title: Do SNe Ia Provide Direct Evidence for Past Deceleration of the Universe?

abstract:
  Observations of SN 1997ff at z ~ 1.7 favor the accelerating Universe
interpretation of the high-redshift type Ia supernova data over simple models
of intergalactic dust or SN luminosity evolution. Taken at face-value, they
provide direct lines of evidence that the Universe was decelerating in the
past, an expected but untested feature of the current cosmological model. We
show that the strength of this conclusion depends upon the nature of the dark
energy causing the present acceleration. Only for a cosmological constant is
the SNe evidence definitive. Using a new test which is independent of the
contents of the Universe, we show that the SN data favor recent acceleration (z
< 0.5) and past deceleration (z > 0.5).


title:
Ionisation Structure in Accretion Shocks with a Composite Cooling
  Function

abstract:
  We have investigated the ionisation structure of the post-shock regions of
magnetic cataclysmic variables using an analytic density and temperature
structure model in which effects due to bremsstrahlung and cyclotron cooling
are considered. We find that in the majority of the shock-heated region where
H- and He-like lines of the heavy elements are emitted, the
collisional-ionisation and corona-condition approximations are justified. We
have calculated the line emissivity and ionisation profiles for Iron as a
function of height within the post-shock flow. For low-mass white dwarfs, line
emission takes place near the shock. For high-mass white dwarfs, most of the
line emission takes place in regions well below the shock and hence it is less
sensitive to the shock temperature. Thus, the line ratios are useful to
determine the white-dwarf masses for the low-mass white dwarfs, but the method
is less reliable when the white dwarfs are massive. Line spectra can, however,
be used to map the hydrodynamic structure of the post-shock accretion flow.


title: Thermal Limit Spectroscopy as a Goal for X-ray Astronomy

abstract:
  The R~300-1000 grating spectra from XMM-Newton and Chandra are a radical
advance, allowing spectroscopic physics techniques to be applied to X-ray
astronomy, revolutionizing a wide range of research. Ten years on these spectra
will be routine, and higher resolution will be needed. I propose ``Thermal
Limit Spectroscopy'' as the next natural goal for X-ray spectroscopy. This will
open up new physics: plasma physics, velocity widths, Doppler shifts, line
profiles, and absorption lines in photoionized plasmas. A resolution of
R=3000-10,000 is required, and the technology is within reach.


title:
Signal of Quark Deconfinement in Millisecond Pulsars and Reconfinement
  in Accreting X-ray Neutron Stars

abstract:
  Theoretically, the phase transition between the confined and deconfined
phases of quarks can have a remarkable effect on the spin properties of
millisecond pulsars and on the spin distribution of the population of x-ray
neutron stars in low-mass binaries. In the latter class of stars, the effect
has already been observed---a strong clustering in the population in a narrow
band of spins. The observed clustering cannot presently be uniquely assigned to
the phase transition as cause. However, there is another possible signal---not
so far observed---in millisecond pulsars that we also discuss. It would have
the same origin, and its discovery would tend to confirm the interpretation in
terms of a phase transition in the stellar core and that the high density phase
exists in the higer mass canonical neutron stars.


title: The Las Campanas Distant Cluster Survey - The Catalog

abstract:
  We present an optically-selected catalog of 1073 galaxy cluster and group
candidates at 0.3<z<1. These candidates are drawn from the Las Campanas Distant
Clusters Survey (LCDCS), a drift-scan imaging survey of a 130 square degree
strip of the southern sky. To construct this catalog we utilize a novel
detection process in which clusters are detected as positive surface brightness
fluctuations in the background sky. This approach permits us to find clusters
with significantly shallower data than other matched-filter methods that are
based upon number counts of resolved galaxies. Selection criteria for the
survey are fully automated so that this sample constitutes a well-defined,
homogeneous sample that can be used to address issues of cluster evolution and
cosmology. Estimated redshifts are derived for the entire sample, and an
observed correlation between surface brightness and velocity dispersion (sigma)
is used to estimate the limiting velocity dispersion of the survey as a
function of redshift. We find a net surface density of 15.5 candidates per
square degree at z_{est}>0.3, with a false-detection rate of 30%. At z=0.3 we
probe down to the level of poor groups while by z=0.8 we detect only the most
massive systems (sigma>1000 km/s). We also present a supplemental catalog of
112 candidates that fail one or more of the automated selection criteria, but
appear from visual inspection to be bona fide clusters.


title:
Seeing Galaxies though Thick and Thin. IV. The Superimposed Spiral
  Galaxies of NGC 3314

abstract:
  The superimposed pair of spiral galaxies NGC 3314 offers a unique opportunity
to trace the dust properties in a spiral galaxy. We analyze multicolor HST
imaging, supported by ground-based near-IR imaging and fiber-array spectroscopy
to measure dust extinction in the foreground Sc galaxy NGC 3314A, which is
backlit by the Sb system NGC 3314B. We can measure extinctions over a wide
range of galactocentric radii in the foreground galaxy, from 0.4-4.5 kpc. In
the outer disk, the extinction is strongly localized in discrete dust lanes.
These dust features show an extinction curve with a slope close to the Galactic
mean (R = 3.5+/-0.3) from 1.6 to 3.8 kpc, with no radial trend. Using the I-K
color of the background nucleus, we derive an extinction A(I) = 3.3 through the
disk at a projected distance 400 pc from the nucleus of NGC 3314A. The
extinction in even the inner disk of NGC 3314A is quite patchy, since
background H-alpha emission is detected from all parts of the system. Local
anticorrelations between foreground and background line emission demonstrate
that the dust is concentrated to star-forming regions, as has been found for
the blue light in several systems. Colors of dust lanes in NGC 3314A which are
projected only partially against the background disk indicate that the dust
scale height in the foreground disk is substantially smaller than that of the
stars.


title:
X-Ray Observations of Cluster Mergers: Cluster Morphologies and Their
  Implications

abstract:
  X-ray observations have played a key role in the study of substructure and
merging in galaxy clusters. I review the evidence for cluster substructure and
mergers obtained from X-ray observations with satellites that operated before
Chandra and XMM. Different techniques to study cluster mergers via X-ray
imaging and spectral data are discussed with an emphasis on the quantitative
analysis of cluster morphologies. I discuss the implications of measurements of
cluster morphologies for cosmology and the origin of radio halos.


title:
Forming stars on a viscous timescale: the key to exponential stellar
  profiles in disk galaxies?

abstract:
  We argue for implementing star formation on a viscous timescale in
hydrodynamical simulations of disk galaxy formation and evolution. Modelling
two-dimensional isolated disk galaxies with the Bhatnagar-Gross-Krook (BGK)
hydrocode, we verify the analytic claim of various authors that if the
characteristic timescale for star formation is equal to the viscous timescale
in disks, the resulting stellar profile is exponential on several scale lengths
whatever the initial gas and dark matter profile. This casts new light on both
numerical and semi-analytical disk formation simulations which either (a)
commence star formation in an already exponential gaseous disk, (b) begin a
disk simulation with conditions known to lead to an exponential, i.e. the
collapse of a spherically symmetric nearly uniform sphere of gas in solid body
rotation under the assumption of specific angular momentum conservation, or (c)
in simulations performed in a hierarchical context, tune their feedback
processes to delay disk formation until the dark matter halos are slowly
evolving and without much substructure so that the gas has the chance to
collapse under conditions known to give exponentials. In such models, star
formation follows a Schmidt-like law, which for lack of a suitable timescale,
resorts to an efficiency parameter. With star formation prescribed on a viscous
timescale however, we find gas and star fractions after $\sim$ 12 Gyr that are
consistent with observations without having to invoke any ``fudge factor'' for
star formation. Our results strongly suggest that despite our gap in
understanding the exact link between star formation and viscosity, the viscous
timescale is indeed the natural timescale for star formation.


title:
Infrared Space Observatories: How to Mitigate Zodiacal Dust
  Intereference

abstract:
  (Abridged) Out-of-the-ecliptic trajectories that are beneficial to space
observatories such as the Terrestrial Planet Finder and other potential mid-IR
missions are introduced. These novel trajectories result in significantly
reduced background noise from the zodiacal dust radiation and therefore allow a
reduction in telescope collecting area and hence cost. Two types of optimal
trajectories that are energetically feasible were derived using genetic
algorithms. These are highly inclined non-Keplerian heliocentric orbits. The
first optimal trajectory can use existing launch technology and the zodiacal
brightness for this trajectory is reduced by at least 50% for 60% of the
mission lifetime. The second optimal trajectory requires planned improvement in
launch technology but it renders a zodiacal cloud brightness reduction by at
least 70% for 82% of the mission lifetime. Heliocentric orbits at 5 AU have
been discussed because the zodiacal dust concentration is extremely low there
and the energy requirements to reach these trajectories are low if
gravitational assists can be used. Unfortunately such orbits are impractical
because of high cost, power source constraints (inability to use solar cells),
communication delays, and a long travel time before data return. Additionally,
the energy requirements to reach our low and high energy optimal trajectories
are respectively half as much and equivalent to a direct trip to 5AU with no
planetary gravitational assists.


title:
Star Formation, Supernovae Feedback and the Angular Momentum Problem in
  Numerical CDM Cosmogony: Half Way There?

abstract:
  We present a smoothed particle hydrodynamic (SPH) simulation that reproduces
a galaxy that is a moderate facsimile of those observed. The primary failing
point of previous simulations of disk formation, namely excessive transport of
angular momentum from gas to dark matter, is ameliorated by the inclusion of a
supernova feedback algorithm that allows energy to persist in the model ISM for
a period corresponding to the lifetime of stellar associations. The inclusion
of feedback leads to a disk at a redshift $z=0.52$, with a specific angular
momentum content within 10% of the value required to fit observations. An
exponential fit to the disk baryon surface density gives a scale length within
17% of the theoretical value. Runs without feedback, with or without star
formation, exhibit the drastic angular momentum transport observed elsewhere.


title: Empirical Constraints on Convective Core Overshoot

abstract:
  In stellar evolution calculations, the local pressure scale height is often
used to empirically constrain the amount of convective core overshoot. However,
this method brings unsatisfactory results for low-mass stars (< 1.1 -1.2 Mo for
Z= \Zs) which have very small cores or no convective core at all. Following
Roxburgh's integral constraint,we implemented an upper limit of overshoot
within the conventional method of alpha parameterization in order to remove an
overly large overshoot effect on low-mass stars. The erroneously large effect
of core overshoot due to the failure of alpha parameterization can be
effectively corrected by limiting the amount of overshoot to < 15 % of the core
radius. 15 % of the core radius would be a proper limit of overshoot which can
be implemented in a stellar evolution code for intermediate to low mass stars.
The temperature structure of the overshoot region does not play a crucial role
in stellar evolution since this transition region is very thin.


title: L-dwarf variability: Magnetic star spots or non-uniform clouds?

abstract:
  The recent discovery of photometric variations in L dwarfs has opened a
discussion on the cause of the variations. We argue against the existence of
magnetic spots in these atmospheres and favor the idea that non-uniform
condensate coverage (i.e. clouds) is responsible for the variations. The
magnetic Reynolds number (Rm) in the atmosphere of L dwarfs, which describes
how well the gas couples with the magnetic field, is too small (<<1) to support
the formation of magnetic spots. In constrast silicate and iron clouds form in
the photospheres of L dwarfs. Inhomogeneities in such cloud decks can plausibly
produce the observed photometric variations. Further evidence in support of
clouds is the tendency for variable L dwarfs to be bluer in J-Ks than the
average L dwarf of a given spectral type. This color effect is expected if
clear holes appear in an otherwise uniform cloud layer.


title: Temperature Structure and Chemical Abundances in Gaseous Nebulae

abstract:
  In this summary I review some results relative to: planetary nebulae, H II
regions, chemical evolution of galaxies, and the determination of the
primordial helium abundance. These results were presented during the symposium
"Ionized Gaseous Nebulae" which took place in Mexico City, Nov, 2000. To get a
more general perspective of this meeting I encourage you to read all the
contributions to the symposium proceedings.


title: Results from AMANDA

abstract:
  The AMANDA (Antarctic Muon And Neutrino Detector Array) detector, located at
the South Pole station, Antarctica, was recently expanded with the addition of
six new strings, completing the phase referred to as AMANDA-II. This detector
has been calibrated and in operation since January 2000. The first data
analyses are currently underway. In this report we present an update on the
results from the AMANDA-B10 detector, which operated during the austral winter
1997.


title: Is the X-ray variable source in M82 due to gravitational lensing ?

abstract:
  We explore the possibility of attributing the recent discovery of the hard
X-ray variable source CXOM82 J095550.2+694047 in M82 to the gravitational
magnification by an intervening stellar obeject along the line of sight as
microlens. The duration of the event ($>84$ days) allows us to set robust
constraints on the mass and location of the mircolensing object when combined
with the dynamical properties of the Galactic halo, the M82 and typical
globular clusters. Except for the extremely low probablity, the microlensing
magnification by MACHO in either the Galactic halo or the M82 halo is able to
explain the X-ray variability of CXOM82 J095550.2+694047. It is hoped that the
lensing hypothesis can be soon tested by the light curve measurement.


title: 1WGAJ1226.9+3332: a high redshift cluster discovered by Chandra

abstract:
  We report the detection of 1WGAJ1226.9+3332 as an arcminute scale extended
X-ray source with the Chandra X-ray Observatory. The Chandra observation and R
and K band imaging strongly support the identification of 1WGAJ1226.9+3332 as a
high redshift cluster of galaxies, most probably at z=0.85 +- 0.15, with an
inferred temperature kT =10 (+4;-3) keV and an unabsorbed luminosity (in a
r=120" aperture) of 1.3 (+0.16;-0.14) x 1e45 erg/s (0.5-10 keV). This
indication of redshift is also supported by the K and R band imaging, and is in
agreement with the spectroscopic redshift of 0.89 found by Ebeling et al.
(2001). The surface brightness profile is consistent with a beta-model with
beta=0.770 +- 0.025, rc=(18.1 +-0.9)" (corresponding to 101 +- 5 kpc at
z=0.89), and S(0)=1.02 +- 0.08 counts/arcsec**2. 1WGAJ1226.9+3332 was selected
as an extreme X-ray loud source with FX/FV>60; this selection method, thanks to
the large area sampled, seems to be a highly efficient method for finding
luminous high z clusters of galaxies.


title:
Multi-wavelength observations of serendipitous Chandra X-ray sources in
  the field of A2390

abstract:
  We present optical spectra and near-infrared imaging of a sample of
serendipitous X-ray sources detected in the field of Chandra observations of
the A2390 cluster of galaxies. The sources have 0.5-7 keV fluxes of 0.6-8 x
10^{-14} erg cm^{-2} s^{-1} and lie around the break in the 2-10 keV source
counts. They therefore are typical of sources dominating the X-ray Background
in that band. Twelve of the fifteen targets for which we have optical spectra
show emission lines, most of which have soft X-ray spectra. Including
photometric redshifts and published spectra we have redshifts for seventeen of
the sources, ranging from z~0.2 up to z~3 with a peak between z=1-2. Ten of our
sources have hard X-ray spectra indicating a spectral slope flatter than that
of a typical unabsorbed quasar. Two hard sources that are gravitationally
lensed by the foreground cluster are obscured quasars, with intrinsic 2-10 keV
luminosities of 0.2-3 x 10^{45} erg/s and absorbing columns of N_H>10^{23}
cm^{-2}. Both were detected by ISO, showing that the absorbed flux emerges in
the far-infrared.


title: Analysis of two quintessence models with SN Ia data

abstract:
  The supernovae Ia data are used to analyze two general exact solutions for
quintessence models. The best fit values for $\Omega_{m0}$ are smaller than in
the $\Lambda $-term model, but still acceptable. With present-day data, it is
not possible to discriminate among the various situations.


title:
Rotationally-induced asymmetry in the double-peak lightcurves of the
  bright EGRET pulsars?

abstract:
  Pulsed emission from the bright EGRET pulsars - Vela, Crab, and Geminga -
extends up to 10 GeV. The generic gamma lightcurve features two peaks separated
by 0.4 to 0.5 in phase. According to Thompson (2001) the lightcurve becomes
asymmetrical above 5 GeV in such a way that the trailing peak dominates over
the leading peak. We attempt to interpret this asymmetry within a
single-polar-cap scenario. We investigate the role of rotational effects on the
magnetic one-photon absorption rate in inducing such asymmetry. Our Monte Carlo
simulations of pulsar gamma-ray beams reveal that in the case of oblique
rotators with rotation periods of a few millisecond the rotational effects lead
to the asymmetry of the requested magnitude. However, the rotators relevant for
the bright EGRET pulsars must not have their inclination angles too large in
order to keep the two peaks at a separation of 0.4 in phase. With such a
condition imposed on the model rotators the resulting effects are rather minute
and can hardly be reconciled with the magnitude of the observed asymmetry.


title: On the Wilson-Bappu relationship in the Mg II k line

abstract:
  An investigation is carried out on the Wilson-Bappu effect in the Mg II k
line at 2796.34 A. The work is based on a selection of 230 stars observed by
both the IUE and HIPPARCOS satellites, covering a wide range of spectral type
and absolute visual magnitudes. The Wilson-Bappu relationship here provided is
considered to represent an improvement over previous recent results for the
considerably larger data sample used as well as for a proper consideration of
the measurement errors. No evidence has been found for a possible dependence of
the WB effect on stellar metallicity and effective temperature.


title: General Relativistic Effects on Magnetar Models of AXPs

abstract:
  General relativistic bending of light dramatically alters the variability of
X-ray emission originating from the surfaces of ultramagnetic neutron stars. We
construct radiative equilibrium models of such strongly magnetic cooling
neutron stars with light-element atmospheres to compute the angle- and
energy-dependent intensity emerging from their surfaces and find that the
beaming of surface emission is predominantly non-radial. The combination of
this radiation pattern with the calculations of light bending yields pulse
amplitudes that vary non-monotonically with the neutron star compactness and
the size of the emitting region. The significant suppression of the pulse
amplitude for large emitting areas provides very strong constraints on the
mechanisms that can simultaneously produce high periodic variability and X-ray
luminosity. We apply these results to the thermally-emitting magnetar models of
anomalous X-ray pulsars (AXPs), which are bright slowly-rotating X-ray sources
with large pulse amplitudes. We use the observed fluxes and pulse amplitudes
for all known AXPs and show that thermal emission from two antipodal regions on
their surfaces, as predicted by some magnetar models, is inconsistent with
these observed properties.


title: The Case Against Cold, Dark Chromospheres

abstract:
  Is the solar chromosphere always hot, with relatively small temperature
variations ($\delta T/T\sim0.1$); or is it cold most of the time, with
temperature fluctuations that reach $\delta T/T\sim 10$ at the top of the
chromosphere? Or, equivalently: Is the chromosphere heated continually, or only
for a few seconds once every three minutes? Two types of empirical model, one
essentially time independent and always hot, the other highly time dependent
and mostly cold, come to fundamentally different conclusions. This paper
analyzes the time-dependent model of the quiet, nonmagnetic chromosphere by
Carlsson & Stein (1994: CS94) and shows that it predicts deep absorption lines,
none of which is observed; intensity fluctuations in the Lyman continuum that
are much larger than observed; and time-averaged emission that falls far short
of the observed emission. The paper concludes that the solar chromosphere,
while time dependent, is never cold and dark. The same conclusion applies for
stellar chromospheres.
  A complete, time-dependent model of the nonmagnetic chromosphere must
describe two phenomena: (1) dynamics, like that modeled by CS94 for
chromospheric bright points but corrected for the geometrical properties of
shocks propagating in an upward-expanding channel; and (2) the energetically
more important general, sustained heating of the chromosphere, as described by
current time-independent empirical models, but modified in the upper
photosphere for the formation of molecular absorption lines of CO in a
dynamical medium. This model is always hot and, except for absorption features
caused by departures from local thermodynamic equilibrium, shows chromospheric
lines only in emission.


title: Optimal multihump filter for photometric redshifts

abstract:
  We propose a novel type filter for multicolor imaging to improve on the
photometric redshift estimation of galaxies. An extra filter - specific to a
certain photometric system - may be utilized with high efficiency. We present a
case study of the Hubble Space Telescope's Advanced Camera for Surveys and show
that one extra exposure could cut down the mean square error on photometric
redshifts by 34% over the z<1.3 redshift range.


title:
A K-band Selected Photometric Redshift Catalog in the HDF-S: Sampling
  the Rest-Frame V-Band to z=3

abstract:
  We present the first results from the Faint Infra-Red Extragalactic Survey
(FIRES) of the Hubble Deep Field South. Using a combination of deep near
infrared data obtained with ISAAC at the VLT with the WFPC2 HST data, we
construct a K-band selected sample of 136 galaxies with K(AB)<=23.5. We derive
zphot's using a newly developed technique which models the observed spectral
energy distribution with a linear combination of empirical galaxy templates.
Testing our zphot technique against spectroscopic redshifts in the HDF-N yields
dz/(1+z)~0.07 for z<6. We show that we can derive realistic error estimates in
zphot by combining the systematic uncertainties derived from the HDF-N with
errors in zphot which depend on the observed flux errors. The redshift
histogram of galaxies in the HDF-S shows distinct structure with a sharp peak
at z~0.5 and a broad enhancement at z~1-1.4. We find that 12% of our galaxies
with K(vega)<21 lie at z>=2. While this is higher than the fraction predicted
in Omega_M=1 hierarchical models of galaxy formation we find that published
predictions using pure luminosity evolution models produce too many bright
galaxies at redshifts greater than unity. Finally, we use our broad wavelength
coverage to measure the rest-frame UBV luminosities Lrest for z<=3. There is a
paucity of galaxies brighter than Lrest_V>=1.4e10 h^{-2}Lsun at z~1.5-2,
however, at z>2 we find very luminous galaxies with Lrest_V>=5e10 h^{-2}Lsun
(for Omega_M=0.3,Lambda=0.7, H_o=100 h km s^{-1}Mpc^{-1}). Local B-band
luminosity functions predict 0.1 galaxies in the redshift range 2<=z<=3.5 and
with Lrest_B>= 5e10 h^{-2}Lsun,B but we find 9. The discrepancy can be
explained if L*_B increases by a factor of 2.4-3.2 with respect to locally
determined values (abridged).


title:
Analogies, new paradigms and observational data as growing factors of
  Relativistic Astrophysics

abstract:
  Patterns in the scientific developments of Relativistic Astrophysics are
analyzed with special attention to the physics and astrophysics of Black Holes
and Gamma Ray Bursts.


title: Tests of a Structure for Quasars

abstract:
  The model I recently proposed for the structure of quasars (astro-ph/0008064)
claims to unify all the emission, absorption and reflection phenomenology of
quasars and AGN, and so is heavily overconstrained and readily tested.
  Here I concentrate on how the model has performed against tests since
publication - with many of the tests being reported at this meeting. I then
begin to explore how these and future tests can discriminate between this wind
model and 3 well-defined alternatives.


title: Cosmic Ray Acceleration by Magnetic Traps

abstract:
  Cosmic ray acceleration in turbulent interstellar medium is considered.
Turbulence is treated as ensemble of moving magnetic traps. We derive equations
for particle momentum distribution function that describes acceleration of
particles in this case. Rate of acceleration calculated is estimated for our
Galaxy and compared with ones given by other acceleration mechanisms.


title:
On Nonlinear Alfv\'en Waves Generated by Cosmic Ray Streaming
  Instability

abstract:
  Nonlinear damping of parallel propagating Alfv\'en waves in high-$\beta$
plasma is considered. Trapping of thermal ions and Coulomb collisions are taken
into account. Saturated damping rate is calculated. Applications are made for
cosmic ray propagation in the Galaxy.


title: Future Supernovae observations as a probe of dark energy

abstract:
  We study the potential impact of improved future supernovae data on our
understanding of the dark energy problem. We carefully examine the relative
utility of different fitting functions that can be used to parameterize the
dark energy models, and provide concrete reasons why a particular choice (based
on a parameterization of the equation of state) is better in almost all cases.
We discuss the details of a representative sample of dark energy models and
show how future supernova observations could distinguish among these. As a
specific example, we consider the proposed ``SNAP'' satellite which is planned
to observe around 2000 supernovae. We show how a SNAP-class data set taken
alone would be a powerful discriminator among a family of models that would be
approximated by a constant equation of state for the most recent epoch of
cosmic expansion. We show how this family includes most of the dark energy
models proposed so far. We then show how an independent measurement of
$\Omega_{\rm m}$ can allow SNAP to probe the evolution of the equation of state
as well, allowing further discrimination among a larger class of proposed dark
energy models. We study the impact of the satellite design parameters on this
method to distinguish the models and compare SNAP to alternative measurements.
We establish that if we exploit the full precision of SNAP it provides a very
powerful probe.


title:
On the possible existence of a self-regulating hydrodynamical process in
  slowly rotating stars II. Lithium Plateau in Halo Stars and Primordial
  Abundance

abstract:
  The lithium plateau observed in halo stars has long appeared as a paradox in
the general context of the lithium abundance behavior in stellar outer layers.
First, the plateau is flat, second, the lithium abundance dispersion is
extremely small. This seems in contradiction with the large lithium variations
observed in younger stars. It is also difficult to understand theoretically as
lithium nuclei are easily destroyed by nuclear reactions, and subject to
microscopic diffusion which, in the case of halo stars, should also lead to
depletion. Several ideas have been proposed to account for the lithium behavior
in halo stars. The most promising possibilities were rotational-induced mixing,
which could reduce lithium in the same way for all the stars, and mass-loss,
which could oppose the lithium settling. In both cases however, the parameters
should be tightly adjusted to prevent any dispersion in the final results.
Vauclair 1999 (paper I) pointed out that the mu-gradient terms which appear in
the computations of the meridional circulation velocity were not introduced in
previous computations of rotationally-induced mixing. This can lead to a
self-regulating process which reduces the efficiency of the meridional
circulation as well as the microscopic diffusion. Here we present numerical
computations of this process and its influence on the lithium abundance
variations in halo stars. We show that in slowly rotating stars, under some
conditions, lithium can be depleted by a factor of up to two with a dispersion
smaller than 0.1 dex in the middle part of the lithium plateau. We derive a
primordial lithium abundance of 2.5 +/- 0.1, consistent with the recent
determinations of D/H and 4He/H.


title:
Bayesian event reconstruction and background rejection in neutrino
  detectors

abstract:
  Several large volume, high energy neutrino detectors are in operation or in
the design stage. Upward going signal neutrino events must be separated from
large backgrounds of downgoing cosmic ray induced atmospheric muons. To this
end, a Bayesian extension of the traditional maximum likelihood reconstruction
method will be described. Further, it will be shown how signals can be
separated from backgrounds through integration of Bayesian posterior
probability densities.


title: Non-integrable galactic dynamics

abstract:
  Orbital and self-consistent dynamics of non-integrable galaxy models are
reviewed. Topics covered include torus construction; resonances; triaxial
systems with central singularities; mixing and collisionless relaxation; and
chaos in collisional systems.


title: Wide-band X-ray variability of GRS 1915+105 observed with BeppoSAX

abstract:
  The Galactic Microquasar GRS 1915+105 was observed by the Narrow Field
Instruments onboard BeppoSAX in two pointings during year 2000. We present the
preliminary results of wide-band study of the observed variability, carried out
also with the wavelet analysis.


title:
CCD Observations of the RR Lyrae Variables in the Globular Cluster NGC
  5897

abstract:
  CCD observations for 10 (6 previously known and 4 newly discovered) of the 11
RR Lyrae variables in NGC 5897 have been analysed. The period-luminosity and
period-amplitude plots indicate that the population of RR Lyrae variables in
NGC 5897 includes 3 fundamental mode, 4 first-overtone and 4 second-overtone
variables with mean periods 0.828, 0.459 and 0.343 days respectively. The
variables have properties that are similar to some of the Oosterhoff type II
variables in Omega Centauri. Two of the new variables (V11 and V13) were
previously considered to be possible non-variables that lie within or near the
instability strip on the horizontal branch; both have V amplitudes less than
0.2 mag. There is a chance that one or two of the variables (V10 and possibly
V3) might be anomalous Cepheids and not RR Lyrae stars.


title: A Model for Abundances in Metal-Poor Stars

abstract:
  It is argued that the abundances of r-process related elements in stars with
-3<[Fe/H]<-1 can be explained by the contributions of three sources. The
sources are: the first generations of very massive (>100 solar masses) stars
that are formed from Big Bang debris and are distinct from SNII, and two types
of SNII, the H and L events, which can occur only at [Fe/H]>-3. The H events
are of high frequency and produce dominantly heavy (A>130) r-elements but no Fe
(presumably leaving behind black holes). The L events are of low frequency and
produce Fe and dominantly light (A<130) r-elements (essentially none above Ba).
By using the observed abundances in two ultra-metal-poor stars and the solar
r-abundances, the initial or prompt inventory of elements produced by the first
generations of very massive stars and the yields of H and L events can be
determined. The abundances of a large number of elements in a star can then be
calculated from the model by using only the observed Eu and Fe abundances. To
match the model results and the observational data for stars with -3<[Fe/H]<-1
requires that the solar r-abundances for Sr, Y, Zr, and Ba must be
significantly increased from the standard values. Whether the solar
r-components of these elements used here to obtain a fit to the stellar data
can be reconciled with those obtained from solar abundances by subtracting the
s-components calculated from models is not clear.


title: Detecting Eccentric Globular Cluster Binaries with LISA

abstract:
  The energy carried in the gravitational wave signal from an eccentric binary
is spread across several harmonics of the orbital frequency. The inclusion of
the harmonics in the analysis of the gravitational wave signal increases the
signal-to-noise ratio of the detected signal for binaries whose fundamental
frequency is below the galactic confusion-limited noise cut-off. This can allow
for an improved angular resolution for sources whose orbital period is greater
than 2000 s. Globular cluster sources include possible binary black holes and
neutron stars which may have high eccentricities. Cluster dynamics may also
enhance the eccentricities of double white dwarf binaries and white
dwarf-neutron star binaries over the galactic sources. Preliminary results of
the expected signal-to-noise ratio for selected globular cluster binaries are
presented.


title: Detection of Gravitational Waves from Gravitationally Lensed Systems

abstract:
  It is accepted that quasars are powered by supermassive black holes (SMBH)
with masses in the range 10^6 - 10^9 solar masses in their cores. Occasionally,
compact stars can plunge into SMBH. In addition, there may be a number of such
compact objects circling the central SMBH in any given quasar. Both of these
processes are known to emit gravitational waves. LISA has the right sensitivity
to detect these waves. We show that gravitational lenses amplify the amplitudes
of these gravitational waves just as they amplify the observed light of
quasars. Given the geometry of the lensing configuration, this amplification
can be as large as a factor of 2 to 10, allowing the waves to be above the
detection threshold of LISA. We also show that waves from lensed quasars arrive
with time delays which are much larger than the coherence time of the
gravitational waves, making interference effects negligible. Thus, a simple
geometrical optics application leads to the lensing theory of gravitational
waves. In this context, we analyze and show in this preliminary analysis that
there is an enhancement of the amplitudes of gravitational radiation coming
from observed lensed quasars.


title:
Optical and Infrared Photometry of the Type Ia Supernovae 1999da,
  1999dk, 1999gp, 2000bk, and 2000ce

abstract:
  We present BVRI photometry of the Type Ia supernovae 1999da, 1999dk, 1999gp,
2000bk, and 2000ce, plus infrared photometry of three of these. These objects
exhibit the full range of decline rates of Type Ia supernovae. Combined optical
and infrared data show that families of V - infrared color curves can be used
to derive the host extinction (A_V) of these objects. Existing data do not yet
allow us to construct these loci for all color indices and supernova decline
rates, but the V-K color evolution is sufficiently uniform that it allows the
determination of host extinction over a wide range of supernova decline rates
to an accuracy of roughly +/- 0.1 mag. We introduce a new empirical parameter,
the mean I-band flux 20 to 40 days after maximum light, and show how it is
directly related to the decline rate.


title:
An X-Ray Point Source and Synchrotron Nebula Candidate in the Supernova
  Remnant G292.0+1.8

abstract:
  We present archival data from the Chandra X-Ray Observatory that reveal a
bright point source to the southeast of the center of the young supernova
remnant G292.0+1.8 that is coincident with the peak of highest radio surface
brightness. The mostly featureless spectrum of the point source at coordinates
(J2000) RA = 11 24 39.2, DEC = -59 16 19.8 is well fit by a three-parameter
absorbed model with one power-law and two blackbody components. We also argue
that the neutron star is surrounded by a synchrotron wind nebula based off of
the source's hard emission and high radio and X-ray luminosities, each
corresponding to a canonical wind nebula spin-down power, dE/dt ~ 10^36 erg/s.


title:
Discovering Long Wavelength Neutrino Oscillations in the Distorted
  Neutrino Spectrum of Galactic Supernova Remnants

abstract:
  We investigate the muon neutrino event rate in km$^3$ neutrino telescopes due
to a number of galactic supernova remnants expected on the basis of these
objects' known $\gamma$-ray signals. We evaluate the potential of these
neutrino signals to exhibit evidence of the sub-dominant neutrino oscillations
expected in various neutrino mixing schemes including pseudo-Dirac scenarios
and the Exact Parity Model. With ten years' data, neutrino signals from Sgr A
East should either discover or exclude neutrino oscillations governed by a
$\delta m^2$ parameter in the range $10^{-12}$ to $10^{-15}$ eV$^2$. Such a
capability is not available to terrestrial or solar system neutrino
experiments.


title: Test of primary model predictions by EAS size spectra

abstract:
  High statistical accuracy of experiments KASCADE and ANI allowed to obtain
approximations of primary energy spectra and elemental composition in the
"knee" region. Obtained results point out to the correctness of QGSJET
interaction model and 2-component model of primary cosmic ray origin up to 100
PeV energies.


title: Confusion limit due to galaxies: using SIRTF's Infrared Array Camera

abstract:
  Recent ISO-data has allowed for the first time observationally based
estimates for source confusion in mid-infrared surveys. We use the
extragalactic source counts from ISOCAM in conjunction with K-band counts to
predict the confusion due to galaxies in deep mid-IR observations. We
specifically concentrate on the near-future Space Infrared Telescope Facility
(SIRTF) mission, and calculate expected confusion for the Infrared Array Camera
(IRAC) onboard SIRTF. A defining scientific goal of the IRAC instrument will be
the study of high redshift galaxies using a deep, confusion limited wide field
survey at 3-10 microns. A deep survey can reach 3 $\mu$Jy sources with
reasonable confidence in the shorter wavelength IRAC bands. Truly confusion
limited images at 8 microns will be difficult to obtain due to practical time
constraints, unless infrared galaxies exhibit very strong evolution beyond the
deepest current observations. We find L^star galaxies to be detectable to
z=3-3.5 at 8 microns, which is slightly more pessimistic than found by Simpson
& Eisenhardt (1999).


title: Analyze of the star formation modeling algorithm in SPH code

abstract:
  The chemical and photometric evolution of star forming disk galaxies is
investigated. Numerical simulations of the complex gasdynamical flows are based
on our own coding of the Chemo - Dynamical Smoothed Particle Hydrodynamical (CD
- SPH) approach, which incorporates the effects of star formation. The
presented model describes well the time evolution of the basic dynamical,
chemical and photometric parameters of a disk galaxy similar to the Milky Way.
The metallicity, luminosity and colors obtained are typical for such disk
galaxies. During the calculations we made an extended test of the proposed SF
criteria. We find that the obtained results with different "gas" and "star"
particle numbers are not only qualitatively but also quantitatively similar.


title:
First Results of the EDELWEISS WIMP Search using a 320 g
  Heat-and-Ionization Ge Detector

abstract:
  The EDELWEISS collaboration has performed a direct search for WIMP dark
matter using a 320 g heat-and-ionization cryogenic Ge detector operated in a
low-background environment in the Laboratoire Souterrain de Modane. No nuclear
recoils are observed in the fiducial volume in the 30-200 keV energy range
during an effective exposure of 4.53 kg.days. Limits for the cross-section for
the spin-independent interaction of WIMPs and nucleons are set in the framework
of the Minimal Supersymmetric Standard Model (MSSM). The central value of the
signal reported by the experiment DAMA is excluded at 90% CL.


title:
The nebular spectra of the hypernova SN 1998bw and evidence for
  asymmetry

abstract:
  The nebular spectra of the energetic Type Ic supernova SN1998bw (hypernova)
are studied. The transition to the nebular phase occurred at an epoch of about
100 days after outburst, which is assumed to coincide with GRB980425. Early in
the nebular epoch the spectra show the characteristics of a typical SN Ic
spectrum, with strong lines of [OI], CaII and MgI], and lines of [FeII].
However, the [FeII] lines are unusually strong for a SN Ic. Also, lines of
different elements have different widths, indicating different expansion
velocities. In particular, iron appears to expand more rapidly than oxygen.
Furthermore, the [OI] nebular lines decline more slowly than the [FeII] ones,
signalling deposition of gamma-rays in a slowly-moving O-dominated region.
These facts suggest that the explosion was aspherical. The absence of [FeIII]
nebular lines can be understood if the ejecta are significantly clumped. A
schematic picture of what this very unusual stellar explosion may have looked
like is presented.


title: Dusty winds: I. Self-similar solutions

abstract:
  We address the dusty wind problem, from the point where dust formation has
been completed and outward. Given grain properties, both radiative transfer and
hydrodynamics components of the problem are fully defined by four additional
input parameters. The wind radiative emission and the shape of its velocity
profile are both independent of the actual magnitude of the velocity and are
determined by just three dimensionless free parameters. Of the three, only one
is always significant---for most of phase space the solution is described by a
set of similarity functions of a single independent variable, which can be
chosen as the overall optical depth at visual \tV. The self-similarity implies
general scaling relations among mass loss rate (\Mdot), luminosity ($L$) and
terminal velocity (\vf). Systems with different \Mdot, $L$ and \vf but the same
combination $\Mdot/L^{3/4}$ necessarily have also the same $\Mdot\vf/L$.
  ... Eliminating \tV produces $\vf^3 = A \Mdot(1 + B \Mdot^{4/3}/L)^{-1.5}$,
where $A$ and $B$ are coefficients that contain the only dependence of this
universal correlation on chemical composition. At a given $L$, the maximal
velocity of a dusty wind is $v\sub{max} \propto L^{1/4}$ attained at $\Mdot
\propto L^{3/4}$, with proportionality coefficients derived from $A$ and $B$.


title:
High-resolution O VI absorption line observations at 1.2 < z < 1.7 in
  the bright QSO HE 0515-4414

abstract:
  STIS Echelle observations at a resolution of 10 km/s and UVES/VLT
spectroscopy at a resolution of 7 km/s of the luminous QSO HE 0515-4414 (z_em =
1.73, B = 15.0) reveal four intervening O VI absorption systems in the redshift
range 1.2 < z_abs < 1.7 (1.38503, 1.41601, 1.60175, 1.67359). In addition two
associated systems at z = 1.69707 and z = 1.73585 are present. For the first
time high resolution observations allow to measure radial velocities of H I, C
IV and O VI simultaneously in several absorption systems (1.385, 1.674, 1.697)
with the result that significant velocity differences (up to 18 km/s) are
observed between H I and O VI, while smaller differences (up to 5 km/s) are
seen between C IV and O VI. We tentatively conclude that H I, O VI, and C IV
are not formed in the same volumes and that therefore implications on
ionization mechanisms are not possible from observed column density ratios O
VI/H I or O VI/C IV. The number density of O VI absorbers with W_rest > 25 mA
is dN/dz < 10, roughly a factor of 5 less than what has been found by Tripp at
al. (2000) at low redshift. An estimate of the cosmological mass-density of the
O VI-phase yields Omega_b(O VI) = 0.0003 h^{-1}_{75} for [O/H] = -1 and an
assumed ionization fraction O VI/O = 0.2. This corresponds to an increase by
roughly a factor of 15 between z = 1.5 (this work) and the value found by Tripp
et al. (2000) at z = 0.21, if the same oxygen abundance [O/H] = -1 is assumed.
Agreement with the simulations by Dave et al. (2001) can be obtained, if the
oxygen abundance increases by a factor of 3 over the same redshift interval.


title: The XMM-Newton $\Omega$ Project

abstract:
  The abundance of high-redshift galaxy clusters depends sensitively on the
matter density $\OmM$ and, to a lesser extent, on the cosmological constant
$\Lambda$. Measurements of this abundance therefore constrain these fundamental
cosmological parameters, and in a manner independent and complementary to other
methods, such as observations of the cosmic microwave background and distance
measurements. Cluster abundance is best measured by the X-ray temperature
function, as opposed to luminosity, because temperature and mass are tightly
correlated, as demonstrated by numerical simulations. Taking advantage of the
sensitivity of XMM-Newton, our Guaranteed Time program aims at measuring the
temperature of the highest redshift (z>0.4) SHARC clusters, with the ultimate
goal of constraining both $\OmM$ and $\Lambda$.


title:
Empirical constraints on alternative gravity theories from gravitational
  lensing

abstract:
  If it is hypothesised that there is no dark matter then some alternative
gravitational theory must take the place of general relativity (GR) on the
largest scales. Dynamical measurements can be used to investigate the nature of
such a theory, but only where there is visible matter. Gravitational lensing is
potentially a more powerful probe as it can be used to measure deflections far
from the deflector, and, for sufficiently large separations, allow it to be
treated as a point-mass. Microlensing within the local group does not yet
provide any interesting constraints, as only images formed close to the
deflectors are appreciably magnified, but stacking of multiple light-curves and
observations of microlensing on cosmological scales may be able to discriminate
between GR and non-dark matter theories. Galaxy-galaxy lensing is likely to be
an even more powerful probe of gravity, with the Sloan Digital Sky Survey
(SDSS) commissioning data used here to constrain the deflection law of galaxies
to be A(R) propto R^(0.1 +/- 0.1) for impact parameters in the range 50 kpc < R
< 1 Mpc. Together with observations of flat rotation curves, these results
imply that, in any gravitational theory, photons must experience (close to)
twice the deflection of massive particles moving at the speed of light (at
least on these physical scales). The full SDSS data-set will also be sensitive
to asymmetry in the lensing signal and variation of the deflection law with
galaxy type. A detection of either of these effects would represent an
independent confirmation that galaxies are dark matter-dominated; conversely
azimuthal symmetry of the shear signal would rule out the typically ellipsoidal
haloes predicted by most simulations of structure formation.


title: Gravitational lensing in modified Newtonian dynamics

abstract:
  Modified Newtonian dynamics (MOND) is an alternative theory of gravity that
aims to explain large-scale dynamics without recourse to any form of dark
matter. However the theory is incomplete, lacking a relativistic counterpart,
and so makes no definite predictions about gravitational lensing. The most
obvious form that MONDian lensing might take is that photons experience twice
the deflection of massive particles moving at the speed of light, as in general
relativity (GR). In such a theory there is no general thin-lens approximation
(although one can be made for spherically-symmetric deflectors), but the
three-dimensional acceleration of photons is in the same direction as the
relativistic acceleration would be. In regimes where the deflector can
reasonably be approximated as a single point-mass (specifically low-optical
depth microlensing and weak galaxy-galaxy lensing), this naive formulation is
consistent with observations. Forthcoming galaxy-galaxy lensing data and the
possibility of cosmological microlensing have the potential to distinguish
unambiguously between GR and MOND. Some tests can also be performed with
extended deflectors, for example by using surface brightness measurements of
lens galaxies to model quasar lenses, although the breakdown of the thin-lens
approximation allows an extra degree of freedom. Nonetheless, it seems unlikely
that simple ellipsoidal galaxies can explain both constraints. Further, the
low-density universe implied by MOND must be completely dominated by the
cosmological constant (to fit microwave background observations), and such
models are at odds with the low frequency of quasar lenses. These conflicts
might be resolved by a fully consistent relativistic extension to MOND; the
alternative is that MOND is not an accurate description of the universe.


title: Sub-milliarcsec-scale structure of the gravitational lens B1600+434

abstract:
  In the gravitational lens system B1600+434 the brighter image, A, is known to
show rapid variability which is not detected in the weaker image, B (Koopmans &
de Bruyn 2000). Since correlated variability is one of the fundamental
properties of gravitational lensing, it has been proposed that image A is
microlensed by stars in the halo of the lensing galaxy (Koopmans & de Bruyn
2000). We present VLBA observations of B1600+434 at 15 GHz with a resolution of
0.5 milliarcsec to determine the source structure at high spatial resolution.
The surface brightness of the images are significantly different, with image A
being more compact. This is in apparent contradiction with the required
property of gravitational lensing that surface brightness be preserved. Our
results suggest that both the lensed images may show two-sided elongation at
this resolution, a morphology which does not necessarily favour superluminal
motion. Instead these data may suggest that image B is scatter-broadened at the
lens so that its size is larger than that of A, and hence scintillates less
than image A.


title: Absorption Measurement of Hydrogen Molecules in the Early Universe

abstract:
  We investigate the observability of hydrogen molecules in absorption. The
absorption efficiency of the hydrogen molecules become comparable with or
larger than that of the dust grains in the metal-poor condition expected in the
early Universe. If we can use bright infrared continuum sources behind the
molecular gas clouds, the absorption measurement of the hydrogen molecules will
be an important technique to explore the primordial gas clouds that are
contracting into first-generation objects.


title:
Can the 33s pulsations observed from AE Aquarii be explained in terms of
  accretion onto the white dwarf surface?

abstract:
  The 33 s pulsing component observed from AE Aqr is frequently assumed to be
the result of accretion onto the surface of a rotating white dwarf. The
validity of this assumption is discussed in the present paper. I show that
under the conditions of interest the white dwarf is in the state of supersonic
propeller and the efficiency of plasma penetration into its magnetosphere is <
0.1%. This is too small to explain the observed luminosity of the pulsing
component. Moreover, I find that for the currently established value of the
angle between the magnetic and rotational axes of the white dwarf, the material
entering the magnetosphere at the boundary can never reach its surface by
flowing along the magnetic field lines. I conclude that the assumption about
the direct accretion onto the surface of the white dwarf in AE Aqr contradicts
the observational data obtained in the optical/UV and thus cannot be accepted.


title: Determination of time delay from the gravitational lens B1422+231

abstract:
  We present the radio light curves of lensed images of the gravitational lens
B1422+231. The observations have been carried out using the VLA at 8.4 and 15
GHz over a period of 197 days. We describe a method to estimate the time delay
from the observed light curves. Using this method, our cross-correlation
analysis shows that the time delay between images B and A is 1.5$\pm$1.4d,
between A and C is 7.6$\pm$2.5d, between B and C is 8.2$\pm$2.0d. When applied
to other lensed systems with measured time delays our new method gives
comparable results.


title: NewtonPlus: Approximate Relativity for Supernova Simulations

abstract:
  We propose an approximation to general relativity that captures the main
gravitational effects of dynamical importance in supernovae. The conceptual
link between this formalism and the Newtonian limit is such that it could
likely be implemented in existing multidimensional Newtonian gravitational
hydrodynamics codes employing a Poisson solver. As a test of the formalism's
utility, we display results for rapidly rotating (and therefore highly
deformed) neutron stars.


title: Supernova Ia: a Converging Delayed Detonation Wave

abstract:
  A model of a carbon-oxygen (C--O) presupernova core with an initial mass 1.33
M_\odot, an initial carbon mass fraction 0.27, and with an average mass
growth-rate 5 x 10^{-7} M_\odot/yr due to accretion in a binary system was
evolved from initial central density 10^9 g/cm^3, and temperature 2.05 x 10^8 K
through convective core formation and its subsequent expansion to the carbon
runaway at the center. The only thermonuclear reaction contained in the
equations of evolution and runaway was the carbon burning reaction 12C + 12C
with an energy release corresponding to the full transition of carbon and
oxygen (with the same rate as carbon) into 56Ni. As a parameter we take
\alpha_c - a ratio of a mixing length to the size of the convective zone. In
spite of the crude assumptions, we obtained a pattern of the runaway acceptable
for the supernova theory with the strong dependence of its duration on
\alpha_c. In the variants with large enough values of \alpha_c=4.0 x 10^{-3}
and 3.0 x 10^{-3} the fuel combustion occurred from the very beginning as a
prompt detonation. In the range of 2.0 x 10^{-3} >= \alpha_c >= 3.0 x 10^{-4}
the burning started as a deflagration with excitation of stellar pulsations
with growing amplitude. Eventually, the detonation set in, which was activated
near the surface layers of the presupernova (with m about 1.33 M_\odot) and
penetrated into the star down to the deflagration front. Excitation of model
pulsations and formation of a detonation front are described in detail for the
variant with \alpha_c=1.0 x 10^{-3}.


title:
Early Metal Enrichment by Pregalactic Outflows: II. Simulations of
  Blow-away

abstract:
  We present results from three-dimensional numerical simulations of the
dynamics of SN-driven bubbles as they propagate through and escape the grasp of
subgalactic halos with masses M ~ 10^8 Msun at redshift z=9. The hydrodynamic
simulations use a nested grid method to follow the evolution of explosive
multi-SN events operating on the characteristic timescale of a few x 10^7 yr,
the lifetime of massive stars. The results confirm that, if the star formation
efficiency of subgalactic halos is close to 10%, a significant fraction of the
halo gas will be lifted out of the potential well (`blow-away'), shock the
intergalactic medium, and pollute it with metal-enriched material, a scenario
recently advocated by Madau, Ferrara & Rees (2001). The volume filling factor
of the ejecta is close to unity. Depending on the stellar distribution, we find
that less than 30% of the available SN energy is converted into kinetic energy
of the blown away material, the remainder being radiated away. It appears that
mechanical feedback is less efficient than expected from simple energetic
arguments, as off-nuclear SN explosions drive inward-propagating shocks that
tend to collect and pile up cold gas in the central regions of the host halo.
Low-mass galaxies at early epochs may survive multiple SN events and continue
forming stars.


title: Constraining the window on sterile neutrinos as warm dark matter

abstract:
  Sterile neutrinos may be one of the best Warm Dark Matter candidates we have
today. Both lower and upper bounds on the mass of the sterile neutrino come
from astronomical observations. We show that the proper inclusion of the
neutrino momentum distribution reduces the allowed region to be 2.6 keV < m < 5
keV for the simplest models. A search for a spectral line with E=m/2 is thus
more interesting than ever before.


title:
A dozen colliding wind X-ray binaries in the star cluster R136 in the
  30Doradus region

abstract:
  We analyzed archival Chandra X-ray observations of the central portion of the
30 Doradus region in the Large Magellanic Cloud. The image contains 20 X-ray
point sources with luminosities between $5 \times 10^{32}$ and $2 \times
10^{35}$ erg s$^{-1}$ (0.2 -- 3.5 keV). A dozen sources have bright WN
Wolf-Rayet or spectral type O stars as optical counterparts. Nine of these are
within $\sim 3.4$pc of R136, the central star cluster of NGC2070. We derive an
empirical relation between the X-ray luminosity and the parameters for the
stellar wind of the optical counterpart. The relation gives good agreement for
known colliding wind binaries in the Milky Way Galaxy and for the identified
X-ray sources in NGC2070. We conclude that probably all identified X-ray
sources in NGC2070 are colliding wind binaries and that they are not associated
with compact objects. This conclusion contradicts Wang (1995) who argued, using
ROSAT data, that two earlier discovered X-ray sources are accreting black-hole
binaries. Five of the eighteen brightest stars in R136 are not visible in our
X-ray observations. These stars are either single, have low mass companions or
very wide orbits. The resulting binary fraction among early type stars is then
unusually high (at least 70%).


title: CO emission from high redshift

abstract:
  Future observations with ALMA will be able to detect star-forming primordial
gal axies, and perhaps even their dwarf spheroidal satellites, in CO emission
lines at redshifts approaching 10. These observations will compliment other
tools designed to study the dawn of galaxy formation, such as NGST and FIRST.


title: MHD consistent cellular automata (CA) models I: Basic features

abstract:
  A set-up is introduced which can be superimposed onto the existing solar
flare cellular automata (CA) models, and which specifies the interpretation of
the model's variables. It extends the CA models, yielding the magnetic field,
the current, and an approximation to the electric field, in a way that is
consistent with Maxwell's and the MHD equations. Applications to several solar
flare CA models during their natural state (self-organized criticality (SOC))
show, among others, that (1) the magnetic field exhibits characteristic
large-scale organization over the entire modeled volume; (2) the magnitude of
the current seems spatially dis-organized, with no obvious tendency towards
large-scale structures or even local organization; (3) bursts occur at sites
with increased current, and after a burst the current is relaxed; (4) by
estimating the energy released in individual bursts with the use of the current
as Ohmic dissipation, it turns out that the power-law distributions of the
released energy persist. The CA models, extended with the set-up, can thus be
considered as models for energy-release through current-dissipation. The
concepts of power-law loading and anisotropic events (bursts) in CA models are
generalized to 3--D vector-field models, and their effect on the magnetic field
topology is demonstrated.


title:
Gigamasers: the key to the dust-obscured star-formation history of the
  Universe?

abstract:
  We discuss the possibility of using OH and H2O gigamasers to trace the
redshift distribution of luminous, dust-obscured, star-forming galaxies. It has
long been thought that ultraluminous, interacting galaxies should host
gigamasers due to their vast pumping IR luminosity, the large column density of
molecules available to populate the maser states and the turbulent motion of
the gas in these dynamically complex systems which allows unsaturated maser
emission. OH masers may thus be well-suited to the redshift-blind detection of
ultraluminous and hyperluminous infrared galaxies (L_FIR >= 10^12 L_sun) such
as those uncovered by the SCUBA submillimetre camera. The bandwidth requirement
is low, <1 GHz for z=1-10 (lower still if additional redshift constraints are
available) and the dual-line 1665-/1667-MHz OH spectral signature can act as a
check on the reality of detections.


title: Gravitational Wave Emission From Core-Collapse of Massive Stars

abstract:
  We derive estimates for the characteristics of gravitational radiation from
stellar collapse, using recent models of the core-collapse of Chandrasekhar
mass white dwarfs (accretion induced collapse), core-collapse supernovae and
collapsars, and the collapse of very massive stars (~> 300 Msun). We study
gravitational-wave emission mechanisms using several estimation techniques,
including two-dimensional numerical computation of quadrupole wave emission,
estimates of bar-mode strength, estimates of r-mode emission, and estimates of
waves from black hole ringing. We also review the rate at which the relevant
collapses are believed to occur, which has a major impact on their relevance as
astrophysical sources. Although the latest supernova progenitor simulations
produce cores rotating much slower than those used in the past, we find that
bar-mode and r-mode instabilities from core-collapse supernovae remain among
the leading candidate sources for LIGO-II. Accretion induced collapse (AIC) of
a white dwarf could produce gravitational-wave signals similar to those from
core-collapse. In the models that we examine, such collapses are not unstable
to bar modes; we note that models recently examined by Liu and Lindblom, which
have slightly more angular momentum, are certainly unstable to bar formation.
Because AIC events are probably 1,000 times less common than core-collapse
supernovae, the typical AIC event will be much further away, and thus the
observed waves will be much weaker. In the most optimistic circumstances, we
find it may be possible to detect gravitational waves from the collapse of 300
Msun Population III stars.


title: New circumstellar magnetic field diagnostics

abstract:
  In this paper I will discuss new magnetic field diagnostics and
instrumentation for an area of astrophysics where magnetic field observations
have been difficult - circumstellar material. Such diagnostics would be
particularly relevant to star formation and evolution. Stellar photosphere
diagnostics include the Zeeman effect and atomic scattering diagnostics like
the Hanle Effect and atomic alignment. The Zeeman Effect is in general not
sensitive enough for the field strengths expected for circumstellar material,
and it is easily defeated by Doppler broadening in a dynamic envelope. Atomic
scattering diagnostics, pioneered recently for the Sun, are promising, but have
never been applied outside the Sun. For the study of unresolved envelopes, the
Hanle Effect may be applicable particularly in the ultraviolet. A medium
resolution UV spectropolarimeter, for instance, would serve for such studies.
Atomic alignment effects could utilize a ground-based, high signal-to-noise
spectropolarimeter, with profile information from high spectral resolution. I
will briefly mention several instrumentation development efforts in these
directions.


title:
Determination of Magnetic Fields in the Winds from Hot Stars Using the
  Hanle Effect

abstract:
  Resonance lines that are sensitive to the Hanle effect are prominent in the
UV spectra of early-type stars. To understand the differences from the solar
application of the Hanle effect, we focus on the formation of P-Cygni lines
both as a scattering process, and as one that allows a spectral isolation of
sectors in the wind. Some complications occuring in the solar case are found to
be absent for the Hanle effect for hot stars. Rocket observations from the Far
Ultraviolet SpectroPolarimeter (FUSP) experiment should allow for a
determination of fields in the dynamically interesting range from 1 to 300
Gauss.


title: Observable Effects of B fields on the Winds and Envelopes of Hot Stars

abstract:
  Magnetic fields on hot stars can produce a variety of interesting effects on
the velocity, density, and temperature structure in the winds from the stars.
The fields can produce a longitudinal dependence of the mass flux, which would
lead to cyclical variability such as that seen in optical and UV spectra of
many early-type stars. The fields can channel and spin-up the outflow, which
appears to be needed to explain the disk-like density enhancements around Ap
and Be stars. Magnetic confinement of hot gases can occur and be responsible
for the anomalously high EUV fluxes seen in B giants, and the anomalous high
ion X-ray line emission that is seen in recent CHANDRA observations. Special
attention is given to the reports at this meeting that A stars develop magnetic
Ap phenomenon only after about 30 percent of their main sequence lifetimes. A
similar delay occurs for the emission line Be stars. It is suggested that these
delays are related to the time it takes for fields to rise through the
sub-adiabatic envelope to the surface starting from the interface between the
convective-core and radiative-envelope where they are generated.


title: Influence of Expansion on Hierarchical Structure

abstract:
  We study a one dimensional model of gravitational instability in an
Einstein-de Sitter universe. Scaling in both space and time results in an
autonomous set of coupled Poisson-Vlasov equations for the field and phase
space density, and the $N$-body problem. Using dynamical simulation, we find
direct evidence of hierarchical clustering. A multi-fractal analysis reveals a
bifractal geometry similar to that observed in the distribution of galaxies. To
demonstrate the role of scaling, we compare the system to other one dimensional
models recently employed to study structure formation. Finally we show that the
model yields an estimate of the time of galaxy formation of the correct order.


title: Surface imaging of HD 199178 (V1794 Cygni)

abstract:
  We present surface temperature maps for the FK Comae-type star HD 199178
(V1794 Cygni) calculated from high resolution spectra obtained in 1994 and
1995. The spot pattern evolves, but all maps reveal a large cool spot remaining
nearly at the same high latitude. The main spot is 1200 -- 1600 K cooler than
the mean surface temperature. The observed slightly flat bottomed absorption
lines would usually be interpreted as evidence for a large cool polar spot. We
argue that antisolar surface differential rotation offers a better explanation
for the box like shape of the line profiles. However, we do not find conclusive
evidence for antisolar differential rotation and note that there are still
other possible explanations for the slightly flat bottomed line profiles.


title: Auto-correlation of Binary stars

abstract:
  Speckle interferometric technique is used to record a series of short
exposure images of several close binary stars with sub-arcsecond separation
through a narrow band filter centred at H$\alpha$ at the Cassegrain focus of
the 2.34 meter Vainu Bappu telescope (VBT), situated at Vainu Bappu Observatory
(VBO), Kavalur. The auto-correlation method is developed under Image Reduction
Analysis Facility (IRAF). Wiener filter is included in the programme to
eliminate spurious high frequency contributions; a few sets of data provide the
optimised results. The auto-correlated image of these stars gives the
separation of the binary components.


title: PTHalos: A fast method for generating mock galaxy distributions

abstract:
  Current models of galaxy formation applied to understanding the large-scale
structure of the universe have two parts. The first is an accurate solution of
the equations of motion for the dark matter due to gravitational clustering.
The second consists of making physically reasonable approximations to the
behavior of baryons inside dark matter halos. The first uses large,
computationally intensive, $n$-body simulations. We argue that because the
second step is, at least at present, uncertain, it is possible to obtain
similar galaxy distributions without solving the first step exactly. We
describe an algorithm which is several orders of magnitude faster than n-body
simulations, but which is, nevertheless, rather accurate. The algorithm
combines perturbation theory with virialized halo models of the nonlinear
density and velocity fields. For two- and three-point statistics the resulting
fields are exact on large scales, and rather accurate well into the nonlinear
regime, particularly for two-point statistics in real and redshift space. We
then show how to use this algorithm to generate mock galaxy distributions from
halo occupation numbers. As a first application, we show that it provides a
good description of the clustering of galaxies in the PSCz survey. We also
discuss applications to the estimation of non-Gaussian contributions to error
bars and covariance matrix of the power spectrum, in real and redshift space,
for galaxies and dark matter. The results for the latter show good agreement
with simulations, supporting the use of our method to constrain cosmological
parameters from upcoming galaxy surveys.


title:
GMRT Detection of HI 21 cm-line Absorption from the Peculiar Galaxy in
  Abell 2125

abstract:
  Using the recently completed Giant Meterwave Radio Telescope, we have
detected the HI 21 cm-line absorption from the peculiar galaxy C153 in the
galaxy cluster Abell 2125. The HI absorption is at a redshift of 0.2533, with a
peak optical depth of 0.36. The full width at half minimum of the absorption
line is 100 km/s. The estimated column density of atomic Hydrogen is
0.7e22(Ts/100K) per sq. cm. The HI absorption is redshifted by ~ 400 km/s
compared to the [OIII] emission line from this system. We attribute this to an
in-falling cold gas, or to an out-flowing ionised gas, or to a combination of
both as a consequence of tidal interactions of C153 with either a cluster
galaxy or the cluster potential.


title: The Star Cluster Systems of the Magellanic Clouds

abstract:
  The characteristics of the cluster systems of the Magellanic Clouds, as
inferred from integrated properties, are compared with those from individual
cluster studies and from the field population. The agreement is generally
satisfactory though in the case of the LMC, the lack of clusters older than ~3
Gyr is not reflected in the field population. The possible origin(s) for this
cluster ``age-gap'' are discussed. The SMC cluster age-metallicity relation is
also presented and discussed.


title: The Distance Scale of Planetary Nebulae

abstract:
  By collecting distances from the literature, a set of 73 planetary nebulae
with mean distances of high accuracy is derived. This sample is used for
recalibration of the mass-radius relationship, used by many statistical
distance methods. An attempt to correct for a statistical peculiarity, where
errors in the distances influences the mass--radius relationship by increasing
its slope, has been made for the first time. Distances to PNe in the Galactic
Bulge, derived by this new method as well as other statistical methods from the
last decade, are then used for the evaluation of these methods as distance
indicators. In order of achieving a Bulge sample that is free from outliers we
derive new criteria for Bulge membership. These criteria are much more
stringent than those used hitherto, in the sense that they also discriminate
against background objects. By splitting our Bulge sample in two, one with
optically thick (small) PNe and one with optically thin (large) PNe, we find
that our calibration is of higher accuracy than most other calibrations.
Differences between the two subsamples, we believe, are due to the
incompleteness of the Bulge sample, as well as the dominance of optical
diameters in the ``thin'' sample and radio diameters in the ``thick'' sample.
  Our final conclusion is that statistical methods give distances that are at
least as accurate as the ones obtained from many individual methods. Also, the
`long' distance scale of Galactic PNe is confirmed.


title: Anisotropy analysis of EAS data in the knee region

abstract:
  Based on MAKET-ANI EAS data the distributions of equatorial coordinates of
EAS core directions are obtained in the knee region. Anisotropy of primary
cosmic rays is displayed only by declination equatorial coordinates (20+/-3
degrees) at primary energies more than 5-10 PeV. The fraction of anisotropic
component turns out ~10% in the knee region.


title:
Gamma-Ray Line Emission from Superbubbles in the Interstellar Medium:
  The Cygnus Region

abstract:
  The star forming process in the Milky Way is non-uniform in time and space.
The scale of star forming regions ranges from groups within a few pc to large
segments of spiral arms with linear dimension of order kpc. When many stars
form in a relatively small volume over a short duration, a localized starburst
ensues. The energetic impact of such a burst of star formation can severely
affect the dynamic structure of the gaseous disk. Stellar winds and supernova
explosions drive an expanding superbubble, whose size eventually exceeds the
scale height of the disk and thus drives a disk-wind blowing metal enriched gas
into the halo. We discuss the basic scenario of superbubble evolution,
emphasizing the associated gamma-ray line signatures. In particular, we discuss
nuclear line emission from 26Al and 60Fe in the Cygnus region.


title:
Maser and thermal methanol emission in the millimeter wave range: new
  masers at 1.3 mm and 2.8 mm

abstract:
  Results of a survey of Galactic star-forming regions in the lines of methanol
8_{-1}-7_0E at 229.8 GHz, 3_{-2}-4_{-1}E at 230.0 GHz, 0_0-1_{-1}E at 108.9
GHz, and a series of methanol lines J_1-J_0E near 165 GHz are presented. Two
masers, DR 21(OH) and DR 21West, and two maser candidates, L 379IRS3 and NGC
6334I(N), as well as 16 thermal sources are found at 229.8 GHz. This is the
first detection of methanol masers at a wavelength as short as 1 mm. At 108.9
GHz, masers were found towards G345.01+1.79 and probably, towards M 8E. Thermal
emission is found towards 28 objects. Only thermal emission was found at 165
and 230.0 GHz (20 and 7 sources, respectively). The masers at 229.8 GHz belong
to class I, whereas those at 108.9 GHz belong to class II, according to the
classification by Menten (1991). The masers in DR 21(OH) and DR 21West can be
roughly fitted by models with the gas kinetic temperature of the order of 50K.
The detection of the 108.9 GHz masers towards G345.01+1.79 and M 8E may
indicate on a specific geometry of these objects. The combination of the
existence of the class II J_0-J_{-1}E masers towards W 3(OH), G345.01+1.79, W
48, and Cep A and our non-detection of the 3_{-2}-4_{-1}E and J_1-J_0E lines is
an evidence that the class II masers in these objects are pumped by the
radiation of hot dust rather than by that of UC HII-regions.


title:
A sample of 6C radio sources designed to find objects at redshift > 4:
  II --- spectrophotometry and emission line properties

abstract:
  (Abridged) This is the second in a series of three papers which present and
interpret basic observational data on the 6C* 151-MHz radio sample: a
low-frequency selected sample which exploits filtering criteria based on radio
properties (steep spectral index and small angular size) to find radio sources
at redshift z > 4 within a 0.133sr patch of sky. We present results of a
programme of optical spectroscopy which has yielded redshifts in the range 0.5
< z < 4.4 for the 29 sources in the sample, all but six of which are secure. We
find that the fil tering criteria used for 6C* are very effective in excluding
the low-redshift, low-luminosity radio sources: the median redshift of 6C* is
z~1.9 compared to z~1.1 for a complete sample matched in 151-MHz flux density.
By combining the emission-line dataset for the 6C* radio sources with those for
the 3CRR, 6CE and 7CRS samples we establish that z > 1.75 radio galaxies follow
a rough proportionality between Lyalpha- and 151 MHz-luminosity which, like
similar correlations seen in samples of lower-redshift radio sources, are
indicative of a primary link between the power in the source of the
photoionising photons (most likely a hidden quasar nucleus) and the power
carried by the radio jets. We argue that radio sources modify their
environments and that the range of emission-line properties seen is determined
more by the range of source age than by the range in ambient environment. This
is in accord with the idea that all high-redshift, high-luminosity radio
sources are triggered in similar environments, presumably recently collapsed
massive structures.


title: Modelling the radio to X-ray SED of galaxies

abstract:
  We present our model to interpret the SED of galaxies. The model for the UV
to sub-mm SED is already well established (Silva et al 1998). We remind here
its main features and show some applications. Recently we have extended the
model to the radio range (Bressan et al 2001), and we have started to include
the X-ray emission from the stellar component.


title:
Predicting Metallicities and Color Distributions for Secondary GCs
  Forming in Spiral Galaxy Mergers at Various Redshifts

abstract:
  In a 1$^{\rm st}$ step I present results from our new set of evolutionary
synthesis models for Simple (= single burst) Stellar Populations ({\bf SSP}s)
of various metallicities, and in a 2$^{\rm nd}$ step I combine these results
with the information we have about the redshift evolution of spiral galaxies'
ISM abundances. The aim is to provide a grid of color and luminosity
distibutions of any secondary GC population formed at some time in the past in
those mergers for comparison with observations.


title:
A sample of 6C radio sources designed to find objects at redshift > 4:
  III --- imaging and the radio galaxy K-z relation

abstract:
  In this paper, the third and final of a series, we present complete K-band
imaging and some complementary I-band imaging of the filtered 6C* sample. We
find no systematic differences between the K-z relation of 6C* radio galaxies
and those from complete samples, so the near-infrared properties of luminous
radio galaxies are not obviously biased by the additional 6C* radio selection
criteria (steep spectral index and small angular size). The 6C* K-z data
significantly improve delineation of the K-z relation for radio galaxies at
high-redshift (z >2). Accounting for non-stellar contamination, and for
correlations between radio luminosity and stellar mass, we find little support
for previous claims that the underlying scatter in the stellar luminosity of
radio galaxies increases significantly at z >2. In a particular spatially-flat
universe with a cosmological constant, the most luminous radio sources appear
to be associated with galaxies with a luminosity distribution with a high mean
(~5 Lstar), and a low dispersion (sigma ~ 0.5 mag) which formed their stars at
epochs corresponding to z >~2.5. This result is in line with recent sub-mm
studies of high-redshift radio galaxies and the inferred ages of extremely red
objects from faint radio samples.


title: SN1998bw/GRB980425 and Radio Supernovae

abstract:
  The unusual supernova SN1998bw, which is thought to be related to the
gamma-ray burster GRB980425, is a possible link between the two classes of
objects. Analyzing the extensive radio emission data avaliable for SN1998bw, we
are able to describe its time evolution within the well established framework
available for the analysis of radio emission from supernovae. This then allows
description of a number of physical properties of the object. The radio
emission can best be explained as interaction of a mildly relativistic (Gamma
about 1.6) shock with a dense pre-explosion stellar wind established
circumstellar medium (CSM) which is highly structured both azimuthally, in
clumps or filaments, and radially, with two observed density enhancements
separated by about 3e17 cm. With assumptions as to pre-explosion stellar wind
conditions, it is possible to estimate that the progenitor to SN 1998bw had a
mass loss rate of about 3.5e-5 solar masses per yr with at least two
approximately 30% increases in mass-loss rate; the most recent extending from
about 1,600 - 4,700 yr before explosion and the oldest known having occurred,
with possibly comparable length, about 12,000 yr before explosion. Because of
its unusual characteristics for a Type Ib/c SN, the relation of SN1998bw to
GRB980425 is strengthened with consequent improvement in our understanding of
these poorly understood objects.


title: The Detection of New Methanol Masers in the 5_{-1}-4_0E Line

abstract:
  Fifty-one objects in the 5_{-1}-4_0E methanol line at 84.5 GHz were detected
during a survey of Class I maser sources. Narrow maser features were found in
17 of these. Broad quasi-thermal lines were detected towards other sources. One
of the objects with narrow features, the young bipolar outflow L 1157 was also
observed in the 8_0-7_1A+ line at 95.2 GHz; a narrow line was detected at this
frequency. Analysis showed that the broad lines are usually inverted. The
quasi-thermal profiles imply that the line opacities are not larger than
several units. These results confirm the plausibility of models in which
compact Class I masers appear in extended sources as a result of an appropriate
velocity field.
  Measurements of linear polarization at 84.5 GHz in 13 sources were made. No
polarization was found except a tentative detection of a weak polarization in M
8E.


title: Tachocline Confinement by an Oscillatory Magnetic Field

abstract:
  Helioseismic measurements indicate that the solar tachocline is very thin,
its full thickness not exceeding 4% of the solar radius. The mechanism that
inhibits differential rotation to propagate from the convective zone to deeper
into the radiative zone is not known, though several propositions have been
made. In this paper we demonstrate by numerical models and analytic estimates
that the tachocline can be confined to its observed thickness by a poloidal
magnetic field B_p of about one kilogauss, penetrating below the convective
zone and oscillating with a period of 22 years, if the tachocline region is
turbulent with a diffusivity of eta 10^10 cm^2/s (for a turbulent magnetic
Prandtl number of unity). We also show that a similar confinement may be
produced for other pairs of the parameter values (B_p, eta). The assumption of
the dynamo field penetrating into the tachocline is consistent whenever
eta>10^9 cm^2/s.


title:
Memory Effects in Turbulent Dynamo: Generation and Propagation of Large
  Scale Magnetic Field

abstract:
  We are concerned with large scale magnetic field dynamo generation and
propagation of magnetic fronts in turbulent electrically conducting fluids. An
effective equation for the large scale magnetic field is developed here that
takes into account the finite correlation times of the turbulent flow. This
equation involves the memory integrals corresponding to the dynamo source term
describing the alpha-effect and turbulent transport of magnetic field. We find
that the memory effects can drastically change the dynamo growth rate, in
particular, non-local turbulent transport might increase the growth rate
several times compared to the conventional gradient transport expression.
Moreover, the integral turbulent transport term leads to a large decrease of
the speed of magnetic front propagation.


title:
The Cosmological Constant and Quintessence from a Correlation Function
  Comoving Fine Feature in the 2dF Quasar Redshift Survey

abstract:
  Detections of local maxima in the density perturbation spectrum at
characteristic comoving scales L~100-200h^{-1}Mpc have previously been claimed.
Here, this cosmic standard ruler is sought in the ``10K'' release of the 2dF
QSO Redshift Survey (2QZ-10K), by estimating the comoving, spatial correlation
functions \xi(r) of the three-dimensional distribution of the N=2378 quasars in
the most completely observed and ``covered'' sky regions, over the three
redshift ranges 0.6 < z < 1.1, 1.1 < z < 1.6 and 1.6 < z < 2.2. Because of the
selection method of the survey and sparsity of the data, the analysis was done
conservatively to avoid non-cosmological artefacts.
  (i) Avoiding 'a priori' estimates of the length scales of features, local
maxima in \xi(r) are found in all three redshift ranges. The requirement that a
local maximum be present in all three redshift ranges at a fixed comoving
length scale implies strong, purely geometric constraints on the local
cosmological parameters. The length scale of the local maximum common to the
three redshift ranges is 2L= (244\pm17)h^{-1}Mpc.
  (ii) For a standard FLRW model, the matter density \Omm and cosmological
constant \Omega_\Lambda are constrained to \Omm= 0.25\pm0.10,
\Omega_\Lambda=0.65\pm0.25 (68% confidence), \Omm= 0.25\pm0.15,
\Omega_\Lambda=0.60\pm0.35 (95%), respectively, *from the 2QZ-10K alone*.
Independently of the SNe Ia data, the zero cosmological constant model
(\Omega_\Lambda=0) is rejected at the 99.7% confidence level.
  (iii) For an effective quintessence (w_Q) model and zero curvature, w_Q<-0.5
(68%), w_Q<-0.35 (95%) are found, again *from the 2QZ-10K alone*.


title: Field Stars, Open Clusters, and the Galactic Abundance Gradient

abstract:
  The effects of the orbital diffusion of stars and clusters on the galactic
abundance gradient have been modelled. For a single generation of field stars,
the results confirm previous analyses based upon the assumption of a linear
gradient with galactocentric distance. Though the dispersion in metallicity at
a given radius grows with time, the underlying slope across the disk remains
unchanged. For a disk dominated by a discontinuity in [Fe/H] beyond the solar
circle, but no gradient within the inner or outer disk, a gradient is derived
for any sample whose galactocentric baseline overlaps the discontinuity. The
consequence of orbital diffusion is to shift the observable edge of the
transition in [Fe/H] to smaller galactocentric distance. In contrast, star
clusters of a single generation evaporate so quickly that the small surviving
sample of the oldest clusters is statistically insufficient to define any but a
linear gradient. Inclusion of multiple generations of stars and clusters with a
plausible age-metallicity relation enhances these patterns by expanding the
metallicity range at a given galactocentric distance through the inclusion of
stars with a wide range in both age and galactocentric origin. For field stars,
the metallicity distribution of stars in the solar neighborhood is virtually
indistinguishable for the two cases modelled. Because ages, abundances, and
distances can be reliably determined for clusters and any sample of clusters is
invariably dominated by clusters formed over the last 2 Gyrs, the cluster
population offers a means for finding detailed structure within the recent
galactic abundance gradient. Using clusters to extend the galactocentric
baseline would supply an additional critical test of the discontinuity.


title: Cluster Mergers and Diffuse Radio Emission in Abell 2256 and Abell 754

abstract:
  We present deep VLA observations of the galaxy clusters Abell 2256 and Abell
754, both of which appear to be in the violent stage of major cluster merger
events. The complex nature of Abell 2256 is revealed through radio images
which, in addition to the head-tail galaxies, show two extended, irregular, and
sharp-edged regions of diffuse radio emission at the cluster periphery (so
called radio relics), and a large-scale diffuse radio halo located in the
central regions of the cluster. Polarimetry of the A2256 cluster relics reveals
large-scale ordered magnetic fields which appear to trace the bright filaments
in the relics. The polarization fraction across the relics ranges from 20% -
40% with the majority of the relics polarized above the 30% level. At the
sensitivity of our current observations we place an upper limit of 20% on the
polarization of the radio halo. Low frequency VLA observations of Abell 754
reveal extended, diffuse radio (halo) emission in the cluster core region as
well as steep spectrum emission in the cluster periphery. The location,
morphology, and spectral index of the peripheral emission are consistent with
the properties of radio relics. The X-ray evidence of the ongoing mergers in
both clusters, together with the polarization properties of A2256's radio
relics supports recent suggestions of a merger-induced origin of the relic
emission. Deciphering the complex radio properties of these clusters may thus
provide the key to understanding the dynamical history of the systems.


title: A multiscale regularized restoration algorithm for XMM-Newton data

abstract:
  We introduce a new multiscale restoration algorithm for images with few
photons counts and its use for denoising XMM data. We use a thresholding of the
wavelet space so as to remove the noise contribution at each scale while
preserving the multiscale information of the signal. Contrary to other
algorithms the signal restoration process is the same whatever the signal to
noise ratio is. Thresholds according to a Poisson noise process are indeed
computed analytically at each scale thanks to the use of the unnormalized Haar
wavelet transform. Promising preliminary results are obtained on X-ray data for
Abell 2163 with the computation of a temperature map.


title: Multi-wavelength observations of serendipitous Chandra sources

abstract:
  We describe progress in a programme to study a sample of sources typical of
those which contribute a large fraction of the hard X-ray background. The
sources are selected from the fields of approximately 10 ks Chandra cluster
observations with follow-up in the near-infrared and optical. The X-ray data
indicate that many of these are powerful, obscured sources. Two hard objects
which are lensed by the cluster are good candidates for X-ray type-2 quasars,
with luminosities of the order 10^{44}-10^{45} erg s^{-1} and obscuring column
densities of the order 10^{23} cm^{-2}. We find that the sources are bright in
the infra-red (K typically 17-18). From Keck optical spectra and photometric
redshifts, we find that the host galaxies are consistent with being early-type,
massive hosts at redshifts ranging from 0.2 to 3, with median redshift
approximately 1.5. The two obscured quasars also have mid-infrared detections
and 850-micron upper-limits implying that the surrounding dust is at
warm-to-hot temperatures (T of the order of 1000 K).


title:
The Rapid Burster in Liller 1: the Chandra X-ray Position and a Search
  for an IR Counterpart

abstract:
  Despite the unique X-ray behavior of the compact bursting X-ray source
MXB1730-335, the "Rapid Burster" (RB) in the highly reddened globular cluster
Liller 1, to date there has been no known optical/IR counterpart for the
object, no precise astrometric solution that correlates X-ray, radio, and
optical positions and thus restricts the number of possible candidates, nor
even published IR images of the field. We solve a previous radio/X-ray
positional discrepancy, presenting the results of precise Chandra X-ray
imaging, which definitively show that the radio source is positionally aligned
with MXB1730-335. At the same time, we have detected three additional low
luminosity (Lx~10e34 erg/s) X-ray sources within two core radii, which are
possibly quiescent low-mass X-ray binaries. We present both ground-based and
Hubble Space Telescope infrared imaging of the field (in quiescent and bursting
X-ray states of the RB), together with the necessary astrometric solution to
overlay the radio/X-ray source positions. Even at HST resolution, the RB field
is very complex and there are multiple candidates. No object of unusual color,
or of substantial variability in quiescent versus active or burst versus
non-burst states, is identified. Further, more sensitive HST/NICMOS and/or
ground-based adaptive-optics observations are needed to confidently identify
the proper counterpart. In the case of the RB, uncertain but plausible
calculations on the effects of the burst on the binary companion indicate that
detection of a variable candidate should be feasible.


title: A Comprehensive Study of Neutron Star Retention in Globular Clusters

abstract:
  (abridged) Observations of very high speeds among pulsars in the Galactic
disk present a puzzle regarding neutron stars in globular clusters. The
inferred characteristic speed of single pulsars in the Galaxy is $\sim 5-10$
times as large as the central escape speed from the most massive globular
clusters. It is then reasonable to ask why any pulsars are seen in globular
clusters, whereas, in fact, quite a large number have been detected and as many
as $\sim 1000$ are thought to be present in some of the richest clusters.
  We use a Monte Carlo approach to generate a population of massive primordial
binaries. If we utilize the convention assumptions regarding mass transfer and
neutron star kicks, we find that < 5% of the neutron stars initially formed in
a massive cluster can be retained. We suggest that this fraction is too low to
account for what is observed, and we speculate on possible alternative
solutions to the retention problem.


title:
An observability study for the tentatively identified 3EG sources likely
  to be detected by the next-generation Cherenkov telescopes

abstract:
  We present a compilation of data on the 22 tentatively identified gamma-ray
sources from the Third EGRET Catalog which may be detected by the
next-generation imaging atmospheric Cherenkov telescopes.


title:
The Cold Big-Bang Cosmology as a Counter-example to Several Anthropic
  Arguments

abstract:
  A general Friedmann big-bang cosmology can be specified by fixing a
half-dozen cosmological parameters such as the photon-to-baryon ratio Eta, the
cosmological constant Lambda, the curvature scale R, and the amplitude Q of
(assumed scale-invariant) primordial density fluctuations. There is currently
no established theory as to why these parameters take the particular values we
deduce from observations. This has led to proposed `anthropic' explanations for
the observed value of each parameter, as the only value capable of generating a
universe that can host intelligent life. In this paper, I explicitly show that
the requirement that the universe generates sun-like stars with planets does
not fix these parameters, by developing a class of cosmologies (based on the
classical `cold big-bang' model) in which some or all of the cosmological
parameters differ by orders of magnitude from the values they assume in the
standard hot big-bang cosmology, without precluding in any obvious way the
existence of intelligent life. I also give a careful discussion of the
structure and context of anthropic arguments in cosmology, and point out some
implications of the cold big-bang model's existence for anthropic arguments
concerning specific parameters.


title: Interplay Between Gravity and Quintessence: A Set of New GR Solutions

abstract:
  A set of new exact analytical General Relativity (GR) solutions with
time-dependent and spatially inhomogeneous quintessence demonstrate 1) a static
non-empty space-time with a horizon-type singular surface; 2) time-dependent
spatially homogeneous `spheres' which are completely different in geometry from
the Friedmann isotropic models; 3) infinitely strong anti-gravity at a `true'
singularity where the density is infinitely large. It is also found that 4) the
GR solutions allow for an extreme `density-free' form of energy that can
generate regular space-time geometries.


title: Constraining Cosmological Parameters Based on Relative Galaxy Ages

abstract:
  We propose to use relative galaxy ages as a means of constraining
cosmological parameters. By measuring the age difference between two ensembles
of old galaxies at somewhat different redshifts, one could determine the
derivative of redshift with respect to cosmic time, dz/dt. At high redshifts,
z=1-2, this measurement would constrain the equation-of-state of the dark
energy, while at low redshifts, z< 0.2, it would determine the Hubble constant,
H_0. The selected galaxies need to be passively-evolving on a time much longer
than their age difference.


title: BIMA Observations of Linear Polarization in Sagittarius A* at 112 GHz

abstract:
  We report here BIMA array observations of linear polarization in Sagittarius
A*, the compact radio source in the Galactic Center. These observations had a
resolution of 20 arcsec x 5 arcsec oriented North-South. We do not detect
linear or circular polarization at a level of 1.8% (1-sigma) at 112 GHz. This
puts a new constraint on models that show a sharp change in linear polarization
fraction at 100 GHz.