra, XMM-Newton and RXTE. At the same
time, the Parkes Multibeam Survey has discovered over 700 new radio pulsars,
some of them young and coincident with EGRET sources, and others having
magnetar-strength magnetic fields. These new observations are raising important
questions about neutron star birth and evolution, as well as the properties of
their high-energy emission.


title: 1-100 GeV Emission from Millisecond Pulsars

abstract:
  A number of rotation-powered millisecond pulsars are powerful sources of
X-ray emission. We present predictions for the spectral characteristics of
these sources at gamma-ray energies, using a model for acceleration and pair
cascades on open magnetic field lines above the polar caps. Since these pulsars
have low surface magnetic fields, the majority do not produce sufficient pairs
to completely screen the accelerating electric field allowing particle
acceleration to high altitude. The resulting emission above 1 GeV comes from
curvature radiation by primary electrons with radiation-reaction-limited
Lorentz factors. The spectra are very hard power-laws with exponential cutoffs
between 1 and 50 GeV, and the spectral power peaks near the cutoff energy.
Millisecond pulsars are thus ideal targets for air-Cherenkov detectors that are
able to reach energy thresholds below 50 GeV.


title: On the Origin of Sulfur

abstract:
  We present our work on the halo evolution of sulfur, based on observations of
the S I lines around 9220 A for ten stars for which the S abundance was
obtained previously from much weaker S I lines at 8694 A. We cannot confirm the
rise and the high [S/Fe] abundances for low [Fe/H], as claimed in the
literature from analysis of the 8694 A lines. The reasons for claims of an
increase in [S/Fe] with decreasing [Fe/H] are probably twofold: uncertainties
in the measurements of the weak 8694 A lines, and systematic errors in
metallicity determinations from Fe I lines. The near-infrared sulfur triplet at
9212.9, 9228.1, and 9237.5 A are preferred for an abundance analysis of sulfur
for metal-poor stars. Our work was presented in full by Ryde & Lambert (2004).


title: Did WMAP see Moving Local Structures?

abstract:
  The divergence of the momentum density field of the large scale structure
generates a secondary anisotropy contribution to the Cosmic Microwave
Background (CMB). While the effect is best described as a non-linear extension
to the well-known integrated Sachs-Wolfe effect, due to mathematical
coincidences, the anisotropy contribution is also described as the lensing of
the dipole seen in the rest-frame of a moving mass. Given the closeness, there
is a remote possibility that local concentrations of mass in the form of the
Great Attractor and the Shapley concentration generate large angular scale
fluctuations in CMB and could potentially be responsible, at least partly, for
some of the low-multipole anomalies in WMAP data. While the local anisotropy
contribution peaks at low multipoles, for reasonable models of the mass and
velocity distributions associated with local super structures we find that the
amplitude of temperature anisotropies is at most at a level of 10$^{-2}$ $\mu$K
and is substantially smaller than primordial fluctuations. It is extremely
unlikely that the momentum density of local mass concentrations is responsible
for any of the large angular scale anomalies in WMAP data.


title:
Wind ionization structure of the short-period eclipsing LMC Wolf-Rayet
  binary BAT99-129: preliminary results

abstract:
  BAT99-129 is a rare, short-period eclipsing Wolf-Rayet binary in the Large
Magellanic Cloud. We present here medium-resolution NTT/EMMI spectra that allow
us to disentangle the spectra of the two components and find the orbital
parameters of the binary. We also present VLT/FORS1 spectra of this binary
taken during the secondary eclipse, i.e. when the companion star passes in
front of the Wolf-Rayet star. With these data we are able to extract, for the
first time in absolute units for a WR+O binary, the sizes of the line emitting
regions.


title: Angular Diameter Amplitudes of Bright Cepheids

abstract:
  Expected mean angular diameters and amplitudes of angular diameter variations
are estimated for all monoperiodic Classical Cepheids brighter than <V> =
8.0mag. The catalog is intended to help selecting best Cepheid targets for
interferometric observations.


title: Double Mode Cepheids with Amplitude Modulation

abstract:
  Recent search for multiperiodicity in LMC Cepheids (Moskalik, Kolaczkowski &
Mizerski 2004) has led to discovery of periodic modulation of amplitudes and
phases in many of the first/second overtone (FO/SO) double mode pulsators. We
discuss observational characteristics and possible mechanisms responsible for
this behaviour.


title:
The short-duration GRB 050724 host galaxy in the context of the
  long-duration GRB hosts

abstract:
  We report optical and near-infrared broad band observations of the
short-duration GRB 050724 host galaxy, used to construct its spectral energy
distribution (SED). Unlike the hosts of long-duration gamma-ray bursts (GRBs),
which show younger stellar populations, the SED of the GRB 050724 host galaxy
is optimally fitted with a synthetic elliptical galaxy template based on an
evolved stellar population (age ~2.6 Gyr). The SED of the host is difficult to
reproduce with non-evolving metallicity templates. In contrast, if the short
GRB host galaxy metallicity enrichment is considered, the synthetic templates
fit the observed SED satisfactorily. The internal host extinction is low (A_v
\~< 0.4 mag) so it cannot explain the faintness of the afterglow. This short
GRB host galaxy is more massive (~5x10^10 Mo) and luminous (~1.1 L*) than most
of the long-duration GRB hosts. A statistical comparison based on the ages of
short- and long-duration GRB host galaxies strongly suggests that
short-duration GRB hosts contain, on average, older progenitors. These findings
support a different origin for short- and long-duration GRBs.


title: The Evolution of Barium and Europium in Local Dwarf Spheroidal Galaxies

abstract:
  By means of a detailed chemical evolution model, we follow the evolution of
barium and europium in four Local Group Dwarf Spheroidal Galaxies, in order to
set constraints on the nucleosynthesis of these elements and on the evolution
of this type of galaxies compared with the Milky Way. The model, which is able
to reproduce several observed abundance ratios and the present day total mass
and gas mass content of these galaxies, adopts up to date nucleosynthesis and
takes into account the role played by supernovae of different types (II, Ia)
allowing us to follow in detail the evolution of several chemical elements (H,
D, He, C, N, O, Mg, Si, S, Ca, Fe, Ba and Eu). By assuming that barium is a
neutron capture element produced in low mass AGB stars by s-process but also in
massive stars (in the mass range 10 - 30 $M_{\odot}$) by r-process, during the
explosive event of supernovae of type II, and that europium is a pure r-process
element synthesized in massive stars also in the range of masses 10 - 30
$M_{\odot}$, we are able to reproduce the observed [Ba/Fe] and [Eu/Fe] as
functions of [Fe/H] in all four galaxies studied. We confirm also the important
role played by the very low star formation efficiencies ($\nu$ = 0.005 - 0.5
Gyr$^{-1}$) and by the intense galactic winds (6-13 times the star formation
rate) in the evolution of these galaxies. These low star formation efficiencies
(compared to the one for the Milky Way disc) adopted for the Dwarf Spheroidal
Galaxies are the main reason for the differences between the trends of [Ba/Fe]
and [Eu/Fe] predicted and observed in these galaxies and in the metal-poor
stars of our Galaxy. Finally, we provide predictions for Sagittarius galaxy for
which data of only two stars are available.


title: The Dusty Disk of the Early Galaxy NGC 3656

abstract:
  SHARC II, 350-micron continuum and archival HST J-H band maps are presented
of NGC 3656, the brightest of our sample of six elliptical galaxies for which
resolved CO gas disks have recently been detected with 7''-spatial-resolution,
interferometry mapping. These gas disks confirm the conclusions of earlier
results showing optical dust lanes and unresolved CO that implied the common
existence of molecular gas in ellipticals and the disk-like structure of this
gas. The presented SHARC II mapping results provide the best to date resolved
FIR-submm extent of NGC 3656 and of any elliptical galaxy > 40 Mpc, showing
that dust of 29 K exists out to at least 1.8 kpc in this galaxy. These new data
are used in conjunction with the archival HST maps and other published data to
determine dust properties and associations with galactic structures, including
dominant heating sources such as nuclear-activity, star-formation or
diffuse-stellar radiation.


title: Properties of Resolved Star Clusters in M51

abstract:
  We present a study of compact star clusters in the nearby pair of interacting
galaxies NGC 5194/95 (M51), based on multifilter Hubble Space Telescope WFPC2
archival images. We have detected ~400 isolated clusters. Our requirement that
clusters be detected based only on their morphology results in the selection of
relatively isolated objects, and we estimate that we are missing the majority
(by a factor 4-6) of <10 Myr clusters due to crowding. Hence we focus on the
cluster population older than 10 Myr. An age distribution shows a broad peak
between 100-500 Myr, which is consistent with the crossing times of NGC 5195
through the NGC 5194 disk estimated in both single and multiple-passage
dynamical models. We estimate that the peak contains approximately 2.2-2.5
times more clusters than expected from a constant rate of cluster formation
over this time interval. We estimate the effective radii of our sample clusters
and find a median value of 3-4 pc. Additionally, we see correlations of
increasing cluster size with cluster mass (with a best fit slope of
0.14\pm0.03) at the 4sigma level, and with cluster age (0.06\pm0.02) at the
3sigma level. Finally, we report for the first time the discovery of faint,
extended star clusters in the companion, NGC 5195, an SB0 galaxy. These have
red [(V-I)>1.0] colors, effective radii >7 pc, and are scattered over the disk
of NGC 5195. Our results indicate that NGC 5195 is therefore currently the
third known barred lenticular galaxy to have formed so-called "faint fuzzy"
star clusters. (abridged)


title:
Star--forming galaxies at intermediate redshifts: morphology, ages and
  sizes

abstract:
  We present the analysis of the deepest near-UV image obtained with HST using
the WFPC2(F300W) as part of the parallel observations of the Ultra Deep Field
campaign. The U-band 10sigma limiting magnitude measured over 0.2 arcsec square
is m(AB)=27.5 which is 0.5 magnitudes deeper than that in the HDF-North. We
matched the U-band catalog with those in the ACS images taken during the GOODS
observations of the CDF-South and obtained photometric-z for 306 matched
objects. We find that the UV-selected galaxies span all the major morphological
types at 0.2<z_phot<1.2. However, disks are more common at lower redshifts,
0.2<z_phot<0.8. Higher-z objects (0.7<z_phot<1.2) are on average bluer than
lower-z and have spectral type typical of starbursts. Their morphologies are
compact, peculiar or low surface brightness galaxies. The average half-light
radius (rest-frame 1200--1800 A) of the UV-selected galaxies at 0.66<z_
phot<1.5 is 0.26 +- 0.01 arcsec (2.07 +- 0.08 kpc). The UV-selected galaxies
are on average fainter (M_B=-18.43+-0.13) than Lyman Break Galaxies
(M_B=-23+-1). Our sample includes early-type galaxies that are presumably
massive and forming stars only in their cores, as well as starburst-type
systems that are more similar to the LBGs, although much less luminous. This
implies that even the starbursts in our sample are either much less massive
than LBGs or are forming stars at a much lower rate or both. The low surface
brightness galaxies have no overlap with the LBGs and form an interesting new
class of their own.


title: Understanding the Equilibrium Structure of CDM Halos

abstract:
  N-body simulations find a universal structure for the halos which result from
the nonlinear growth of Gaussian-random-noise density fluctuations in the CDM
universe. This talk summarized our attempts to derive and explain this
universal structure by analytical approximation and simplified models. As an
example, we show here that a 1D spherical infall model involving a fluid
approximation derived from the Boltzmann equation can explain not only the halo
density profile but its phase-space density profile, as well.


title:
Discrete Self-Similarity Between RR Lyrae Stars And Singly-Excited
  Helium Atoms

abstract:
  Classical variable stars called RR Lyrae stars have pulsating outer envelopes
comprised of excited atoms. Here we demonstrate that the qualitative and
quantitative properties of RR Lyrae variables and one subclass of their atomic
scale constituents: singly-excited helium atoms undergoing transitions between
Rydberg states, share a remarkable degree of self-similarity. In terms of
masses, radii, oscillation periods, morphologies and kinematics the stellar and
atomic analogues obey a simple set of discrete self-similar scaling equations.
The concept of stellar/atomic self-similarity may prove useful in the search
for a deeper understanding of both stellar and atomic systems.


title: Calibrating M dwarf metallicities using molecular indices

abstract:
  We report progress in the calibration of a method to determine cool dwarf
star metallicities using molecular band strength indices. The molecular band
index to metallicity relation can be calibrated using chemical abundances
calculated from atomic line equivalent width measurements in high resolution
spectra. Building on previous work, we have measured Fe and Ti abundances in 32
additional M and K dwarf stars to extend the range of temperature and
metallicity covered. A test of our analysis method using warm star - cool star
binaries shows we can calculate reliable abundances for stars warmer than 3500
K. We have used abundance measurements for warmer binary or cluster companions
to estimate abundances in 6 additional cool dwarfs. Adding stars measured in
our previous work and others from the literature provides 76 stars with Fe
abundance and CaH2 and TiO5 index measurements. The CaH2 molecular index is
directly correlated with temperature. TiO5 depends on temperature and
metallicity. Metallicity can be estimated to within plus or minus 0.3 dex
within the bounds of our calibration, which extends from roughly [Fe/H] = +0.05
to -1.0 with a limited extension to -1.5.


title:
The Evolution of Stellar Mass in the NICMOS UDF and the CFHTLS Deep
  Fields

abstract:
  We measure the build-up of the stellar mass of galaxies from z=6 to z=1.
Using 15 band multicolour imaging data in the NICMOS Ultra Deep Field we derive
photometric redshifts and masses for 796 galaxies down to H_AB=26.5. The
derived evolution of the global stellar mass density of galaxies is consistent
with previous star formation rate density measurements over the observed range
of redshifts. Ongoing research in the CFHTLS Deep Fields confirms this result
at lower redshifts. Further, if the sample is split by morphological type, a
substantial increase is seen in the number of bulge dominated galaxies relative
to disk-dominated galaxies since z=1.


title:
Identifying Very Metal-Rich Stars with Low-Resolution Spectra: Finding
  Planet-Search Targets

abstract:
  We present empirical calibrations that estimate stellar metallicity,
effective temperature and surface gravity as a function of Lick/IDS indices.
These calibrations have been derived from a training set of 261 stars for which
(1) high-precision measurements of [Fe/H], T_eff and log g have been made using
spectral-synthesis analysis of HIRES spectra, and (2) Lick indices have also
been measured. Our [Fe/H] calibration, which has precision 0.07 dex, has
identified a number of bright (V < 9) metal-rich stars which are now being
screened for hot Jupiter-type planets. Using the Yonsei-Yale stellar models, we
show that the calibrations provide distance estimates accurate to 20% for
nearby stars.
  This paper outlines the second tier of the screening of planet-search targets
by the N2K Consortium, a project designed to identify the stars most likely to
harbor extrasolar planets. Discoveries by the N2K Consortium include the
transiting hot Saturn HD 149026 b (Sato et al. 2005, astro-ph/0507009) and HD
88133 b (Fischer et al. 2005). See Ammons et al. (2005, In Press) for a
description of the first tier of N2K metallicity screening, calibrations using
broadband photometry.


title: Effects of Cosmological Magnetic Helicity on the CMB

abstract:
  In this talk I present a short review of primordial magnetic helicity effects
on Cosmic Microwave Background (CMB) temperature and polarization anisotropies.
These effects allow us to test for cosmological magnetic helicity, however,
very accurate CMB fluctuation data is required. This scheme for magnetic
helicity detection is valid only for a cosmological magnetic field with a
present amplitude larger than $10^{-9}-10^{-10}$ Gauss.


title: WR 143: A Wolf-Rayet Binary

abstract:
  Near infrared spectroscopy and photometry of the Wolf-Rayet Star WR 143 (HD
195177) were obtained in the $JHK$ photometric bands. High resolution spectra
observed in the J and H bands exhibit narrow 1.083-micron He I line and the H I
Pa Beta and the Brackett series lines in emission superposed on the broad
emission line spectrum of the Wolf-Rayet star, giving strong indications of the
presence of a companion. From the narrow emission lines observed, the companion
is identified to be an early-type Be star. The photometric magnitudes exhibit
variations in the JHK bands which are probably due to the variability of the
companion star. The flux density distribution is too steep for a Wolf-Rayet
atmosphere. This is identified to be mainly due to the increasing contribution
from the early-type companion star towards shorter wavelengths.


title:
Searching for proto-brown dwarfs: Extending near IR spectroscopy of
  protostars below the hydrogen burning limit

abstract:
  Recent observations of nearby star forming regions have offered evidence that
young brown dwarfs undergo a period of mass accretion analogous to the T Tauri
phase observed in young stars. Brown dwarf analogs to stellar protostars,
however, have yet to be definitively observed. These young, accreting objects
would shed light on the nature of the dominant brown dwarf formation process,
as well as provide ideal laboratories to investigate the dependence of the
accretion mechanism on protostellar mass. Recent near infrared surveys have
identified candidate proto-brown dwarfs and characterized low mass protostars
in nearby star forming regions. These techniques allow near infrared spectra to
diagnose the effective temperature, accretion luminosity, magnetic field
strength and rotation velocity of young low mass stars across the
stellar/substellar boundary. The lowest mass proto-brown dwarfs (M < 40 M_Jup),
however, will prove challenging to observe given current near IR observational
capabilities.


title: Partial suppression of the radial orbit instability in stellar systems

abstract:
  It is well known that the simple criterion proposed originally by Polyachenko
and Shukhman (1981) for the onset of the radial orbit instability, although
being generally a useful tool, faces significant exceptions both on the side of
mildly anisotropic systems (with some that can be proved to be unstable) and on
the side of strongly anisotropic models (with some that can be shown to be
stable). In this paper we address two issues: Are there processes of
collisionless collapse that can lead to equilibria of the exceptional type?
What is the intrinsic structural property that is responsible for the sometimes
noted exceptional stability behavior? To clarify these issues, we have
performed a series of simulations of collisionless collapse that start from
homogeneous, highly symmetrized, cold initial conditions and, because of such
special conditions, are characterized by very little mixing. For these runs,
the end-states can be associated with large values of the global pressure
anisotropy parameter up to 2K_r/K_T \approx 2.75. The highly anisotropic
equilibrium states thus constructed show no significant traces of radial
anisotropy in their central region, with a very sharp transition to a radially
anisotropic envelope occurring well inside the half-mass radius (around 0.2
r_M). To check whether the existence of such almost perfectly isotropic
"nucleus" might be responsible for the apparent suppression of the radial orbit
instability, we could not resort to equilibrium models with the above
characteristics and with analytically available distribution function; instead,
we studied and confirmed the stability of configurations with those
characteristics by initializing N-body approximate equilibria (with given
density and pressure anisotropy profiles) with the help of the Jeans equations.


title:
Hubble Space Telescope and Ground-Based Observations of Type Ia
  Supernovae at Redshift 0.5: Cosmological Implications

abstract:
  We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q,
1999S, and 1999U, at redshift z~0.5. They were discovered in early 1999 with
the 4.0~m Blanco telescope at Cerro Tololo Inter-American Observatory by the
High-z Supernova Search Team (HZT) and subsequently followed with many
ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble
Space Telescope. We computed luminosity distances to the new SNe using two
methods, and added them to the high-z Hubble diagram that the HZT has been
constructing since 1995.
  The new distance moduli confirm the results of previous work. At z~0.5,
luminosity distances are larger than those expected for an empty universe,
implying that a ``Cosmological Constant,'' or another form of ``dark energy,''
has been increasing the expansion rate of the Universe during the last few
billion years.


title: Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium

abstract:
  We have analyzed the 9.7 and ``18'' micron interstellar silicate absorption
features along the line of sight toward four heavily extincted galactic WC-type
Wolf-Rayet (WR) stars. We construct two interstellar extinction curves from
1.25 to 25 micron using near-IR extinction measurements from the literature
along with the silicate profiles of WR 98a (representing the local ISM) and GCS
3 (representing the Galactic Center). We have investigated the mineralogy of
the interstellar silicates by comparing extinction profiles for amorphous
silicates with olivine and pyroxene stochiometry to the 9.7 and ``18'' micron
absorption features in the WR 98a spectrum. In this analysis, we have
considered solid and porous spheres and a continuous distribution of
ellipsoids. While it is not possible to simultaneously provide a perfect match
to both profiles, we find the best match requires a mixture of these two types
of compounds. We also consider iron oxides, aluminosilicates and silicate
carbide (SiC) as grain components. Iron oxides cannot be accommodated in the
observed spectrum, while the amount of Si in SiC is limited to <4%. Finally, we
discuss the cosmic elemental abundance constraints on the silicate mineralogy,
grain shape and porosity.


title:
Accurate magnetic field measurements of Vega-like stars and Herbig Ae/Be
  stars

abstract:
  We have obtained accurate circular spectropolarimetric observations for a
sample of Vega-like and Herbig Ae/Be stars with FORS1 at the VLT in an attempt
to detect their magnetic fields. No magnetic field could be diagnosed in any
Vega-like star. The most accurate determination of a magnetic field, at 2.6
sigma level, has been performed for the Vega-like star iota Cen for which we
have measured <B_z> = -77+-30 G. In the prototype of Vega-like stars, the star
beta Pictoris, which shows conspicuous signs of chromospheric activity, a
longitudinal magnetic field is measured only at ~1.5 sigma level. We diagnose
for the first time a longitudinal magnetic field at a level larger than 3 sigma
for the two Herbig Ae stars HD31648 and HD144432 and we confirm the previous
detection of a magnetic field in a third Herbig Ae star, HD139614. Finally, we
discuss the discovery of distinctive Zeeman features in the unusual Herbig Ae
star HD190073 where the Ca II doublet displays several components in both H and
K lines. From the measurement of circular polarization in all Balmer lines from
H_beta to H_8 we obtain <B_z> = +26+-34 G. However, using for the measurement
of circular polarization only the Ca II H and K lines, we are able to diagnose
a longitudinal magnetic field at 2.8 sigma level, <B_z> = +84+-30 G.


title: Evolution of magnetic fields in stars across the upper main sequence

abstract:
  To properly understand the physics of upper main sequence stars it is
particularly important to identify the origin of their magnetic fields.
Recently, we confirmed that magnetic fields appear in Ap stars of mass below 3
M_sun only if they have already completed at least approximately 30% of their
main-sequence lifetime. The absence of stars with strong magnetic fields close
to the ZAMS might be seen as an argument against the fossil field theories.
Here we present the results of our recent magnetic survey with FORS1 at the VLT
in polarimetric mode of a sample of A, B and Herbig Ae stars with previously
undetected magnetic fields and briefly discuss their significance for our
understanding of the origin of the magnetic fields in intermediate mass stars.


title:
A Search for Early Optical Emission at Gamma-Ray Burst Locations by the
  Solar Mass Ejection Imager (SMEI)

abstract:
  The Solar Mass Ejection Imager (SMEI) views nearly every point on the sky
once every 102 minutes and can detect point sources as faint as R~10th
magnitude. Therefore, SMEI can detect or provide upper limits for the optical
afterglow from gamma-ray bursts in the tens of minutes after the burst when
different shocked regions may emit optically. Here we provide upper limits for
58 bursts between 2003 February and 2005 April.


title:
The Sunyaev-Zel'dovich effect in a sample of 31 clusters - a comparison
  between the X-ray predicted and WMAP observed CMB temperature decrement

abstract:
  The WMAP Q, V, and W band radial profiles of temperature deviation of the
cosmic microwave background (CMB) were constructed for a sample of 31 randomly
selected nearby clusters of galaxies in directions of Galactic latitude $|b| >$
30$^o$. The profiles were compared in detail with the expected CMB
Sunyaev-Zel'dovich effect (SZE) caused by these clusters, with the hot gas
properties of each cluster inferred observationally by applying gas
temperatures as measured by ASCA to isothermal $\beta$ models of the ROSAT
X-ray surface brightness profiles, and with the WMAP point spread function
fully taken into consideration. After co-adding the 31 cluster field, it
appears that WMAP detected the SZE in all three bands. Quantitatively, however,
the observed SZE only accounts for about 1/4 of the expected decrement. The
discrepancy represents too much unexplained extra flux: in the W band, the
detected SZE corresponds on average to 5.6 times less X-ray gas mass within a
10 arcmin radius than the mass value given by the ROSAT $\beta$ model. We
examined critically how the X-ray prediction of the SZE may depend on our
uncertainties in the density and temperature of the hot intracluster plasma,
and emission by cluster radio sources. Although our comparison between the
detected and expected SZE levels is subject to a margin of error, the fact
remains that the average observed SZE depth and profile are consistent with
those of the primary CMB anisotropy, i.e. in principle the average WMAP
temperature decrement among the 31 rich clusters is too shallow to accomodate
any extra effect like the SZE. A unique aspect of this SZE investigation is
that because all the data being analyzed are in the public domain, our work is
readily open to the scrutiny of others.


title:
An analysis of ultraviolet spectra of Extreme Helium Stars and new clues
  to their origins

abstract:
  Abundances of about 18 elements including the heavy elements Y and Zr are
determined from Hubble Space Telescope Space Telescope Imaging Spectrograph
ultraviolet spectra of seven extreme helium stars (EHes): LSE 78, BD+10 2179,
V1920 Cyg, HD 124448, PV Tel, LS IV -1 2, and FQ Aqr. New optical spectra of
the three stars -- BD+10 2179, V1920 Cyg, and HD 124448 were analysed. The
abundance analyses is done using LTE line formation and LTE model atmospheres
especially constructed for these EHe stars. The stellar parameters derived from
an EHe's UV spectrum are in satisfactory agreement with those derived from its
optical spectrum. Adopted abundances for the seven EHes are from a combination
of the UV and optical analyses. Published results for an additional ten EHes
provide abundances obtained in a nearly uniform manner for a total of 17 EHes,
the largest sample on record. The initial metallicity of an EHe is indicated by
the abundance of elements from Al to Ni; Fe is adopted to be the representative
of initial metallicity. Iron abundances range from approximately solar to about
one-hundredth of solar. Clues to EHe evolution are contained within the H, He,
C, N, O, Y, and Zr abundances. Two novel results are (i) the O abundance for
some stars is close to the predicted initial abundance yet the N abundance
indicates almost complete conversion of initial C, N, and O to N by the
CNO-cycles; (ii) three of the seven stars with UV spectra show a strong
enhancement of Y and Zr attributable to an s-process. The observed compositions
are discussed in light of expectations from accretion of a He white dwarf by a
CO white dwarf.


title:
On the non-occurrence of Type I X-ray bursts from the Black Hole
  Candidates

abstract:
  It has been justifiably questioned that if the Black Hole Candidates (BHCs)
have a ``hard surface'' why Type I X-ray bursts are not seen from them
(Nayayan, R., Black Holes in Astrophysics, New J. Phys., 7, 199-218, 2005). It
is pointed out that a ``physical surface'' need not always be ``hard'' and in
could be ``gaseous'' in case the compact object is sufficiently hot (Mitra, A.,
The day of reckoning: the value of the integration constant in the vacuum
Schwarzschild solution, physics/0504076, p1-p6; BHs or Eternally Collapsing
Objects: A review of 90 years of misconceptions, in Focus on Black Hole
Research, Nova Sc. Pub., NY, p1-p94, 2006). Even if a ``hard surface'' would be
there, presence of strong strong intrinsic magnetic field could inhibit Type I
X-ray burst from a compact object as is the case for Her X-1. Thus,
non-occurrence of Type I bursts actually rules out those alternatives of BHs
which are either non-magnetized or cold and, hence, is no evidence for
existence of Event Horizons (EHs). On the other hand, from the first principle,
we again show that the BHCs being uncharged and having finite masses cannot be
BHs, because uncharged BHs have a unique mass M=0. Thus the previous results
that the so-called BHCs are actually extremely hot, ultramagnetized,
Magnetospheric Eternally Collapsing Objects (MECOs) (Robertson, S. & Leiter,
D., Astrophys. J. 565, 447-451, 2002; MECO Model of galactic BH Candidates and
active galactic nuclei, in: New Developments in BLack Hole Research, NOva Sc.
Pub., NY, p1-p44, 2006) rather than anything else get reconfirmed by
non-occurrence of Type I X-ray bursts in BHCs.


title: Atmospheric Aerosol Limb Scanning Based on the Lunar Eclipses Photometry

abstract:
  The work is devoted to the analysis of the surface photometric observations
of two total lunar eclipses in 2004. The lunar surface relative brightness
distribution inside the umbra was used to retrieve the vertical distribution of
aerosol extinction of the solar radiation expanding by a tangent path and its
dependence on the location at the limb of the Earth. The upper altitude of
troposphere aerosol layer was estimated for different latitude zones. The
correlation between additional aerosol extinction in the upper troposphere and
cyclones was investigated.


title: Constraining topology in harmonic space

abstract:
  We consider several ways to test for topology directly in harmonic space by
comparing the measured a_lm with the expected correlation matrices. Two tests
are of a frequentist nature while we compute the Bayesian evidence as the third
test. Using correlation matrices for cubic and slab-space tori, we study how
these tests behave as a function of the minimal scale probed and as a function
of the size of the universe. We also apply them to different first-year WMAP
CMB maps and confirm that the universe is compatible with being infinitely big
for the cases considered. We argue that there is an information theoretical
limit (given by the Kullback-Leibler divergence) on the size of the topologies
that can be detected.


title:
UV dust attenuation in normal star forming galaxies: I. Estimating the
  L_TIR/L_FUV ratio

abstract:
  We analyze the dust attenuation properties of a volume-limited,
optically-selected sample of normal star forming galaxies in nearby clusters as
observed by GALEX. The internal attenuation is estimated using three
independent indicators, namely: the ratio of the total infrared to
far-ultraviolet emission, the ultraviolet spectral slope beta and the Balmer
decrement. We confirm that normal galaxies follow a L_TIR/L_FUV-beta relation
offset from the one observed for starburst galaxies. This offset is found to
weakly correlate with the birthrate parameter, thus with the galaxy star
formation history. We study the correlations of dust attenuation with other
global properties, such as the metallicity, dynamical mass, ionized gas
attenuation, Halpha emission and mass surface density. Metal-rich, massive
galaxies are, as expected, more heavily extinguished in the UV than are small
systems. For the same gas metallicity normal galaxies have lower L_TIR/L_FUV
ratio than starbursts, in agreement with the difference observed in the
L_TIR/L_FUV-beta relation. Unexpectedly we find however that normal star
forming galaxies follow exactly the same relationship between metallicity and
ultraviolet spectral slope beta determined for starbursts, complicating our
understanding of dust properties. This result might indicate a different dust
geometry between normal galaxies and starbursts, but it could also be due to
aperture effects eventually present in the IUE starbursts dataset. The present
multiwavelength study allows us to provide some empirical relations from which
the total infrared to far ultraviolet ratio (L_TIR/L_FUV) can be estimated when
far infrared data are absent.


title: Quantitative Spectroscopy of Supernovae for Dark Energy Studies

abstract:
  Detailed quantitative spectroscopy of Type Ia supernovae (SNe~Ia) provides
crucial information needed to minimize systematic effects in both ongoing SNe
Ia observational programs such as the Nearby Supernova Factory, ESSENCE, and
the SuperNova Legacy Survey (SNLS) and in proposed JDEM missions such as SNAP,
JEDI, and DESTINY.
  Quantitative spectroscopy is mandatory to quantify and understand the
observational strategy of comparing ``like versus like''. It allows us to
explore evolutionary effects, from variations in progenitor metallicity to
variations in progenitor age, to variations in dust with cosmological epoch. It
also allows us to interpret and quantify the effects of asphericity, as well as
different amounts of mixing in the thermonuclear explosion.


title:
Compton backscattered and primary X-rays from solar flares: angle
  dependent Green's function correction for photospheric albedo

abstract:
  The observed hard X-ray (HXR) flux spectrum $I(\epsilon)$ from solar flares
is a combination of primary bremsstrahlung photons $I_P(\epsilon)$ with a
spectrally modified component from photospheric Compton backscatter of downward
primary emission. The latter can be significant, distorting or hiding the true
features of the primary spectrum which are key diagnostics for acceleration and
propagation of high energy electrons and of their energy budget. For the first
time in solar physics, we use a Green's function approach to the backscatter
spectral deconvolution problem, constructing a Green's matrix including
photoelectric absorption. This approach allows spectrum-independent extraction
of the primary spectrum for several HXR flares observed by the {\it Ramaty High
Energy Solar Spectroscopic Imager} (RHESSI). We show that the observed and
primary spectra differ very substantially for flares with hard spectra close to
the disk centre. We show in particular that the energy dependent photon
spectral index $\gamma (\epsilon)=-d \log I/d \log \epsilon$ is very different
for $I_P(\epsilon)$ and for $I(\epsilon)$ and that inferred mean source
electron spectra ${\bar F}(E)$ differ greatly. Even for a forward fitting of a
parametric ${\bar F}(E)$ to the data, a clear low-energy cutoff required to fit
$I(\epsilon)$ essentially disappears when the fit is to $I_P(\epsilon)$ - i.e.
when albedo correction is included. The self-consistent correction for
backscattered photons is thus shown to be crucial in determining the energy
spectra of flare accelerated electrons, and hence their total number and
energy.


title:
Distances to six Cepheids in the LMC cluster NGC1866 from the near-IR
  surface-brightness method

abstract:
  We derive individual distances to six Cepheids in the young populous star
cluster NGC1866 in the Large Magellanic Cloud employing the near-IR surface
brightness technique. With six stars available at the exact same distance we
can directly measure the intrinsic uncertainty of the method. We find a
standard deviation of 0.11 mag, two to three times larger than the error
estimates and more in line with the estimates from Bayesian statistical
analysis by Barnes et al. (2005). Using all six distance estimates we determine
an unweighted mean cluster distance of 18.30+-0.05. The observations indicate
that NGC1866 is close to be at the same distance as the main body of the LMC.
If we use the stronger dependence of the p-factor on the period as suggested by
Gieren et al. (2005) we find a distance of 18.50+-0.05 (internal error) and the
PL relations for Galactic and MC Cepheids are in very good agreement.


title:
How good are RR Lyrae and Cepheids really as Distance Indicators? The
  observational approach

abstract:
  A number of recent technical developments, including the Hipparcos satellite,
the Hubble Space Telescope fine guidance sensors and long base line near-IR
interferometry has made it possible to employ several largely geometrical
methods to determine direct distances to RR Lyrae stars and Cepheids. The
distance scale now rests on a much firmer basis and the significant differences
between the distances based on RR Lyrae stars (short) and Cepheids (long) to
the LMC have been largely eliminated. The effects of metalicity on the RR Lyrae
period-luminosity (PL) relation in the K-band as well as on the Cepheid PL
relation appears to be the main remaining issues but even here empirical
results are beginning to show convergence. I review here some of these recent
developments seen from the perspective of the near-IR surface brightness
method.


title: Features of radio-detected Extensive Air Shower with CODALEMA

abstract:
  Some performances of the present CODALEMA experiment, set up to analyse
radio-detected Extensive Air Shower (EAS) events, are presented.
Characteristics of the EAS electric field distribution sampled on a 600~m long
axis are discussed.


title:
Low Mass Pre-Main Sequence stars in the Large Magellanic Cloud - II:
  HST-WFPC2 observations of two fields in the 30 Doradus region

abstract:
  As a part of an ongoing effort to characterise the young stellar populations
in the Large Magellanic Cloud, we present HST-WFPC2 broad and narrow band
imaging of two fields with recent star formation activity in the Tarantula
region. A population of objects with Halpha and/or Balmer continuum excess was
identified. On account of the intense Halpha emission (equivalent widths up to
several tens of Angstroms), its correlation with the Balmer continuum excess
and the stars' location on the HR diagram, we interpret them as low mass (~1-2
Mo) Pre-Main Sequence stars. In this framework, the data show that coeval high
and low mass stars have significantly different spatial distributions, implying
that star formation processes for different ranges of stellar masses are rather
different and/or require different initial conditions. We find that the overall
slope of the mass function of the young population is somewhat steeper than the
classical Salpeter value and that the star formation density of this young
component is 0.2-0.4 Mo/yr/kpc2, i.e. intermediate between the value for an
active spiral disk and that of a starburst region. The uncertainties associated
with the determination of the slope of the mass function and the star formation
density are thoroughly discussed.


title: Robust Limits on Lorentz Violation from Gamma-Ray Bursts

abstract:
  We constrain the possibility of a non-trivial refractive index in free space
corresponding to an energy-dependent velocity of light: c(E) \simeq c_0 (1 -
E/M), where M is a mass scale that might represent effect of
quantum-gravitational space-time foam, using the arrival times of sharp
features observed in the intensities of radiation with different energies from
a large sample of gamma-ray bursters (GRBs) with known redshifts. We use
wavelet techniques to identify genuine features, which we confirm in
simulations with artificial added noise. Using the weighted averages of the
time-lags calculated using correlated features in all the GRB light curves, we
find a systematic tendency for more energetic photons to arrive earlier.
However, there is a very strong correlation between the parameters
characterizing an intrinsic time-lag at the source and a distance-dependent
propagation effect. Moreover, the significance of the earlier arrival times is
less evident for a subsample of more robust spectral structures. Allowing for
intrinsic stochastic time-lags in these features, we establish a statistically
robust lower limit: M > 0.9x10^{16} GeV on the scale of violation of Lorentz
invariance.


title: A Galaxy Cluster Near NGC 720

abstract:
  The galaxy cluster RXJ 0152.7-1357 is emitting X-rays at the high rate of 148
counts $ks^{-1}$. It would be one of the most luminous X-ray clusters known if
it is at its redshift distance of z = .8325. It is conspicuously elongated,
however, toward the bright, X-ray active galaxy NGC 720 about 14 arcmin away.
At the same distance on the other side of NGC 720, and almost perfectly
aligned, is an X-ray BSO of 5.8 cts/ks. It is reported here that the redshift
of this quasar is z = .8312.


title: Near-Infrared Observations of RR Lyrae Variables in $\omega$ Centauri

abstract:
  We present Near-Infrared (NIR) $J$ and $K_s$-band observations for 181 RR
Lyrae stars in the Galactic Globular Cluster $\omega$ Cen. The comparison
between predicted and empirical slopes of NIR Period-Luminosity (PL) relations
indicates a very good agreement. Cluster distance estimates based on NIR PL
relations agree quite well with recent determinations based on different
standard candles, giving a true mean distance modulus $\mu = 13.71\pm0.05$, and
$d=5.52\pm0.13$ kpc.


title:
3D Gasdynamic Modelling of the Changes in the Flow Structure During
  Transition From Quiescent to Active State in Symbiotic Stars

abstract:
  The results of 3D modelling of the flow structure in the classical symbiotic
system Z~Andromedae are presented. Outbursts in systems of this type occur when
the accretion rate exceeds the upper limit of the steady burning range.
Therefore, in order to realize the transition from a quiescent to an active
state it is necessary to find a mechanism able to sufficiently increase the
accretion rate on a time scale typical to the duration of outburst development.
  Our calculations have confirmed the transition mechanism from quiescence to
outburst in classic symbiotic systems suggested earlier on the basis of 2D
calculations (Bisikalo et al, 2002). The analysis of our results have shown
that for wind velocity of 20 km/s an accretion disc forms in the system. The
accretion rate for the solution with the disc is ~22.5-25% of the mass loss
rate of the donor, that is, ~4.5-5*10^(-8)Msun/yr for Z And. This value is in
agreement with the steady burning range for white dwarf masses typically
accepted for this system. When the wind velocity increases from 20 to 30 km/s
the accretion disc is destroyed and the matter of the disc falls onto the
accretor's surface. This process is followed by an approximately twofold
accretion rate jump. The resulting accretion rate growth is sufficient for
passing the upper limit of the steady burning range, thereby bringing the
system into an active state. The time during which the accretion rate is above
the steady burning value is in a very good agreement with observations.
  The analysis of the results presented here allows us to conclude that small
variations in the donor's wind velocity can lead to the transition from the
disc accretion to the wind accretion and, as a consequence, to the transition
from quiescent to active state in classic symbiotic stars.


title: Observations on the Formation of Massive Stars by Accretion

abstract:
  Observations of the H66a recombination line from the ionized gas in the
cluster of newly formed massive stars, G10.6-0.4, show that most of the
continuum emission derives from the dense gas in an ionized accretion flow that
forms an ionized disk or torus around a group of stars in the center of the
cluster. The inward motion observed in the accretion flow suggests that despite
the equivalent luminosity and ionizing radiation of several O stars, neither
radiation pressure nor thermal pressure has reversed the accretion flow. The
observations indicate why the radiation pressure of the stars and the thermal
pressure of the HII region are not effective in reversing the accretion flow.
The observed rate of the accretion flow, 0.001 solar masses/yr, is sufficient
to form massive stars within the time scale imposed by their short main
sequence lifetimes. A simple model of disk accretion relates quenched HII
regions, trapped hypercompact HII regions, and photo-evaporating disks in an
evolutionary sequence.


title:
Water Vapor on Betelgeuse as Revealed by TEXES High-Resolution 12 Micron
  Spectra

abstract:
  The outer atmosphere of the M supergiant Betelgeuse is puzzling. Published
observations of different kinds have shed light on different aspects of the
atmosphere, but no unified picture has emerged. They have shown, for example,
evidence of a water envelope (MOLsphere) that in some studies is found to be
optically thick in the mid-infrared. In this paper, we present high-resolution,
mid-infrared spectra of Betelgeuse recorded with the TEXES spectrograph. The
spectra clearly show absorption features of water vapor and OH. We show that a
spectrum based on a spherical, hydrostatic model photosphere with T_eff = 3600
K, an effective temperature often assumed for Betelgeuse, fails to model the
observed lines. Furthermore, we show that published MOLspheres scenarios are
unable to explain our data. However, we are able to model the observed spectrum
reasonably well by adopting a cooler outer photospheric structure corresponding
to T_mod = 3250 K. The success of this model may indicate the observed
mid-infrared lines are formed in cool photospheric surface regions. Given the
uncertainties of the temperature structure and the likely presence of
inhomogeneities, we cannot rule out the possibility that our spectrum could be
mostly photospheric, albeit non-classical. Our data put new, strong constraints
on atmospheric models of Betelgeuse and we conclude that continued
investigation requires consideration of non-classical model photospheres as
well as possible effects of a MOLsphere. We show that the mid-infrared
water-vapor features have great diagnostic value for the environments of K and
M (super-) giant star atmospheres.


title: Observational Constraints on Undulant Cosmologies

abstract:
  In an undulant universe, cosmic expansion is characterized by alternating
periods of acceleration and deceleration. We examine cosmologies in which the
dark-energy equation of state varies periodically with the number of e-foldings
of the scale factor of the universe, and use observations to constrain the
frequency of oscillation. We find a tension between a forceful response to the
cosmic coincidence problem and the standard treatment of structure formation.


title:
Interferometric Visibility and Closure Phase of Microlensing Events with
  Finite Source Size

abstract:
  Interferometers from the ground and space will be able to resolve the two
images in a microlensing event. This will at least partially lift the inherent
degeneracy between physical parameters in microlensing events. To increase the
signal-to-noise ratio, intrinsically bright events with large magnifications
will be preferentially selected as targets. These events may be influenced by
finite source size effects both photometrically and astrometrically. Using
observed finite source size events as examples, we show that the fringe
visibility can be affected by 5% - 10%, and the closure phase by a few degrees:
readily detectable by ground and space interferometers. Such detections will
offer unique information about the lens-source trajectory relative to the
baseline of the interferometers. Combined with photometric finite source size
effects, interferometry offers a way to measure the angular sizes of the source
and the Einstein radius accurately.
  Limb-darkening changes the visibility by a small amount compared with a
source with uniform surface brightness, marginally detectable with ground-based
instruments.
  We discuss the implications of our results for the plans to make
interferometric observations of future microlensing events.


title: Looking for z>7 galaxies with the Gravitational Telescope

abstract:
  We summarize the main results obtained recently by our group on the
identification and study of very high-z galaxies (z>7) using lensing clusters
as natural gravitational telescopes. A description of our pilot survey with
ISAAC/VLT is presented, aimed at the spectroscopic confirmation of z>7
candidate galaxies photometrically selected from deep near-IR, HST and optical
ground-based imaging. The first results issued from this survey are discussed,
in particular the global photometric properties of our high-z candidates, and
the implications for the global star formation rate at very high-z.


title: PulsarSpectrum: simulating gamma-ray pulsars for the GLAST mission

abstract:
  We present here an overview of PulsarSpectrum, a program that simulates the
gamma ray emission from pulsars. This simulator reproduces not only the basic
features of the observed gamma ray pulsars, but it can also simulate more
detailed effects related to pulsar timing. It is a very useful tool to
understand the GLAST capabilities in the pulsar science.


title: Bar instability in cosmological halos

abstract:
  Aims: We want to investigate the growth of bar instability in stellar disks
embedded in a suitable dark matter halo evolving in a fully consistent
cosmological framework.
  Methods: We perform seven cosmological simulations to emphasise the role of
both the disk-to-halo mass ratio and of the Toomre parameter, Q, on the
evolution of the disk.We also compare our fully cosmological cases with
corresponding isolated simulations where the same halo, is extracted from the
cosmological scenario and evolved in physical coordinates.
  Results: A long living bar, lasting about 10 Gyr, appears in all our
simulations. In particular, disks expected to be stable according to classical
criteria, form indeed weak bars. We argue that such a result is due to the
dynamical properties of our cosmological halo which is far from stability and
isotropy, typical of the classical halos used in literature; it is dynamically
active, endowed of substructures and infall.
  Conclusions: At least for mild self-gravitating disks, the study of the bar
instability using isolated isotropic halos, in gravitational equilibrium, can
lead to misleading results. Furthermore, the cosmological framework is needed
for quantitatively investigating such an instability.


title: Elliptical Galaxy Halo Masses from Internal Kinematics

abstract:
  The halo masses of nearby individual elliptical galaxies can be estimated by
using the kinematics of their stars, planetary nebulae, and globular clusters
-- ideally in combination. With currently improving coverage of galaxies of
ordinary luminosities and morphologies, systematic trends may be identified.
Bright, boxy ellipticals show strong signatures of dark matter, while faint,
disky ones typically do not. The former result is problematic for the MOND
theory of gravity, and the latter is a challenge to explain in the LCDM
paradigm of galaxy formation.


title:
Axisymmetric simulations of magneto--rotational core collapse: dynamics
  and gravitational wave signal

abstract:
  We have performed a comprehensive parameter study of the collapse of
rotating, strongly magnetized stellar cores in axisymmetry to determine their
gravitational wave signature based on the Einstein quadrupole formula. We use a
Newtonian explicit magnetohydrodynamic Eulerian code based on the relaxing-TVD
method for the solution of the ideal MHD equations, and apply the
constraint-transport method to guarantee a divergence--free evolution of the
magnetic field. We neglect effects due to neutrino transport and employ a
simplified equation of state. The pre--collapse initial models are polytropes
in rotational equilibrium with a prescribed degree of differential rotation and
rotational energy (~ 1 % of the gravitational energy). The initial magnetic
fields are purely poloidal the field strength ranging from 10^10 G to 10^13 G.
The evolution of the core, whose collapse is initiated by reducing the gas
pressure by a prescribed amount, is followed until a few ten milliseconds past
core bounce.
  The initial magnetic fields are amplified mainly by the differential rotation
of the core giving rise to a strong toroidal field component. The poloidal
field component grows by compression during collapse, but does not change
significantly after core bounce if (abbreviated)


title:
A deep XMM-Newton observation of the ultraluminous X-ray source HoII X-1
  : the case against a 1000 solar mass black hole

abstract:
  We present results from a 112 ks long look by XMM-Newton at the ultraluminous
X-ray source (ULX) Holmberg II X-1, long thought to be the one of best
candidates for the missing class of intermediate mass black holes (IMBHs). Our
data comprises the first high quality XMM-Newton/RGS spectrum of an ULX, and an
XMM-Newton/EPIC spectrum with unprecedented signal-to-noise. A detailed timing
analysis shows that any variability on time-scales of minutes to hours is very
weak (< few per cent fractional rms), though larger amplitude variations on
much shorter time-scales could be hidden by photon counting statistics. This
result suggests that if Ho II X-1 harbours an IMBH, then we are observing this
source in a highly unusual and atypical state when compared with the known
variability behaviour of other accreting systems of large mass. Moreover unlike
Galactic X-ray binaries, our spectral analysis indicates the possible presence
of an optically-thick low temperature corona. Taken together our timing and
spectral analysis suggests that the compact companion is most-likely a high
luminosity analogue of black hole binary systems similar to GRS 1915+105, the
Galactic microquasar, harbouring a compact object of mass no greater than 100
solar masses.


title:
Faint InfraRed Extragalactic Survey: Data and Source Catalogue of the
  MS1054-03 field

abstract:
  We present deep near-infrared Js, H, and Ks band imaging of a field around
MS1054-03, a massive cluster at z=0.83. The observations were carried out with
ISAAC at the ESO VLT as part of the Faint InfraRed Extragalactic Survey
(FIRES). The total integration time amounts to 25.9h in Js, 24.4h in H, and
26.5h in Ks, divided nearly equally between four pointings covering 5.5'x5.3'.
The 3-sigma total limiting AB magnitudes for point sources from the shallowest
to deepest pointing are Js=26.0-26.2, H=25.5-25.8, and Ks=25.3-25.7. The
effective spatial resolution of the coadded images has FWHM=0.48", 0.46", and
0.52" in Js, H, and Ks. We complemented the ISAAC data with deep optical
imaging using existing HST WFPC2 mosaics in the F606W and F814W filters and new
U, B and V band data from VLT FORS1. We constructed a Ks-band limited
multicolour source catalogue to Ks(total,AB)=25 (about 5-sigma for point
sources). The catalogue contains 1858 objects, of which 1663 have eight-band
photometry. We describe the observations, data reduction, source detection and
photometric measurements method. We present the number counts, colour
distributions, and photometric redshifts z_ph of the catalogue sources. We find
that our counts at the faint end 22<Ks(AB)<25, with slope dlog(N)/dm=0.20, lie
at the flatter end of published counts in other deep fields and are consistent
with those we derived in the HDF-South, the other FIRES field. Spectroscopic
redshifts z_sp are available for about 330 sources in the MS1054-03 field;
comparison between the z_ph and z_sp shows very good agreement, with
<|z_sp-z_ph|/(1+z_sp)>=0.078. The MS1054-03 field observations complement our
HDF-South data set with nearly five times larger area at about 0.7 brighter
magnitudes. [ABRIDGED]