title:
A Possible Shock Wave in the Intergalactic Medium of the Cluster of
  Galaxies A754

abstract:
  The cluster of galaxies A754 undergoes a merger of several large structural
units. X-ray observations show a nonequilibrium state of the central part of
the cluster, in which a cloud of cold plasma 500 kpc in size was identified
amid the hotter cluster gas. The X-ray image of A754 exhibits a brightness
discontinuity, which can be interpreted as a shock wave in front of a moving
cloud of dense gas. The shock parameters are determined from the jump in
intergalactic gas density using the ROSAT image. The estimated Mach number is
M=1.71^{+0.45}_{-0.24} at a 68% confidence level.


title: Modeling stellar populations in cluster galaxies

abstract:
  In this review I highlight the role played by spectrophotometric models in
the study of galaxy evolution in distant clusters. I summarize the main
achievements of the modeling of k+a spectra, the derivation of the star
formation rate in emission line galaxies and the stellar ages of red cluster
galaxies. The current knowledge of the dependence of the star formation
histories on the galaxy morphology and luminosity is also presented.


title:
Peculiar velocities of galaxy clusters: a comparison with the linear
  theory

abstract:
  We investigate peculiar velocities predicted for clusters in Lambda cold dark
matter ($\Lambda$CDM) models assuming that the initial density fluctuation
field is Gaussian. To study the non-linear regime, we use N-body simulations.
We investigate the rms velocity and the probability distribution function of
cluster peculiar velocities for different cluster masses. To identify clusters
in the simulation we use two methods: the standard friends-of-friends (FOF)
method and the method, where the clusters are defined as maxima of a smoothed
density field (DMAX). The density field is smoothed with a top-hat window,
using the smoothing radii $R_s=1.5h^{-1}$ Mpc and $R_s=1.0h^{-1}$ Mpc. The
peculiar velocity of the DMAX clusters is defined to be the mean peculiar
velocity of matter within a sphere of the radius $R_s$. We find that the rms
velocity of the FOF clusters decreases as the cluster mass increases. The rms
velocity of the DMAX clusters is almost independent of the cluster mass and is
well approximated by the linear rms peculiar velocity smoothed at the radius
$R=R_s$. The velocity distribution function of the DMAX clusters is similar to
a Gaussian.


title: WMAP and Supergravity Inflationary Models

abstract:
  We study a class of N=1 Supergravity inflationary models in which the
evolution of the inflaton dynamics is controlled by a single power in the
inflaton field at the point where the observed density fluctuations are
produced, in the context of the braneworld scenario, in light of WMAP results.
In particular, we find that the bounds on the spectral index and its running
constrain the parameter space both for models where the inflationary potential
is dominated by a quadratic term and by a cubic term in the inflaton field. We
also find that $\alpha_s>0$ is required for the quadratic model whereas
$\alpha_s<0 $ for the cubic model. Moreover, we have determined an upper bound
on the five-dimensional Planck scale, $M_5 \lsim 0.019$ M, for the quadratic
model. On the other hand, a running spectral index with $n_s>1$ on large scales
and $n_s<1$ on small scales is not possible in either case.


title:
Secular dynamics of the three body problem: application to the upsilon
  Andromedae planetary system

abstract:
  (abbreviated) We use a semi-numerical approach to study the secular behavior
of a system composed of a central star and two massive planets in eccentric
co-planar orbits. We show that the secular dynamics of this system can be
described using only two parameters, the ratios of the semimajor axes and the
planetary masses. The main dynamical features of the system are presented in
geometrical pictures that allows us to investigate a large domain of the
secular phase space of this three-body problem without time-expensive numerical
integrations of the equations of motion, and without any restriction on the
magnitude of the planetary eccentricities. We show that three different regimes
of secular motion with respect to the secular angle $\Delta\varpi$ are
possible: they are circulation, oscillation (around 0 and $180^\circ$), and
high eccentricity libration in a nonlinear secular resonance. The first two
regimes are a continuous extension of the classical linear secular perturbation
theory; the last is a new feature, hitherto unknown, in the secular dynamics of
the three-body problem.


title:
XMM-Newton and the Pleiades -- I: Bright coronal sources and the X-ray
  emission from intermediate-type stars

abstract:
  We perform X-ray spectral and timing analyses of solar-like (spectral types
F5--K8) and intermediate-type (B4--F4) Pleiads observed in a 40-ks XMM-Newton
EPIC exposure. All 8 solar-like members have ``quasi-steady'' \lx $\ga 10^{29}$
erg/s and 4 exhibit flares. Using a hydrodynamic modelling technique we derive
loop half-lengths ${\cal L} \la 0.5 R_{\star}$ for the two strongest flares, on
HII 1032 and HII 1100. HII 1100's lightcurve suggests a total occultation of
the flaring loop. Eclipse by a substellar companion in a close orbit is
possible but would seem a highly fortuitous event; absorption by a fast-moving
cloud of cool material requires \nh at least two orders of magnitude greater
than any solar or stellar prominence. An occultation may have been mimicked by
the coincidence of two flares, though the first, its decay time shorter than
its rise time and suggestive of ${\cal L} \sim 0.02 R_{\star}$, would be
unusual. Spectral modelling of the quasi-steady emission shows a rising trend
in coronal temperature from F and slowly-rotating G stars through K stars to
fast-rotating G stars, and a preference for low coronal metallicity: features
consistent with those of nearby solar-like stars, although none of the three
stars showing ``saturated'' emission bears the significant component at 2 keV
seen in the saturated coronae of AB Dor and 47 Cas. Of 5 intermediate-type
stars, 2 are undetected (\lx$ < 4 \times 10^{27}$ erg/s) and 3 show X-ray
emission with a spectrum and \lx consistent with origin from an active
solar-like companion.


title: Dust and Nebular Emission. I. Models for Normal Galaxies

abstract:
  We present a model for nebular emission in star forming galaxies, which takes
into account the effects of dust reprocessing. The nebular emissions have been
computed with CLOUDY and then included into GRASIL, our spectrophotometric code
specifically developed for dusty galaxies. The interface between nebular
emission and population synthesis is based on a set of pre-computed HII region
emission models covering a wide range of physical quantities. Concerning the
extinction properties of normal star forming galaxies, we are able to interpret
the observed lack of correlation between the attenuation measured at Halpha and
in the UV band as a consequence of age selective extinction. We also find that,
for these galaxies with modest SFR, the ratio FIR/UV provides the best
constraints on the UV attenuation. Our model also allows to deal with different
SFR estimators in a consistent way, from the UV to radio wavelengths, and to
discuss the uncertainties arising from the different physical conditions
encountered in star forming galaxies. We provide our best estimates of
SFR/luminosity calibrations, together with their expected range of variation.
It results that SFR derived through Halpha, even when corrected for extinction
using the Balmer decrement, is affected by important uncertainties due to age
selective extinction. Another remarkable result is that SFR from UV luminosity
corrected by means of the ratio FIR/UV has a small uncertainty. Finally, our
model provides a calibration of SFR from radio luminosity; we are also able to
reproduce the observed FIR/radio ratio.


title:
A 3-5 micron VLT spectroscopic survey of embedded young low mass stars
  I: Structure of the CO ice

abstract:
  Medium resolution (lambda/Delta lambda = 5000-10000) VLT-ISAAC M-band spectra
are presented of 39 young stellar objects in nearby low-mass star forming
clouds showing the 4.67 micron stretching vibration mode of solid CO. By taking
advantage of the unprecedentedly large sample, high S/N ratio and high spectral
resolution, similarities in the ice profiles from source to source are
identified. It is found that excellent fits to all the spectra can be obtained
using a phenomenological decomposition of the CO stretching vibration profile
at 4.67 micron into 3 components. All observed interstellar CO profiles can
thus be uniquely described by a model depending on only 3 linear fit
parameters, indicating that a maximum of 3 specific molecular environments of
solid CO exist under astrophysical conditions. A simple physical model of the
CO ice is presented, which shows that the 2139.9 cm-1 component is
indistinguishable from pure CO ice. It is concluded, that in the majority of
the observed lines of sight, 60-90% of the CO is in a nearly pure form. In the
same model the 2143.7 cm-1 component can possibly be explained by the
longitudinal optical (LO) component of the vibrational transition in pure
crystalline CO ice which appears when the background source is linearly
polarised. Furthermore the absorption band from solid 13CO at 2092 cm-1 is
detected towards IRS 51 in the Rho Ophiuchi cloud complex and an isotopic ratio
of 12CO/13CO=68+/-10 is derived. It is shown that all the observed solid 12CO
profiles, along with the solid 13CO profile, are consistent with grains with an
irregularly shaped CO ice mantle simulated by a Continuous Distribution of
Ellipsoids (CDE), but inconsistent with the commonly used models of spherical
grains in the Rayleigh limit. [Abstract abridged]


title:
Bayesian joint analysis of cluster weak lensing and Sunyaev-Zel'dovich
  effect data

abstract:
  As the quality of the available galaxy cluster data improves, the models
fitted to these data might be expected to become increasingly complex. Here we
present the Bayesian approach to the problem of cluster data modelling:
starting from simple, physically motivated parameterised functions to describe
the cluster's gas density, gravitational potential and temperature, we explore
the high-dimensional parameter spaces with a Markov-Chain Monte-Carlo sampler,
and compute the Bayesian evidence in order to make probabilistic statements
about the models tested. In this way sufficiently good data will enable the
models to be distinguished, enhancing our astrophysical understanding; in any
case the models may be marginalised over in the correct way when estimating
global, perhaps cosmological, parameters. In this work we apply this
methodology to two sets of simulated interferometric Sunyaev-Zel'dovich effect
and gravitational weak lensing data, corresponding to current and
next-generation telescopes. We calculate the expected precision on the
measurement of the cluster gas fraction from such experiments, and investigate
the effect of the primordial CMB fluctuations on their accuracy. We find that
data from instruments such as AMI, when combined with wide-field ground-based
weak lensing data, should allow both cluster model selection and estimation of
gas fractions to a precision of better than 30 percent for a given cluster.


title:
Kinematics of Ultracompact HII Regions Revealed: High Spectral and
  Spatial Resolution Mapping of the 12.8 micron [NeII] Line in Monoceros R2

abstract:
  We present the first results of a study of the kinematics and morphology of
ultracompact HII regions using a new observational technique. We used very high
spatial (1.5") and spectral (3.4 km/s)resolution observations of the [NeII]
line at 12.8 microns to study the ionized gas in Monoceros R2. The [NeII]
emission shows an HII region with highest emission measure in a ~24" shell.
Line widths are as narrow as 8 km/s at some positions. In places where the
lines are complex and broader, the additional width is most likely due to
overlap of narrower features along the line of sight. The global kinematics
suggest that the 24" shell is expanding at ~10 km/s. However, the spectral
profiles toward the southeast side of the shell are not consistent with a
simple expansion picture.


title:
Probing dark energy perturbations: the dark energy equation of state and
  speed of sound as measured by WMAP

abstract:
  We review the implications of having a non-trivial matter component in the
universe and the potential for detecting such a component through the matter
power spectrum and ISW effect. We adopt a phenomenological approach and
consider the mysterious dark energy to be a cosmic fluid. It is thus fully
characterized, up to linear order, by its equation of state and its speed of
sound. Whereas the equation of state has been widely studied in the literature,
less interest has been devoted to the speed of sound. Its observational
consequences come predominantly from very large scale modes of dark matter
perturbations (k < 0.01 h.Mpc^{-1}). Since these modes have hardly been probed
so far by large scale galaxy surveys, we investigate whether joint constraints
that can be placed on those two quantities using the recent CMB fluctuations
measurements by WMAP as well as the recently measured CMB large scale structure
cross-correlation. We find only a tentative 1$sigma$ detection of the speed of
sound, from CMB alone, c_{s}^{2}<0.04 at this low significance level.
Furthermore, the current uncertainties in bias in the matter power spectrum
preclude any constraints being placed using the cross correlation of CMB with
the NVSS radio survey. We believe however that improvements in bias through
improved survey scales and depths in the near future will improve hopes of
detecting the speed of sound.


title: Scale Invariance without Inflation?

abstract:
  We propose a new alternative mechanism to seed a scale invariant spectrum of
primordial density perturbations that does not rely on inflation. In our
scenario, a perfect fluid dominates the early stages of an expanding,
non-inflating universe. Because the speed of sound of the fluid decays,
perturbations are left frozen behind the sound horizon, with a spectral index
that depends on the fluid equation of state. We explore here a toy model that
realizes this idea. Although the model can explain an adiabatic, Gaussian,
scale invariant spectrum of primordial perturbations, it turns out that in its
simplest form it cannot account for the observed amplitude of the primordial
density perturbations.


title: The Richness-Dependent Cluster Correlation Function: Early SDSS Data

abstract:
  The cluster correlation function and its richness dependence are determined
from 1108 clusters of galaxies -- the largest sample of clusters studied so far
-- found in 379 deg^2 of Sloan Digital Sky Survey early data. The results are
compared with previous samples of optically and X-ray selected clusters. The
richness-dependent correlation function increases monotonically from an average
correlation scale of ~ 12 h^{-1} Mpc for poor clusters to ~ 25 h^{-1} Mpc for
the richer, more massive clusters with a mean separation of ~ 90 h^{-1} Mpc.
X-ray selected clusters suggest slightly stronger correlations than optically
selected clusters (~ 2-\sigma). The results are compared with large-scale
cosmological simulations. The observed richness-dependent cluster correlation
function is well represented by the standard flat LCDM model (\Omega_m ~= 0.3,
h ~= 0.7), and is inconsistent with the considerably weaker correlations
predicted by \Omega_m = 1 models. An analytic relation for the correlation
scale versus cluster mean separation, r_0 - d, that best describes the
observations and the LCDM prediction is r_0 ~= 2.6 \sqrt{d} (for d ~= 20 - 90
h^{-1} Mpc). Data from the complete Sloan Digital Sky Survey, when available,
will greatly enhance the accuracy of the results and allow a more precise
determination of cosmological parameters.


title: The spectroscopic signature of hot Jupiters in FU Orionis objects

abstract:
  We show that if FU Orionis objects harbour hot Jupiters embedded in their
discs, the resulting non-axisymmetric dissipation profile in the disc would be
manifest as time-dependent distortions in the absorption line profiles of these
objects. In order to affect the infrared line profiles, planets must lie within
approximately 0.5 au of the central star, whereas only planets within 0.1 au
would influence the optical line profiles. The timescale for modulation of the
line profiles is relatively short (months) in each case, so that the effect
could not have been discovered from published spectra (which combine data taken
in different observing seasons). The detection of hot Jupiters in FU Orionis
objects would be in line with the expectations of tidal migration theories
(which predict a high incidence of close planets around young stars) and would
also lend support to models which link the triggering of rapid rise FU Orionis
events to the existence of a close massive planet.


title: Large Scale Cosmic Microwave Background Anisotropies and Dark Energy

abstract:
  In this note we investigate the effects of perturbations in a dark energy
component with a constant equation of state on large scale cosmic microwave
background anisotropies. The inclusion of perturbations increases the large
scale power. We investigate more speculative dark energy models with w<-1 and
find the opposite behaviour. Overall the inclusion of perturbations in the dark
energy component increases the degeneracies. We generalise the parameterization
of the dark energy fluctuations to allow for an arbitrary const ant sound
speeds and show how constraints from cosmic microwave background experiments
change if this is included. Combining cosmic microwave background with large
scale structure, Hubble parameter and Supernovae observations we obtain
w=-1.02+-0.16 (1 sigma) as a constraint on the equation of state, which is
almost independent of the sound speed chosen. With the presented analysis we
find no significant constraint on the constant speed of sound of the dark
energy component.


title:
Disk Properties and Density Structure of the Star-Forming Dense Core
  B335

abstract:
  We present subarcsecond resolution dust continuum observations of the
protostellar collapse candidate B335 made with the IRAM Plateau de Bure
Interferometer at wavelengths of 1.2 and 3.0 mm. These observations probe to <
100 AU size scales and reveal a compact source component that we identify with
a circumstellar disk. We analyze these data in concert with previous lower
resolution interferometer observations and find a best fit density structure
for B335 that consists of a power law envelope with index p=1.55 +/- 0.04 (r <
5000 AU) together with a disk (r < 100 AU) of flux F_{1.2 mm}=21 +/-2 mJy. We
estimate a systematic uncertainty in the power law index delta(p) < 0.15, where
the largest error comes from the assumed form of the dust temperature falloff
with radius. This determination of the inner density structure of B335 has a
precision unique amongst protostellar cores, and it is consistent with the
r^{-1.5} profile of gravitational free-fall, in accord with basic expectations
for the formation of a star. The flux (and implied mass) of the compact
component in B335 is typical of the disks around T Tauri stars.


title:
Inner Structure of Starless Core L694--2 Derived from Millimeter-Wave
  Interferometry

abstract:
  We study the density structure of candidate contracting starless core L694-2
using 1.3 mm dust continuum observations from the IRAM Plateau de Bure
Interferometer and the Berkeley-Illinois-Maryland Array, probing spatial scales
from 10000-500 AU. The long baseline PdBI observations detect no emission, and
limit the contamination from a compact component F_c < 2.7 mJy. This limit
corresponds to a very small disk mass, M_disk < 5e-4 M_sun x (60 K / T_disk),
and bolsters the ``starless'' interpretation of the core. The shorter baseline
BIMA data are compared to density models using a physically motivated
temperature distribution with a central minimum. This analysis provides clear
evidence for a turn-over from the steep outer density profile observed in dust
extinction to much more shallow behavior in the inner regions (<7500 AU). The
best fit Bonnor-Ebert, Plummer-like, broken power law, and end-on cylinder
models produce very similar flattened profiles and cannot be distinguished. We
quantify the sensitivity of the inferred structure to various uncertainties,
including the temperature distribution, the central position, and the presence
of a weak unresolved central component. The largest uncertainty comes from the
temperature assumption; an isothermal model modifies the best fit parameters by
\~2 sigma, with the inferred profiles more shallow. Dust emission and
extinction profiles are reproduced by an embedded cylinder with scale height
H=13.5'' inclined at a small angle to the line of sight. The flat central
density profile suggests that pressure forces still support the core, despite
the extended inward motions inferred from molecular line observations (Lee,
Myers, & Tafalla 2001). In the context of the cylindrical density model, these
inward motions may represent the contraction of a prolate core along its major
axis.


title: Planet - Disk Symbiosis

abstract:
  Planets form in disks around young stars. Interactions with these disks cause
them to migrate and thus affect their final orbital periods. We suggest that
the connection between planets and disks may be deeper and involve a symbiotic
evolution. By contributing to the outward transport of angular momentum,
planets promote disk accretion. Here we demonstrate that planets sufficiently
massive to open gaps could be the primary agents driving disk accretion. Those
having masses below the gap opening threshold drift inward more rapidly than
the disk material and can only play a minor role in its accretion. Eccentricity
growth during gap formation may involve an even more intimate symbiosis. Given
a small initial eccentricity, just a fraction of a percent, the orbital
eccentricity of a massive planet may grow rapidly once a mass in excess of the
planet's mass has been repelled to form a gap around the planet's orbit. Then,
as the planet's radial excursions approach the gap's width, subsequent
eccentricity growth slows so that the planet's orbit continues to be confined
within the gap.


title:
Dust in the Early Universe: Dust Formation in the Ejecta of Population
  III Supernovae

abstract:
  We investigate the formation of dust grains in the ejecta of population III
supernovae including pair--instability supernovae, applying a theory of non--
steady state nucleation and grain growth. In the calculations, the time
evolution of gas temperature in theejecta, which strongly affects the number
density and size of newly formed grains, is calculated by solving the radiative
transfer equation taking account of the energy deposition of radio active
elements. Two extreme cases are considered for the mixing of elements in the
ejecta; unmixed and uniformly mixed cases within the He--core.
  The results of calculations are summarized as the followings; in the unmixed
ejecta, a variety of grain species condense, reflecting the difference of the
elemental composition at the formation site in the ejecta, otherwise only oxide
grains condense in the uniformly mixed ejecta. The average size of newly formed
grains spans the range of three orders of magnitude, depending on the grain
species and the formation condition, and the maximum radius is limited to less
than 1 $\mu$m, which does not depend on the progenitor mass. The size
distribution function summed up over all grain species is approximated by a
power--law formula whose index is -3.5 for the larger radius and -2.5 for the
smaller one; the radius at the crossover point ranges from 0.004 to 0.1 $\mu$m,
depending on the model of supernovae. The fraction of mass locked into dust
grains increases with increasing the progenitor mass; 2--5 % of the progenitor
mass for core collapse supernovae and 15--30 % for pair--instability supernovae
whose progenitor mass ranges from 140 to 260 $M_{\odot}$. Thus, if the very
massive stars populate the first generation stars, a large amount of dust
grains would be produced in the early universe.


title:
Magnetorotational instability in weakly ionised, stratified accretion
  discs

abstract:
  The magnetorotational instability (MRI) (Balbus and Hawley 1991, Hawley and
Balbus 1991) transports angular momentum radially outwards in accretion discs
through the distortion of the magnetic field lines that connect fluid elements.
In protostellar discs, low conductivity is important, especially in the inner
regions (Gammie 1996, Wardle 1997). As a result, low k modes are relevant and
vertical stratification is a key factor of the analysis. However, most models
of the MRI in these environments have adopted either the ambipolar diffusion or
resistive approximations and have not simultaneously treated stratification and
Hall conductivity. We present here a linear analysis of the MRI, including the
Hall effect, in a stratified disc.


title:
XMM-Newton observation of the brightest X-ray flare detected so far from
  SgrA*

abstract:
  We report the high S/N observation on October 3, 2002 with XMM-Newton of the
brightest X-ray flare detected so far from SgrA* with a duration shorter than
one hour (~ 2.7 ks). The light curve is almost symmetrical with respect to the
peak flare, and no significant difference between the soft and hard X-ray range
is detected. The overall flare spectrum is well represented by an absorbed
power-law with a soft photon spectral index of Gamma=2.5+/-0.3, and a peak 2-10
keV luminosity of 3.6 (+0.3-0.4) x 10^35 erg/s, i.e. a factor 160 higher than
the Sgr A* quiescent value. No significant spectral change during the flare is
observed. This X-ray flare is very different from other bright flares reported
so far: it is much brighter and softer. The present accurate determination of
the flare characteristics challenge the current interpretation of the physical
processes occuring inside the very close environment of SgrA* by bringing very
strong constraints for the theoretical flare models.


title:
Unusual profile variations in pulsar PSR J1022+1001 -- Evidence for
  magnetospheric "return currents"?

abstract:
  We report a detailed multi-frequency study of significant instabilities
observed in the average pulse profile of the 16-millisecond pulsar PSR
J1022+1001. These unusual profile variations which are seen as a function of
time and of radio frequency are clearly different from classical profile
mode-changing. We also note discrete jumps in the polarisation position angle
curve of this pulsar which are remarkably coincident with the unstable profile
component. We propose that these jumps, as well as the instability of the pulse
profile, are due to magnetospheric return currents. This would allow us to
measure the basic properties of the magnetospheric plasma for the very first
time.


title: Proper motions and velocity asymmetries in the RW Aur jet

abstract:
  We present adaptive optics spectro-imaging observations of the RW Aur jet in
optical forbidden lines, at an angular resolution of 0.4 arcsec. Comparison
with HST data taken 2 years later shows that proper motions in the blueshifted
and redshifted lobes are in the same ratio as their radial velocities, a direct
proof that the velocity asymmetry in this jet is real and not an emissivity
effect. The inferred jet inclination to the line of sight is i = 46 +/- 3
degrees. The inner knot spacing appears best explained by time variability with
at least two modes: one irregular and asymmetric (possibly random) on
timescales of <3-10 yr, and another more regular with ~ 20 yr period. We also
report indirect evidence for correlated velocity and excitation gradients in
the redshifted lobe, possibly related to the blue/red velocity and brightness
asymmetry in this system.


title:
Can the age discrepancies of neutron stars be circumvented by an
  accretion-assisted torque?

abstract:
  It is found that 1E 1207.4-5209 could be a low-mass bare strange star if its
small radius or low altitude cyclotron formation can be identified. The age
problems of five sources could be solved by a fossil-disk-assisted torque. The
magnetic dipole radiation dominates the evolution of PSR B1757-24 at present,
and the others are in propeller (or tracking) phases.


title:
An alpha-stable approach to the study of the P(D) distribution of
  unresolved point sources in CMB sky maps

abstract:
  We present a new approach to the statistical study and modelling of number
counts of faint point sources in astronomical images, i.e. counts of sources
whose flux falls below the detection limit of a survey. The approach is based
on the theory of alpha-stable distributions. We show that the non-Gaussian
distribution of the intensity fluctuations produced by a generic point source
population -- whose number counts follow a simple power law -- belongs to the
alpha-stable family of distributions. Even if source counts do not follow a
simple power law, we show that the alpha-stable model is still useful in many
astrophysical scenarios. With the alpha-stable model it is possible to totally
describe the non-Gaussian distribution with a few parameters which are closely
related to the parameters describing the source counts, instead of an infinite
number of moments. Using statistical tools available in the signal processing
literature, we show how to estimate these parameters in an easy and fast way.
We demonstrate that the model proves valid when applied to realistic point
source number counts at microwave frequencies. In the case of point
extragalactic sources observed at CMB frecuencies, our technique is able to
successfully fitting the P(D) distribution of deflections and to precisely
determining the main parameters which describe the number counts. In the case
of the Planck mission, the relative errors on these parameters are small either
at low and at high frequencies. We provide a way to deal with the presence of
Gaussian noise in the data using the empirical characteristic function of the
P(D). The formalism and methods here presented can be very useful also for
experiments in other frequency ranges, e.g. X-ray or radio Astronomy.


title: Searching for dark matter

abstract:
  The observational evidence for dark matter on progressively larger cosmic
scales is reviewed in a rather pedagogical fashion. Although the emphasis is on
dark matter in galaxies and in clusters of galaxies, its cosmological evidence
as well as its physical nature are also discussed.


title: Advanced pseudo-correlation radiometers for the Planck-LFI instrument

abstract:
  The LFI (Low Frequency Instrument) on board the ESA Planck satellite is
constituted by an array of radiometric detectors actively cooled at 20 K in the
30-70 GHz frequency range in the focal plane of the Planck telescope. In this
paper we present an overview of the LFI instrument, with a particular focus on
the radiometer design. The adopted pseudo-correlation scheme uses a software
balancing technique (with a tunable parameter called gain modulation factor)
which is effective in reducing the radiometer susceptibility to amplifier
instabilities also in presence of small non-idealities in the radiometric chain
components, provided that the gain modulation factor is estimated with an
accuracy of the order of 0.2%. These results have been recently confirmed by
experimental laboratory measurements conducted on the LFI prototype radiometers
at 30, 70 and 100 GHz.


title: CRASH: a Radiative Transfer Scheme

abstract:
  We present a largely improved version of CRASH, a 3-D radiative transfer code
that treats the effects of ionizing radiation propagating through a given
inhomogeneous H/He cosmological density field, on the physical conditions of
the gas. The code, based on a Monte Carlo technique, self-consistently
calculates the time evolution of gas temperature and ionization fractions due
to an arbitrary number of point/extended sources and/or diffuse background
radiation with given spectra. In addition, the effects of diffuse ionizing
radiation following recombinations of ionized atoms have been included. After a
complete description of the numerical scheme, to demonstrate the performances,
accuracy, convergency and robustness of the code we present four different test
cases designed to investigate specific aspects of radiative transfer: (i) pure
hydrogen isothermal Stromgren sphere; (ii) realistic Stromgren spheres; (iii)
multiple overlapping point sources, and (iv) shadowing of background radiation
by an intervening optically thick layer. When possible, detailed quantitative
comparison of the results against either analytical solutions or 1-D standard
photoionization codes has been made showing a good level of agreement. For more
complicated tests the code yields physically plausible results, which could be
eventually checked only by comparison with other similar codes. Finally, we
briefly discuss future possible developments and cosmological applications of
the code.


title:
Predicting the Polarization of The Microwave Background from the WMAP
  Temperature Maps

abstract:
  In this paper, we study how to predict the polarization of the Cosmic
Microwave Background using knowledge of only the temperature (intensity) and
the cross-correlation between temperature and polarization. We derive a
``Wiener prediction'' method and apply it to the WMAP all-sky CMB temperature
maps and to the MAXIMA field.


title: The radial velocity curve of HD153919 (4U1700-37) revisited

abstract:
  We have re-analysed all available high-resolution ultraviolet IUE spectra of
the high-mass X-ray binary HD153919/4U1700-37. The radial velocity
semi-amplitude of 20.6 +/- 1.0 km/s and orbital eccentricity of 0.22 +/- 0.04
agree very well with the values obtained earlier from optical spectra. They
disagree with earlier conclusions for the same data reduced by Heap & Corcoran
(1992) and by Stickland & Lloyd (1993).


title:
The nuclear SED of NGC6251: a BL Lac in the center of an FR I radio
  galaxy

abstract:
  We determine the nuclear spectral energy distribution (SED) from the radio to
the gamma-ray band for the FR I radio galaxy NGC6251, by using both data from
the literature and analyzing HST and X-ray archival data. In the Log nu - Log
nu F(nu) representation, the SED has two broad peaks, and it is remarkably
similar to those of blazars. We show that the low-energy peak can be explained
in terms of synchrotron radiation, while the high energy peak is most plausibly
produced by inverse Compton scattering. This brings direct support to the FR
I-BL Lacs unification model. We model the overall emission in the frame of a
synchrotron self-Compton scenario, which well describes the SED of BL Lacs. The
model parameters we obtain confirm also quantitatively the FR I-BL Lac
unification model and imply a rather small viewing angle to this source (theta
<~ 20deg). NGC6251 is the second radio galaxy, in addition to Centaurus A, for
which a similar analysis has been performed. A significant improvement with
respect to the case of Cen A is the absence of obscuration in NGC6251, which
strengthens the overall result.


title: Magnetic White Dwarfs from the SDSS. The First Data Release

abstract:
  Beyond its goals related to the extragalactic universe, the Sloan Digital Sky
Survey (SDSS) is an effective tool for identifying stellar objects with unusual
spectral energy distributions. Here we report on the 53 new magnetic white
dwarfs discovered during the first two years of the survey, including 38 whose
data are made public in the 1500 square-degree First Data Release. Discoveries
span the magnitude range 16.3 < 20.5, and based on the recovery rate for
previously-known magnetic white dwarfs, the completeness of the SDSS appears to
be high for reasonably hot stars with B > 3 MG and g > 15. The new objects
nearly double the total number of known magnetic white dwarfs, and include
examples with polar field strengths B > 500 MG as well as several with exotic
atmospheric compositions. The improved sample statistics and uniformity
indicate that the distribution of magnetic white dwarfs has a broad peak in the
range ~5-30 MG and a tail extending to nearly 10^9 G. Degenerates with polar
fields B > 50 MG are consistent with being descendents of magnetic Ap/Bp
main-sequence stars, but low- and moderate-field magnetic white dwarfs appear
to imply another origin. Yet-undetected magnetic F-type stars with convective
envelopes that destroy the ordered underlying field are attractive candidates.


title:
Probing the rotation curve of the outer accretion disk in FU Orionis
  objects with long-wavelength spectroscopy

abstract:
  Studies of the Spectral Energy Distribution of Young Stellar Objects suggest
that the outer disk of FU Orionis objects might be self-gravitating. In this
paper we propose a method to test directly whether, in these objects,
significant deviations from Keplerian rotation occur. In a first approach, we
have used a simplified model of the disk vertical structure that allows us to
quickly bring out effects related to the disk self-gravity. We find that the
often studied optical and near-infrared line profiles are produced too close to
the central object to provide significant evidence for non-Keplerian rotation.
Based on parameters relevant for the case of FU Ori, we show that
high-resolution long-wavelength spectroscopy, of the far-infrared H$_2$ pure
rotational lines (sometimes observed in ``passive'' protostellar disks) and
sub-mm CO lines, should be well suited to probe the rotation curve in the outer
disk, thus measuring to what extent it is affected by the disk self-gravity.
The results of the present exploratory paper should be extended soon to a more
realistic treatment of the disk vertical structure.


title:
Quasi-periodic X-ray brightness fluctuations in an accreting millisecond
  pulsar

abstract:
  The relativistic plasma flows onto neutron stars that are accreting material
from stellar companions can be used to probe strong-field gravity as well as
the physical conditions in the supranuclear-density interiors of neutron stars.
Plasma inhomogeneities orbiting a few kilometres above the stars are observable
as X-ray brightness fluctuations on the millisecond dynamical timescale of the
flows. Two frequencies in the kilohertz range dominate these fluctuations: the
twin kilohertz quasi-periodic oscillations (kHz QPOs). Competing models for the
origins of these oscillations (based on orbital motions) all predict that they
should be related to the stellar spin frequency, but tests have been difficult
because the spins were not unambiguously known. Here we report the detection of
kHz QPOs from a pulsar whose spin frequency is known. Our measurements
establish a clear link between kHz QPOs and stellar spin, but one not predicted
by any current model. A new approach to understanding kHz QPOs is now required.
We suggest that a resonance between the spin and general relativistic orbital
and epicyclic frequencies could provide the observed relation between QPOs and
spin.


title: The Environment of AGNs in the Sloan Digital Sky Survey

abstract:
  We present the observed fraction of galaxies with an Active Galactic Nucleus
(AGN) as a function of environment in the Early Data Release of the Sloan
Digital Sky Survey (SDSS). Using 4921 galaxies between 0.05 <= z <= 0.095, and
brighter than M_r* = -20.0 (or M* +1.45), we find at least ~ 20% of these
galaxies possess an unambiguous detection of an AGN, but this fraction could be
as high as ~40% after we model the ambiguous emission line galaxies in our
sample. We have studied the environmental dependence of galaxies using the the
distance to the 10^th nearest neighbor. As expected, we observe that the
fraction of star--forming galaxies decreases with density, while the fraction
of passive galaxies increases with density. In contrast, the fraction of
galaxies with an AGN remains constant from the cores of galaxy clusters to the
rarefied field population. We conclude that the presence of an AGN is
independent of the disk component of a galaxy. Our analyses are robust against
measurement error, definition of an AGN, aperture bias, stellar absorption,
survey geometry and signal--to--noise. Our observations are consistent with the
hypothesis that a supermassive black hole resides in the bulge of all massive
galaxies and ~40% of these black holes are seen as AGNs in our sample. A high
fraction of local galaxies with an AGN suggests that either the mean lifetime
of these AGNs is longer than previously thought (>10^8 years), or that the AGN
burst more often than expected; ~40 times over the redshift range of our
sample.


title: Low Mass X-ray Binaries and Globular Clusters in Early-Type Galaxies

abstract:
  (Abridged) A high fraction of the Low Mass X-ray Binaries (LMXBs) in
early-type galaxies are associated with globular clusters (GCs). Here, we
discuss the correlations between LMXBs and GCs in a sample of four early-type
galaxies. There is some evidence that the fraction of LMXBs associated with GCs
(f_X-GC) increases along the Hubble sequence from spiral bulges to S0s to Es to
cDs. On the other hand, the fraction of globular clusters which contain X-ray
sources appears to be roughly constant at f_GC-X ~ 4%. There is a strong
tendency for the X-ray sources to be associated with the optically more
luminous GCs. However, this correlation is consistent with a constant
probability of finding a LMXB per unit optical luminosity; it seems to result
primarily from the larger number of stars in optically luminous GCs. The
probability of finding a bright LMXB per unit optical luminosity in the GCs is
about 1.5e-7 LMXBs per L_solar,I for L_X >~ 1e38 erg/s, and rises to about
2.0e-7 LMXBs per L_solar,I at lower X-ray luminosities, L_X >~ 3e37 erg/s. This
frequency appears to be roughly constant for different galaxies, including the
bulges of the Milky Way and M31. There is a tendency for the X-ray sources to
be found preferentially in redder GCs. This seems to indicate that the
evolution of X-ray binaries in a GC is affected either by the metallicity or
age of the GC, with younger and/or more metal rich GCs having more LMXBs. There
is a weak tendency for the brightest LMXBs, whose luminosities exceed the
Eddington luminosity for a 1.4 M_solar neutron star, to avoid GCs. That may
indicate that black hole X-ray are somewhat less likely to be found in GCs, as
seems to be true in our Galaxy.


title: On Heavy Element Enrichment in Classical Novae

abstract:
  Many classical nova ejecta are enriched in CNO and Ne. Rosner et al. recently
suggested that the enrichment might originate in the resonant interaction
between large-scale shear flows in the accreted H/He envelope and gravity waves
at the interface between the envelope and the underlying C/O white dwarf. The
shear flow amplifies the waves, which eventually form cusps and break. This
wave breaking injects a spray of C/O into the superincumbent H/He. Using
two-dimensional simulations, we formulate a quantitative expression for the
amount of C/O per unit area that can be entrained into the H/He at saturation.
The fraction of the envelope that is enriched depends on the horizontal
distribution of shear velocity and the density contrast between the C/O white
dwarf and the H/He layer but is roughly independent of the vertical shape of
the shear profile. Using this parameterization for the mixed mass, we then
perform several one-dimensional Lagrangian calculations of an accreting white
dwarf envelope and consider two scenarios: that the wave breaking and mixing is
driven by the convective flows; and that the mixing occurs prior to the onset
of convection. In the absence of enrichment prior to ignition, the base of the
convective zone, as calculated from mixing-length theory with the Ledoux
instability criterion, does not reach the C/O interface. As a result, there is
no additional mixing, and the runaway is slow. In contrast, the formation of a
mixed layer during the accretion of H/He, prior to ignition, causes a more
violent runaway. The envelope can be enriched by <25% of C/O by mass
(consistent with that observed in some ejecta) for shear velocities, over the
surface, with Mach numbers <0.4.


title: A Massive X-Ray Outflow from the Quasar PDS 456

abstract:
  We report on XMM-Newton spectroscopic observations of the luminous,
radio-quiet quasar PDS 456. The hard X-ray spectrum of PDS 456 shows a deep
absorption trough (constituting 50% of the continuum) at energies above 7 keV
in the quasar rest frame, which can be attributed to a series of blue-shifted
K-shell absorption edges due to highly ionized iron. The higher resolution soft
X-ray RGS spectrum exhibits a broad absorption line feature near 1 keV, which
can be modeled by a blend of L-shell transitions from highly ionized iron (Fe
XVII-XXIV). An extreme outflow velocity of 50000 km/s is required to model the
K and L shell iron absorption present in the XMM-Newton data. Overall, a large
column density ($N_{H}=5\times10^{23}$cm$^{-2}$) of highly ionized gas
(logxi=2.5) is required in PDS 456. A high mass outflow rate of 10 solar masses
per year (assuming a conservative outflow covering factor of 0.1 steradian) is
derived, which is of the same order as the overall mass accretion rate in PDS
456. The kinetic energy of the outflow represents a substantial fraction (10%)
of the quasar energy budget, whilst the large column and outflow velocity place
PDS 456 towards the extreme end of the broad absorption line quasar population.


title:
The Age of the Oldest Stars in the Local Galactic Disk From Hipparcos
  Parallaxes of G and K Subgiants

abstract:
  We review the history of the discovery of field subgiant stars and their
importance in the age dating of the Galactic disk. We use the cataloged data
from the Hipparcos satellite in this latter capacity. Based on Hipparcos
parallaxes accurate to 10% or better, the absolute magnitude of the lower
envelope of the nearly horizontal subgiant sequence for field stars in the H-R
diagram for B-V colors between 0.85 and 1.05 is measured to be M_V = 4.03 +/-
0.06. The age of the field stars in the solar neighborhood is found to be 7.9
+/- 0.7 Gyr by fitting the theoretical isochrones for [Fe/H] = +0.37 to the
lower envelope of the Hipparcos subgiants. The same grid of isochrones yields
ages, in turn, of 4.0 +/- 0.2 Gyr, 6.2 +/- 0.5 Gyr, and 7.5 to 10 Gyr for the
old Galactic clusters M67, NGC188, and NGC6791. The ages of both the Galactic
disk in the solar neighborhood and of NGC6791 are, nevertheless, likely between
3 and 5 Gyr younger than the oldest halo globular clusters, which have ages of
13.5 Gyr. The most significant results are (1) the supermetallicity of the
oldest local disk stars, and (2) the large age difference between the most
metal-poor component of the halo and the thick and thin disk in the solar
neighborhood. These facts are undoubtedly related and pose again the problem of
the proper scenario for the timing of events in the formation of the halo and
the Galactic disk in the solar neighborhood. [Abstract Abridged]


title: Absolute Branching Ratio of Beta-Delayed Gamma-Ray Emission of N18

abstract:
  The absolute branching ratio of the beta-delayed gamma-ray emission of N18
was measured, providing absolute normalization of the previous work by Olness
et al. [J.W. Olness et al., Nuc. Phys. A373, 13 (1982)] who measured the
relative branching ratios for the individual gamma-rays. We find the total
absolute branching ratio for beta-delayed gamma emission of N18 to be 76.7 +/-
7.2(stat) +/- 5.8(norm)%. A combination of other results suggests a value
consistent with our result, but smaller than that calculated by Millener as
quoted in Olness et al.


title: Gauge Freedom in the N-body problem of Celestial Mechanics

abstract:
  We summarise research reported in (Efroimsky 2002, 2003; Efroimsky and
Goldreich 2003a,b) and develop its application to planetary equations in
non-inertial frames.
  We provide a practical example illustrating how the gauge formalism
considerably simplifies the calculation of satellite motion about an oblate
precessing planet.


title: The Local Group as an Astrophysical Laboratory for Massive Star Feedback

abstract:
  The feedback effects of massive stars on their galactic and intergalactic
environments can dominate evolutionary processes in galaxies and affect cosmic
structure in the Universe. Only the Local Group offers the spatial resolution
to quantitatively study feedback processes on a variety of scales. Lyman
continuum radiation from hot, luminous stars ionizes HII regions and is
believed to dominate production of the warm component of the interstellar
medium (ISM). Some of this radiation apparently escapes from galaxies into the
intergalactic environment. Supernovae and strong stellar winds generate shell
structures such as supernova remnants, stellar wind bubbles, and superbubbles
around OB associations. Hot (10^6 K) gas is generated within these shells, and
is believed to be the origin of the hot component of the ISM. Superbubble
activity thus is likely to dominate the ISM structure, kinematics, and phase
balance in star-forming galaxies. Galactic superwinds in starburst galaxies
enable the escape of mass, ionizing radiation, and heavy elements. Although
many important issues remain to be resolved, there is little doubt that
feedback processes plays a fundamental role in energy cycles on scales ranging
from individual stars to cosmic structure. This contribution reviews studies of
radiative and mechanical feedback in the Local Group.


title:
Relativistic equilibrium velocity distribution, nuclear fusion reaction
  rate and the solar neutrino problem

abstract:
  In solar interior, it is the equilibrium velocity distribution of few
high-energy protons and nuclei that participates in determining nuclear fusion
reaction rates. So, it is inappropriate to use the Maxwellian velocity
distribution to calculate the rates of solar nuclear fusion reactions. We have
to use the relativistic equilibrium velocity distribution for the purpose. The
nuclear fusion reaction rate based on the relativistic equilibrium velocity
distribution has a reduction factor with respect to that based on the
Maxwellian distribution. The reduction factor depends on the temperature,
reduced mass and atomic numbers of the studied nuclear fusion reactions, in
other words, it varies with the sort of neutrinos. Substituting the
relativistic equilibrium velocity distribution for the Maxwellian distribution
is not important for the calculation of solar sound speeds. The relativistic
equilibrium velocity distribution, if adopted in standard solar models, will
lower solar neutrino fluxes and change solar neutrino energy spectra but
maintain solar sound speeds. This velocity distribution is possibly a solution
to the solar neutrino problem.


title: Origin and evolution of neutron star magnetic fields

abstract:
  This paper intends to give a broad overview of the present knowledge about
neutron star magnetic fields, their origin and evolution. An up-to-date
overview of the rich phenomenology (encompassing ``classical'' and millisecond
radio pulsars, X-ray binaries, ``magnetars'', and ``thermal emitters'')
suggests that magnetic fields on neutron stars span at least the range
$10^{8-15}$ G, corresponding to a range of magnetic fluxes similar to that
found in white dwarfs and upper main sequence stars. The limitations of the
observational determinations of the field strength and evidence for its
evolution are discussed. Speculative ideas about the possible main-sequence
origin of the field (``magnetic strip-tease'') are presented. Attention is also
given to physical processes potentially leading to magnetic field evolution.


title: The magnetic stress tensor in magnetized matter

abstract:
  We derive the form of the magnetic stress tensor in a completely general,
stationary magnetic medium, with an arbitrary magnetization field $\vec M(\vec
r)$ and free current density $\vec j(\vec r)$. We start with the magnetic force
density $\vec f$ acting on a matter element, modelled as a collection of
microscopic magnetic dipoles in addition to the free currents. We show that
there is a unique tensor ${\bf T}$ quadratic in the magnetic flux density $\vec
B(\vec r)$ and the magnetic field $\vec H(\vec r)=\vec B-4\pi\vec M$ whose
divergence is $\nabla\cdot{\bf T}=\vec f$. In the limit $\vec M=0$, the
well-known vacuum magnetic stress tensor is recovered. However, the general
form of the tensor is asymmetric, leading to a divergent angular acceleration
for matter elements of vanishing size. We argue that this is not inconsistent,
because it occurs only if $\vec M$ and $\vec B$ are not parallel, in which case
the macroscopic field does indeed exert a torque on each of the microscopic
dipoles, so this state is only possible if there are material stresses which
keep the dipoles aligned with each other and misaligned with the macroscopic
field. We briefly discuss the consequences for the stability of strongly
magnetized stars.


title: Fossil HII Regions: Self-Limiting Star Formation at High Redshift

abstract:
  Recent results by the WMAP satellite suggest that the intergalactic medium
was significantly reionized at redshifts as high as z~17. At this early epoch,
the first ionizing sources likely appeared in the shallow potential wells of
mini-halos with virial temperatures T < 10^4 K. Once such an ionizing source
turns off, its surrounding HII region Compton cools and recombines.
Nonetheless, we show that the ``fossil'' HII regions left behind remain at high
adiabats, prohibiting gas accretion and cooling in subsequent generations of
mini-halos. Thus, early star formation is self-limiting. We quantify this
effect to show that star formation in mini-halos cannot account for the bulk of
the electron scattering opacity measured by WMAP, which must be due to more
massive objects. We argue that gas entropy, rather than IGM metallicity,
regulates the evolution of the global ionizing emissivity, and impedes full
reionization until lower redshifts. We discuss several important consequences
of this early entropy floor for reionization. It reduces gas clumping,
curtailing the required photon budget for reionization. An entropy floor also
prevents H2 formation and cooling, due to reduced gas densities: it greatly
enhances feedback from UV photodissociation of H2. An early X-ray background
would also furnish an entropy floor to the entire IGM; thus, X-rays impede
rather than enhance H2 formation. Future 21cm observations may probe the
topology of fossil HII regions.


title:
Optical Photometry and Spectroscopy of the SN 1998bw-like Type Ic
  Supernova 2002ap

abstract:
  We present optical photometric and spectral data of the peculiar Type Ic SN
2002ap. Photometric coverage includes UBVRI bands from 2002 January 30, the day
after discovery, through 2002 December 12. There are 5 early-time spectra and 8
in the nebular phase. We determine that SN 2002ap is similar to SN 1997ef and
the GRB-associated SN 1998bw with respect to spectral and photometric
characteristics. The nebular spectra of SN 2002ap present the largest Mg I]
\lambda 4571 to [O I] \lambda \lambda 6300, 6364 ratio of any supernova spectra
yet published, suggesting that the progenitor of SN 2002ap was a highly
stripped star. Comparing the nebular spectra of SN 1985F and SN 2002ap, we
notice several similar features, casting the classification of SN 1985F as a
normal Type Ib supernova in doubt. We also present nebular modeling of SN
2002ap and find that the object ejected >~ 1.5 M_{sun} of material within the
outer velocity shell of the nebula (~5500 km/s) and synthesized ~0.09 M_{sun}
of 56Ni.


title: LINERs and their Physical Mechanisms

abstract:
  I review the basic properties of low-ionization nuclear emission-line regions
(LINERs), as well as the main ionization mechanisms thus far proposed for them.
There is substantial heterogeneity among LINERs, especially those with extended
kpc-scale emission. An extensive survey by Ho, Filippenko, & Sargent quantifies
with unprecedented accuracy the optical emission-line intensity ratios in the
nuclei of a complete sample of 486 nearby, bright galaxies. Over 40% of all
early-type galaxies in the sample can be classified as LINERs or LINER/H II
transition objects. A nonstellar continuum is detected in many LINERs,
suggesting that they are genuine AGNs powered by accretion onto a compact
object. Broad H alpha emission similar to that of Seyfert 1 nuclei is seen in
many LINERs. In some LINERs, the broad H alpha emission has two well-separated
peaks, probably indicative of an accretion disk.


title: Optical Spectra and Light Curves of Supernovae

abstract:
  I review recent optical observations of supernovae (SNe) conducted by my
group. The Lick Observatory Supernova Search with the 0.76-m Katzman Automatic
Imaging Telescope is currently the world's most successful search for nearby
SNe. We also use this telescope to obtain multicolor light curves of SNe. One
of the more interesting SNe we discovered is SN 2000cx, which differs from all
previously observed SNe Ia. Another very strange SN Ia that we studied is SN
2002cx, many of whose properties are opposite those of SN 2000cx. Extensive
data on SNe II-P 1999em and 1999gi were used to derive distances with the
expanding photosphere method. Results from spectropolarimetry suggest that the
deeper we peer into the ejecta of core-collapse SNe, the greater the
asphericity. We are using Hubble Space Telescope data to identify, or set
limits on, the progenitors of core-collapse SNe.


title:
Evidence from Type Ia Supernovae for an Accelerating Universe and Dark
  Energy

abstract:
  I review the use of Type Ia supernovae (SNe Ia) for cosmological distance
determinations. Low-redshift SNe Ia (z <~ 0.1) demonstrate that the Hubble
expansion is linear, that H_0 = 65 +/- 2 (statistical) km/s/Mpc, and that the
properties of dust in other galaxies are similar to those of dust in the Milky
Way. The light curves of high-redshift (z = 0.3 - 1) SNe Ia are stretched in a
manner consistent with the expansion of space; similarly, their spectra exhibit
slower temporal evolution (by a factor of 1 + z) than those of nearby SNe Ia.
The measured luminosity distances of SNe Ia as a function of redshift have
shown that the expansion of the Universe is currently accelerating, probably
due to the presence of repulsive dark energy such as Einstein's cosmological
constant (\Lambda). Combining our data with existing measurements of the cosmic
microwave background (CMB) radiation and with the results of large-scale
structure surveys, we find a best fit for \Omega_m and \Omega_\Lambda of about
0.3 and 0.7, respectively. Other studies (e.g., masses of clusters of galaxies)
also suggest that \Omega_m \approx 0.3. The sum of the densities, ~1.0, agrees
with the value predicted by most inflationary models for the early Universe:
the Universe is flat on large scales. A number of possible systematic effects
(dust, supernova evolution) thus far do not seem to eliminate the need for
\Omega_\Lambda > 0. Most recently, analyses of SNe Ia at z = 1.0 - 1.7 provide
further support for current acceleration, and give tentative evidence for an
early epoch of deceleration. Current projects include the search for additional
SNe Ia at z > 1 to confirm the early deceleration, and the measurement of a few
hundred SNeIa at z = 0.2 - 0.8 to determine the equation of state of the dark
energy, w = P/(\rho c^2).


title: Theory of the quantification of the redshifts

abstract:
  The quantification of the redshifts of the lines observed in the spectra of
the quasars and the galaxies (the redshifts of their lines have some of the
values given by the formula z=a+0.062m where a depends on the object, and m is
an integer), the density of the lines, result from a purely spectroscopic
effect. The explanation requires only standard spectroscopy, a nearly
homogeneous halo of atomic hydrogen, and a magnetic field.


title: The scaling relations of galaxy clusters and their dark matter halos

abstract:
  Like early-type galaxies, also nearby galaxy clusters define a Fundamental
Plane, a luminosity-radius, and a luminosity-velocity dispersion relations,
whose physical origin is still unclear. By means of high resolution N--body
simulations of massive dark matter halos in a Lambda-CDM cosmology, we find
that scaling relations similar to those observed for galaxy clusters are
already defined by their dark matter hosts. The slopes however are not the
same, and among the various possibilities in principle able to bring the
simulated and the observed scaling relations in mutual agreement, we show that
the preferred solution is a luminosity dependent mass-to-light ratio (M/L ~
L^0.3), that well corresponds to what inferred observationally. We then show
that at galactic scales there is a conflict between the cosmological
predictions of structure formation, the observed trend of the mass-to-light
ratio in ellipticals, and the slope of their luminosity-velocity dispersion
relation (that significantly differs from the analogous one followed by
clusters). The conclusion is that the scaling laws of elliptical galaxies might
be the combined result of the cosmological collapse of density fluctuations at
the epoch when galactic scales became non-linear, plus important modifications
afterward due to early-time dissipative merging. Finally, we briefly discuss
the possible evolution of the cluster scaling relations with redshift.


title:
An XMM-Newton and Chandra investigation of the nuclear accretion in the
  Sombrero Galaxy (NGC4594)

abstract:
  We present an analysis of the XMM-Newton and Chandra ACIS-S observations of
the LINER nucleus of the Sombrero galaxy and we discuss possible explanations
for its very sub-Eddington luminosity by complementing the X-ray results with
high angular resolution observations in other bands. The X-ray investigation
shows a hard (Gamma=1.89) and moderately absorbed (N_H=1.8 10^21 cm^-2) nuclear
source of 1.5 10^40 erg s^-1 in the 2-10 keV band, surrounded by hot gas at a
temperature of \sim 0.6 keV. The bolometric nuclear luminosity is at least \sim
200 times lower than expected if mass accreted on the supermassive black hole,
that HST shows to reside at the center of this galaxy, at the rate predicted by
the spherical and adiabatic Bondi accretion theory and with the high radiative
efficiency of a standard accretion disc. The low luminosity, coupled to the
observed absence of Fe-K emission in the nuclear spectrum, indicates that such
a disc is not present. This nucleus differs from bright unobscured AGNs also
for the lack of high flux variability and of prominent broad Halpha emission.
However, it is also too faint for the predictions of simple radiatively
inefficient accretion taking place at the Bondi rate; it could be too radio
bright, instead, for radiatively inefficient accretion that includes strong
mass outflows or convection. This discrepancy could be solved by the possible
presence of nuclear radio jets. An alternative explanation of the low
luminosity, in place of radiative inefficiency, could be unsteady accretion.


title: The origin of the iron lines in NGC 7213

abstract:
  The analysis of a simultaneous XMM-Newton/BeppoSAX plus three previous
BeppoSAX observations revealed that NGC 7213 is a rather peculiar Seyfert 1. No
significant Compton reflection component was observed, while an iron line
complex, best explained in terms of three narrow lines, is clearly apparent in
the data. Due to the absence of the reflection component, the neutral iron line
is likely not produced in a Compton-thick material, but current data do not
allow to choose between a Compton-thin torus and the BLR. The two ionized iron
lines from \ion{Fe}{xxv} and \ion{Fe}{xxvi} may be produced in a photoionized
gas with a column density of a few 10$^{23}$ cm$^{-2}$, in analogy with the
case of NGC 5506.


title: The DA+dMe eclipsing binary EC13471-1258: its cup runneth over...just

abstract:
  EC13471-1258 is a detached eclipsing binary with Porb = 3h37m, comprising a
DA white dwarf and a dMe dwarf. Total eclipses of the white dwarf lasting 14
min, and a large amplitude ellipsoidal variation are seen in the light curve.
Flares from the dMe star occur regularly. Each star contributes roughly equal
amounts of light at 5500 Ang.
  HST STIS spectra show strong Ly alpha with weak metal lines, and yield Teff =
14220 K, log g = 8.34, Z = 1/30th solar, K = 138 km/s and V sin i = 400 km/s
for the white dwarf. Optical spectra yield the spectral type (M3.5-4.0), Teff =
3100 K, Z = solar, K = 266 km/s and V sin i = 140 km/s for the dMe star. The H
alpha emission line comprises 2 or more components and implies that very weak
mass transfer is occurring. The dynamical solution also implies that the dMe
star just fills its Roche lobe. Accurate masses and radii for each star were
derived: the dMe values favour the Clemens et al. (1998) mass-radius relation.
The large rotational velocity of the white dwarf (400 km/s) suggests that the
system has transferred mass in the past so that it is presently a hibernating
cataclysmic variable. The metallicity contrast between the component stars
provides an opportunity for tests of diffusion theory.


title:
A Quest for PMS candidate stars at low metallicity: Variable HAe/Be and
  Be stars in the Small Magellanic Cloud

abstract:
  We report the discovery of 5 new Herbig Ae/Be candidate stars in the Small
Magellanic Cloud in addition to the 2 reported in Beaulieu et al. (2001). We
discuss these 7 HAeBe candidate stars in terms of (1) their irregular
photometric variability, (2) their near infrared emission, (3) their Halpha
emission and (4) their spectral type. One star has the typical photometric
behaviour that is observed only among Pre-Main Sequence UX Orionis type stars.
The objects are more luminous than Galactic HAeBe stars and Large Magellanic
Cloud HAeBe candidates of the same spectral type. The stars were discovered in
a systematic search for variable stars in a subset of the EROS2 database
consisting of 115,612 stars in a field of 24x24 arcmin in the Small Magellanic
Cloud. In total we discovered 504 variable stars. After classifying the
different objects according to their type of variability, we concentrate on 7
blue objects with irregular photometric behaviour. We cross-identified these
objects with emission line catalogues from Simbad and JHK photometry from
2MASS. The analysis is supplemented with obtained narrow and broad band
imaging. We discuss their variability in terms of dust obscuration and
bound-free and free-free emission. We estimate the influence of metallicity on
the circumstellar dust emission from pre-main sequence stars.


title: The Chemistry of Galaxy Clusters

abstract:
  From X-ray observations of galaxy clusters one derives the mass of the
intracluster medium along with its chemical composition. Optical/infrared
observations are used to estimate the mass of the stellar components of
galaxies, along with their chemical composition and age. This review shows that
when combining all this information, several interesting inferences can be
drawn, including: (1) galaxies lose more metals than they retain; (2) clusters
and the general field have converted the same fraction of baryons into stars,
hence the metallicity of the $z = 0$ Universe as a whole has to be nearly the
same we see in clusters, $\sim$1/3 solar; (3) for the same reason, the thermal
content of the intergalactic medium is expected to be nearly the same as the
preheating energy of clusters; (4) a strong increase of the Type Ia supernova
(SN) rate with lookback time is predicted if SNe Ia produce a major fraction of
cosmic iron; (5) the global metallicity of the $z\approx 3$ Universe was
already $\sim$1/10 solar; and (6) the Milky Way disk formed out of material
that was pre-enriched to $\sim$1/10 solar by the bulge stellar population.


title:
Integral-field spectroscopy of the quadruple QSO HE 0435-1223: Evidence
  for microlensing

abstract:
  We present the first spatially resolved spectroscopic observations of the
recently discovered quadruple QSO and gravitational lens HE0435-1223. Using the
Potsdam Multi-Aperture Spectrophotometer (PMAS), we show that all four QSO
components have very similar but not identical spectra. In particular, the
spectral slopes of components A, B, and D are indistinguishable, implying that
extinction due to dust plays no major role in the lensing galaxy. While also
the emission line profiles are identical within the error bars, as expected
from lensing, the equivalent widths show significant differences between
components. Most likely, microlensing is responsible for this phenomenon. This
is also consistent with the fact that component D, which shows the highest
relative continuum level, has brightened by 0.07 mag since Dec 2001. We find
that the emission line flux ratios between the components are in better
agreement with simple lens models than broad band or continuum measurements,
but that the discrepancies between model and data are still unacceptably large.
Finally, we present a detection of the lensing galaxy, although this is close
to the limits of the data. Comparing with a model galaxy spectrum, we obtain a
redshift estimate of z_lens=0.44+-0.02.


title:
Contributions of point extragalactic sources to the Cosmic Microwave
  Background bispectrum

abstract:
  All the analyses of Cosmic Microwave Background (CMB) temperature maps
up--to--date show that CMB anisotropies follow a Gaussian distribution. On the
other hand, astrophysical foregrounds which hamper the detection of the CMB
angular power spectrum, are not Gaussian distributed on the sky. Therefore,
they should give a sizeable contribution to the CMB bispectrum. In fact, the
first year data of the Wilkinson Microwave Anisotropy Probe (WMAP) mission have
allowed the {\it first} detection of the extragalactic source contribution to
the CMB bispectrum at 41 GHz and, at the same time, much tighter limits than
before to non--Gaussian primordial fluctuations. In view of the above and for
achieving higher precision in current and future CMB measurements of
non--Gaussianity, in this paper we discuss a comprehensive assessment of the
bispectrum due to either uncorrelated and clustered extragalactic point sources
in the whole frequency interval around the CMB intensity peak. Our
calculations, based on current cosmological evolution models for sources, show
that the reduced angular bispectrum due to point sources, $b_{ps}$, should be
detectable in all WMAP and Planck frequency channels. We also find agreement
with the results on $b_{ps}$ at 41 GHz coming from the analysis of the first
year WMAP data. Moreover, by comparing $b_{ps}$ with the primordial reduced CMB
bispectrum, we find that only the peak value of the primordial bispectrum
(which appears at $l\simeq 200$) results greater than $b_{ps}$ in a frequency
window around the intensity peak of the CMB. The amplitude of this window
basically depends on the capability of the source detection algorithms (i.e.,
on the achievable flux detection limit, $S_{lim}$, for sources).


title:
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass
  Density of the Universe from z=0 to z=3

abstract:
  We present the evolution of the rest-frame optical luminosity density, of the
integrated rest-frame optical color, and of the stellar mass density for a
sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity
density in the rest-frame U, B, and V-bands and found that the luminosity
density increases by a factor of 1.9+-0.4, 2.9+-0.6, and 4.9+-1.0 in the V, B,
and U rest-frame bands respectively between a redshift of 0.1 and 3.2. We
derived the luminosity weighted mean cosmic (U-B)_rest and (B-V)_rest colors as
a function of redshift. The colors bluen almost monotonically with increasing
redshift; at z=0.1, the (U-B)_rest and (B-V)_rest colors are 0.16 and 0.75
respectively, while at z=2.8 they are -0.39 and 0.29 respectively. We derived
the luminosity weighted mean M/LV using the correlation between (U-V)_rest and
log_{10} M/LV which exists for a range in smooth SFHs and moderate extinctions.
We have shown that the mean of individual M/LV estimates can overpredict the
true value by ~70% while our method overpredicts the true values by only ~35%.
We find that the universe at z~3 had ~10 times lower stellar mass density than
it does today in galaxies with LV>1.4 \times 10^{10} h_{70}^-2 Lsol. 50% of the
stellar mass of the universe was formed by $z~1-1.5. The rate of increase in
the stellar mass density with decreasing redshift is similar to but above that
for independent estimates from the HDF-N, but is slightly less than that
predicted by the integral of the SFR(z) curve.


title: X-ray Surveys of Low-redshift Clusters

abstract:
  The selection of clusters of galaxies through their X-ray emission has proved
to be an extremely powerful technique over the past four decades. The growth of
X-ray astronomy has provided the community with a steadily more detailed view
of the intracluster medium in clusters. In this review I will assess how far
X-ray surveys of clusters have progressed and how far they still have to
travel.


title: Identifying Compact Symmetric Objects in the Southern Sky

abstract:
  We present results of multifrequency polarimetric VLBA observations of 20
compact radio sources. The observations represent the northern and southern
extensions of a large survey undertaken to identify Compact Symmetric Objects
(CSOs) Observed in the Northern Sky (COINS). CSOs are young radio galaxies
whose jet axes lie close to the plane of the sky, and whose appearance is
therefore not dominated by relativistic beaming effects. The small linear sizes
of CSOs make them valuable for studies of both the evolution of radio galaxies
and testing unified schemes for active galactic nuclei (AGN). In this paper we
report on observations made of 20 new CSO candidates discovered in the northern
and southern extremities of the VLBA Calibrator Survey. We identify 4 new CSOs,
and discard 12 core-jet sources. The remaining 4 sources remain candidates
pending further investigation. We present continuum images at 5 GHz and 15 GHz
and, where relevant, images of the polarized flux density and spectral index
distributions for the 8 new CSOs and CSO candidates.


title: Large Scale Simulations of Jets in Dense and Magnetised Environments

abstract:
  We report two simulations that have been carried out at the SX-5 at HLRS
(Stuttgart). One simulation is axisymmetric and purely hydrodynamic, but with a
resolution of 20 points per beam-radius (ppb). The bipolar jet is injected in
the center of a spherically symmetric King profile, initially underdense to its
environment by a factor of 10,000. As expected from our previous work, the jet
starts with producing a spherical bubble around it, bounded by the bow shock.
The bubble slowly elongates, first with roughly elliptical shape, and then
forms narrower extensions in beam direction. The final aspect ratio of the bow
shock is 1.8. We have transformed the results on a 3D-rectangular grid and
integrated the emission properties to compare the results with observed central
cluster radio galaxies. In the particular case of Cygnus A, we come to
convincing consistency, morphologically, regarding the size of the influenced
region by the jet, size, and cylindrical shape of the radio cocoon, and source
age. This strongly supports our earlier hypothesis on the nature of the jet in
Cygnus A, and the derived constraints on other jet parameters like a power of
$8 \times 10^{46}$ erg/s and an age of 27 Myr. But, the simulation also clearly
shows the shortcoming of the model: The jet's beam is very unstable, reaching
the tip of the bow shock only very seldom. Also, the contact discontinuity
between shocked beam plasma and shocked ambient gas is quite disrupted by the
action of the Kelvin-Helmholtz-instability. This is not seen in observations,
and necessitates the presence of dynamically important magnetic fields or an at
least moderately relativistic flow, or both. [abridged]


title: The blue host galaxy of the red GRB 000418

abstract:
  We report on multi-band (UBVRIZJsKs) observations of the host galaxy of the
April 18, 2000 gamma-ray burst. The Spectral Energy Distribution (SED) is
analysed by fitting empirical and synthetic spectral templates. We find that:
(i) the best SED fit is obtained with a starburst template, (ii) the
photometric redshift is consistent with the spectroscopic redshift, (iii) the
colours of the host are inconsistent with an old stellar population, and (iv)
the global extinction is constrained to be in the range Av=0.12-0.61 mag. The
derived global extinction agrees with the one reported for the afterglow
(Av=0.4-0.9 mag), suggesting a homogeneous distribution of the interstellar
medium (ISM) in the host galaxy. These findings are supplemented by
morphological information from Hubble Space Telescope (HST) imaging: the
surface brightness profile is smooth, symmetric and compact with no underlying
structures (like dust lanes, spiral arms or disks). A natural scenario which
accounts of all the above results is a nuclear starburst that harbours a young
population of stars from which the GRB originated.


title:
High-Resolution Measurements of the Dark Matter Halo of NGC 2976:
  Evidence for a Shallow Density Profile

abstract:
  We have obtained two-dimensional velocity fields of the dwarf spiral galaxy
NGC 2976 in Halpha and CO. The high spatial (~75 pc) and spectral (13 km/s and
2 km/s, respectively) resolution of these observations, along with our
multicolor optical and near-infrared imaging, allow us to measure the shape of
the density profile of the dark matter halo with good precision. We find that
the total (baryonic plus dark matter) mass distribution of NGC 2976 follows a
rho_tot ~ r^(-0.27 +/- 0.09) power law out to a radius of 1.8 kpc, assuming
that the observed radial motions provide no support. The density profile
attributed to the dark halo is even shallower, consistent with a nearly
constant density of dark matter over the entire observed region. A maximal disk
fit yields an upper limit to the K-band stellar mass-to-light ratio (M*/L_K) of
0.09^{+0.15}_{-0.08} M_sun/L_sun,K (including systematic uncertainties), with
the caveat that for M*/L_K > 0.19 M_sun/L_sun,K the dark matter density
increases with radius, which is unphysical. Assuming 0.10 M_sun/L_sun,K <
M*/L_K < 0.19 M_sun/L_sun,K, the dark matter density profile lies between
rho_dm ~ r^-0.17 and rho_dm ~ r^-0.01. Therefore, independent of any
assumptions about the stellar disk or the functional form of the density
profile, NGC 2976 does not contain a cuspy dark matter halo. We also
investigate some of the systematic effects that can hamper rotation curve
studies, and show that 1) longslit rotation curves are far more vulnerable to
systematic errors than two-dimensional velocity fields, 2) NGC 2976 contains
large radial motions at small radii, and 3) the Halpha and CO velocity fields
of NGC 2976 agree within their uncertainties. [slightly abridged]


title: A Search for Mid-Infrared Emission from Hot Molecular Core Candidates

abstract:
  We present here mid-infrared images of seven sites of water maser emission
thought to be associated with the hot molecular core (HMC) phase of massive
star formation. Observations were obtained at the NASA InfraRed Telescope
Facility 3-m, the Gemini 8-m, and Keck II 10-m telescopes. We have detected
mid-infrared sources at the locations of two HMC candidates, G11.94-0.62 and
G45.07-0.13. We observed G19.61-0.23 and G34.26+0.15, each of which have HMCs
previously detected in the mid-infrared. We did not detect mid-infrared
emission from either HMC source, and we place new upper limits on the
mid-infrared flux densities for these HMCs that are much lower than their
previously reported flux densities. We were able to obtain extremely accurate
astrometry for our mid-infrared images of G9.62+0.19, and conclude that the
mid-infrared emission thought to be coming from the HMC in this field is in
fact coming from a different source altogether.


title:
Interstellar Hydroxyl Masers in the Galaxy. II. Zeeman Pairs and the
  Galactic Magnetic Field

abstract:
  We have identified and classified Zeeman pairs in the survey by Argon, Reid,
& Menten of massive star-forming regions with 18 cm (2 Pi 3/2, J = 3/2) OH
maser emission. We have found a total of more than 100 Zeeman pairs in more
than 50 massive star-forming regions. The magnetic field deduced from the
Zeeman splitting has allowed us to assign an overall line-of-sight magnetic
field direction to many of the massive star-forming regions. Combining these
data with other data sets obtained from OH Zeeman splitting, we have looked for
correlations of magnetic field directions between star-forming regions
scattered throughout the Galaxy. Our data do not support a uniform,
Galactic-scale field direction, nor do we find any strong evidence of magnetic
field correlations within spiral arms. However, our data suggest that in the
Solar neighborhood the magnetic field outside the Solar circle is oriented
clockwise as viewed from the North Galactic Pole, while inside the Solar circle
it is oriented counterclockwise. This pattern, including the magnetic field
reversal near the Sun, is in agreement with results obtained from pulsar
rotation measures.


title: A Relativistic Disk in Sagittarius A*

abstract:
  The detection of a mm/Sub-mm ``bump'' in Sgr A*'s radio spectrum suggests
that at least a portion of its overall emission is produced within a compact
accretion torus. This inference is strengthened by observations of strong
linear polarization (at the 10 percent level) within this bump. No linear
polarization has been detected yet at other wavelengths. Given that radiation
from this source is produced on progressively smaller spatial scales with
increasing frequency, the mm/Sub-mm bump apparently arises within a mere
handful of Schwarzschild radii of the black hole. We have found that a small
(10-Schwarzschild-radii) magnetized accretion torus can not only account for
the spectral bump via thermal synchrotron processes, but that it can also
reproduce the corresponding polarimetric results. In addition, the quiescent
X-ray emission appears to be associated with synchrotron self-Comptonization,
while X-ray flares detected from Sgr A* may be induced by a sudden enhancement
of accretion through this torus. This picture predicts correlations among the
mm, IR, and X-ray flux densities, that appear to be consistent with recent
multi-wavelength observations. Further evidence for such a torus in Sgr A* is
provided by its radio variability. Recent monitoring of Sgr A* at cm and mm
wavelengths suggests for a spectral break at 3 mm during cm/Sub-mm flares.
Radio emission from Sgr A* is intriguing since it is circularly polarized
though no linear polarization was ever detected. We first proved that the
emission must be due to nonthermal process should the flow be bounded. It is
then suggested that the nonthermal electrons are energized very close to the
black hole.


title: Turbulent Comptonization in Black Hole Accretion Disks

abstract:
  In the inner-most regions of radiation pressure supported accretion disks,
the turbulent magnetic pressure may greatly exceed that of the gas. If this is
the case, it is possible for bulk Alfvenic motions driven by the
magnetorotational instability (MRI) to surpass the electron thermal velocity.
Bulk rather than thermal Comptonization may then be the dominant radiative
process which mediates gravitational energy release. For sufficiently large
turbulent stresses, we show that turbulent Comptonization produces a
significant contribution to the far-UV and X-ray emission of black hole
accretion disks. The existence of this spectral component provides a means of
obtaining direct observational constraints on the nature of the turbulence
itself. We describe how this component may affect the spectral energy
distributions and variability properties of X-ray binaries and active galactic
nuclei.


title: Chandra Observations of the Interacting NGC 4410 Galaxy Group

abstract:
  We present high resolution X-ray imaging data from the ACIS-S instrument on
the Chandra telescope of the nearby interacting galaxy group NGC 4410. Four
galaxies in the inner portion of this group are clearly detected by Chandra,
including the peculiar low luminosity radio galaxy NGC 4410A. In addition to a
nuclear point source, NGC 4410A contains diffuse X-ray emission, including an
X-ray ridge extending out to about 12" (6 kpc) to the northwest of the nucleus.
This ridge is coincident with an arc of optical emission-line gas, which has
previously been shown to have optical line ratios consistent with shock
ionization. This structure may be due to an expanding superbubble of hot gas
caused by supernovae and stellar winds or by the active nucleus. The Chandra
observations also show four or five possible compact ultra-luminous X-ray (ULX)
sources (L(x) >= 10^39 erg/s) associated with NGC 4410A. At least one of these
candidate ULXs appears to have a radio counterpart, suggesting that it may be
due to an X-ray binary with a stellar-mass black hole, rather than an
intermediate mass black hole. In addition, a faint diffuse intragroup X-ray
component has been detected between the galaxies (L(x) ~ 10^41 erg/s). This
supports the hypothesis that the NGC 4410 group is in the process of evolving
via mergers from a spiral-dominated group (which typically have no
X-ray-emitting intragroup gas) to an elliptical-dominated group (which often
have a substantial intragroup medium).


title:
Some implications of the introduction of scattered starlight in the
  spectrum of reddened stars

abstract:
  This paper presents new investigations on coherent scattering in the forward
direction (orders of magnitude; conservation of energy; dependence of scattered
light on geometry and wavelength), and on how scattered light contamination in
the spectrum of reddened stars is possibly related to as yet unexplained
observations (the diminution of the 2200 A bump when the obscuring material is
close to the star, the difference between Hipparcos and photometric distances).
This paper then goes on to discuss the fit of the extinction curve, a possible
role of extinction by the gas in the far-UV, and the reasons of the inadequacy
of the Fitzpatrick and Massa [ApJSS, 72 (1990) 163] fit.


title: Exotic phases in compact stars

abstract:
  We discuss how the co-existence of hyperons, antikaon condensate and color
superconducting quark matter in neutron star interior influences the gross
properties of compact stars such as, the equation of state and mass-radius
relationship. We compare our results with the recent observations. We also
discuss about superdense stars in the third family branch which may contain a
pure color-flavor-locked (CFL) core.


title: Massive star formation in a gravitationally-lensed HII-galaxy at z=3.357

abstract:
  The Lynx arc, with a redshift of 3.357, was discovered during spectroscopic
follow-up of the z=0.570 cluster RX J0848+4456 from the ROSAT Deep Cluster
Survey. The arc is characterized by a very red R-K color and strong, narrow
emission lines. Analysis of HST WFPC2 imaging and Keck optical and infrared
spectroscopy shows that the arc is an \hii galaxy magnified by a factor of ~10
by a complex cluster environment. The high intrinsic luminosity, the emission
line spectrum, the absorption components seen in Ly\alpha and C IV, and the
restframe ultraviolet continuum are all consistent with a simple HII region
model containing ~ 10^6 hot O stars. The best fit parameters for this model
imply a very hot ionizing continuum (T_BB ~ 80,000 K), high ionization
parameter (log U ~ -1), and low nebular metallicity (Z / Z_\odot ~ 0.05). The
narrowness of the emission lines requires a low mass-to-light ratio for the
ionizing stars, suggestive of an extremely low metallicity stellar cluster. The
apparent overabundance of silicon in the nebula could indicate enrichment by
past pair instability supernov\ae, requiring stars more massive than ~140
M_\odot.


title:
The lack of variability of the iron line in MCG-6-30-15: general
  relativistic effects

abstract:
  The spectrum and variability of the Seyfert galaxy MCG-6-30-15 can be
decomposed into two apparently disconnected components: a highly variable power
law and an almost constant component which contains a broad and strong iron
line. We explore a possible explanation of the puzzling lack of variability of
the iron line, by assuming that the variations of the power law component are
due to changes in the height of the primary source in the near vicinity of a
rotating black hole. Due to the bending of light in the strong field of the
central black hole, the apparent brightness of the power-law component can vary
by about a factor 4 according to its position, while the total iron line flux
variability is less than 20 percent. This behaviour is obtained if the primary
source is located within 3-4 gravitational radii ($r_{\rm g}$) from the
rotation axis with a variable height of between $\sim$ 3 and 8 $r_{\rm g}$.
These results revive the possibility that future X-ray observations of
MCG-6-30-15 can map out the strong gravity regime of accreting black holes.


title:
Optical Identification of the ASCA Medium Sensitivity Survey in the
  Northern Sky: Nature of Hard X-ray-selected Luminous Active Galactic Nuclei

abstract:
  We present the results of optical spectroscopic identifications of a bright
subsample of 2-10keV hard X-ray selected sources from the ASCA Medium
Sensitivity Survey in the northern sky. The flux limit of the subsample is
3*10^-13 erg s^-1 cm^-2 in the 2-10keV band. All but one of the 87 hard X-ray
selected sources are optically identified, with AGNs, 7 clusters of galaxies,
and 1 galactic star. It is the largest complete sample of hard X-ray selected
AGNs at the bright flux limit. Amounts of absorption to their nuclei are
estimated to be hydrogen column densities (N_H) of up to ~3*10^23 cm^-2 from
their X-ray spectra. Optical properties of X-ray absorbed AGNs with N_H >
1*10^22 cm^-2 indicate the effects of dust absorption: at redshifts, z<0.6,
AGNs without broad H\beta emission lines have significantly larger N_H value
than AGNs with broad H\beta emission lines. At z>0.6, the X-ray absorbed AGNs
have a large hard X-ray to optical flux ratio (log f2-10keV/fR > +1). However,
three X-ray absorbed z>0.6 AGNs show strong broad lines. In combination with
hard X-ray selected AGN samples from the ASCA Large Sky Survey, the ASCA Deep
Survey in the Lockman Hole and Chandra Deep Field North, the luminosity
distributions of absorbed and less-absorbed AGNs are compared.


title:
The Galactic magnetic field and propagation of ultra-high energy cosmic
  rays

abstract:
  The puzzle of ultra-high energy cosmic rays (UHECRs) still remains
unresolved. With the progress in preparation of next generation experiments
(AUGER, EUSO, OWL) grows also the importance of directional analysis of
existing and future events. The Galactic magnetic field (GMF) plays the key
role in source identification even in this energy range. We first analyze
current status of our experimental and theoretical knowledge about GMF and
introduce complex up-to-date model of GMF. Then we present two examples of
simple applications of influence of GMF on UHECR propagation. Both examples are
based on Lorentz equation solution. The first one is basic directional analysis
of the incident directions of UHECRs and the second one is a simulation of a
change of chemical composition of CRs in the energy range 10^13 - 10^19 eV. The
results of these simple analyses are surprisingly rich - e.g. the rates of
particle escape from the Galaxy or the amplifications of particle flux in
specific directions.


title: Sunyaev Zel`dovich effect studies with MASTER

abstract:
  Our three frequencies radiometer MASTER which allows low noise observations
in three frequency intervals around 90, 220 and 345 GHz is being completed. We
discuss the possibility of exploiting the MASTER`s charachteristics for studies
of the Sunyaev Zel`dovich effect from the Antarctic Plateau and propose an
observational program from Dome C


title:
Dust Production from collisions in extrasolar planetary systems The
  inner Beta-Pictoris disc

abstract:
  Dust particles observed in extrasolar planetary discs originate from
undetectable km-sized bodies but this valuable information remains
uninteresting if the theoretical link between grains and planetesimals is not
properly known. We outline in this paper a numerical approach we developed in
order to address this issue for the case of dust producing collisional
cascades. The model is based on a particle-in-a-box method. We follow the size
distribution of particles over eight orders of magnitude in radius taking into
account fragmentation and cratering according to different prescriptions. A
very particular attention is paid to the smallest particles, close to the
radiation pressure induced cut-off size $R_{pr}$, which are placed on highly
eccentric orbits by the stellar radiation pressure....(abstract continued in
the uploaded paper)


title: Aging of the Universe and the fine structure constant

abstract:
  In this paper the aging of the Universe is investigated in the frame of
quantum hyperbolic heat transport equation. For the open universe, when t to
\infty, hbar to \infty, c to 0 and fine structure constant alpha is constant.
Key words: Quantum heat transport; Open universe; Fine structure constant.


title:
Survey of long-term variability of stars I. Reliability of magnitudes in
  old star catalogues

abstract:
  The comparison of visual magnitudes of stars compiled in old catalogues is
expected to yield information about their long-term magnitude variations. In
seven old catalogues whose historical data have been intensively compared, 2123
sampled stars have been studied, disregarding stars that we could not identify,
double stars which could be misidentified, or stars observed under poor
conditions, and known variable stars with large amplitude discrepancies. The
independence of stellar magnitude catalogues is demonstrated by comparing seven
old studies to each other, suggesting that the magnitude estimates in each
catalogue reflect the brightness at each observational period. Furthermore, by
comparing them with a modern star catalogue, the magnitude differences show a
Gaussian distribution. Therefore, if they are sufficiently larger than the
deduced standard deviations, the magnitude variations between the catalogues
can be considered real. Thus, the stellar magnitudes compiled in old studies
can be used as scientific data within the average intrinsic uncertainty. These
seven old catalogues can be used as data for the survey of the long-term
variability of stars.


title: X-ray rotational modulation of a supersaturated star in IC 2391

abstract:
  We present evidence of X-ray rotational modulation on VXR45, a young fast
rotator star, member of IC 2391. It is a dG9 spectral type star whose
rotational period and X-ray luminosity make it a supersaturated star. Our X-ray
observation, made with EPIC/PN on XMM-Newton, covers about two photometric
rotational periods. The detection of rotational modulation implies the presence
of structural inhomogeneities. Possible interpretations are presented and
discussed.


title:
Massive black hole remnants of the first stars I: abundance in
  present-day galactic haloes

abstract:
  We investigate the possibility that present-day galaxies and their dark
matter haloes contain a population of massive black holes (MBHs) that form by
hierarchical merging of the black hole remnants of the first stars in the
Universe. Some of the MBHs may be large enough or close enough to the centre of
the galactic host that they merge within a Hubble time. We estimate to what
extent this process could contribute to the mass of the super-massive black
holes (SMBHs) observed in galactic centres today. The relation between SMBH and
galactic bulge mass in our model displays the same slope as that found in
observations. Many MBHs will not reach the centre of the host halo, however,
but continue to orbit within it. In doing so MBHs may remain associated with
remnants of the satellite halo systems of which they were previously a part.
Using a semi-analytical approach that explicitly accounts for dynamical
friction, tidal disruption and encounters with galactic disks, we follow the
hierarchical merging of MBH systems and their subsequent dynamical evolution
inside the respective host haloes. We predict the mass and abundance of MBHs in
present-day galactic haloes, and also estimate the MBH mass accretion rates as
well as bolometric luminosities for two different accretion scenarios. MBHs
that have not undergone recent merging will retain associated dark matter cusps
that were enhanced by black hole accretion growth, and may be possible sources
of gamma rays via neutralino annihilations.


title: Monte Carlo Radiative Transfer in Embedded Prestellar Cores

abstract:
  We implement a Monte Carlo radiative transfer method, that uses a large
number of monochromatic luminosity packets to represent the radiation
transported through a system. These packets are injected into the system and
interact stochastically with it. We test our code against various benchmark
calculations and determine the number of packets required to obtain accurate
results under different circumstances. We then use this method to study cores
that are directly exposed to the interstellar radiation field (non-embedded
cores) and find similar results with previous studies. We also explore a large
number of models of cores that are embedded in the centre of a molecular cloud.
Our study indicates that the temperature profiles in embedded cores are less
steep than those in non-embedded cores. Deeply embedded cores (ambient cloud
with visual extinction larger than 15-25) are almost isothermal at around 7-8
K. The temperature inside cores surrounded by an ambient cloud of even moderate
thickness (Av~5) is less than 12 K, which is lower than previous studies have
assumed. Thus, previous mass calculations of embedded cores (for example in the
rho Ophiuchi protocluster), based on mm continuum observations, may
underestimate core masses by up to a factor of 2. Our study shows that the best
wavelength region to observe embedded cores is between 400 and 500 microns,
where the core is quite distinct from the background. We also predict that very
sensitive observations (~1-3 MJy/sr) at 170-200 microns can be used to estimate
how deeply a core is embedded in its parent molecular cloud. The upcoming
HERSCHEL mission (ESA, 2007) will, in principle, be able to detect these
features and test our models.