title:
Re-analysis of VLT Data for M83 with Image Subtraction -- Nine-fold
  Increase in Number of Cepheids

abstract:
  We apply the image subtraction method to re-analyze the ESO Very Large
Telescope data on M83 (NGC 5236), obtained and analyzed by Thim et al. Whereas
Thim et al. found 12 Cepheids with periods between 12-55 days, we find 112
Cepheids with periods ranging from 7-91 days, as well as ~60 other variables.
These include 2 candidate eclipsing binaries, which, if confirmed, would be the
first optically discovered outside the Local Group. We thus demonstrate that
the image subtraction method is much more powerful for detecting variability,
especially in crowded fields. However, HST observations are necessary to obtain
a Cepheid period-luminosity distance not dominated by blending and crowding. We
propose a ``hybrid'' approach, where numerous Cepheids are discovered and
characterized using large ground-based telescopes and then followed-up with the
HST to obtain precise distances.


title: Planck-Kerr Turbulence

abstract:
  A quantum gravitational instability is identified at Planck scales between
non-spinning extreme Schwarzschild black holes and spinning extreme Kerr black
holes, which produces a turbulent Planck particle gas. Planck inertial vortex
forces balance gravitational forces as the Planck turbulence cascades to larger
scales and the universe expands and cools. Turbulent mixing of temperature
fluctuations and viscous dissipation of turbulent kinetic energy provide
irreversibilities necessary to sustain the process to the strong force freeze
out temperature where inflation begins. Turbulent temperature fluctuations are
fossilized when they are stretched by inflation beyond the horizon scale of
causal connection. As the horizon of the expanding universe grows, the
fluctuations seed patterns of nucleosynthesis, and these seed the formation of
structure in the plasma epoch. Fossil big bang turbulence is supported by
extended self similarity coefficients computed for cosmic microwave background
temperature anisotropies that match those for high Reynolds number turbulence.


title: The OGLE-II event sc5_2859 -- An example of disk-disk microlensing

abstract:
  We present a new long-duration parallax event from the OGLE-II database,
sc5_2859, which has the second longest time-scale ever identified (tE =
547.6{+22.6}{-7.8} days). We argue that both the lens and source reside in the
Galactic disk, making event sc5_2859 one of the first confirmed examples of
so-called disk-disk microlensing. We find that the source star is most probably
located at a distance of D_S ~ 2 kpc, and from this we conclude that the lens
is unlikely to be a main-sequence star due to the strict limits that can be
placed on the lens brightness. A simple likelihood analysis is carried out on
the lens mass, which indicates that the lens could be another candidate stellar
mass black hole. We recommend that spectroscopic observations of the source be
carried out in order to constrain the source distance, since this is the main
source of uncertainty in our analysis. In addition, we briefly discuss whether
there appears to be an excess of long duration microlensing events in the
OGLE-II catalogue.


title: Radio and X-ray observations of the jet in Centaurus A

abstract:
  We present new, high dynamic range VLA images of the inner jet of the closest
radio galaxy, Centaurus A. Over a ten-year baseline we detect apparent
sub-luminal motions (v ~ 0.5c) in the jet on scales of hundreds of pc. The
inferred speeds are larger than those previously determined using VLBI on
smaller scales, and provide new constraints on the angle made by the jet to the
line of sight if we assume jet-counterjet symmetry. The new images also allow
us to detect faint radio counterparts to a number of previously unidentified
X-ray knots in the inner part of the jet and counterjet, showing conclusively
that these X-ray features are genuinely associated with the outflow. However,
we find that the knots with the highest X-ray to radio flux density ratios do
not have detectable proper motions, suggesting that they may be related to
standing shocks in the jet; we consider some possible internal obstacles that
the jet may encounter. Using new, high-resolution Chandra data, we discuss the
radio to X-ray spectra of the jet and the discrete features that it contains,
and argue that the compact radio and X-ray knots are privileged sites for the
in situ particle acceleration that must be taking place throughout the jet. We
show that the offsets observed between the peaks of the radio and X-ray
emission at several places in the Cen A jet are not compatible with the
simplest possible models involving particle acceleration and downstream
advection together with synchrotron and expansion losses.


title: Cooling flows or warming rays?

abstract:
  The radiative cooling time of the X-ray-emitting plasma near the center in
many clusters of galaxies is shorter than the age of the cluster, but neither
the expected large drop in central temperature --nor the expected mass flow
towards the pressure-depleted cluster centers-- are observed. We propose a
solution to these ``cooling flow'' problems wherein energy is supplied to the
plasma by hadronic cosmic rays (CRs). The solution requires an energy
deposition more intense and more distributed than in conventional CR models,
but this alternative model is also successful in describing the origin of CRs,
as well as the properties of gamma ray bursts and of the diffuse gamma
background radiation. The X-ray energy emitted by clusters is supplied, in a
quasi-steady state, by the hadronic CRs, which act as ``warming rays''. The
temperature distribution in the intracluster space is successfully predicted
from the measured plasma-density distribution. Four other puzzling features of
clusters can also be explained in simple terms: the discrepancy between their
``virial'' and ``lensing'' masses, their large magnetic fields, the correlation
between their optical and X-ray luminosities, and the non-thermal tail of their
X-ray spectrum.


title:
Some Constraints On the Effects of Age and Metallicity on the Low Mass
  X-ray Binary Formation Rate

abstract:
  We have studied the low mass X-ray binary (LMXB) populations within and
outside globular clusters (GC) in NGC 4365 and NGC 3115. Using published age
and metallicity constraints from optical and IR observations of their GCs, we
do not find any evidence for an increase in the LMXB formation rate in the
intermediate age cluster population of NGC 4365, as has been proposed in some
scenarios of dynamical LMXB formation in GCs. The old, metal-rich, red
population of GCs in NGC 3115 on the other hand is {\it at least} three times
as efficient at creating LMXBs as the old, metal-poor, blue clusters. These
data suggest that the higher formation efficiency of LMXBs in the red GC
subsystems of many galaxies is largely a consequence of their higher
metallicity. A comparison of the densities of field LMXBs in different galaxies
does not reveal an obvious correlation with the age of the field stars as
predicted by models in which the LMXB formation rate in the field drops
monotonically with time after an initial burst. This suggests that either a
significant fraction of the field LMXBs are created in GCs and subsequently
injected into the field, or the LMXB formation rate has a more complex time
evolution pattern.


title:
Effect of realistic astrophysical inputs on the phase and shape of the
  WIMP annual modulation signal

abstract:
  The orbit of the Earth about the Sun produces an annual modulation in the
WIMP direct detection rate. If the local WIMP velocity distribution is
isotropic then the modulation is roughly sinusoidal with maximum in June,
however if the velocity distribution is anisotropic the phase and shape of the
signal can change. Motivated by conflicting claims about the effect of
uncertainties in the local velocity distribution on the interpretation of the
DAMA annual modulation signal (and the possibility that the form of the
modulation could be used to probe the structure of the Milky Way halo), we
study the dependence of the annual modulation on various astrophysical inputs.
We first examine the approximations used for the Earth's motion about the Sun
and the Sun's velocity with respect to the Galactic rest frame. We find that
overly simplistic assumptions lead to errors of up to ten days in the phase and
up to tens of per-cent in the shape of the signal, even if the velocity
distribution is isotropic. Crucially, if the components of the Earth's velocity
perpendicular to the motion of the Sun are neglected, then the change in the
phase which occurs for anisotropic velocity distributions is missed. We then
examine how the annual modulation signal varies for physically and
observationally well-motivated velocity distributions. We find that the phase
of the signal changes by up to 20 days and the mean value and amplitude change
by up to tens of per-cent.


title: On the Origin of Intracluster Entropy

abstract:
  The entropy distribution of the intracluster medium and the shape of its
confining potential well completely determine the X-ray properties of a relaxed
cluster of galaxies, motivating us to explore the origin of intracluster
entropy and to describe how it develops in terms of some simple models. We
present an analytical model for smooth accretion, including both preheating and
radiative cooling, that links a cluster's entropy distribution to its mass
accretion history and shows that smooth accretion overproduces the entropy
observed in massive clusters by a factor ~2-3, depending on the mass accretion
rate. Any inhomogeneity in the accreting gas reduces entropy production at the
accretion shock; thus, smoothing of the gas accreting onto a cluster raises its
entropy level. Because smooth accretion produces more entropy than hierarchical
accretion, we suggest that some of the observed differences between clusters
and groups may arise because preheating smooths the smaller-scale lumps of gas
accreting onto groups more effectively than it smooths the larger-scale lumps
accreting onto clusters. This effect may explain why entropy levels at the
outskirts of groups are ~2-3 times larger than expected from self-similar
scaling arguments. The details of how the density distribution of accreting gas
affects the entropy distribution of a cluster are complex, and we suggest how
to explore the relevant physics with numerical simulations.


title: Neutrinos from the Propagation of a Relativistic Jet Through a Star

abstract:
  We discuss the neutrino signature of a relativistic jet propagating through a
stellar envelope, a scenario realized in the collapsar model for Gamma Ray
Bursts (GRBs). It is shown that the dramatic slowing of the jet deep within the
star is accompanied by inelastic neutron-nucleon collisions and the conversion
of a substantial fraction of the jet kinetic energy to neutrinos. These
neutrinos have observed energies in the range two to tens of GeV and an
estimated detection rate comparable to or larger than the detection rate of GeV
neutrinos from other GRB-related processes. The time delay between the arrival
of these neutrinos and the GRB photons is tens of seconds. An observation of
this delay would provide an indication that the GRB jet originated in a massive
star.


title: The K Band Luminosity Function of High Redshift Clusters

abstract:
  K band observations of the galaxy populations of three high redshift
(z=0.8-1.0), X-ray selected, massive clusters are presented. The observations
reach a depth of K = 21.5, corresponding to K*+3.5 mag. The evolution of the
galaxy properties are discussed in terms of their K band luminosity functions
and the K band Hubble diagram of brightest cluster galaxies.
  The bulk of the galaxies, as characterised by the parameter K* from the
Schechter (1976) function, are found to be consistent with passive evolution
with a redshift of formation of z_f = 1.5-2. This is in agreement with
observations of other high redshift clusters, but in disagreement with field
galaxies at similar redshifts. The shape of the luminosity function at high
redshift, after correcting for passive evolution, is not significantly
different from that of the Coma cluster, again consistent with passive
evolution.


title: Surface Outflow in Optically Thick Dust Disks by the Radiation Pressure

abstract:
  We study the outflow of dust particles on the surface layers of optically
thick disks. At the surface of disks around young stars, small dust particles
(size < 10 micron) experience stellar radiation pressure support and orbit more
slowly than the surrounding gas. The resulting tail-wind imparts energy and
angular momentum to the dust particles, moving them outward. This outflow
occurs in the thin surface layer of the disk that is exposed to starlight, and
the outward mass flux is carried primarily by particles of size ~0.1 micron.
Beneath the irradiated surface layer, dust particles experience a head-wind,
which drives them inward. For the specific case of a minimum-mass-solar-nebula,
less than a thousandth of the dust mass experiences outward flow. If the
stellar luminosity is 15 times brighter than the sun, however, or if the gas
disk mass is as small as ~100 M_earth, then the surface outflow can dominate
the inward flux in certain radial ranges, leading to the formation of rings or
gaps in the dust disks.


title:
From linear to non-linear scales: analytical and numerical predictions
  for the weak lensing convergence

abstract:
  Weak lensing convergence can be used directly to map and probe the dark mass
distribution in the universe. Building on earlier studies, we recall how the
statistics of the convergence field are related to the statistics of the
underlying mass distribution, in particular to the many-body density
correlations. We describe two model-independent approximations which provide
two simple methods to compute the probability distribution function, pdf, of
the convergence. We apply one of these to the case where the density field can
be described by a log-normal pdf. Next, we discuss two hierarchical models for
the high-order correlations which allow one to perform exact calculations and
evaluate the previous approximations in such specific cases. Finally, we apply
these methods to a very simple model for the evolution of the density field
from linear to highly non-linear scales. Comparisons with the results obtained
from numerical simulations, obtained from a number of different realizations,
show excellent agreement with our theoretical predictions. We have probed
various angular scales in the numerical work and considered sources at 14
different redshifts in each of two different cosmological scenarios, an open
cosmology and a flat cosmology with non-zero cosmological constant. Our
simulation technique employs computations of the full 3-d shear matrices along
the line of sight from the source redshift to the observer and is complementary
to more popular ray-tracing algorithms. Our results therefore provide a
valuable cross-check for such complementary simulation techniques, as well as
for our simple analytical model, from the linear to the highly non-linear
regime.


title:
An H-alpha survey aiming at the detection of extraplanar diffuse ionized
  gas in halos of edge-on spiral galaxies. I. How common are gaseous halos
  among non-starburst galaxies?

abstract:
  In a series of two papers we present results of a new H-alpha imaging survey,
aiming at the detection of extraplanar diffuse ionized gas in halos of
late-type spiral galaxies. We have investigated a sample of 74 nearby edge-on
spirals, covering the northern and southern hemisphere. In 30 galaxies we
detected extraplanar diffuse emission at mean distances of |z|~1-2 kpc.
Individual filaments can be traced out to |z|<= 6 kpc in a few cases. We find a
good correlation between the FIR flux ratio (S_60/S_100) and the SFR per unit
area (L_FIR/D^2_25), based on the detections/non-detections. This is actually
valid for starburst, normal and for quiescent galaxies. A minimal SFR per unit
area for the lowest S_60/S_100 values, at which extended emission has been
detected, was derived, which amounts to (dE/dt)_A25^thres = (3.2+-0.5)x10E+40
erg/s/kpc^2. There are galaxies where extraplanar emission was detected at
smaller values of L_FIR/D^2_25, however, only in combination with a
significantly enhanced dust temperature. The results corroborate the general
view that the gaseous halos are a direct consequence of SF activity in the
underlying galactic disk.


title: Clusters in the Zone of Avoidance

abstract:
  The Clusters in the Zone of Avoidance (CIZA) project is producing the first
statistically complete catalogue of X-ray selected galaxy clusters behind the
Galactic plane. Current optically selected cluster catalogues have excluded a
wide band of sky centered on the Milky Way (|b| < 20 deg) due to the high
extinction and stellar obscuration at low Galactic latitudes. An X-ray search
for cluster candidates overcomes the problems faced by optically selected
catalogues, hence providing the first opportunity to explore the sky in the
traditional Zone of Avoidance; principally, the Great Attractor region. When
added to other X-ray selected cluster surveys such as the BCS and REFLEX, CIZA
will complete the first unbiased, all-sky cluster catalogue. We here report on
the progress of the CIZA survey as well as preliminary results of a dipole
analysis which utilizes the current CIZA sample.


title: Secular Evolution of Hierarchical Planetary Systems

abstract:
  (Abridged) We investigate the dynamical evolution of coplanar hierarchical
two-planet systems where the ratio of the orbital semimajor axes alpha=a_1/a_2
is small. The orbital parameters obtained from a multiple Kepler fit to the
radial velocity variations of a star are best interpreted as Jacobi coordinates
and Jacobi coordinates should be used in any analyses of hierarchical planetary
systems. An approximate theory that can be applied to coplanar hierarchical
two-planet systems with a wide range of masses m_j and orbital eccentricities
e_j is the octupole-level secular perturbation theory (OSPT). The OSPT shows
that if the ratio of the maximum orbital angular momenta, lambda \approx
(m_1/m_2) alpha^{1/2}, for given a_j is approximately equal to a critical value
lambda_{crit}, then libration of the difference in the longitudes of periapse,
w_1-w_2, about either 0 or 180 deg. is almost certain, with possibly large
amplitude variations of both e_j. We establish that the OSPT is highly accurate
for systems with alpha<0.1 and reasonably accurate even for systems with alpha
as large as 1/3, provided that alpha is not too close to a significant
mean-motion commensurability or above the stability boundary. The HD 168443
system is not in a secular resonance and its w_1-w_2 circulates. The HD 12661
system is the first extrasolar planetary system found to have w_1-w_2 librating
about 180 deg. The libration of w_1-w_2 and the large-amplitude variations of
both e_j in the HD 12661 system are consistent with the analytic results on
systems with lambda \approx lambda_{crit}. The HD 12661 system with the best-
fit orbital parameters and sin i = 1 is affected by the close proximity to the
11:2 commensurability, but small changes in the outer orbital period can result
in configurations that are not affected by mean-motion commensurabilities.


title: Minkowski Functionals of SDSS galaxies I : Analysis of Excursion Sets

abstract:
  We present a first morphometric investigation of a preliminary sample from
the SDSS of 154287 galaxies with apparent magnitude 14.5<m_r<17.5 and redshift
0.001<z<0.4. We measure the Minkowski Functionals, which are a complete set of
morphological descriptors. To account for the complicated wedge--like geometry
of the present survey data, we construct isodensity contour surfaces from the
galaxy positions in redshift space and employ two complementary methods of
computing the Minkowski Functionals. We find that the observed Minkowski
Functionals for SDSS galaxies are consistent with the prediction of a
Lambda--dominated spatially--flat Cold Dark Matter model with random--Gaussian
initial conditions, within the cosmic variance estimated from the corresponding
mock catalogue. We expect that future releases of the SDSS survey will allow us
to distinguish morphological differences in the galaxy distribution with regard
to different morphological type and luminosity ranges.


title: A new hypothesis of sunspot formation

abstract:
  The process of sunspot formation is considered with the account of heat
effects. According to the Le Chatelier principle, a local overheating must
precede to the cooling of solar surface in the places of sunspot formation. The
sunspot dynamics is a process close to the surface nucleate-free boiling in a
thin layer with formation of bubbles (or craters), so we focus on the analogy
between these two processes. Solar spots and surface nucleate-free boiling in a
thin layer have similarities in formation conditions, results of impact on the
surface were they have been formed, periodicity, and their place in the
hierarchy of self-organization in complex systems. The difference is in the
working medium and method of channelling of extra energy from the overheated
surface -for boiling process, the energy is forwarded to generation of vapor,
and in sunspots the solar energy is consumed to formation of a strong magnetic
field. This analogy explains the problem of a steady brightness (temperature)
of a spot that is independent of the spot size and other characteristics.


title:
Numerical 3D constraints on convective eddy time-correlations :
  consequences for stochastic excitation of solar p modes

abstract:
  A 3D simulation of the upper part of the solar convective zone is used to
obtain information on the frequency component, chi_k, of the correlation
product of the turbulent velocity field. This component plays an important role
in the stochastic excitation of acoustic oscillations. A time analysis of the
solar simulation shows that a gaussian function does not correctly reproduce
the nu-dependency of chi_k inferred from the 3D simuation in the frequency
range where the acoustic energy injected into the solar p modes is important
(nu ~ 2 - 4 mHz). The nu-dependency of chi_k is fitted with different
analytical functions which can then conveniently be used to compute the
acoustic energy supply rate P injected into the solar radial oscillations. With
constraints from a 3D simulation, adjustment of free parameters to solar data
is no longer necessary and is not performed here. The result is compared with
solar seismic data. Computed values of P obtained with the analytical function
which fits best chi_k are found ~ 2.7 times larger than those obtained with the
gaussian model and reproduce better the solar seismic observations. This
non-gaussian description also leads to a Reynolds stress contribution of the
same order as the one arising from the advection of the turbulent fluctuations
of entropy by the turbulent motions. Some discrepancy between observed and
computed P values still exist at high frequency and possible causes for this
discrepancy are discussed.


title:
The Optical Gravitational Lensing Experiment. Eclipsing Binary Stars in
  the Large Magellanic Cloud

abstract:
  We present the catalog of 2580 eclipsing binary stars detected in 4.6 square
degree area of the central parts of the Large Magellanic Cloud. The photometric
data were collected during the second phase of the OGLE microlensing search
from 1997 to 2000. The eclipsing objects were selected with the automatic
search algorithm based on an artificial neural network. Basic statistics of
eclipsing stars are presented. Also, the list of 36 candidates of detached
eclipsing binaries for spectroscopic study and for precise LMC distance
determination is provided. The full catalog is accessible from the OGLE
Internet archive.


title:
Signatures of highly inclined accretion disks in Galactic Black Hole
  Candidates and AGNs

abstract:
  Recent X-ray observations of Galactic Black Hole Candidates and AGNs and
Seyfert galaxies reveal the broad emission lines in their spectra, which can
arise in the innermost parts of accretion disks. Simulation indicates that at
low inclination angle the line is registered by distant observer with
characteristic two-peak profile. However, at high inclination angles ($> 85
\degr$) two additional peaks arise. This phenomenon was discovered by Matt,
Perola, Stella (1993) using the Schwarzschild black hole metric to analyze such
effect. They assumed that the effect is applicable to a Kerr metric far beyond
of a range of parameters that they exploited. We check and confirm their
hypothesis about such structure of the spectral line shape for a Kerr metric
case. We use no astrophysical assumptions about physical structure of the
emission region except assumption that the region should be narrow enough.
  Positions and heights of these extra peaks drastically depends on both the
radial coordinate of the emitting region (circular hot spot) and the
inclination angle. We find that best conditions to observe this effect are
realized at $\theta > 85\degr$ and $r > 5r_g$ and may exist in microquasars or
low-mass black holes in X-ray binary systems, because there is some precession
(and nutation of accretion disks) with not very long time periods (see, for
example, SS433 binary system). The line profiles for different inclination
angles and radial coordinates are presented. To analyze an influence of disk
models on the spectral line shapes we simulate the line profiles for Shakura --
Sunyaev disk model for accretion disks with the high inclination.


title:
Extragalactic Globular Clusters in the Near Infrared: III. NGC 5846 and
  NGC 7192

abstract:
  In this third paper of our series on near-IR and optical photometry of
globular cluster systems in early-type galaxies we concentrate on the
photometric results for NGC 5846 and NGC 7192, two group ellipticals, and on a
first comparison between the globular cluster systems investigated so far. In
NGC 5846 the colour-colour diagram shows clear bi-modality in (V-K), which is
confirmed by a KMM test. The mean colour of both peaks were estimated to be
(V-K) =2.57+/-0.06 (blue) and (V-K)=3.18+/-0.06 (red). The situation in NGC
7192 is different, in that the colour-colour diagram gives no evidence for a
distinct second population of globular clusters. Using simulated colour
distributions of globular cluster systems, we make a first step in quantifying
the cumulative age distribution in globular cluster systems. Also here the
result for NGC 5846 leads us to the conclusion that its metal-rich globular
cluster population contains two globular cluster populations which differ in
age by several Gyr. The age structure for NGC 7192 shows instead strong
similarity with a single-age population.


title: Simulations of Evolving or Outbursting Molecular Protostellar Jets

abstract:
  The kinematic and radiative power of molecular jets is expected to change as
a protostar undergoes permanent or episodal changes in the rate at which it
accretes. We study here the consequences of evolving jet power on the spatial
and velocity structure, as well as the fluxes, of molecular emission from the
bipolar outflow. We consider a jet of rapidly increasing density and a jet in
which the mass input is abruptly cut off. We perform three dimensional
hydrodynamic simulations with atomic and molecular cooling and chemistry. In
this work, highly collimated and sheared jets are assumed. We find that
position-velocity diagrams, velocity-channel maps and the relative H$_2$ and CO
fluxes are potentially the best indicators of the evolutionary stage. In
particular, the velocity width of the CO lines may prove most reliable although
the often-quoted mass-velocity power-law index is probably not. We demonstrate
how the relative H$_2$ 1--0 S(1) and CO J=1--0 fluxes evolve and apply this to
interpret the phase of several outflows.


title:
Resonant origin for density fluctuations deep within the Sun:
  helioseismology and magneto-gravity waves

abstract:
  We analyze helioseismic waves near the solar equator in the presence of
magnetic fields deep within the solar radiative zone. We find that reasonable
magnetic fields can significantly alter the shapes of the wave profiles for
helioseismic g-modes. They can do so because the existence of density gradients
allows g-modes to resonantly excite Alfven waves, causing mode energy to be
funnelled along magnetic field lines, away from the solar equatorial plane. The
resulting wave forms show comparatively sharp spikes in the density profile at
radii where these resonances take place. We estimate how big these waves might
be in the Sun, and perform a first search for observable consequences. We find
the density excursions at the resonances to be too narrow to be ruled out by
present-day analyses of p-wave helioseismic spectra, even if their amplitudes
were to be larger than a few percent. (In contrast it has been shown in
(Burgess et al. 2002) that such density excursions could affect solar neutrino
fluxes in an important way.) Because solar p-waves are not strongly influenced
by radiative-zone magnetic fields, standard analyses of helioseismic data
should not be significantly altered. The influence of the magnetic field on the
g-mode frequency spectrum could be used to probe sufficiently large
radiative-zone magnetic fields should solar g-modes ever be definitively
observed. Our results would have stronger implications if overstable solar
g-modes should prove to have very large amplitudes, as has sometimes been
argued.


title: The Evolution of Cluster Substructure

abstract:
  Using Chandra archival data, we have begun a study to quantify the evolution
of cluster morphology with redshift. To quantify cluster morphology, we use the
power ratio method developed by Buote and Tsai (1995). Power ratios are
constructed from moments of the two-dimensional gravitational potential and
are, therefore, related to a cluster's dynamical state. Our sample will include
around 50 clusters from the Chandra archive with redshifts between 0.11 and
1.1. These clusters were selected from two fairly complete flux-limited X-ray
surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity
Survey), and additional high-redshift clusters were selected from recent ROSAT
flux-limited surveys. Here we present preliminary results from the first 15
clusters in this sample. Of these, eight have redshifts below 0.5, and seven
have redshifts above 0.5.


title: Recent Microlensing Results from the MACHO Project

abstract:
  We describe a few recent microlensing results from the MACHO Collaboration.
The aim of the MACHO Project was the identification and quantitative
description of dark and luminous matter in the Milky Way using microlensing
toward the Magellanic Clouds and Galactic bulge. We start with a discussion of
the HST follow-up observations of the microlensing events toward the LMC
detected in the first 5 years of the experiment. Using color-magnitude diagrams
we attempt to distinguish between two possible locations of the microlensing
sources: 1) in the LMC or 2) behind the LMC. We conclude that unless the
extinction is extremely patchy, it is very unlikely that most of the LMC events
have sources behind the LMC. During an examination of the HST images of the 13
LMC events we found a very red object next to the source star of event LMC-5.
Astrometry, microlensing parallax fit, and a spectrum suggest that in this case
we directly image the lens - a low-mass disk star.
  Then we focus on the majority of events observed by the MACHO Project, which
are detected toward the Galactic bulge. We argue that the microlensing optical
depth toward the bulge is best measured using events that have clump giant
sources, which are almost unaffected by blending. From this sample we derive a
low optical depth toward the Galactic bulge of (1.4 +/- 0.3) x 10^{-6}, in good
agreement with other observational constraints and with theoretical models. The
presence of many long-duration events among the bulge candidates allows us to
investigate the microlensing parallax effect. Events with the strongest
parallax signal are probably due to massive remnants. Events MACHO-96-BLG-5 and
MACHO-98-BLG-6 might have been caused by the 6-solar-mass black holes.


title:
Nuclear activity and massive star formation in the low luminosity AGN
  NGC4303: Chandra X-ray observations

abstract:
  We present evidence of the co-existence of either an AGN or an ultraluminous
X-ray source (ULX), together with a young super stellar cluster in the 3
central parsecs of NGC4303. The galaxy contains a low luminosity AGN and hosts
a number of starburst regions in a circumnuclear spiral, as well as in the
nucleus itself. A high spatial resolution Chandra image of this source reveals
that the soft X-ray emission traces the ultraviolet nuclear spiral down to a
core, which is unresolved both in soft and hard X-rays. The astrometry of the
X-ray core coincides with the UV core within the Chandra positioning accuracy.
The total X-ray luminosity of the core, 1.5*10^{39} erg/s, is similar to that
from some LINERs or from the weakest Seyferts detected so far. The soft X-rays
in both the core and the extended structure surrounding it can be well
reproduced by evolutionary synthesis models (which include the emission
expected from single stars, the hot diffuse gas, supernova remnants and binary
systems), consistent with the properties of the young stellar clusters
identified in the UV. The hard X-ray tail detected in the core spectrum,
however, most likely requires the presence of an additional source. This
additional source could either be a weak active nucleus black hole or an
ultraluminous X-ray object. The implications of these results are discussed.


title:
Static spherically symmetric collapsar in the relativistic theory of
  gravitation: numerical approach and stability analysis

abstract:
  Numerical investigation of the static spherically symmetric vacuum solution
of the Logunov equations confirms the analytical results and demonstrates a
strong repulsion at sub-Planckian distance from the Schwarzschild-like
singularity, which is stable against the small perturbations. We suppose that
the final stage of the stellar collapse in the relativistic theory of
gravitation can entail the gravitational bursts with the gravitons
overproduction due to the strong deceleration in the vicinity of the
Schwarzschild sphere. The rigorous investigation of this topic requires a
quantum-field consideration.


title: GOTPM: A Parallel Hybrid Particle-Mesh Treecode

abstract:
  We describe a parallel, cosmological N-body code based on a hybrid scheme
using the particle-mesh (PM) and Barnes-Hut (BH) oct-tree algorithm. We call
the algorithm GOTPM for Grid-of-Oct-Trees-Particle-Mesh. The code is
parallelized using the Message Passing Interface (MPI) library and is optimized
to run on Beowulf clusters as well as symmetric multi-processors. The
gravitational potential is determined on a mesh using a standard PM method with
particle forces determined through interpolation. The softened PM force is
corrected for short range interactions using a grid of localized BH trees
throughout the entire simulation volume in a completely analogous way to P$^3$M
methods. This method makes no assumptions about the local density for short
range force corrections and so is consistent with the results of the P$^3$M
method in the limit that the treecode opening angle parameter, $\theta \to 0$.
  (abridged)


title: Telling the tale of the first stars

abstract:
  HE 0107-5240 is a star in more than once sense of the word. Chemically, it is
the most primitive object yet discovered, and it is at the centre of debate
about the origins of the first elements in the Universe.


title: N2H+(1-0) survey of massive molecular cloud cores

abstract:
  We present the results of N2H+(1-0) observations of 35 dense molecular cloud
cores from the northern and southern hemispheres where massive stars and star
clusters are formed. Line emission has been detected in 33 sources, for 28
sources detailed maps have been obtained. The optical depth of (23-12)
component toward peak intensity positions of 10 sources is ~ 0.2-1. In total,
47 clumps have been revealed in 26 sources. Integrated intensity maps with
aspect ratios < 2 have been fitted with a power-law radial distribution
$r^{-p}$ convolved with the telescope beam. Mean power-law index is close to
unity corresponding to the $\sim r^{-2}$ density profile provided N2H+
excitation conditions do not vary inside these regions. Line widths of the
cores either decrease or stay constant with distance from the center. The ratio
of rotational to gravitational energy is too low for rotation to play a
significant role in the dynamics of the cores. A correlation between mean line
widths and sizes of clumps has been found.


title: Searching for Variability in the Globular Cluster Messier 4

abstract:
  Time-series data taken with the Hubble Space Telescope of a field six core
radii (~5') from the center of the globular cluster Messier 4, and covering a
period of about 10 weeks in early 2001, have been analyzed in search of
variable objects. Various criteria were employed to select candidate variable
stars. Period searches were performed on the selected candidates using phase
dispersion minimization (PDM). The reliability of the PDM search results was
tested using synthetic light curves of eclipsing binary stars and sinusoidal
light curves of different periods. Results from this analysis showed that there
are probably no eclipsing binary stars or periodic variables in our field with
periods on the order of a few hours to a few days, down to limiting magnitudes
of V~25 and I~24, which is consistent with the absence of contact binaries such
as W Ursae Majoris systems. However, one candidate variable star does show an
increase in brightness of ~0.1 magnitudes in both bandpasses, which seems to
last for a few days. Possible explanations concerning the nature of this object
include a binary system with a white dwarf primary and a low-mass main sequence
secondary, or a BY Draconis variable star. We are able to set an upper limit to
the observed fraction of photometric variability in this dataset of 0.05%.


title:
Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. II. Optical
  Spectroscopy

abstract:
  The results from deep long-slit spectroscopy of nine edge-on spiral galaxies
with known extraplanar line emission are reported. Emission from Halpha, [N II]
lambda 6548, 6583, and [S II] lambda 6716, 6731 is detected out to heights of a
few kpc in all of these galaxies. Several other fainter diagnostic lines such
as [O I] lambda 6300, [O III] lambda 4959, 5007, and He I lambda 5876 are also
detected over a smaller scale. The relative strengths, centroids and widths of
the various emission lines provide constraints on the electron density,
temperature, reddening, source(s) of ionization, and kinematics of the
extraplanar gas. In all but one galaxy, photoionization by massive OB stars
alone has difficulties explaining all of the line ratios in the extraplanar
gas. Hybrid models that combine photoionization by OB stars and another source
of ionization such as photoionization by turbulent mixing layers or shocks
provide a better fit to the data. The (upper limits on the) velocity gradients
measured in these galaxies are consistent with the predictions of the galactic
fountain model to within the accuracy of the measurements.


title: Infrared Photometry of Starless Dense Cores

abstract:
  Deep JHKs photometry was obtained towards eight dense molecular cores and J-H
vs. H-Ks color-color plots are presented. Our photometry, sensitive to the
detection of a 1 solar mass, 1 X 10^6 year old star through approx. 35 - 50
magnitudes of visual extinction, shows no indication of the presence of
star/disk systems based on J-H vs. H-Ks colors of detected objects. The stars
detected towards the cores are generally spatially anti-correlated with core
centers suggesting a background origin, although we cannot preclude the
possibility that some stars detected at H and Ks alone, or Ks alone, are not
low mass stars or brown dwarfs (< 0.3 Solar Masses) behind substantial amounts
of visual extinction (e.g. 53 magnitudes for L183B). Lower limits to optical
extinctions are estimated for the detected background stars, with high
extinctions being encountered, in the extreme case ranging up to at least Av =
46, and probably higher. The extinction data are used to estimate cloud masses
and densities which are comparable to those determined from molecular line
studies. Variations in cloud extinctions are consistent with a systematic
nature to cloud density distributions and column density variations and
extinctions are found to be consistent with submillimeter wave continuum
studies of similar regions. The results suggest that some cores have achieved
significant column density contrasts (approx. 30) on sub-core scales (approx.
0.05 pc) without having formed known stars.


title: Infrared Spectral Energy Distribution Model for Extremely Young Galaxies

abstract:
  The small grain sizes produced by Type II supernova (SN II) models in young,
metal-poor galaxies make the appearance of their infrared (IR) spectral energy
distribution (SED) quite different from that of nearby, older galaxies. To
study this effect, we have developed a model for the evolution of dust content
and the IR SED of low-metallicity, extremely young galaxies based on Hirashita
et al. (2002). We find that, even in the intense ultraviolet (UV) radiation
field of very young galaxies, small silicate grains are subject to stochastic
heating resulting in a broad temperature distribution and substantial MIR
continuum emission. Larger carbonaceous grains are in thermal equilibrium at T
\simeq 50 - 100K, and they also contribute to the MIR. We present the evolution
of SEDs and IR extinction of very young, low-metallicity galaxies. The IR
extinction curve is also shown. In the first few Myrs, the emission peaks at
\lambda \sim 30-50um at later times dust self-absorption decreases the apparent
grain temperatures, shifting the bulk of the emission into the submillimetre
band. We successfully apply the model to the IR SED of a low metallicity (1/41
Z_\odot) dwarf galaxy SBS0335-052. We find the SED, optical properties and
extinction of the star forming region to be consistent with a very young and
compact starburst. We also predict the SED of another extremely low-metallicity
galaxy, I Zw 18, for future observational tests. Some prospects for future
observations are discussed.


title: Direct Mapping of Massive Compact Objects in Extragalactic Dark Halos

abstract:
  A significant fraction of non-baryonic or baryonic dark matter in galactic
halos may consist of MASsive Compact Objects (MASCOs) with mass
M=10^{1-4}M_{sun}. Possible candidates for such compact objects include
primordial black holes or remnants of primordial (Population III) stars. We
propose a method for directly detecting MASCOs in extragalactic halos, using
the VLBI techniques with extremely high resolution. If a galactic halo
comprising a large number of MASCOs produces multiple images of a background
radio-loud QSO by gravitational lensing, then a high-resolution radio map of
each macro-lensed image should reveal microlensing effects by MASCOs. To assess
their observational feasibility, we simulate microlensing of the radio-loud,
four-image lensed QSO, B1422+231, assuming angular resolution of ~0.01 mas.
MASCOs are represented by point masses. For comparison, we also simulate
microlensing of B1422+231 by singular isothermal spheres. We find that the
surface brightness of the macro-lensed images shows distinct spatial patterns
on the scale of the Einstein radius of the perturbers. In the case of
point-mass perturbers, many tiny dark spots also appear in the macro-lensed
images associated with a decrease in the surface brightness toward the fringe
of the original QSO image, whereas no such spots are available in the SIS
models. Based on the size, position and magnified or demagnified patterns of
images, we shall be able to determine the mass and density profile of a MASCO
as well as its spatial distribution and abundance in a galactic halo.


title:
Hot HB stars in globular clusters - Physical parameters and consequences
  for theory. VI. The second parameter pair M 3 and M 13

abstract:
  We present the results of spectroscopic analyses of hot horizontal branch
(HB) stars in M 13 and M 3, which form a famous ``second parameter'' pair. From
the spectra and Stroemgren photometry we derived -- for the first time in M 13
-- atmospheric parameters (effective temperature and surface gravity). For
stars with Stroemgren temperatures between 10,000 and 12,000 K we found
excellent agreement between the atmospheric parameters derived from Stroemgren
photometry and those derived from Balmer line profile fits. However, for cooler
stars there is a disagreement in the parameters derived by the two methods, for
which we have no satisfactory explanation. Stars hotter than 12,000 K show
evidence for helium depletion and iron enrichment, both in M 3 and M 13.
Accounting for the iron enrichment substantially improves the agreement with
canonical evolutionary models, although the derived gravities and masses are
still somewhat too low. This remaining discrepancy may be an indication that
scaled-solar metal-rich model atmospheres do not adequately represent the
highly non-solar abundance ratios found in blue HB stars affected by diffusion.
We discuss the effects of an enhancement in the envelope helium abundance on
the atmospheric parameters of the blue HB stars, as might be caused by deep
mixing on the red giant branch or primordial pollution from an earlier
generation of intermediate mass asymptotic giant branch stars.


title: Detection of abundant solid methanol toward young low mass stars

abstract:
  We present detections of the absorption band at 3.53 micron due to solid
methanol toward three low-mass young stellar objects located in the Serpens and
Chameleon molecular cloud complexes. The sources were observed as part of a
large spectroscopic survey of ~40 protostars. This is the first detection of
solid methanol in the vicinity of low mass (M <1 Msol) young stars and shows
that the formation of methanol does not depend on the proximity of massive
young stars. The abundances of solid methanol compared to water ice for the
three sources are in the range 15-25% which is comparable to those for the most
methanol-rich massive sources known. The presence of abundant methanol in the
circumstellar environment of some low mass young stars has important
consequences for the formation scenarios of methanol and more complex organic
species near young solar-type stars.


title: INTEGRAL and XMM-Newton observations of the weak GRB 030227

abstract:
  We present INTEGRAL and XMM-Newton observations of the prompt gamma-ray
emission and the X-ray afterglow of GRB030227, the first GRB for which the
quick localization obtained with the INTEGRAL Burst Alert System (IBAS) has led
to the discovery of X-ray and optical afterglows. GRB030227 had a duration of
about 20 s and a peak flux of 1.1 photons cm^-2 s^-1 in the 20-200 keV energy
range. The time averaged spectrum can be fit by a single power law with photon
index about 2 and we find some evidence for a hard to soft spectral evolution.
The X-ray afterglow has been detected starting only 8 hours after the prompt
emission, with a 0.2-10 keV flux decreasing as t^-1 from 1.3x10e-12 to 5x10e-13
erg cm^-2 s^-1. The afterglow spectrum is well described by a power law with
photon index 1.94+/-0.05 modified by a redshifted neutral absorber with column
density of several 10e22 cm^-2. A possible emission line at 1.67 keV could be
due to Fe for a redshift z=3, consistent with the value inferred from the
absorption.


title: Gamma Rays from Primordial Black Holes in Supersymmetric Scenarios

abstract:
  Using the MacGibbon-Webber model, the instantaneous photon (gamma-ray)
emission spectra from PBHs in the Standard Model and mSUGRA benchmark models
were investigated numerically. The point source and diffuse gamma-ray spectra
from PBHs were also found numerically. It was found that the instantaneous
photon flux from PBHs in mSUGRA benchmark models is generally less than
approximately four times greater than in the Standard Model. The point source
flux from a PBH in its final stages of emission will in mSUGRA benchmark models
both quantitatively and qualitatively differ from that in the Standard Model.
The dominant part of the diffuse gamma-ray flux should not be affected by any
supersymmetric particles. However, for PBHs with initial mass approximately in
the range [4x10^13 g, 1x10^14 g], the diffuse Standard Model flux at photon
energies E_0 > ~1 GeV will generally be less than roughly 50% greater than for
mSUGRA benchmark models. The results generally show good agreement with
previous works, although model differences give some disagreement. It is
concluded that it is unlikely that the effects found could be detected with the
upcoming gamma-ray satellite GLAST, due for launch in 2006. This Master's
Thesis also gives a review of PBH formation and emission, as well as some
cosmological consequences associated with PBHs. The concept of supersymmetry in
quantum mechanics and particle physics is also introduced.


title: XMM-Newton observations of Nova LMC 2000

abstract:
  We report on three X-ray observations of Nova LMC 2000 with XMM at 17, 51 and
294 days after the maximum, respectively. X-ray spectral fits show a concordant
decrease of the absorbing column and the X-ray luminosity. No supersoft X-ray
emission is detected. The mass of the ejected shell is determined to be (less
than) 7.5*E-5 msun. Though data are sparse, one interesting correlation becomes
visible: sources with a long-duration supersoft X-ray phase have shorter
orbital periods than those with short or no supersoft X-ray phase. This can be
understood considering that (i) enough matter has to be accreted in order to
ignite the H burning, and (ii) that H burning ceases when the mass of the
remaining material (after shell ejection and burning) drops below a certain
limit under which the temperature at the bottom of the envelope is too low for
the shell burning to compensate the energy loss from the surface.


title: Flux Ratio Anomalies: Micro- and Milli-lensing

abstract:
  Simple models for lensing potentials that successfully reproduce the
positions of quadruple images to high accuracy fail abysmally in reproducing
the flux ratios of the multiple images, suggesting the presence of small scale
structure within the lensing galaxies. It has been argued that the flux ratio
anomalies observed at radio wavelengths signal the presence of CDM mini-halos.
We argue that at least some of the anomalies observed at optical wavelengths
result from micro-lensing by stars. This model succeeds in explaining observed
asymmetry between minima and saddle-points of the light travel time only if a
substantial fraction of the projected mass is in a smooth, dark component.


title: Optical afterglow of the not so dark GRB 021211

abstract:
  We determine Johnson $B,V$ and Cousins $R,I$ photometric CCD magnitudes for
the afterglow of GRB 021211 during the first night after the GRB trigger. The
afterglow was very faint and would have been probably missed if no prompt
observation had been conducted. A fraction of the so-called ``dark'' GRBs may
thus be just ``optically dim'' and require very deep imaging to be detected.
The early-time optical light curve reported by other observers shows prompt
emission with properties similar to that of GRB 990123. Following this, the
afterglow emission from $\sim 11$ min to $\sim 33$ days after the burst is
characterized by an overall power-law decay with a slope $1.1\pm0.02$ in the
$R$ passband. We derive the value of spectral index in the optical to near-IR
region to be 0.6$\pm$0.2 during 0.13 to 0.8 day after the burst. The flux decay
constant and the spectral slope indicate that optical observations within a day
after the burst lies between cooling frequency and synchrotron maximum
frequency.


title: SN 2002ap, the hypernova of class Ic

abstract:
  The supernova SN 2002ap was discovered in the outer regions of the nearby
spiral M74 on January 29.4 UT. Early photometric and spectroscopic observations
indicate the supernova belongs to the class of Ic hypernova. Late time (After
JD 2452500) light curve decay slopes are similar to that of the hypernovae SN
1997ef and SN 1998bw. We present here the $BVRI$ photometric light curves and
colour evolutions of SN 2002ap to investigate the late time nature of the light
curve.


title:
Evidence for Hydro-Gravitational Structure Formation Theory versus
  Cold-Dark-Matter, Hierarchical-Clustering, and Jeans 1902

abstract:
  Observations are compared to conflicting predictions about self-gravitational
structure formation by the hydro-gravitational theory (HGT) of Gibson 1996-2003
versus cold-dark-matter hierarchical-clustering-cosmology (CDMHCC) and the
Jeans 1902 criterion. According to HGT, gravitational structures form
immediately after mass-energy equality by plasma fragmentation at 30,000 years
when viscous and weak turbulence forces first balance gravitational forces
within the horizon L_H = ct < L_J = c/[3\rho G]^1/2, contrary to the Jeans 1902
criterion. Buoyancy forces fossilize the 10^-12 s^-1 rate-of-strain and the
10^-17 kg m^-3 baryonic density. The non-baryonic dark matter (NBDM) diffuses
into the voids rather than forming cold-dark-matter (CDM) halos required by
CDMHCC. From HGT, supercluster-mass to galaxy-mass fragments exist at the
plasma to gas transition, and these fragment further to form
proto-globular-star clusters (PGCs) and planetary-mass primordial-fog-particles
(PFPs): the baryonic dark matter of the interstellar-medium and
inner-galaxy-dark-matter-halos, from which all planets and stars are formed by
accretion (Gibson 1996, Schild 1996). From HGT and a rich cluster mass profile
(Tyson and Fischer 1995), D_NBDM = 6 x10^28 m^2 s^-1, m_NBDM <= 10^-33 kg, and
the NBDM forms outer-galaxy halos after 300,000 years.


title:
Observational estimates of the initial power spectrum at small scale
  from Lyman-$\alpha$ absorbers

abstract:
  We present a new method of measuring the power spectrum of initial
perturbations to an unprecedently small scale of $\sim$ 10$h^{-1}$ kpc. We
apply this method to a sample of 4500 Ly-$\alpha$ absorbers and recover the
cold dark matter (CDM) like power spectrum at scales $\geq 300h^{-1}$kpc with a
precision of $\sim$ 10%. However at scales $\sim 10 - 300 h^{-1}$kpc the
measured and CDM--like spectra are noticeable different. This result suggests a
complex inflation with generation of excess power at small scales. The
magnitude and reliability of these deviations depend also upon the possible
incompleteness of our sample and poorly understood process of formation of weak
absorbers. Confirmation of the CDM--like shape of the initial power spectrum or
detection of its distortions at small scales are equally important for widely
discussed problems of physics of the early Universe, galaxy formation, and
reheating of the Universe. Our method links the observed mass function of
absorbers with the correlation function of the initial velocity field and
therefore it avoids the Nyquist restrictions limiting the investigations based
on the smoothed flux or density fields.
  The physical model of absorbers adopted here asserts that they are formed in
the course of both linear and nonlinear adiabatic or shock compression of dark
matter (DM) and gaseous matter. At scales $\geq 1h^{-1}$Mpc all characteristics
of the DM component and, in particular, their redshift distribution are found
to be consistent with theoretical expectations for Gaussian initial
perturbations with a CDM--like power spectrum.


title: Microlensing towards M31 with MDM data

abstract:
  We report the final analysis of a search for microlensing events in the
direction of the Andromeda galaxy, which aimed to probe the MACHO composition
of the M31 halo using data collected during the 1998-99 observational campaign
at the MDM observatory. In a previous paper, we discussed the results from a
first set of observations. Here, we deal with the complete data set, and we
take advantage of some INT observations in the 1999-2000 seasons. This merging
of data sets taken by different instruments turns out to be very useful, the
study of the longer baseline available allowing us to test the uniqueness
characteristic of microlensing events. As a result, all the candidate
microlensing events previously reported turn out to be variable stars. We
further discuss a selection based on different criteria, aimed at the detection
of short--duration events. We find three candidates whose positions are
consistent with self--lensing events, although the available data do not allow
us to conclude unambiguously that they are due to microlensing.


title: Magnetohydrostatic atmospheres

abstract:
  We show that the atmospheric and magnetic height variations are coupled in
general MHS equilibria with gravity when isolated thin non-force-free flux
tubes are present. In gas-dominated environments, as in stellar photospheres,
flux tubes must expand rapidly with height to maintain pressure balance with
the cool surroundings. But in magnetically dominated environments, as in
stellar coronae, the large-scale background magnetic field determines the
average spreading of embedded flux tubes, and rigidly held flux tubes {\it
require} a specific surrounding atmosphere with a unique temperature profile
for equilibrium. The solar static equilibrium atmosphere exhibits correct
transition-region properties and the accepted base coronal temperature for the
sun's main magnetic spherical harmonic. Steady flows contribute to the overall
pressure, so equilibria with accelerated wind outflows are possible as well.
Flux tubes reflect a mathematical degeneracy in the form of non-force-free
fields, which leads to coupling in general equilibrium conditions. The
equilibrium state characterizes the system average in usual circumstances and
dynamics tend to maintain the MHS atmosphere. Outflows are produced everywhere
external to rigidly held flux tubes that refill a depleted or cool atmosphere
to the equilibrium gas profile, heating the gas compressively.


title: Spectral properties of anomalous X-ray pulsars

abstract:
  In this paper, the spectra of the persistent emission from anomalous X-ray
pulsars (AXPs) and their variation with spin-down rate $\dot{\Omega}$ is
considered. Firstly, based on an accretion-powered model, the influences of
both magnetic field and mass accretion rate on the spectra properties of AXPs
are addressed. Subsequently, the relation between the spectral property of AXPs
and mass accretion rate $\dot{M}$ is investigated. The result shows that there
exists a linear correlation between the photon index and mass accretion rate,
and the spectral hardness increases with increasing $\dot{M}$. A possible
emission mechanism for the explanation of spectral properties of AXPs is also
discussed.


title: Astrophysics of Dust in Cold Clouds

abstract:
  Nine lectures reviewing the astrophysics of dust in interstellar clouds.
Topics include: (1) Summary of observational evidence concerning interstellar
dust: broadband extinction, scattering of starlight, polarization of starlight,
spectroscopy of dust, IR and FIR emission, and depletions of grain-forming
elements. (2) Optics of interstellar dust grains: dielectric functions of
nonconducting and conducting materials, calculational techniques, formulae
valid in the Rayleigh limit, Kramers-Kronig relations, microwave emission
mechanisms, and X-ray scattering. (3) IR and FIR emission: heating of
interstellar dust, including single-photon heating, and resulting IR emission
spectrum. (4) Charging of dust grains: collisional charging, photoelectric
emission, and resulting charge distribution functions. (5) Dynamics: gas drag,
Lorentz force, forces due to anisotropic radiation, and resulting drift
velocities. (6) Rotational dynamics: brownian rotation, suprathermal rotation,
and effects of starlight torques. (7) Alignment of interstellar dust:
observations and theories. (8) Evolution of the grain population: dust
formation in outflows, grain growth in the ISM, photodesorption, and grain
destruction in shock waves. (9) Effects of dust grains: photoelectric heating,
H2 formation, ion recombination, coupling of gas to magnetic fields, and dust
grains as indicators of magnetic field direction.


title: Interstellar Dust Grains

abstract:
  This review surveys the observed properties of interstellar dust grains: the
wavelength-dependent extinction of starlight, including absorption features,
from UV to IR; optical luminescence; IR emission; microwave emission; optical,
UV, and X-ray scattering by dust; and polarization of starlight and of infrared
emission. The relationship between presolar grains in meteorites and the
interstellar grain population is discussed. Candidate grain materials and
abundance constraints are considered. A dust model consisting of amorphous
silicate grains, graphite grains, and PAHs is compared with observed emission
and scattering. Some issues concerning evolution of interstellar dust are
discussed.


title:
Diamagnetic Screening of the Magnetic Field in Accreting Neutron Stars
  II -- The effect of Polar Cap Widening

abstract:
  Recently, we have proposed a model for the screening of the magnetic field of
an accreting neutron star by the accreted material flowing from the polar
regions towards the equator and sinking there underneath the surface (Choudhuri
& Konar). In this model it was assumed that the flow pattern remained
stationary over time. However, as the surface magnetic field weakens, the
accretion takes place over a wider region around the pole, making the flow more
radial and isotropic. In the present work, we extend this two-dimensional model
to include the time-dependence of the flow of the accreted material. The final
radial flow is found to be less efficient in screening the magnetic field
compared to the initial tangential flow. After an initial phase of rapid decay,
the magnetic field slowly reaches an asymptotic value when the accretion
becomes nearly isotropic and radial. Assuming the initial extent of the polar
cap to be $\sim 5^0$--$10^0$, a simple geometric argument suggests that the
magnetic field should decay by 3-4 orders of magnitude before stabilizing to an
asymptotic value, consistent with the magnetic fields observed in millisecond
pulsars.


title: Thermal radiation from an accretion disk

abstract:
  An effect of stimulated radiation processes on thermal radiation from an
accretion disk is considered. The radial density waves triggering flare
emission and producing quasi-periodic oscillations in radiation from an
accretion disk are discussed. It is argued that the observational data suggest
the existence of the weak laser sources in a two-temperature plasma of an
accretion disk.


title: A Fossil Record of Galaxy Encounters

abstract:
  The cosmic infrared background (CIRB) is a record of a large fraction of the
emission of light by stars and galaxies over time. The bulk of this emission
has been resolved by the Infrared Space Observatory camera. The dominant
contributors are bright starburst galaxies with redshift z ~ 0.8; that is, in
the same redshift range as the active galactic nuclei responsible for the bulk
of the x-ray background. At the longest wavelengths, sources of redshift z>2
tend to dominate the CIRB. It appears that the majority of present-day stars
have been formed in dusty starbursts triggered by galaxy-galaxy interactions
and the build-up of large-scale structures.


title: A new technique to improve RFI suppression in radio interferometers

abstract:
  Radio interferometric observations are less susceptible to radio frequency
interference (RFI) than single dish observations. This is primarily due to :
(1)fringe-frequency averaging at the correlator output and (2) bandwidth
decorrelation of broadband RFI. Here, we propose a new technique to improve RFI
suppression of interferometers by replacing the fringe-frequency averaging
process with a different filtering process. In the digital implementation of
the correlator, such a filter should have cutoff frequencies $< 10^{-6}$ times
the frequency at which the baseband signals are sampled. We show that filters
with such cutoff frequencies and attenuation $>$ 40 dB at frequencies above the
cutoff frequency can be realized using multirate filtering techniques.
Simulation of a two element interferometer system with correlator using
multirate filters shows that the RFI suppression at the output of the
correlator can be improved by 40 dB or more compared to correlators using a
simple averaging process.


title: VLT/ISAAC H-band spectroscopy of embedded massive YSOs

abstract:
  We have performed intermediate resolution (R = 5000), high signal-to-noise
H-band spectroscopy of a small, initial sample of three massive embedded young
stellar objects (YSOs), using VLT/ISAAC. The sample has been selected from
sources characterised in previous literature as being likely of OB spectral
type, to be unambiguously associated with bright (H < 14) single point sources
in the 2MASS database, and to have no optical counterparts. Of the targets
observed, one object shows a ~B3 spectrum, similar to a main sequence object of
the same spectral type. A second object exhibits weak HeI and H emission,
indicating an early-type source: we detect HeII absorption, which supports a
previous indirect derivation of the spectral type as mid-O. The third object
does not show absorption lines, so no spectral type can de derived. It does,
however, exhibit a rich spectrum of strong, broad emission lines and is likely
to be surrounded by dense circumstellar material and at a very early
evolutionary stage. Our results from this very small sample are in agreement
with those of Kaper et al. (2002), who also find spectra similar to optically
visible main sequence stars, together with emission line objects representing a
very early evolutionary phase, in their much larger sample of K-band spectra.


title:
The Brightest Pulses in the Universe: Multifrequency Observations of the
  Crab Pulsar's Giant Pulses

abstract:
  We analyze the Crab pulsar at ten frequencies from 0.43 to 8.8 GHz using data
obtained at the Arecibo Observatory. Giant pulses occur only in the main and
interpulse components manifest from radio frequencies to gamma-ray energies.
Individual giant pulses reach brightness temperatures of at least $10^{32}$K in
our data, which do not resolve the narrowest pulses, and are known to reach
$10^{37}$K in nanosecond-resolution observations (Hankins et al 2003). Giant
pulses are therefore the brightest known in the observable universe and
represent an important milestone for theories of the pulsar emission mechanism
to explain. Their short durations allow them to serve as especially sensitive
probes of the Crab Nebula and the interstellar medium. We analyze frequency
structure in individual giant pulses using a scintillating,
amplitude-modulated,polarized shot-noise model. The frequency structure
associated with multipath propagation decorrelates on a time scale of 25 sec at
1.5 GHz, which requires that multipath propagation be strongly influenced by
material within the Crab Nebula. Additional frequency structure decorrelates
faster than one spin period, as would be expected from the shot-noise pattern
of nanosecond duration pulses emitted by the pulsar. Taking into account the
Crab pulsar's locality inside a bright supernova remnant, we conclude that the
brightest pulse in a typical 1-hour observation would be most easily detectable
in our lowest frequency band (0.43 GHz) to a distance of 1.6 Mpc. We also
discuss the detection of such pulses using future instruments such as LOFAR and
the SKA.


title:
Dynamics of magnetic flux tubes in close binary stars I. Equilibrium and
  stability properties

abstract:
  Surface reconstructions of active close binary stars based on photometric and
spectroscopic observations reveal non-uniform starspot distributions, which
indicate the existence of preferred spot longitudes (with respect to the
companion star). We consider the equilibrium and linear stability of toroidal
magnetic flux tubes in close binaries to examine whether tidal effects are
capable to initiate the formation of rising flux loops at preferred longitudes
near the bottom of the stellar convection zone. The tidal force and the
deviation of the stellar structure from spherical symmetry are treated in
lowest-order perturbation theory assuming synchronised close binaries with
orbital periods of a few days. The frequency, growth time, and spatial
structure of linear eigenmodes are determined by a stability analysis. We find
that, despite their small magnitude, tidal effects can lead to a considerable
longitudinal asymmetry in the formation probability of flux loops, since the
breaking of the axial symmetry due to the presence of the companion star is
reinforced by the sensitive dependence of the stability properties on the
stellar stratification and by resonance effects. The orientation of preferred
longitudes of loop formation depends on the equilibrium configuration and the
wave number of the dominating eigenmode. The change of the growth times of
unstable modes with respect to the case of a single star is very small.


title: Quasar Lensing: the Observer's Point of View

abstract:
  The determination of the Hubble parameter H_0 is probably one of the most
important applications of quasar lensing. The method, based on the measurement
of the so-called ``time-delay'' between the lensed images of distant sources,
e.g., quasars, and on detailed mass modeling of the potential well responsible
for the multiple images, yields an accuracy at least comparable with other
techniques and that can be improved further with high precision observations,
as can be obtained with intrumentation of constantly increasing quality. The
basics of the ``time-delay'' method are described, and the emphasis is put on
the observational constraints available to the astrophysicist in order to
implement the method and to derive an accurate value for H_0, independent of
any standard candle or any strong prior on the other cosmological parameters.


title:
Dynamics of magnetic flux tubes in close binary stars II. Nonlinear
  evolution and surface distributions

abstract:
  Observations of magnetically active close binaries with orbital periods of a
few days reveal the existence of starspots at preferred longitudes (with
respect to the direction of the companion star). We numerically investigate the
non-linear dynamics and evolution of magnetic flux tubes in the convection
zoneof a fast-rotating component of a close binary system and explore whether
the tidal effects are able to generate non-uniformities in the surface
distribution of erupting flux tubes. Assuming a synchronised system with a
rotation period of two days and consisting of two solar-type components, both
the tidal force and the deviation of the stellar structure from spherical shape
are considered in lowest-order perturbation theory. The magnetic field is
initially stored in the form of toroidal magnetic flux rings within the stably
stratified overshoot region beneath the convection zone. Once the field has
grown sufficiently strong, instabilities initiate the formation of rising flux
loops, which rise through the convection zone and emerge at the stellar
surface. We find that although the magnitude of tidal effects is rather small,
they nevertheless lead to the formation of clusters of flux tube eruptions at
preferred longitudes on opposite sides of the star, which result from the
cumulative and resonant character of the action of tidal effects on rising flux
tubes. The longitude distribution of the clusters depends on the initial
parameters of flux tubes in the overshoot region like magnetic field strength
and latitude, implying that there is no globally unique preferred longitude
along a fixed direction.


title:
The Relation Between the Surface Brightness and the Diameter for
  Galactic Supernova Remnants

abstract:
  In this work, we have constructed a relation between the surface brightness
($\Sigma$) and diameter (D) of Galactic C- and S-type supernova remnants
(SNRs). In order to calibrate the $\Sigma$-D dependence, we have carefully
examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of
the ambient medium) properties of the remnants and, taking into account also
the distance values given in the literature, we have adopted distances for some
of the SNRs which have relatively more reliable distance values. These
calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR
Cas A which has an exceptionally high surface brightness) are excluded. The
Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: $\Sigma$(at 1
GHz)=8.4$^{+19.5}_{-6.3}$$\times10^{-12}$ D$^{{-5.99}^{+0.38}_{-0.33}}$
Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$\le3.7\times10^{-21}$
Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$\ge$36.5 pc) and $\Sigma$(at 1
GHz)=2.7$^{+2.1}_{-1.4}$$\times$ 10$^{-17}$ D$^{{-2.47}^{+0.20}_{-0.16}}$
Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$>3.7\times10^{-21}$
Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$<$36.5 pc). We discussed the theoretical
basis for the $\Sigma$-D dependence and particularly the reasons for the change
in slope of the relation were stated. Added to this, we have shown the
dependence between the radio luminosity and the diameter which seems to have a
slope close to zero up to about D=36.5 pc. We have also adopted distance and
diameter values for all of the observed Galactic SNRs by examining all the
available distance values presented in the literature together with the
distances found from our $\Sigma$-D relation.


title:
Six years of BeppoSAX Wide Field Cameras observations of nine galactic
  type-I X-ray bursters

abstract:
  We present an overview of BeppoSAX Wide Field Cameras observations of the
nine most frequent type-I X-ray bursters in the Galactic center region. Six
years of observations (from 1996 to 2002) have amounted to 7 Ms of Galactic
center observations and the detection of 1823 bursts. The 3 most frequent
bursters are GX 354-0 (423 bursts), KS 1731-260 (339) and GS 1826-24 (260).
These numbers reflect an unique dataset. We show that all sources have the same
global burst behavior as a function of luminosity. At the lowest luminosities
(L_X<=2E37 erg/s bursts occur quasi-periodically and the burst rate increases
linearly with accretion rate (clear in e.g. GS 1826-24 and KS 1731-260). At
L_pers=2E37 erg/s the burst rate drops by a factor of five. This corresponds to
the transition from, on average, a hydrogen-rich to a pure helium environment
in which the flashes originate that are responsible for the bursts. At higher
luminosities the bursts recur irregularly; no bursts are observed at the
highest luminosities. Our central finding is that most of the trends in
bursting behavior are driven by the onset of stable hydrogen burning in the
neutron star atmosphere. Furthermore, we notice three new observational fact
which are difficult to explain with current burst theory: the presence of short
pure-helium bursts at the lowest accretion regimes, the bimodal distribution of
peak burst rates, and an accretion rate that is ten times higher than predicted
at which the onset of stable hydrogen burning occurs. Finally, we note that our
investigation is the first to signal quasi-periodic burst recurrence in KS
1731-260, and a clear proportionality between the frequency of the
quasi-periodicity and the persistent flux in GS 1826-24 and KS 1731-260.


title:
Radiative transfer in disc galaxies -- III. The observed kinematics of
  dusty disc galaxies

abstract:
  We present SKIRT (Stellar Kinematics Including Radiative Transfer), a new
Monte Carlo radiative transfer code that allows the calculation of the observed
stellar kinematics of a dusty galaxy. The code incorporates the effects of both
absorption and scattering by interstellar dust grains, and calculates the
Doppler shift of the emerging radiation exactly by taking into account the
velocities of the emitting stars and the individual scattering dust grains. The
code supports arbitrary distributions of dust through a cellular approach,
whereby the integration through the dust is optimized by means of a novel
efficient trilinear interpolation technique.
  We apply our modelling technique to calculate the observed kinematics of
realistic models for dusty disc galaxies. We find that the effects of dust on
the mean projected velocity and projected velocity dispersion are severe for
edge-on galaxies. For galaxies which deviate more than a few degrees from
exactly edge-on, the effects are already strongly reduced. As a consequence,
dust attenuation cannot serve as a possible way to reconcile the discrepancy
between the observed shallow slopes of the inner rotation curves of LSB
galaxies and the predictions of CDM cosmological models. For face-on galaxies,
the velocity dispersion increases with increasing dust mass due to scattering,
but the effects are limited, even for extended dust distributions. Finally, we
show that serious errors can be made when the individual velocities of the dust
grains are neglected in the calculations.


title:
Tracing the Sgr Stream with 2MASS. Detection of Stream stars around
  Outer Halo Globular Clusters

abstract:
  We use infrared Color Magnitude Diagrams from the 2-Micron All-Sky Survey
(2MASS) to search for stars belonging to the tidal stream of the Sagittarius
dwarf spheroidal galaxy (Sgr dSph) around selected Galactic globular clusters.
Statistically significant detections are presented for the cases of Pal 12 and
NGC 4147, strongly supporting the idea that these clusters are associated with
the Sgr Stream and that they were previous members of the Sgr dSph galaxy.


title: RX J0042.3+4115: a stellar mass black hole binary identified in M31

abstract:
  Four XMM-Newton X-ray observations of the central region of the Andromeda
Galaxy (M31) have revealed an X-ray source that varies in luminosity over
\~1--3, 10^{38} erg s^{-1} between observations and also displays significant
variability over time-scales of a few hundred seconds. The power density
spectra of lightcurves obtained in the 0.3--10 keV energy band from the three
EPIC instruments on board XMM-Newton are typical of disc-accreting X-ray
binaries at low accretion rates, observed in neutron star binaries only at much
lower luminosities (~10^{36} erg s^{-1}). However X-ray binaries with massive
black hole primaries have exhibited such power spectra for luminosities
>10^{38} erg s^{-1}. We discuss alternative possibilities where RX J0042.3+4115
may be a background AGN or foreground object in the field of view, but conclude
that it is located within M31 and hence use the observed power spectra and
X-ray luminosities to identify the primary as a black hole candidate.


title: Modelling galaxy halos using dark matter with pressure

abstract:
  We investigate whether a dark matter with substantial amounts of pressure,
comparable in magnitude to the energy density, could be a viable candidate for
the constituent of dark matter halos. We find that galaxy halos models,
consistent with observations of flat rotation curves, are possible for a
variety of equations of state with anisotropic pressures. It turns out that the
gravitational bending of light rays passing through such halos is very
sensitive to the pressure. We propose that combined observations of rotation
curves and gravitational lensing can be used to determine the equation of state
of the dark matter. Alternatively, if the equation of state is known from other
observations, rotation curves and gravitational lensing can together be used to
test General Relativity on galaxy scales.


title:
The Composition of the Interstellar Medium towards the Lockman Hole. HI,
  UV and X-ray observations

abstract:
  The Lockman Hole is well known as the region with the lowest neutral atomic
hydrogen colum density on the entire sky. We present an analysis of the soft
X-ray background radiation towards the Lockman Hole using ROSAT all-sky survey
data. This data is correlated with the Leiden/Dwingeloo survey (Galactic HI
21cm-line emission) in order to model the soft X-ray background by using
radiative transfer calculations for four ROSAT energy bands simultaneously. It
turns out, that an important gas fraction, ranging between 20-50%,of the X-ray
absorbing material is not entirely traced by the HI but is in the form of
ionized hydrogen. Far-ultraviolet absorption line measurements by FUSE are
consistent with this finding and support an ionized hydrogen component towards
the Lockman Hole.


title:
Faster Background Determination - a method for gaining time coverage and
  flux measurement accuracy with Cherenkov telescopes

abstract:
  An improved way of taking off-source data for background determination in
Cherenkov telescope observations is proposed. Generalizing the traditional
concept of taking on-source/off-source observations of equal duration (e.g. 30
minutes ON followed by 30 minutes OFF), Faster Background Determination (FBD)
permits an off-source observation with the same zenith angle distribution as
the on-source observation to be obtained within less time. The method permits
the on-source observation time to be maximized without compromising the quality
of the background determination. It also increases the signal significance for
strong sources. The only modification necessary in the data acquisition is a
small change to the tracking algorithm. The only modification necessary in the
data analysis is to introduce a time normalization which does not increase the
systematic errors. The method could become the normal observing mode for
Cherenkov telescopes when observing strong sources.


title: Update on String Theory

abstract:
  The first part of this report gives a very quick sketch of how string theory
concepts originated and evolved during its first 25 years (1968-93). The second
part presents a somewhat more detailed discussion of the highlights of the past
decade. The final part discusses some of the major problems that remain to be
solved.


title:
The Reuven Ramaty High Energy Solar Spectroscopic Imager observation of
  the 1809 keV line from Galactic 26Al

abstract:
  Observations of the central radian of the Galaxy by the Reuven Ramaty High
Energy Solar Spectroscopy Imager (RHESSI) have yielded a high-resolution
measurement of the 1809 keV line from 26Al, detected at 11 sigma significance
in nine months of data. The RHESSI result for the width of the cosmic line is
2.03 (+0.78, -1.21) keV FWHM. The best fit line width of 5.4 keV FWHM reported
by Naya et al. (1996) using the Gamma-Ray Imaging Spectrometer (GRIS) balloon
instrument is rejected with high confidence.


title:
Effects of Systematic Uncertainties on the Supernova Determination of
  Cosmological Parameters

abstract:
  Mapping the recent expansion history of the universe offers the best hope for
uncovering the characteristics of the dark energy believed to be responsible
for the acceleration of the expansion. In determining cosmological and
dark-energy parameters to the percent level, systematic uncertainties impose a
floor on the accuracy more severe than the statistical measurement precision.
We delineate the categorization, simulation, and understanding required to
bound systematics for the specific case of the Type Ia supernova method. Using
simulated data of forthcoming ground-based surveys and the proposed space-based
SNAP mission we present Monte Carlo results for the residual uncertainties on
the cosmological parameter determination. The tight systematics control with
optical and near-infrared observations and the extended redshift reach allow a
space survey to bound the systematics below 0.02 magnitudes at z=1.7. For a
typical SNAP-like supernova survey, this keeps total errors within 15% of the
statistical values and provides estimation of Omega_m to 0.03, w_0 to 0.07, and
w' to 0.3; these can be further improved by incorporating complementary data.


title: A Luminous Recurrent Supersoft X-ray Source in NGC 300

abstract:
  We report the results of XMM-Newton observations for an especially luminous
supersoft X-ray source (SSS) with bolometric luminosity of 10^39 erg/s in the
spiral galaxy NGC 300. The source was detected as a SSS in 1992 and disappeared
in subsequent X-ray observations. The source was active again during recent
XMM-Newton observations. It appeared to be very soft (kT~60 eV) and very
luminous (~10^38 - 10^39 erg/s). The two XMM-Newton observations also reveal
that the source went from a ``high'' state to a ``low'' state in 6 days. We
also found a 5.4-hr periodicity during the ``low'' state. We consider white
dwarf, black hole, and neutron star models to explain the nature of the source.


title:
Local Three-Dimensional Simulations of Magneto-Rotational Instability in
  Radiation-Dominated Accretion Disks

abstract:
  We examine the small-scale dynamics of black hole accretion disks in which
radiation pressure exceeds gas pressure. Local patches of disk are modeled by
numerically integrating the equations of radiation MHD in the flux-limited
diffusion approximation. The shearing-box approximation is used, and the
vertical component of gravity is neglected. Magneto-rotational instability
(MRI) leads to turbulence in which accretion stresses are due primarily to
magnetic torques. When radiation is locked to gas over the length and time
scales of fluctuations in the turbulence, the accretion stress, density
contrast, and dissipation differ little from those in the corresponding
calculations with radiation replaced by extra gas pressure. However, when
radiation diffuses each orbit a distance that is comparable to the RMS vertical
wavelength of the MRI, radiation pressure is less effective in resisting
squeezing. Large density fluctuations occur, and radiation damping of
compressive motions converts PdV work into photon energy. The accretion stress
in calculations having a net vertical magnetic field is found to be independent
of opacity over the range explored, and approximately proportional to the
square of the net field. In calculations with zero net magnetic flux, the
accretion stress depends on the portion of the total pressure that is effective
in resisting compression. The stress is lower when radiation diffuses rapidly
with respect to the gas. We show that radiation-supported Shakura-Sunyaev disks
accreting via internal magnetic stresses are likely in their interiors to have
radiation marginally coupled to turbulent gas motions.


title:
The three dimensional power spectrum of dark and luminous matter from
  the VIRMOS-DESCART cosmic shear survey

abstract:
  We present the first optimal power spectrum estimation and three dimensional
deprojections for the dark and luminous matter and their cross correlations.
The results are obtained using a new optimal fast estimator (Pen 2003)
deprojected using minimum variance and SVD techniques. We show the resulting
3-D power spectra for dark matter and galaxies, and their covariance for the
VIRMOS-DESCART weak lensing shear and galaxy data. The survey is most sensitive
to nonlinear scales k_NL ~ 1 h Mpc^-1. On these scales, our 3-D power spectrum
of dark matter is in good agreement with the RCS 3-D power spectrum found by
(Hoekstra et al 2002). Our galaxy power is similar to that found by the 2MASS
survey, and larger than that of SDSS, APM and RCS, consistent with the expected
difference in galaxy population.
  We find an average bias b=1.24+/-0.18 for the I selected galaxies, and a
cross correlation coefficient r=0.75+/-0.23. Together with the power spectra,
these results optimally encode the entire two point information about dark
matter and galaxies, including galaxy-galaxy lensing. We address some of the
implications regarding galaxy halos and mass-to-light ratios. The best fit
``halo'' parameter h=r/b=0.57+/-0.16, suggesting that dynamical masses
estimated using galaxies systematically underestimate total mass.
  Ongoing surveys, such as the Canada-France-Hawaii-Telescope-Legacy survey
will significantly improve on the dynamic range, and future photometric
redshift catalogs will allow tomography along the same principles.


title: Fast Power Spectrum Estimation

abstract:
  We present a new algorithm to rapidly and optimally compute power spectra.
This new algorithm is based on a generalization of iterative multigrid, and has
computational cost O(N log N), compared to the standard brute force approach
which costs O(N^3). The procedure retains this speed on the full sky and for
ill-conditioned matrices. It is applicable to galaxy power spectra, CMB,
polarization and weak lensing data. We present a mathematical convergence
analysis, and performance results.


title: The local black-hole mass function from 2dFGRS radio galaxies

abstract:
  Radio emission from early-type (E and S0) galaxies usually signals the
presence of a central supermassive black hole. If radio luminosity and
black-hole mass are correlated, then we can use the large sample of radio
galaxies observed in the 2dF Galaxy Redshift Survey (2dFGRS) to estimate the
local (z<0.1) black-hole mass function for early-type galaxies. Integrating
over this mass function yields a local black-hole mass density of Rho_BH = 1.8
(+0.4, -0.6) x 10^5 solar mases/Mpc^3 (for Ho = 50 km/s/Mpc), in good agreement
both with the local value derived from galaxy velocity dispersions and with the
high-redshift value derived from QSOs. This supports earlier suggestions that
local radio galaxies are the direct descendants of most or all of the
high-redshift QSOs.


title: Signatures of QCD Phase Transition in a Newborn Compact Star

abstract:
  We study the scenario that a new born strange quark star cools to the Quantum
ChromoDynamics (QCD) phase transition temperature and converts to a neutron
star, and we calculate the evolution of temperature and luminosity of the
compact star. We argue that the conversion energy released can be of the order
$10^{53}$ erg. We also propose that a second neutrino burst will be emitted at
the completion of this phase transition.


title: A VLT spectroscopic study of the ultracompact HII region G29.96-0.02

abstract:
  A high quality, medium-resolution K-band spectrum has been obtained of the
ultracompact HII region G29.96-0.02 with the Very Large Telescope (VLT). The
slit was positioned along the symmetry axis of the cometary shaped nebula.
Besides the spectrum of the embedded ionizing O star, the long-slit observation
revealed the rich emission-line spectrum produced by the ionized nebula with
sub-arcsec spatial resolution. The nebular spectrum includes Br$\gamma$,
several helium emission lines and a molecular hydrogen line. A detailed
analysis is presented of the variation in strength, velocity and width of the
nebular emission lines along the slit. The results are consistent with previous
observations, but the much better spatial resolution allows a critical
evaluation of models explaining the cometary shape of the nebula. Our
observations support neither the wind bow shock model nor the champagne flow
model. The measured line ratios of the nebular hydrogen and helium lines are
compared to predictions from case B recombination-line theory. The results
indicate an electron temperature between 6400 and 7500 K, in good agreement
with other determinations and the Galactocentric distance of 4.6 kpc. The
He$^{+}$/H$^{+}$ ratio is practically constant over the slit; we argue that He
is singly ionized throughout the nebula. We review the various observational
constraints on the effective temperature of the ionizing star and show that
these are in agreement with its K-band spectral type of O5-O6V.


title: CVcat: an interactive database on cataclysmic variables

abstract:
  CVcat is a database that contains published data on cataclysmic variables and
related objects. Unlike in the existing online sources, the users are allowed
to add data to the catalogue. The concept of an ``open catalogue'' approach is
reviewed together with the experience from one year of public usage of CVcat.
New concepts to be included in the upcoming AstroCat framework and the next
CVcat implementation are presented. CVcat can be found at http://www.cvcat.org.


title: Rotating models for evolved low-mass stars

abstract:
  Low mass stars (< 2-2.5 M_sun) exhibit, at all the stages of their evolution,
signatures of processes that require challenging modeling beyond the standard
stellar theory. In this paper we focus on their peculiarities while they climb
the red giant branch (RGB). We first compare the classical predictions for
abundance variations due to the first dredge-up with observational data in
various environments. We show how clear spectroscopic diagnostics probe the
nucleosynthesis and the internal mixing mechanisms that drive RGB stars.
Coherent data reveal in particular the existence of a non-standard mixing
process that changes their surface abundances at the so-called RGB bump. By
reviewing the models presented so far to explain the various abundance
anomalies, we show that the occurrence of this extra-mixing process is
certainly related to rotation. Finally we discuss the so-called Li-flash which
is expected to occur at the very beginning of the extra-mixing episode.


title:
Is Praesepe really different from the coeval Hyades cluster? The
  XMM-Newton view

abstract:
  The Praesepe open cluster represents a puzzle since it has about the same age
as the Hyades, and only slightly different metallicity, yet previous ROSAT
observations resulted in a detection rate of cluster sources significantly
lower than for the Hyades. We present a new 50 ksec observation of Praesepe
performed with the EPIC instrument on board XMM-Newton, which resulted in the
detection of ~ 200 sources, including 48 cluster members. We detected all
solar-type (F-G) stars in the field of view, 90% of the K stars and 70% of the
M stars. We find that the distribution of X-ray luminosities of solar-type
Praesepe members is comparable to that of the Hyades, in contrast with the
previous ROSAT results; however, the disagreement between the ROSAT and
XMM-Newton results appears to be mostly due to X-ray faint Praesepe members
falling outside the XMM-Newton field of view, while it is considerably reduced
when considering only the subsample of stars in the ROSAT survey in common with
the present observation. The finding supports an earlier suggestion that
Praesepe may be formed by two merged clusters of different age.


title: The Impact of the Chrono-geometrical Structure of Spacetime on Causality

abstract:
  We discuss the usual account of causal structure that relies on the temporal
precedence constraint between cause-effect pairs. In particular, we consider
the subtle interplay between local and global characters of time and causality
encoded in General Relativity. We find that the temporal precedence constraint
must be relaxed. We argue that these results could lead to an enriched
structure of the physical causality.


title: XMM-Newton Observations of the Field of Gamma-Ray Burst 980425

abstract:
  The error box of GRB980425 has been observed by XMM-Newton in March 2002,
with the aim of measuring the late epoch X-ray emission of the supernova 1998bw
and of clarifying its supposed association with the GRB itself. We present here
the preliminary results obtained with the EPIC PN camera. Our observations
confirm the association between SN 1998bw and GRB980425. The EPIC PN
measurement of the SN 1998bw flux is significantly below the extrapolation of
the power-law temporal trend fitted to the BeppoSAX points and implies a faster
temporal decay. We propose different physical interpretations of the SN X-ray
light curve, according to whether it is produced by one or more radiation
components.


title: Core radius evolution of star clusters

abstract:
  We use N-body simulations of star clusters to investigate the possible
dynamical origins of the observed spread in core radius among intermediate-age
and old star clusters in the Large Magellanic Cloud (LMC). Two effects are
considered, a time-varying external tidal field and variations in primordial
hard binary fraction. Simulations of clusters orbiting a point-mass galaxy show
similar core radius evolution for clusters on both circular and elliptical
orbits and we therefore conclude that the tidal field of the LMC has not yet
significantly influenced the evolution of the intermediate-age clusters. The
presence of large numbers of hard primordial binaries in a cluster leads to
core radius expansion; however, the magnitude of the effect is insufficient to
explain the observations. Further, the range of binary fractions required to
produce significant core radius growth is inconsistent with the observational
evidence that all the LMC clusters have similar stellar luminosity functions.


title: The nature of X-ray spectral variability in Seyfert Galaxies

abstract:
  We use a model-independent technique to investigate the nature of the 2-15
keV X-ray spectral variability in four Seyfert galaxies and distinguish between
spectral pivoting and the two-component model for spectral variability. Our
analysis reveals conclusively that the softening of the X-ray continuum with
increasing flux in MCG -6-30-15 and NGC 3516 is a result of summing two
spectral components: a soft varying component (SVC) with spectral shape
independent of flux and a constant hard component (HCC). In contrast, the
spectral variability in NGC 4051 can be well described by simple pivoting of
one component, together with an additional hard constant component. The
spectral variability model for NGC 5506 is ambiguous, due to the smaller range
of fluxes sampled by the data. We investigate the shape of the hard spectral
component in MCG -6-30-15 and find that it appears similar to a pure reflection
spectrum, but requires a large reflected fraction (R>3). We briefly discuss
physical interpretations of the different modes of spectral variability.


title:
Gravitational Field of Static Thin Planar Walls in Weak-Field
  Approximation

abstract:
  We investigate gravitational properties of thin planar wall solutions of the
Einstein's equations in the weak field approximation. We find the general
metric solutions and discuss the behavior of a particle placed initially at
rest to one side of the plane. Moreover we study the case of
non-reflection-symmetric solutions.