title:
XTE J1118+480: Clues on the Nature of the Accretion Flow from the
  Optical Variability

abstract:
  We show how the simultaneous presence of a strong quasi periodic oscillation
(QPO) of period of about 10 seconds in the optical and X-ray lightcurves of the
X-ray transient XTE J1118+480 can be used to obtain information about the
nature of the accretion flow around the source. The unusually high
optical-to-X-ray flux ratio and the QPO observed simultaneously in both energy
bands suggest that a significant fraction of the optical flux might originate
close to the central source, where most of the X-rays are produced and be
indicative of a magnetically dominated corona. We also show how the temporal
evolution of the QPO can provide us with information on both the inner radius
and the viscous properties of the optically thick accretion disc.


title: The Turbulent Shock Origin of Proto--Stellar Cores

abstract:
  The fragmentation of molecular clouds (MC) into protostellar cores is a
central aspect of the process of star formation. Because of the turbulent
nature of super-sonic motions in MCs, it has been suggested that dense
structures such as filaments and clumps are formed by shocks in a turbulent
flow. In this work we present strong evidence in favor of the turbulent origin
of the fragmentation of MCs. The most generic result of turbulent fragmentation
is that dense post shock gas traces a gas component with a smaller velocity
dispersion than lower density gas, since shocks correspond to regions of
converging flows, where the kinetic energy of the turbulent motion is
dissipated. Using synthetic maps of spectra of molecular transitions, computed
from the results of numerical simulations of super--sonic turbulence, we show
that the dependence of velocity dispersion on gas density generates an
observable relation between the rms velocity centroid and the integrated
intensity (column density), Sigma(V_0)-I, which is indeed found in the
observational data. The comparison between the theoretical model (maps of
synthetic 13CO spectra), with 13CO maps from the Perseus, Rosette and Taurus MC
complexes, shows excellent agreement in the Sigma(V_0)-I relation. The
Sigma(V_0)-I relation of different observational maps with the same total rms
velocity are remarkably similar, which is a strong indication of their origin
from a very general property of the fluid equations, such as the turbulent
fragmentation process.


title:
Reviving Fossil Radio Plasma in Clusters of Galaxies by Adiabatic
  Compression in Environmental Shock Waves

abstract:
  We give for a plasma with a history of several expansion and contraction
phases an analytical model of the evolution of a contained relativistic
electron population under synchrotron, inverse Compton and adiabatic energy
losses or gains. This is applied to different scenarios for evolution of radio
plasma inside the cocoons of radio galaxies, after the activity of the central
engine has ceased. It is demonstrated that fossil radio plasma with an age of
even up to 2 Gyr can be revived by compression in a shock wave of large-scale
structure formation, caused during the merging events of galaxy clusters, or by
the accretion onto galaxy clusters. We argue, that this is a highly plausible
explanation for the observed cluster radio relics, which are the regions of
diffuse radio emission found in clusters of galaxies, without any likely parent
radio galaxy seen nearby. An implication of this model is the existence of a
population of diffuse, ultra-steep spectrum, very low frequency radio sources
located inside and possibly outside of clusters of galaxies, tracing the
revival of aged fossil radio plasma by the shock waves associated with
large-scale structure formation.


title:
Radiation-driven winds of hot stars. XIII. A description of NLTE line
  blocking and blanketing towards realistic models of expanding atmospheres

abstract:
  We present significant improvements of our approach in constructing detailed
atmospheric models and synthetic spectra for hot luminous stars:
  1. A sophisticated and consistent description of line blocking and
blanketing. Our solution concept renders the line blocking influence on the
ionizing fluxes (mainly the EUV and UV are affected) in identical quality as
the synthetic high resolution spectra representing the observable region. Line
blanketing is properly accounted for in the energy balance.
  2. A considerably improved and enhanced atomic data archive providing the
basis for a detailed multilevel NLTE treatment of the metal ions (from C to Zn)
and an adequate representation of line blocking and the radiative line
acceleration.
  3. A revised inclusion of EUV and X-ray radiation produced by cooling zones
originating from shock heated matter.
  This new tool not only provides an easy to use method for O-star diagnostics,
whereby physical constraints on the properties of stellar winds, stellar
parameters, and abundances can be obtained via a comparison of observed and
synthetic spectra, but also allows the astrophysically important information
about the ionizing fluxes of hot stars to be determined automatically. Results
illustrating this are discussed by means of a basic model grid calculated for
O-stars with solar metallicity. To further demonstrate the astrophysical
potential of our new method we provide a first detailed spectral diagnostic
determination of the stellar parameters, the wind parameters, and the
abundances by an exemplary application to the O9.5Ia supergiant alpha Cam.


title:
WIYN Open Cluster Study 5. Lithium Depletion and Metallicity in G and K
  Dwarfs of the Open Cluster M35

abstract:
  We present an analysis of high quality spectra of members of the young
cluster M35. By using a multi-fiber spectrograph, we are able to collect high
signal-to-noise, high resolution spectra of a sample of photometric candidate
members. Accurate radial velocities are used to establish the membership status
and rotational velocities are measured using cross-correlation. We also derive
the metal content of the cluster, [Fe/H]= -0.21$\pm$0.10, based on spectral
synthesis. Finally, we derive the lithium abundances of the bona fide cluster
members and compare the results with members of other clusters. For example,
M35 shows a smaller range in both rotation rates and lithium abundances as
compared to the Pleiades. We discuss possible roles of various parameters. Our
high quality M35 database of lithium abundances and rotational velocities are
perfectly suited to be used as a laboratory to test theoretical models dealing
with the lithium depletion phenomenon.


title: Star Formation History in the Solar Vicinity

abstract:
  The star formation history in the solar neighbourhood is inferred comparing a
sample of field stars from the Hipparcos Catalog with synthetic CMDs. We
considered separately the main sequence and the red giant region of the HR
diagram. The criteria for our best solutions are based on the $\chi^{2}$
minimization of star distributions in selected zones of the HR diagram. Our
analysis suggests that: a) the solutions are compatible with a Salpeter IMF and
with {\sl a star formation rate increasing, in a broad sense, from the
beginning to the present time}; b) the deduced volume mass densities and the
corresponding absolute scale of the SFR solutions are strongly influenced by
the initial mass function slope of low mass stars (below 0.5 Mo); c) the
stellar evolutionary models are not completely adequate: in fact {\sl the
theoretical ratio between the He-burning and MS star numbers is always a factor
1.5 greater than the observational value}. This fact could indicate the need of
a more efficient overshoot in the evolutionary models, or a different mixing
theory.


title:
Confronting Hydrodynamic Simulations Of Relativistic Jets With Data:
  What Do We Learn About Particles & Fields?

abstract:
  We review recent relativistic hydrodynamic simulations of jets, and their
interpretation in terms of the results from linear stability analysis. These
studies show that, interpreted naively, the distribution of synchrotron
intensity will in general be a poor guide to the physical state (density and
pressure) of the underlying flow, and that even if the physical state can be
inferred, it, in turn, may prove to be a poor guide to the source dynamics, in
terms of the transport of energy and momentum from the central engine. However,
we demonstrate that an interplay of simulation and linear stability analysis
provides a powerful tool for elucidating the nature and character of structures
that jets may sustain. From such studies we can explain the complex behavior of
observed jets, which manifest both stationary and propagating structures,
without recourse to ad hoc macroscopic disturbances. This provides a framework
for the interpretation of multi-epoch total intensity data wherein an
understanding of the character of individual flow features will allow the
effects of physical state and dynamics to be deconvolved.


title: Results from Microlensing Searches for Extrasolar Planets

abstract:
  Specially-designed microlensing searches, some of which have been underway
for several years, are sensitive to extrasolar planets orbiting the most common
stars in our Galaxy. Microlensing is particularly well-suited to the detection
of Jupiter-mass planets orbiting their parent stars at several AU. Since Jovian
analogs are thought to influence the subsequent evolution of most planetary
systems, they are particularly important to study. The orbital radii and
distances to the planetary systems probed by microlensing are larger than those
currently studied by radial velocity techniques; the two methods are thus
complementary. Recent results from microlensing searches are discussed,
including constraints on Jovian analogs orbiting typical Galactic stars.
Benefits and drawbacks of the technique for the characterization of planetary
systems, and future prospects are briefly reviewed.


title:
Extracting cosmological information from galaxy spectra and observations
  of high-redshift objects

abstract:
  I review the statistical techniques needed to extract information about
physical parameters of galaxies from their observed spectra. This is important
given the sheer size of the next generation of large galaxy redshift surveys.
Going to the opposite extreme I review what we can learn about the nature of
the primordial density field from observations of high--redshift objects.


title: Helioseismology and screening of nuclear reactions in the Sun

abstract:
  We show that models for screening of nuclear reactions in the Sun can be
tested by means of helioseismology. As well known, solar models using the weak
screening factors are in agreement with data. We find that the solar model
calculated with the anti screening factors of Tsytovitch is not consistent with
helioseismology, both for the sound speed profile and for the depth of the
convective envelope. Moreover, the difference between the no-screening and weak
screening model is significant in comparison with helioseismic uncertainty. In
other words, the existence of screening can be proved by means of
helioseismology.


title: The Development of Gas/Star Offsets in Tidal Tails

abstract:
  We present models of interacting galaxies in order to study the development
of spatial offsets between the gaseous and stellar components in tidal tails.
Observationally, such offsets are observed to exist over large scales (e.g.,
NGC 3690; Hibbard et al. 2000), suggesting an interaction between the tidal gas
and some (unseen) hot ISM. Instead, our models show these offsets are a natural
consequence of the radially extended HI spatial distribution in disk galaxies,
coupled with internal dissipation in the gaseous component driven by the
interaction. This mechanism is most effective in systems involved in very
prograde interactions, and explains the observed gas/star offsets in
interacting galaxies without invoking interactions with a hot ISM, starburst
ionization, or dust obscuration within the tails.


title: Alkali Metals and the Color of Brown Dwarfs

abstract:
  I summarize some of the consequences for the optical and very-near-infrared
spectra of T dwarfs (in particular) and brown dwarfs (in general) of their
possible dominance by the neutral alkali metal lines. As a byproduct of this
study, I estimate the true optical color of ``brown'' dwarfs.


title:
Gamma-ray Burst Afterglow with Continuous Energy Injection: Signature of
  a Highly-Magnetized Millisecond Pulsar

abstract:
  We investigate the consequences of a continuously injecting central engine on
the gamma-ray burst afterglow emission, focusing more specifically on a
highly-magnetized millisecond pulsar engine. For initial pulsar parameters
within a certain region of the parameter space, the afterglow lightcurves are
predicted to show a distinctive achromatic bump feature, the onset and duration
of which range from minutes to months, depending on the pulsar and the fireball
parameters. The detection of or upper limits on such features would provide
constraints on the burst progenitor and on magnetar-like central engine models.
An achromatic bump such as that in GRB 000301C afterglow may be caused by a
millisecond pulsar with P0=3.4 millisecond and Bp=2.7e14 Gauss.


title:
Damped Lyman-alpha absorption from a nearby Low Surface Brightness
  galaxy

abstract:
  Ground-based & HST images of the nearby galaxy SBS 1543+593 (z=0.009) show it
to be a Low Surface Brightness (LSB) galaxy with a central surface brightness
of mu_B(0)=23.2 mag/arcsec-2 and scale length 0.9 h-1 kpc, values typical for
the local LSB galaxy population. The galaxy lies directly in front of the QSO
HS 1543+5921 (z=0.807); an HST STIS spectrum of the quasar reveals a damped
Lyman-alpha (DLA) line at the redshift of the interloper with an HI column
density of log N(HI) = 20.35, as well as several low-ionization metal lines
with strengths similar to those found in the Milky Way interstellar medium. Our
data show that LSB galaxies are certainly able to produce the DLA lines seen at
higher redshift, and fuels the speculation that LSB galaxies are a major
contributor to that population of absorbers.


title:
Keck Diffraction-Limited Imaging of the Young Quadruple Star System HD
  98800

abstract:
  This paper presents diffraction-limited 1-18 micron images of the young
quadruple star system HD 98800 obtained with the W. M. Keck 10-m telescopes
using speckle and adaptive optics imaging at near-IR wavelengths and direct
imaging at mid-IR wavelengths. The two components of the visual binary, A and
B, both themselves spectroscopic binaries, were separable at all wavelengths,
allowing us to determine their stellar and circumstellar properties. Combining
these observations with spectroscopic data from the literature, we derive an
age of 10 Myr, masses of 0.93 and 0.64 M_sun and an inclination angle of 58 deg
for the spectroscopic components of HD 98800 B, and an age of 10 Myr and a mass
of 1.1 M_sun for HD 98800 Aa. Our data confirm that the large mid-IR excess is
entirely associated with HD 98800 B. This excess exhibits a black body
temperature of 150 K and a strong 10 micron silicate emission feature. The
theoretical equilibrium radius of large, perfectly absorbing, 150 K grains
around HD 98800 B is 2.4 AU, suggesting a circum-spectroscopic binary
distribution. Our observations set important upper limits on the size of the
inner dust radius of ~2 AU (mid-IR data) and on the quantity of scattered light
of <10% (H-band data). For an inner radius of 2 AU, the dust distribution must
have a height of at least 1 AU to account for the fractional dust luminosity of
\~20% L_B. Based on the scattered light limit, the dust grains responsible for
the excess emission must have an albedo of <0.33. The presence of the prominent
silicate emission feature at 10 microns implies dust grain radii of >2 microns.
The total mass of the dust, located in a circumbinary disk around the HD 98800
B, is >0.002 M_earth. The orbital dynamics of the A-B pair are likely
responsible for the disk geometry.


title:
From the Top to the Bottom of the Main Sequence: A Complete Mass
  Function of the Young Open Cluster M35

abstract:
  We present very deep and accurate photometry of the open cluster M35 (VRIc
filters). We have covered a region of 27.5x27.5 square arcmin.
  The data range from Ic=12.5 to 23.5 mag, and the color intervals are
0.4\le(V-I)c\le3.0, 0.5\le(R-I)c\le2.5. Roughly, these values span from 1.6
M_\odot down to the substellar limit. By using the location of the stars on
color-magnitude and color-color diagrams, we have selected candidate members of
this cluster. We have merged our sample with previously published data and
obtained a color-magnitude diagram for the complete stellar population of the
cluster, covering the spectral range early B - mid M. The Mass Function
increases monotonically, when plotted in a log-log form, until it reaches ~0.8
M_\odot (\alpha=2.59). It remains shallower for less massive stars (\alpha=0.81
for 0.8-0.2 M_\odot), whereas a decrease ins observed for stars close to the
substellar regime. The total mass of the cluster is ~1600 M_\odot in the area
covered by this study.


title: Incidence and survival of remnant disks around main-sequence stars

abstract:
  We present photometric ISO 60 and 170um measurements, complemented by some
IRAS data at 60um, of a sample of 84 nearby main-sequence stars of spectral
class A, F, G and K in order to determine the incidence of dust disks around
such main-sequence stars. Of the stars younger than 400 Myr one in two has a
disk; for the older stars this is true for only one in ten. We conclude that
most stars arrive on the main sequence surrounded by a disk; this disk then
decays in about 400 Myr. Because (i) the dust particles disappear and must be
replenished on a much shorter time scale and (ii) the collision of
planetesimals is a good source of new dust, we suggest that the rapid decay of
the disks is caused by the destruction and escape of planetesimals. We suggest
that the dissipation of the disk is related to the heavy bombardment phase in
our Solar System. Whether all stars arrive on the main sequence surrounded by a
disk cannot be established: some very young stars do not have a disk. And not
all stars destroy their disk in a similar way: some stars as old as the Sun
still have significant disks.


title:
Simultaneous intensive photometry and high resolution spectroscopy of
  Delta Scuti stars. V. The high--degree modes in the pulsational content of BV
  Circini

abstract:
  We discuss here the pulsation properties of the $\delta$ Scuti star BV
Circini on the basis of data obtained during a simultaneous photometric and
spectroscopic campaign in 1996 and a spectroscopic one in 1998, and taking also
advantage of the previous photometric observations by Kurtz (1981). Nine
pulsation modes were detected from photometry and thirteen from spectroscopy;
five of them are in common to both techniques. The spectroscopic data give
ample evidence of dramatic amplitude variations in some modes, in particular
the strongest spectroscopic mode in 1998 was not detectable in 1996 data. The
two dominant photometric modes (6.33 and 7.89 c\d) are observed on both
seasons. The typing of the modes was performed by means of a simultaneous model
fit of line profile and light variations. The 6.33 c\d photometric term is
probably the fundamental radial mode, while the 7.89 c\d is a nonradial mode
with mi different than 0. There are six high-degree prograde modes with an
azimuthal order m ranging from -12 to -14, and also a retrograde mode with m~7.
These modes combined with the identification of the 6.33 c\d mode allowed us to
estimate i~60 deg for the value of the inclination of the rotation axis. An
accurate evaluation of the main stellar physical parameters is also proposed as
a result of the pulsational analysis.


title: 47 Tuc: The Spectroscopic Versus CMD Age Discrepancy

abstract:
  We investigate current problems in obtaining reliable ages for old stellar
systems based on stellar population synthesis modelling of their integrated
spectra. In particular, we address the large ages derived for the globular
cluster 47 Tuc, which is at odds with its Color-Magnitude-Diagram (CMD) age.
Using a new age indicator, Hgamma_sigma<130, which is particularly effective at
breaking the degeneracy between age and metallicity, we confirm the discrepancy
between the spectroscopic age and the CMD age of 47 Tuc, in that the
spectroscopic age is much older. Nebular emission appears unlikely to be a
source for weakening the observed Balmer lines. We then explore a number of key
parameters affecting the temperature of Turn-Off stars, which are the main
contributors to the Balmer lines for old metal-rich stellar populations. We
find that alpha-enhanced isochrones with atomic diffusion included not only
provides a good fit to the CMD of 47 Tuc, but also leads to a spectroscopic age
in better agreement with the CMD age.


title: XMM-Newton survey of the low-metallicity open cluster NGC 2516

abstract:
  We present the first results of an XMM-Newton EPIC survey of NGC 2516, a
southern low-metallicity open cluster with an age close to the Pleiades. The
attained limiting sensitivity is of ~ 2.4 10^-15 erg sec^-1} cm^-2 in the
0.1--4.0 keV bandpass. This has been achieved by summing the data of the MOS
and PN cameras of two distinct observations for a total exposure time of ~ 33
ks and by analyzing the summed data set with the wavelet detection algorithm
developed at Osservatorio Astronomico di Palermo (OAPA) that has yielded over
200 X-ray detections. Using data just from a single exposure or from a single
camera would have reduced by a factor 2--4 our limiting sensitivity and would
have resulted in 25--40% less X-ray detections. To date, 129 detections have as
counterparts one or more of the 540 photometrically selected cluster members in
the surveyed region, for a total of 147 likely detected members, with unique
identification in 112 cases. We derive the X-ray luminosity functions (XLF) of
NGC 2516 members of different spectral types and compare them with those of the
more metal rich, approximately coeval Pleiades cluster, finding the NGC 2516
photometrically selected dG and dK stars less luminous than the Pleiades. The
XLFs of the NGC 2516 and of the Pleiades dM stars are indistinguishable. We
compare the XMM-Newton results with those recently obtained with Chandra.


title: Combined MEM and MHW analysis of CMB observations

abstract:
  We present a combined maximum-entropy method (MEM) and Mexican Hat wavelet
(MHW) analysis in order to recover the different components of the microwave
sky. We apply this technique to simulated observations by the ESA Planck
satellite in small patches of the sky. In particular, the introduction of the
MHW allows one to detect and subtract the brightest point sources present in
the input data and therefore to improve the reconstructions of the CMB and
foreground components achieved by MEM on its own. In addition, a point source
catalogue at each Planck frequency is produced, which is more complete and
accurate than those obtained by each technique independently.


title: MERLIN/VLA imaging of the gravitational lens system B0218+357

abstract:
  Gravitational lenses offer the possibility of accurately determining the
Hubble parameter (H_0) over cosmological distances, and B0218+357 is one of the
most promising systems for an application of this technique. In particular this
system has an accurately measured time delay (10.5+/-0.4 d; Biggs et al. 1999)
and preliminary mass modelling has given a value for H_0 of 69 +13/-19
km/s/Mpc. The error on this estimate is now dominated by the uncertainty in the
mass modelling. As this system contains an Einstein ring it should be possible
to constrain the model better by imaging the ring at high resolution. To
achieve this we have combined data from MERLIN and the VLA at a frequency of 5
GHz. In particular MERLIN has been used in multi-frequency mode in order to
improve substantially the aperture coverage of the combined data set. The
resulting map is the best that has been made of the ring and contains many new
and interesting features. Efforts are currently underway to exploit the new
data for lensing constraints using the LensClean algorithm (Kochanek & Narayan
1992).


title: Planet Detection Capabilities of the Eddington Mission

abstract:
  Eddington is a space mission for extrasolar planet finding and for
asteroseismic observations. It has been selected by ESA as an F2/F3 reserve
mission with a potential implementation in 2008-13. Here we describe
Eddington's capabilities to detect extrasolar planets, with an emphasis on the
detection of habitable planets. Simulations covering the instrumental
capabilities of Eddington and the stellar distributions in potential target
fields lead to predictions of about 10,000 planets of all sizes and
temperatures, and a few tens of terrestrial planets that are potentially
habitable. Implications of Eddington for future larger scale missions are
briefly discussed.


title:
Ambiguities in Determination Of Self-Affinity in the AE-index Time
  Series

abstract:
  The interaction between the Earth's magnetic field and the solar wind plasma
results in a natural plasma confinement system which stores energy. Dissipation
of this energy through Joule heating in the ionosphere can be studied via the
  Auroral Electrojet (AE) index. The apparent broken power law form of the
frequency spectrum of this index has motivated investigation of whether it can
be described as fractal coloured noise. One frequently-applied test for
self-affinity is to demonstrate linear scaling of the logarithm of the
structure function of a time series with the logarithm of the dilation factor
$\lambda$. We point out that, while this is conclusive when applied to signals
that are self-affine over many decades in $\lambda$, such as Brownian motion,
the slope deviates from exact linearity and the conclusions become ambiguous
when the test is used over shorter ranges of $\lambda$. We demonstrate that non
self-affine time series made up of random pulses can show near-linear scaling
over a finite dynamic range such that they could be misinterpreted as being
self-affine. In particular we show that pulses with functional forms such as
those identified by Weimer within the $AL$ index, from which $AE$ is partly
derived, will exhibit nearly linear scaling over ranges similar to those
previously shown for $AE$ and $AL$. The value of the slope, related to the
Hurst exponent for a self-affine fractal, seems to be a more robust
discriminator for fractality, if other information is available.


title: The 1997 hard state outburst of the X-ray transient GS 1354-64 / BW Cir

abstract:
  We present observations of the 1997 outburst of the X-ray transient GS
1354-64 (BW Cir) at X-ray, optical and, for the first time, radio wavelengths;
this includes upper limits to the linear and circular polarisation of the radio
data. The X-ray outburst was unusual in that the source remained in the
low/hard X-ray state throughout; the X-ray peak was also preceded by at least
one optical outburst, suggesting that it was an `outside-in' outburst - similar
to those observed in dwarf novae systems, although possibly taking place on a
viscous timescale in this case. It therefore indicates that the optical
emission was not dominated by the reprocessing of X-rays but that instead we
see the instability directly. While the radio source was too faint to detect
any extended structure, spectral analysis of the radio data and a comparison
with other similar systems suggests that mass ejections, probably in the form
of a jet, took place and that the emitted synchrotron spectrum may have
extended as far as infrared wavelengths. Finally, we compare this 1997 outburst
of GS 1354-64 with possible previous outbursts and also with other hard state
objects, both transient and persistent. It appears that a set of
characteristics -- such as a weak, flat spectrum radio jet, a mHz QPO
increasing in frequency, a surprisingly high optical:X-ray luminosity ratio and
the observed optical peak preceding the X-ray peak -- may be common to all hard
state X-ray transients.


title:
Modelling gaseous and stellar kinematics in the disc galaxies NGC 772,
  NGC 3898, and NGC 7782

abstract:
  We present V-band surface photometry and major-axis kinematics of stars and
ionized gas of three early-type spiral galaxies, namely NGC 772, NGC 3898 and
NGC 7782. For each galaxy we present a self-consistent Jeans model for the
stellar kinematics, adopting the light distribution of bulge and disc derived
by means of a two-dimensional parametric photometric decomposition. This
allowed us to investigate the presence of non-circular gas motions, and derive
the mass distribution of luminous and dark matter in these objects.
  NGC 772 and NGC 7782 have apparently normal kinematics with the ionized gas
tracing the gravitational equilibrium circular speed. This is not true in the
innermost region (r < 8'') of NGC 3898 where the ionized gas is rotating more
slowly than the circular velocity predicted by dynamical modelling. This
phenomenon is common in the bulge-dominated galaxies for which dynamical
modelling enables us to make the direct comparison between the gas velocity and
the circular speed, and it poses questions about the reliability of galaxy mass
distributions derived by the direct decomposition of the observed ionized-gas
rotation curve into the contributions of luminous and dark matter.


title: From Anisotropy to Omega

abstract:
  Following the recent measurement of the acoustic peak by the BOOMERanG and
MAXIMA experiments in the CMB anisotropy angular power spectrum, many analyses
have found that the geometry of the Universe is very close to flat, but
slightly closed models are favoured. In this paper we will briefly review how
the CMB anisotropies depend on the curvature, explaining any assumptions we
could make and showing that this skewness towards closed models can be easily
explained by degeneracies in the cosmological parameters. While it is difficult
to give independent constraints on the cosmological constant and/or different
forms of dark energies, we will also show that combining CMB measurements with
other observational data will introduce new and tighter constraints, like
$\Omega_\Lambda > 0$ at high significance.


title: Effects of Strong Magnetic Fields on Neutron Star Structure

abstract:
  We study static neutron stars with poloidal magnetic fields and a simple
class of electric current distributions consistent with the requirement of
stationarity. For this class of electric current distributions, we find that
magnetic fields are too large for static configurations to exist when the
magnetic force pushes a sufficient amount of mass off-center that the
gravitational force points outward near the origin in the equatorial plane. (In
our coordinates an outward gravitational force corresponds to $\partial\ln
g_{tt}/\partial r>0$, where $t$ and $r$ are respectively time and radial
coordinates and $g_{tt}$ is coefficient of $dt^2$ in the line element.) For the
equations of state (EOSs) employed in previous work, we obtain configurations
of higher mass than had been reported; we also present results with more recent
EOSs. For all EOSs studied, we find that the maximum mass among these static
configurations with magnetic fields is noticeably larger than the maximum mass
attainable by uniform rotation, and that for fixed values of baryon number the
maximum mass configurations are all characterized by an off-center density
maximum.


title: Constraints on the tensor mode from large scale structure observations

abstract:
  Observational data on the large scale structure (LSS) of the Universe are
used to establish an upper limit for the amplitude of the tensor mode
marginalized over all other cosmological parameters within the class of
adiabatic inflationary models. It is shown that the upper 1$\sigma$ limit for
the contribution of a tensor mode to the COBE DMR data is T/S$<1$.


title: Type Ia Supernovae and Remnant Neutron Stars

abstract:
  On the basis of the current observational evidence, we put forward the case
that the merger of two CO white dwarfs produces both a Type Ia supernova
explosion and a stellar remnant, the latter in the form of a magnetar. The
estimated occurrence rates raise the possibility that many, if not most, SNe Ia
might result from white dwarf mergers.


title: Advection dominated flows around black holes in two dimensions

abstract:
  We show the results of two-dimensional, azimuthally symmetric simulations of
advection dominated fluid flows around black holes. We use the SPH method, and
the alpha-prescription for the viscosity, including all terms in the stress
tensor. We have performed calculations with 0.001 < alpha < 0.2 and find strong
circulation patterns in the flow, on spatial scales that depend on the
magnitude of the viscosity.


title:
Starbursts versus Truncated Star Formation in Nearby Clusters of
  Galaxies

abstract:
  We present long-slit spectroscopy, B and R bandpass imaging, and 21 cm
observations of a sample of early-type galaxies in nearby clusters which are
known to be either in a star-forming phase or to have had star formation which
recently terminated. From the long-slit spectra, obtained with the Blanco 4-m
telescope, we find that emission lines in the star-forming cluster galaxies are
significantly more centrally concentrated than in a sample of field galaxies.
The broadband imaging reveals that two currently star-forming early-type
galaxies in the Pegasus I cluster have blue nuclei, again indicating that
recent star formation has been concentrated. In contrast, the two galaxies for
which star formation has already ended show no central color gradient. The
Pegasus I galaxy with the most evident signs of ongoing star formation
(NGC7648), exhibits signatures of a tidal encounter. Neutral hydrogen
observations of that galaxy with the Arecibo radiotelescope reveal the presence
of ~4 x 10^8 solar masses of HI. Arecibo observations of other current or
recent star-forming early-type galaxies in Pegasus I indicate smaller amounts
of gas in one of them, and only upper limits in others.


title:
Observational Estimates for the Mass-Loss Rates of Alpha Centauri and
  Proxima Centauri Using HST Lyman-alpha Spectra

abstract:
  We study H I Lyman-alpha absorption observed by the Hubble Space Telescope
toward the nearby binary system Alpha Cen (G2 V+K0 V) and its distant companion
star Proxima Cen (M5.5 Ve). Absorption from heliospheric H I heated by the
solar wind/ISM interaction is observed toward both Alpha Cen and Proxima Cen.
Absorption from analogous "astrospheric" material surrounding the stars is
detected toward Alpha Cen, but not Proxima Cen. The nondetection of
astrospheric absorption toward Proxima Cen suggests that the stellar wind of
Proxima Cen must be significantly weaker than that of the Alpha Cen system. We
use hydrodynamic models of the astrospheres computed assuming different
mass-loss rates to predict astrospheric Lyman-alpha absorption for comparison
with the observations. The model that best matches the Alpha Cen data has a
mass-loss rate of twice the solar rate, and the models suggest an upper limit
of 0.2 solar for Proxima Cen. Finally, we note that the heliospheric absorption
observed toward Proxima Cen in 2000 May is identical to the heliospheric
absorption observed toward Alpha Cen in 1995 May, implying that the structure
of the outer heliosphere does not change significantly during the solar
activity cycle.


title: Application of the synchrotron proton blazar model to BL Lac objects

abstract:
  We apply the synchrotron proton blazar (SPB) model to the April 1997 flare of
Markarian 501 and find we are able to fit the observed spectral energy
distribution. We explore the effect of target photon density on the high energy
part of the spectral energy distribution (SED) for fixed assumed magnetic
field, emission region size and Doppler factor and find that the luminosity and
peak frequency of the high energy part of the SED may depend on the luminosity
of the low energy part of the SED in high-frequency peaked BL Lac objects
(HBL).


title: Stars & Gas in the Galaxy Pair II Zw 70/71

abstract:
  II Zw 71 (UGC 9562) was classified as a ``probable'' polar-ring galaxy in the
Polar-Ring Catalog, based upon its optical appearance. We present 21 cm and
optical observations of this galaxy and its companion, the blue star-forming
dwarf II Zw 70. Our 21 cm observations show that 5e8 solar masses of HI is
present in a polar ring orbiting II Zw 71, and show a spatially and
kinematically contiguous streamer with 2.5e8 solar masses of HI gas between the
two galaxies. This gaseous bridge, plus our observations of Halpha line
emission in the polar ring and in II Zw 70, are strong evidence for an ongoing
interaction between the two galaxies. However, the configuration of the
streamer suggests that the polar ring itself may well have predated the current
interaction, which then stimulated an outburst of star formation in the ring
gas.


title: Physics of mirror photons

abstract:
  The physics of kinetic mixing between ordinary and mirror photons is
discussed. An important role is played by four linear combinations we dub the
physical photon, the sterile photon, the physical mirror photon, and the
sterile mirror photon. Because of the mass degeneracy between the two gauge
bosons, quantum coherence effects are important. The physical photon becomes a
certain coherent superposition of the bare ordinary photon and the bare mirror
photon. Similarly, the physical mirror photon is another, but {\it not
orthogonal}, coherent superposition. We discuss the physics of the interaction
between physical mirror photons and ordinary matter. Observational signatures
for some hybrid ordinary/mirror binary astrophysical systems are qualitatively
discussed. We show that a small amount of ordinary matter at the center of a
mirror star may make the mirror star observable. We speculate that the recently
reported halo white dwarfs might actually be mirror halo stars.


title:
Determining the Equation of State of the Expanding Universe Using a New
  Independent Variable

abstract:
  To determine the equation of state of the universe, we propose to use a new
independent variable $R\equiv (H_0/c)(d_L(z)/(1+z))$, where $H_0$ and $d_L(z)$
are the present Hubble parameter and the luminosity distance, respectively. For
the flat universe suggested from the observation of the anisotropy of cosmic
microwave background, the density and the pressure are expressed as
$\rho/\rho_0=4(df/dR)^2/f^6$ and $p/\rho_0=-4/3(d^2f/dR^2)/f^5$ where $\rho_0$
is the present density and $f(R)=1/\sqrt{1+z(R)}$. In $(R, f)$ plane the sign
as well as the strength of the pressure is in proportion to the curvature of
the curve $f(R)$. We propose to adopt a Pade-like expression of
$f(R)=1/\sqrt{u}$ with $u\equiv 1+\sum\limits_{n=1}^{N}u_nR^n$. For flat
$\Lambda$ model the expansion up to N=7 has at most an error $< 0.2%$ for $z <
1.7$ and any value of $\Lambda$. We also propose a general method to determine
the equation of state of the universe which has $N-1$ free parameters. If the
number of parameters are smaller than $N-1$, there is a consistency check of
the equation of state so that we may confirm or refute each model.


title: Remnants from Gamma-Ray Bursts

abstract:
  We model the intermediate time evolution of a "jetted" gamma-ray burst by two
blobs of matter colliding with the interstellar medium. We follow the
hydrodynamical evolution of this system numerically and calculate the
bremsstrahlung and synchrotron images of the remnant. We find that for a burst
energy of $10^{51}$ erg the remnant becomes spherical after $\sim 5000$ years
when it collects $\sim 50M_\odot$ of interstellar mass. This result is
independent of the exact details of the GRB, such as the opening angle. After
this time a gamma-ray burst remnant has an expanding sphere morphology. The
similarity to a supernova remnant makes it difficult distinguish between the
two at this stage. The expected number of non-spherical gamma-ray burst
remnants is $\sim0.05$ per galaxy for a beaming factor of 0.01 and a burst
energy of $10^{51}$ erg. Our results suggest that that the double-shell object
DEM L 316 is not a GRB remnant.


title: XMM-Newton monitoring of X-ray variability in the quasar PKS 0558-504

abstract:
  We present the temporal analysis of X-ray observations of the radio-loud
Narrow-Line Seyfert 1 galaxy (NLS1) PKS 0558-504 obtained during the XMM-Newton
Calibration and Performance Verification (Cal/PV) phase. The long term light
curve is characterized by persistent variability with a clear tendency for the
X-ray continuum to harden when the count rate increases. Another strong
correlation on long time scales has been found between the variability in the
hard band and the total flux. On shorter time scales the most relevant result
is the presence of smooth modulations, with characteristic time of ~ 2 hours
observed in each individual observation. The short term spectral variability
turns out to be rather complex but can be described by a well defined pattern
in the hardness ratio-count rate plane.


title:
Star Formation and Selective Dust Extinction in Luminous Starburst
  Galaxies

abstract:
  We investigate the star formation and dust extinction properties of very
luminous infrared galaxies whose spectra display a strong Hdelta line in
absorption and a moderate [OII] emission (e[a] spectrum). This spectral
combination has been suggested to be a useful method to identify dusty
starburst galaxies at any redshift on the basis of optical data alone. We
compare the average e(a) optical spectrum with synthetic spectra that include
both the stellar and the nebular contribution, allowing dust extinction to
affect differentially the stellar populations of different ages. We find that
reproducing the e(a) spectrum requires the youngest stellar generations to be
significantly more extinguished by dust than older stellar populations, and
implies a strong ongoing star formation activity at a level higher than in
quiescent spirals. A model fitting the optical spectrum does not necessarily
produce the observed FIR luminosity and this can be explained by the existence
of stellar populations which are practically obscured at optical wavelengths.
Models in which dust and stars are uniformly mixed yield a reddening of the
emerging emission lines which is too low compared to observations: additional
foreground reddening is required.


title: Factor analysis of Galactic globular clusters on structural parameters

abstract:
  Principal component method is used to study galactic globular clusters in 7-
and 8-axis space of structural parameters. It is shown that the manifold
properties of clusters with this set of parameters is determined mainly by two
independent factors. This result may be useful for the theory of formation and
evolution of clusters.


title: Two Boehm-Vitense gaps in the main sequence of the Hyades

abstract:
  Hipparcos proper motions and trigonometric parallaxes allow the derivation of
secular parallaxes which fix the distances to individual stars in the Hyades
cluster to an accuracy of \sim 2 percent. The resulting color-absolute
magnitude diagram for 92 high-fidelity single members of the cluster displays a
very narrow main sequence, with two turn-offs and associated gaps. These occur
at the locations where the onset of surface convection affects the B-V colors,
as predicted by Boehm-Vitense thirty years ago. The new distances provide
stringent constraints on the transformations of colors and absolute magnitudes
to effective temperatures and luminosities, and on models of stellar interiors.


title: On the history of the interplay between HD 56925 and NGC 2359

abstract:
  NGC 2359 is an optical nebula excited by the powerful wind and the radiation
of the Wolf-Rayet star HD 56925. We have investigated the interaction between
this massive star and the surrounding neutral gas by analyzing the large-scale
21cm-HI emission and by mapping the nebula in the J = 1-0 and the J = 2-1 lines
of CO. We found a conspicuous (70 x 37 pc) HI shell, expanding at 12 km/s,
likely produced during the main-sequence phase of the star. The molecular gas
towards NGC 2359 shows three velocity components. Two of these components, A1
and A2, have narrow linewidths (1-2 km/s) and radial velocities of 35-38 and
64-68 km/s, respectively. The third component is detected at radial velocities
between 50 and 58 km/s and has a broader profile (up to 5.5 km/s). Furthermore,
this component is morphologicaly related with the nebula and has a velocity
gradient of a few km/s. We have also estimated the physical parameters of the
molecular gas by means of a LVG modelling of the CO emission. The gas projected
onto the southern HII region of the nebula has low CO column density and is
rather hot, probably up to 80 K. Several profiles of the 13CO J = 1-0 line near
the peak of the emission, together with a weak emission bridge between the
broad and one of the narrow components (component A2), suggest the presence of
a shock front acting in the southern part of the nebula. This shock was likely
produced in a previous RSG/LBV phase of HD 56925.


title:
Dissecting the luminosity function of the Coma cluster of galaxies by
  means of CFHT wide field images

abstract:
  By means of wide-field (42x28 arcmin) CCD images of the Coma cluster of
galaxies and of control fields, taken at the Canada-France-Hawaii telescope
with the CFH12K and UH8K cameras, we determine the luminosity function
bi-variate in central brightness. We found a clear progression for a steeping
and weakening of the FL going from high surface brightness galaxies (mu~20$
mag/arcsec2) to galaxies of very-faint central brightnesses (mu 24.5
mag/arcsec2). Compact galaxies, usually rejected in the star/galaxy
classification, are found to be a minor population in Coma. A huge population
of low surface brightness galaxies red and faint are discovered, representing
the largest contributor to the LF at faint magnitudes. Among them, there could
be the remnant of high redshift starbursting galaxies responsible for the
Butcher-Oemler effect.


title:
Resistive Magnetohydrodynamics of Jet Formation and Magnetically Driven
  Accretion

abstract:
  We carried out 2.5-dimensional resistive magnetohydrodynamic simulations to
study the effects of magnetic diffusivity on magnetically driven mass accretion
and jet formation. We found that (1) when the normalized magnetic diffusivity,
is small, mass accretion and jet formation take place intermittently; (2) when
diffusivity is middle, the system evolves toward a quasi-steady state; and the
system evolves toward a quasi-steady state; and (3) when diffusivity is large,
the accretion/mass outflow rate decreases with diffusivity and approaches 0.
The results of these simulations indicate magnetic braking provide a mass
accretion rate which is sufficient to explain the activity of AGNs.


title: The XMM/Megacam-VST/VIRMOS Large Scale Structure Survey

abstract:
  The objective of the XMM-LSS Survey is to map the large scale structure of
the universe, as highlighted by clusters and groups of galaxies, out to a
redshift of about 1, over a single 8x8 sq.deg. area. For the first time, this
will reveal the topology of the distribution of the deep potential wells and
provide statistical measurements at truly cosmological distances. In addition,
clusters identified via their X-ray properties will form the basis for the
first uniformly-selected, multi-wavelength survey of the evolution of clusters
and individual cluster galaxies as a function of redshift. The survey will also
address the very important question of the QSO distribution within the cosmic
web.


title:
Soft X-ray emission lines from a relativistic accretion disk in MCG
  -6-30-15 and Mrk 766

abstract:
  XMM-Newton Reflection Grating Spectrometer (RGS) spectra of the Narrow Line
Seyfert 1 galaxies MCG -6-30-15 and Mrk 766 are physically and
spectroscopically inconsistent with standard models comprising a power-law
continuum absorbed by either cold or ionized matter. We propose that the
remarkably similar features detected in both objects in the 5 - 35 A band are
H-like oxygen, nitrogen, and carbon emission lines, gravitationally redshifted
and broadened by relativistic effects in the vicinity of a Kerr black hole. We
discuss the implications of our interpretation, and demonstrate that the
derived parameters can be physically self-consistent.


title:
Substructure in clusters containing wide-angle tailed radio galaxies. I.
  New redshifts

abstract:
  We present new redshifts and positions for 635 galaxies in nine rich clusters
containing Wide-Angle Tailed (WAT) radio galaxies. Combined with existing data,
we now have a sample of 18 WAT-containing clusters with more than 10 redshifts.
This sample contains a substantial portion of the WAT clusters in the VLA 20 cm
survey of Abell clusters, including 75% of WAT clusters in the complete survey
(z<=0.09), and 20% of WAT clusters with z>0.09. It is a representative sample
which should not contain biases other than selection by radio morphology. We
graphically present the new data using histograms and sky maps. A
semi-automated procedure is used to search for emission lines in the spectra in
order to add and verify galaxy redshifts. We find that the average apparent
fraction of emission line galaxies is about 9% in both the clusters and the
field. We investigate the magnitude completeness of our redshift surveys with
CCD data for a test case, Abell 690. This case indicates that our galaxy target
lists are deeper than the detection limit of a typical MX exposure, and they
are 82% complete down to R=19.0. The importance of the uniformity of the
placement of fibers on targets is posited, and we evaluate this in our
datasets. We find some cases of non-uniformities which may influence dynamical
analyses. A second paper will use this database to look for correlations
between the WAT radio morphology and the cluster's dynamical state.


title: Radio Variability of Sagittarius A* - A 106 Day Cycle

abstract:
  We report the presence of a 106-day cycle in the radio variability of Sgr A*
based on an analysis of data observed with the Very Large Array (VLA) over the
past 20 years. The pulsed signal is most clearly seen at 1.3 cm with a ratio of
cycle frequency to frequency width f/Delta_f= 2.2+/-0.3. The periodic signal is
also clearly observed at 2 cm. At 3.6 cm the detection of a periodic signal is
marginal. No significant periodicity is detected at both 6 and 20 cm. Since the
sampling function is irregular we performed a number of tests to insure that
the observed periodicity is not the result of noise. Similar results were found
for a maximum entropy method and periodogram with CLEAN method. The probability
of false detection for several different noise distributions is less than 5%
based on Monte Carlo tests. The radio properties of the pulsed component at 1.3
cm are spectral index alpha ~ 1.0+/- 0.1 (for S nu^alpha), amplitude Delta
S=0.42 +/- 0.04 Jy and characteristic time scale Delta t_FWHM ~ 25 +/- 5 days.
The lack of VLBI detection of a secondary component suggests that the
variability occurs within Sgr A* on a scale of ~5 AU, suggesting an instability
of the accretion disk.


title: Efficiency and spectrum of internal gamma-ray burst shocks

abstract:
  We present an analysis of the Internal Shock Model of GRBs, where gamma-rays
are produced by internal shocks within a relativistic wind. We show that
observed GRB characteristics impose stringent constraints on wind and source
parameters. We find that a significant fraction, of order 20 %, of the wind
kinetic energy can be converted to radiation, provided the distribution of
Lorentz factors within the wind has a large variance and provided the minimum
Lorentz factor is higher than 10^(2.5)L_(52)^(2/9), where L=10^(52)L_(52)erg/s
is the wind luminosity. For a high, >10 %, efficiency wind, spectral energy
breaks in the 0.1 to 1 MeV range are obtained for sources with dynamical time
R/c < 1 ms, suggesting a possible explanation for the observed clustering of
spectral break energies in this range. The lower limit to wind Lorenz factor
and the upper limit, around (R/10^7 cm)^(-5/6) MeV to observed break energies
are set by Thomson optical depth due to electron positron pairs produced by
synchrotron photons. Natural consequences of the model are absence of bursts
with peak emission energy significantly exceeding 1 MeV, and existence of low
luminosity bursts with low, 1 keV to 10 keV, break energies.


title: Large Scale Structure and Cosmic Rays revisited

abstract:
  We investigate the possibility that ultra high energy cosmic rays (E > 10^19
eV) are related to the distribution of matter on large scales. The large scale
structure (LSS) data stems from the recent IRAS PSCz redshift survey. We
present preliminary predictions drawn from an anisotropic distribution of
sources which follows the galaxy distribution.


title:
Using the 2dF galaxy redshift survey to detect gravitationally-lensed
  quasars

abstract:
  Galaxy redshift surveys can be used to detect gravitationally-lensed quasars
if the spectra obtained are searched for the quasars' emission lines. Previous
investigations of this possibility have used simple models to show that the 2
degree Field (2dF) redshift survey could yield several tens of new lenses, and
that the larger Sloan Digital Sky Survey should contain an order of magnitude
more. However the particular selection effects of the samples were not included
in these calculations, limiting the robustness of the predictions; thus a more
detailed simulation of the 2dF survey was undertaken here. The use of an
isophotal magnitude limit reduces both the depth of the sample and the expected
number of lenses, but more important is the Automatic Plate Measuring survey's
star-galaxy separation algorithm, used to generate the 2dF input catalogue. It
is found that most quasar lenses are classed as merged stars, with only the few
lenses with low-redshift deflectors likely to be classified as galaxies.
Explicit inclusion of these selection effects implies that the 2dF survey
should contain 10 lenses on average. The largest remaining uncertainty is the
lack of knowledge of the ease with which any underlying quasars can be
extracted from the survey spectra.


title:
FUSE Observations of Atomic Abundances and Molecular Hydrogen in the
  Leading Arm of the Magellanic Stream

abstract:
  We present Far Ultraviolet Spectroscopic Explorer observations of the atomic
and molecular absorption in high velocity cloud HVC 287.5+22.5+240, which lies
in front of the ultraviolet-bright nucleus of the Seyfert 1 galaxy NGC 3783. We
detect H2, N I, N II, Si II, and Fe II absorption and set limits on the amount
of absorption due to P III, Ar I, and Fe III. We extend the earlier metallicity
and dust-depletion measurements made by Lu and collaborators by examining the
relative gas-phase abundances of Si, P, S, and Fe. Corrections to the derived
gas-phase abundances due to ionized gas in the HVC are less than 15%. The HVC
has a metallicity of 0.2-0.4 solar, similar to that of the Small Magellanic
Cloud. The relative abundance pattern for the elements studied resembles that
of warm gas in the SMC, which supports the idea that this HVC is part of the
tidally stripped Leading Arm of the Magellanic Stream. The abundance pattern
implies that the HVC contains dust grains that have been processed
significantly. It is likely that the grain mantles have been modified or
stripped back to expose the grain cores. We have identified more than 30 lines
of H2 arising in the HVC from rotational levels J = 0 to J = 3. Synthetic
spectra and a curve-of-growth fit to these lines with b = 12 km/sec indicate
that log N(H2) = 16.80+/-0.10 and f(H2) = 2N(H2)/[N(H I)+2N(H2)] = 0.0016. From
an analysis of the H2 rotational populations, we find an absorption rate (at
1000 A) that is less than one-tenth the average value in the solar
neighborhood. The presence of molecular gas in the HVC requires that either the
H2 formed in situ or that molecules formed within the SMC survived tidal
stripping. We favor the latter possibility because of the long formation time
derived for molecules in this HVC.


title: The statistics of wide-separation lenses

abstract:
  The probability that high-redshift sources are gravitationally-lensed with
large image separations (i.e., greater than can be produced by galactic
deflectors) is determined by the cosmological population of group- and
cluster-sized halos. Thus the observed frequency of wide-separation lensed
quasars can be used to constrain not only the halo distribution, but also a
number of cosmological parameters. A calculation of the optical depth due to
collapsed, isothermal halos is a useful guide to the lens statistics, and
illustrates that the number of wide-separation lenses is a sensitive probe of
the mean density of the universe and the present day density variance whilst
being nearly independent of the cosmological constant.


title: Gravitational lensing in galaxy redshift surveys

abstract:
  Gravitationally-lensed quasars should be discovered as a by-product of large
galaxy redshift surveys, being discovered spectroscopically when a low-redshift
galaxy exhibits high-redshift quasar emission lines. The number of lenses
expected is higher than previously estimated, mainly due to the fact that the
presence of the quasar images brings faint deflector galaxies above the survey
limit. Thus the a posteriori likelihood of the discovery of Q 2237+0305 in the
Center for Astrophysics redshift survey is approximately 0.03. In the future,
the 2 degree Field survey should yield at least 10 lensed quasars, and the
Sloan Digitial Sky Survey up to 100.


title:
Distance-Redshift in Inhomogeneous $Omega_0=1$
  Friedmann-Lemaitre-Robertson-Walker Cosmology

abstract:
  Distance--redshift relations are given in terms of associated Legendre
functions for partially filled beam observations inspatially flat
Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies. These models are
dynamically pressure-free, flat FLRW on large scales but, due to mass
inhomogeneities, differ in their optical properties. The partially filled beam
area-redshift equation is a Lame$^{\prime}$ equation for arbitrary FLRW and is
shown to simplify to the associated Legendre equation for the spatially flat,
i.e. $\Omega_0=1$ case. We fit these new analytic Hubble curves to recent
supernovae (SNe) data in an attempt to determine both the mass parameter
$\Omega_m$ and the beam filling parameter $\nu$. We find that current data are
inadequate to limit $\nu$. However, we are able to estimate what limits are
possible when the number of observed SNe is increased by factor of 10 or 100,
sample sizes achievable in the near future with the proposed SuperNova
Acceleration Probe satellite.


title: Gamma Ray Burst progenitors - a case for helium star mergers

abstract:
  Recently much work in Gamma-Ray Burst (GRB) studies was devoted to revealing
the nature of outburst mechanism and to looking for GRB progenitors. Several
types of progenitors were proposed for GRBs. Most promising objects are
collapsars, compact object binaries, Helium star mergers and recently discussed
supernovae. In this paper we consider four proposed binary star progenitors of
GRBs: double neutron star (NS-NS), black hole neutron star (BH-NS), black hole
white dwarf (BH-WD) mergers and Helium star mergers (He-BH). Helium star
mergers are a possible outcome of common envelope evolution of a compact object
entering the envelope of a giant with a helium core.
  Using population synthesis we calculate number of the binary progenitors and
show that BH-WD and Helium star mergers dominate population of the proposed
binary progenitors. Comparison of distribution of different binary mergers
around galaxies they are born in, with localization of GRB afterglows in their
host galaxies shows that only Helium mergers may be responsible for GRBs with
observed afterglows while it excludes NS-NS, BH-NS and BH-WD systems as GRB
progenitors. Assuming that all GRBs come from Helium star mergers and comparing
numbers of Helium star mergers with observed BATSE GRB rate let us derive upper
limit on GRB collimation to be 4 degrees.


title: A Luminous Infrared Companion in the Young Triple System WL 20

abstract:
  We present spatially resolved near-infrared and mid-infrared (1-25 microns)
imaging of the WL 20 triple system in the nearby (d=125 pc) rho Ophiuchi
star-forming cloud core. We find WL 20 to be a new addition to the rare class
of "infrared companion systems", with WL 20:E and WL 20:W displaying Class II
(T-Tauri star) spectral energy distributions (SEDs) and total luminosities of
0.61 and 0.39 L_sun, respectively, and WL 20:S, the infrared companion, with a
Class I (embedded protostellar) SED and a luminosity of 1.0-1.8 L_sun. WL 20:S
is found to be highly variable over timescales of years, to be extended (40 AU
diameter) at mid-infrared wavelengths, and to be the source of the centimeter
emission in the system. The photospheric luminosities, estimated from our data,
allow us to compare and test current pre-main-sequence evolutionary tracks. WL
20:E and WL 20:W fall into the region of the H-R diagram in which sources may
appear up to twice as old as they actually are using non-accreting tracks, a
fact which may reconcile the co-existence of two T-Tauri stars with an embedded
protostar in a triple system. The derived masses and observed projected
separations of the components of the WL 20 triple system indicate that it is in
an unstable dynamical configuration, and may therefore provide an example of
dynamical evolution during the pre-main-sequence phase.


title:
The Deuterium to Hydrogen Abundance Ratio Towards a Fourth QSO:
  HS0105+1619

abstract:
  We report the measurement of the primordial D/H abundance ratio towards QSO
\object. The column density of the hydrogen in the $z \simeq 2.536$ Lyman limit
system is high, \lnhi $= 19.422 \pm 0.009$ \cmm, allowing for the deuterium to
be seen in 5 Lyman series transitions. The measured value of the D/H ratio
towards QSO \object is found to be D/H$ = 2.54 \pm 0.23 \times 10^{-5}$. The
metallicity of the system showing D/H is found to be $\simeq 0.01$ solar,
indicating that the measured D/H is the primordial D/H within the measurement
errors. The gas which shows D/H is neutral, unlike previous D/H systems which
were more highly ionized. Thus, the determination of the D/H ratio becomes more
secure since we are measuring it in different astrophysical environments, but
the error is larger because we now see more dispersion between measurements.
Combined with prior measurements of D/H, the best D/H ratio is now D/H$ = 3.0
\pm 0.4 \times 10^{-5}$, which is 10% lower than the previous value. The new
values for the baryon to photon ratio, and baryonic matter density derived from
D/H are $\eta = 5.6 \pm 0.5 \times 10^{-10} $ and \ob $=0.0205 \pm 0.0018$
respectively.


title: Tests for primordial non-Gaussianity

abstract:
  We investigate the relative sensitivities of several tests for deviations
from Gaussianity in the primordial distribution of density perturbations. We
consider models for non-Gaussianity that mimic that which comes from inflation
as well as that which comes from topological defects. The tests we consider
involve the cosmic microwave background (CMB), large-scale structure (LSS),
high-redshift galaxies, and the abundances and properties of clusters. We find
that the CMB is superior at finding non-Gaussianity in the primordial
gravitational potential (as inflation would produce), while observations of
high-redshift galaxies are much better suited to find non-Gaussianity that
resembles that expected from topological defects. We derive a simple expression
that relates the abundance of high-redshift objects in non-Gaussian models to
the primordial skewness.


title: Gamma and Cosmic-Ray Tests of Special Relativity

abstract:
  Lorentz symmetry violation (LSV) at Planck scale can be tested (see e.g.
physics/0003080) through ultra-high energy cosmic rays (UHECR). In a deformed
Lorentz symmetry (DLS) pattern where the effective LSV parameter varies like
the square of the momentum scale (quadratically deformed relativistic
kinematics, QDRK), a 10E-6 LSV at Planck scale would be enough to produce
observable effects on the properties of cosmic rays at the 10E20 eV scale:
absence of GZK cutoff, stability of unstable particles, lower interaction
rates, kinematical failure of any parton model and of standard formulae for
Lorentz contraction and time dilation... Its phenomenological implications are
compatible with existing data. If the effective LSV parameter is taken to vary
linearly with the momentum scale (linearly deformed relativistic kinematics,
LDRK), a LSV at Planck scale larger than 10E-7 eV seems to lead to
contradictions with data above TeV energies. Consequences are important for
high-energy gamma-ray experiments, as well as for high-energy cosmic rays and
gravitational waves.


title: Lorentz Symmetry Violation and Acceleration in Relativistic Shocks

abstract:
  In previous papers (e.g. physics/0003080 and references therein), it was
pointed out that Lorentz symmetry violation (LSV) at Planck scale can play a
crucial role in astrophysical processes at very high energy. It can potentially
inhibit radiation under external forces (e.g. synchrotron-like), GZK-like
cutoffs, decays, photodisintegration of nuclei, momentum loss trough collisions
(e.g. with a photon wind in reverse shocks), production of lower-energy
secondaries... An updated description of this phenomenon is presented, focusing
on acceleration in relativistic shocks and having in mind a model where the
effective parameter driving LSV would vary like the square of the momentum
scale (Quadratically Deformed Relativistic Kinematics, QDRK). Implications for
ultra-high energy (UHE) neutrino production are equally discussed.


title:
Population synthesis of neutron stars, strange (quark) stars and black
  holes

abstract:
  We compute and present the distribution in mass of single and binary neutron
stars, strange stars, and black holes. The calculations were performed using a
stellar population synthesis code. We follow all phases of single and binary
evolution, starting from a ZAMS binary and ending in the creation of one
compact object (neutron star, black hole, strange star) and a white dwarf, or
two compact objects (single or binary). We assume that neutron stars are formed
in the collapse of iron/nickel cores in the mass range M0 < M < M1, quark stars
in the range M1 < M < M2, and black holes for core masses M > M2 and find that
the population of quark stars can easily be as large as the population of black
holes, even if there is only a small mass window for their formation.


title: Explosive Nucleosynthesis in Hypernovae

abstract:
  We examine the characteristics of nucleosynthesis in 'hypernovae', i.e.,
supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs). We
carry out detailed nucleosynthesis calculations for these energetic explosions
and compare the yields with those of ordinary core-collapse supernovae. We find
that both complete and incomplete Si-burning takes place over more extended,
lower density regions, so that the alpha-rich freezeout is enhanced and
produces more Ti in comparison with ordinary supernova nucleosynthesis. In
addition, oxygen and carbon burning takes place in more extended, lower density
regions than in ordinary supernovae. Therefore, the fuel elements O, C, Al are
less abundant while a larger amount of Si, S, Ar, and Ca ("Si") are synthesized
by oxygen burning; this leads to larger ratios of "Si"/O in the ejecta.
Enhancement of the mass ratio between complete and incomplete Si-burning
regions in the ejecta may explain the abundance ratios among iron-peak elements
in metal-poor stars. Also the enhanced "Si"/O ratio may explain the abundance
ratios observed in star burst galaxies. We also discuss other implications of
enhanced [Ti/Fe] and [Fe/O] for Galactic chemical evolution and the abundances
of low mass black hole binaries.


title:
Black Hole Magnetospheres Around Thin Disks Driving Inward and Outward
  Winds

abstract:
  We construct a simple model for stationary, axisymmetric black-hole
magnetospheres, in which the poloidal magnetic field is generated by a toroidal
electric current in a thin disk with the inner edge, by solving the vacuum
Maxwell equations in Schwarzschild background. In this work, to obtain a
concise analytical form of the magnetic stream function, we use the
approximation that the inner edge is far distant from the event horizon. The
global magnetospheric structure with the closed-loop and open field lines
threading the inner and outer parts of the disk is explicitly shown, claiming
that the model is useful as a starting point to study astrophysical problems
involving inward disk-driven winds to a black hole and outward ones to
infinity. The asymptotic shape of the field lines at the event horizon becomes
nearly cylindrical, while at infinity it becomes conical. The magnetic spot in
the disk connected with the black hole through the loop field lines occupies a
very narrow region with the ring area roughly equal to the horizon area. By
taking account of the existence of a uniform (external) magnetic field, we also
obtain the model for collimated open field lines. Then, it is found that the
magnetic connection between the black hole and the disk breaks down if the
uniform field is strong enough. Considering slow rotation of the magnetosphere
and angular momentum transfer by inward winds from the disk, the final
discussion is devoted to gradual disruption of the closed loops due to radial
accretion of disk plasma toward the black hole.


title:
The EUV excess emission of the Virgo and A1795 clusters - re-observation
  with in-situ background measurements

abstract:
  The Virgo and A1795 clusters of galaxies were re-observed by EUVE with {\it
in situ} background measurements by pointing at small offsets. Earlier, a
similar re-observational strategy applied to the cluster A2199 revealed that
the background radial profile was consistent with a flat distribution, and
therefore the original method of extracting cluster EUV signals by the
subtraction of an aymptotically determined background was valid. It is shown
here that the same conclusions hold for the current sample. A model of the
background was obtained from its known properties and the {\it in situ}
measurements, and the subtracted cluster fluxes remain in agreement with those
reported in our discovery papers. They are also consistent with results from
the most conservative procedure of direct point-to-point subtraction of the
{\it in situ} background and proper error propagation, which still preserves
the existence of the EUV excess and its rising radial trend. We present
evidence which argues against the soft excess as due to peculiarities in the
line-of-sight Galactic absorption. The data appear to favor a thermal origin of
the emission.


title:
Hydrodynamical simulations of the Sunyaev-Zel'dovich effect: the kinetic
  effect

abstract:
  We use hydrodynamical N-body simulations to study the kinetic
Sunyaev-Zel'dovich effect. We construct sets of maps, one square degree in
size, in three different cosmological models. We confirm earlier calculations
that on the scales studied the kinetic effect is much smaller than the thermal
(except close to the thermal null point), with an rms dispersion smaller by
about a factor five in the Rayleigh-Jeans region. We study the redshift
dependence of the rms distortion and the pixel distribution at the present
epoch. We compute the angular power spectra of the maps, including their
redshift dependence, and compare them with the thermal Sunyaev-Zel'dovich
effect and with the expected cosmic microwave background anisotropy spectrum as
well as with determinations by other authors. We correlate the kinetic effect
with the thermal effect both pixel-by-pixel and for identified thermal sources
in the maps to assess the extent to which the kinetic effect is enhanced in
locations of strong thermal signal.


title: Recent CMB Observations and the Ionization History of the Universe

abstract:
  Interest in non-standard recombination scenarios has been spurred by recent
cosmic microwave background (CMB) results from BOOMERANG and MAXIMA, which show
an unexpectedly low second acoustic peak, resulting in a best-fit baryon
density that is 50% larger than the prediction of big-bang nucleosynthesis
(BBN). This apparent discrepancy can be avoided if the universe has a
non-standard ionization history in which the recombination of hydrogen is
significantly delayed relative to the standard model. While future CMB
observations may eliminate this discrepancy, it is useful to develop a general
framework for analyzing non-standard ionization histories. We develop such a
framework, examining non-standard models in which the hydrogen binding energy
E_b and the overall expression for the time rate of change of the ionized
fraction of electrons are multiplied by arbitrary factors. This set of models
includes a number of previously-proposed models as special cases. We find a
wide range of models with delayed recombination that are able to fit the CMB
data with a baryon density in accordance with BBN, but there are even allowed
models with earlier recombination than in the standard model. A generic
prediction of these models is that the third acoustic CMB peak should be very
low relative to what is found in the standard model. This is the case even for
the models with earlier recombination than in the standard model, because here
the third peak is lowered by an increased diffusion damping at recombination
relative to the standard model. Interestingly, the specific height of the third
peak depends sensitively on the model parameters, so that future CMB
measurements will be able to distinguish between different non-standard
recombination scenarios.


title: Intracluster Supernova as a Possible Extra Energy Source of Clusters

abstract:
  The observed luminosity -- temperature relation of clusters is considerably
steeper than that expected from a simple scaling relation. Although extra
energy input is a likely solution, its source has not been identified. We
propose intracluster supernova as a possible source, and also predict the
supernova rate in intracluster space as a critical test.


title:
A Strategy for Identifying the Grid Stars for the Space Interferometry
  Mission (SIM)

abstract:
  We present a strategy to identify several thousand stars that are
astrometrically stable at the micro-arcsecond level for use in the SIM (Space
Interferometry Mission) astrometric grid. The requirements on the grid stars
make this a rather challenging task. Taking a variety of considerations into
account we argue for K giants as the best type of stars for the grid, mainly
because they can be located at much larger distances than any other type of
star due to their intrinsic brightness. We show that it is possible to identify
suitable candidate grid K giants from existing astrometric catalogs. However,
double stars have to be eliminated from these candidate grid samples, since
they generally produce much larger astrometric jitter than tolerable for the
grid. The most efficient way to achieve this is probably by means of a radial
velocity survey. To demonstrate the feasibility of this approach, we repeatedly
measured the radial velocities for a pre-selected sample of 86 nearby Hipparcos
K giants with precisions of 5-8 m/s. The distribution of the intrinsic radial
velocity variations for the bona-fide single K giants shows a maximum around 20
m/s, which is small enough not to severely affect the identification of stellar
companions around other K giants. We use the results of our observations as
input parameters for Monte-Carlo simulations on the possible design of a radial
velocity survey of all grid stars. Our favored scenario would result in a grid
which consists to 68% of true single stars and to 32% of double or multiple
stars with periods mostly larger than 200 years, but only 3.6% of all grid
stars would display astrometric jitter larger than 1 microarcsecond. This
contamination level is probably tolerable.


title: Angular separations of the lensed QSO images

abstract:
  We have analyzed the observed image separations of the gravitationally lensed
images of QSOs for a possible correlation with the source redshift. Contrary to
the previously noted anti-correlation based on a smaller data set, no
correlation is found for the currently available data. We have calculated the
average image separations of the lensed QSOs as a function of source redshifts,
for isothermal spheres with cores in a flat universe, taking into account the
amplification bias caused by lensing. The shape of the distribution of average
image separation as a function of redshift is very robust and is insensitive to
most model parameters. Observations are found to be roughly consistent with the
theoretical results for models which assume the lens distribution to be (i)
Schechter luminosity function which, however, can not produce images with large
separation and (ii) the mass condensations in a cold dark matter universe, as
given by the Press-Schechter theory if an upper limit of 1-7$\times 10^{13}$
M$\odot$ is assumed on the mass of the condensations.


title: On the nature of the microquasar V4641 Sagittarii

abstract:
  We present photometric and spectroscopic optical and near-infrared (NIR)
observations taken during the outburst on September 1999 of the source V4641
Sgr = SAX J1819.3-2525 (in'tzand et al., 2000) = XTE J1819-254 (Markwardt et
al., 1999). We show that our observations suggest a distance between 4 and 8
kpc, the spectral type of the companion star being constrained between B3 and
A2 V, making the system a High Mass X-ray Binary System (HMXB). In view of the
radio and optical/NIR observations, it is possible that the ejecta of the
source interacted with the surrounding medium of the source.


title: XMM - Newton observations of Markarian 421

abstract:
  The BL Lac object Mrk 421 was observed on May 25, 2000 during the XMM -
Newton CAL/PV phase. The high throughput of the X-ray telescopes and the
spectral capabilities of the instruments allow an uninterrupted temporal and
spectral study of the source with unprecedented time resolution. Mrk 421 was
found at a relatively high state with a 2-6 keV flux of (1.3 - 1.9)E-10 erg
cm**-2 s **-1. The observed intensity variations by more than a factor of three
at highest X-ray energies are accompanied by complex spectral variations with
only a small time lag (tau = 265 {+116} {-102} seconds) between the hard and
soft photons. The (0.2-10) keV spectrum can be well fitted by a broken power
law and no absorption structures are found in the source spectrum at the high
spectral resolution of the transmission gratings.


title: Broadband X-ray Spectroscopy of GRS 1915+105

abstract:
  We analyzed RXTE data of GRS 1915+105 of X-ray low states between 1996 and
1998. The X-ray spectrum is dominated by the power law component. We found (i)
that the power law is pivoting at 10-30 keV, (ii) that the power law slope
correlates with radio flux, (iii) three different groups of 3-10 keV residuals,
(iv) that one of these residual groups correlates with the power law slope.


title: Before Inflation

abstract:
  Observations of the cosmic microwave sky are revealing the primordial
non-uniformities from which all structure in the Universe grew. The only known
physical mechanism for generating the inhomogeneities we see involves the
amplification of quantum fluctuations during a period of inflation. Developing
the theory further will require progress in quantum cosmology, connecting
inflation to a theory of the initial state of the Universe. I discuss recent
work within the framework of the Euclidean no boundary proposal, specifically
classical instanton solutions and the computation of fluctuations around them.
Within this framework, and for a generic inflationary theory, it appears that
an additional anthropic constraint is required to explain the observed
Universe. I outline an attempt to impose such a constraint in a precise
mathematical manner.


title: The eclipsing bursting X-ray binary EXO 0748-676 revisited by XMM-Newton

abstract:
  The bright eclipsing and bursting low-mass X-ray binary EXO 0748-676 has been
observed at several occasions by XMM-Newton during the initial calibration and
performance verification (CAL/PV) phase. We present here the results obtained
from observations with the EPIC cameras. Apart from several type-I X-ray
bursts, the source shows a high degree of variability with the presence of soft
flares. The wide energy coverage and high sensitivity of XMM-Newton allows for
the first time a detailed description of the spectral variability.
  The source is found to be the superposition of a central (~2 10^8 cm)
Comptonized emission, most probably a corona surrounding the inner edge of an
accretion disk, associated with a more extended (~3 10^10 cm) thermal halo at a
typical temperature of ~0.6 keV with an indication of non-solar abundances.
Most of the variations of the source can be accounted for by a variable
absorption affecting only the central comptonized component and reaching up to
NH ~1.3 10^23 cm^{-2}. The characteristics of the surrounding halo are found
compatible with an irradiated atmosphere of an accretion disc which intercepts
the central emission due to the system high inclination.


title: CMB anisotropies in pre-big bang cosmology

abstract:
  We present an alternative scenario for cosmic structure formation where
initial fluctuations are due to Kalb-Ramond axions produced during a pre-big
bang phase of inflation. We investigate whether this scenario, where the
fluctuations are induced by seeds and therefore are of isocurvature nature, can
be brought in agreement with present observations by a suitable choice of
cosmological parameters. We also discuss several observational signatures which
can distinguish axion seeds from standard inflationary models.


title: Measuring Cluster Temperature Profiles with XMM/EPIC

abstract:
  Using the PV observation of A1795, we illustrate the capability of XMM-EPIC
to measure cluster temperature profiles, a key ingredient for the determination
of cluster mass profiles through the equation of hydrostatic equilibrium. We
develop a methodology for spatially resolved spectroscopy of extended sources,
adapted to XMM background and vignetting characteristics. The effect of the
particle induced background is discussed. A simple unbiased method is proposed
to correct for vignetting effects, in which every photon is weighted according
to its energy and location on the detector. We were able to derive the
temperature profile of A1795 up to 0.4 times the virial radius. A significant
and spatially resolved drop in temperature towards the center (r<200 kpc) is
observed, which corresponds to the cooling flow region of the cluster. Beyond
that region, the temperature is constant with no indication of a fall-off at
large radii out to 1.2 Mpc.


title: Radio Observations of High Redshift Star Forming Galaxies

abstract:
  I summarize recent results from radio observations of high redshift star
forming galaxies, discuss radio continuum emission as a measure of star
formation rate, and consider future capabilities at cm to IR wavelengths.


title: Interstellar Turbulence: I. Retrieval of Velocity Field Statistics

abstract:
  We demonstrate the capability of Principal Component Analysis (PCA) as
applied by Heyer & Schloerb (1997) to extract the statistics of turbulent
interstellar velocity fields as measured by the energy spectrum, E(k)= k^-beta.
Turbulent velocity and density fields with known statistics are generated from
fBm simulations. These fields are translated to the observational domain,
T(x,y,v), considering the excitation of molecular rotational energy levels and
radiative transfer. Using PCA and the characterization of velocity and spatial
scales from the eigenvectors and eigenimages respectively, a relationship is
identified which describes the magnitude of line profile differences, deltav,
and the scale, L, over which these differences occur, deltav=L^alpha. From a
series of models with varying values of beta, we find, alpha = 0.33beta - 0.05
for 1 < beta < 3. This provides the basic calibration between the intrinsic
velocity field statistics to observational measures and a diagnostic for
turbulent flows in the interstellar medium. We also investigate the effects of
noise, line opacity, and finite resolution on these results.


title: Hiden Star Formation: The Ultraviolet Perspective

abstract:
  Many recent estimates of the star formation rate density at high redshift
rely on rest-frame ultraviolet (UV) data. These are highly sensitive to dust
absorption. Applying a correlation between the far-infrared (FIR) to UV flux
ratio and UV color found in a local starbursts to galaxy samples out to z ~ 3,
one can account for most of the FIR background. However, the correlation is
based on a sample that does not include the most extreme starbursts, Ultra
Luminous Infrared Galaxies (ULIGs). Our new UV images of ULIGs show that their
FIR fluxes are underpredicted by this correlation by factors ranging from 7 to
70. We discuss how ULIGs compare to the various types of high-z galaxies:
sub-mm sources, Lyman Break Galaxies, and Extremely Red Objects.


title: Cosmological Parameter Estimation from CMB Experiments

abstract:
  I review the general aspects of cosmological parameter estimation from
observations of the cosmic microwave background (CMB) temperature anisotropies
in the framework of inflationary adiabatic models. The most recent CMB datasets
are starting to give good constraints on the relevant parameters of
inflationary adiabatic models. They point toward a model consistent with the
basic predictions of inflation: a nearly flat universe, with a nearly scale
invariant spectrum of primordial fluctuation.


title:
Galaxy Morphological Segregation in Clusters: Local vs. Global
  Conditions

abstract:
  We study the relative fraction of galaxy morphological types in clusters, as
a function of the projected local galaxy density and different global
parameters: cluster projected gas density, cluster projected total mass density
, and reduced clustercentric distance. Since local and global densities are
correlated, we have considered different tests to search for the parameters to
which segregation show the strongest dependence. Also, we have explored the
results of our analysis applied to the central regions of the clusters and
their outskirts. We consider a sample of clusters of galaxies with temperature
estimates to derive the projected mass density profile and the 500 density
contrast radius ($r_{500}$) using the NFW model and the scaling relation
respectively. The X-ray surface brightness profiles are used to obtain the
projected gas density assuming the hydrostatic equilibrium model. Our results
suggest that the morphological segregation in clusters is controlled by the
local galaxy density in the outskirts. On the other hand, the global projected
mass density, shows the strongest correlation with the fraction of
morphological types in the central high density region, with a marginal
dependence on the local galaxy density.


title:
Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 from the
  Nuclear Stellar Dynamics

abstract:
  We analyze the nuclear stellar dynamics of the SB0 galaxy NGC 1023, utilizing
observational data both from the Space Telescope Imaging Spectrograph aboard
the Hubble Space Telescope and from the ground. The stellar kinematics measured
from these long-slit spectra show rapid rotation (V = 70 km/s at a distance of
0.1 arcsec = 4.9 pc from the nucleus) and increasing velocity dispersion toward
the nucleus (where sigma = 295 +/- 30 km/s). We model the observed stellar
kinematics assuming an axisymmetric mass distribution with both two and three
integrals of motion. Both modeling techniques point to the presence of a
central dark compact mass (which presumably is a supermassive black hole) with
confidence > 99%. The isotropic two-integral models yield a best-fitting black
hole mass of (6.0 +/- 1.4) x 10^7 M_sun and mass-to-light ratio (M/L_V) of 5.38
+/- 0.08, and the goodness-of-fit (chi^2) is insensitive to reasonable values
for the galaxy's inclination. The three-integral models, which
non-parametrically fit the observed line-of-sight velocity distribution as a
function of position in the galaxy, suggest a black hole mass of (3.9 +/- 0.4)
x 10^7 M_sun and M/L_V of 5.56 +/- 0.02 (internal errors), and the edge-on
models are vastly superior fits over models at other inclinations. The internal
dynamics in NGC 1023 as suggested by our best-fit three-integral model shows
that the velocity distribution function at the nucleus is tangentially
anisotropic, suggesting the presence of a nuclear stellar disk. The nuclear
line of sight velocity distribution has enhanced wings at velocities >= 600
km/s from systemic, suggesting that perhaps we have detected a group of stars
very close to the central dark mass.


title: XMM-Newton EPIC and RGS observations of LMC X-3

abstract:
  We report the results of preliminary analysis of the XMM_Newton EPIC and RGS
observations of the candidate black-hole binary LMC X-3 between February and
June 2000. The observations covered both the soft and the hard X-ray spectral
states. The hard-state spectra were dominated by a power-law component with a
photon index Gamma = 1.9 +/- 0.1. The soft-state spectra consisted of a thermal
component with a multi-colour disk temperature T_in = 0.9 keV and a power-law
tail with Gamma ~ 2.5--2.7. The model in which the X-rays from LMC X-3 in the
high-soft state are powered by a strong stellar wind from a massive companion
is not supported by the small line-of-sight absorption (n_H <~ 10^{21} cm^{-2})
deduced from the RGS data. The transition from the soft to the hard state
appears to be a continuous process associated with the changes in the
mass-transfer rate.


title:
Exploding and Non-exploding Stars: Coupling Nuclear Reaction Networks to
  Multidimensional Hydrodynamics

abstract:
  After decades of one-dimensional nucleosynthesis calculations, the growth of
computational resources has meanwhile reached a level, which for the first time
allows astrophysicists to consider performing routinely realistic
multidimensional nucleosynthesis calculations in explosive and, to some extent,
also in non-explosive environments. In the present contribution we attempt to
give a short overview of the physical and numerical problems which are
encountered in these simulations. In addition, we assess the accuracy that can
be currently achieved in the computation of nucleosynthetic yields, using
multidimensional simulations of core collapse supernovae as an example.


title:
Unified Electronic Recombination Of Ne-like Fe XVII: Implications for
  Modeling X-Ray Plasmas

abstract:
  Unified recombination cross sections and rates are computed for (e + Fe
XVIII) --> Fe XVII including non-resonant and resonant (radiative and
di-electronic recombination, RR and DR) processes in an ab initio manner with
relativistic fine structure. The highly resolved theoretical cross sections
exhibit considerably more resonance structures than observed in the heavy-ion
storage ring measurements at Heidelberg, Germany. Nonetheless, the detailed
resonance complexes agree well with experiment, and the unfiied rates agree
with the sum of experimentally derived DR and theoretical RR rates to ~ 20%,
within experimental or theoretical uncertainties. Theoretical results may
provide estimates of field ionization of rydberg levels close to the DR peak,
and non-resonant background contirbutions, particularly close to the RR peak as
E --> 0. More generally, the unified results avoid the physical and practical
problems in astrophysical models inherent in the separation of electronic
recombination into RR and DR on the one hand, and further subdivision into
low-energy Delta n = 0 DR and high-energy Delta n > 0 DR in photoionized and
collisionally ionized X-ray plasmas.


title: The Discovery of a Giant H-alpha Filament in NGC 7213

abstract:
  The nearby Seyfert galaxy NGC 7213 has been imaged in H-alpha and HI with the
CTIO 1.5 m telescope and with the Australia Telescope Compact Array (ATCA),
respectively. Optically NGC 7213 looks undisturbed and relatively featureless
but the continuum-subtracted H-alpha image shows a 19 kpc long filament located
approximately 18.6 kpc from the nucleus. The H-alpha filament could be neutral
gas photo-ionized by the active nucleus, as has been suggested for the Seyfert
galaxy NGC 5252, or shock-ionized by a jet interacting with the surrounding HI,
as has been suggested for the radio galaxy PKS 2240-41. The HI map reveals NGC
7213 to be a highly disturbed system suggesting a past merging event.


title: The formation of life

abstract:
  The formation of life is an automatic stage in the consolidation of rocky or
"terrestrial" planets. The organic (=carbonaceous) matter, light elements,
gases, and water must "float" toward the surface and the heavier metals must
sink toward the center. Random processes in the molecular soup that fills
microfractures in unmelted crust eventually produce self-replicating
microtubules. In an appendix I suggest that some primordial crust remains
because there is not enough consolidation energy to melt the whole planet.
Energy is lost when iron planetesimals first partially melt and then coalesce
to form the molten iron planetary core. Stony planetesimals accrete onto the
surface of an already consolidated core.


title:
The Butcher-Oemler Effect in 295 Clusters: Strong Redshift Evolution and
  Cluster Richness Dependence

abstract:
  We examine the Butcher-Oemler effect and its cluster richness dependence in
the largest sample studied to date: 295 Abell clusters. We find a strong
correlation between cluster richness and the fraction of blue galaxies, f_B, at
every redshift. The slope of the f_B(z) relation is similar for all richnesses,
but at a given redshift, f_B is systematically higher for poor clusters. This
is the chief cause of scatter in the f_B vs. z diagram: the spread caused by
the richness dependence is comparable to the trend in f_B over a typical
redshift baseline, so that conclusions drawn from smaller samples have varied
widely. The two parameters, z, and a consistently defined projected galaxy
number density, N, together account for all of the observed variation in f_B
within the measurement errors. The redshift evolution of f_B is real, and
occurs at approximately the same rate for clusters of all richness classes.


title: Radio Observations of the Supernova Remnant Candidate G312.5-3.0

abstract:
  The radio images from the Parkes-MIT-NRAO (PMN) Southern Sky Survey at 4850
MHz have revealed a number of previously unknown radio sources. One such
source, G312.5-3.0 (PMN J1421-6415), has been observed using the
multi-frequency capabilities of the Australia Telescope Compact Array (ATCA) at
frequencies of 1380 MHz and 2378 MHz. Further observations of the source were
made using the Molonglo Observatory Synthesis Telescope (MOST) at a frequency
of 843 MHz. The source has an angular size of 18 arcmin and has a distinct
shell structure. We present the reduced multi-frequency observations of this
source and provide a brief argument for its possible identification as a
supernova remnant.


title: Simulations of Deep Pencil-Beam Redshift Surveys

abstract:
  We create mock pencil-beam redshift surveys from very large cosmological
$N$-body simulations of two Cold Dark Matter cosmogonies, an Einstein-de Sitter
model ($\tau$CDM) and a flat model with $\Omega_0 =0.3$ and a cosmological
constant ($\Lambda$CDM). We use these to assess the significance of the
apparent periodicity discovered by Broadhurst et al. (1990). Simulation
particles are tagged as `galaxies' so as to reproduce observed present-day
correlations. They are then identified along the past light-cones of
hypothetical observers to create mock catalogues with the geometry and the
distance distribution of the Broadhurst et al. data. We produce 1936 (2625)
quasi-independent catalogues from our $\tau$CDM ($\Lambda$CDM) simulation. A
couple of large clumps in a catalogue can produce a high peak at low
wavenumbers in the corresponding one-dimensional power spectrum, without any
apparent large-scale periodicity in the original redshift histogram. Although
the simulated redshift histograms frequently display regularly spaced clumps,
the spacing of these clumps varies between catalogues and there is no
`preferred' period over our many realisations. We find only a 0.72 (0.49) per
cent chance that the highest peak in the power spectrum of a $\tau$CDM
($\Lambda$CDM) catalogue has a peak-to-noise ratio higher than that in the
Broadhurst et al. data. None of the simulated catalogues with such high peaks
shows coherently spaced clumps with a significance as high as that of the real
data. We conclude that in CDM universes, the kind of regularity observed by
Broadhurst et al. has a priori probability well below $10^{-3}$.


title: Mid-Infrared observations of GRS 1915+105 and SS433

abstract:
  We have observed in the mid-infrared (4-18 micron) the counterpart of the
compact object GRS 1915+105, and the western jet of SS433. The images were
carried out with the ISOCAM infrared camera on board of the Infrared Space
Observatory (ISO). The mid-infrared photometry of GRS 1915+105 shows the
presence of an additional contribution besides the synchrotron emission. The 15
micron images of the large-scale western lobe of the SS433/W50 nebula are
compared to the radio and X-ray ones. They show infrared synchrotron emission
on the western edge of SS433/W50 lobe.