title: The masses of AGN host galaxies & the origin of radio loudness

abstract:
  We highlight some of the principal results from our recent Hubble Space
Telescope studies of quasars and radio galaxies. The hosts of these powerful
AGN are normal massive ellipticals which lie on the region of the fundamental
plane populated predominantly by massive ellipticals with boxy isophotes and
distinct cores. The hosts of the radio-loud sources are on average 1.5 times
brighter than their radio-quiet counterparts and appear to lie above a mass
threshold of 4 x 10^11 solar masses. This suggests that black holes more
massive than 5 x 10^8 solar masses are required to produce a powerful radio
source. However we show that this apparent threshold appears to be a
consequence of an upper bound on radio output which is a strong function of
black-hole mass, L_5GHz proportional to M_bh^2.5. This steep mass dependence
can explain why the hosts of the most powerful radio sources are good standard
candles. Such objects were certainly fully assembled by z = 1, and appear to
have formed the bulk of their stars prior to z = 3.


title: Evidence for a relativistic iron line in GRS 1915+105

abstract:
  We report on the discovery of a relativistic iron K\alpha fluorescent
emission line in the BeppoSAX spectrum of the microquasar GRS 1915+105, taken
on April 19, 1998, when the line was unusually intense. The feature is broad
and skewed, clearly indicating emission from the innermost regions of the
accretion disc. The inner emitting orbit is larger than the innermost stable
orbit, even in Schwarzschild metric: thus, a non-zero BH spin is not required
by these data.


title: Infrared Photometry of the Globular Cluster Palomar 6

abstract:
  We present JHK photometry of Palomar 6. Our photometric measurements range
from the RGB-tip to 2 mag below the RHB and our CMDs show that Palomar~6
appears to have a well-defined RHB population. The distance modulus and
interstellar reddening of the cluster are estimated by comparing the magnitude
and color of Palomar 6 RHB stars with respect to those of 47 Tuc. We obtain
(m-M)_0 = 14.28 mag and E(B-V) = 1.30 mag for the cluster and our study
suggests that Palomar~6 is clearly located in the Galaxy's central regions. We
also discuss the metallicity of the cluster using the slope of the RGB. We
obtain [Fe/H] = -1.2 for Palomar~6 and our metallicity estimate is 0.5 - 1.0
dex lower than previous estimates by others.


title: Dynamical relaxation and the orbits of low-mass extrasolar planets

abstract:
  We consider the evolution of a system containing a population of massive
planets formed rapidly through a fragmentation process occurring on a scale on
the order of 100 au and a lower mass planet that assembles in a disc on a much
longer timescale. During the formation phase, the inner planet is kept on a
circular orbit due to tidal interaction with the disc, while the outer planets
undergo dynamical relaxation. Interaction with the massive planets left in the
system after the inner planet forms may increase the eccentricity of the inner
orbit to high values, producing systems similar to those observed.


title:
High-Resolution Optical Rotation Curves of Low-Luminosity Spiral
  Galaxies

abstract:
  We present optical longslit spectroscopic observations of 21 low-luminosity,
extreme late-type spiral galaxies. Our sample is comprised of Sc-Sm Local
Supercluster spirals with moderate-to-low optical surface brightnesses and with
luminosities at the low end for spiral disk galaxies (M_V>-18.8). For each
galaxy we have measured high spatial resolution position-velocity (P-V) curves
using the H alpha emission line, and for 15 of the galaxies we also derive
major axis rotation curves. In ~50% of our sample, the P-V curves show
significant asymmetries in shape, extent, and/or amplitude on the approaching
and receding sides of the disk. A number of the P-V curves are still rising to
the last measured point, or reach a clear turnover on only one side. In most
instances we find good agreement between the kinematic centers of extreme
late-type spirals as defined by the global HI emission profile and by their
optical continuum, although in a few cases we see evidence of possible real
offsets. In spite of their shallow central gravitational potentials, at least 6
of the galaxies in our sample possess semi-stellar nuclei that appear to be
compact nuclear star clusters; in 5 of these cases we see kinematic signatures
in the P-V curves at the location of the nucleus. Finally, we find that like
giant spirals, our sample galaxies have higher specific angular momenta than
predicted by current cold dark matter models.


title:
The Cluster Gas Mass - Temperature Relation: Evidence for a High Level
  of Preheating

abstract:
  Recent X-ray observations have been used to demonstrate that the cluster gas
mass-temperature relation is steeper than theoretical self-similar predictions
drawn from numerical simulations that consider the evolution of the cluster gas
through the effects of gravity and shock heating alone. One possible
explanation for this is that the gas mass fraction is not constant across
clusters of different temperature, as is usually assumed. Observationally,
however, there is no compelling evidence for gas mass fraction variation,
especially in the case of hot clusters. Seeking an alternative physical
explanation for the observed trends, we investigate the role in the cluster gas
mass - temperature relation of the preheating of the intracluster medium by
some arbitrary source for clusters with emission-weighted mean temperatures of
greater than about 3 keV. Making use of the physically-motivated, analytic
models developed in 2002 by Babul and coworkers, we find that preheating does,
indeed, lead to a steeper relation. This is in agreement with previous
theoretical studies on the relation. However, in apparent conflict with these
studies, we argue that a ``high'' level of entropy injection is required to
match observations. In particular, an entropy floor of greater than about 300
keV cm^2 is required. We also present a new test, namely, the study of the
relation within different fixed radii. This allows one to indirectly probe the
density profiles of clusters, since it samples different fractions of the
virial radius for clusters of different temperature. This test also confirms
that a high level of preheating is required to match observations.


title:
A Mini-survey of X-ray Point Sources in Starburst and Non-Starburst
  Galaxies

abstract:
  We present a comparison of X-ray point source luminosity functions of 3
starburst galaxies (the Antennae, M82, and NGC 253) and 4 non-starburst spiral
galaxies (NGC 3184, NGC 1291, M83, and IC 5332). We find that the luminosity
functions of the starbursts are flatter than those of the spiral galaxies; the
starbursts have relatively more sources at high luminosities. This trend
extends to early-type galaxies which have steeper luminosity functions than
spirals. We show that the luminosity function slope is correlated with 60
micron luminosity, a measure of star formation. We suggest that the difference
in luminosity functions is related to the age of the X-ray binary populations
and present a simple model which highlights how the shape of the luminosity
distribution is affected by the age of the underlying X-ray binary population.


title:
The Giant X-Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown
  Dwarf, or a Planet?

abstract:
  We model the 1990 giant X-ray flare of the quiescent galaxy NGC 5905 as the
tidal disruption of a star by a supermassive black hole. From the observed
rapid decline of the luminosity, over a timescale of a few years, we argue that
the flare was powered by the fallback of debris rather than subsequent
accretion via a thin disk. The fallback model allows constraints to be set on
the black hole mass and the mass of debris. The latter must be very much less
than a solar mass to explain the very low luminosity of the flare. The
observations can be explained either as the partial stripping of the outer
layers of a low-mass main sequence star or as the disruption of a brown dwarf
or a giant planet. We find that the X-ray emission in the flare must have
originated within a small patch rather than over the entire torus of
circularized material surrounding the black hole. We suggest that the patch
corresponds to the ``bright spot'' where the stream of returning debris impacts
the torus. Interestingly, although the peak luminosity of the flare was highly
sub-Eddington, the peak flux from the bright spot was close to the Eddington
limit. We speculate on the implications of this result for observations of
other flare events.


title:
ISOCAM observations of the Ursa Major cirrus: Evidence for large
  abundance variations of small dust grains

abstract:
  We present mid-IR imaging observations of a high Galactic latitude cirrus
obtained with the ISO camera ISOCAM at 6" angular resolution. The observations
were done with two filters LW2 (5-8.5 microns) and LW3 (12-18 microns) that
measure respectively the aromatic carbon bands and the underlying continuum
emission from small dust particles. Three 0.05 square degree images sample
atomic and molecular sections in the Ursa Major cirrus. These images are
compared with Hi, CO and IRAS observations. In such a cloud transparent to
stellar light (Av < 0.5) the mid-infrared to 100 microns and the mid-IR
emissivity per hydrogen are related to the abundance and the optical properties
of small dust particles independently of any modelling of the penetration of
the radiation. Within the atomic section of the cloud, the comparison between
ISOCAM images and 21 cm interferometric data highlights an enhancement of the
mid-IR emitters abundance by a factor ~5 in an Hi filament characterized by a
large transverse velocity gradient suggestive of rotation. Furthermore, a drop
in the abundance of the same mid-IR emitters is observed at the interface
between the atomic and molecular cirrus sections. We propose that these
abundance variations of the mid-IR emitters are related to the production of
small dust particles by grain shattering in energetic grain-grain collisions
generated by turbulent motions within the cirrus and inversely by their
disappearance due to coagulation on large grains. At the atomic-molecular
interface we also observe a decrease of the Lw2/Lw3 ratio by a factor 2 in the
molecular region. This could result from a modification of the dust size
distribution or of the intrinsic optical properties of the small dust
particles.


title:
The Prompt Inventory from Very Massive Stars and Elemental Abundances in
  Ly Alpha Systems

abstract:
  It has been proposed that very massive stars (VMSs) dominated heavy element
production until a metallicity threshold corresponding to [Fe/H]=-3 was
reached. This results in a prompt (P) inventory of elements, the abundances of
which were determined from observations of Galactic halo stars with [Fe/H]=-3.
We calculate Omega_P(E) from the P inventory for a large number of elements in
the IGM. Using the available data on Omega(E_ion) for C IV, O VI, and Si IV in
Ly alpha systems, we find that the ionization fractions calculated from
Omega(E_ion)/Omega_P(E) are, within reasonable uncertainties, compatible with
the values estimated from ionization models for Ly alpha systems. This
agreement appears to hold from z=0.09 to 4.6, indicating that the bulk of the
baryonic matter remains dispersed with a fixed chemical composition. We
conclude that the P inventory was established in the epoch prior to z=4.6. The
dispersal of processed baryonic matter to the general IGM is considered to be
the result of energetic VMS explosions that disrupted baryonic aggregates until
the metallicity threshold was reached to permit normal astration. The formation
of most galaxies is considered to have occurred subsequent to the achievement
of this metallicity threshold in the IGM.


title: Neutrino-Induced Fission and r-Process Nucleosynthesis

abstract:
  An r-process scenario with fission but no fission cycling is considered to
account for the observed abundance patterns of neutron-capture elements in
ultra-metal-poor stars. It is proposed that neutrino reactions play a crucial
role in inducing the fission of the progenitor nuclei after the r-process
freezes out in Type II Supernovae. To facilitate neutrino-induced fission, the
proposed r-process scenario is restricted to occur in a low-density environment
such as the neutrino-driven wind from the neutron star. Further studies to
develop this scenario are emphasized.


title: The Search for Intergalactic Hydrogen Clouds in Voids

abstract:
  I present the results of a search for intergalactic hydrogen clouds in voids.
Clouds are detected by their HI LyA absorption lines in the HST spectra of
low-redshift AGN. The parameter with which the environments of clouds are
characterized is the tidal field, which places a lower limit on the cloud
mass-density which is dynamically stable against disruption. Galaxy redshift
catalogs are used to sum the tidal fields along the lines of sight, sorting
clouds according to tidal field upper, or lower limits. The analytical
methodology employed is designed to detect gas clouds whose expansion following
reionization is restrained by dark matter perturbations. End-products are the
cloud equivalent width distribution functions (EWDF) of catalogs formed by
sorting clouds according to various tidal field upper, or lower limits.
  Cumulative EWDFs are steep in voids (S ~ -1.5 \pm 0.2), but flatter in high
tidal field zones (S ~ -0.5 \pm 0.1). Most probable cloud Doppler parameters
are ~30 km/s in voids and ~60 km/s in proximity to galaxies. In voids, the
cumulative line density at low EW (~ 15 mA) is ~ 500 per unit redshift. The
void filling factor is found to be 0.87 <= f_v <= 0.94. The void EWDF is
remarkably uniform over this volume, with a possible tendency for more massive
clouds to be in void centers. The size and nature of the void cloud population
suggested by this study is completely unanticipated by the results of published
3-D simulations, which predict that most clouds are in filamentary structures
around galaxy concentrations, and that very few observable absorbers would lie
in voids. Strategies for modeling this population are briefly discussed.


title: Dissecting a galaxy: mass distribution of 2237+0305

abstract:
  We determine the mass distribution of a spiral galaxy, 2237+0305 using both
gravitational lensing and dynamical constraints. We find that lensing can break
the disc-halo degeneracy. 2237+0305 has a sub-maximal disc, contributing 57+/-3
per cent of the rotational support at the disc maximum. The disc mass-to-light
ratio is 1.1+/-0.2 in the I-band and the bulge, 2.9+/-0.5. The dark matter
halo, modelled as a softened isothermal sphere, has a large core radius
(13.4+/-0.4 kpc, equivalent to 1.4r_d) to high accuracy for the best-fitting
solution. The image positions are reasonably well fitted, but require further
rotation information to obtain a unique solution.


title: Cosmological Nucleosynthesis in the Big-Bang and Supernovae

abstract:
  Recent observation of the power spectrum of Cosmic Microwave Background (CMB)
Radiation has exhibited that the flat cosmology is most likely. This suggests
too large universal baryon-density parameter $\Omega_b h^2 \approx 0.022 \sim
0.030$ to accept a theoretical prediction, $\Omega_b h^2 \le 0.017$, in the
homogeneous Big-Bang model for primordial nucleosynthesis. Theoretical upper
limit arises from the sever constraints on the primordial $^7$Li abundance. We
propose two cosmological models in order to resolve the descrepancy; lepton
asymmetric Big-Bang nucleosynthesis model, and baryon inhomogeneous Big-Bang
nucleosynthesis model. In these cosmological models the nuclear processes are
similar to those of the r-process nucleosynthesis in gravitational collapse
supernova explosions.
  Massive stars $\geq 10 M_{\odot}$ culminate their evolution by supernova
explosions which are presumed to be the most viable candidate site for the
r-process nucleosynthesis. Even in the nucleosynthesis of heavy elements,
initial entropy and density at the surface of proto-neutron stars are so high
that nuclear statistical equilibrium favors production of abundant light
nuclei. In such explosive circumstances many neutron-rich radioactive nuclei of
light-to-intermediate mass as well as heavy mass nuclei play the significant
roles.


title:
Spatial distribution of emission in Unidentified Infrared Bands from
  Midcourse Space Experiment Survey

abstract:
  Recently the Midcourse Space Experiment (MSX) has surveyed the Galactic plane
in mainly four infrared bands between 6 and 25 micron. Two of these bands cover
several Unidentified Infrared emission Bands (UIBs). With the aim of extracting
the spatial distribution of the UIB emission on a large scale, a scheme has
been developed to model the MSX data with emission in the UIBs alongwith the
underlying thermal continuum from the interstellar dust. In order to test this
scheme, a sample of five Galactic compact H II regions (Sh-61, Sh-138, Sh-152,
Sh-156, Sh-186; Zavagno & Ducci 2001) for which imaging study in some
individual UIBs is available from ISOCAM measurements, has been studied. The
results of this comparative study on small angular scale are as follows : (i)
the morphological details extracted from our scheme agree very well with those
from the superior ISOCAM measurements; (ii) the integrated strength of UIBs
extracted from the MSX database correlates extremely well with the sum of the
strengths of individual UIBs measured from ISOCAM. This tight correlation is
very encouraging and promises the potential of MSX database for study of large
scale spatial distribution of UIB emission (and the carriers of UIBs) in the
entire Galactic plane.


title:
The black hole mass of BL Lac objects from the stellar velocity
  dispersion of the host galaxy

abstract:
  The correlation between black hole mass M(BH) and stellar velocity dispersion
sigma in nearby elliptical galaxies affords a novel way to determine M(BH) in
active galaxies. We report on measurements of sigma from optical spectra of 7
BL Lac host galaxies. The derived values of sigma are in the range of 160 - 290
km/s corresponding to M(BH) of 5 x 10^7 to 1 x 10^9 Msun. The average ratio of
M(BH) to the host galaxy mass is 1.4 x 10^-3, consistent with that estimated in
other active and inactive galaxies. The velocity dispersions and the derived
values of M(BH) of the BL Lacs are similar to those obtained for low redshift
radio galaxies, in good agreement with the predictions of the unified models
for radio-loud active galaxies.


title: On the density of Cold Dark Matter

abstract:
  The nature of dark matter is increasingly constrained by cosmological data.
In this paper, we examine the implications of the Cosmic Microwave Background
anisotropy limits on the density of cold dark matter under different
theoretical assumptions and combinations of datasets. We infer the constraint
$\Omega_{cdm}h^2=0.12\pm0.04$ (at 95% c.l.). The CDM models are compared with
the shape of the linear matter power spectrum inferred from the 2dF galaxy
redshift survey and with the rms mass fluctuations from recent local cluster
observations. We found that a value of $\sigma_8 \sim 1$ as suggested by recent
cosmic shear data is not favoured by the CMB data alone nor by combined
CMB+SN-Ia, CMB+HST or CMB+2dFGRS analyses. We also extrapolate our bounds on
the rms linear mass fluctuations to sub-galactic scales and compare them with
recent lensing constraints, finding agreement with the standard $\Lambda$CDM
model.


title: Colour Evolution of Disk Galaxy Models from z=4 to z=0

abstract:
  We calculate synthetic UBVRIJHKLM images, integrated spectra and colours for
the disk galaxy formation models of Samland & Gerhard (2002), from redshift z=4
to z=0. Two models are considered, an accretion model based on LambdaCDM
structure formation simulations, and a classical collapse model in a dark
matter halo. Both models provide the star formation history and dynamics of the
baryonic component within a three-dimensional chemo-dynamical description. To
convert to spectra and colours, we use the latest, metallicity-calibrated
spectral library of Westera et al. (2002), including internal absorption. As a
first application, we compare the derived colours with Hubble Deep Field North
bulge colours and find good agreement. With our model, we disentangle
metallicity effects and absorption effects on the integrated colours, and find
that absorption effects are dominant for redshift z < 1.5. Furthermore, we
confirm the quality of m_K as a mass tracer, and find indications for a
correlation between (J-K) and metallicity gradients.


title:
Reprocessing of X-rays in AGN. I. Plane parallel geometry -- test of
  pressure equilibrium

abstract:
  We present a model of the vertical stratification and the spectra of an
irradiated medium under the assumption of constant pressure. Such a solution
has properties intermediate between constant density models and hydrostatic
equilibrium models, and it may represent a flattened configuration of gas
clumps accreting onto the central black hole. Such a medium develops a hot
skin, thicker than hydrostatic models, but thinner than constant density
models, under comparable irradiation. The range of theoretical values of the
alpha_ox index is comparable to those from hydrostatic models and both are
close to the observed values for Seyfert galaxies but lower than in quasars.
The amount of X-ray Compton reflection is consistent with the observed range.
The characteristic property of the model is a frequently multicomponent iron K
alpha line.


title: Looking for the First Galaxies with EMIR/GTC

abstract:
  The new Pop III models by Schaerer (2002) have been used to derive the
observed properties of the first galaxies in terms of the expected magnitudes
and colors. The dependence of their properties on the IMF and upper mass limit
for star formation are studied. The emerging synthetic spectra are used to
discuss the implications on different observational features. Strong emission
lines, such as Lyman-alpha and HeII 1640, could easily be detected with a good
S/N with near-IR medium resolution spectrographs, such as EMIR at GTC. Our
simulations aim at exploring possible observational constraints on the
formation epoch of the first stars in galaxies.


title: Large-scale gas disk around the radio galaxy Coma A

abstract:
  We present WSRT and VLA radio observations of the neutral hydrogen in the
radio galaxy Coma A. We detect extended HI absorption against both radio lobes
of Coma A, at distances of about 30 kpc from the centre. Coma A is the first
radio galaxy in which HI is seen in absorption at such large distances from the
nucleus. The match between the velocities of the neutral hydrogen and those of
the extended ionized gas suggests that they are part of the same disk-like
structure of at least 60 kpc in diameter. Most likely, this gas disk is partly
ionised by the bulk motion of the radio lobes expanding into it. The gas mass
of this disk is at least 10^9 Msun. The relatively regular structure of the gas
disk suggests that a merger occurred involving at least one large gas-rich
galaxy, at least a few times 10^8 yr ago.


title: The peculiar velocity field in a quintessence model

abstract:
  We investigate the evolution of matter density perturbations and some
properties of the peculiar velocity field for a special class of exponential
potentials in a scalar field model for quintessence, for which a general exact
solution is known. The data from the 2-degree Field Galaxy Redshift Survey
(2dFGRS) suggest a value of the today pressureless matter density Omega_M0 =
0.18 +- 0.05.


title: IRAS 21391+5802: The Molecular Outflow and its Exciting Source

abstract:
  We present centimeter and millimeter observations of gas and dust around IRAS
21391+5802, an intermediate-mass source embedded in the core of IC 1396N.
Continuum observations from 3.6 cm to 1.2 mm are used to study the embedded
objects and overall distribution of the dust, while molecular line observations
of CO, CS, and CH3OH are used to probe the structure and chemistry of the
outflows in the region. The continuum emission at centimeter and millimeter
wavelengths has been resolved into three sources separated about 15 arcsec from
each other, and with one of them, BIMA 2, associated with IRAS 21391+5802. The
dust emission around this source shows a very extended envelope, which accounts
for most of the circumstellar mass of 5.1 Msun. This source is powering a
strong molecular outflow, elongated in the E--W direction, which presents a
complex structure and kinematics. While at high outflow velocities the outflow
is clearly bipolar, at low outflow velocities the blueshifted and redshifted
emission are highly overlapping, and the strongest emission shows a V-shaped
morphology. The outflow as traced by CS and CH3OH exhibits two well
differentiated and clumpy lobes, with two prominent northern blueshifted and
redshifted clumps. The curved shape of the clumps and the spectral shape at
these positions are consistent with shocked material. In addition, CS and CH3OH
are strongly enhanced toward these positions with respect to typical quiescent
material abundances in other star-forming regions.


title: Timing with the EPIC pn Camera of XMM-Newton

abstract:
  The EPIC pn CCD camera on board of XMM-Newton is designed to perform high
throughput imaging and spectroscopy as well as high resolution timing
observations in the energy range of 0.1-15 keV. A temporal resolution of
milliseconds or microseconds, depending on the instrument mode and detector, is
outstanding for CCD based X-ray cameras. In order to calibrate the different
observing modes of the EPIC pn CCD, XMM-Newton observations of the pulsars PSR
B1509-58, PSR B0540-69 and the Crab were performed during the calibration and
performance verification phase. To determine the accuracy of the on board clock
against Coordinated Universal Time (UTC), PSR B1509-58 was observed
simultaneously with XMM-Newton and RXTE in addition. The paper summarizes the
current status of the clock calibration.


title:
A Self-Similar Solution for the Propagation of a Relativistic Shock in
  an Exponential Atmosphere

abstract:
  We derive a fully relativistic, self-similar solution to describe the
propagation of a shock along an exponentially decreasing atmosphere, in the
limit of very large Lorentz factor. We solve the problem in planar symmetry and
compute the acceleration of the shock in terms of the density gradient crossed
during its evolution. We apply our solution to the acceleration of shocks
within the atmosphere of a HyperNova, and show that velocities consistent with
the requirements of GRB models can be achieved with exponential atmospheres
spanning a wide density range.


title:
The outer atmosphere of the M-type supergiant alpha Orionis: KI 7699A
  emission

abstract:
  Spatially-resolved high-resolution long-slit spectra of Betelgeuse's
circumstellar shell are described for a spectral window centered on the 7699\AA
resonance line of neutral potassium. The K I emission from resonance
fluorescent scattering of photospheric photons which is mapped out to 50 arcsec
from the star is approximately spherically symmetric with a brightness
decreasing as r^{-2.36 \pm 0.03}, where $r$ is the radial distance from the
star. Our measurements together with the earlier theoretical interpretation by
Rodgers & Glassgold suggest that the mass loss rate is about 2 . 10^{-6} solar
mass/year. The K I emission is far from homogeneous: intensity inhomogeneities
are seen down to the seeing limit of about 1 arcsec and the velocity resolution
of about 2 km/s. There is clear evidence for a thin shell of 50 arcsec radius.
This is identified with the weaker circumstellar absorption component known as
S2. Estimates are made of the density of K atoms in this shell (approx. 6 .
10^{-5} cm^{-3}).


title: HI and Galactic Structure

abstract:
  HI observations in the 21cm line have been a principal tool for investigating
the large-scale structure of the Milky Way. This review considers what was
learned in the first decade after the discovery of the 21cm line, and how that
knowledge has been expanded and refined in subsequent years. Topics include
spiral structure, the Galactic nucleus, the thickness of the HI layer, and
affairs in the outskirts of the Galaxy. New advances in instrumentation and
computing, and a broad attack on problems using information from all
wavelengths, are likely to keep HI studies of the Milky Way interesting for
years to come.


title: The Nature of Submm-Detected Galaxies

abstract:
  We present high resolution VLT spectra of 2 submm-detected galaxies.
Diagnostic stellar absorption lines (Starburst99) are used to analyse their
stellar population. SMM J14011+0252 (z=2.565) shows signs of starburst and SMM
J02399-0136 (z=2.808) shows signs of starburst and AGN. A MgII line at z~0.94
is identified in the latter galaxy and could account for an extra magnification
factor in this SCUBA source.


title: The unified model of compact radio sources

abstract:
  We propose the unified model of compact radio sources, i.e. of pulsars, maser
sources, and active galactic nuclei. The unification is based on the wavelength
dependence of radio source size. It is shown that the compact sources are
characterized by a maser amplification of thermal radio emission. The density,
temperature, and magnetic field profiles of compact sources are discussed.


title:
A Her X-1 Turn-On: Using the pulse profile to probe the outer edge of an
  accretion disk

abstract:
  The X-ray binary pulsar Her X-1 shows a wide variety of long and short term
variabilities in the X-ray light curve. The 35 d variability of the source is
interpreted as the influence of a warped, inclined, and twisted accretion disk
periodically covering the line of sight to the central neutron star. In 1997
September we observed the ``turn-on'' of a 35 d cycle with the Rossi X-ray
Timing Explorer (RXTE). Spectral analysis reveals that during early phases of
the turn-on the overall spectrum is composed of X-rays scattered into the line
of sight plus heavily absorbed X-rays. This interpretation is consistent with
the variation of the pulse profile observed at the same time. The overall shape
of the pulse profile is not changing, but towards earlier phases of the turn-on
the pulse signature is steadily ``washed out''. This behavior can be understood
as an influence of scattering and absorption due to the presence of the
accretion disk rim. Using a Monte Carlo code we simulate the influence of both
processes on a time variable, beamed emission characteristic, similar to the
pulse profile of Her X-1. By comparing the results of the simulation with the
observed profiles we determine the amount of scattered radiation, absorbed
radiation, and the size of the scattering region.


title:
Cosmological Microlensing Statistics: Variability rates for Quasars and
  GRB Afterglows, and implications for macrolensing magnification bias and flux
  ratios

abstract:
  The fraction of quasar's and gamma-ray burst (GRB) afterglows that vary due
to microlensing by the stellar populations of intervening elliptical/S0
galaxies is computed by combining the joint distribution of effective
microlensing convergence (kappa) and shear (gamma) with microlensing
magnification patterns. Microlensing is common in multiply imaged sources. We
find that 1 in 3 multiply imaged quasars should vary by more than 0.5
magnitudes per decade due to microlensing, while 10% of macrolensed GRB
afterglows should show a departure of more than 0.5 magnitudes from their
intrinsic light-curve during the first 30 days. However microlensing by stars
is rare in general, with only 1 source in ~500 varying by more than 0.5
magnitudes during the same periods. We find that most microlensing by stars
will be observed in a regime where gamma>0.1. Thus point-mass lenses do not
provide an adequate description for most microlensing events. If dark matter
halos contain a large fraction of mass in compact objects, the fraction of
microlensed (by 0.5 magnitudes) images rises significantly to ~1 in 10 for
quasars and ~1 in 5 for GRB afterglows. Comparison of variability between
macrolensed and normal quasar images, and a moderate number of well sampled GRB
afterglow light-curves should therefore discover or refute the existence of
stellar mass compact objects in galaxy halos. While microlensing results in
departures of the distribution of magnifications from that of a smooth model,
the effect on the macrolensing magnification bias for the discovery of lenses
in quasar surveys is small. On the other hand, microlensing significantly
broadens the distribution of macrolensed image flux ratios.


title:
Directionality of Solar Flare Accelerated Protons and Alpha Particles
  from Gamma-Ray Line Measurements

abstract:
  The energies and widths of gamma-ray lines emitted by ambient nuclei excited
by flare-accelerated protons and alpha particles provide information on the
ions directionality and spectra, and on the characteristics of the interaction
region. We have measured the energies and widths of strong lines from
de-excitations of 12C, 16O, and 20Ne in solar flares as a function of
heliocentric angle. The line energies from all three nuclei exhibit ~1%
redshifts for flares at small heliocentric angles, but are not shifted near the
limb. The lines have widths of ~3% FWHM. We compare the 12C line measurements
for flares at five different heliocentric angles with calculations for
different interacting-particle distributions. A downward isotropic distribution
(or one with a small upward component) provides a good fit to the line
measurements. An angular distribution derived for particles that undergo
significant pitch angle scattering by MHD turbulence in coronal magnetic loops
provides comparably good fits.


title: Solar System Objects in the ISOPHOT 170 micron Serendipity Survey

abstract:
  The ISOPHOT Serendipity Survey (ISOSS) covered approximately 15 % of the sky
at a wavelength of 170 micron while the ISO satellite was slewing from one
target to the next. By chance ISOSS slews went over many solar system objects
(SSOs). We identified the comets, asteroids and planets in the slews through a
fast and effective search procedure based on N-body ephemeris and flux
estimates. The detections were analysed from a calibration and scientific point
of view. Through the measurements of the well-known asteroids Ceres, Pallas,
Juno and Vesta and the planets Uranus and Neptune it was possible to improve
the photometric calibration of ISOSS and to extend it to higher flux regimes.
We were also able to establish calibration schemes for the important slew end
data. For the other asteroids we derived radiometric diameters and albedos
through a recent thermophysical model. The scientific results are discussed in
the context of our current knowledge of size, shape and albedos, derived from
IRAS observations, occultation measurements and lightcurve inversion
techniques. In all cases where IRAS observations were available we confirm the
derived diameters and albedos. For the five asteroids without IRAS detections
only one was clearly detected and the radiometric results agreed with sizes
given by occultation and HST observations. Four different comets have clearly
been detected at 170 micron and two have marginal detections. The observational
results are presented to be used by thermal comet models in the future. The
nine ISOSS slews over Hale-Bopp revealed extended and asymmetric structures
related to the dust tail. We attribute the enhanced emission in post-perihelion
observations to large particles around the nucleus. The signal patterns are
indicative of a concentration of the particles in trail direction.


title: A Limit on the Metallicity of Compact High Velocity Clouds

abstract:
  There is a fortuitous coincidence in the positions of the quasar TonS210 and
the compact H I high velocity cloud CHVC224.0-83.4-197 on the sky. Using Far
Ultraviolet Spectroscopic Explorer observations of the metal-line absorption in
this cloud and sensitive H I 21cm emission observations obtained with the
multibeam system at Parkes Observatory, we determine a metallicity of (O/H)
<0.46 solar at a confidence of 3 sigma. The metallicity of the high velocity
gas is consistent with either an extragalactic or Magellanic Cloud origin, but
is not consistent with a location inside the Milky Way unless the chemical
history of the gas is considerably different from that of the interstellar
medium in the Galactic disk and halo. Combined with measurements of highly
ionized species (C III and O VI) at high velocities, this metallicity limit
indicates that the cloud has a substantial halo of ionized gas; there is as
much ionized gas as neutral gas directly along the Ton S210 sight line. We
suggest several observational tests that would improve the metallicity
determination substantially and help to distinguish between possible origins
for the high velocity gas. Additional observations of this sight line would be
valuable since the number of compact HVCs positioned in front of background
sources bright enough for high resolution absorption-line studies is extremely
limited.


title: The EXPLORE Project I: A Deep Search for Transiting Extrasolar Planets

abstract:
  (Abridged) We discuss the design considerations of the EXPLORE (EXtra-solar
PLanet Occultation REsearch) project, a series of transiting planet searches
using 4-m-class telescopes to continuously monitor a single field of stars in
the Galactic Plane in each ~2 week observing campaign. We discuss the general
factors which determine the efficiency and the number of planets found by a
transit search, including time sampling strategy and field selection. The
primary goal is to select the most promising planet candidates for radial
velocity follow-up observations. We show that with very high photometric
precision light curves that have frequent time sampling and at least two
detected transits, it is possible to uniquely solve for the main parameters of
the eclipsing system (including planet radius) based on several important
assumptions about the central star. Together with a measured spectral type for
the star, this unique solution for orbital parameters provides a powerful
method for ruling out most contaminants to transiting planet candidates. For
the EXPLORE project, radial velocity follow-up observations for companion mass
determination of the best candidates are done on 8-m-class telescopes within
two or three months of the photometric campaigns. This same-season follow-up is
made possible by the use of efficient pipelines to produce high quality light
curves within weeks of the observations. We conclude by presenting early
results from our first search, EXPLORE I, in which we reached <1% rms
photometric precision (measured over a full night) on ~37,000 stars to I <=
18.2.


title:
The small-scale structure of magnetohydrodynamic turbulence with large
  magnetic Prandtl numbers

abstract:
  We study the intermittency and field-line structure of the MHD turbulence in
plasmas with very large magnetic Prandtl numbers. In this regime, which is
realized in the interstellar medium, some accretion disks, protogalaxies,
galaxy-cluster gas, early Universe, etc., magnetic fluctuations can be excited
at scales below the viscous cutoff. The salient feature of the resulting
small-scale magnetic turbulence is the folded structure of the fields. It is
characterized by very rapid transverse spatial oscillation of the field
direction, while the field lines remain largely unbent up to the scale of the
flow. Quantitatively, the fluctuation level and the field-line geometry can be
studied in terms of the statistics of the field strength and of the field-line
curvature. In the kinematic limit, the distribution of the field strength is an
expanding lognormal, while that of the field-line curvature K is stationary and
has a power tail K^{-13/7}. The field strength and curvature are
anticorrelated, i.e. the growing fields are mostly flat, while the sharply
curved fields remain relatively weak. The field, therefore, settles into a
reduced-tension state. Numerical simulations demonstrate three essential
features of the nonlinear regime. First, the total magnetic energy is equal to
the total kinetic energy. Second, the intermittency is partially suppressed
compared to the kinematic case, as the fields become more volume-filling and
their distribution develops an exponential tail. Third, the folding structure
of the field is unchanged from the kinematic case: the anticorrelation between
the field strength and the curvature persists and the distribution of the
latter retains the same power tail. We propose a model of back reaction based
on the folding picture that reproduces all of the above numerical results.


title: Properties of disks and spiral arms along the Hubble sequence

abstract:
  This paper presents some new statistical correlations between the properties
of disks and spiral arms with some physical properties of galaxies. Our results
show that the thickness of spiral disks tend to diminish along the Hubble
sequence in the sense that disks of Sc galaxies are 40% thinner than disks of
Sab-Sb galaxies. Moreover, the thinner disks tend also to be bluer. We also
find that there exists a correlation between HI linewidths and arm pattern
within each Hubble type, which suggests that the arm shape is partially
determined by the mass of a galaxy. Total mass luminosity ratios and total mass
surface densities also have correlations with pitch angles, i.e., for disks
with lower surface densities and lower total mass luminosity ratios, the pitch
angles tend to be greater.


title:
On the X-ray source luminosity distributions in the bulge and disk of
  M31: First results from XMM-Newton survey

abstract:
  We present luminosity distributions for the X-ray sources detected with
XMM-Newton in the bulge and disk of the Andromeda Galaxy (M31). The disk is
clearly lacking the brighter sources which dominate X-ray emission from the
bulge. This is the first convincing evidence for a difference between bulge and
disk X-ray populations in M31. Our results are in good qualitative agreement
with the luminosity distributions for low- and high-mass X-ray binaries
recently obtained by Grimm et al.(2001) for our Galaxy. This confirms that
X-ray population of the disk of M31 is dominated by fainter HMXB sources, while
the bulge is populated with brighter LMXBs.


title:
Cerenkov Line Emission as a Possible Mechanism of X-ray Lines in
  Gamma-ray Bursts

abstract:
  The recent discoveries of X-ray lines in the afterglows of gamma-ray bursts
(GRBs) provide significant clues to the nature of GRB progenitors and central
environments. However, the iron line interpretation by fluorescence or
recombination mechanism requires a large amount of iron material. We argue that
the very strong iron line could be attributed to an alternative mechanism:
Cerenkov line emission since relativistic electrons and dense medium exist near
GRB sites. Therefore, the broad iron lines are expected, and line intensity
will be nearly independent of the iron abundance, the medium with the
anomalously high Fe abundance is not required.


title: Mechanism of Magnetic Flux Loss in Molecular Clouds

abstract:
  We investigate the detailed processes working in the drift of magnetic fields
in molecular clouds. To the frictional force, whereby the magnetic force is
transmitted to neutral molecules, ions contribute more than half only at cloud
densities $n_{\rm H} < 10^4 {\rm cm}^{-3}$, and charged grains contribute more
than 90% at $n_{\rm H} > 10^6 {\rm cm}^{-3}$. Thus grains play a decisive role
in the process of magnetic flux loss. Approximating the flux loss time $t_B$ by
a power law $t_B \propto B^{-\gamma}$, where $B$ is the mean field strength in
the cloud, we find $\gamma \approx 2$, characteristic to ambipolar diffusion,
only at $n_{\rm H} < 10^7 {\rm cm}^{-3}$. At higher densities, $\gamma$
decreases steeply with $n_{\rm H}$, and finally at $n_{\rm H} \approx n_{\rm
dec} \approx {\rm a few} \times 10^{11} {\rm cm}^{-3}$, where magnetic fields
effectively decouple from the gas, $\gamma << 1$ is attained, reminiscent of
Ohmic dissipation, though flux loss occurs about 10 times faster than by Ohmic
dissipation. Ohmic dissipation is dominant only at $n_{\rm H} > 1 \times
10^{12} {\rm cm}^{-3}$. While ions and electrons drift in the direction of
magnetic force at all densities, grains of opposite charges drift in opposite
directions at high densities, where grains are major contributors to the
frictional force. Although magnetic flux loss occurs significantly faster than
by Ohmic dissipation even at very high densities as $n_{\rm H} \approx n_{\rm
dec}$, the process going on at high densities is quite different from ambipolar
diffusion in which particles of opposite charges are supposed to drift as one
unit.


title: X-ray Flashes from Off-axis Gamma-Ray Bursts

abstract:
  Ioka and Nakamura (2001) proposed a simple jet model that is compatible with
the peak luminosity-spectral lag relation, the peak luminosity-variability
relation and various other relations in the Gamma-Ray Bursts. If the viewing
angle is much larger than the collimation angle of the jet in the model by Ioka
and Nakamura, for appropriate model parameters we obtain the observational
characteristics of the X-ray flashes, such as the peak flux ratio and the
fluence ratio between the $\gamma$-ray (50-300 keV) and the X-ray band (2-10
keV), the X-ray photon index, the typical duration and the event rate $\sim 100
{\rm yr}^{-1}$. In our model, if the distance to the X-ray flashes is much
larger than $\sim 1$ Gpc (or $z \gtrsim 0.2$) they are too dim to be observed,
so the spatial distribution of the X-ray flashes should be homogeneous and
isotropic.


title: Quintessence or Phoenix?

abstract:
  We show that it is impossible to determine the state equation of quintessence
models on the basis of pure observational SNIa data. An independent estimate of
$\Omega_{M0}$ is necessary. Also in this most favourable case the situation can
be problematic.


title:
The role of the central stellar cluster in active galactic nuclei. I.
  Semi-analytical model

abstract:
  The subject of the paper is the role of the massive stellar cluster in the
activity phenomenon and in the structure of active galactic nuclei. We
introduce a simple model of stellar dynamics in the internal part of the
cluster, which allows us to include both the star-disk and the star-star
interactions. It is shown that the properties of the distribution of stars in
the vicinity of the black hole are determined both by the interaction of the
stars with the accretion disk and by the pair gravitational and contact
interaction between the stars. We calculate the distribution of stars in the
central parts of the cluster and we discuss possible effects of stellar
mass-loss due to the star-disk interaction. Finally, we study the implications
of the central cluster for active galactic nuclei activity. We model the broad
line region assuming that the gaseous wakes, following stars after each disk
crossing, play the role of the broad line region clouds, and we calculate the
corresponding line profiles. We also analyze the contribution of star-star and
star-disk collisions to active galactic nuclei variability.


title:
X-ray and optical observations of 1RXS J154814.5-452845: a new
  intermediate polar with soft X-ray emission

abstract:
  We report the identification of the ROSAT all-sky survey source 1RXS
J154814.5-452845as new intermediate polar and present the results from
follow-up optical and X-ray observations. The source shows pulsations with a
period of 693 s both in the optical and X-ray light curves and the detection of
a synodic frequency strongly suggests that this is the rotation period of the
white dwarf. Although the one day aliasing and the sparse optical data coverage
does not allow to unambiguously identify the orbital period, the most likely
values of 9.37 h and 6.72 h add 1RXS J154814.5-452845 to the intermediate
polars with the longest orbital periods known. The optical spectrum displays
features from the late type secondary and shows the presence of broad
absorption lines at \Hbet and higher order Balmer lines which may be a
signature of the white dwarf atmosphere, very similar to V 709 Cas. The average
X-ray spectra as obtained by the EPIC instruments on board XMM-Newton show hard
emission typical for this class of objects but also the presence of soft
blackbody-like emission similar to that seen from soft intermediate polars and
thought to arise from the white dwarf surface heated by the hard X-rays. The
best fit model comprises thermal emission from multi-temperature plasma in
collisional ionization equilibrium with a continuous temperature distribution
up to a maximum of $\sim$60 keV, an Fe fluorescence line at 6.4 keV and with
equivalent width of 260 eV and a blackbody component with kT of 86 eV. The hard
X-ray emission is absorbed by matter covering 47% of the X-ray source with an
equivalent hydrogen density of $\sim$\ohcm{23}. The remaining hard emission is
absorbed by a much reduced column density of 1.5\hcm{21} as is the soft
blackbody emission. (truncated)


title: The SSC XID Database

abstract:
  The XMM identification (XID) programme is accumulating Optical/IR data to
identify thousands of XMM sources at both high ($bII > 20^{\circ}$) and low
galactic latitude. X-ray sources are divided into samples on the basis of their
X-ray flux and their Galactic latitude. The XID Programme aims to identify and
classify around 1000 object in each sample. These in turn, will be used to
provide a basis for the statistical identification of the much larger pool of
serendipitous objects observed in XMM fields. The purpose of the XID database
is to underpin these projects by storing and connecting key information from
XMM XID fields and sources, together with (primarily) Optical/IR multi-colour
imaging and spectral data from the ground-based follow-up campaign. It should
shortly be able to serve as both a support tool for guiding the `ground-based`
effort, and permit collation and scientific exploitation of the results.


title: X-Ray Off States and Optical Variability in CAL 83

abstract:
  CAL 83 was one of the first supersoft X-ray binaries to be discovered and is
considered to be the prototype of its class. In 15 X-ray observations between
1983-1997 it was observed to have nearly constant X-ray luminosity and
temperature, with the exception of one off-state in 1996. We report on a second
X-ray off-state, discovered with a Chandra ACIS-S observation in November 1999.
Comparing the long-term X-ray and MACHO optical light curves, we find that, CAL
83 has exhibited distinct and well-defined low, intermediate, and high optical
states. Transitions between states are not accompanied by color variations.
Both X-ray off states were observed during optical high states and were
followed by optical low states within ~50 days. We discuss possible
explanations for the observed optical and X-ray variations.


title: Optical observations of the supernova remnant G 69.4+1.2

abstract:
  We performed deep optical observations of the area of the new supernova
remnant G 69.4+1.2 in the emission lines of [O III], Halpha+[N II] and [S II].
The low ionization images reveal diffuse and filamentary emission in the
central and south, south-west areas of our field. Estimates of the [S
II]/Halpha ratio suggest that the detected emission in these areas originates
from shock heated gas, while the strong extended source in the north must be an
HII region. The medium ionization image of [O III] shows a single filament
close to the field center. Emission from [O III] is not detected elsewhere in
the field but only in the north from LBN 069.96+01.35. Deep long-slit spectra
taken at the position of the [O III] filament suggest shock velocities ~120
km/s, while in other areas velocities around 50 km/s are expected. The sulfur
lines ratio indicates electron densities less than 120 cm^{-3}. The absolute
Halpha flux is ~5 x 10^{-17} erg s^{-1} cm^{-2} arcsec^{-2}. The optical
emission is very well correlated with the radio emission, especially in the
south west. The soft X-ray emission detected in the ROSAT All-Sky survey shows
a satisfactory degree of correlation with the optical data in the south-west
suggesting their association.


title: COMPTEL Observations of the Gamma-Ray Blazar PKS 1622-297

abstract:
  We report results of observations and analyses on the gamma-ray blazar PKS
1622-297, with emphasis on the COMPTEL data (0.75 - 30 MeV) collected between
April 1991 and November 1997. PKS 1622-297 was detected as a source of
gamma-rays by the EGRET experiment aboard CGRO in 1995 during a gamma-ray
outburst at energies above 100 MeV lasting for five weeks.
  In this time period the blazar was significantly (~ 5.9 sigma) detected by
COMPTEL at 10-30 MeV. At lower COMPTEL energies the detection is marginal,
resulting in a hard MeV spectrum.
  The combined COMPTEL/EGRET energy spectrum shows a break at MeV energies. The
broad-band spectrum (radio - gamma-rays) shows that the gamma-ray emission
dominates the overall power output. On top of the 5-week gamma-ray outburst,
EGRET detected a huge flare lasting for > 1 day. Enhanced MeV emission (10 - 30
MeV) is found near the time of this flare, suggesting a possible time delay
with respect to the emission above 100 MeV. Outside the 5-week flaring period
in 1995, we do not detect MeV emission from PKS 1622-297.


title: Initial conditions for quintessence after inflation

abstract:
  We consider the behaviour of a quintessence field during an inflationary
epoch, in order to learn how inflation influences the likely initial conditions
for quintessence. We use the stochastic inflation formalism to study quantum
fluctuations induced in the quintessence field during the early stages of
inflation, and conclude that these drive its mean to large values (> 0.1
m_{Planck}). Consequently we find that tracker behaviour typically starts at
low redshift, long after nucleosynthesis and most likely also after decoupling.


title:
First deep XMM-Newton observations of the LMC: Identifying LMC intrinsic
  source populations

abstract:
  The first X-ray survey of the Large Magellanic Cloud (LMC) was performed with
the Einstein satellite, revealing diffuse X-ray emission from hot gas and
discrete X-ray sources. The ROSAT observations between 1990 and 1998 supplied
the most sensitive survey with imaging instruments in the soft X-ray band (0.1
- 2.4 keV). The PSPC and HRI observations covered 59 square degrees of the LMC
and yielded a catalogue of about 1000 sources. Large efforts were undertaken to
identify and classify the X-ray sources according to the nature of their X-ray
emission. X-ray properties were used together with information from other
electro-magnetic wavelength bands to screen out foreground stars and background
objects from the LMC intrinsic X-ray source population which comprises X-ray
binaries, supernova remnants and supersoft sources. However, the vast majority
of sources still remains of unknown nature. First deep XMM-Newton observations
of selected regions in the LMC demonstrate a large step forward in the
identification of LMC X-ray sources. The large collecting area together with
imaging detectors covering energies 0.1 - 15 keV with far improved spectral
resolution allows to determine the nature of an object directly from the X-ray
properties down to low flux levels of a few 10$^{-14}$ erg cm$^{-2}$ s$^{-1}$.
First results of a deep observation north of LMC X-4 are presented, which
reveal the presence of new supernova remnants and X-ray binaries.


title: The extended atmosphere and evolution of the RV Tau star R Scuti

abstract:
  We analyze ISO/SWS spectra of the RV Tau star R Scuti. The infrared spectra
are dominated by H2O emission bands. The near- and mid-infrared excess is
attributed to H2O; the dust contribution is less important. We also identify
CO, SiO and CO2 bands. The various molecular emission bands originate from an
extended atmosphere, an atmosphere above the photosphere. The extended
atmosphere of R Sct is formed from matter which gradually have lifted up from
the photosphere through the pulsations of the star.
  In contrast to the abundant molecules around the star, the silicate dust
feature is weak and the dust mass-loss rate is only 10^{-11} solar mass per
year. This implies that there might be a process to inhibit dust formation from
molecules.
  RV Tau stars are commonly considered as post-AGB stars. While a detached dust
envelope around R Sct is consistent with such an interpretation, we show that
its period evolution is slower than expected. We argue that R Sct may be a
thermal-pulsing AGB star, observed in a helium-burning phase.


title: Spectral response of the EPIC-pn detector: basic dependences

abstract:
  One of the three cameras behind the X-ray telescopes on board XMM-Newton is
equipped with a pn CCD detector. Here the current status of the pn spectral
response calibration is summarized. Several parameters describing the spectral
response of the EPIC-pn detector show spatial dependencies. E.g. spectral
resolution and single- to double-pixel event ratios are functions of the charge
transfer losses and therefore depend on the distance to the read-out node of
the CCD (the RAWY detector coordinate).


title: The origin of [Fe II] emission in NGC 4151

abstract:
  The centre of NGC 4151 has been observed in the J-band with the SMIRFS
integral field unit (IFU) on the UK Infrared Telescope. A map of [Fe II]
emission is derived, and compared with the distributions of the optical narrow
line region and radio jet. We conclude that, because the [Fe II] emission is
associated more closely with the visible narrow-line region than with the radio
jet, it arises mainly through photoionization of gas by collimated X-rays from
the Seyfert nucleus. The velocity field and strength with respect to [Pa B] are
found to be consistent with this argument. The performance of the IFU is
considered briefly, and techniques for observation and data analysis are
discussed.


title: Waves and Instabilities in Accretion Disks: MHD Spectroscopic Analysis

abstract:
  A complete analytical and numerical treatment of all magnetohydrodynamic
waves and instabilities for radially stratified, magnetized accretion disks is
presented. The instabilities are a possible source of anomalous transport.
While recovering results on known hydrodynamicand both weak- and strong-field
magnetohydrodynamic perturbations, the full magnetohydrodynamic spectra for a
realistic accretion disk model demonstrates a much richer variety of
instabilities accessible to the plasma than previously realized. We show that
both weakly and strongly magnetized accretion disks are prone to strong
non-axisymmetric instabilities.The ability to characterize all waves arising in
accretion disks holds great promise for magnetohydrodynamic spectroscopic
analysis.


title:
Geometry and Kinematics in the Central Broad-Line Region of a Seyfert 1
  Galaxy

abstract:
  We recorded spectra of the highly variable Seyfert 1 galaxy Mrk110 in a
variability campaign with the 9.2m Hobby-Eberly Telescope at McDonald
Observatory in order to study the detailed line profile variations of the broad
emission lines. Here we show that only an AGN model predicting the formation of
the broad Hb line emission in the wind of an accretion disk matches the
observed 2-D variability pattern. Furthermore, we derive an improved mass of
the central supermassive black hole of M = 1.0(+1.0,-0.5)E7 M_sun from the Hb
velocity-delay map.


title:
Hubble Space Telescope Imaging of the Post-Starburst Quasar UN
  1025-0040: Evidence for Recent Star Formation

abstract:
  We present new Hubble Space Telescope (HST) WFPC2 images of the
post-starburst quasar UN J1025-0040, which contains both an active galactic
nucleus (AGN) and a 400-Myr-old nuclear starburst of similar bolometric
luminosity (10^{11.6} solar luminosities). The F450W and F814W images resolve
the AGN from the starburst and show that the bulk of the star light (6 x
10^{10} solar masses) is contained within a central radius of about 600
parsecs, and lacks clear morphological structures at this scale. Equating the
point-source light in each image with the AGN contribution, we determined the
ratio of AGN-to-starburst light. This ratio is 69% in the red F814W image,
consistent with our previous spectral analysis, but about 50% in the blue F450W
image whereas we had predicted 76%. The HST images are consistent with previous
photometry, ruling out variability (a fading AGN) as a cause for this result.
We can explain the new data if there is a previously unknown young stellar
population present, 40 Myr or younger, with as much as 10% of the mass of the
dominant 400-Myr-old population. This younger starburst may represent the
trigger for the current nuclear activity. The multiple starburst ages seen in
UN J1025-0040 and its companion galaxy indicate a complex interaction and
star-formation history.


title:
Constraining Strong Baryon-Dark Matter Interactions with Primordial
  Nucleosynthesis and Cosmic Rays

abstract:
  Self-interacting dark matter (SIDM) was introduced by Spergel & Steinhardt to
address possible discrepancies between collisionless dark matter simulations
and observations on scales of less than 1 Mpc. We examine the case in which
dark matter particles not only have strong self-interactions but also have
strong interactions with baryons. The presence of such interactions will have
direct implications for nuclear and particle astrophysics. Among these are a
change in the predicted abundances from big bang nucleosynthesis (BBN) and the
flux of gamma-rays produced by the decay of neutral pions which originate in
collisions between dark matter and Galactic cosmic rays (CR). From these
effects we constrain the strength of the baryon--dark matter interactions
through the ratio of baryon - dark matter interaction cross section to dark
matter mass, $s$. We find that BBN places a weak upper limit to this ratio $<
10^8 cm^2/g$. CR-SIDM interactions, however, limit the possible DM-baryon cross
section to $< 5 \times 10^{-3} cm^2/g$; this rules out an energy-independent
interaction, but not one which falls with center-of-mass velocity as $s \propto
1/v$ or steeper.


title: Constraints on the Bulk Lorentz Factor of GRB 990123

abstract:
  GRB 990123 was a long, complex gamma-ray burst accompanied by an extremely
bright optical flash. We present the collective constraints on the bulk Lorentz
factor for this burst based on estimates from burst kinematics, synchrotron
spectral decay, prompt radio flash observations, and prompt emission pulse
width. Combination of these constraints leads to an average bulk Lorentz factor
for GRB 990123 of Gamma_0=1000 +/- 100 which implies a baryon loading of
M_jet=8 (+17/-2) x 10^-8 Msolar. We find these constraints to be consistent
with the speculation that the optical light is emission from the reverse shock
component of the external shock. In addition, we find the implied value of
M_jet to be in accordance with theoretical estimates: the baryonic loading is
sufficiently small to allow acceleration of the outflow to Gamma > 100.


title: Particle Dark Matter Constraints from the Draco Dwarf Galaxy

abstract:
  It is widely thought that neutralinos, the lightest supersymmetric particles,
could comprise most of the dark matter. If so, then dark halos will emit radio
and gamma ray signals initiated by neutralino annihilation. A particularly
promising place to look for these indicators is at the center of the local
group dwarf spheroidal galaxy Draco, and recent measurements of the motion of
its stars have revealed it to be an even better target for dark matter
detection than previously thought. We compute limits on WIMP properties for
various models of Draco's dark matter halo. We find that if the halo is nearly
isothermal, as the new measurements indicate, then current gamma ray flux
limits prohibit much of the neutralino parameter space. If Draco has a moderate
magnetic field, then current radio limits can rule out more of it. These
results are appreciably stronger than other current constraints, and so
acquiring more detailed data on Draco's density profile becomes one of the most
promising avenues for identifying dark matter.


title: X-ray Point Sources in The Central Region of M31 as seen by Chandra

abstract:
  We report on \chandra observations of the central region of M31. By combining
eight \chandra ACIS-I observations taken between 1999 and 2001, we have
identified 204 X-ray sources within the central $\sim 17'\times17'$ region of
M31, with a detection limit of $\sim 2\times10^{35}$\lum. Of these 204 sources,
22 are identified with globular clusters, 2 with supernova remnants, 9 with
planetary nebula, and 9 as supersoft sources. By comparing individual images,
about 50% of the sources are variable on time scales of months. We also found
13 transients, with light curves showing a variety of shapes. We also extracted
the energy spectra of the 20 brightest sources; they can be well fit by a
single power-law with a mean photon index of 1.8. The spectral shapes of 12
sources are shown to be variable, suggesting that they went through state
changes. The luminosity function of all the point sources is consistent with
previous observations (a broken power-law with a luminosity break at
$1.7\times10^{37}$\lum). However, when the X-ray sources in different regions
are considered separately, different luminosity functions are obtained. This
indicates that the star-formation history might be different in different
regions.


title:
Chandra Observations of the Gravitational Potential Structure in Abell
  1060

abstract:
  We present results from a Chandra observation of Abell 1060, the nearby
cluster of galaxies. The ACIS-I image shows that the central cusp-like
structure, previously seen from PSPC, is caused mainly by an emission from the
central elliptical galaxy NGC 3311. We confirmed that the central region is
remarkably isothermal with a temperature of 3.2 keV, based on the spectral fits
for fine pixels. An extended region in the northeast of NGC 3311 indicates high
iron abundance. The surface brightness profile excluding the central galaxy,
NGC 3311, can be fitted only by a double beta model, with core radii about 40
and 140 kpc, out to a radius of about 200 kpc. This suggests that the
gravitational potential in Abell 1060 consists of 2 components.


title: Deep Ly-alpha imaging of two z=2.04 GRB host galaxy fields

abstract:
  We report on the results of deep narrow-band Ly-alpha, U and I imaging of the
fields of two GRBs at z=2.04 (GRB 000301C and GRB 000926). We find that the
host galaxy of GRB 000926 is an extended, strong Ly-alpha emitter with a
rest-frame equivalent width of 71+20-15 AA. The galaxy consists of two main
components and several fainter knots. GRB 000926 occurred in the western
component, whereas most of the Ly-alpha luminosity (about 65%) originates in
the eastern component. Using archival HST images of the host galaxy we measure
the spectral slopes (f_lambda prop. to lambda^beta) of the two components to
beta = -2.4+-0.3 (east) and -1.4+-0.2 (west). This implies that both components
contain at most small amounts of dust, consistent with the observed strong
Ly-alpha emission. The western component has a slightly redder V-I colour than
the eastern component, suggesting the presence of at least some dust. We do not
detect the host galaxy of GRB 000301C in neither Ly-alpha emission nor in U and
I-band images. We infer a limit of U(AB)>27.7 (2-sigma limit per arcsec^2). The
upper limits on the Ly-alpha flux implies a Ly-alpha equivalent width upper
limit of 150AA. We find 11 and 8 other galaxies with excess emission in the
narrow filter in the fields of GRB 000301C and GRB 000926 respectively. Based
on these detections we conclude that GRB 000926 occurred in one of the
strongest centres of star formation within several Mpc, whereas GRB 000301C
occurred in an intrinsically very faint galaxy far from being the strongest
centre of star formation in its galactic environment. Under the hypothesis that
GRBs trace star formation, the wide range of GRB host galaxy luminosities
implies a very steep faint end slope of the high redshift galaxy luminosity
function.


title: Accretion Flows in X-ray Binaries

abstract:
  I review the X-ray observations of Galactic accreting black holes and neutron
stars, and interpretions of these in terms of solutions of the accretion flow
equations.


title:
Kilo-Second Quasi-Periodic Oscillations in the Cataclysmic Variable DW
  Cancri

abstract:
  Our photometric monitoring revealed that DW Cnc, which was originally
classified as a dwarf nova (V=15--17.5), remained at a bright state of
Rc=14.68+/-0.07 for 61 days. In conjunction with optical spectra lacking a
strong He II emission line, we propose that the object is not a dwarf nova, but
a non-magnetic nova-like variable. Throughout our monitoring, the object showed
strong quasi-periodic oscillations (QPOs) with amplitudes reaching about 0.3
mag. Our period analysis yielded a power spectrum with two peaks of QPOs, whose
center periods are 37.5+/-0.1 and 73.4+/-0.4 min and, furthermore, with a
significant power in frequencies lower than the QPOs. DW Cnc is a unique
cataclysmic variable in which kilo-second QPOs were continuously detected for
61 days. We propose two possible interpretations of DW Cnc: (i) A permanent
superhumper below the period minimum of hydrogen-rich cataclysmic variables.
(ii) A nova-like variable having an orbital period over 3 hours. In this case,
the QPOs may be caused by trapped disk oscillations.


title:
Discovery of a Dwarf Nova Breaking the Standard Sequence of Compact
  Binary Evolution

abstract:
  We revealed that the dwarf nova 1RXS J232953.9+062814 is an SU UMa-type
system with a superhump period of 66.774+/-0.010 min. The short period strongly
indicates that the orbital period of this object is below the period minimum of
cataclysmic variables. The superhump period is 4.04+/-0.02 % longer than the
photometric period during quiescence (64.184+/-0.003 min), which is probably
associated with the orbital period. Although the standard evolutionary scenario
of cataclysmic variables predicts lower mass-transfer rates in systems with
shorter orbital periods, we revealed firm evidence of a relatively high
mass-transfer rate from its large proper motion and bright apparent magnitude.
Its proximity indicates that we have overlooked a number of objects in this new
class. With the analogous system of V485 Cen, these objects establish the first
subpopulation in hydrogen-rich cataclysmic variables below the period minimum.


title: The most distant structure of galaxies known: a protocluster at z=4.1

abstract:
  Imaging and spectroscopy with the Very Large Telescope have revealed 20
Lyman-alpha emitters within a projected distance of 1.3 Mpc and 600 km/s of the
luminous radio galaxy TN J1338-1942 at z=4.1. Compared to the field density of
Lyman-alpha emitters, this implies an overdensity on the order of 15. The
structure has a projected size of at least 2.7 Mpc x 1.8 Mpc and a velocity
dispersion of 325 km/s, which makes it the most distant structure known. Using
the galaxy overdensity and assuming a bias parameter b = 3 - 5, the mass is
estimated to be ~10^15 M_sun. The radio galaxy itself is surrounded by an
uniquely asymmetric Lyman-alpha halo. Taken together with our previous data on
PKS 1138-262 at z ~ 2.16, these results suggest that luminous radio sources are
excellent tracers of high density regions in the early Universe, which evolve
into present-day clusters. The statistics of bright radio sources and of
concentrations in the Lyman break galaxy population are consistent with the
picture that each of those concentrations harbours an active or passive
luminous radio source.


title: Estimating photometric redshifts with artificial neural networks

abstract:
  A new approach to estimating photometric redshifts - using Artificial Neural
Networks (ANNs) - is investigated. Unlike the standard template-fitting
photometric redshift technique, a large spectroscopically-identified training
set is required but, where one is available, ANNs produce photometric redshift
accuracies at least as good as and often better than the template-fitting
method. The Bayesian priors on the underlying redshift distribution are
automatically taken into account. Furthermore, inputs other than galaxy colours
- such as morphology, angular size and surface brightness - may be easily
incorporated, and their utility assessed.
  Different ANN architectures are tested on a semi-analytic model galaxy
catalogue and the results are compared with the template-fitting method.
Finally the method is tested on a sample of ~ 20000 galaxies from the Sloan
Digital Sky Survey. The r.m.s. redshift error in the range z < 0.35 is ~ 0.021.


title: Statistics of galaxy clustering

abstract:
  In this introductory talk we will establish connections between the
statistical analysis of galaxy clustering in cosmology and recent work in
mainstream spatial statistics. The lecture will review the methods of spatial
statistics used by both sets of scholars, having in mind the cross-fertilizing
purpose of the meeting series. Special topics will be: description of the
galaxy samples, selection effects and biases, correlation functions, nearest
neighbor distances, void probability functions, Fourier analysis, and structure
statistics.


title: Unusual Broad Absorption Line Quasars from the Sloan Digital Sky Survey

abstract:
  The Sloan Digital Sky Survey has confirmed the existence of populations of
broad absorption line (BAL) quasars with various unusual properties. We present
and discuss twenty-three such objects and consider the implications of their
wide range of properties for models of BAL outflows and quasars in general. We
have discovered one BAL quasar with a record number of absorption lines. Two
other similarly complex objects with many narrow troughs show broad MgII
absorption extending longward of their systemic host galaxy redshifts. This can
be explained as absorption of an extended continuum source by the
rotation-dominated base of a disk wind. Five other objects have absorption
which removes an unprecedented ~90% of all flux shortward of MgII. The
absorption in one of them has varied across the ultraviolet with an amplitude
and rate of change as great as ever seen. This same object may also show broad
H-beta absorption. Numerous reddened BAL quasars have been found, including at
least one reddened mini-BAL quasar with very strong FeII emission. The five
reddest objects have continuum reddenings of E(B-V)~0.5, and in two of them we
find strong evidence that the reddening curve is even steeper than that of the
SMC. We have found at least one object with absorption from FeIII but not FeII.
This may be due to a high column density of moderately high-ionization gas, but
the FeIII level populations must also be affected by some sort of resonance.
Finally, we have found two luminous, probably reddened high-redshift objects
which may be BAL quasars whose troughs partially cover different regions of the
continuum source as a function of velocity.


title: Retroactive Coherence

abstract:
  In gravitational microlensing, interference visibility is established when
the spectral resolution of the observation is less than the reciprocal of the
time delay difference. Using high resolutionspectroscopy fringes will be
visible at large path differences, even when the source emission is incoherent.
This is possible because coherence can be established after interference has
already occurred. Results of a laboratory test are presented which demonstrate
this retroactive establishment of coherence.


title: Unusually Weak Diffuse Interstellar Bands toward HD 62542

abstract:
  As part of an extensive survey of diffuse interstellar bands (DIBs), we have
obtained optical spectra of the moderately reddened B5V star HD 62542, which is
known to have an unusual UV extinction curve of the type usually identified
with dark clouds. The typically strongest of the commonly catalogued DIBs
covered by the spectra -- those at 5780, 5797, 6270, 6284, and 6614 A -- are
essentially absent in this line of sight, in marked contrast with other lines
of sight of similar reddening. We compare the HD 62542 line of sight with
others exhibiting a range of extinction properties and molecular abundances and
interpret the weakness of the DIBs as an extreme case of deficient DIB
formation in a dense cloud whose more diffuse outer layers have been stripped
away. We comment on the challenges these observations pose for identifying the
carriers of the diffuse bands.


title: The Halo Density Profiles with Non-Standard N-body Simulations

abstract:
  We propose a new numerical procedure to simulate a single dark halo of any
size and mass in a hierarchical framework coupling the extended Press-Schechter
formalism (EPSF) to N-body simulations. The procedure consists of assigning
cosmological initial conditions to the particles of a single halo with a EPSF
technique and following only the dynamical evolution using a serial N-body
code. The computational box is fixed with a side of $0.5 h^{-1}$ Mpc. This
allows to simulate galaxy cluster halos using appropriate scaling relations, to
ensure savings in computing time and code speed. The code can describe the
properties of halos composed of collisionless or collisional dark matter. For
collisionless Cold Dark Matter (CDM) particles the NFW profile is reproduced
for galactic halos as well as galaxy cluster halos. Using this numerical
technique we study some characteristics of halos assumed to be isolated or
placed in a cosmological context in presence of weak self-interacting dark
matter: the soft core formation and the core collapse. The self-interacting
dark matter cross section per unit mass is assumed to be inversely proportional
to the particle collision velocity: $\sigma/m_{x} \propto 1/v$.


title: A catalogue of dust clouds in the Galaxy

abstract:
  In this study 21 catalogues of dust clouds in the Galaxy were
cross-identified by taking into account available properties such as position,
angular dimensions, opacity class and velocity. An initial list of
$\approx$6500 entries was condensed into a cross-identified all-sky catalogue
containing 5004 dust clouds. In particular, the transition zone between high
and low Galactic latitude studies was also cross-identified. The unified
catalogue contains 525 high-latitude clouds. The catalogue deals primarily with
optical dark nebulae and globules, but it includes as well substantial
information from their molecular counterparts. Some previously uncatalogued
clouds were detected on optical images and FIR maps. Finally, we address recent
results and prospective work based on NIR imaging, especially for clouds
detected in the 2MASS $K_s$ Atlas.


title: Finding Black Holes with Microlensing

abstract:
  The MACHO and OGLE collaborations have argued that the three longest duration
bulge microlensing events are likely caused by nearby black holes, given the
small velocities measured with microlensing parallax and nondetection of the
lenses. However, these events may be due to lensing by more numerous lower mass
stars at greater distances. We find a posteriori probabilities of 76%, 16%, and
4% that the three longest events are black holes, assuming a Salpeter initial
mass function (IMF) and a 40 M cutoff for neutron star progenitors; the numbers
depend strongly on the assumed mass function but favor a black hole for the
longest event for most standard IMFs. The longest events (>600 days) have an a
priori 26% probability of being black holes for a standard mass function. We
propose a new technique for measuring the lens mass function using the mass
distribution of long events measured with the Advanced Camera for Surveys on
the Hubble Space Telescope, the Very Large Telescope Interferometer, the Space
Interferometry Mission, or the Global Astrometric Interferometer for
Astrophysics.


title: Fluxes of cosmic rays: A delicately balanced stationary state

abstract:
  The analysis of cosmic rays fluxes as a function of energy reveals a {\it
knee} slightly below $10^{16}$ eV and an {\it ankle} close to $10^{19}$ eV.
Their physical origins remain up to now quite enigmatic; in particular, no
elementary process is known which occurs at energies close to $10^{16}$ eV. We
propose a phenomenological approach along the lines of nonextensive statistical
mechanics, a formalism which contains Boltzmann-Gibbs statistical mechanics as
a particular case. The knee then appears as a crossover between two
fractal-like thermal regimes, the crossover being caused by process occurring
at energies ten million times lower than that of the knee, in the region of the
quark hadron transition ($\simeq 10^{9}$ eV). This opens the door to an
unexpected standpoint for further clarifying the phenomenon.


title: Combining cosmological datasets: hyperparameters and Bayesian evidence

abstract:
  A method is presented for performing joint analyses of cosmological datasets,
in which the weight assigned to each dataset is determined directly by it own
statistical properties. The weights are considered in a Bayesian context as a
set of hyperparameters, which are then marginalised over in order to recover
the posterior distribution as a function only of the cosmological parameters of
interest. In the case of a Gaussian likelihood function, this marginalisation
may be performed analytically. Calculation of the Bayesian evidence for the
data, with and without the introduction of hyperparameters, enables a direct
determination of whether the data warrant the introduction of weights into the
analysis; this generalises the standard likelihood ratio approach to model
comparison. The method is illustrated by application to the classic toy problem
of fitting a straight line to a set of data. A cosmological illustration of the
technique is also presented, in which the latest measurements of the cosmic
microwave background power spectrum are used to infer constraints on
cosmological parameters.


title:
The importance of neutrino opacities for the accretion luminosity in
  spherically symmetric supernova models

abstract:
  Based on general relativistic three-flavor Boltzmann neutrino transport, we
compare simulations of the postbounce evolution for five different stellar
progenitors with 13 and 20 solar masses (Nomoto & Hashimoto '88), and 15, 25,
and 40 solar masses (Woosley & Weaver '95).


title:
RR Lyrae Stars and Anomalous Cepheids in the Draco Dwarf Spheroidal
  Galaxy

abstract:
  We present new results on RR Lyrae stars and anomalous Cepheids in the Draco
dwarf spheroidal galaxy. We have increased the number of double-mode RR Lyrae
stars and found three new anomalous Cepheids. With period-magnitude and
period-amplitude diagrams, we discuss the Oosterhoff classification of Draco.
Contradictory results were found in that Draco appears to contain both
Oosterhoff I and II type RR Lyrae populations.


title: Orphan GRB radio afterglows: Candidates and constraints on beaming

abstract:
  The number of orphan radio afterglows associated with gamma-ray bursts (GRBs)
that should be detected by a flux limited radio survey, is calculated. It is
shown that for jetted GRBs this number is smaller for smaller jet opening angle
(theta), contrary to naive expectation. For a beaming factor
f_b^{-1}=(theta^2/2)^{-1} = 500, roughly the value inferred by Frail et al.
(2001) from analysis of afterglow light curves, we predict that between several
hundreds to several thousands orphan radio afterglows should be detectable
(over all sky) above 1 mJy at GHz frequencies at any given time. This orphan
population is dominated by sources lying at distances of a few hundred Mpc, and
having an age of ~1 yr. A search for point-like radio transients with flux
densities greater than 6 mJy was conducted using the FIRST and NVSS surveys,
yielding a list of 25 orphan candidates. We argue that most of the candidates
are unlikely to be radio supernovae. However, the possibility that they are
radio loud AGNs cannot be ruled out without further observations. Our analysis
sets an upper limit for the all sky number of radio orphans, which corresponds
to a lower limit f_b^{-1}>10 on the beaming factor. Rejection of all candidates
found in our search would imply f_b^{-1}>100. This, and the fact that some
candidates may indeed be radio afterglows, strongly motivate further
observations of these transients.


title:
The Ionized Gas and Nuclear Environment in NGC 3783. I. Time-Averaged
  900 ks Chandra Grating Spectroscopy

abstract:
  We present results from a 900 ks exposure of NGC 3783 with the High-Energy
Transmission Grating Spectrometer on board the Chandra X-ray Observatory. The
resulting X-ray spectrum has the best combination of signal-to-noise and
resolution ever obtained for an AGN. This spectrum reveals absorption lines
from H-like and He-like ions of N, O, Ne, Mg, Al, Si, and S. There are also
possible absorption lines from H-like and He-like Ar and Ca. We also identify
inner-shell absorption from lower-ionization ions such as Si_VII-Si_XII and
S_XII-S_XIV. The iron absorption spectrum is very rich; L-shell lines of
Fe_XVII-Fe_XXIV are detected, strong complex of M-shell lines, and probable
resonance lines from Fe_XXV. The absorption lines are blueshifted relative to
the systemic velocity by a mean velocity of -590+-150 km/s. We resolve many of
the absorption lines, and their mean FWHM is 820+-280 km/s. We do not find
correlations between the velocity shifts or the FWHMs with the ionization
potentials of the ions. Most absorption lines show asymmetry, having more
extended blue wings than red wings. In O_VII we have resolved this asymmetry to
be from an additional absorption system at ~ -1300 km/s. The two X-ray
absorption systems are consistent in velocity shift and FWHM with the ones
identified in the UV lines of C IV, N V, and H I. Equivalent width measurements
for all lines are given and column densities are calculated for several ions.
We resolve the narrow Fe_K\alpha line at 6398.2+-3.3 eV to have a FWHM of
1720+-360 km/s, which suggests that this narrow line may be emitted from the
outer part of the broad line region or the inner part of the torus. We also
detect a `Compton shoulder' redward of the narrow Fe_K\alpha line which
indicates that it arises in cold, Compton-thick gas.


title: Structure in the Dusty Debris around Vega

abstract:
  We present images of the Vega system obtained with the IRAM Plateau de Bure
interferometer at 1.3 millimeters wavelength with sub-mJy sensitivity and
$\sim2\farcs5$ resolution (about 20 AU). These observations clearly detect the
stellar photosphere and two dust emission peaks offset from the star by
$9\farcs5$ and $8\farcs0$ to the northeast and southwest, respectively. These
offset emission peaks are consistent with the barely resolved structure visible
in previous submillimeter images, and they account for a large fraction of the
dust emission. The presence of two dust concentrations at the observed
locations is plausibly explained by the dynamical influence of an unseen planet
of a few Jupiter masses in a highly eccentric orbit that traps dust in
principle mean motion resonances.


title: The temperature dependence of equilibrium plasma density

abstract:
  Temperature dependence of an electron-nuclear plasma equilibrium density is
considered basing on known approaches, which are given in (1)(2). It is shown
that at a very high temperature, which is characteristic for a star interior,
the equilibrium plasma density is almost constant and equals approximately to
$10^{25}$ particles per $cm^3$. At a relatively low temperature, which is
characteristic for star surface, the equilibrium plasma density is in several
orders lower and depends on temperature as $T^{3/2}$.


title: On the Population of Wind-Accreting Neutron Stars in the Galaxy

abstract:
  We explore the possibility that neutron stars accreting from the winds of
main-sequence stellar companions account for a significant fraction of
low-luminosity, hard X-ray sources (L_X <~ 10^35 ergs/s; 1-10 keV) in the
Galaxy. This work was motivated by recent Chandra observations of the Galactic
center by Wang et al. (2002). Our calculations indicate that many of the
discrete X-ray sources detected in this survey may be wind-accreting neutron
stars, and that many more may be discovered with deeper X-ray observations. We
propose that an infrared observing campaign be undertaken to search for the
stellar counterparts of these X-ray sources.


title: Dark matter, dark charge, and the fractal structure of the Universe

abstract:
  It is shown that the observed fractal distribution of galaxies is, in fact,
consistent with homogeneity of the Universe and observational limits on $
\Delta T/T$, if the presence of dark matter and dark charge predicted by the
Modified Field Theory (MOFT) is taken into account. It is also shown that
indeed in MOFT the ground state for baryons does correspond to the fractal
distribution of baryons with dimension D=2. It is discussed a new scenario of
structure formation in which observed structures appear as a result of decay of
the primordial fractal distribution of baryons.


title:
SZ and X-ray combined analysis of a distant galaxy cluster, RX
  J2228+2037

abstract:
  We have performed a combined analysis of X-ray and Sunyaev-Zel'dovich data in
the direction of the distant galaxy cluster, RX J2228+2037. Fitting a
$\beta$-model to the high-resolution HRI data gives $r_c = 103 \pm 12
h_{70}^{-1}$ kpc and $\beta=0.54 \pm 0.03$. The dependency of the
Sunyaev-Zel'dovich effect with respect to the gas temperature allows us,
through the additional use of the 21 GHz data of the cluster, to determine $k_B
T_e=10.4 \pm 1.8 h_{70}^{1/2}$ keV. Extrapolating the gas density profile out
to the virial radius ($R_v=r_{178}=2.9$ Mpc), we derived a gas mass of
$M_{g}(r<R_v)=(4.0\pm 0.2)\times 10^{14} h_{70}^{-5/2} \rm{M}_\odot$. Within
the hypothesis of hydrostatic equilibrium, the corresponding extrapolated total
mass for this source is: $M_{tot}(r<R_v)=(1.8 \pm 0.4)\times 10^{15} h^{-1}
\rm{M}_\odot$, which corresponds to a gas fraction of $f_{gas}=0.22\pm 0.06
h_{70}^{-3/2}$. Our results on the temperature and on the cluster mass classify
RX J2228+2037 among the distant, hot and very massive galaxy clusters. Our work
highlights the power of the association of galaxy cluster mapping observations
in X-ray and the SZ effect to derive the cluster's physical properties, even
without X-ray spectroscopy.


title: HI Fluctuations at Large Redshifts: I--Visibility correlation

abstract:
  We investigate the possibility of probing the large scale structure in the
universe at large redshifts by studying fluctuations in the redshifted 1420 MHz
emission from the neutral hydrogen (HI) at early epochs. The neutral hydrogen
content of the universe is known from absorption studies for z<4.5. The HI
distribution is expected to be inhomogeneous in the gravitational instability
picture and this inhomogeneity leads to anisotropy in the redshifted HI
emission. The best hope of detecting this anisotropy is by using a large
low-frequency interferometric instrument like the Giant Meter-Wave Radio
Telescope (GMRT). We calculate the visibility correlation function <V_nu(u)
V_nu'(u)> at two frequencies nu and nu' of the redshifted HI emission for an
interferometric observation. In particular we give numerical results for the
two GMRT channels centered around nu =325 and 610 MHz from density
inhomogeneity and peculiar velocity of the HI distribution. The visibility
correlation is ~10^-9 to 10^-10 Jy^2. We calculate the signal-to-noise for
detecting the correlation signal in the presence of system noise and show that
the GMRT might detect the signal for integration times ~ 100 hrs. We argue that
the measurement of visibility correlation allows optimal use of the
uncorrelated nature of the system noise across baselines and frequency
channels.


title:
XMM-Newton Detection of Hard X-ray Emission in the Nitrogen-Type
  Wolf-Rayet Star WR110

abstract:
  We have used the excellent sensitivity of XMM-Newton to obtain the first
high-quality X-ray spectrum of a Wolf-Rayet (WR) star which is not known to be
a member of a binary system. Our target, the nitrogen-type star WR 110 (= HD
165688) was also observed and detected with the VLA at four different
frequencies. The radio data are in excellent agreement with that expected for
free-free wind emission. and the ionized mass-loss rate is derived. The X-ray
emission measure distribution shows a dominant contribution from cool plasma at
kT$_{cool}$ = 0.5 keV (6 MK) which is only weakly absorbed. We argue that this
cool emission originates at hundreds of radii if the wind is spherical and
homogeneous and derive shock velocities and the X-ray filling factor using
radiative shock models. A surprising result is the unambiguous detection of a
hard X-ray component clearly seen in the hard-band images and the spectra. This
hard component accounts for about half of the observed flux and can be
acceptably fitted by a hot optically thin thermal plasma or a power-law model.
If the emission is thermal, then a temperature kT$_{hot}$ $\geq$ 3 keV is
derived. Such high temperatures are not predicted by current instability-driven
wind shock models. We examine several alternatives and show that the hard
emission could be accounted for by the WR wind shocking onto a close stellar
companion which has so far escaped detection. However, until persuasive
evidence for binarity is found we are left with the intriguing possibility that
the hard X-ray emission is produced entirely by the Wolf-Rayet star.


title:
1E 1207.4-5209: The puzzling pulsar at the center of the PKS 1209-51/52
  supernova remnant

abstract:
  Second Chandra observation of 1E 1207.4-5209, the central source of the
supernova remnant PKS 1209-51/52, allowed us to confirm the previously detected
period of 424 ms and, assuming a uniform spin-down, estimate the period
derivative, Pdot (0.7-3)e-14 s/s. The corresponding characteristic age of the
pulsar, P/2Pdot~200-900 kyr, is much larger than the estimated age of the SNR,
\~7 kyr. The values of the spin-down luminosity, Edot (0.4-1.6)e34 erg/s, and
conventional magnetic field, B (2-4)e12 G, are typical for a middle-aged radio
pulsar, although no manifestations of pulsar activity have been observed. If 1E
1207.4-5209 is indeed the neutron star formed in the same supernova explosion
that created PKS 1209-51/52, such a discrepancy in ages could be explained
either by a long initial period, close to its current value, or, less likely,
by a very large braking index of the pulsar. Alternatively, the pulsar could be
a foreground object unrelated to the supernova remnant, but the probability of
such a coincidence is very low.


title: Observational Constraints on Dark Radiation in Brane Cosmology

abstract:
  We analyze the observational constraints on brane-world cosmology whereby the
universe is described as a three-brane embedded in a five-dimensional anti-de
Sitter space.
  In this brane-universe cosmology, the Friedmann equation is modified by the
appearance of extra terms which derive from existence of the extra dimensions.
  In the present work we concentrate on the ``dark radiation'' term which
diminishes with cosmic scale factor as $a^{-4}$.
  We show that, although the observational constraints from primordial
abundances allow only a small contribution when this term is positive, a much
wider range of negative values is allowed. Furthermore, such a negative
contribution can reconcile the tension between the observed primordial $\he4$
and D abundances.
  We also discuss the possible constraints on this term from the power spectrum
of CMB anisotropies in the limit of negligible cosmological perturbation on the
brane world. We show that BBN limits the possible contribution from dark
radiation just before the nucleosynthesis epoch to lie between -65% and $+5%$
of the background photon energy density. Combining this with the CMB constraint
reduces this range to between -24% and $+3.5%$ at the $2\sigma$ confidence
level.


title:
Large Scale Magnetic Fields and the Number of Cosmic Ray Sources above
  10^(19) eV

abstract:
  We present numerical simulations for the two-point correlation function and
the angular power spectrum of nucleons above 10^{19} injected by a discrete
distribution of sources following a simple approximation to the profile of the
Local Supercluster. We develop a method to constrain the number of sources
necessary to reproduce the observed sky distribution of ultra-high energy
cosmic rays, as a function of the strength of the large scale cosmic magnetic
fields in the Local Supercluster. While for fields B < 0.05 micro Gauss the
Supercluster source distribution is inconsistent with the data for any number
of sources, fields of strength B~0.3 micro Gauss could reproduce the observed
data with a number of sources around 10.


title: Stable Models of Elliptical Galaxies

abstract:
  We construct stable axially symmetric models of elliptical galaxies. The
particle density on phase space for these models depends monotonically on the
particle energy and on the third component of the angular momentum. They are
obtained as minimizers of suitably defined energy-Casimir functionals, and this
implies their nonlinear stability. Since our analysis proceeds from a rigorous
but purely mathematical point of view it should be interesting to determine if
any of our models match observational data in astrophysics. The main purpose of
these notes is to initiate some exchange of information between the
astrophysics and the mathematics communities.


title: X-Ray Spectroscopy of Gamma-Ray Bursts

abstract:
  Observational evidence of iron absorption and emission lines in X-ray spectra
of Gamma-Ray Bursts is quite compelling. I will briefly review the results,
summarize different models and describe the connection with massive progenitors
in star-forming regions implied by these results. This link is also supported
by measurements of the X-ray absorbing gas in several GRB's, with column
density consistent with that of Giant Molecular Clouds harbouring
star-formation in our Galaxy, as well as by evidences gathered in other
wavelengths. However, the volume density inferred by the fireball-jet model is
much lower than typical of a GMC, and I will confront this with the alternative
explanation of fireball expansion in a high dense medium, outlining the
problems that both models have at present. Finally I will briefly summarize
some results on dark GRB's, and describe the prospects of high resolution X-ray
spectroscopy in getting closer to the central environment of GRB, and far in
the Early Universe by using GRB as beacons to probe star and galaxy formation.