title:
The properties of field elliptical galaxies at intermediate redshift.
  III: the Fundamental Plane and the evolution of stellar populations from
  z~0.4 to z=0

abstract:
  We report on the study of a sample of 25 field early-type galaxies, in the
redshift range z~0.1-0.5, selected on the basis of colours and morphology from
the HST-MDS. Field early-type galaxies define a tight Fundamental Plane (FP)
out to z~0.4, with scatter unchanged with respect to local samples, within the
observational errors. The intermediate redshift FP is offset with respect to
the FP of the Coma Cluster. The offset of the FP is found to increase with
redshift. The evolution of the FP is studied quantitatively with a
Bayesian-Montecarlo technique. By applying this technique, we find that the
offset of the intercept of the FP (\Delta \gamma) with respect to the local FP
increases as \Delta \gamma = \tau z with the following 68 per cent limits:
0.33<\tau<0.44 (for \Omega=1, \Omega_{\Lambda}=0) or 0.44<\tau<0.56 (for
\Omega=0.3,\Omega_{\Lambda}=0.7). In addition, we interpret the results in
terms of the evolution of the stellar populations, under the assumption of
passive evolution. In a single-burst scenario, the observed properties are
consistent with those of a stellar population formed at z>2 (for \Omega=1,
\Omega_{\Lambda}=0, H_0=50 \kms Mpc^{-1}) or 0.8<z<1.6 (for \Omega=0.3,
\Omega_{\Lambda}=0.7, H_0=65 \kms Mpc^{-1}). If a small fraction of the stellar
mass is formed in a secondary burst, the primary burst may have occurred at
higher z. Finally, the intercept and scatter of the FP found for field
early-type galaxies and for cluster data at z~0.4 are mutually consistent,
within the observational errors. If higher redshift (up to z=0.83) cluster data
are considered, the ages of the stellar populations of field early-type
galaxies inferred from a single-burst scenario are found to be marginally
smaller than the ages derived for the cluster galaxies. [shortened]


title: Kinematics of Globular Clusters in M49 and M87

abstract:
  We present recent multi-object spectroscopy of globular clusters in the Virgo
gEs M49 and M87. In M49, we have a total of 144 confirmed clusters out to 8
arcmin radius (~6 R_eff or 35 kpc). We find that the blue (metal-poor) clusters
have both a higher velocity dispersion and rotation than the red (metal-poor)
clusters. For the metal-rich population we place an upper limit of
(v/sigma)_proj < 0.34 at 99% confidence. We calculate the velocity dispersion
as a function of radius, and show that this is consistent with isotropic
cluster orbits and the M49 mass distribution determined from X-ray data. For
M87, we combine new CFHT data with previous data to obtain a total sample of
278 clusters out to 10 arcmin radius (~45 kpc). We find a similar global
rotation for the metal-poor and metal-rich clusters of 160-170 km/sec. Beyond ~
2 R_eff (15 kpc), both the metal-poor and metal-rich clusters appear to rotate
about the photometric minor axis. The combined cluster sample is consistent
with isotropic orbits, but when considered separately, the metal-poor clusters
show significant tangential bias of beta_cl ~ -0.4, while the metal-rich
clusters show a radial bias with beta_cl ~ +0.4. In both galaxies, the
metal-rich and metal-poor clusters share different kinematics, but there is no
clear preference for any one formation scenario.


title: Cosmology as seen from Venice

abstract:
  The flat matter dominated Universe that dominated cosmological model building
for much of the past 20 years does not correspond to the Universe in which we
live. This has profound implications both for our understanding of dark matter,
and also for our understanding of the future of the Universe. I review recent
developments here and present best fits for the current, sometimes crazy,
values of the major measured fundamental cosmological parameters. (Invited
review talk, 9th International Workshop on Neutrino Telescopes, Venice, March
2001. Note: this is an updated version of an article prepared for the
proceedings of IDM2000 in York, UK.)


title: On the nature of X-ray absorption in Seyfert 2 galaxies

abstract:
  We have studied the correlation among X-ray absorption, optical reddening and
nuclear dust morphology in Seyfert 2 galaxies. Two main conclusions emerge: a)
the Balmer decrement and the amount of X-ray absorption are anticorrelated on a
wide range of column density: 10^{21} < N_H < 10^{24} atoms/cm/cm. The
correlation does no longer apply to Compton-thick objects (N_H < 10^{24}
atoms/cm/cm), although they span a comparable range in Balmer decrement; b)
Compton-thin Seyfert 2s seem to prefer nuclear environments, which are rich of
dust on scales of the hundreds parsecs. On the other hand, Compton-thick
Seyferts exhibit indifferently ``dust-poor'' and ``dust-rich'' environments.
These results support an extension of the Seyfert unification scenario (as
recently proposed by Matt, 2000), where Compton-thick Seyfert 2s are observed
through compact ``torii'', whereas Compton-thin ones are obscured by dust on
much larger scales


title: Universal gas density and temperature profile

abstract:
  We present an analytic approach to predict gas density and temperature
profiles in dark matter haloes. We assume that the gas density profile traces
the dark matter density profile in outer parts of the haloes, as suggested by
many hydrodynamic simulations. Under this assumption, the hydrostatic
equilibrium uniquely fixes the two free parameters in the model, the
mass-temperature normalization and the polytropic index, that determine the
temperature profile. This enables us to predict a universal gas profile from
any universal dark matter profile. Our results show that gas tracing dark
matter in the outer parts of the haloes is inconsistent with gas being
isothermal; on the contrary, it requires temperature to decrease slowly with
radius, in agreement with observations. We compare our predictions for X-ray
surface brightness profiles of the haloes and the mass-temperature relation
with observations. We find that they are generally in a good agreement. We
compare the universal profile with the beta profile and find that, although the
beta profile gives a reasonable fit to our predicted profiles, the deviation
from it can explain many of the observed trends, once we take into account the
observational selection effects. Our model predicts that the mass-temperature
relation does not follow the self-similar relation because of the
mass-dependent halo concentration. We also predict surface brightness profiles
of the Sunyaev-Zel'dovich (SZ) effect. We find that fitted to the beta profile
the core radii and beta inferred from the SZ effect are systematically larger
than those from the X-ray measurement.


title:
Archeops: A High Resolution, Large Sky Coverage Balloon Experiment for
  Mapping CMB Anisotropies

abstract:
  Archeops is a balloon-borne instrument dedicated to measuring cosmic
microwave background (CMB) temperature anisotropies at high angular resolution
(8 arcminutes) over a large fraction (25%) of the sky in the millimetre domain.
Based on Planck High Frequency Instrument (HFI) technology, cooled bolometers
(0.1 K) scan the sky in total power mode with large circles at constant
elevation. During the course of a 24-hour Arctic-night balloon flight, Archeops
will observe a complete annulus on the sky in four frequency bands centered at
143, 217, 353 and 545 GHz with an expected sensitivity to CMB fluctuations of
\~100muK for each of the 90 thousand 20 arcminute average pixels. We describe
the instrument and its performance obtained during a test flight from Trapani
(Sicily) to Spain in July 1999.


title: Electrical Conductivity at the Core of a Magnetar

abstract:
  An expression for the electrical conductivity at the core of a magnetar is
derived using Boltzmann kinetic equation with the relaxation time
approximation. The rates for the relevant scattering processes, e.g.,
electron-electron and electron-proton are evaluated in presence of strong
quantizing magnetic fields using tree level diagrams. It is found that in
presence of a strong quantizing magnetic field, electrical conductivity behaves
like a second rank tensor. However, if the zeroth Landau levels are only
occupied by the charged particles, it again behaves like a scaler of a one
dimensional system.


title:
Generation of Cosmic Magnetic Fields and Gravitational Waves at Neutrino
  Decoupling

abstract:
  We show that an inhomogeneous cosmological lepton number may have produced
turbulence in the primordial plasma when neutrinos entered (almost)
free-streaming regime. This effect may be responsible for the origin of cosmic
magnetic fields and give rise to a detectable background of gravitational
waves. An existence of inhomogeneous lepton asymmetry could be naturally
generated by active-sterile neutrino oscillations or by some versions of
Affleck and Dine baryogenesis scenario.


title: Far-Infrared Census of Starburst-Seyfert Connection

abstract:
  Far-infrared flux densities are newly extracted from the IRAS database for
the RSA and CfA complete samples of Seyfert galaxies. These data are used to
classify the Seyfert galaxies into those where the far-infrared continuum
emission is dominated by the active galactic nucleus (AGN), circumnuclear
starburst, or host galaxy.
  While AGN-dominant objects consist of comparable numbers of Seyfert 1 and 2
galaxies, starburst- and host-dominant objects consist preferentially of
Seyfert 2 galaxies. Thus, in addition to the dusty torus, the circumnuclear
starburst region and host galaxy are important in hiding the broad-line region.
  Morphologically, starburst-dominant Seyfert galaxies are of later types and
more strongly interacting than AGN-dominant Seyfert galaxies. In a later-type
galaxy, the AGN central engine has a lower Eddington luminosity, and the
gaseous content is higher. The gas is efficiently supplied to the starburst via
a galaxy-galaxy interaction. Morphologies of host-dominant Seyfert galaxies are
of various types.
  Since starbursts in Seyfert galaxies are older than those in classical
starburst galaxies, we propose an evolution from starburst to
starburst-dominant Seyfert to host-dominant Seyfert for a late-type galaxy. An
evolution from AGN-dominant Seyfert to host-dominant Seyfert is proposed for an
early-type galaxy. These sequences have durations of a few x 10^8 yr and occur
repeatedly within a galaxy during its evolution from a late type to an early
type.


title: The fragmentation of expanding shells: cloud formation rates and masses

abstract:
  The gravitational instability of expanding shells is discussed. Linear and
nonlinear terms are included in an analytical solution in the static and
homogeneous medium. We discuss the interaction of modes and give the time
needed for fragmentation. Masses of individual fragments are also estimated and
their formation rates and the initial mass function are derived. Results of
simulations are compared to observation.


title:
Comparative Studies of Line and Continuum Positron Annihilation
  Radiation

abstract:
  Positron annihilation radiation from the Galaxy has been observed by the
OSSE, SMM and TGRS instruments. Improved spectral modeling of OSSE observations
has allowed studies of the distribution of both positron annihilation radiation
components, the narrow line emission at 511 keV and the positronium continuum
emission. The results derived for each individual annihilation component are
then compared with each other. These comparisons reveal approximate agreement
between the distribution of these two emissions. In certain regions of the sky
(notably in the vicinity of the previously reported positive latitude
enhancement), the distribution of the emissions differ. We discuss these
differences and the methods currently being employed to understand whether the
differences are physical or a systematic error in the present analysis.


title:
On the reliability of peak-flux distributions, with an application to
  solar flares

abstract:
  Narrow-band radio spikes have been recorded during a solar flare with
unprecedented resolution. This unique example allows to study the effect of low
resolution in previously published peak-flux distributions of radio spikes. We
give a general, analytical expression for how an actual peak-flux distribution
is changed in shape if the peaks are determined with low temporal and/or
frequency resolution. It turns out that, generally, low resolution tends to
cause an exponential behavior at large flux values if the actual distribution
is of power-law shape. The distribution may be severely altered if the
burst-duration depends on the peak-flux. The derived expression is applicable
also to peak-flux distributions derived at other wavelengths (e.g. soft and
hard X-rays, EUV). We show that for the analyzed spike-event the resolution was
sufficient for a reliable peak flux distribution. It can be fitted by
generalized power-laws or by an exponential.


title: The Velocity Distribution of Isolated Radio Pulsars

abstract:
  (Abridged) We infer the velocity distribution of radio pulsars by modelling
their birth, evolution, and detection in large-scale 0.4 GHz pulsar surveys,
and by comparing model distributions of measurable pulsar properties with
survey data using a likelihood function. We test models that characterize a
population's birth rate, luminosity, shutoff of radio emission, birth
locations, and birth velocities. We infer that the radio beam luminosity (i) is
comparable to the energy flux of relativistic particles in models for
spin-driven magnetospheres, signifying that radio emission losses reach nearly
100% for the oldest pulsars; and (ii) scales approximately as sqrt(Edot) which,
in magnetosphere models, is proportional to the voltage drop available for
acceleration of particles. We find that a two-component velocity distribution
with characteristic velocities of 90 km/s and 500 km/s is greatly preferred to
any one-component distribution. We explore some consequences of the preferred
birth velocity distribution: (i) roughly 50% of pulsars in the solar
neighborhood will escape the Galaxy, while ~15% have velocities greater than
1000 km/s; (ii) an important low-velocity population exists that increases the
fraction of neutron stars retained by globular clusters and is consistent with
the number of old objects that accrete from the interstellar medium; (iii)
under standard assumptions for supernova remnant expansion and pulsar
spin-down, ~10% of pulsars younger than 20 kyr will appear to lie outside of
their host remnants. Finally, we comment on the ramifications of our birth
velocity distribution for binary survival and the population of inspiraling
binary neutron stars relevant to some GRB models and potential sources for
LIGO.


title: Radial Velocity Studies of Close Binary Stars.V

abstract:
  Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the fifth set of ten close binary systems: V376
And, EL Aqr, EF Boo, DN Cam, FN Cam, V776 Cas, SX Crv, V351 Peg, EQ Tau, KZ
Vir. All systems are double-lined spectroscopic contact binaries (KZ Vir may be
a low inclination, close, non-contact binary), with seven (all except EL Aqr,
SX Crv and EQ Tau) being the recent photometric discoveries of the Hipparcos
satellite project. The most interesting object is SX Crv, a contact system with
an unprecedently low mass ratio, q=0.066+/-0.003, whose existence challenges
the current theory of tidal stability of contact systems. Several of the
studied systems are prime candidates for combined light and radial-velocity
synthesis solutions.


title:
Identifying the Mysterious EGRET Sources: Signatures of Polar Cap Pulsar
  Models

abstract:
  The advent of the next generation of gamma-ray experiments, led by GLAST,
AGILE, INTEGRAL and a host of atmospheric \v{C}erenkov telescopes coming on
line in the next few years, will enable ground-breaking discoveries relating to
the presently enigmatic set of EGRET/CGRO UID galactic sources that have yet to
find definitive identifications. Pulsars are principal candidates for such
sources, and many are expected to be detected by GLAST, some that are
radio-selected, like most of the present EGRET/Comptel pulsars, and perhaps
even more that are detected via independent pulsation searches. At this
juncture, it is salient to outline the principal predictions of pulsar models
that might aid identification of gamma-ray sources, and moreover propel
subsequent interpretation of their properties. This review summarizes relevant
characteristics of the polar cap model, emphasizing where possible distinctions
from the competing outer gap model. Foremost among these considerations are the
hard X-ray to gamma-ray spectral shape, high energy cutoffs and pulse profiles,
and how these characteristics generally depend on pulsar period and period
derivative, as well as observational viewing angle. The polar cap model
exhibits definitive signatures that will be readily tested by the detections of
GLAST and other experiments, thereby establishing cogent observational
diagnostics. The paper focuses on different classes of pulsars that might
define agendas and parameter regimes for blind gamma-ray pulsation searches;
examples include the highly-magnetized ones that are currently quite topical in
astrophysics.


title: The Supermassive Black Hole at the Galactic Center

abstract:
  The inner few parsecs at the Galactic Center have come under intense scrutiny
in recent years, in part due to the exciting broad-band observations of this
region, but also because of the growing interest from theorists motivated to
study the physics of black hole accretion, magnetized gas dynamics and unusual
star formation. The Galactic Center is now known to contain arguably the most
compelling supermassive black hole candidate, weighing in at a little over 2.6
million suns. Its interaction with the nearby environment, comprised of
clusters of evolved and young stars, a molecular dusty ring, ionized gas
streamers, diffuse hot gas, and a hypernova remnant, is providing a wealth of
accretion phenomenology and high-energy processes for detailed modeling. In
this review, we summarize the latest observational results, and focus on the
physical interpretation of the most intriguing object in this region---the
compact radio source Sgr A*, thought to be the radiative manifestation of the
supermassive black hole.


title:
Spectroscopic Signatures of Conduction-Mediated Transition Layers Above
  an X-ray Illuminated Disk

abstract:
  We derive a semi-analytic solution for the structure of conduction-mediated
transition layers above an X-ray illuminated accretion disk, and calculate
explicitly the X-ray line radiation resulting from both resonance line
scattering and radiative recombination in these layers. The vertical thermal
structure of the illuminated disk is found to depend on the illuminating
continuum: for a hard power law continuum, there are two stable phases
connected by a single transition layer; while for a softer continuum, there may
exist three stable phases connected by two separate transition layers, with an
intermediate stable layer in between. We show that the structure can be written
as a function of the electron scattering optical depth through these layers,
which leads to unique predictions of the equivalent width of the resulting line
radiation from both recombination cascades and resonance line scattering. We
find that resonance line scattering plays an important role, especially for the
case where there is no intermediate stable layer.


title: Sources of carbon and the evolution of the abundance of CNO elements

abstract:
  Using the standard infall model of Galactic chemical evolution, we explore
the origin of carbon and calculate the abundance evolution of CNO elements for
8 different models of stellar nucleosynthesis yields. The results show that, in
the early stage of the Galaxy, massive stars are the main producer of carbon,
and that as our Galaxy evolves to the late stage, the longer lived
intermediate- and low-mass stars play an increasingly important role, while at
the same time, metal-rich Wolf-Rayet stars eject a significant amount of carbon
into the ISM by radiative-driven stellar winds. However, from the present
published nucleosynthesis yields we cannot distinguish whether the main source
of carbon in the late Galactic stage is just the massive stars ($M>8M_{\odot}$)
alone, or just the intermediate-, low-mass stars and $M\leq 40M_{\odot}$
massive stars that do not go through the Wolf-Rayet stage. The
$^{12}$C$(\alpha,\gamma)^{16}$O reaction rate is very important in the stellar
nucleosynthesis calculations: a lower rate will give a higher yield of carbon.
The contribution to nitrogen is dominated by intermediate- and low-mass stars,
and the secondary source of massive stars cannot explain the observed [N/Fe] in
metal-poor stars. Most of oxygen is produced by massive stars. The fact that a
higher O abundance in metal-poor stars is derived from the \ion{O}{i}
7771$-$7775 \AA triplet than from the forbidden [\ion{O}{i}] line at 6300 \AA
poses a problem.


title: The nuclear starburst activity in the Seyfert 2 galaxy NGC 7679

abstract:
  We present our recent spectrophotometric results of the infrared luminous
Seyfert 2 galaxy NGC 7679. We find compelling evidence of the presence of a
recent nuclear starburst, revealed by the observations of a) the spectral
features of high order Balmer absorption lines, b) the weak equivalent widths
for CaIIK $\lambda$3933, CN $\lambda$4200, G-band $\lambda$4300 and MgIb
$\lambda$5173, and c) the suggested UV stellar wind resonance lines (N V
$\lambda$1240, Si IV $\lambda$1400 and C IV $\lambda$1550) in the IUE spectrum.
Using the simple stellar population synthesis model, we find that in the
nuclear 2" $\times$ 2" region, the contributions from the old, intermediate and
young components are 21.7%, 42.9% and 35.4%, respectively. These nuclear
starburst activities might be triggered by the close encounter with NGC 7682,
as suggested by recent numerical simulations.


title: WFPC2 Observations of Two dSph Galaxies in the M81 Group

abstract:
  We have obtained HST WFPC2 and ground-based images of two low surface
brightness dwarf spheroidal galaxies in the M81 group, FM1 and KKH57. Their
colour-magnitude diagrams show red giant branches with tips at I = 23.77 +-
0.14 and I = 23.97 +- 0.17, respectively. The derived true distance moduli,
27.66 +- 0.16 and 27.96 +- 0.19, agree well with the mean distance modulus of
the M81 group, 27.84 +- 0.05. Absolute V magnitudes of the galaxies (-11.46 and
-10.85), their colours ((B-V) = 0.88 and 0.80), and central surface
brightnesses ($\Sigma_{0,V}$ = 24.8 and 24.4 mag/$\sq\arcsec$) are in the range
of other dSph companions of M81, M31, and Milky Way. With two new objects the
maximum projected radius of the dwarf spheroidal subsystem around M81 is 380
kpc.


title: RR Lyrae stars in the Sagittarius dwarf galaxy: Period analysis

abstract:
  (Abridged) We carried out a period analysis on ~3700 RR Lyrae stars spread
over ~50 square degrees towards the Sagittarius dwarf galaxy (Sgr). The RR
Lyraes are distributed almost evenly between Sgr and the Milky Way. For Sgr
members, the average periods are 0.574 day and 0.322 day for RRab and RRc stars
respectively. This places Sgr in the long-period tail of the Oosterhoff I
group. We report the detection of 53 double-mode RR Lyrae stars (RRd) within
our sample. The magnitude of 40 of these stars is consistent with membership in
Sgr whereas 13 RRds are located within our Galaxy. We also found 13 RR Lyraes
(5 in Sgr and 8 in the Galaxy) exhibiting two closely spaced frequencies, most
probably related to non-radial pulsations. The period distribution of the RR
Lyrae variables in Sgr is compared to those of other Milky Way satellites. We
find a remarkable similarity between the RR Lyrae populations in Sgr and the
Large Magellanic Cloud (LMC), suggesting that these galaxies have similar
horizontal branch morphologies. This may indicate that Sgr and the LMC started
their formation under similar conditions. Using various photometric indicators,
we estimate the metallicity of the RR Lyrae stars in Sgr and find <[Fe/H]>~-1.6
dex with a dispersion of ~ +/-0.5 dex around this value and a minor but
significant population at <-2.0 dex. We do not find evidence for a spatial
metallicity gradient in the RR Lyrae population of Sgr. From the spatial
distribution of RR Lyraes, we estimate the RRab content and total luminosity of
this galaxy and find MV(Sgr)~-14.7 mag, a value that would be consistent with
the empirical metallicity/luminosity relation for Dsph galaxies.


title: Spectropolarimetry of Broad H_alpha Lines and Geometry of the BLR

abstract:
  In a small fraction of Broad Line Radio Galaxies (BLRG) and Seyfert 1
galaxies, the polarization position angle rotates across the broad emission
lines, especially at H_alpha. An understanding of this behavior can potentially
yield important information on the scattering geometry in the nucleus. We show
two examples of this phenomenon, 3C 445, a BLRG, and Mrk 231, a Seyfert 1, and
present an equatorial scattering model that explains some of its features in a
straightforward way.


title:
Possible Signatures of Quark-Hadron Phase Transitions inside Neutron
  Stars

abstract:
  The spin-down power of an isolated neutron star can drive its central density
increase and overall structural changes, and trigger a quark-hadron phase
transition. A series of observational signatures may be seen as a result of the
phase transition, including pulsar spin-down and glitch behaviors, Soft Gamma
Repeaters or Gamma-Ray Bursts.


title: Hidden Blazars and Emission Line Variability of High Redshift Quasars

abstract:
  We have carried out a survey to search for hidden blazars in a sample of
$z{\sim}2$ radio-loud quasars. The idea is based on our prediction that we
should be able to see large CIV line variability not associated with observed
continuum variations or most other emission lines in every radio-loud quasar.
Here we report the initial results including the discovery of large CIV line
variations in two quasars.


title: Discovery of Hidden Blazars

abstract:
  A blazar is believed to exist in every radio-loud quasar. This is expected in
a unified scheme where the differences in both optical and radio observations
of radio-loud quasars are the result of different viewing angles. We have
predicted that blazars may be detected using emission line ratio variations
caused by variable illumination of gas clouds in the broad emission line
region. In a spectroscopic search of 62 quasars at a redshift of about 2, we
have discovered large (>20%) variations of the emission line ratios, CIV/CIII]
or CIV/Ly$\alpha$, when compared with historical data taken over 10 years ago.
This result is consistent with our prediction, and thus supports the
unification scheme for radio-loud quasars.


title:
High Resolution Mid-Infrared Imaging of Infrared Luminous Starburst
  Galaxies

abstract:
  Observations for seven infrared luminous starburst galaxies are reported in
the mid-infrared from 8 - 18 microns using the Keck Telescopes with spatial
resolution approaching the diffraction limit. All of the galaxies observed show
evidence of strong interactions based on optical morphologies. For these
galaxies, a substantial fraction, usually more than 50%, of the infrared
luminosity is generated in regions ranging in sizes from 100pc -- 1 Kpc.
Nuclear starbursts often dominate the infrared luminosity, but this is not
always true. In some galaxies, most notably NGC 6090, substantial infrared
luminosity greatly in excess of the nuclear luminosity is generated in regions
associated with the physical interaction between two galaxies. The radio
emission is a good tracer of the location of high luminosity young stars. The
visual/ultraviolet radiation output of the nearby star forming galaxies is
dominated by emission from regions that are generally not producing the copious
infrared luminosity of the systems. The regions of high infrared luminosity in
local starburst galaxies are significantly smaller than the galaxies as a
whole. The integrated spectral energy distributions (SEDs) of these galaxies
are very different from the SEDs of the regions of star formation. If the SEDs
of star-forming regions in these galaxies reflect the SEDs found in forming
galaxies at high redshift, the distant galaxies should be dominated by the mid
and far-infrared luminosity output far more than the integrated luminous output
of nearby starburst galaxies would suggest.


title:
Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio
  luminosity functions for AGN and star-forming galaxies at 1.4 GHz

abstract:
  We have cross-matched the 1.4 GHz NRAO VLA Sky Survey (NVSS) with the first
210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an
effective area of 325 square degrees (about 20% of the final 2dFGRS area). This
yields a set of optical spectra of 912 candidate NVSS counterparts, of which we
identify 757 as genuine radio IDs - the largest and most homogeneous set of
radio-source spectra ever obtained. The 2dFGRS radio sources span the redshift
range z=0.005 to 0.438, and are a mixture of active galaxies (60%) and
star-forming galaxies (40%). About 25% of the 2dFGRS radio sources are
spatially resolved by NVSS, and the sample includes three giant radio galaxies
with projected linear size greater than 1 Mpc. The high quality of the 2dF
spectra means we can usually distinguish unambiguously between AGN and
star-forming galaxies. We have made a new determination of the local radio
luminosity function at 1.4 GHz for both active and star-forming galaxies, and
derive a local star-formation density of 0.022+/-0.004 solar masses per year
per cubic Mpc. (Ho=50 km/s/Mpc).


title: The nature of the E-B decomposition of CMB polarization

abstract:
  We present a derivation of the transformation between the Q and U Stokes
parameters and the E and B scalar and pseudo-scalar fields. We emphasize the
geometrical properties that such transformation must satisfy. We present the E
and B decomposition of some simple maps and of a model for a supernova remnant.
We discuss the relative amplitudes of the E and B components and argue that for
generic random maps E and B should have roughly the same amplitudes.


title:
Frequency-dependent time lags in the X-ray emission of the Seyfert
  galaxy NGC 7469

abstract:
  We report the discovery of time lags in the cross-spectra of the X-ray light
curves of the Seyfert galaxy NGC 7469. This behavior is common in Galactic
black hole and neutron star binaries, and is in the sense that harder X-rays
are delayed with respect to the soft with a time lag approximately proportional
to the Fourier period. At the longest period probed by our observation we find
a time lag of approximately 3.5 hours between the 2-4 and 4-10 keV X-rays. A
similar lag and period dependence is found comparing the 2-4 and 10-15 keV
light curves, albeit with less significance. We find the coherence function of
the light curves to be close to 1. The implications of these results for the
X-ray production mechanism in active galactic nuclei (AGN) is discussed.


title: Gravitational Lens Statistics and The Density Profile of Dark Halos

abstract:
  We investigate the influence of the inner profile of lens objects on
gravitational lens statistics taking into account of the effect of
magnification bias and both the evolution and the scatter of halo profiles. We
take the dark halos as the lens objects and consider the following three models
for the density profile of dark halos; SIS (singular isothermal sphere), the
NFW (Navarro Frenk White) profile, and the generalized NFW profile which has a
different slope at smaller radii. The mass function of dark halos is assumed to
be given by the Press-Schechter function. We find that magnification bias for
the NFW profile is order of magnitude larger than that for SIS. We estimate the
sensitivity of the lensing probability of distant sources to the inner profile
of lenses and to the cosmological parameters. It turns out that the lensing
probability is strongly dependent on the inner density profile as well as on
the cosmological constant. We compare the predictions with the largest
observational sample, the Cosmic Lens All-Sky Survey. The absence or presence
of large splitting events in larger surveys currently underway such as the 2dF
and SDSS could set constraints on the inner density profile of dark halos.


title:
The role of synchrotron self-absorption in the late radio emission of
  SN1993J

abstract:
  The standard model for radio supernovae considers that the observed
synchrotron radio emission arises from the high-energy shell that results from
the strong interaction between the expanding supernova ejecta and the
circumstellar medium. This emission is considered to be only partially absorbed
by ionized thermal electrons in the circumstellar wind of the progenitor star.
Based on a study of the radio light curves of the type II supernova SN1993J, we
present evidence of synchrotron self-absorption. Our modeling of the radio
light curves requires a large initial magnetic field, of about 30 Gauss, and
the existence of an (initially) highly-relativistic population of electrons. We
also show that while at early epochs the dominant absorption mechanism is
external absorption by thermal electrons, at late epochs and long wavelengths
the dominant absorption mechanism is synchrotron self-absorption. Consequently,
the spectral turnover takes place at much shorter wavelengths than expected in
the standard model, and at long wavelengths (greater than about 90cm at current
epochs) the flux predictions depart substantially from those of the standard
model.


title: A search for nearby young stars among the flare stars

abstract:
  Flare stars were discovered in the late 1940s in the solar vicinity and were
named UV Cet-type variables (classical FSs). Among the FSs within 100 pc we
search for young stars. For the search we take spectra with sufficient
resolution to resolve Lithium at 6707 \AA and Calcium at 6718 \AA of all the
stars. The real young stars are prime targets for the search of extra-solar
planets by direct imaging.


title:
Dynamics of blue compact galaxies, as revealed by their H$\alpha$
  velocity fields II. Mass models and the starburst triggering mechanism

abstract:
  The H$\alpha$ velocity fields of a sample of six luminous blue compact
galaxies (BCGs) and two companions have been obtained by observations with a
scanning Fabry-Perot interferometer. The Fabry-Perot images, velocity fields
and rotations curves have been presented in a previous paper (Paper I). In
general, the velocity fields are irregular and often contain secondary
dynamical components, but display overall rotation. The two companions have
more regular velocity fields and rotation curves. In this article we analyse
the velocity fields and dynamics together with the morphology of the studied
BCGs, and present detailed mass models. In addition, we model the stellar mass
content by means of multicolour surface photometry and spectral evolutionary
synthesis analysis. By comparison of the masses of stars and those derived from
the rotation curve, we show that about half of the galaxies cannot be supported
by rotation alone. The morphology and dynamics of the BCGs suggest that the
starburst activity in these galaxies are most likely triggered by mergers
involving gas-rich dwarf galaxies and/or massive gas clouds.


title: Polarimetric Imaging of the Massive Black Hole at the Galactic Center

abstract:
  The radio source Sgr A* in the Galactic center emits a polarized spectrum at
millimeter and sub-millimeter wavelengths that is strongly suggestive of
relativistic disk accretion onto a massive black hole. We use the
well-constrained mass of Sgr A* and a magnetohydrodynamic model of the
accretion flow to match both the total flux and polarization from this object.
Our results demonstrate explicitly that the shift in the position angle of the
polarization vector, seen at wavelengths near the peak of the mm to sub-mm
emission from this source, is a signal of relativistic accretion flow in a
strong gravitational field. We provide maps of the polarized emission to
illustrate how the images of polarized intensity from the vicinity of the black
hole would appear in upcoming observations with very long baseline radio
interferometers (VLBI). Our results suggest that near-term VLBI observations
will be able to directly image the polarized Keplerian portion of the flow near
the horizon of the black hole.


title: Mirror eclipses in the cataclysmic variable IP Peg

abstract:
  We present time resolved K-band infrared spectra of the dwarf nova (DN) IP
Peg in early quiescence. The Brackett-gamma and HeI lines in our data show
hitherto unseen behaviour, which we term a mirror eclipse, and interpret as an
eclipse of the secondary star by an optically thin accretion disc. Mirror
eclipses are a direct probe of the structure and physical conditions of
accretion discs. For example, on assuming the relevant level populations to be
in LTE, we constrain the temperature and density of the optically thin material
causing the mirror eclipse to be 10,000 < T < 20,000 K and \rho ~10^-11 g/cm^3
respectively. In order to match our data we find that at least the outermost
20% of the disc (in radius) must be entirely optically thin. Implications for
time-dependant disc models are examined.


title: Propagation of UHECRs from the Sources in the Super-Galactic Plane

abstract:
  We have performed the detailed numerical simulations on the propagation of
the UHE protons in the energy range $E=(10^{19.5} - 10^{22.0}$) eV in the
relatively strong extra-galactic magnetic field with strength $B= (10, 100)$ nG
within about 40 Mpc. In this case, the deflection angles of UHECRs become so
large that the no counterparts problem is simply solved. As for the source
distribution, we assumed that it is proportional to the number distribution of
galaxies within the GZK sphere. We have found many clusters, which mean the
small-scale anisotropy, in our simulations. It has been also shown that the
observed energy spectrum is well reproduced in our models without any
fine-tuned parameter. We have used the correlation value in order to
investigate statistically the similarity between the distribution of arrival
directions of UHECRs and that of galaxies. We have found that each correlation
value for each parameter set begins to converge when the number of the detected
events becomes ${\large O}(10^3)$. Since the expected number counts by the
experiment of the next generation such as TA, HiRes, Auger, and EUSO are
thought to be the order of $10^3$, we will be able to determine the source
distribution and values of the parameters in this study in the very near
future. Compared with the AGASA data, the significant anisotropy on the arrival
directions of UHECRs are found in the analysis of first and second harmonics.
This may originate from the incompleteness of the ORS database. This problem
may be also solved if the source distribution is slightly changed. For example,
this problem may be solved if we assume that UHECRs come from some of the
galaxies such as AGNs and radio galaxies.


title: Revealing the Energetics and Structure of AGN Jets

abstract:
  Until very recently, few constraints existed on the physics of jets, even
though they represent the first known evidence of mass outflow in AGN. This has
begun to change with HST and Chandra observations, which allow us to observe
short-lived, dynamic features, and compare their spectra and morphology to
those of longer-lived particles seen in the radio. We examine HST and Chandra
observations of M87 and 3C273 which reveal that these two prototype objects
seem radically different.


title: Altair's Oblateness and Rotation Velocity

abstract:
  We present infrared interferometric angular size measurements for the A7IV-V
star Altair which indicate a non-circular projected disk brightness
distribution. Given the known rapid rotation of this star, we model the data as
arising from an elongated rigid atmosphere. To first order, an ellipse may be
fit to our interferometric diameter measurements, with major and minor axes of
2a=3.461+-0.038 milliarcseconds (mas) and 2b=3.037+-0.069 mas, respectively,
for a difference of 424+-79 microarcseconds between 2a and 2b, and with an
axial ratio of a/b =1.140+-0.029. Assuming that the apparent oblateness of the
photosphere is due to the star's rapid rotation, a more rigorous evaluation of
the observation data in the context of a rigidly rotating Roche model shows
that an estimate of v sin i = 210+-13 km/s can be derived that is independent
of spectroscopic techniques. Also derived are values for the mean effective
temperature, the mean linear radius, and an observational constraint upon the
the relationship between rotation velocity and stellar inclination is
established. Altair is the first main sequence star for which direct
observations of an oblate photosphere have been reported, and the first star
forwhich v sin i has been established from observations of the star's
photospheric geometry.


title: Multiplicity of young brown dwarfs in Cha I

abstract:
  How frequent are brown dwarf binaries? Do brown dwarfs have planets? Are
current theoretical pre-main-sequence evolutionary tracks valid down to the
substellar regime? - Any detection of a companion to a brown dwarf takes us one
step forward towards answering these basic questions of star formation.
  We report here on a search for spectroscopic and visual companions to young
brown dwarfs in the Cha I star forming cloud.
  Based on spectra taken with UVES at the VLT, we found significant radial
velocity (RV) variations for five bona-fide and candidate brown dwarfs in Cha
I. They can be caused by either a (substellar or planetary) companion or
stellar activity. A companion causing the detected RV variations would have
about a few Jupiter masses. We are planning further UVES observations in order
to explore the nature of the detected RV variations. We also found that the RV
dispersion is only ~ 2km/s indicating that there is probably no run-away brown
dwarf among them.
  Additionally a search for companions by direct imaging with the HST and SOFI
(NTT) has yielded to the detection of a few companion candidates in larger
orbits.


title:
The Hamburg/SAO Survey for Emission--Line Galaxies. V. The Fifth List of
  161 Galaxies

abstract:
  We present the fifth list with results of the Hamburg/SAO Survey for
Emission-Line Galaxies (HSS therein, SAO -- Special Astrophysical Observatory,
Russia). The list is a result of follow-up spectroscopy conducted with the 2.2m
CAHA and 4m Kitt Peak telescopes in 1999. The data of this snap-shot
spectroscopy survey confirmed 166 emission-line objects out of 209 observed
candidates and allowed their quantitative spectral classification and redshift
determination. We could classify 98 emission-line objects as BCG/HII galaxies
or probable BCGs, 5 -- as QSOs, 3 - as Seyfert galaxies, 2 - as
super-associations in subluminous spiral galaxies. 25 low-excitation objects
were classified as starburst nuclei (SBN), 24 as dwarf amorphous nuclei
starburst galaxies (DANS) and 3 as LINERs. Due to low signal-to-noise ratio we
could not classify 6 ELGs. Furthermore, for another 4 galaxies we did not
detect any significant emission lines. For 131 emission-line galaxies, the
redshifts and/or line intensities are determined for the first time. For the
remaining 30 previously known ELGs we give either improved data of the line
intensities or some independent measurements.


title:
Heating of the Hot Intergalactic Medium by Powerful Radio Galaxies and
  Associated High Energy Gamma-Ray Emission

abstract:
  There is increasing evidence that some heating mechanism in addition to
gravitational shock heating has been important for the hot gas inside clusters
and groups of galaxies, as indicated by their observed X-ray scaling
properties. While supernovae are the most obvious candidate heating sources, a
number of recent studies have suggested that they may be energetically
insufficient. Here we consider high-power, FRII radio galaxies and shock
heating of the intracluster medium (ICM, including the case of the
intergalactic medium prior to cluster formation) by their large-scale jets.
Based on the observed statistics of radio galaxies in clusters and their
evolution, along with the most reasonable assumptions, it is shown that they
can provide the ICM with excess specific energies of 1--2 keV per particle,
mainly during the redshift interval $z \sim 1-3$. This naturally meets the
requirements of cluster evolution models with non-gravitational feedback in
accounting for the observed deviations in the X-ray luminosity-temperature
relation. In contrast to supernovae, such large-scale jets deposit their energy
directly into the low density ICM outside galaxies, and are much less
susceptible to radiative losses. As a clear and potentially decisive test of
this scenario, we propose the observation of `prompt' high energy gamma-rays
emitted by shock-accelerated, non-thermal electrons during the epoch of ICM
heating by radio galaxies, which may be feasible with the {\it GLAST}
satellite. Implications for recent detections of excess hard X-rays from groups
are also discussed.


title: Production of Intermediate-Mass Black Holes in Globular Clusters

abstract:
  The discovery of numerous non-nuclear X-ray point sources with luminosities
L>10^39 erg/s in several starburst galaxies has stimulated speculation about
their nature and origin. The strong variability seen in several sources points
to massive black holes as the central engines. If the flux is isotropic, the
luminosities range up to roughly 10^41 erg/s, implying masses of M>10^3 Msun if
the luminosity is sub-Eddington. Here we explore a model for these sources. We
suggest that in some tens of percent of globular clusters a very massive black
hole, M>50 Msun, is formed. This black hole sinks in <10^6 yr to the center of
the cluster, where in the 10^10 yr lifetime of the cluster it accretes roughly
10^3 Msun, primarily in the form of lighter black holes. Unlike less massive
black holes in binaries, which are flung from clusters by recoil before they
can merge gravitationally, a >50 Msun black hole has enough inertia that it
remains bound to the cluster. We suggest that 10^3 Msun black holes may be
common in the centers of dense globular clusters, and may therefore exist in
some tens of percent of current globulars. If the cluster later merges with its
host galaxy, accretion from young star clusters in molecular clouds by the
black hole can generate luminosity consistent with that observed. We also
consider the detectability of massive black holes in globular clusters with
gravitational wave detectors such as LISA and LIGO, and speculate on future
observations that may test our predictions.


title:
Impact of reverberation in flared accretion discs on temporal
  characteristics of X-ray binaries

abstract:
  Observations suggest that accretion discs in many X-ray binaries are likely
flared. An outer edge of the disc intercepts radiation from the central X-ray
source. Part of that radiation is absorbed and reemitted in the optical/UV
spectral ranges. However, a large fraction of that radiation is reflected and
appears in the broad-band X-ray spectrum as a Compton reflection bump. This
radiation is delayed and variability is somewhat smeared compared with the
intrinsic X-ray radiation. We compute response functions for flat and flared
accretion discs and for isotropic and anisotropic X-ray sources. A simple
approximation for the response function which is valid in the broad range of
the disc shapes and inclinations, inner and outer radii, and the plasma bulk
velocity is proposed. We also study the impact of the X-ray reprocessing on
temporal characteristics of X-ray binaries such as the power spectral density,
auto- and cross-correlation functions, and time/phase lags. We propose a
reprocessing model which explains the secondary peaks in the phase lag Fourier
spectra observed in Cyg X-1 and other Galactic black hole sources. The position
of the peaks could be used to determine the size of the accretion disc.


title:
High Spectral and Spatial Resolution Observations of Shocked Molecular
  Hydrogen at the Galactic Center

abstract:
  The presence of OH (1720 MHz) masers, and the absence of counterparts at
1665/1667 MHz has proved to be a clear diagnostic of shocked molecular gas
associated with Galactic supernova remnants. This suggests that shocked
molecular gas should be associated with the OH (1720 MHz) masers that have been
detected in the circumnuclear disk (CND) and Sgr A East at the Galactic center.
In order to test this hypothesis, we observed the H$_2$ 1--0 S(1) and Br
$\gamma$ lines using NICMOS on the HST and UNSWIRF on the AAT, near the regions
where OH (1720 MHz) masers are detected in the CND and Sgr A East. We present
the distribution of H$_2$ in the North and South lobes of the CND and in Sgr A
East. H$_2$ emission accompanies almost all of the maser spots detected at the
Galactic center. In particular, we find a striking filamentary structure near
the Northwest of the CND and evidence that shocked molecular gas is associated
with the 70 \kms molecular cloud at the Galactic center. We argue that the
emission from the CND could arise in gas heated by the dissipation of the
random motion of clumps by collisions or the dissipation of turbulence in a
more homogeneous medium. In addition, highly red-shifted gas of up to 140 \kms\
close to the eastern edge of the Sgr A East shell is detected. These
observations combined with OH (1720 MHz) results suggest that the H$_2$ gas is
shocked and accelerated by the expansion of Sgr A East into the 50 and the 70
\kms cloud and into the lobes of the CND.


title: Wide-field tracking with zenth-pointing telescopes

abstract:
  Equipped with a suitable optical relay system, telescopes employing low-cost
fixed primary mirrors could point and track while delivering high-quality
images to a fixed location. Such an optical tracking system would enable
liquid-mirror telescopes to access a large area of sky and employ infrared
detectors and adaptive optics. Such telescopes could also form the elements of
an array in which light is combined either incoherently or interferometrically.
Tracking of an extended field requires correction of all aberrations including
distortion, field curvature and tilt. A specific design is developed that
allows a 10-metre liquid-mirror telescope to track objects for as long as 30
minutes and to point as far as 4 degrees from the zenith, delivering a
distortion-free diffraction-limited image to a stationary detector,
spectrograph, or interferometric beam combiner.


title: The Ly-edge paradox and the need for obscured QSOs

abstract:
  Based on the most recent QSO ultraviolet spectra, the covering factor of the
clouds of the Broad Line Region (BLR) is about 30%, or larger. This value would
imply that in at least 30% of the QSOs our line of sight crosses one, or more,
BLR clouds and, in the latter case, the UV spectrum should show a sharp Ly-edge
in absorption. This Ly-edge in absorption is never observed. This paradox is
solved if, as suggested by various authors, the BLR is flattened and the dusty
gas in the outer parts, on the same plane, prevents the observation along the
lines of sight passing through the BLR clouds. The objects observed edge-on
(with respect to the flattened BLR) would be classified as obscured QSOs or,
within the framework of the unified model, type 2 QSOs. The covering factor of
the BLR constrains the fraction of obscured QSOs to be QSO2/QSO1 > 0.5. This
lower limit is already high with respect to the number of candidate type 2 QSOs
claimed so far. We discuss this constraint in relation to recent AGN surveys.


title:
A BeppoSAX observation of Her X-1 during the first main-on after an
  anomalous low-state: evidence for rapid spin-down

abstract:
  Results of a BeppoSAX observation of Her X-1 in 2000 October during the first
main-on state after the longest recorded anomalous low-state are presented. The
0.1-30 keV spectrum, light curve and pulse profile are all consistent with
those measured during previous main on-states, indicating that Her X-1 has
resumed its regular 35 day cycle with similar on-state properties as before.
However, from a comparison of the measured pulse period with that obtained
close to the start of the anomalous low-state, it is evident that Her X-1
continued to spin-down strongly during the anomalous low-state such that the
pulse period has returned to a similar value as ~15 years ago. Additionally,
the occurrence time of the main-on states after the end of the anomalous
low-state indicate that a change in the length, or phasing, of the 35-day cycle
occurred during the anomalous low-state.


title:
A new constraint on cosmological variability of the proton-to-electron
  mass ratio

abstract:
  Exotic cosmologies predict variability of the fundamental physical constants
over the cosmic time. Using the VLT/UVES high resolution spectra of the quasar
Q0347-3819 and unblended electronic - vibrational - rotational lines of the H2
molecule identified at z = 3.025 we test possible changes in the proton - to -
electron mass ratio mu_0 = m_p/m_e over the period of 11 Gyr. We obtained a new
constraint on the time - averaged variation rate of mu_0 of |d mu /d t /mu_0| <
5 10^{-15} yr^{-1} (1 sigma c.l.). The estimated 1 sigma uncertainty interval
of the |Delta mu/mu_0| ratio of about 0.004% implies that since the time when
the H2 spectrum was formed at z = 3.025, mu_0 has not changed by more than a
few thousands of a percent.


title: XMM-Newton study of the ULIRG NGC 6240

abstract:
  A recently performed XMM-Newton observation of the ULIRG NGC 6240 clearly
indicates the presence of an AGN contribution to its X-ray spectrum. In the 5.0
- 7.0 keV energy range there is a clear signature of the fluorescent Fe K lines
at 6.4, 6.7 and 6.9 keV, respectively.
  The line strength of the 6.4 keV line cannot be produced by a thermal
component. The 0.3 - 10.0 keV spectral energy distribution is characterized by
the following components: (I) two hot thermal components (the starburst), (II)
one direct component (heavily absorbed; AGN is hidden), (III) one reflection
component (the AGN), (IV) three narrow Fe lines. The model parameters for the
broad-band spectral energy distribution are consistent with the results of
previously works.


title:
Temporal and spectral gamma-ray properties of Mkn421 above 250 GeV from
  CAT observations between 1996 and 2000

abstract:
  The gamma-ray emission above 250 GeV from the BL Lac object Markarian 421 was
observed by the CAT Cherenkov imaging telescope between December, 1996, and
June, 2000. In 1998, the source produced a series of small flares, making it
the second extragalactic source detected by CAT. The time-averaged differential
spectrum has been measured from 0.3 to 5 TeV, which is well fitted with a power
law with an index of -2.88+-0.12(stat)+-0.06(syst). In 2000, the source showed
an unprecedented activity, with variability time-scales as short as one hour,
as for instance observed during the night between 4 and 5 February. The 2000
time-averaged spectrum measured is compatible with that of 1998, but some
indication of a spectral curvature is found between 0.3 and 5 TeV. The
possibility of TeV spectral hardening during flares is also discussed, and the
results are compared to those obtained on the other TeV BL Lac, Markarian 501.


title:
Evolution of cosmological perturbations in non-singular string
  cosmologies

abstract:
  In a class of non-singular cosmologies derived from higher-order corrections
to the low-energy bosonic string action, we derive evolution equations for the
most general cosmological scalar, vector and tensor perturbations. In the large
scale limit, the evolutions of both scalar and tensor perturbations are
characterised by conserved quantities, the usual curvature perturbation in the
uniform-field gauge and the tensor-type perturbed metric. The vector
perturbation is not affected, being described by the conservation of the
angular momentum of the fluid component in the absence of any additional
dissipative process. For the scalar- and tensor-type perturbations, we show
how, given a background evolution during kinetic driven inflation of the
dilaton field, we can obtain the final power spectra generated from the vacuum
quantum fluctuations of the metric and the dilaton field during the inflation.


title:
Physical properties and small-scale structure of the Lyman-alpha forest:
  Inversion of the HE 1122-1628 UVES spectrum

abstract:
  We study the physical properties of the Lyman-alpha forest by applying the
inversion method described by Pichon et al. (2001) to the high resolution and
high S/N ratio spectrum of the z_em=2.40 quasar HE 1122-1628 obtained during
Science Verification of UVES at the VLT. We compare the column densities
obtained with the new fitting procedure with those derived using standard Voigt
profile methods. The agreement is good and gives confidence in the new
description of the Lyman-alpha forest as a continuous field as derived from our
method. We show that the observed number density of lines with logN>13 and 14
is, respectively, 50 and 250 per unit redshift at z~2. We study the physical
state of the gas, neglecting peculiar velocities, assuming a relation between
the overdensity and the temperature. T=Tbar * rho^(2beta). There is an
intrinsic degeneracy between the parameters beta and Tbar. We demonstrate that,
at a fixed beta, the temperature at mean density, Tbar, can be uniquely
extracted however. While applying the method to HE 1122-1628, we conclude that
for 0.2<beta<0.3, 6000<Tbar<15000 K at z~2. We investigate the small scale
structure of strong absorption lines using the information derived from the
Lyman-beta, Lyman-gamma and Civ profiles. Introducing the Lyman-beta line in
the fit allows us to reconstruct the density field up to rho~10 instead of 5
for the Lyman-alpha line only. There may be small velocity shifts ~10km.s^{-1}
between the peaks in the Civ and Hi density profiles. Although the statistics
is small, it seems that Civ/Hi and n_HI are anti-correlated. This could be a
consequence of the high sensitivity of the Civ/Hi ratio to temperature. The
presence of associated Ovi absorption, with similar profile, confirms that the
gas is photo-ionized and at a temperature of T~10^5 K.


title: Influence of the cosmological expansion on small systems

abstract:
  The effect of the large-scale cosmological expansion on small systems is
studied in the light of modern cosmological models of large-scale structure. We
identify certain assumptions of earlier works which render them unrealistic
regarding these cosmological models. The question is reanalyzed by dropping
these assumptions to conclude that a given small system can experience either
an expansion or a contraction of cosmological origin.


title: Towards One Tonne Direct WIMP Detectors: Have we got what it takes?

abstract:
  Experimentally have we got what it takes to pursue the direct observation of
WIMP interactions down to sensitivities of a few events /100 kg/year? For a Ge
target with a low energy threshold (<20 keVr) this corresponds to a
WIMP-nucleon sigma~10^-46 cm^2. A number of recent theoretical papers, making
calculations in SUSY-based frameworks, show many (>5) orders of magnitude
spread in the possible interaction rates for models consistent with existing
Cosmology and Accelerator bounds. Some theorists, but certainly not all, are
able to generate models, that lead to interaction rates at the few /kg/day that
would be implied by the current DAMA annual modulation signal. All theorists
demonstrate models that generate much lower interaction rates. This paper takes
an unashamed experimentalist`s view of the issues that arise when looking
forward to constructing 1 tonne WIMP detectors.


title: Distribution of baryonic and non-baryonic matter in clusters of galaxies

abstract:
  We present the analysis of baryonic and non-baryonic matter distributions in
a sample of eleven nearby clusters (0.03<z<0.09) with temperatures between 4.4
and 9.4 keV. These galaxy clusters have been studied in detail using X-ray data
and global physical properties have been determined. Correlations between these
quantities have been analysed and compared with the results for distant
clusters. We found an interesting dependence between the relative gas extent
(expressed as the ratio of gas mass fractions at different radii) and the total
cluster mass. The extent of the gas relative to the extent of the dark matter
tends to be larger in less massive clusters. This dependence might give us some
hints about non-gravitational processes in clusters.


title:
Time dependent photoionization opacities in dense Gamma-Ray Burst
  environments

abstract:
  The recent detection of a transient absorption feature in the X-ray prompt
emission of GRB 990705 showed the importance of such observations in the
understanding of gamma-ray bursts and their progenitors. We investigate the
time dependence of photoionization edges during the prompt emission of bursts
in different environments. We show that their variability can be used to infer
the density and geometry of the surrounding medium, giving important clues to
unveil the nature of the burst progenitor.


title: CHANDRA observation of the narrow-line Seyfert 1 galaxy IRAS 13224-3809

abstract:
  The narrow-line Seyfert 1 galaxy (NLS1) IRAS 13224-3809 has been observed
with the CHANDRA High Resolution Camera (HRC-I) for 12 ksec on February, 2,
2000. The source was proposed for CHANDRA observations to precisely determine
the X-ray centroid position and to investigate the timing properties of the
most X-ray variable Seyfert galaxy. The position derived from CHANDRA confirms
that the X-ray emission is associated with IRAS 13224-3809. The CHANDRA HRC-I
light curve shows indications for a possible presence of a quasi-periodic
oscillation. The strongest signal is found at 2500 sec. Accretion disk
instabilities may provide a plausible explanation for the quasi-periodic
oscillations.


title: Revealing the Warm-Hot Intergalactic Medium with OVI Absorption

abstract:
  Hydrodynamic simulations of growth of cosmic structure suggest that 30-50% of
the total baryons at z=0 may be in a warm-hot intergalactic medium (WHIM) with
temperatures ~10^5-10^7K. The O VI \lambda \lambda 1032, 1038 absorption line
doublet in the FUV portion of QSO spectra provides an important probe of this
gas. Utilizing recent hydrodynamic simulations, it is found that there should
be ~5 O VI absorption lines per unit redshift with equivalent widths >= 35 mA,
decreasing rapidly to ~0.5 per unit redshift at >= 350 mA. About 10% of the
total baryonic matter or 20-30% of the WHIM is expected to be in the O VI
absorption line systems with equivalent width >= 20 mA; the remaining WHIM gas
may be too hot or have too low metallicity to be detected in O VI. We find that
the simulation results agree well with observations with regard to the line
abundance and total mass contained in these systems. Some of the O VI systems
are collisionally ionized and some are photoionized, but most of the mass is in
the collisionally ionized systems. We show that the gas that produces the O VI
absorption lines does not reside in virialized regions such as galaxies,
groups, or clusters of galaxies, but rather has an overdensity of 10-40 times
the average density. These regions form a somewhat connected network of
filaments. The typical metallicity of these regions is 0.1-0.3Zsun.


title: Experimental Limit to Interstellar 244Pu Abundance

abstract:
  Short-lived nuclides, now extinct in the solar system, are expected to be
present in the interstellar medium (ISM). Grains of ISM origin were recently
discovered in the inner solar system and at Earth orbit and may accrete onto
Earth after ablation in the atmosphere. A favorable matrix for detection of
such extraterrestrial material is presented by deep open-sea sediments with
very low sedimentation rates (0.8-3 mm/kyr). We report here on the measurement
of Pu isotopic abundances in a 1-kg deep-sea dry sediment collected in 1992 in
the North Pacific. Our measured value of (3+-3)x10^5 244Pu atoms in the
Pu-separated fraction of the sample shows no excess over the expected
stratospheric nuclear fallout content and under reasonable assumptions we
derive a limit of 2x10^-11 g-244Pu/g-ISM for the abundance of 244Pu in ISM.


title: Variable UV Absorption in the Spectrum of MRC 2251-178

abstract:
  We present an ultraviolet spectrum of MRC 2251-178 taken with HST/STIS-G230L.
The observation is part of a snap shot program of QSOs to systematically search
for intrinsic absorption lines through variability. The sample consists of all
QSOs observed with HST/FOS which showed associated narrow absorption lines. The
FOS spectrum of MRC 2251-178, taken in 1996, showed an associated C IV doublet
with an C IV \lambda1548 equivalent width 1.09+/-0.09 A (Monier et al. 2001).
It is not detected in the STIS spectrum taken four years later, down to a
3-sigma threshold of 0.19 A. In addition to its other accolades, these
observations make MRC 2251-178 the very first QSO at low redshift in which the
associated absorption is shown to be truly intrinsic. We discuss the
implications of this and suggest courses for future study.


title: Looking for clues to the nature of HI deficiency in cluster spirals

abstract:
  We derive the atomic hydrogen content for 1900 spirals in the fields of
eighteen nearby clusters. By comparing the HI deficiency distributions of the
galaxies inside and outside one Abell radius ($\ra$) of the center of each
region, we find that two thirds of the clusters in our sample show a dearth of
neutral gas in their interiors. Possible connections between the gaseous
deficiency and the characteristics of both the underlying galaxies and their
environment are investigated in order to gain insight into the cause of HI
depletion. In the clusters in which neutral gas deficiency is pronounced, we
see clear indications that the amount of depletion is related to the morphology
of the galaxies: early-type and, probably, dwarf spirals are more easily
emptied of gas than the intermediate Sbc-Sc types. Gas contents below one
tenth, and even one hundredth, of the expected value have been measured,
implying that gas removal must be very efficient. Our 21-cm data also show that
in the HI-deficient clusters the proportion of gas-poor spirals decreases
continuously towards the outskirts of these systems, the zone of significant
deficiency reaching as far out as $2\ra$. In an independent analysis of the
Virgo cluster, we find suggestive indications that gas losses are driven by the
interaction of the disks with the inner hot intracluster gas around M87. We
also report evidence that gas-poor spirals follow more radial orbits than those
of the gas-rich objects. We conclude that ISM-IGM hydrodynamic effects appear
as the most plausible cause of HI removal.


title: Properties of QSO-Intrinsic Narrow Ultraviolet Absorption

abstract:
  I present the current state of knowledge about narrow (<500 km/s) ultraviolet
absorption that is intrinsic to QSOs. I consider interpretations in the context
of the accretion-disk/wind scenario of QSOs.


title: On the Formation of Degenerate Heavy Neutrino Stars

abstract:
  The dynamics of a self-gravitating cold Fermi gas is described using the
analogy with an interacting self-gravitating Bose condensate having the same
Thomas-Fermi limit. The dissipationless formation of a heavy neutrino star
through gravitational collapse and ejection of matter is demonstrated
numerically. Such neutrino stars offer an alternative to black holes for the
supermassive compact dark objects at the centers of galaxies.


title: Very high-energy gamma-ray sources as seen by the CAT imaging telescope

abstract:
  To date, only three objects have been firmly established as very high-energy
gamma-ray sources in the Northern sky: the Crab nebula, which is a plerion, and
the two blazars Markarian 501 and Markarian 421. This paper reviews the most
striking results obtained for these sources by the CAT atmospheric Cherenkov
imaging telescope.


title:
The determination of the age of Globular Clusters: a statistical
  approach

abstract:
  We present a statistical approach for determining the age of Globular
Clusters (GCs) that allows estimating the age derived from CMDs more accurately
than the conventional methods of the isochrone fitting. We measure how closely
a set of synthetic CMDs constructed from different evolutionary models resemble
the observed ones by determining the likelihood using Saha and Chi-square
statistics. The model which best matches the observational data, of a set of
plausible ones, is the one with the highest value of the estimator. We apply
this method to a set of three different evolutionary models presented by three
different authors. Each of theses sets consists again of many different models
of various chemical abundances, ages, input physics and there alike. We
subsequently derive the age of GCs NGC 6397, M92 and M3. With a confidence
level of 99%, we find that the best estimate of the age is 14.0 Gyrs within the
range of 13.8 to 14.4 Gyrs for NGC 6397, 14.75 Gyrs within the range of 14.50
to 15.40 Gyrs for M92, and 16.0 Gyrs within the range of 15.9 to 16.3 Gyrs for
M3.


title: Time Dependence in Plasma Codes

abstract:
  Time-dependent plasma codes are a natural extension of static nonequilibrium
plasma codes. Comparing relevant timescales will determine whether or not
time-dependent treatment is necessary. In this article I outline the
ingredients for a time-dependent plasma code in a homogeneous medium and
discuss the computational method. In the second half of the article I describe
recombination in the early Universe as a detailed example of a problem whose
solution requires a time-dependent plasma code.


title:
Sulfur, Chlorine, & Argon Abundances in Planetary Nebulae. I:
  Observations and Abundances in a Northern Sample

abstract:
  This paper is the first of a series specifically studying the abundances of
sulfur, chlorine, and argon in Type II planetary nebulae (PNe) in the Galactic
disk. Ratios of S/O, Cl/O, and Ar/O constitute important tests of differential
nucleosynthesis of these elements and serve as strict constraints on massive
star yield predictions. We present new ground-based optical spectra extending
from 3600-9600 Angstroms for a sample of 19 Type II northern PNe. This range
includes the strong near infrared lines of [S III] 9069,9532, which allows us
to test extensively their effectiveness as sulfur abundance indicators. We also
introduce a new, model-tested ionization correction factor for sulfur. For the
present sample, we find average values of S/O=1.2E-2(+/- 0.71E-2),
Cl/O=3.3E-4(+/- 1.6E-4), and Ar/O=5.0E-3(+/- 1.9E-3).


title: How Evolved are the Mass Donor Stars inCataclysmic Variables?

abstract:
  Recent spectroscopic observations have identified several cataclysmic
variables non-solar metal abundances. We present theoretical models which
examine the level of core evolution expected for CV secondaries prior to
contact. Our results indicate that few secondary stars evolve past 10% of their
main sequence lifetime prior to the initiation of mass transfer; a result which
is in agreement with present day observations. Thus, the non-solar metal
abundances observed must be due to nuclear burning by-products accreted by the
secondary star during common envelope sweeping prior to initial contact or
ejecta collected during classical nova outbursts.


title:
The Stellar Parameters and Evolutionary State of the Primary in the
  d'-Symbiotic System StH\alpha190

abstract:
  We report on a high-resolution, spectroscopic stellar parameter and abundance
analysis of a d' symbiotic star: the yellow component of StH\alpha190. This
star has recently been discovered, and confirmed here, to be a rapidly rotating
(vsini=100 km/s) subgiant, or giant, that exhibits radial-velocity variations
of probably at least 40 km/s, indicating the presence of a companion (a white
dwarf star). It is found that the cool stellar component has Teff=5300K and log
g=3.0. The iron and calcium abundances are close to solar, however, barium is
overabundant, relative to Fe and Ca, by about +0.5 dex. The barium enhancement
reflects mass-transfer of s-process enriched material when the current white
dwarf was an asymptotic giant branch (AGB) star. The past and future evolution
of this binary system depends critically on its current orbital period, which
is not yet known. Concerted and frequent radial-velocity measurements are
needed to provide crucial physical constraints to this d' symbiotic system.


title:
The Reanalysis of the ROSAT Data of GQ Mus (1983) Using White Dwarf
  Atmosphere Emission Models

abstract:
  The analyses of X-ray emission from classical novae during the outburst stage
have shown that the soft X-ray emission below 1 keV, which is thought to
originate from the photosphere of the white dwarf, is inconsistent with the
simple blackbody model of emission. Thus, $ROSAT$ Position Sensitive
Proportional Counter (PSPC) archival data of the classical novae GQ Mus 1983
(GQ Mus) have been reanalyzed in order to understand the spectral development
in the X-ray wavelengths during the outburst stage. The X-ray spectra are
fitted with the hot white dwarf atmosphere emission models developed for the
remnants of classical novae near the Eddington luminosity. The post-outburst
X-ray spectra of the remnant white dwarf is examined in the context of
evolution on the Hertzsprung-Russell diagram using C-O enhanced atmosphere
models. The data obtained in 1991 August (during the ROSAT All Sky Survey)
indicate that the effective temperature is kT_e<54 eV (<6.2x10^5 K). The 1992
February data show that the white dwarf had reached an effective temperature in
the range 38.3-43.3 eV (4.4-5.1x10^5 K) with an unabsorbed X-ray flux (i.e.,
$\sim$ bolometric flux) between 2.5x10^-9 and 2.3x10^-10 erg s^-1 cm^-2. We
show that the H burning at the surface of the WD had most likely ceased at the
time of the X-ray observations. Only the 1991 August data show evidence for
ongoing H burning.


title:
Observation of Excess Flux for Negative Cosmic Ray Penetrating Particles
  in Bubble Chamber "SKAT" for Momentum Range (30GeV/c<P<150GeV/c)

abstract:
  There are presented the first results of the new heavy stable cosmic ray
particles search in the bubble chamber "SKAT", exposed in the neutrino beam of
Serpukhov Accelerator during 1976-1992. For momentum range (30-150GeV/c) it was
observed negative particles excess flux after looking over 3,000 such stills.


title:
Erzion Interpretation of Negative Penetrating Cosmic Ray Particles
  Excess Flux Observed in Bubble Chamber "SKAT"

abstract:
  It is discussed the interpretation of negative penetrating cosmic ray
particles excess flux observed in bubble chamber "SKAT" for momentum range
(30-150GeV/c) by Erzions, hypothetical heavy stable penetrating hadrons,
proposed to explain the anomalous vertical muons energy spectrum at small depth
underground. It is shown that negative charge of particles, observed in "SKAT"
is the same as predicted by theoretical Erzion model.


title:
Supermassive Black Hole Accretion History Inferred from a Large Sample
  of Chandra Hard X-ray Sources

abstract:
  We describe the optical, near-infrared, and radio properties of a sample of
hard (2-7 keV) X-ray sources detected in a deep Chandra observation of the
field surrounding the Abell 370 cluster. We combine these data with similar
observations of the Chandra Deep Field-North and the Hawaii Survey Field SSA13
to obtain a sample of 69 hard X-ray sources (45 are spectroscopically
identified) with extremely deep 20 cm observations. We find that about 4% of
the >Lstar galaxy population is X-ray luminous at any time and hence that black
hole accretion has a duration of about half a Gyr. We find that about 30% of
the summed 2-7 keV flux from our total sample is from sources at z<1. We
estimate the bolometric luminosities of accretion onto supermassive black holes
and the mass inflow rates. The time history of the accretion rate density is
evaluated, and its integrated value is reasonably consistent with the value
inferred from the local black hole mass to bulge mass ratio.


title:
Fourier Analysis of Gamma-Ray Burst Light Curves: Searching for Direct
  Signature of Cosmological Time Dilation

abstract:
  We study the power density spectrum (PDS) of light curves of the observed
gamma-ray bursts (GRBs) to search for a direct signature for cosmological time
dilation in the PDS statistics with the GRBs whose redshifts $z$'s are known.
The anticorrelation of a timescale measure and a brightness measure is indirect
evidence of its effect. On the other hand, we directly demonstrate that a time
dilation effect can be seen in GRB light curves. We find that timescales tend
to be shorter in bursts with small redshift, as expected from cosmological
time-dilation effects, and we also find that there may be non-cosmological
effects constituting to this correlation. We discuss its implication on
interpretations of the PDS analysis results. We put forward another caution to
this kind of analysis when we statistically exercise with GRBs whose $z$ is
unknown.


title:
A grid of Composite Models for the Simulation of Starburst Galaxy and
  HII Region Spectra

abstract:
  A grid of models for starburst spectra is presented and compared with
power-law models which represent AGNs. The models are composite, i.e., they
account for the radiation from the starburst and for the shocks created by
super-winds. Some interesting fit of models to observations are also discussed.
In particular, it is found that [OIII]/Hb ~can reach values as high as for the
AGN when the emitting clouds are close to the starburst region. Moreover CIV
lines can be high even if SiIV lines are relatively low. It is found that for
some line ratios, which have similar values for starburst and AGN models, the
width of the lines can distinguish between the two types.


title:
Search for nearby stars among proper motion stars selected by
  optical-to-infrared photometry. I. Discovery of LHS 2090 at spectroscopic
  distance of d=6pc

abstract:
  We present the discovery of a previously unknown very nearby star - LHS 2090
at a distance of only d=6 pc. In order to find nearby (i.e. d < 25 pc) red
dwarfs, we re-identified high proper motion stars ($\mu >$ 0.18 arcsec/yr) from
the NLTT catalogue (Luyten \cite{luyten7980}) in optical Digitized Sky Survey
data for two different epochs and in the 2MASS data base. Only proper motion
stars with large $R-K_s$ colour index and with relatively bright infrared
magnitudes ($K_s<10$) were selected for follow-up spectroscopy. The
low-resolution spectrum of LHS 2090 and its large proper motion (0.79
arcsec/yr) classify this star as an M6.5 dwarf. The resulting spectroscopic
distance estimate from comparing the infrared $JHK_s$ magnitudes of LHS 2090
with absolute magnitudes of M6.5 dwarfs is $6.0\pm1.1$ pc assuming an
uncertainty in absolute magnitude of $\pm$0.4 mag.


title: Long periodicity of Blasers with RXTE ASM

abstract:
  We have searched for long periodicity in ten X-ray selected Blasers with RXTE
ASM 4.6 years data. We found about 10-100 day possible periodicities for three
TeV gamma ray Blasers, Mkn 421, Mkn 501 and PKS 2155-304.


title: On the formation of oxygen-neon white dwarfs in close binary systems

abstract:
  The evolution of a star of initial mass 10 $M_{\odot}$, and metallicity $Z =
0.02$ in a Close Binary System (CBS) is followed from its main sequence until
an ONe degenerate remnant forms. Restrictions have been made on the
characteristics of the companion as well as on the initial orbital parameters
in order to avoid the occurrence of reversal mass transfer before carbon is
ignited in the core. The system undergoes three mass loss episodes. The first
and second ones are a consequence of a case B Roche lobe overflow. During the
third mass loss episode stellar winds may play a role comparable to, or even
more important than Roche lobe overflow. In this paper, we extend the
previously existing calculations of stars of intermediate mass belonging to
close binary systems by following carefully the carbon burning phase of the
primary component. We also propose different possible outcomes for our scenario
and discuss the relevance of our findings. In particular, our main result is
that the resulting white dwarf component of mass $1.1 M_\odot$ more likely has
a core composed of oxygen and neon, surrounded by a mantle of carbon-oxygen
rich material. The average abundances of the oxygen-neon rich core are $X({\rm
O}^{16})=0.55$, $X({\rm Ne}^{20})=0.28$, $X({\rm Na}^{23})=0.06$ and $X({\rm
Mg}^{24})=0.05$. This result has important consequences for the Accretion
Induced Collapse scenario. The average abundances of the carbon-oxygen rich
mantle are $X({\rm O}^{16})=0.55$, and $X({\rm C}^{12})=0.43$. The existence of
this mantle could also play a significant role in our understanding of
cataclysmic variables.


title:
The detection of molecular gas in the central galaxies of cooling-flow
  clusters

abstract:
  We present the detections of CO line emission in the central galaxy of
sixteen extreme cooling flow clusters using the IRAM 30m and the JCMT 15m.
These detections of CO(1-0), CO(2-1), CO(3-2) and CO(4-3) are consistent with
the presence of a substantial mass of warm molecular gas (10^9-11.5Mo) within
50kpc radius of the central galaxy. We present limits on thirteen other
galaxies in similarly extreme cooling flow clusters. These results are
consistent with the presence of a massive starburst in the central galaxy which
warms a population of cold gas clouds producing both optical and NIR emission
lines and significant CO line emission. Curiously, our CO detections are
restricted to the lower radio power central galaxies. These are the first
detections of molecular gas in a cooling flow other than NGC1275 in the Perseus
cluster. As four of our targets have firm limits on their dust mass from SCUBA
and the rest have crude limits from IRAS, we can calculate gas-to-dust ratios.
Simple analysis indicates that the best secondary indicatorof molecular gas is
optical line luminosity. We review the implications of these results and the
prospects for observations in the near future.


title:
Strange Star Heating Events as a Model for Giant Flares of Soft
  Gamma-ray Repeaters

abstract:
  Two giant flares were observed on 5 March 1979 and 27 August 1998 from the
soft gamma-ray repeaters SGR 0526-66 and SGR 1900+14, respectively. The
striking similarity between these remarkable bursts strongly implies a common
nature. We show that the light curves of the giant bursts may be easily
explained in the model where the burst radiation is produced by the bare quark
surface of a strange star heated, for example, by impact of a massive
comet-like object.


title:
Second-Parameter Globular Clusters in the Milky Way and in M33 as
  Tracers of Mass Loss from M31 in the Early Epoch?

abstract:
  I suggest that the bulk of the "young", second-parameter globular clusters
(SPGCs) observed in the outer halo of our Galaxy and recently found in other
massive spiral of the Local Group (LG), M33, may have originated due to mass
outflow from M31 and subsequent accretion of gas on the Galaxy and M33 in the
early epoch.


title: Comment on "Self-interacting Warm Dark Matter"

abstract:
  Hannestad and Scherrer analysed self-interacting Warm and Hot Dark Matter and
found power spectra in disagreement with previous papers. We argue that they
include self-interactions in a weak-coupling approximation, as for photons
after recombination. The ``tightly coupled'' approximation used for
pre-recombination photons, and previous discussions of self-interacting HMD,
would have been more appropriate. Their approximation generates a Boltzmann
hierarchy leading to a stiff system of equations. Furthermore contamination by
gauge modes could invalidate their results.


title:
Coalescing neutron stars - a step towards physical models III. Improved
  numerics and different neutron star masses and spins

abstract:
  (Abridged) In this paper we present a compilation of results from our most
advanced neutron star merger simulations, including a description of the
employed numerical procedures and a more complete overview over a large number
of computed models. The three-dimensional hydrodynamic simulations were done
with a code based on the Piecewise Parabolic Method with up to five levels of
nested Cartesian grids. The simulations are basically Newtonian, but
gravitational-wave emission and the corresponding back-reaction are taken into
account. The use of a physical nuclear equation of state allows us to follow
the thermodynamic history of the stellar medium and to compute the energy and
lepton number loss due to the emission of neutrinos. The computed models differ
concerning the neutron star masses and mass ratios, the neutron star spins, the
numerical resolution expressed by the cell size of the finest grid and the
number of grid levels, and the calculation of the temperature from the solution
of the entropy equation instead of the energy equation. Our simulations show
that the details of the gravitational-wave emission are still sensitive to the
numerical resolution, even in our highest-quality calculations. The amount of
mass which can be ejected from neutron star mergers depends strongly on the
angular momentum of the system. Our results do not support the initial
conditions of temperature and proton-to-nucleon ratio assumed in recent work
for producing a solar r-process pattern for nuclei around and above the A
approx 130 peak. The improved models confirm our previous conclusion that
gamma-ray bursts are not powered by neutrino emission during the dynamical
phase of the merging of two neutron stars.


title:
The velocity field of collapsing spherical structures. Limitations of
  the spherical infall model in mass estimation

abstract:
  We assume that the amplitude of the caustics in redshift space is a sum of
two components: the first one can be predicted by the spherical infall model
with no random motion, and the second is due to the random motion distribution.
Smooth model curves are used to estimate the maximum values of the first
component for the Coma cluster. Then, an approximation of the radial component
of the infall velocity --based on the above curves-- is derived and a mass
profile of the cluster is calculated. This mass profile, that is an upper limit
for the spherical infall model, combined with estimations given by other
authors provides an approximation of a lower limit for the mass of the system.


title: Photometric Constraints on Microlens Spectroscopy of EROS-BLG-2000-5

abstract:
  We apply EROS photometric data to interpret previously published Keck and VLT
spectra of the binary-microlens caustic-crossing event EROS-BLG-2000-5. We show
that the VLT data imply that the outer 4 % of the limb of the K3-giant source
is strongly in emission in Halpha, in contradiction to available models of the
photosphere. This conflict could be resolved if the integrated Halpha emission
from the chromosphere were equal to 8 % of the integrated Halpha absorption
from the source as a whole. These conclusions regarding the extreme limb are
almost completely model-independent. We also present a general method for using
the photometric data to facilitate direct comparison between the atmospheric
model and the spectroscopic data. While this method has some model-dependent
features, it is fairly robust and can serve to guide the analysis of spectra
while more detailed models of the lens geometry are being developed. In
addition, we find that the color of the limb of the source (outer 5.5 % by
radius) is Delta(V-I) = 0.37 redder than the source as a whole, so that it has
the color of a M0 giant.


title:
The X-ray properties of the low-redshift quasar MRC 2251-178 and its
  environment: some surprises

abstract:
  MR 2251-178 was the first quasar initially discovered in X-rays, and the
first one found to host a warm absorber. Despite its many outstanding
multi-wavelength properties, MR 2251-178 has not yet been studied in detail
with recent X-ray observatories. Here, we present results from an analysis of
the X-ray spectral, temporal, and spatial properties of this source and its
environment based on deep observations carried out with the X-ray satellite
{\sl ROSAT}. The derived mean soft X-ray luminosity of MR 2251-178, ~10^{45}
erg/s, places the quasar among the most X-ray luminous AGN in the local
universe.
  The complete results of this study appeared in A&A 367, 801 (see
http://www.xray.mpe.mpg.de/~skomossa/).


title:
Nuclear gas dynamics in Arp 220 - sub-kiloparsec scale atomic hydrogen
  disks

abstract:
  We present new, high angular resolution (~0.22") MERLIN observations of
neutral hydrogen (HI) absorption and 21-cm radio continuum emission across the
central ~900 parsecs of the ultraluminous infrared galaxy, Arp220. Spatially
resolved HI absorption is detected against the morphologically complex and
extended 21-cm radio continuum emission, consistent with two counterrotating
disks of neutral hydrogen, with a small bridge of gas connecting the two.
  We propose a merger model in which the two nuclei represent the galaxy cores
which have survived the initial encounter and are now in the final stages of
merging, similar to conclusions drawn from previous CO studies (Sakamoto,
Scoville & Yun 1999). However, we suggest that instead of being coplanar with
the main CO disk (in which the eastern nucleus is embedded), the western
nucleus lies above it and, as suggested by bridge of HI connecting the two
nuclei, will soon complete its final merger with the main disk. We suggest that
the collection of radio supernovae (RSN) detected in VLBA studies in the more
compact western nucleus represent the second burst of star formation associated
with this final merger stage and that free-free absorption due to ionised gas
in the bulge-like component can account for the observed RSN distribution.
(Abridged)


title:
Broad emission lines from opaque electron-scattering environment of SN
  1998S

abstract:
  I propose that broad narrow-topped emission lines with full width at zero
intensity >20000 km/s, seen in early-time spectra of SN 1998S, originate from a
dense circumstellar gas and not from the supernova ejecta. The tremendous line
width is the result of multiple scattering of the narrow line radiation on
thermal electrons of the circumstellar shell with the Thomson optical depth of
about 4 on 1998 March 6.


title: New spectroscopic observations of the B[e]/K binary system MWC 623

abstract:
  The B[e]/K binary system MWC 623 was reinvestigated using new spectroscopic
observations. The absorption lines of the K and the B star do not exhibit any
significant radial velocity variations over a time interval of 14 years. The
spectral classification using a recent echelle spectrum yielded spectral types
of K2II-Ib and B4III. The luminosity class of the K star gives an estimate of
the distance towards MWC 623 of 2.4(+1.4/-0.9) kpc. This is consistent with the
kinematic distance of 2.0(+0.6/-0.3) kpc. The masses derived from the locations
of the binary components in the H-R diagram are 7+-1.5 Msun and 7.5+-2.5 Msun
for the B and K star, respectively, i.e. the mass ratio is close to 1. Both
stars are coeval with an age of 50+10/-20 Myr as shown by the comparison with
isochrones. The high luminosity of the K star excludes a pre-main sequence
evolutionary phase as explanation for the strong LiI lambda 6708 absorption
line observed in the late-type component. Rather, the high lithium abundance is
a consequence of the young age. Likewise, the B[e] star is a slightly evolved
object starting it post-main sequence evolution.


title:
Large-Scale Structure from Spatial Condensation and Reproducing Dark
  Mass

abstract:
  Accounting for large-scale structure in our universe will require not only
reasonably accurate mathematical models of its cosmogony, topology and
cosmology, but also a more deeper understanding of our fundamental physical
concepts of space, time and energy. The foundations for a new "Spatial
Condensation (SC-)" cosmological model for our closed 3-D universe has already
been presented and this paper will explore the new and different predictions
for the evolution of its large-scale structure. Accounting begins with a
spatial condensation solution of the "cosmological constant" problem for the
infamous 10^120 factor for vacuum energy. The newly derived "expansion forces"
demark that distance where gravity gives way to the Hubble flow and decelerates
peculiar velocities towards "rest" in the comoving reference frame. The
postulated new dark mass, that scales differently than matter with the
expansion, provides the seeds for the condensation of matter and the formation
of black holes even before the decoupling of matter and radiation. Graphics of
the predicted size of large-scale structures are presented versus astronomical
measurements.


title: Non-pulsing emission from X-ray pulsars

abstract:
  Results of GRANAT/ART-P observations of three X-ray pulsars in non-pulsing
states are presented: 1) a statistically significant non-pulsing flux with a
simple power-law spectrum was detected during the ``off''- state of Her X-1; 2)
a significant (13 $\sigma$) non-pulsing flux with a strong iron emission line
at energies ~ 6.7-6.9 keV was detected during the eclipse ingress of Cen X-3;
3) a weak non-pulsing flux was detected during the X-ray eclipse of Vela X-1,
which probably resulted from scattering of the pulsar emission in the stellar
wind of an optical star.


title: Observation of solar flares through the ART-P telescope side shield

abstract:
  Some preliminary results of observations of six solar flares though the ART-P
telescop side shield in 1990-1992 are presented.


title:
Horizontal and Upward Tau Airshowers in Valleys from Mountains and
  Space: Discovering UHE Neutrinos and New Physics

abstract:
  Upward and horizontal tau Air-showers emerging from the Earth crust or
mountain chains are the most powerful signals of Ultra High Energy UHE
neutrinos nu_{tau}, bar\nu_{tau} and bar{nu}_e at PeVs and higher energy. The
multiplicity in tau Air-showers secondary particles,
N_{opt}=10^{12}(E_{tau}/PeV), N_{gamma}= 10^8*E_{tau}/PeV, N_{e^- e^+}= 2*10^7
E_{tau}/PeV, N_{mu}= 3 *10^5 (E_{tau}/PeV)^{0.85} make easy their discover. UHE
nu_tau,bar\nu_tau, following Super Kamiokande evidence of neutrino flavor
mixing, nu_mu<-->nu_tau, should be as abundant as nu_mu, bar\nu_mu.
  Also anti-neutrino electrons, bar\nu_e, near the Glashow W resonance energy
peak, E_{bar\nu_e} = M^2_W / 2m_e = 6.3*10^{15} eV may generate tau
Air-showers.
  Upward UHE nu_tau- N interaction on Earth crust at horizontal edge and from
below, their consequent upward UHE tau air-showers beaming toward high
mountains, air-planes, ballons and satellites should flash gamma, mu, X and
Cherenkov lights toward detectors.
  Such upward tau air-shower may already hit nearby satellite GRO gamma
detectors flashing them by short, hard, diluted gamma-burst at the edge of
BATSE threshold.
  The tau air-shower may test the UHE neutrino interactions leading to
additional fine-tuned test of New TeV Physics both in Mountain Valleys and in
Upward showers.


title:
The stellar content of the Hamburg/ESO survey. II. A large,
  homogeneously-selected sample of high latitude carbon stars

abstract:
  We present a sample of 403 faint high latitude carbon (FHLC) stars selected
from the digitized objective prism plates of the Hamburg/ESO Survey (HES).
Because of the ~15 Angstroem spectral resolution and high signal-to-noise ratio
of the HES prism spectra, our automated procedure based on the detection of C_2
and CN molecular bands permits high-confidence identification of carbon stars
without the need for follow-up spectroscopy. From a set of 329 plates (87% of
the survey), covering 6400 square degrees to a magnitude limit of V~16.5, we
analyze the selection efficiency and effective surface area of the HES FHLC
survey to date. The surface density of FHLC stars that we detect (0.072 +/-
0.005 square degrees) is 2-4 times higher than that of previous objective prism
and CCD surveys at high galactic latitude, even though those surveys claimed a
limiting magnitude up to 1.5 magnitudes fainter. This attests to the highest
selection sensitivity yet achieved for these types of stars.


title: Leptons with E>200 MeV trapped in the Earth's radiation belts

abstract:
  For the first time accurate measurements of electron and positron fluxes in
the energy range 0.2-10 GeV have been performed with the Alpha Magnetic
Spectometer (AMS) instrument at altitudes of 370-390 Km in the geographic
latitude interval +/- 51.7 deg. We present an original analysis of the AMS
data, focused on the study of the under-cutoff component of these fluxes,
outside the region of the South Atlantic Anomaly (SAA). A separation in
quasi-trapped, long lifetime (O(10 s)), and albedo, short life time (O(100
ms)), components is found. The flux maps as a function of the canonical
adiabatic variables L, alpha0 are determined in the interval
(L,alpha0)=(0.95-3,0-90) for electrons with E less than 10 GeV, and positrons
with E less than 3 GeV. The results are compared with existing data at lower
energies and in similar L, alpha0 range. The properties of the observed
under-cutoff particles are also investigated in terms of their residence times
and geographical origin. The resulting distributions are discussed and related
to the characteristics of the drift shells observed by AMS.


title:
Supersolar metal abundances and the Broad Line Region of Narrow-line
  Seyfert 1 galaxies

abstract:
  Narrow-line Seyfert 1 galaxies (NLSy1) are intriguing due to their extreme
continuum and emission line properties which are not yet well understood. This
paper is motivated by the recent suggestion that NLSy1 galaxies might be young
active galactic nuclei (AGNs) and that they may have supersolar metal
abundances. We have examined the stability of broad emission line region (BLR)
clouds under isobaric perturbation and its dependence on gas metal abundances.
We show that supersolar metallicity increases the range where multiple phases
in pressure balance may exist. This is particularly important for NLSy1s with
steep X-ray spectra where it delays the trend of hindrance of a multi-phase
equilibrium. Finally, the role of warm absorbers in the context of this
scenario is assessed.