title: Nonlinear Hydromagnetic Wave Support of a Stratified Molecular Cloud

abstract:
  We perform numerical simulations of nonlinear MHD waves in a gravitationally
stratified molecular cloud that is bounded by a hot and tenuous external
medium. We study the relation between the strength of the turbulence and
various global properties of a molecular cloud, within a 1.5-dimensional
approximation. Under the influence of a driving source of Alfvenic
disturbances, the cloud is lifted up by the pressure of MHD waves and reaches a
steady-state characterized by oscillations about a new time-averaged
equilibrium state. The nonlinear effect results in the generation of
longitudinal motions and many shock waves; however, the wave kinetic energy
remains predominantly in transverse, rather than longitudinal, motions. There
is an approximate equipartition of energy between the transverse velocity and
fluctuating magnetic field (aspredicted by small-amplitude theory) in the
region of the stratified cloud which contains most of the mass; however, this
relation breaks down in the outer regions, particularly near the cloud surface,
where the motions have a standing-wave character. This means that the
Chandrasekhar-Fermi formula applied to molecular clouds must be significantly
modified in such regions. Models of an ensemble of clouds show that, for
various strengths of the input energy, the velocity dispersion in the cloud
$\sigma \propto Z^{0.5}$, where $Z$ is a characteristic size of the
cloud.Furthermore, $\sigma$ is always comparable to the mean Alfven velocity of
the cloud, consistent with observational results.


title:
On the Assembly History of Early-Type Galaxies in the Hubble Deep Field
  North

abstract:
  We present deep Keck spectroscopy for a sample of I<22.5 field early-type
galaxies selected morphologically in the redshift range 0.56<z<1.02 in the
HDF-N. Using velocity dispersions determined from the Keck spectra in
conjunction with structural parameters measured from the deep WFPC2 images we
study the evolution of the M/L_B ratio and the fundamental plane (FP) with
redshift. For the majority of galaxies the trends observed are very similar to
those determined earlier for rich clusters. The systematic offset between HDF-N
galaxies and cluster galaxies is d(ln M/L_B) = -0.14 +- 0.13, corresponding to
an age difference of only 16 +- 15 % at <z>=0.88. However, we find enhanced H
delta absorption of equivalent width 4.0 Angstrom in the mean spectrum of the
ten galaxies, indicating the presence of young stars. We infer that the
galaxies have composite stellar populations, consisting of a low mass young
component in addition to a dominating old component. As the bulk of the stellar
mass must have formed at z >~ 2 our results argue against formation scenarios
involving major mergers of gas-rich disk systems at 1<z<1.5, and we conclude
that z~1 early-type galaxies were either assembled at higher redshift or in
mergers involving little gas. The ubiquitous enhanced Balmer lines and the
presence of tidal features in two of the galaxies lend some support to the
latter hypothesis. The main uncertainty in the analysis is the small sample;
larger samples are needed to study the interplay between the evolution of
stellar populations and morphology in detail.


title: The Distance to Pleiades

abstract:
  The distance to Pleiades remains controversial. There is a simple way to
resolve the dispute definitely by measuring the distance to one of its
brightest members, Atlas, which is astrometric and spectroscopic binary.


title: Gravitational Collapse of Filamentary Magnetized Molecular Clouds

abstract:
  We develop models for the self-similar collapse of magnetized isothermal
cylinders. We find solutions for the case of a fluid with a constant toroidal
flux-to-mass ratio (Gamma_phi=constant) and the case of a fluid with a constant
gas to magnetic pressure ratio (beta=constant). In both cases, we find that a
low magnetization results in density profiles that behave as rho ~ r^{-4} at
large radii, and at high magnetization we find density profiles that behave as
rho ~ r^{-2}. This density behaviour is the same as for hydrostatic filamentary
structures, suggesting that density measurements alone cannot distinguish
between hydrostatic and collapsing filaments--velocity measurements are
required. Our solutions show that the self-similar radial velocity behaves as
v_r ~ r during the collapse phase, and that unlike collapsing self-similar
spheres, there is no subsequent accretion (i.e. expansion-wave) phase. We also
examine the fragmentation properties of these cylinders, and find that in both
cases, the presence of a toroidal field acts to strengthen the cylinder against
fragmentation. Finally, the collapse time scales in our models are shorter than
the fragmentation time scales. Thus, we anticipate that highly collapsed
filaments can form before they are broken into pieces by gravitational
fragmentation.


title:
Towards a Solution to the Early Faint Sun Paradox: A Lower Cosmic Ray
  Flux from a Stronger Solar Wind

abstract:
  Standard solar models predict a solar luminosity that gradually increased by
about 30% over the past 4.5 billion years. Under the faint sun, Earth should
have been frozen solid for most of its existence. Yet, running water is
observed to have been present since very early in Earth's history. This enigma
is known as the faint sun paradox. We show here that it can be partially
resolved once we consider the cooling effect that cosmic rays are suspected to
have on the global climate and that the younger sun must have had a stronger
solar wind, such that it was more effective at stopping cosmic rays from
reaching Earth. The paradox can then be completely resolved with the further
contribution of modest greenhouse gas warming. When we add the cosmic ray flux
modulation by a variable star formation rate in the Milky Way, we recover the
long term glacial activity on Earth. As to the future, we find that the average
global temperature will increase by typically 10K in the coming 2 Gyr.


title: Current models for the evolution of AGB stars

abstract:
  While the basic properties of AGB stellar evolution are well established,
comprehensive observational studies of late phases of intermediate mass stars
continue to generate puzzles for current stellar models. Here, I review current
techniques to model AGB stars, and I discuss important aspects of current
research of AGB (and post-AGB) stellar evolution with a particular focus on how
these interrelate.


title:
Spectral Energy Distributions of Circumstellar Debris Disks I. Analytic
  Disk Density Distributions

abstract:
  We present results of a study aimed at deriving fundamental properties of
circumstellar debris disks from observed infrared to submillimeter spectral
energy distributions. This investigation is motivated by increasing
telescope/detector sensitivity, in particular the expected availability of the
Space Infrared Telescope Facility (SIRTF) followed by the Stratospheric
Observatory for Infrared Astronomy (SOFIA), which will enable detailed studies
with large source samples of late stage circumstellar disk and planetary system
evolution. We base our study on an analytic model of the disk density
distribution and geometry, taking into account existing constraints from
observations and results of theoretical investigations of debris disks. We also
outline the effects of the most profound characteristics of circumstellar dust
including the grain size distribution and dust chemical composition.


title: Are there brown dwarfs in globular clusters?

abstract:
  We present an analytical method for constraining the substellar initial mass
function in globular clusters, based on the observed frequency of transit
events. Globular clusters typically have very high stellar densities where
close encounters are relatively common, and thus tidal capture can occur to
form close binary systems. Encounters between main sequence stars and
lower-mass objects can result in tidal capture if the mass ratio is > 0.01. If
brown dwarfs exist in significant numbers, they too will be found in close
binaries, and some fraction of their number should be revealed as they transit
their stellar companions. We calculate the rate of tidal capture of brown
dwarfs in both segregated and unsegregated clusters, and find that the tidal
capture is more likely to occur over an initial relaxation time before
equipartition occurs. The lack of any such transits in recent HST monitoring of
47 Tuc implies an upper limit on the frequency of brown dwarfs (< 15 % relative
to stars) which is significantly below that measured in the galactic field and
young clusters.


title:
General Relativistic Numerical Simulation on Coalescing Binary Neutron
  Stars and Gauge-Invariant Gravitational Wave Extraction

abstract:
  We are developing 3 dimensional simulation codes for coalescing binary
neutron stars. A code using the maximal slicing condition is obtained. To
evaluate the gravitational radiation, we implemented a gauge-invariant wave
extraction and compared the wave forms with the metric tensors at the wave
zone. The energy spectrum of the waves was also evaluated to investigate the
possibility that the excitation of the quasi-normal modes of the black hole,
which may be formed after the merger of two stars, can be observed.


title: Surface photon emissivity of bare strange stars

abstract:
  We consider the bremsstrahlung surface photon emissivity of strange quark
stars, by sistematically taking into account the effects of the multiple
scatterings of the highly relativistic quarks in a dense medium (the
Landau-Pomeranchuk-Migdal effect). Due to interference between amplitudes of
nearby interactions, the bremsstrahlung emissivity from strange star surface is
suppressed for frequencies smaller than a critical frequency. The range of the
suppressed frequencies is a function of the quark matter density at the star's
surface and of the QCD coupling constant. For temperatures much smaller than
the Fermi energy of the quarks the bremsstrahlung spectrum has the same
temperature dependence as the equilibrium black body radiation. Multiple
collisions could reduce the intensity of the bremsstrahlung radiation by an
order of magnitude. The effect of the thin electron layer at the surface of the
quark star on the bremsstrahlung spectrum is also analyzed in detail. It is
shown that absorption in the semi-degenerate electron gas can also
significantly reduce the intensity of the quark-quark bremsstrahlung radiation
and, consequently, the surface emissivity. Hence the combined effects of
multiple collisions and absorption in the electron layer could make the soft
photon surface radiation of quark stars six orders of magnitude smaller than
the equilibrium black body radiation.


title:
Further evidence for a variable fine-structure constant from Keck/HIRES
  QSO absorption spectra

abstract:
  [Abridged] We previously presented evidence for a varying fine-structure
constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we
present a detailed many-multiplet analysis of a third Keck/HIRES sample
containing 78 absorption systems. We also re-analyse the previous samples,
providing a total of 128 absorption systems over the redshift range
0.2<z_abs<3.7. All three samples separately yield consistent, significant
values of da/a. The analyses of low- and high-z systems rely on different
ions/transitions with very different dependencies on alpha, yet they also give
consistent results. We identify additional random errors in 22 high-z systems
characterized by transitions with a large dynamic range in apparent optical
depth. Increasing the statistical errors on da/a for these systems gives our
fiducial result, a weighted mean da/a=(-0.543+/-0.116)x10^-5, representing
4.7-sigma evidence for a smaller weighted mean alpha in the absorption clouds.
Assuming that da/a=0 at z_abs=0, the data marginally prefer a linear increase
in alpha with time: dota/a=(6.40+/-1.35)x10^-16 yr^-1. The two-point
correlation function for alpha is consistent with zero over 0.2-13 Gpc comoving
scales and the angular distribution of da/a shows no significant dipolar
anisotropy. We therefore have no evidence for spatial variations in da/a. We
extend our previous searches for possible systematic errors, identifying
atmospheric dispersion and isotopic structure effects as potentially the most
significant. However, overall, known systematic errors do not explain the
results. Future many-multiplet analyses of QSO spectra from different
telescopes and spectrographs will provide a now crucial check on our Keck/HIRES
results.


title:
First Results from MASIV: The Micro-Arcsecond Scintillation-Induced
  Variability Survey

abstract:
  We are undertaking a large-scale, Micro-Arcsecond Scintillation-Induced
Variability (MASIV) survey of the northern sky, Dec > 0 deg, at 4.9 GHz with
the VLA. Our objective is to construct a sample of 100 to 150 scintillating
extragalactic sources with which to examine both the microarcsecond structure
and the parent populations of these sources, and to probe the turbulent
interstellar medium responsible for the scintillation. We report on our first
epoch of observations which revealed variability on timescales ranging from
hours to days in 85 of 710 compact flat-spectrum sources. The number of highly
variable sources, those with RMS flux density variations greater than 4% of the
mean, increases with decreasing source flux density but rapid, large amplitude
variables such as J1819+3845 are very rare. When compared with a model for the
scintillation due to irregularities in a 500 pc thick electron layer, our
preliminary results indicate maximum brightness temperatures ~10E+12 K, similar
to those obtained from VLBI surveys even though interstellar scintillation is
not subject to the same angular resolution limit.


title: The Electron Spectrum in 3C279 and the Observed Emission Spectrum

abstract:
  The emission mechanisms of the blazar 3C 279 are studied by solving the
kinetic equations of electrons and photons in a relativistically moving blob.
The gamma-ray spectral energy distribution (SED) is fitted by inverse Compton
scattering of external photons. The bulk Lorentz factor of the emitting blob is
found to be 25, and the magnetic field is found to be 0.3 G. GeV gamma-rays are
well explained by inefficiently cooled electrons because of the Klein-Nishina
effects. The electron spectrum is not a broken power law with a steeper
spectrum above a break energy, which is often used to fit the observed SED. The
kinetic energy density of the nonthermal electrons dominates the magnetic
energy density; this result is qualitatively the same as that for TeV blazars
such as Mrk 421 and Mrk 501. The gamma-ray luminosity of 3C 279 is often
observed to increase rapidly. We show that one of the better sampled gamma-ray
flares can be explain by the internal shock model.


title: Supernova Cosmology and the Fine Structure Constant

abstract:
  We study the dependence of the peak luminosity of Type Ia supernovae on the
fine structure constant $\alpha$. We find that decreasing (increasing) $\alpha$
enhances (reduces) the luminosity. Future experiments like SNAP could determine
the variation of $\alpha$ to a precision of $10^{-2}$.


title: Universality in the distribution of caustics in the expanding Universe

abstract:
  We numerically investigate the long--time evolution of density perturbations
after the first appearance of caustics in an expanding cosmological model with
one--dimensional `single--wave' initial conditions. Focussing on the
time--intervals of caustic appearances and the spatial distribution of caustics
at subsequent times, we find that the time--intervals of caustic appearances
approach a constant, i.e., their time--subsequent ratio converges to 1; it is
also found that the spatial distribution of caustics at a given time features
some universality rules, e.g., the ratio between the position of the nearest
caustic from the center and that of the second nearest caustic from the center
approaches a constant. Furthermore we find some rules for the mass distribution
for each caustic. Using these universality constants we are in the position to
predict the spatial distribution of caustics at an arbitrary time in order to
give an estimate for the power spectral index in the fully--developed
non--dissipative turbulent (`virialized') regime.


title:
Diagnostic Signatures of Radio and HXR Emission on Particle Acceleration
  Processes in the Coma Cluster

abstract:
  We investigate theoretical models for the radio halo and hard X-ray (HXR)
excess in the Coma galaxy cluster. Time-independent and time-dependent
re-acceleration models for relativistic electrons have been carried out to
study the formation of the radio halo and HXR excess. In these models, the
relativistic electrons are injected by merger shocks and re-accelerated by
ensuing violent turbulence. The effects of different Mach numbers of the merger
shocks on the radio and HXR excess emission are also investigated. We adopt 6
$\mu$G as the central magnetic field and reproduce the observed radio spectra
via the synchrotron emission. We also obtain a central "plateau" in the radio
spectral-index distribution, which have been observed in radio emission
distribution. Our models can also produce the observed HXR excess emission via
the inverse Compton scattering of the cosmic microwave background photons. We
find that only the merger shocks with the Mach numbers around 1.6--2 can
produce results in agreement with both the radio and HXR emission in the Coma
cluster.


title: An accretion disk model for periodic timing variations of pulsars

abstract:
  The long-term, highly periodic and correlated variations in both the pulse
shape and the rate of slow-down of two isolated pulsars (PSRs) PSR B1828-11 and
PSR B1642-03 were discovered recently. This phenomenon may provide evidence for
"free precession" as suggested in the literature. Some authors presented
various kinds of models to explain this phenomenon within the framework of free
precession. Here we present an accretion disk model for this precession
phenomenon instead. Under reasonable parameters, the observed phenomenon can be
explained by an isolated pulsar with a fossil disk. This may link radio pulsars
and anomalous X-ray pulsars (AXPs) and present an indirect evidence for the
existence of the fossil disk in nature.


title: Dark matter in galaxies and growth of giant black holes

abstract:
  The connection between dark matter and giant black holes in the galactic
nuclei is investigated. The joint evolution of dark and luminous matter in
averaged self-consistent gravitational potential is considered. It is shown
that the distribution of dark matter remains spherically symmetric even in
presence of essential asymmetry of luminous matter in the galaxy.
  The kinetic equation describing evolution of dark matter particles
distribution function which takes into account their dynamics in gravitational
potential and scattering on stars is derived. It is shown that significant flux
of dark matter on a seed black hole in the center of galaxy should appear. The
growth law of seed black hole due to absorption of dark matter is derived. It
appears that during the lifetime of galaxy the seed black hole should grow
significantly, up to observed value. Brief analysis of observational data shows
that the presented theory is in reasonable agreement with observations.


title:
The effects of inclination, gravity darkening and differential rotation
  on absorption profiles of fast rotators

abstract:
  Mechanisms influencing absorption line profiles of fast rotating stars can be
sorted into two groups; (i) intrinsic variations sensitive to temperature and
pressure, and (ii) global effects common to all spectral lines. I present a
detailed study on the latter effects focusing on gravity darkening and
inclination for various rotational velocities and spectral types. It is shown
that the line shapes of rapidly and rigidly rotating stars mainly depend on the
equatorial velocity $v_{\rm e}$, not on the projected rotational velocity $v
\sin{i}$ which determines the lines width. The influence of gravity darkening
and spectral type on the line profiles is shown. The results demonstrate the
possibility of determining the inclination angle $i$ of single fast rotators,
and they show that constraints on gravity darkening can be drawn for stellar
samples. While significant line profile deformation occurs in stars rotating as
fast as $v_{\rm e} \ga 200$ km s$^{-1}$, for slower rotators profile distortion
are marginal. In these cases spectral signatures induced by, e.g., differential
rotation are not affected by gravity darkening and the methods applicable to
slow rotators can be applied to these faster rotators, too.


title:
IRAS 08544-4431 : a new post-AGB star in a binary system surrounded by a
  dusty disc

abstract:
  We present an analysis of our extensive data-set on IRAS 08544-4431. It is
the first object we discuss of our newly defined sample of stars, selected for
their position in the 'RV Tauri' box in the IRAS [12]-[25], [25]-[60] two-color
diagram. Moreover, our selection criteria included an observed excess in the
L-band, indicative of a dusty disc. The SED of IRAS 08544-4431 shows a broad IR
excess starting already at H. Our optical photometric data reveal some evidence
for deep and] shallow minima in the light curve and a pulsation time-scale of
around 100 days with a small amplitude (peak-to-peak amplitude in V = 0.17
mag). Our CORALIE radial velocity measurements show that IRAS 08544-4431 is a
binary system with a period of 499 +/- 3 days and a mass function of 0.02
M_sun. Moreover, IRAS 08544-4431 is detected in both the CO (2-1) and (1-0)
mm-wave emission lines. The triangular shape of the weak CO profile confirms
that part of the circumstellar material is not freely expanding but resides
probably in a dusty circumbinary disc. Our chemical abundance analysis of a
high resolution spectrum of high S/N reveals that a depletion process has
modified the photospheric abundances to a moderate extent ([Zn/Fe]=+0.4). All
these findings confirm that the F-type IRAS 08544-4431 is another good example
of a binary Post-AGB star surrounded by a dusty disc. The H-alpha P-Cygni
profile shows ongoing mass-loss with a very high outflow velocity, the origin
of which is not understood. The strength and velocity of the H-alpha-absorption
are modulated with the orbital motion; the maxima of both quantities (+/- 400
km/s, 5 Angstrom, respectively) occur at superior conjunction.


title: The onset of the non-linear regime in unified dark matter models

abstract:
  We discuss the onset of the non-linear regime in the context of unified dark
matter models involving a generalised Chaplygin gas. We show that the
transition from dark matter-like to dark energy-like behaviour will never be
smooth. In some regions of space the transition will never take place while in
others it may happen sooner or later than naively expected. As a result the
linear theory used in previous studies may break down late in the matter
dominated era even on large cosmological scales. We study the importance of
this effect showing that its magnitude depends on the exact form of the
equation of state in the low density regime. We expect that our results will be
relevant for other unified dark matter scenarios particularly those where the
quartessence candidate is a perfect fluid.


title: Chemical evolution of the intra-cluster medium

abstract:
  The high metallicity of the intra-cluster medium (ICM) is generally
interpreted on the base of the galactic wind scenario for elliptical galaxies.
In this framework, we develop a toy-model to follow the chemical evolution of
the ICM, formulated in analogy to chemical models for individual galaxies. The
model computes the galaxy formation history (GFH) of cluster galaxies,
connecting the final luminosity function (LF) to the corresponding metal
enrichment history of the ICM. The observed LF can be reproduced with a smooth,
Madau-plot like GFH peaking at z~ 1-2, plus a "burst" of formation of dwarf
galaxies at high redshift. The model is used to test the response of the
predicted metal content and abundance evolution of the ICM to varying input
galactic models. The chemical enrichment is computed from "galactic yields"
based on models of elliptical galaxies with a variable initial mass function
(IMF), favouring the formation of massive stars at high redshift and/or in more
massive galaxies. For a given final galactic luminosity, these model
ellipticals eject into the ICM a larger quantity of gas and of metals than do
standard models based on the Salpeter IMF. However, a scenario in which the IMF
varies with redshift as a consequence of the effect of the the cosmic
background temperature on the Jeans mass scale, appears to be too mild to
account for the observed metal production in clusters. The high
iron-mass-to-luminosity-ratio of the ICM can be reproduced only by assuming a
more dramatic variation of the typical stellar mass, in line with other recent
findings. The mass in the wind-ejected gas is predicted to exceed the mass in
galaxies by a factor of 1.5-2 and to constitute roughly half of the
intra-cluster gas.


title:
Discovery of a young massive stellar cluster associated with IRAS source
  16177-5018

abstract:
  We report the discovery of a young massive stellar cluster embedded in an
extended HII region, invisible at optical wavelengths where the extinction is
$A_V \approx 28$ magnitudes, associated with the IRAS source 16177-5018. $J, H$
and nb$K$ imaging photometry combined with the $K_S$ 2MASS data show the
presence of sources with infrared excess emission at 2.2 $\mu$m, concentrated
in an area of about one square parsec around a massive young stellar object
identified as the IRAS source. This object has a near-mid infrared spectral
index betweem 2.2 and 25 $\mu$m $\alpha({\rm IR}) = d {\rm log}(\lambda
F_\lambda)/d {\rm log} \lambda $ =4.78, characteristic of compact H II regions,
with bolometric luminosity, inferred from the integrated near to far-infrared
flux density of $2.8 \times 10^5 L_\odot$, which corresponds to a ZAMS star of
about $42 M_\odot$. From the color-magnitude diagram we were able to classify
the majority of the cluster members as reddened massive stars earlier than
spectral type B5.


title:
Radio Variability of the Sagittarius $ {\rm A^*}$ due to an Orbiting
  Star

abstract:
  Recently, unprecedentedly accurate data on the orbital motion of stars in the
vicinity of the Sagittarius $ {\rm A^*}$ have been available. Such information
can be used not only to constrain the mass of the supermassive black hole
(SMBH) in the Galactic center but also to study the source of the radio
emission. Two major competing explanations of the radio spectrum of the
Sagittarius $ {\rm A^*}$ are based on two different models, that is, hot
accretion disk and jet. Hence, independent observational constraints are
required to resolve related issues. We explore the possibility of using the
observational data of the star S2, currently closest to the Galactic center, to
distinguish physical models for the radio emission of the Sagittarius $ {\rm
A^*}$, by applying the stellar cooling model to the Sagittarius $ {\rm A^*}$
with the orbital parameters derived from the observation. The relative
difference in the electron temperature due to the stellar cooling from the star
S2 at the pericenter is a few parts of a thousand and the consequent relative
radio luminosity difference is order of $10^{-4}$. Therefore, one could
possibly expect to observe the radio flux variation with a periodic or
quasi-periodic modulation in the frequency range at $\nu \la {\rm 100 MHz}$ if
the radiatively inefficient hot accretion flows are indeed responsible for the
radio emission, contrary to the case of a jet. According to our findings, even
though no periodic radio flux variations have been reported up to date a
radiatively inefficient hot accretion disk model cannot be conclusively ruled
out.


title:
The detection of stellar velocity dispersion drops in the central
  regions of five isolated Seyfert spirals

abstract:
  We analyze the kinematics of the central regions of five isolated Seyfert
spiral galaxies from the DEGAS sample (four with new data presented in this
paper, IC184, UGC3223, NGC2639, NGC6814, and NGC6951 from our previous data),
by using long slit spectroscopy in the CaII triplet range (at ~ 8600 A)
obtained with a 4m-class telescope. A drop of the velocity dispersions in the
innermost 1-3 arcsec is observed in four of them, and hinted in the remaining
galaxy (NGC6814). The available HST images for our sample together with another
nine galaxies with reported velocity dispersion drops, are also used to
investigate the presence of morphological inner structures at the scales of the
kinematical drops. Evidence for disk-like shapes is found in 12 out of the 14
cases. The only exceptions are NGC6814 and NGC6951. Existing N-body simulations
including stars, gas and star formation predict that such a drop is most
probably due to a young stellar population born from dynamically cold gas
accreted in a circumnuclear disk formed during an episode of central gas
accretion driven by a bar. The equivalent widths of the Calcium triplet lines
for our 5 galaxies have been measured. Even if the profiles could be formally
consistent with constant EW(CaT) values, they seem to indicate the presence of
a local maximum in the regions corresponding spatially to the drops; if
confirmed, this would imply the presence of a different stellar population,
whose properties could help constraining the models.


title: Conserved cosmological perturbations

abstract:
  A conserved cosmological perturbation is associated with each quantity whose
local evolution is determined entirely by the local expansion of the Universe.
It may be defined as the appropriately normalised perturbation of the quantity,
defined using a slicing of spacetime such that the expansion between slices is
spatially homogeneous. To first order, on super-horizon scales, the slicing
with unperturbed intrinsic curvature has this property. A general construction
is given for conserved quantities, yielding the curvature perturbation $\zeta$
as well as more recently-considered conserved perturbations. The construction
may be extended to higher orders in perturbation theory and even into the
non-perturbative regime.


title:
Galaxy and hot gas distributions in the z=0.52 galaxy cluster RBS380
  from CHANDRA and NTT observations

abstract:
  We present CHANDRA X-ray and NTT optical observations of the distant z=0.52
galaxy cluster RBS380 -- the most distant cluster of the ROSAT Bright Source
(RBS) catalogue. We find diffuse, non-spherically symmetric X-ray emission with
a X-ray luminosity of L_X(0.3-10 keV)=1.6 10^(44) erg/s, which is lower than
expected from the RBS. The reason is a bright AGN in the centre of the cluster
contributing considerably to the X-ray flux. This AGN could not be resolved
with ROSAT. In optical wavelength we identify several galaxies belonging to the
cluster. The galaxy density is at least 2 times higher than expected for such a
X-ray faint cluster, which is another confirmation of the weak correlation
between X-ray luminosity and optical richness. The example of the source
confusion in this cluster shows how important high-resolution X-ray imaging is
for cosmological research.


title: The CDM isocurvature perturbation in the curvaton scenario

abstract:
  We discuss the residual isocurvature perturbations, fully-correlated with the
curvature perturbation, that are automatic in the curvaton scenario if curvaton
decay is sufficiently late. We contrast these residual isocurvature
perturbations with the generally un-correlated `intrinsic' isocurvature
perturbation generated by an additional field such as the axion. We present a
general formula for the residual isocurvature perturbations, referring only to
the generation of the relevant quantity (Cold Dark Matter, baryon number or
lepton number) in an unperturbed universe. Specific formulas for the residual
isocurvature CDM perturbation are given, for most of the commonly-considered
CDM candidates.


title:
On the Structure and Kinematics of Nebulae around LBVs and LBV
  Candidates in the LMC

abstract:
  We present a detailed analysis of the morphology and kinematics of nebulae
around LBVs and LBV candidates in the Large Magellanic Cloud. HST images and
high-resolution Echelle Spectra were used to determine the size, shape,
brightness, and expansion velocities of the LBV nebulae around R127, R143, and
S61. For S Dor, R71, R99, and R84 we discuss the possible presence of nebular
emission, and derive upper limits for the size and lower limits on the
expansion velocities of possible nebulae. Including earlier results for the LBV
candidates S119 and SK-69 279 we find that in general the nebulae around LBVs
in the LMC are comparable in size to those found in the Milky Way. The
expansion velocities of the LMC nebulae, however, are significantly lower--by
about a factor of 3 to 4--than those of galactic nebulae of comparable size.
Galactic and LMC nebulae show about the same diversity of morphologies, but
only in the LMC do we find nebulae with outflow. Bipolarity--at least to some
degree--is found in nebulae in the LMC as well as in the Milky Way, and
manifests a much more general feature among LBV nebulae than previously known.


title: M51 revisited: a genetic algorithm approach of its interaction history

abstract:
  Detailed models of observed interacting galaxies suffer from the extended
parameter space. Here, we present results from our code MINGA which couples an
evolutionary optimization strategy (a genetic algorithm) with a fast N-body
method. MINGA allows for an automatic search of the optimal region(s) in
parameter space within a few hours to a few days of CPU time on a modern PC by
investigating of the order of 10^5 models. We demonstrate its applicability by
modelling the HI intensity and velocity maps of the interacting system M51 and
NGC 5195. We get a good fit for the HI intensity map and we can reproduce the
counter-rotation feature of the HI arm. Our result corroborates the results of
Salo & Laurikainen (2000) who favour a model with multiple passages through
M51's disk.


title:
The evolution of a hot subdwarf: observations of the pulsating subdwarf
  B star Feige~48

abstract:
  Since pulsating subdwarf B (sdBV or EC14026) stars were first discovered
(Kilkenny et al, 1997), observational efforts have tried to realize their
potential for constraining the interior physics of extreme horizontal branch
(EHB) stars. Difficulties encountered along the way include uncertain mode
identifications and a lack of stable pulsation mode properties. Here we report
on Feige~48, an sdBV star for which follow-up observations have been obtained
spanning more than four years, which shows some stable pulsation modes.
  We resolve the temporal spectrum into five stable pulsation periods in the
range 340 to 380 seconds with amplitudes less then 1%, and two additional
periods that appear in one dataset each. The three largest amplitude
periodicities are nearly equally spaced, and we explore the consequences of
identifying them as a rotationally split $\ell=1$ triplet by consulting with a
representative stellar model.
  The general stability of the pulsation amplitudes and phases allows us to use
the pulsation phases to constrain the timescale of evolution for this sdBV
star. Additionally, we are able to place interesting limits on any stellar or
planetary companion to Feige~48.


title: Recent Results from the MAXIMA Experiment

abstract:
  MAXIMA is a balloon-borne platform for measuring the anisotropy of the Cosmic
Microwave Background (CMB). It has measured the CMB power spectrum with a
ten-arcminute FWHM beam, corresponding to a detection of the power spectrum out
to spherical harmonic multipole l~1000. The spectrum is consistent with a flat
Universe with a nearly scale-invariant initial spectrum of adiabatic density
fluctuations. Moreover, the MAXIMA data are free from any notable non-Gaussian
contamination and from foreground dust emission. In the same region, the WMAP
experiment observes the same structure as that observed by MAXIMA, as evinced
by analysis of both maps and power spectra. The next step in the evolution of
the MAXIMA program is MAXIPOL, which will observe the polarization of the CMB
with comparable resolution and high sensitivity over a small patch of the sky.


title:
The evolution of galaxy clustering since z=1 from the Calar Alto Deep
  Imaging Survey

abstract:
  We present results from an investigation of the clustering evolution of field
galaxies between a redshift of z~1 and the present epoch. The current analysis
relies on a sample of ~3600 galaxies from the Calar Alto Deep Imaging
  Survey (CADIS). The redshift distribution extends to z~1.1, with formal
errors of sigma_z~0.02. Thus the amplitude of the three-dimensional correlation
function can be estimated by means of the projected correlation function
w(r_p). We developed a new method to overcome the influence of redshift errors
on w(r_p). We parametrise the evolution of the clustering strength with
redshift by a parameter q, the values of which give directly the deviation of
the evolution from the global Hubble flow. From a subsample of bright galaxies
we find q=-2.28+-0.31 for Omega_m=0.3, Omega_Lambda=0.7, that is a significant
growth of the clustering strength between z=1 and the present epoch. From
linear theory of dark matter clustering growth one would only expect q=-2.
Moreover, we establish that the measured clustering strength depends on galaxy
type: galaxies with early type SEDs (Hubble type: E0 to Sbc) are more strongly
clustered at redshifts z>0.2 than later types. The evolution of the amplitude
of the two-point correlation function for these ``old'' galaxies is much slower
(q=-0.85+-0.82 for Omega_m=0.3, Omega_Lambda=0.7).


title: CMB Likelihood Functions for Beginners and Experts

abstract:
  Although the broad outlines of the appropriate pipeline for cosmological
likelihood analysis with CMB data has been known for several years, only
recently have we had to contend with the full, large-scale, computationally
challenging problem involving both highly-correlated noise and extremely large
datasets ($N > 1000$). In this talk we concentrate on the beginning and end of
this process. First, we discuss estimating the noise covariance from the data
itself in a rigorous and unbiased way; this is essentially an iterated
minimum-variance mapmaking approach. We also discuss the unbiased determination
of cosmological parameters from estimates of the power spectrum or experimental
bandpowers.


title: Observational Constraints on Chaplygin Quartessence: Background Results

abstract:
  We derive the constraints set by several experiments on the quartessence
Chaplygin model (QCM). In this scenario, a single fluid component drives the
Universe from a nonrelativistic matter-dominated phase to an accelerated
expansion phase behaving, first, like dark matter and in a more recent epoch
like dark energy. We consider current data from SNIa experiments, statistics of
gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in
galaxy clusters. We investigate the constraints from this data set on flat
Chaplygin quartessence cosmologies. The observables considered here are
dependent essentially on the background geometry, and not on the specific form
of the QCM fluctuations. We obtain the confidence region on the two parameters
of the model from a combined analysis of all the above tests. We find that the
best-fit occurs close to the $\Lambda$CDM limit ($\alpha=0$). The standard
Chaplygin quartessence ($\alpha=1$) is also allowed by the data, but only at
the $\sim2\sigma$ level.


title: The Luminosity Function of Cluster Galaxies. III

abstract:
  We investigated the optical properties of 7 clusters of galaxies observed in
three colors over the range of absolute magnitudes -24 < M < -12. Our aim is to
estimate the Luminosity Function and the total cluster luminosity of our sample
in order to have information about the formation and the evolution of galaxies
in clusters. In this paper, we present the main points of our analysis and give
the formal parameters obtained by fitting the data using the maximum likelihood
algorithm. We find consistency between our results and other works in
literature confirming the bimodal nature of the luminosity function of cluster
galaxies. More important, we find that the relation L_opt/ L_X versus L_X is
color dependent: Low X ray Luminosity clusters have a bluer galaxy population.


title: Evolution of primordial perturbations and a fluctuating decay rate

abstract:
  We present a gauge invariant formalism to study the evolution of curvature
perturbations during decay of the inflaton or some other field that dominates
the energy density. We specialize to the case where the total curvature
perturbation arises predominantly from a spatially fluctuating decay rate.
Gaussian fluctuations in the decay rate are present if the inflaton coupling or
mass depends on some light field, which freely fluctuates during inflation. The
isocurvature fluctuations of the light field seeds the total curvature
perturbations, whose amplitude freezes after inflaton decay. We also analyze
the resulting curvature perturbation starting with non-negligible values of the
initial inflaton curvature. Lastly, we study the effects of the energy density
stored in the light field.


title: On the origin of the X-rays and the nature of accretion in NGC 4261

abstract:
  We report on the X-ray properties of the radio galaxy NGC 4261, combining
information from the XMM, Chandra, and SAX satellites. Goals of this study are
to investigate the origin of the X-rays from this low-power radio galaxy and
the nature of the accretion process onto the central black hole. The X-ray
spectrum of the nuclear source extending up to 100--150 keV is well described
by a partially covered (covering factor $>$ 0.8) power law with a photon index
\~1.5 absorbed by a column density 5e22 cm^-2. The X-ray luminosity associated
with the non-thermal component is ~5e41 erg/s. The nuclear source is embedded
in a diffuse hot gas (kT~0.6 keV), whose density profile implies a Bondi
accretion rate of 4.5e-2 solar masses/year. For the first time rapid X-ray
variability is detected in a low-power radio galaxy at more than 99% confidence
level. The observed X-ray spectral and variability properties indicate the
accretion flow as the most likely origin of the bulk X-ray continuum.This
conclusion is strengthened by energetic considerations based on a comparison
between the X-ray luminosity and the kinetic power of the jet, whichalso
suggest that the Bondi accretion rate overestimates the actual accretion rate
onto the black hole.


title: Fourier analysis of luminosity-dependent galaxy clustering

abstract:
  We extend the Fourier transform based method for the analysis of galaxy
redshift surveys of Feldman, Kaiser & Peacock (1994: FKP) to model
luminosity-dependent clustering. In a magnitude limited survey, galaxies at
high redshift are more luminous on average than galaxies at low redshift.
Galaxy clustering is observed to increase with luminosity, so the inferred
density field is effectively multiplied by an increasing function of radius.
This has the potential to distort the shape of the recovered power spectrum. In
this paper we present an extension of the FKP analysis method to incorporate
this effect, and present revised optimal weights to maximize the precision of
such an analysis. The method is tested and its accuracy assessed using mock
catalogues of the 2-degree field galaxy redshift survey (2dFGRS). We also show
that the systematic effect caused by ignoring luminosity-dependent bias was
negligible for the initial analysis of the 2dFGRS of Percival et al. (2001).
However, future surveys, sensitive to larger scales, or covering a wider range
of galaxy luminosities will benefit from this refined method.


title:
Non-Sobolev modelling of radiation pressure driven flows in Active
  Galactic Nuclei

abstract:
  We present a new general scheme for calculating the structure and dynamics of
radiation pressure driven, photoionized flows. The new method goes one step
beyond the Sobolev approximation. It involves a numerical solution of the
radiative transfer in absorption lines including the effects of differential
expansion and line interactions such as line locking and blanketing. We also
present a new scheme for calculating the radiation pressure due to trapped line
photons in finite, differentially expanding flows. We compare our results for
the radiation pressure force with those obtained using the Sobolev
approximation and show the limitations of the latter. In particular, we
demonstrate that the Sobolev method gives a poor approximation near
discontinuity surfaces and its neglect of line blanketing can lead to erroneous
results in high velocity flows. We combine the newly calculated radiation
pressure force with self-consistent photoionization and thermal calculations to
study the dynamics and spectral features of broad absorption line flows and
highly ionized gas flows in AGN. A comparison with Sobolev-type calculations
shows that the latter over estimates the flow's terminal velocity and,
conversely, under estimates its opacity. We also show that line locking on
broad emission lines can have a significant effect on the dynamics and spectral
features of AGN flows.


title: Continuum Shielding and Flow Dynamics in Active Galactic Nuclei

abstract:
  We study the ionization, thermal structure, and dynamics of AGN flows which
are partially shielded from the central continuum. We utilize detailed non-LTE
photoionization and radiative transfer code using exact (non-Sobolev)
calculations. We find that shielding has a pronounced effect on the ionization,
thermal structure, and the dynamics of such flows. Moderate shielding is
especially efficient in accelerating flows to high velocities since it
suppresses the ionization level of the gas. The ionization structure of
shielded gas tends to be distributed uniformly over a wide range of ionization
levels. In such gas, radiation pressure due to trapped line photons can
dominate over the thermal gas pressure and have a significant effect on the
thermal stability of the flow. Heavily shielded flows are driven mainly by line
radiation pressure, and so line locking has a large effect on the flow
dynamics. We show that the observed ``L_\alpha ghost'' is a natural outcome in
highly ionized flows that are shielded beyond the Lyman limit. We suggest that
high velocity AGN flows occupy only a small fraction of the volume and that
their density depends only weakly on the velocity field.


title: Magellan Echelle Spectroscopy of TW Hydrae Brown Dwarfs

abstract:
  We present high-resolution optical spectroscopy of four candidate members of
the nearby TW Hydrae young association including three brown dwarfs (2MASS
1207-3932, 2MASS 1139-3159 and TWA 5B) and one T Tauri multiple star (TWA 5A).
Using echelle spectra from the Magellan Baade 6.5-meter telescope, we confirm
the pre-main sequence status and cluster membership of the substellar
candidates, through the detection of LiI, NaI consistent with low gravity, and
radial velocity. Given their late spectral type (~M8) and the youth of the
association (age ~10Myr), cluster membership certifies these three objects as
very low-mass young brown dwarfs. One of them (2MASS 1207-3932) shows strong
emission both in the Hydrogen Balmer series (H_alpha to H_epsilon) and in HeI
(4471, 5876, 6678 and 7065 A), compared to other young brown dwarfs of similar
spectral type. The H_alpha line is also relatively broad (10% width ~200 km/s)
and asymmetric. These characteristics suggest that 2MASS 1207-3932 is a (weak)
accretor. While we cannot rule out activity, comparison to a flaring field
dwarf implies that such activity would have to be quite anomalous. The
verification of accretion would make 2MASS 1207-3932 the oldest actively
accreting brown dwarf known to date, suggesting that inner disk lifetimes in
substellar objects can be comparable to those in stars, consistent with a
similar formation mechanism. Finally, TWA 5A appears to be a variable accretor:
observations separated by two days show broad accretion-like H_alpha (10% width
\~270 km/s), with significant changes in the H_alpha profile, as well as in the
strengths of HeI, Na D and [OI 6300]. TWA 5A is known to be a close triple;
thus, our result implies that long-lived disks can exist even in multiple
systems.


title: Properties of galaxy dark matter halos from weak lensing

abstract:
  We present the results of a study of weak lensing by galaxies based on 45.5
deg$^2$ of $R_C$ band imaging data from the Red-Sequence Cluster Survey (RCS).
We present the first weak lensing detection of the flattening of galaxy dark
matter halos. We use a simple model in which the ellipticity of the halo is $f$
times the observed ellipticity of the lens. We find a best fit value of
$f=0.77^{+0.18}_{-0.21}$, suggesting that the dark matter halos are somewhat
rounder than the light distribution. The fact that we detect a significant
flattening implies that the halos are well aligned with the light distribution.
Given the average ellipticity of the lenses, this implies a halo ellipticity of
$<e_{\rm halo} >=0.33^{+0.07}_{-0.09}$, in fair agreement with results from
numerical simulations of CDM. This result provides strong support for the
existence of dark matter, as an isotropic lensing signal is excluded with 99.5%
confidence. We also study the average mass profile around the lenses, using a
maximum likelihood analysis. We consider two models for the halo mass profile:
a truncated isothermal sphere (TIS) and an NFW profile. We adopt
observationally motivated scaling relations between the lens luminosity and the
velocity dispersion and the extent of the halo. The best fit NFW model yields a
mass $M_{200}=(8.4\pm0.7\pm0.4)\times 10^{11} h^{-1} M_\odot$ and a scale
radius $r_s=16.2^{+3.6}_{-2.9} h^{-1}$ kpc. This value for the scale radius is
in excellent agreement with predictions from numerical simulations for a halo
of this mass.


title: Isolated magnetar spin-down, soft X-ray emission and RXJ1856.5-3754

abstract:
  When an isolated magnetar with magnetic dipole field B ~ 10^15 G moves at
high velocity (v > 10^7 cm/s) through the ISM, its transition into propeller
effect driven spin-down may occur in less than 10^6 years. We propose that the
nearby neutron star RXJ1856.5-3754 is such a magnetar, and has spun down by the
propeller effect to a period greater than 10^4 sec within ~5*10^5 years. This
magnetar scenario is consistent with observed thermal X-ray emission properties
and the absence of detectable spin-modulations of them. Detection of other
rapidly moving long period (> 100 sec) magnetars with known ages would strongly
constrain the very great variety of predicted propeller-effect torque
magnitudes.


abstract:
  We present spectral analysis from XMM-Newton observations of the Vela pulsar.
We analyzed thermal emission from the pulsar dominating below ~ 1 keV since
extracted spectra are heavily contaminated by nebular emission at higher
energy. Featureless high-resolution spectra of the Reflection Grating
Spectrometer aboard XMM-Newton suggest the presence of a hydrogen atmosphere,
as previously indicated by Chandra results. Both the temperature and radius are
consistent with those values deduced from Chandra. The derived Chandra and
XMM-Newton temperature of T^{\infty} ~ (6.4-7.1)*10^5 K at its age of ~10^4
years is below the standard cooling curve.


title: Eddington Accretion and QSO Emission Lines at z ~ 2

abstract:
  Broad Absorption Line (BAL) QSOs have been suggested to be youthful
super-accretors based on their powerful radiatively driven absorbing outflows
and often reddened continua. To test this hypothesis, we observed near IR
spectra of the H$\beta$ region for 11 bright BAL QSOs at redshift z ~ 2. We
measured these and literature spectra for 6 BAL QSOs, 13 radio-loud and 7
radio-quiet non-BAL QSOs. Using the luminosity and H$\beta$ broad line width to
derive black hole mass and accretion rate, we find that both BAL and non-BAL
QSOs at z ~ 2 tend to have higher $L/L_{Edd}$ than those at low z -- probably a
result of selecting the brightest QSOs. However, we find that the high z QSOs,
in particular the BAL QSOs, have extremely strong Fe II and very weak [O III],
extending the inverse relationship found for low z QSOs. This suggests that,
even while radiating near $L_{Edd}$, the BAL QSOs have a more plentiful fuel
supply than non-BAL QSOs. Comparison with low z QSOs shows for the first time
that the inverse Fe II -- [O III] relationship is indeed related to
$L/L_{Edd}$, rather than black hole mass.


title:
Magneto-Centrifugal Launching of Jets from Accretion Disks. II: Inner
  Disk-Driven Winds

abstract:
  We follow numerically the time evolution of axisymmetric outflows driven
magneto-centrifugally from the inner portion of accretion disks, from their
launching surface to large, observable distances. Special attention is paid to
the collimation of part of the outflow into a dense, narrow jet around the
rotation axis, after a steady state has been reached. For parameters typical of
T Tauri stars, we define a fiducial ``jet'' as outlined by the contour of
constant density at 10^4 cm^{-3}. We find that the jet, so defined, appears
nearly cylindrical well above the disk, in agreement with previous asymptotic
analyses. Closer to the equatorial plane, the density contour can either bulge
outwards or pinch inwards, depending on the conditions at the launching
surface, particularly the mass flux distribution. We find that even though a
dense, jet-like feature is always formed around the axis, there is no guarantee
that the high-density axial jet would dominate the more tenuous, wide-angle
part of the wind. Specifically, on the 100 AU scale, resolvable by HST and
ground-based adaptive optics for nearby T Tauri winds, the fraction of the wind
mass flux enclosed by the fiducial jet can vary substantially, again depending
on the launching conditions. We show two examples in which the fraction is ~20%
and ~45%. These dependences may provide a way to constrain the conditions at
the launching surface, which are poorly known at present.


title:
How reliable is the kinematical evidence for dark matter: the effects of
  non-sphericity, substructure and streaming motions

abstract:
  Using cosmological $N$-body simulations of dark matter haloes, we study the
effects of non-sphericity, substructure and streaming motions in reproducing
the structure and internal kinematics of clusters of galaxies from kinematical
measurements. Fitting an NFW model to the 3D density profile, we determine the
virial mass, concentration parameter and velocity anisotropy of the haloes, and
then calculate the profiles of projected velocity moments, as they would be
measured by a distant observer. Using these mock data, we apply a Jeans
analysis for spherical objects to reproduce the line-of-sight velocity
dispersion and kurtosis and fit the three parameters. We find that the
line-of-sight velocity dispersion and kurtosis profiles of a given halo can
vary considerably with the angle of view of the observer. We show that the
virial mass, concentration parameter and velocity anisotropy of the haloes can
be reproduced satisfactorily independently of the halo shape, although the
virial mass tends to be underestimated, the concentration parameter
overestimated, while the recovered anisotropy is typically more tangential than
the true one. The mass, concentration and velocity anisotropy of haloes are
recovered with better precision when their mean velocity profiles are near
zero.


title: Non-Fickian diffusion and tau approximation from numerical turbulence

abstract:
  Evidence for non-Fickian diffusion of a passive scalar is presented using
direct simulations of homogeneous isotropic turbulence. The results compare
favorably with an explicitly time-dependent closure model based on the tau
approximation. In the numerical experiments three different cases are
considered: (i) zero mean concentration with finite initial concentration flux,
(ii) an initial top hat profile for the concentration, and (iii) an imposed
background concentration gradient. All cases agree in the resulting relaxation
time in the tau approximation relating the triple correlation to the
concentration flux. The first order smoothing approximation is shown to be
inapplicable.


title:
The temporal and spatial evolution of the starburst in ESO 338-IG04 as
  probed by its star clusters

abstract:
  In this paper we use ultra-violet (UV) and optical HST photometry in five
bands, and an extensive set of spectral evolutionary synthesis scenarios to
investigate the age and masses of 124 star clusters in the luminous blue
compact galaxy ESO338-IG04 (Tololo 1924-416). The very small internal reddening
makes ESO 338-IG04 an excellent laboratory for studying the formation of
massive star clusters. We have used the star clusters to trace the temporal and
spatial evolution of the starburst, and to put constraints on the star
formation activity over a cosmological time-scale. The present starburst has
been active for about 40 Myr. A standard Salpeter initial mass function (IMF)
extending up to 120 solar masses provides the best fit to the data, although a
flatter IMF cannot be excluded. The compact star clusters provide 30-40 percent
of the UV luminosity and star formation activity. We find no evidence for dust
obscuration even among the youngest (< 1 Myr) clusters. The fraction of stellar
mass contained in compact star clusters is found to be several percent, which
is an unusually high value. The intermediate age clusters show a flattened
space distribution which agrees with the isophotal shape of the galaxy, whereas
the oldest clusters seem to have a spherical distribution.(abridged)


title: Inflationary parameters and primordial perturbation spectra

abstract:
  I discuss how parameters describing inflation in the very early universe may
be related to primordial perturbation spectra. Precision observations of
anisotropies in the cosmic microwave background (CMB) such as those provided by
the WMAP satellite offer an unprecedented window onto the physics of the very
early universe. To theorists exploring speculative models of physics at high
energies, the CMB offers us the chance to put our ideas to the test.


title: What Fraction of Sun-like Stars have Planets?

abstract:
  The radial velocities of ~1800 nearby Sun-like stars are currently being
monitored by eight high-sensitivity Doppler exoplanet surveys. Approximately 90
of these stars have been found to host exoplanets massive enough to be
detectable. Thus at least ~5% of target stars possess planets. If we limit our
analysis to target stars that have been monitored the longest (~15 years), ~11%
possess planets. If we limit our analysis to stars monitored the longest and
whose low surface activity allow the most precise velocity measurements, ~25%
possess planets. By identifying trends of the exoplanet mass and period
distributions in a sub-sample of exoplanets less-biased by selection effects,
and linearly extrapolating these trends into regions of parameter space that
have not yet been completely sampled, we find at least ~9% of Sun-like stars
have planets in the mass and orbital period ranges Msin(i) > 0.3 M_Jupiter and
P < 13 years, and at least ~22% have planets in the larger range Msin(i) > 0.1
M_Jupiter and P < 60 years. Even this larger area of the mass-period plane is
less than 20% of the area occupied by our planetary system, suggesting that
this estimate is still a lower limit to the true fraction of Sun-like stars
with planets, which may be as large as ~100%.


title:
GMRT detection of HI 21 cm associated absorption towards the z=1.2 red
  quasar 3C 190

abstract:
  We report the GMRT detection of associated HI 21 cm-line absorption in the
z=1.1946 red quasar 3C 190. Most of the absorption is blue-shifted with respect
to the systemic redshift. The absorption, at $\sim$ 647.7 MHz, is broad and
complex, spanning a velocity width of $\sim$ 600 \kms. Since the core is
self-absorbed at this frequency, the absorption is most likely towards the
hotspots. Comparison of the radio and deep optical images reveal linear
filaments in the optical which overlap with the brighter radio jet towards the
south-west. We therefore suggest that most of the HI 21 cm-line absorption
could be occurring in the atomic gas shocked by the south-west jet.


title:
Discovery of narrow X-ray absorption features from the low-mass X-ray
  binary X 1254-690 with XMM-Newton

abstract:
  We report on two XMM-Newton observations of the low-mass X-ray binary X
1254-690. During an XMM-Newton observation of the low-mass X-ray binary in 2001
January a deep X-ray dip was seen while in a second observation one year later
no dips were evident. The 0.5-10 keV EPIC spectra from both non-dipping
intervals are very similar being modeled by a disk-blackbody and a power-law
continuum with additional structure around 1 keV and narrow absorption features
at 7.0 keV and 8.2 keV which are identified with the K alpha and K beta
absorption lines of Fe XXVI. The low-energy structure may be modeled as a 175
eV (sigma) wide emission line at ~0.95 keV. This feature is probably the same
structure that was modeled as an absorption edge in an earlier BeppoSAX
observation. The absorption line properties show no obvious dependence on
orbital phase and are similar in both observations suggesting that the
occurrence of such features is not directly related to the presence of dipping
activity. Narrow Fe absorption features have been observed from the two
superluminal jet sources GRO J1655-40 and GRS 1915+105, and the four low-mass
X-ray binaries GX 13+1, MXB 1658-298, X 1624-490 and X 1254-690. Since the
latter 3 sources are dipping sources, which are systems viewed close to the
accretion disk plane, and the two microquasars are thought to be viewed at an
inclination of ~70 degrees, this suggests that these features are more
prominent when viewed at high-inclination angles. This, together with the lack
of any orbital dependence, implies a cylindrical geometry for the absorbing
material.


title: Carbon abundances and 12C/13C from globular cluster giants

abstract:
  The behaviour of the Delta nu =2 CO bands around 2.3 micron was examined by
comparing observed and synthetic spectra in stars in globular clusters of
different metallicity.
  Changes in the 12C/13C isotopic ratio and the carbon abundances were
investigated in stars from 3500--4900 K in the galactic globular clusters M71,
M5, M3 and M13, covering the metallicity range from --0.7 to --1.6. We found
relatively low carbon abundances that are not affected by the value of oxygen
abundance. For most giants the 12C/13C ratios determined are consistent with
the equilibrium value for the CN cycle. This suggests complete mixing on the
ascent of the red giant branch, in contrast to the substantially higher values
predicted across this range of parameters by the current generation of models.
We found some evidence for a larger dispersion of \CDC in giants of M71 of
metallicity [mu] = [M/H] = -0.7 in comparison with the giants of M3, M5 and
M13, which are more metal deficient.
  Finally, we show evidence for lower 12C/13C in giants of globular clusters
with lower metallicities, as predicted by theory.


title:
Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading
  and Size of Sample Effects

abstract:
  The properties of 939 star clusters in the Large and Small Magellanic Clouds
were determined from ground-based CCD images in UBVR passbands. The areal
coverage was extensive, corresponding to 11.0 sq-kpc in the LMC and 8.3 sq-kpc
in the SMC. After corrections for reddening, the colors and magnitudes of the
clusters were converted to ages and masses, and the resulting mass
distributions were searched for the effects of fading, evaporation, and
size-of-sample bias. The data show a clear signature of cluster fading below
the detection threshold. The initial cluster mass function (ICMF) was
determined by fitting the mass and age distributions with cluster population
models. These models suggest a new method to determine the ICMF that is nearly
independent of fading or disruption and is based on the slope of a correlation
between age and the maximum cluster mass in equally spaced intervals of
log-age. For a nearly uniform star formation rate, this correlation has a slope
equal to 1/(alpha-1) for an ICMF of dn(M)/dM proportional to M^-alpha. We
determine that alpha is between 2 and 2.4 for the LMC and SMC using this method
plus another method in which models are fit to the mass distribution integrated
over age and to the age distribution integrated over mass. The maximum mass
method also suggests that the cluster formation rate in the LMC age gap between
3 and 13 Gy is about a factor of ten below that in the period from 0.1 Gy to 1
Gy. The oldest clusters correspond in age and mass to halo globular clusters in
the Milky Way. They do not fit the trends for lower-mass clusters but appear to
be a separate population that either had a very high star formation rate and
became depleted by evaporation or formed with only high masses.


title:
Faraday Rotation as a Diagnostic of Galactic Foreground Contamination of
  CMB Maps

abstract:
  We present a diagnostic test of possible Galactic contamination of cosmic
microwave background sky maps designed to provide an independent check on the
methods used to compile these maps. The method involves a non-parametric
measurement of cross-correlation between the Faraday rotation measure (RM) of
extragalactic sources and the measured microwave signal at the same angular
position. We argue that statistical properties of the observed distribution of
rotation measures are consistent with a Galactic origin, an argument reinforced
by a direct measurement of cross-correlation between dust, free-free and
synchrotron foreground maps and RM values with the strongest correlation being
for dust and free-free. We do not find any statistically compelling evidence
for correlations between the RM values and the COBE DMR maps at any frequency,
so there is no evidence of residual contamination in these CMB maps. On the
other hand, there is a statistically significant correlation of RM with the
preliminary WMAP individual frequency maps which remains significant in the
Tegmark et al. Wiener-filtered map but not in the Internal Linear Combination
map produced by the WMAP team.


title: The X-ray absorber of PKS2126-158

abstract:
  BeppoSAX observed the z=3.27 quasar PKS2126-158 on 1999 May 24-28 when its
2-10keV and 0.1-2.5keV fluxes were 1.1E-11 and 4.4E-12 cgs respectively, a
factor of 2 higher than in all previous ROSAT and ASCA observations and 40%
higher than in two more recent Chandra and XMM-Newton observations. The
shortest detected rest frame variability timescale is of a few months,
comparable to the causal timescale associated to an emission region of ~10
Schwarzschild radii around a few 1E10 solar masses black hole. The source is
detected with a signal to noise ratio S/N>=3 up to ~50 keV, 215 keV rest frame.
The BeppoSAX observations confirm the presence of low energy absorption along
the line of sight, independent on the continuum model adopted, at high
confidence level. Despite the limited spectral resolution of the BeppoSAX LECS
and MECS it is possible to put constraints on different absorption and
continuum models, but not to unambiguously determine the redshift of the
absorber. If the absorber is not significantly ionized the BeppoSAX data do
prefer an absorber at z<=2.7. Strong and complex metal line systems along the
line of sight to PKS2126-158 have been found at z=0.6631 and at 2.64<z<2.82.
They could well be associated to the X-ray absorption. Conversely, an ionized
(``warm'') absorber at the quasar redshift provides a good fit only if the iron
abundance is smaller than ~0.3 solar, while that of the other elements is fixed
to the solar value.


title: Atmospheric models of red giants with massive scale NLTE

abstract:
  We present plane-parallel and spherical LTE and NLTE atmospheric models of a
variety of stellar parameters of the red giant star Arcturus (alpha Boo,
HD124897, HR5340) and study their ability to fit the measured absolute flux
distribution. Our NLTE models include tens of thousands of the strongest lines
in NLTE, and we investigate separately the effects of treating the light metals
and the Fe group elements Fe and Ti in NLTE. We find that the NLTE effects of
Fe group elements on the model structure and flux distribution are much more
important than the NLTE effects of all the light metals combined, and serve to
substantially increases the violet and near UV flux level as a result of NLTE
Fe over-ionization. Both the LTE and NLTE models predict significantly more
flux in the blue and UV bands than is observed. We find that within the
moderately metal-poor metallicity range, the effect of NLTE on the overall UV
flux level decreases with decreasing metallicity. These results suggest that
there may still be important UV opacity missing from the models. We find that
models of solar metallicity giants of similar spectral type to Arcturus fit
well the observed flux distributions of those stars from the red to the near UV
band. This suggests that the blue and near UV flux discrepancy is metallicity
dependent, increasing with decreasing metallicity.


title: Evolution of Magnetic fields in Bok globules?

abstract:
  We study the influence and structure of the magnetic field in the early
phases of low-mass star formation using polarization maps of Bok globules at a
wavelength of 850micron, obtained with the Submillimeter Common-User Bolometer
Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT). We discuss
observations of the following sources: CB26 - a small globule with a nearly
dispersed dense core and a young and large circumstellar disk, CB54 - a large
globule with a massive dense core and a deeply embedded young stellar cluster,
and B335, CB230, and CB244 - three nearby, relatively isolated small globules
with low-mass protostellar cores.
  We find strongly aligned polarization vectors in the case of CB26, B335, and
CB230, while the vector orientations in the case of CB54 and CB244 are more or
less randomly distributed. The degree of polarization, amounting to several
percent, was found to decrease toward the center in each source. Assuming
dichroic emission by aligned non-spherical grains as the polarization
mechanism, where the magnetic field plays a role in the alignment process, we
derive magnetic field strengths and structures from the observed polarization
patterns.
  We compare the magnetic field topology with the morphology and outflow
directions of the globules. In the Class 0 sources B335, CB230, and CB244, the
magnetic field is oriented almost perpendicular to the ouflow direction. In
contrast, the inclination between outflow axis and magnetic field direction is
much more moderate (36deg) in the more evolved Class I source CB26.


title: Revisited abundance diagnostics in quasars: Fe II/Mg II ratios

abstract:
  Both the Fe II UV emission in the 2000- 3000 A region [Fe II (UV)] and
resonance emission line complex of Mg II at 2800 A are prominent features in
quasar spectra. The observed Fe II UV/ Mg II emission ratios have been proposed
as means to measure the buildup of the Fe abundance relative to that of the
alpha-elements C, N, O, Ne and Mg as a function of redshift. The current
observed ratios show large scatter and no obvious dependence on redshift. Thus,
it remains unresolved whether a dependence on redshift exists and whether the
observed Fe II UV/ Mg II ratios represent a real nucleosynthesis diagnostic. We
have used our new 830-level model atom for Fe+ in photoionization calculations,
reproducing the physical conditions in the broad line regions of quasars. This
modeling reveals that interpretations of high values of Fe II UV/ Mg II are
sensitive not only to Fe and Mg abundance, but also to other factors such as
microturbulence, density, and properties of the radiation field. We find that
the Fe II UV/ Mg II ratio combined with Fe II (UV)/ Fe II (Optical) emission
ratio, where Fe II (Optical) denotes Fe II emission in 4000 - 6000 A can be
used as a reliable nucleosynthesis diagnostic for the Fe/Mg abundance ratios
for the physical conditions relevant to the broad-line regions (BLRs) of
quasars. This has extreme importance for quasar observations with the Hubble
Space Telescope and also with the future James Webb Space Telescope.


title:
New High Proper Motion Stars from the Digitized Sky Survey. II. Northern
  Stars with 0.5<mu<2.0 arcsec/yr at High Galactic Latitudes

abstract:
  In a continuation of our systematic search for high proper motion stars in
the Digitized Sky Survey, we have completed the analysis of northern sky fields
at galactic latitudes above 25 degrees. With the help of our SUPERBLINK
software, a powerful automated blink comparator developed by us, we have
identified 1146 stars in the magnitude range 8<r<20 with proper motions
0.500<mu<2.000 arcsec/yr. These include 1080 stars previously listed in
Luyten's proper motion catalogs (LHS, NLTT), 9 stars not previously listed in
the Luyten catalogs but reported elsewhere in the literature (including 1
previously reported by our team), and 57 new objects reported here for the
first time. This paper includes a list of positions, proper motions,
magnitudes, and finder charts for all the new high proper motion stars.
Combined with our previous study of low galactic latitude fields (see Paper I),
our survey now covers over 98% of the northern sky. We conclude that the Luyten
catalogs were 90% complete in the northern sky for stars with 0.5<mu<2.0
arcsec/yr down to magnitude r=19. We discuss the incompleteness of the old
Luyten proper motion survey, and estimate completeness limits for our new
survey.


title: Circulation Flows: Cooling Flows with Bubble Return

abstract:
  The failure of the XMM-Newton and Chandra X-ray telescopes to detect cooling
gas in elliptical galaxies and clusters of galaxies has led many to adopt the
position that the gas is not cooling at all and that heating by an active
nucleus in the central E or cD galaxy is sufficient to offset radiative
cooling. In this paper we explore an idealized limiting example of this point
of view in which hot, buoyant bubbles formed near the center return the
inflowing, radiatively cooling gas to distant regions in the flow. We show that
idealized steady state, centrally heated non-cooling flows can indeed be
constructed. In addition, the emission-weighted temperature profiles in these
circulating flows resemble those of normal cooling flows. However, these
solutions are valid only (1) for a range of bubble parameters for which there
is no independent justification, (2) for a limited spatial region in the
cooling flow and (3) for a limited period of time after which cooling seems
inevitable. Our exploration of non-cooling flows is set in the context of
galaxy/group flows.


title: Neutrino Astronomy at the South Pole: Status of the AMANDA Experiment

abstract:
  AMANDA (Antarctic Muon And Neutrino Detector Array) is a neutrino telescope
built under the southern polar icecap, and its scope is exploring the
possibility to detect high energy cosmic neutrinos generated by powerful
celestial objects where acceleration mechanisms can bring protons up to 10^20
eV. We describe the achievements and results from the AMANDA-B10 prototype and
the preliminary results from the current AMANDA-II detector showing a dramatic
increase in sensitivity. An outlook on IceCube will be given.


title:
Keck Adaptive Optics Imaging of Nearby Young Stars: Detection of Close
  Multiple Systems

abstract:
  Using adaptive optics on the Keck II 10-meter telescope on Mauna Kea, we have
surveyed 24 of the nearest young stars known in search of close companions. Our
sample includes members of the MBM 12 and TW Hydrae young associations and the
classical T Tauri binary UY Aurigae in the Taurus star-forming region. We
present relative photometry and accurate astrometry for 10 close multiple
systems. The multiplicity frequency in the TW Hydrae and MBM 12 groups are high
in comparison to other young regions, though the significance of this result is
low because of the small number statistics. We resolve S 18 into a triple
system including a tight 63 mas (projected separation of 17 AU at a distance of
275 pc) binary for the first time, with a hierarchical configuration
reminiscent of VW Chamaeleontis and T Tauri. Another tight binary in our sample
-- TWA 5Aab (54 mas or 3 AU at 55 pc) -- offers the prospect of dynamical mass
measurement using astrometric observations within a few years, and thus could
be important for testing pre-main sequence evolutionary models. Our
observations confirm with 9-sigma confidence that the brown dwarf TWA 5B is
bound to TWA 5A. We find that the flux ratio of UY Aur has changed
dramatically, by more than a magnitude in the H-band, possibly as a result of
variable extinction. With a smaller flux ratio, the system may once again
become detectable as an optical binary, as it was at the time of its discovery
in 1944. Taken together, our results demonstrate that adaptive optics on large
telescopes is a powerful tool for detecting tight companions, and thus
exploring the frequency and configurations of close multiple systems.


title:
CAIRNS: The Cluster And Infall Region Nearby Survey I. Redshifts and
  Mass Profiles

abstract:
  The CAIRNS (Cluster And Infall Region Nearby Survey) project is a
spectroscopic survey of the infall regions surrounding eight nearby, rich,
X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or
remeasured) within \sim 5-10 Mpc of the centers of the clusters, making it the
largest study of the infall regions of clusters. We determine cluster
membership and the mass profiles of the clusters based on the phase space
distribution of the galaxies. All of the clusters display decreasing velocity
dispersion profiles. The mass profiles are fit well by functional forms based
on numerical simulations but exclude an isothermal sphere. Specifically, NFW
and Hernquist models provide good descriptions of cluster mass profiles to
their turnaround radii. Our sample shows that the predicted infall pattern is
ubiquitous in rich, X-ray luminous clusters over a large mass range. The
caustic mass estimates are in excellent agreement with independent X-ray
estimates at small radii and with virial estimates at intermediate radii. The
mean ratio of the caustic mass to the X-ray mass is 1.03\pm0.11 and the mean
ratio of the caustic mass to the virial mass (when corrected for the surface
pressure term) is 0.93\pm0.07. We further demonstrate that the caustic
technique provides reasonable mass estimates even in merging clusters.


title:
Limits on eclipses of the pre-main-sequence star KH 15D in the first
  half of the 20th century

abstract:
  Over the last decade, the pre-main sequence star KH 15D has exhibited
periodic eclipses that are surprisingly deep (~3 mag) and long-lasting (~40% of
the 48.4-day period). The cause of the eclipses is unknown, but it could be a
feature in a nearly edge-on protoplanetary disk. Here we report on an analysis
of archival photographs of KH 15D from the Harvard College Observatory plate
collection, most of which were taken during the years 1913-1951. During this
time range, the data are consistent with no eclipses; the duty cycle of 1 mag
eclipses was less than 20%. The decadal timescale of this change in eclipse
behavior is compatible with the expected timescale of protoplanet/disk
interactions. Archival images from more recent epochs should reveal the onset
of the eclipses.


title: Iron K features in the hard X-ray XMM-Newton spectrum of NGC 4151

abstract:
  Recent XMM-Newton observations have measured the hard (2.5-12 keV) X-ray
spectrum of the well-known Seyfert galaxy NGC 4151 with a signal-to-noise
unprecedented for this source. We find that a spectral model, developed to fit
previous Beppo-SAX and ASCA observations of NGC 4151, provides an excellent
description of the XMM-Newton EPIC data. The results support the view that it
is the level of the continuum that is the main driver of the complex spectral
variability exhibited by NGC 4151. We focus on the iron K features in the NGC
4151 spectrum. There is no requirement for a relativistically broadened iron Ka
line, in contrast to several earlier studies. The iron Ka line profile is well
modelled by a narrow Gaussian, the intensity of which varies by ~25% on
timescales of about a year. There is also a strong suggestion that the cold
media present in the active nucleus of NGC 4151 have an iron abundance that is
at least twice the solar value.


title:
Massive stars and the energy balance of the ISM. I. The impact of an
  isolated 60 Msun star

abstract:
  We present results of numerical simulations carried out with a 2D radiation
hydrodynamics code in order to study the impact of massive stars on their
surrounding interstellar medium. This first paper deals with the evolution of
the circumstellar gas around an isolated 60 Msun star. The interaction of the
photoionized HII region with the stellar wind bubble forms a variety of
interesting structures like shells, clouds, fingers, and spokes. These results
demonstrate that complex structures found in HII regions are not necessarily
relics from the time before the gas became ionized but may result from
dynamical processes during the course of the HII region evolution. We have also
analyzed the transfer and deposit of the stellar wind and radiation energy into
the circumstellar medium until the star explodes as a supernova. Although the
total mechanical wind energy supplied by the star is negligible compared to the
accumulated energy of the Lyman continuum photons, the kinetic energy imparted
to the circumstellar gas over the star's lifetime is 4 times higher than for a
comparable windless simulation. Furthermore, the thermal energy of warm
photoionized gas is lower by some 55%. Our results document the necessity to
consider both ionizing radiation and stellar winds for an appropriate
description of the interaction of OB stars with their circumstellar
environment.


title:
High-resolution spectroscopic follow-up of OGLE planetary transit
  candidates in the Galactic bulge: two possible Jupiter-mass planets and two
  blends

abstract:
  We report the results of our campaign to follow-up spectroscopically several
candidate extrasolar transiting planets from the OGLE-III survey in the
direction of the Galactic center, announced in 2001 (Udalski et al 2002a,b).
All of these objects present shallow and periodic dips in brightness that may
be due to planetary companions. Our high-resolution Keck I/HIRES observations
have revealed two interesting cases (OGLE-TR-10 with a period of 3.1 days, and
OGLE-TR-58 with a period of 4.3 days) that show no radial velocity variations
at the level of 100--200 m/s. If orbited by companions, their masses would be
similar to Jupiter. With the information in hand (including the light curves)
we are not able to rule out that these candidates are instead the result of
contamination from an eclipsing binary in the same line of sight (a "blend").
We discuss also the case of OGLE-TR-56 that was recently reported by Konacki et
al (2003) to have a Jupiter-size companion, based on an earlier analysis of our
data, and we present supporting information. Two other candidates, OGLE-TR-3
and OGLE-TR-33, show clear evidence that they are blends.


title: Indications of Inflow Motions in Regions Forming Massive Stars

abstract:
  Observational evidence for inflowing motions in massive star forming regions
has been extremely rare. We have made a spectroscopic survey of a sample of 28
massive star forming cores associated with water masers. An optically thick
line of HCN (3-2) was used in combination with optically thin lines [H^{13}CN
(3-2) or C^{34}S (5-4), (3-2), and (2-1)], to identify ``blue'' line profiles
that can indicate inflow. Comparing intensities for 18 double-peaked line
profiles yields 11 blue and 3 red profiles that are statistically significant.
In the full sample of 28 sources, 12 show blue profiles and 6 show red profiles
that are statistically significant based on the velocity offsets of lines that
are optically thick from those that are optically thin. These results indicate
that HCN (3-2) emission may trace inflow in regions forming high-mass stars.


title:
Europium Isotope Ratios in s-Process-Element-Enhanced, Metal-Poor Stars:
  A New Probe of the 151Sm Branching

abstract:
  We report on the first measurement of the Eu isotope fractions (151Eu and
153Eu) in s-process-element-enhanced, metal-poor stars. We use these ratios to
investigate the 151Sm branching of s-process nucleosynthesis. The measurement
was made by detailed study of Eu II lines that are significantly affected by
hyperfine splitting and isotope shifts in spectra of the carbon-rich, very
metal-poor stars LP625-44 and CS31062-050, observed with the Subaru Telescope
High Dispersion Spectrograph. The 151Eu fractions [fr(151Eu) =
151Eu/(151Eu+153Eu)] derived for LP625-44 and CS31062-050 are 0.60 and 0.55,
respectively, with uncertainties of about +/- 0.05. These values are higher
than found in solar-system material, but agree well with the predictions of
recent s-process models. We derive new constraints on the temperature and
neutron density during the s-process based on calculations of pulsed s-process
models for the 151Eu fraction.


title:
On the master equation approach to diffusive grain-surface chemistry:
  the H, O, CO system

abstract:
  We have used the master equation approach to study a moderately complex
network of diffusive reactions occurring on the surfaces of interstellar dust
particles. This network is meant to apply to dense clouds in which a large
portion of the gas-phase carbon has already been converted to carbon monoxide.
Hydrogen atoms, oxygen atoms, and CO molecules are allowed to accrete onto dust
particles and their chemistry is followed. The stable molecules produced are
oxygen, hydrogen, water, carbon dioxide (CO2), formaldehyde (H2CO), and
methanol (CH3OH). The surface abundances calculated via the master equation
approach are in good agreement with those obtained via a Monte Carlo method but
can differ considerably from those obtained with standard rate equations.


title:
Spectral Energy Distribution in Supercritical Disk Accretion Flows
  through Photon-trapping Effects

abstract:
  We investigate the spectral energy distribution (SED) of the supercritical
disk accretion flows around black holes by solving the multi-frequency zeroth
moment equation of the radiation transfer equation under the flux-limited
diffusion approximation as well as the energy equation of gas. Special
attention is paid to the photon-trapping effects, the effects that photons are
trapped within accretion flow and are swallowed by a black hole, with little
being radiated away. It is found that when flow luminosity is below about twice
the Eddington luminosity (L<2L_E) photon trapping is ineffective and the SED
shifts to the higher-energy side as L increases. The peak frequency at which
the SED reaches its peak becomes at maximum three times higher than that given
by the standard-disk model, which might resolve the so-called 'too hot
accretion disk problem.' When L>2L_E, in contrast the peak frequency of the SED
tends to decrease with increase of mass-accretion rate. This is due to enhanced
photon-trapping. Since high-energy photons are generated near the equatorial
plane, they can be more effectively trapped in flow than low-energy ones and,
hence, the high energy part of radiation is suppressed. Finally, the observed
time variation of IC 342 S1, which is an ultraluminous X-ray source, in the
X-ray HR diagram can be explained by the modulation of the mass accretion rate.
In comparison with the observational data, we estimate the mass of black hole
in IC 342 S1 is around 100 solar mass.


title: Clump Development by the Nickel Bubble Effect in Supernovae

abstract:
  We used one-dimensional radiative-transport radiation hydrodynamical (RHD)
simulations to investigate the formation of clumping in freely-expanding
supernova ejecta due to the radioactive heating from the Ni56 -> Co56 -> Fe56
decay sequence. The heating gives rise to an inflated Nickel bubble, which
induces a forward shock that compresses the outer ambient gas into a shell. The
radiative energy deposited by the radioactivity leaks out across the shock by
radiative diffusion, and we investigate its effect on the evolution of the
ejecta structure. Compared to the hydrodynamical adiabatic approximation with
gamma =4/3, the preshock gas becomes accelerated by the radiation outflow. The
shock is thus weakened and the shell becomes broader and less dense. The
thickness of the shell takes up <~ 4 % of the radius of the bubble, and the
structure of the shell can be approximately described by a self-similar
solution. We compared the properties of the shell components with those of the
ejecta clumps indicated by our previous hydrodynamical simulations for the
later interaction of clumps with the outer supernova remnant. The high density
contrast across the shell, chi ~ 100, is compatible with that of ejecta clumps
as indicated for Tycho's knots, but there is insufficient dense gas to cause a
pronounced protrusion on the outline of a core collapse supernova remnant, like
the bullets in the Vela remnant.


title:
Model for Relaxation Oscillations of Luminous Accretion Disk in
  GRS1915+105: Variable Inner Edge

abstract:
  To understand the bursting behavior of the microquasar GRS 1915+105, we
calculate time evolution of a luminous, optically thick accretion disk around a
stellar mass black hole undergoing limit-cycle oscillations between the high-
and low- luminosity states. We, especially, carefully solve the behavior of the
innermost part of the disk, since it produces significant number of photons
during the burst, and fit the theoretical spectra with the multi-color disk
model. The fitting parameters are $\Tin$ (the maximum disk temperature) and
$\Rin$ (the innermost radius of the disk). We find an abrupt, transient
increase in $\Tin$ and a temporary decrease in $\Rin$ during a burst, which are
actually observed in GRS 1915+105. The precise behavior is subject to the
viscosity prescription. We prescribe the radial-azimuthal component of
viscosity stress tensor to be $T_{r \phi}=-\alpha \Pi (p_{\rm gas}/p)^{\mu}$,
with $\Pi$ being the height integrated pressure, $\alpha$ and $\mu$ being the
parameter, and $p$ and $p_{\rm gas}$ being the total pressure and gas pressure
on the equatorial plane, respectively. Model with $\mu=0.1$ can produce the
overall time changes of $\Tin$ and $\Rin$, but cannot give an excellent fit to
the observed amplitudes. Model with $\mu=0.2$, on the other hand, gives the
right amplitudes, but the changes of $\Tin$ and $\Rin$ are smaller. Although
precise matching is left as future work, we may conclude that the basic
properties of the bursts of GRS 1915+105 can be explained by our ``limit-cycle
oscillation'' model. It is then required that the spectral hardening factor at
high luminosities should be about 3 at around the Eddington luminosity instead
of less than 2 as is usually assumed.


title: Multisite observations of the PMS delta Scuti star V351 Ori

abstract:
  We present the results of multisite observations spanning two years on the
pre--main-sequence (PMS) star V351 Ori. A total of around 180 hours of
observations over 29 nights have been collected, allowing us to measure five
different periodicities, most likely related to the delta
  Scuti variability of V351 Ori. Comparison with the predictions of linear
nonadiabatic radial pulsation models put stringent constraints on the stellar
parameters and indicate that the distance to V351 Ori is intermediate between
the lower limit measured by Hipparcos (210 pc) and that of the Orion Nebula
(450 pc). However, radial pulsation models are unable to reproduce all of the
observed frequencies with a single choice of (M, L, and Te), suggesting the
presence of additional nonradial modes.


title:
An intense and broad FeKalpha line observed in the X-ray luminous quasar
  Q0056-363 with XMM-Newton

abstract:
  We present an XMM-Newton observation of the radio-quiet quasar Q0056-363
(z=0.162). This is the first time that this quasar is observed in the hard
X-ray range (above 2 keV). We find that Q0056-363 is a powerful X-ray quasar,
with a 0.3-12 keV unabsorbed luminosity of about 1.2 x 10^45 erg s-1 with the
largest part (~67%) emitted below 2 keV. The spectrum reveals a large
featureless soft X-ray excess below 2 keV and a strong broad FeKalpha line at
6.4 keV (in the quasar frame). The FeK alpha line is due to low to moderate
ionization states of iron (i.e., < Fe XVII), with an equivalent width of about
250 eV and a velocity width of about 25,000 km s-1. Q0056-363 is presently the
most luminous AGN known to exhibit such a broad and intense FeKalpha line
profile from near neutral iron. The line can be fitted with a relativistic
profile from an accretion disc around either a Schwarzschild (non-rotating) or
a Kerr (rotating) black hole. A combination of two thermal Comptonization
components and a disc reflection model is favored to explain both the continuum
over the energy range 0.3-12 keV and the FeK alpha line. A patchy corona
covering a large part of the inner disc surface is needed in order to be
compatible with the accretion rate inferred from the spectral energy
distribution of Q0056-363, unless the mass of the black hole is much higher
than about 5 x 10^8 M_odot.


title:
Eclipses by circumstellar material in the T Tauri star AA Tau. II.
  Evidence for non-stationary magnetospheric accretion

abstract:
  We report the results of a synoptic study of the photometric and
spectroscopic variability of the classical T Tauri star AA Tau on timescales
ranging from a few hours to several weeks. Emission lines show both infall and
outflow signatures and are well reproduced by magnetospheric accretion models
with moderate mass accretion rates and high inclinations. The veiling shows
variations that indicate the presence of 2 rotationally modulated hot spots
corresponding to the two magnetosphere poles. It correlates well with the HeI
line flux, with B-V and the V excess flux. We have indications of a time delay
between the main emission lines and veiling, the lines formed farther away
preceding the veiling changes. The time delay we measure is consistent with
accreted material propagating downwards the accretion columns at free fall
velocity from a distance of about 8 Rstar. We also report periodic radial
velocity variations of the photospheric spectrum which might point to the
existence of a 0.02 Msun object orbiting the star at a distance of 0.08 AU.
During a few days, the variability of the system was strongly reduced and the
line fluxes and veiling severely depressed. We argue that this episode of
quiescence corresponds to the temporary disruption of the magnetic
configuration at the disk inner edge. The radial velocity variations of inflow
and outflow diagnostics in the Halpha profile yield further evidence for large
scale variations of the magnetic configuration on a timescale of a month. These
results may provide the first clear evidence for large scale instabilities
developping in T Tauri magnetospheres as the magnetic field lines are twisted
by differential rotation between the star and the inner disk.


title:
Constraints on the disk geometry of the T Tauri star AA Tau from linear
  polarimetry

abstract:
  We have simultaneously monitored the photometric and polarimetric variations
of the Classical T Tauri star AA Tau during the fall of 2002. We combine these
data with previously published polarimetric data covering two earlier epochs.
The phase coverage is complete, although not contiguous. AA Tau clearly shows
cyclic variations coupled with the rotation of the system. The star-disk system
produces a repeatable polarisation curve where the polarisation increases with
decreasing brightness. The data fit well with the model put forward by Bouvier
et al. (1999) where AA Tau is viewed almost edge-on and its disk is actively
dumping material onto the central star via magnetospheric accretion. The inner
edge of the disk is deformed by its interaction with the tilted magnetosphere,
producing eclipses as it rotates and occults the photosphere periodically. From
the shape of the polarisation curve in the QU-Plane we confirm that the
accretion disk is seen at a large inclination, almost edge-on, and predict that
its position angle is PA~90 deg., i.e., that the disk's major axis is oriented
in the East-West direction.


title: Magnetically channeled accretion in T Tauri stars : a dynamical process

abstract:
  We review observational evidence and open issues related to the process of
magnetospheric accretion in T Tauri stars. Emphasis is put on recent numerical
simulations and observational results which suggest that the interaction
between the stellar magnetosphere and the inner accretion disk is a highly time
dependent process on timescales ranging from hours to months.


title: The World Space Observatory Project (WSO/UV)

abstract:
  The World Space Observatory Project is a new space mission concept, grown out
the needs of the Astronomical community to have access to the part of the
electromagnetic spectrum where all known physics can be studied on all possible
time scales: the Ultraviolet range. The physical diagnostics in this domain
supply a richness of new experimental data unmatched by any other wavelength
range, for the studies of the Universe. As WSO/UV has been driven by the needs
of scientists from many different countries, a new implementation model was
needed to bring the World Space Observatory to reality. The WSO/UV consists of
a single Ultraviolet Telescope in orbit, incorporating a primary mirror of 1.7
m diameter feeding a UV spectrograph and UV Imagers.