title: Probing the First Stars with Hydrogen and Helium Recombination Emission

abstract:
  Unusual patterns of recombination emission from gas ionized by metal-free
stars may distinguish early star-forming galaxies from their present-day
counterparts. This pattern arises from the harder ionizing spectrum expected
from metal-free stars, which strongly enhances the strength of He II
recombination lines. Our calculations indicate that line fluxes of He II 1640
and 4686 are sufficiently large to be detected by narrowband and spectroscopic
searches for high-redshift emission-line sources at redshift z ~ 5 using
current instruments. An unknown fraction of Lya emitters may harbor
low-metallicity or metal-free stars. As the predicted He II 1640 flux is
comparable to and may exceed hydrogen Lya, searches for high-redshift galaxies
should consider He II recombination lines as possible identifications for
single emission lines in observed spectra. Spectra of metal-free stars may show
both H I and He II emission lines, improving the constraints on their redshift
and identification. We assess the considerable uncertainties that affect our
expectations for the detection and identification of true first-generation
stars with present search techniques, including the role of stellar mass loss
in spectral evolution and the confusion of ionization by primordial stellar
sources and AGN in the early universe.


title:
Assisted stellar suicide: the wind-driven evolution of the recurrent
  nova T Pyxidis

abstract:
  We show that the extremely high luminosity of the short-period recurrent nova
T Pyx in quiescence can be understood if this system is a wind-driven supersoft
x-ray source (SSS). In this scenario, a strong, radiation-induced wind is
excited from the secondary star and accelerates the binary evolution. The
accretion rate is therefore much higher than in an ordinary cataclysmic binary
at the same orbital period, as is the luminosity of the white dwarf primary. In
the steady state, the enhanced luminosity is just sufficient to maintain the
wind from the secondary. The accretion rate and luminosity predicted by the
wind-driven model for T Pyx are in good agreement with the observational
evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's
status as a SSS.
  T Pyx's lifetime in the wind-driven state is on the order of a million years.
Its ultimate fate is not certain, but the system may very well end up
destroying itself, either via the complete evaporation of the secondary star,
or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit.
Thus either the primary, the secondary, or both may currently be committing
assisted stellar suicide.


title:
The Be/X-ray binary LS 992/RX J0812.4-3114: physical parameters and
  long-term variability

abstract:
  We present the first long-term optical and infrared study of the optical
counterpart to the source RX J0812.4-3114, an X-ray pulsar with a Be type
companion. During the period covered by the observations the profile of some
Balmer lines changed from absorption to emission and back again to absorption.
Contemporaneously, the infrared magnitudes varied by more than 0.8 mag. This
long-term variability is interpreted as the formation and subsequent
dissipation of the Be star's disc. The building up of the disc ended up in an
active X-ray state characterised by regular outbursts occurring at 80 day
intervals. The overall duration of the formation/dissipation of the disc is
found to be < 4.3 years. Optical spectroscopic and infrared photometric
observations were used to refine the spectral type of the primary (B0.2IV) and
to monitor the circumstellar envelope around the Be star. UBVRI and uvby\beta
photometric observations allowed the determination of the astrophysical
parameters of the optical companion.


title:
Selfconsistent Numerical Calculation of Relativistic Neutron Star
  Magnetospheres

abstract:
  Selfconsistent magnetospheres of rotating cosmic magnets (neutron
stars/pulsars) with arbitrary inclination of the magnetic against the rotation
axis are considered. Present studies concentrate on the regime dominated by the
force--free surface (FFS). A macroscopic fluid description is applied and
radiation reaction is taken into account. As in earlier work of our group, a
'standard set of parameters' is used. Under these conditions, the following
features are found among other results: global charge separation exists for all
degrees of inclination of the magnetic against the rotation axis; clouds of
different charge are seperated by regions of vanishing particle number density;
as expected, test particles inserted into the latter regions propagate into one
of the adjacent clouds; strong polodial currents exist; locally averaged
particle energies for protons typically range up to $10^{16}-10^{17}$ eV,
depending on the angle of inclination.


title:
High-resolution X-ray spectroscopy and imaging of supernova remnant
  N132D

abstract:
  The observation of the supernova remnant N132D by the scientific instruments
on board the XMM-Newton satellite is presented. The X-rays from N132D are
dispersed into a detailed line-rich spectrum using the Reflection Grating
Spectrometers. Spectral lines of C, N, O, Ne, Mg, Si, S, and Fe are identified.
Images of the remnant, in narrow wavelength bands, produced by the European
Photon Imaging Cameras reveal a complex spatial structure of the ionic
distribution. While K-shell Fe emission seems to originate near the centre, all
of the other ions are observed along the shell. A high O VII / O VIII emission
ratio is detected on the northeastern edge of the remnant. This can be a sign
of hot ionising conditions, or it can reflect relatively cool gas. Spectral
fitting of the CCD spectrum suggests high temperatures in this region, but a
detailed analysis of the atomic processes involved in producing the O VII
spectral lines leads to the conclusion that the intensities of these lines
alone cannot provide a conclusive distinction between the two scenarios.


title:
Shock geometry and inverse Compton emission from the wind of a binary
  pulsar

abstract:
  PSR B1259-63 is a 47ms radio pulsar with a high spin-down luminosity which is
in a close, highly eccentric 3.5-year orbit about a bright stellar companion.
The binary system may be a detectable source of hard gamma-rays produced by
inverse Compton scattering of photons from the B2e star SS2883 by electrons and
positrons in the pulsar wind. The star provides an enormous density of optical
photons in the vicinity of the pulsar, particularly at epochs near periastron.
We calculate the emission from the unshocked region of the pulsar wind,
assuming that it terminates at a shock where it attains pressure balance with
the companion's wind. The spectra and light curves for the inverse Compton
emission from the shock-terminated wind are compared with those for an
unterminated wind. If the pulsar's wind is weaker than that from the companion
star, the termination of the wind decreases the inverse Compton flux,
particularly near periastron. The termination shock geometry has the effect of
decreasing the asymmetry of the gamma-ray light curve around periastron, which
arises because of the asymmetrical variation of the scattering angle.


title: Sensitivity of an Imaging Space Infrared Interferometer

abstract:
  We study the sensitivities of space infrared interferometers. We formulate
the signal-to-noise ratios of infrared images obtained by aperture synthesis in
the presence of source shot noise, background shot noise and detector read
noise. We consider the case in which n beams are pairwise combined at n(n-1)/2
detectors, and the case in which all the n beams are combined at a single
detector. We apply the results to future missions, Terrestrial Planet Finder
and Darwin. We also discuss the potential of a far-infrared interferometer for
a deep galaxy survey.


title:
Naked eye star visibility and limiting magnitude mapped from DMSP-OLS
  satellite data

abstract:
  We extend the method introduced by Cinzano et al. (2000a) to map the
artificial sky brightness in large territories from DMSP satellite data, in
order to map the naked eye star visibility and telescopic limiting magnitudes.
For these purposes we take into account the altitude of each land area from
GTOPO30 world elevation data, the natural sky brightness in the chosen sky
direction, based on Garstang modelling, the eye capability with naked eye or a
telescope, based on the Schaefer (1990) and Garstang (2000b) approach, and the
stellar extinction in the visual photometric band. For near zenith sky
directions we also take into account screening by terrain elevation. Maps of
naked eye star visibility and telescopic limiting magnitudes are useful to
quantify the capability of the population to perceive our Universe, to evaluate
the future evolution, to make cross correlations with statistical parameters
and to recognize areas where astronomical observations or popularisation can
still acceptably be made. We present, as an application, maps of naked eye star
visibility and total sky brightness in V band in Europe at the zenith with a
resolution of approximately 1 km.


title: On the Fine Structure in the Fireballs Peak of the 1998 Leonids

abstract:
  The Leonids meteor shower of November 1998 has shown a double activity. An
unexpected shower of fireballs occurred about 16 hours before the expected
maximum of the meteor activity. The activity profile of the fireball shower
revealed also a fine structure. The hypotesis of tidal origin of such
sub-structures is discussed. The close encounter of the meteoroid stream with
the Earth in 1366 and the encounters with Saturn (in 1630) and Jupiter (in
1732), are identified as the cause of the main features of the structure. Such
analysis can be applied to the incoming 2000 Leonids' display.


title: The nature of dwarf nova outbursts

abstract:
  We show that if the dwarf-nova disc instability model includes the effects of
heating by stream impact and tidal torque dissipation in the outer disc, the
calculated properties of dwarf-nova outbursts change considerably, and several
notorious deficiencies of this model are repaired. In particular: (1)
outside-in outbursts occur for mass transfer rates lower than in the standard
model as required by observations; (2) the presence of long (wide) and short
(narrow) outbursts with similar peak luminosities is a natural property of the
model. Mass-transfer fluctuations by factors ~ 2 can explain the occurrence of
both long and short outbursts above the cataclysmic variable period gap,
whereas below 2 hr only short normal outbursts are expected (in addition to
superoutbursts which are not dealt with in this article). With additional
heating by the stream and tidal torques, such fluctuations can also explain the
occurrence of both outside-in and inside-out outbursts in SS Cyg and similar
systems. The occurrence of outside-in outbursts in short orbital-period, low
mass-transfer-rate systems requires the disc to be much smaller than the
tidal-truncation radius. In this case the recurrence time of both inside-out
and outside-in outbursts have a similar dependence on the mass-transfer rate.


title: The BAIKAL neutrino project: status report

abstract:
  We review the present status of the Baikal Neutrino Project and present
preliminary results of a search for upward going atmospheric neutrinos, WIMPs
and magnetic monopoles obtained with the detector NT-2000 during 1998. Also the
results of a search for very high energy neutrinos with partially completed
detector in 1996 are presented.


title: Do relativistic corrections affect microlensing amplification?

abstract:
  Studies of gravitational microlensing are usually based on the lens equation,
which is valid only to first order in the gravitational constant $G$. However,
the amplification factor of microlensing is a second-order quantity with
respect to $G$. Despite this fact, conventional studies are still based on the
lowest-order lens equation. Then the question naturally arises: Why are these
conventional studies justified? We carefully study the relativistic correction
to the amplification factor at $O(G^2)$. We show that the amplification factor
for each image is corrected. However, the total amplification remains unchanged
at this order.


title: Microquasars: Open Questions and Future Perspectives

abstract:
  The discovery and subsequent study of microquasars lead to major progress in
our understanding of: 1) the nature of relativistic jets seen elsewhere in the
universe, and 2) the connection between the accretion onto compact objects and
the formation of collimated jets. A detailed account of the major progress
accomplished until present was published in Annual Review of Astronomy &
Astrophysics (Mirabel & Rodr\'\i guez, 1999). Here I review the questions that
remain unanswered, as well as the future perspectives that this new field of
research is opening.


title:
General Relativistic Electromagnetic Fields of a Slowly Rotating
  Magnetized Neutron Star. I. Formulation of the equations

abstract:
  We present analytic solutions of Maxwell equations in the internal and
external background spacetime of a slowly rotating magnetized neutron star. The
star is considered isolated and in vacuum, with a dipolar magnetic field not
aligned with the axis of rotation. With respect to a flat spacetime solution,
general relativity introduces corrections related both to the monopolar and the
dipolar parts of the gravitational field. In particular, we show that in the
case of infinite electrical conductivity general relativistic corrections due
to the dragging of reference frames are present, but only in the expression for
the electric field. In the case of finite electrical conductivity, however,
corrections due both to the spacetime curvature and to the dragging of
reference frames are shown to be present in the induction equation. These
corrections could be relevant for the evolution of the magnetic fields of
pulsars and magnetars. The solutions found, while obtained through some
simplifying assumption, reflect a rather general physical configuration and
could therefore be used in a variety of astrophysical situations.


title: Detection of nonrandom patterns in cosmological gravitational clustering

abstract:
  A new method for analyzing point patterns produced by the evolution of
gravitational clustering is presented. The method is taken from the study of
molecular liquids, where it has been introduced for making a statistical
description of anisotropic distributions. The statistical approach is based on
the spherical harmonic expansion of angular correlations. A general
introduction to the method is given; a theoretical analysis shows that it is
partially connected with previous harmonic analyses applied to galaxy catalogs.
The effectiveness of the statistical analysis in quantifying clustering
morphology is illustrated by applying the statistical estimators to point
distributions produced by an ensemble of cosmological $N-$ body simulations
with a CDM spectrum. The results demonstrate that the statistical method is
able to detect anisotropies in non-random patterns, with different scales being
probed according to the expansion coefficients.


title:
Infrared Emission from Interstellar Dust. I. Stochastic Heating of Small
  Grains

abstract:
  We present a method for calculating the infrared emission from a population
of dust grains heated by starlight, including very small grains for which
stochastic heating by starlight photons results in high temperature transients.
Because state-to-state transition rates are generally unavailable for complex
molecules, we consider model PAH, graphitic, and silicate grains with realistic
vibrational mode spectra and realistic radiative properties. The vibrational
density of states is used in a statistical-mechanical description of the
emission process. Unlike previous treatments, our approach fully incorporates
multiphoton heating effects, important for large grains or strong radiation
fields. We discuss how the "temperature" of the grain is related to its
vibrational energy. By comparing with an "exact" statistical calculation of the
emission process, we determine the conditions under which the "thermal" and the
"continuous cooling" approximations can be used to calculate the emission
spectrum.
  We present results for the infrared emission spectra of PAH grains of various
sizes heated by starlight. We show how the relative strengths of the 6.2, 7.7,
and 11.3um features depend on grain size, starlight spectrum and intensity, and
grain charging conditions. We show results for grains in the "cold neutral
medium", "warm ionized medium", and representative conditions in
photodissociation regions. Our model results are compared to observed ratios of
emission features for reflection nebulae and photodissociation regions, the
Milky Way, normal spiral galaxies, and starburst galaxies.


title:
Infrared Emission from Interstellar Dust. II. The Diffuse Interstellar
  Medium

abstract:
  We present a quantitative model for the infrared emission from dust in the
diffuse interstellar medium. The model consists of a mixture of amorphous
silicate grains and carbonaceous grains, each with a wide size distribution
ranging from molecules containing tens of atoms to large grains > 1 um in
diameter. We assume that the carbonaceous grains have polycyclic aromatic
hydrocarbon (PAH)-like properties at very small sizes, and graphitic properties
for radii a > 50 A. On the basis of recent laboratory studies and guided by
astronomical observations, we propose "astronomical" absorption cross sections
for use in modeling neutral and ionized PAHs from the far ultraviolet to the
far infrared. We also propose modifications to the far-infrared emissivity of
"astronomical silicate". We calculate energy distribution functions for small
grains undergoing "temperature spikes" due to stochastic absorption of
starlight photons, using realistic heat capacities and optical properties.
Using a grain size distribution consistent with the observed interstellar
extinction, we are able to reproduce the near-IR to submillimeter emission
spectrum of the diffuse interstellar medium, including the PAH emission
features at 3.3, 6.2, 7.7, 8.6, and 11.3um. The model is compared with the
observed emission at high Galactic latitudes as well as in the Galactic plane,
as measured by COBE and IRTS. We calculate infrared emission spectra for our
dust model heated by a range of starlight intensities, and we provide tabulated
dust opacities (extended tables available at
http://www.astro.princeton.edu/~draine/dust/dustmix.html)


title:
Ultra - High Energy Cosmic Rays from decay of the Super Heavy Dark
  Matter Relics

abstract:
  In this paper we briefly discuss the problem of the origin of Ultra High
Energy Cosmic Rays in the framework of Top-Down models. We show that, for high
energy of decays and in a wide range of spectra of injected protons, their
extragalactic flux is consistent with the observed fluxes of cosmic rays in the
energy range 0.1 E_{GZK}< E < 10E_{GZK}. For suitable energy and spectra of
injected protons, the contribution of galactic sources is moderate, in this
energy range, but it dominates at smaller and larger energies. In such models
we can expect that at these energies the anisotropy of cosmic rays distribution
over sky will be especially small.
  Some possible manifestations of decays of super massive particles such as,
for example, primordial black holes with masses M_{pbh} ~ 10^{-5} g, are
considered. In particular, we show that partial conversion of energy released
during these decays at redshifts z ~ 1000 to Ly-alpha photons can delay the
hydrogen recombination and distort the spectrum of fluctuations of the cosmic
microwave background radiation.


title: Inverse cascade in decaying 3D magnetohydrodynamic turbulence

abstract:
  We perform direct numerical simulations of three-dimensional freely decaying
magnetohydrodynamic (MHD) turbulence. For helical magnetic fields an inverse
cascade effect is observed in which power is transfered from smaller scales to
larger scales. The magnetic field reaches a scaling regime with self-similar
evolution, and power law behavior at high wavenumbers. We also find power law
decay in the magnetic and kinematic energies, and power law growth in the
characteristic length scale of the magnetic field.


title: The Evolution of Ly-alpha Absorbing Galaxies

abstract:
  The evolution of Ly-alpha absorber counts is simulated for a model population
of absorbing galaxies. The distribution of gas relative to galaxies could
evolve between moderate and low redshifts, but constraints are needed on the
strength and evolution of the ionizing UV background.


title: A Mosaic of the Coma Cluster of Galaxies with XMM-Newton

abstract:
  The Coma cluster of galaxies was observed with XMM-Newton in 12 partially
overlapping pointings. We present here the resulting X-ray map in different
energy bands and discuss the large scale structure of this cluster. Many point
sources were found throughout the observed area, at least 11 of them are
coincident with bright galaxies. We also give a hardness ratio map at the so
far highest angular resolution obtained for a cluster of galaxies. In this map
we found soft regions at the position of bright galaxies, little variation in
the central 15 arcmin, but some harder regions north of the line NGC 4874 - NGC
4889.


title: Production of 2H, 3He, and 7Li from Interactions Between Jets and Clouds

abstract:
  The interactions between jets of high-energy nuclei and nuclei of the
surrounding medium are studied. Such interactions could be initiated by jets
from active galactic nuclei interacting with surrounding cool clouds. The
resulting nuclear interactions are found to produce copious amounts of 2H and
3He from the 4He nuclei. These results suggest that jets of particles from
quasars could have produced anomalously high abundances in surrounding clouds
of some of the nuclides usually thought to characterize big bang
nucleosynthesis, specifically, the 2H seen in absorption spectra.


title:
On the Size-Dependence of the Inclination Distribution of the Main
  Kuiper Belt

abstract:
  We present a new analysis of the currently available orbital elements for the
known Kuiper belt objects. In the non-resonant, main Kuiper belt we find a
statistically significant relationship between an object's absolute magnitude
(H) and its inclination (i). Objects with H<6.5 (i.e. radii >~170 km for a 4%
albedo) have higher inclinations than those with H>6.5 (radii >~ 170 km). We
have shown that this relationship is not caused by any obvious observational
bias. We argue that the main Kuiper belt consists of the superposition of two
distinct distributions. One is dynamically hot with inclinations as large as
\~35 deg and absolute magnitudes as bright as 4.5; the other is dynamically
cold with i<~5 deg and H>6.5. The dynamically cold population is most likely
dynamically primordial. We speculate on the potential causes of this
relationship.


title: Constraints on the Birth Aggregate of the Solar System

abstract:
  Using the observed properties of our solar system, in particular the isotopic
compositions of meteorites and the regularity of the planetary orbits, we
constrain the star formation environment of the Sun within the scenario of
(external) radioactive enrichment by a massive star. This calculation yields a
probability distribution for the number of stars in the solar birth aggregate.
The Sun is most likely to have formed within a stellar group containing $N$ =
2000 $\pm$ 1100 members. The {\it a priori} probability of a star forming in
this type of environment is ${\cal P} \approx$ 0.0085, i.e., only about 1 out
of 120 solar systems are expected to form under similar conditions. We discuss
additional implications of this scenario, including possible effects from the
radiation fields provided by the putative cluster environment and dynamical
disruption of the Kuiper Belt. The constraints of this paper place tight
restrictions on the properties of the solar birth aggregate for the scenario of
external enrichment by a massive star; alternately, these tight constraints
slightly favor a self-enrichment scenario for the short-lived radioactive
species.


title: The Discovery of Argon in Comet C/1995 O1 (Hale-Bopp)

abstract:
  On 30.14 March 1997 we observed the EUV spectrum of the bright comet C/1995
O1 (Hale-Bopp) at the time of its perihelion, using our EUVS sounding rocket
telescope/spectrometer. The spectra reveal the presence H Ly beta, O+, and,
most notably, Argon. Modelling of the retrieved Ar production rates indicates
that comet Hale-Bopp is enriched in Ar relative to cosmogonic expectations.
This in turn indicates that Hale-Bopp's deep interior has never been exposed to
the 35-40 K temperatures necessary to deplete the comet's primordial argon
supply.


title: The Local Stellar Initial Mass Function

abstract:
  This contribution describes the difficult task of inferring the IMF from
local star-count data, by discussing the mass-luminosity relation, unresolved
binary, triple and quadruple systems, abundance and age spreads and Galactic
structure, all of which must be accounted for properly for the results to be
meaningful. A consensus emerges that the local IMF may be represented by a
two-part power-law, with indices alpha=1-1.5 for stars with mass m<0.5 Msun,
and the Salpeter value alpha=2.3 for more massive stars, but some uncertainties
remain. Notable is also that the sensitivity of the stellar luminosity function
(LF) to the derivative of the mass-luminosity relation is very evident in the
(local) Hipparcos and HST, open-cluster and globular-cluster LFs, thus allowing
tests of stellar structure theory. The upcoming astrometry space missions DIVA
and GAIA will undoubtedly lead to significant advances in this field.


title: Detection of Gravitational Waves from Inflation

abstract:
  Recent measurements of temperature fluctuations in the cosmic microwave
background (CMB) indicate that the Universe is flat and that large-scale
structure grew via gravitational infall from primordial adiabatic
perturbations. Both of these observations seem to indicate that we are on the
right track with inflation. But what is the new physics responsible for
inflation? This question can be answered with observations of the polarization
of the CMB. Inflation predicts robustly the existence of a stochastic
background of cosmological gravitational waves with an amplitude proportional
to the square of the energy scale of inflation. This gravitational-wave
background induces a unique signature in the polarization of the CMB. If
inflation took place at an energy scale much smaller than that of grand
unification, then the signal will be too small to be detectable. However, if
inflation had something to do with grand unification or Planck-scale physics,
then the signal is conceivably detectable in the optimistic case by the Planck
satellite, or if not, then by a dedicated post-Planck CMB polarization
experiment. Realistic developments in detector technology as well as a proper
scan strategy could produce such a post-Planck experiment that would improve on
Planck's sensitivity to the gravitational-wave background by several orders of
magnitude in a decade timescale.


title: NICMOS Imaging of the Host Galaxies of z ~ 2 - 3 Radio-Quiet Quasars

abstract:
  We have made a deep NICMOS imaging study of a sample of 5 z ~ 2 - 3
radio-quiet quasars with low absolute nuclear luminosities, and we have
detected apparent host galaxies in all of these. Most of the hosts have
luminosities approximately equal to present-day L*, with a range from 0.2 L* to
about 4 L*. These host galaxies have magnitudes and sizes consistent with those
of the Lyman break galaxies at similar redshifts and at similar rest
wavelengths, but are about two magnitudes fainter than high-z powerful radio
galaxies. The hosts of our high-z sample are comparable to or less luminous
than the hosts of the low-z RQQs with similar nuclear absolute magnitudes.
However, the high z galaxies are more compact than the hosts of the low z
quasars, and probably have only 10 - 20% of the stellar mass of their low-z
counterparts. Application of the M(bulge)/M(BH) relation found for present-day
spheroids to the stellar masses implied for the high z host galaxies would
indicate that they contain black holes with masses around 10^8 Msolar.
Comparison to their nuclear magnitudes implies accretion rates that are near or
at the Eddington limit. Although these high z hosts already contain
supermassive black holes, the galaxies will need to grow significantly to
evolve into present-day L* galaxies. These results are basically consistent
with theoretical predictions for the hierarchical buildup of the galaxy host
and its relation to the central supermassive black hole.


title: Molecular Tracers of the Central 12 pc of the Galactic Center

abstract:
  We have used the BIMA array to image the Galactic Center with a 19-pointing
mosaic in HCN(1-0), HCO+(1-0), and H 42-alpha emission with 5 km/s velocity
resolution and 13'' x 4'' angular resolution. The 5' field includes the
circumnuclear ring (CND) and parts of the 20 and 50 km/s clouds. HCN(1-0) and
HCO+ trace the CND and nearby giant molecular clouds while the H 42-alpha
emission traces the ionized gas in Sgr A West. We find that the CND has a
definite outer edge in HCN and HCO+ emission at ~45'' radius and appears to be
composed of two or three distinct streams of molecular gas rotating around the
nucleus. Outside the CND, HCN and HCO+ trace dense clumps of high-velocity gas
in addition to optically thick emission from the 20 and 50 km/s clouds. A
molecular ridge of compressed gas and dust, traced in NH3 emission and
self-absorbed HCN and HCO+, wraps around the eastern edge of Sgr A East. Just
inside this ridge are several arcs of gas which have been accelerated by the
impact of Sgr A East with the 50 km/s cloud. HCN and HCO+ emission trace the
extension of the northern arm of Sgr A West which appears to be an independent
stream of neutral and ionized gas and dust originating outside the CND. Broad
line widths and OH maser emission mark the intersection of the northern arm and
the CND. Comparison to previous NH3 and 1.2mm dust observations shows that HCN
and HCO+ preferentially trace the CND and are weaker tracers of the GMCs than
NH3 and dust. We discuss possible scenarios for the emission mechanisms and
environment at the Galactic center which could explain the differences in these
images.


title: Large Scale Structure

abstract:
  Catalogues of galaxies, clusters of galaxies and superclusters - sources of
information to study the large-scale structure of the Universe are reviewed.
The power spectrum of density perturbations, and the correlation function are
discussed as principal description functions which characterize the large-scale
structure. Special attention is payd to the geometric interpretation of these
functions, i.e. the way in which the various properties of the distribution of
galaxies in systems and systems themselves are reflected in these functions. We
discuss cosmological parameters which characterize general properties of the
Universe: the Hubble constant, densities of various populations of the
Universe, and parameters of the power spectrum of galaxies and matter.


title: Large-Scale Structure and Dark Matter Problem

abstract:
  I review the observational data most relevant for large scale structure.
These data determine the system of cosmological parameters: the Hubble
parameter, densities of various populations of the Universe, parameters
characterizing the power spectrum of matter, including the biasing parameter of
galaxies relative to matter. Recent data suggest that the overall matter/energy
density is approximately equal to the critical density, and most (0.6 - 0.7) of
the density is in the form of cosmological term or ``dark (vacuum) energy''.
The density of the matter is 0.3 - 0.4 (including hot and cold dark matter and
luminous matter), the upper limit of the density of the hot dark matter is
0.05, all in units of the critical cosmological density.


title: The structure of the Universe on 100 Mpc Scales

abstract:
  Observational evidence for the presence of a preferred scale around 100 Mpc
in the distribution of high-density regions in the Universe is summarised. Toy
models with various degrees of regularity are analysed to understand better the
observational data. Predictions of models which produce a feature on the
initial power spectrum of matter are analysed and compared with new
observational data on the CMB angular spectrum, cluster mass function, and
galaxy and cluster power spectrum.


title: Evolutionary Constraints from Infra-Red Source Counts

abstract:
  The backward evolution approach to modelling galaxy source counts is
re-visited in the wake of the numerous results and revelations from the
Infrared Space Observatory (ISO), the Submillimetre Common User Bolometer Array
(SCUBA) and the detections and measurements of the cosmic extragalactic
background light. Using the framework of the Pearson and Rowan-Robinson (1996)
galaxy evolution model, the observed source counts and background measurements
are used to constrain the evolution in the galaxy population. It is found that
a strong evolution in both density and luminosity of the high luminosity tail
of the IR luminosity function, interpreted as the ultraluminous galaxies
discovered first by IRAS and later elevated in status by SCUBA and ISO, can
account for the source counts from 15um (where it matches the undulation in the
integral counts and hump in the differential counts extremely well), to the
sub-mm region, as well as explain the peak in the cosmic infrared background at
140um. The sub-mm counts are interpreted as the superposition of 2 separate
populations comprising of ULIGs at the brighter sub-mm fluxes and starburst
galaxies at fluxes fainter than 2mJy. In this scenario the high redshift ULIGs
are tenuously interpreted as the progenitors of today's giant elliptical
galaxies.


title: Numerical simulations of the accretion-ejection instability

abstract:
  The Accretion-Ejection Instability (AEI) is explored numerically using a
global 2d model of the inner region of a magnetised accretion disk. The disk is
initially currentless but threaded by an external vertical magnetic field
created by external currents, and frozen in the flow. In agreement with the
theory a spiral instability, similar in many ways to those observed in
self-gravitating disks, but driven by magnetic stresses, develops when the
magnetic field is close to equipartition with the disk thermal pressure. The
present non-linear simulations give good evidence that such an instability can
occur in the inner region of accretion disks.


title:
Observation of X-ray lines from a Gamma-Ray Burst (GRB991216): Evidence
  of Moving Ejecta from the Progenitor

abstract:
  We report on the discovery of two emission features observed in the X-ray
spectrum of the afterglow of the gamma-ray burst (GRB) of 16 Dec. 1999 by the
Chandra X-Ray Observatory. These features are identified with the Ly$_{\alpha}$
line and the narrow recombination continuum by hydrogenic ions of iron at a
redshift $z=1.00\pm0.02$, providing an unambiguous measurement of the distance
of a GRB. Line width and intensity imply that the progenitor of the GRB was a
massive star system that ejected, before the GRB event, $\approx 0.01 \Ms$ of
iron at a velocity $\approx 0.1 c$, probably by a supernova explosion.


title:
On the hypothesis of an advection-dominated flow in the core of NGC
  1052: new constraints from a BeppoSAX observation

abstract:
  We report the results of a broadband (0.1-100 keV) X-ray observation of the
nearby elliptical galaxy NGC1052, performed with the BeppoSAX observatory. We
confirm the presence of a bright (2-10 keV luminosity ~ 4 x 10^{42} erg/s) and
strongly absorbed (NH ~ 2 x 10^{23} atoms/cm/cm) X-ray source. The flatness of
the X-ray spectrum (photon index ~1.4), the estimated low accretion rate (m-dot
\~ 10^{-4}) and the radio-to-X-ray spectral energy distribution suggest that
this observation may represent the first direct measurement above 10 keV of an
accretion-dominated flow in an elliptical galaxy.


title: On the Origin of Faint Intracluster Starlight in Coma

abstract:
  Using N-body numerical simulations, we examine possible mechanisms for the
origin of the intracluster starlight features recently discovered in the Coma
cluster of galaxies. We show that tidal interactions of a ``normal'' elliptical
galaxy with a symmetrically distributed dark matter potential do not produce
the observed intracluster starlight features. A head-on collision of two normal
ellipticals does, however, explain the origin of the intracluster features with
surface brightness about 26 mag/arcsec$^2$). Another possible explanation for
the intracluster starlight features is galactic tidal interactions with massive
intracluster substructures. The presence of substructures in Coma with a
density of $\sim$ 0.1 times the density in the center of the galaxy, and with a
total mass about three orders of magnitude larger than the mass of a normal
elliptical galaxy, would account for the observations.


title: Optical and Infrared Spectroscopy of the type IIn SN 1998S : Days 3-127

abstract:
  We present contemporary infrared and optical spectroscopic observations of
the type IIn SN 1998S for the period between 3 and 127 days after discovery. In
the first week the spectra are characterised by prominent broad emission lines
with narrow peaks superimposed on a very blue continuum(T~24000K). In the
following two weeks broad, blueshifted absorption components appeared in the
spectra and the temperature dropped. By day 44, broad emission components in H
and He reappeared in the spectra. These persisted to 100-130d, becoming
increasingly asymmetric. We agree with Leonard et al. (2000) that the broad
emission lines indicate interaction between the ejecta and circumstellar
material (CSM) and deduce that progenitor of SN 1998S appears to have gone
through at least two phases of mass loss, giving rise to two CSM zones.
Examination of the spectra indicates that the inner zone extended to <90AU,
while the outer CSM extended from 185AU to over 1800AU. Analysis of high
resolution spectra shows that the outer CSM had a velocity of 40-50 km/s.
Assuming a constant velocity, we can infer that the outer CSM wind commenced
more than 170 years ago, and ceased about 20 years ago, while the inner CSM
wind may have commenced less than 9 years ago. During the era of the outer CSM
wind the outflow was high, >2x10^{-5}M_{\odot}/yr corresponding to a mass loss
of at least 0.003M_{\odot} and suggesting a massive progenitor. We also model
the CO emission observed in SN 1998S. We deduce a CO mass of ~10^{-3} M_{\odot}
moving at ~2200km/s, and infer a mixed metal/He core of ~4M_{\odot}, again
indicating a massive progenitor.


title: Testing current synthesis models of the X-ray background

abstract:
  We present synthesis models of the X-ray background where the available X-ray
observational constraints are used to derive information on the AGN population
properties. We show the need for luminous X-ray absorbed AGNs, the QSO2s, in
reproducing the 2-10 keV source counts at relatively bright fluxes. We compare
a model where the evolution of absorbed AGNs is faster than that of unabsorbed
ones, with a standard model where absorbed and unabsorbed AGNs evolve at the
same rate. It is found that an increase by a factor of ~2 from z=0 to z~1.3 in
the ratio between absorbed and unabsorbed AGNs would provide a significant
improvement in the data description. Finally, we make predictions on the AGNs
to be observed in deep X-ray surveys which contain information on the AGN space
density at high redshift.


title:
X-ray Energy Spectra of the Super-soft X-ray Sources CAL87 and
  RXJ0925.7-4758 Observed with ASCA

abstract:
  We report observation results of the super-soft X-ray sources (SSS) CAL87 and
RXJ0925.7-4758 with the X-ray CCD cameras (Solid-state Imaging Spectrometer;
SIS) on-board the ASCA satellite. We have applied theoretical spectral models
to CAL87, and constrained the white dwarf mass and intrinsic luminosity as 0.8
- 1.2 M_solar and 4 x 10^{37}- 1.2 x 10^{38} erg s^{-1}, respectively. However,
we have found the observed luminosity is an order of magnitude smaller than the
theoretical estimate, which indicates the white dwarf is permanently blocked by
the accretion disk, and we are observing a scattering emission by a fully
ionized accretion disk corona (ADC) whose column density is ~ 1.5 x 10^{23}
cm^{-2}. Through simulation, we have shown that the orbital eclipse can be
explained by the ADC model, such that a part of the extended X-ray emission
from the ADC is blocked by the companion star filling its Roche lobe. We have
found that very high surface gravity and temperature, ~ 10^{10} cm s^{-2} and ~
100 eV respectively, as well as a strong absorption edge at ~ 1.02 keV, are
required to explain the X-ray energy spectrum of RXJ0925.7-4758. These values
are only possible for an extremely heavy white dwarf near the Chandrasekhar
limit. Although the super soft source luminosity should be ~ 10^{38} erg s^{-1}
at the Chandrasekhar limit, the observed luminosity of RXJ0925.7-4758 is nearly
two orders of magnitude smaller even assuming an extreme distance of ~10 kpc.
To explain the luminosity discrepancy, we propose a model that very thick
matter which was previously ejected from the system, as a form of jets,
intervenes the line of sight, and reduces the luminosity significantly due to
Thomson scattering.


title: Fast magnetic reconnection in free space: self-similar evolution process

abstract:
  We present a new model for time evolution of fast magnetic reconnection in
free space, which is characterized by self-similarity. Reconnection triggered
by locally enhanced resistivity assumed at the center of the current sheet can
self-similarly and unlimitedly evolve until external factors affect the
evolution. The possibility and stability of this type of evolution are verified
by numerical simulations in a very wide spatial dynamic range. Actual
astrophysical reconnection in solar flares and geomagnetospheric substorms can
be treated as an evolutionary process in free space, because the resultant
scale is much larger than the initial scale. In spite of this fact, most of the
previous numerical works focused on the evolutionary characters strongly
affected by artificial boundary conditions on the simulation boundary. Our new
model clarifies a realistic evolution for such cases. The characteristic
structure around the diffusion region is quite similar to the Petschek model
which is characterized by a pair of slow-mode shocks and the fast-mode
rarefaction-dominated inflow. However, in the outer region, a vortex-like
return flow driven by the fast-mode compression caused by the piston effect of
the plasmoid takes place. The entire reconnection system expands
self-similarly.


title:
Energy Release on the Surface of a Rapidly Rotating Neutron Star during
  Disk Accretion: A Thermodynamic Approach

abstract:
  The total energy E of a star as a function of its angular momentum J and mass
M in the Newtonian theory: E = E(J, M) [in general relativity, the
gravitational mass M of a star as a function of its angular momentum J and rest
mass m, M = M(J, m)], is used to determine the remaining parameters (angular
velocity, equatorial radius, chemical potential, etc.) in the case of rigid
rotation. Expressions are derived for the energy release during accretion onto
a cool (with constant entropy), rapidly rotating neutron star (NS) in the
Newtonian theory and in general relativity. A separate analysis is performed
for the cases where the NS equatorial radius is larger and smaller than the
radius of the marginally stable orbit in the disk plane. An approximate formula
is proposed for the NS equatorial radius for an arbitrary equation of state,
which matches the exact one at J = 0.


title: Galactic Disk Warps

abstract:
  This review addresses recent developments in the field of disk galaxy warps.
Both results from a new HI survey of edgeon disk galaxies, and of simulations
of the interaction between a disk+halo and an orbiting satelite, will be
discussed.


title: Radio Pulsars in the Magellanic Clouds

abstract:
  We report the results of a survey of the Small Magellanic Cloud (SMC) for
radio pulsars conducted with the 20-cm multibeam receiver of the Parkes
64-meter telescope. This survey targeted a more complete region of the SMC than
a previous pulsar search and had an improvement in sensitivity by a factor of
about two for most pulsar periods. This survey is much more sensitive to fast
young pulsars (with P < 100 ms) and is the first survey of the SMC with any
sensitivity to millisecond pulsars. Two new pulsars were discovered in the
survey, one of which is located within the SMC. The number of pulsars found in
the survey is consistent with the expected number derived using several
methods. We also report the serendipitous discovery of a new pulsar in the 30
Doradus region of the Large Magellanic Cloud (LMC). These discoveries bring the
total number of rotation-powered pulsars currently known in the Magellanic
Clouds to eight. We have also made refined timing measurements for the new
discoveries as well as for three previously known LMC pulsars. The age
distribution of luminous Magellanic Cloud pulsars supports the conjecture that
pulsars younger than about 5 Myr are more luminous on average than older
pulsars.


title: Optical and EUV Light Curves of Dwarf Nova Outbursts

abstract:
  We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV
light curves of dwarf novae in outburst to place constraints on the nature of
dwarf nova outbursts. From the observed optical-EUV time delays of 0.75-1.5
days, we show that the propagation velocity of the dwarf nova instability
heating wave is ~ 3 km/s.


title:
Is There Still Room for Warm/Hot Gas? Simulating the X-ray Background
  Spectrum

abstract:
  At low redshifts, a census of the baryons in all known reservoirs falls a
factor of two to four below the total baryon density predicted from Big Bang
nucleosynthesis arguments and observed light element ratios. Recent
cosmological hydrodynamic simulations suggest that a significant fraction of
these missing baryons could be in the form of warm/hot gas in the filaments and
halos within which most field galaxies are embedded. With the release of source
count results from Chandra and recent detections of this gas in O VI quasar
absorption lines, it becomes interesting to examine the predictions and limits
placed on this component of the X-ray background (XRB). We have used new
hydrodynamical simulations to predict the total X-ray spectrum from the gas in
the 100 eV to 10 keV range. We find that, when uncertainties in the
normalization of the observed XRB and the value of Omega_b are taken into
account, our results are consistent with current observational limits placed on
the contribution of emission from gas to the XRB. In the 0.5-2 keV range, we
expect the contribution from this component to be 0.63 10^{-12} erg s^-1 cm^-2
deg^-2 or between 6% and 18% of the extragalactic surface brightness. The peak
fraction occurs in the 0.5-1 keV range where the predicted line emission
mirrors a spectral bump seen in the latest ASCA/ROSAT XRB data.


title: Precessing collimated outflows in the planetary nebula IC 4846

abstract:
  We present [N II] and H-alpha images and high resolution long-slit spectra of
the planetary nebula IC 4846, which reveal, for the first time, its complex
structure and the existence of collimated outflows. The object consists of a
moderately elongated shell, two (and probably three) pairs of collimated
bipolar outflows at different orientations, and an attached circular shell. One
of the collimated pairs is constituted by two curved, extended filaments whose
properties indicate a high velocity, bipolar precessing jet. A difference of
\~10 km/s is found between the systemic velocity of the precessing jets and the
centroid velocity of the nebula, as recently report for Hu 2-1. We propose that
this difference is due to orbital motion of the ejection source in a binary
central star. The orbital separation and period estimates for the binary star
are less than or equal to 30 AU and 100 yr, respectively. These are similar to
those previously estimated for Hu 2-1, linking the central stars of both
planetary nebulae to interacting binaries. Extraordinary similarities also
exist between IC 4846 and the bewildering planetary nebula NGC 6543, suggesting
a similar formation history for both objects.


title: Nuclear spectra of polar-ring galaxies

abstract:
  We report the results of spectroscopic observations of 8 southern polar-ring
galaxies (PRGs), in the wavelength range 5900-7300 \AA. We fing that 5 out of 8
galaxies contain LINERs or Sy nuclei. Taking into consideration all PRGs with
available spectral data, we estimate that about half of all PRGs and PRG
candidates have either LINER or Seyfert nuclei. The observed widths of the
[NII]6583 line in the nuclei of early-type PRGs follow the linewidth - absolute
luminosity relation for normal E/S0 galaxies. We found that one of the observed
galaxies - ESO 576-G69 - is a new kinematically-confirmed polar-ring galaxy
with a spiral host.


title:
Model Independent Primordial Power Spectrum from Maxima, Boomerang, and
  DASI Data

abstract:
  A model-independent determination of the primordial power spectrum of matter
density fluctuations could uniquely probe physics of the very early universe,
and provide powerful constraints on inflationary models. We parametrize the
primordial power spectrum $A_s^2(k)$ as an arbitrary function, and deduce its
binned amplitude from the cosmic microwave background radiation anisotropy
(CMB) measurements of Maxima, Boomerang, and DASI. We find that for a flat
universe with $A_s^2(k)=1$ (scale-invariant) for scales $k<0.001 $h/Mpc, the
primordial power spectrum is marginally consistent with a scale-invariant
Harrison-Zeldovich spectrum. However, we deduce a rise in power compared to a
scale-invariant power spectrum for $0.001 h/{Mpc} \la k \la 0.01 h/{Mpc}$. Our
results are consistent with large-scale structure data, and seem to suggest
that the current observational data allow for the possibility of unusual
physics in the very early universe.


title:
Scattering in the inner accretion disk and the waveforms and
  polarization of millisecond flux oscillations in LMXBs

abstract:
  The scattering by the inner accretion disk of X-ray radiation generated near
the surface of a spinning neutron star in a low-mass X-ray binary (LMXB) has
observable effects on the waveforms of millisecond X-ray flux oscillations
produced e.g. during type-I bursts or in the millisecond pulsar SAX
J1808.4--3658. We study these effects in the framework of a simplified model in
which there is a single emitting spot on the stellar surface, which is visible
both directly and in X-rays scattered from the disk. The main signature of
scattering from a thin disk is that the pulse of scattered flux leads (if the
star rotates in the same sense as the disk) or lags (in the contrary case) the
primary pulse of direct emission by a quarter of a spin cycle. This is caused
by Doppler boosting of radiation in the sub-relativistic Keplerian flow. The
disk-scattered flux is revealed better in energy-resolved waveforms and the
phase dependence of the polarized flux component. The phenomenon discussed
permits direct testing of the presence of standard thin disks near the neutron
stars in LMXBs and should be observable with future X-ray timing experiments
having a few times better sensitivity than RXTE and also with sensitive X-ray
polarimeters.


title: The Metallicity of 0.5<z<1 Field Galaxies

abstract:
  We have measured the emission line ratios in a sample of 34 CFRS star-forming
galaxies with redshifts between 0.5 < z < 1.0, and computed their metallicities
by means of the empirically-calibrated R_23 metallicity estimator introduced by
Pagel et al. (1979). The current analysis concentrates on the 15 galaxies with
L_Hbeta > 1.2x10^41 erg s-1. Although our results can only be regarded as
preliminary until near-IR spectroscopy of Halpha and [NII]6583 are available,
the metallicities of these galaxies appear to be remarkably similar to those of
local galaxies selected in the same way, and there appears to have been little
change in the relationship between metallicity and line- and
continuum-luminosity from z~1 to today. At this stage our results do not
support the idea that these galaxies, known to be generally small and with
late-type morphologies, are dwarf galaxies brightened by large bursts of
star-formation, as had been suggested from previous studies. Rather, our
findings are more consistent with a picture in which these systems are the
progenitors of today's massive metal-rich galaxies.


title: Current status of Asteroseismology

abstract:
  Oscillation frequencies are the most accurate properties one can measure for
a star, potentially allowing detailed tests of stellar models and evolution
theories. We briefly review asteroseismology for two classes of stars. In delta
Scuti variables, the main problems are the identification of the observed modes
and the theoretical treatment of rotation. In solar-like stars the main
difficulty is the tiny amplitudes, but credible detections are now being made.
These confirm that stars are oscillating at the approximately the expected
levels, but suggest that amplitudes scale as 1/g rather than L/M. We also
stress the importance of multi-site campaigns. Several space missions will be
launched over the coming years, promising an exciting future for
asteroseismology.


title: Status of the CANGAROO-III Project

abstract:
  The CANGAROO-III project, a system of four 10 m telecopes dedicated for
gamma-ray astrophysics, has started in 1999 and is expected to complete in 2004
in Woomera, South Australia. We report the construction work during the first
year, which includes the completion of the first 10 m telescope built as a 7 m
telescope in 1999, and the work in progess to increase the performance by
constructing three more similar telescopes based on the experience gained
during the construction of the first telescope.


title: Blazar jets: the spectra

abstract:
  The radiation observed by blazars is believed to originate from the
transformation of bulk kinetic energy of relativistic jets into random energy.
A simple way to achieve this is to have an intermittent central power source,
producing shells of plasma with different bulk Lorentz factors. These shells
will collide at some distance from the center, producing shocks and then
radiation. This scenario, called internal shock model, is thought to be at the
origin of the gamma-rays observed in gamma-ray bursts and can work even better
in blazars. It accounts for the observed key characteristics of these objects,
including the fact that radiation must be preferentially produced at a few
hundreds of Schwarzschild radii from the center, but continues to be produced
all along the jet. At the kpc scale and beyond, the slowly moving parts of a
(straight) jet can be illuminated by the beamed radiation of the core, while
the fast parts of the jet will see enhanced cosmic microwave radiation. In both
cases the Inverse Compton process can be the dominant radiation process,
leading to a copious production of high energy (X-rays and beyond) radiation in
both radio loud quasars and radio-galaxies.


title: An XMM-Newton study of the sub-structure in M87's halo

abstract:
  The high signal to noise and good point spread function of XMM have allowed
the first detailed study of the interaction between the thermal and radio
emitting plasma in the central regions of M87. We show that the X-ray emitting
structure, previously seen by ROSAT, is thermal in nature and that the east and
southwest extensions in M87's X-ray halo have a significantly lower temperature
(kT= 1.5 keV) than the surrounding ambient medium (kT= 2.3 keV). There is
little or no evidence for non-thermal emission with an upper limit on the
contribution of a power law component of spectral index flatter than 3 being
less than 1% of the flux in the region of the radio lobes.


title:
What can we infer about the underlying physics from burst distributions
  observed in an RMHD simulation ?

abstract:
  We determine that the sizes of bursts in mean-square current density in a
reduced magnetohydrodynamic (RMHD)simulation follow power-law probability
density function (PDF). The PDFs for burst durations and waiting time between
bursts are clearly not exponential and could also be power-law. This suffices
to distinguish their behaviour from the original Bak et al. sandpile model
which had exponential waiting time PDFs. However, it is not sufficient to
distinguish between turbulence, some other SOC-like models, and other red noise
sources.


title: The Optical Extragalactic Background Light from Resolved Galaxies

abstract:
  We discuss the ultraviolet to near-IR galaxy counts from the deepest imaging
surveys, including the northern and southern Hubble Deep Fields. The
logarithmic slope of the galaxy number-magnitude relation is flatter than 0.4
in all seven UBVIJHK optical bandpasses at faint magnitudes, i.e. the light
from resolved galaxies has converged from the UV to the near-IR. Most of the
galaxy contribution to the extragalactic background light (EBL) comes from
relatively bright, low-redshift objects (50% at V_AB<21 and 90% at V_AB<25.5).
We find a lower limit to the surface brightness of the optical EBL of about 15
nW/m^2/sterad, comparable to the intensity of the far-IR background from COBE
data. Diffuse light, lost because of surface brightness selection effects, may
add substantially to the EBL.


title:
Evidence for Ionised Accretion Discs in Five Narrow-Line Seyfert 1
  Galaxies

abstract:
  (Abridged) We present the results of fitting ASCA spectra of six narrow-line
Seyfert 1 (NLS1) galaxies with the ionised reflection models of Ross & Fabian
(1993). We find that five of the galaxies (TONS 180, PKS 0558-504, Ark 564, Mrk
335 and PG 1244+026) are well fit by the ionised disc model, and these are
often better fits than the alternative models considered. The sixth galaxy, NGC
4051, has additional spectral complexity that cannot be well described by a
simple ionised disc model or any of the other alternative models. All six of
the NLS1s we considered show evidence for a broad Fe Kalpha line, but none of
the line centroids are consistent with emission from highly ionised Fe. This is
most likely due to the line being redshifted because of relativistic effects.
We note that sources with larger ionisation parameters tend to have larger Fe
Kalpha EWs. We interpret this as evidence that ionised Fe features are making
their presence felt in the spectra. Since most of our sources have steep
spectra, highly ionised features are predicted even by the new variable density
reflection models. The one source we analyse with a photon index less than two
has the lowest ionisation parameter in our sample. We conclude that our result
is the strongest evidence yet that NLS1 might have ionised accretion discs.
This result gives further weight to the hypothesis that these objects contain
rapidly accreting black holes.


title: Does TV Col Have the longest Recorded Positive Superhumps?

abstract:
  Re-examination of extensive photometric data of TV Col reveals evidence for a
permanent positive superhump. Its period (6.4 h) is 16 percent longer than the
orbital period and obeys the well known relation between superhump period
excess and binary period. At 5.5-h, TV Col has an orbital period longer than
any known superhumping cataclysmic variable and, therefore, a mass ratio which
might be outside the range at which superhumps can occur according to the
current theory. We suggest several solutions for this problem.


title: A Spectral Line Survey from 138.3 to 150.7 GHZ toward Orion-KL

abstract:
  We present the results of a spectral line survey from 138.3 to 150.7 GHz
toward Orion-KL. The observations were made using the 14 m radio telescope of
Taeduk Radio Astronomy Observatory. Typical system temperatures were between
500 and 700 K, with the sensitivity between $0.02 - 0.06$ K in units of $\rm
T_A^*$.
  A total of 149 line spectra are detected in this survey. Fifty lines have
been previously reported, however we find 99 new detections. Among these new
lines, 32 are `unidentified', while 67 are from molecular transitions with
known identifications. There is no detection of H or He recombination lines.
The identified spectra are from a total of 16 molecular species and their
isotopic variants. In the range from 138.3 to 150.7 GHz, the strongest spectral
line is the J=3-2 transition of CS molecule, followed by transitions of the
$\rm H_2CO$, $\rm CH_3OH$, $\rm CH_3CN$, and $\rm SO_2$. Spectral lines from
the large organic molecules such as $\rm CH_3OH$, $\rm CH_3OCH_3$, $\rm
HCOOCH_3$, $\rm C_2H_5CN$ and $\rm CH_3CN$ are prominent; with 80 % of the
identified lines arising from transitions of these molecules. The rotational
temperatures and column densities are derived using the standard rotation
diagram analysis for $\rm CH_3OH$ ($\rm ^{13}CH_3OH$), $\rm HCOOCH_3$, $\rm
CH_3CN$ and $\rm SO_2$ with $\rm 10\sim 270 K$ and $\rm 0.2\sim 20\times
10^{15} cm^{-2}$. These estimates are fairly comparable to the values for the
same molecule in other frequency regions by other studies.


title: Implications of the Discovery of Millisecond Pulsar in SN 1987A

abstract:
  From the observation of a millisecond pulsar in SN 1987A, the following
implications are obtained. 1) The pulsar spindown in SN 1987A is caused by
radiating gravitational waves rather than by magnetic dipole radiation and/or
relativistic pulsar winds. 2) A mildly deformed shock wave would be formed at
the core-collapse and explosion in SN 1987A, which is consistent with the
conclusion given in Nagataki (2000). 3) The gravitational waves from the pulsar
should be detected in several years using a Fabry-Perot-Michelson
interferometer as the gravitational detector, such as LIGO and TAMA. 4) The
neutrino oscillation model is not a promising model for the explanation of the
kick velocity of the pulsar in SN 1987A. The hydrodynamical instability model
is more favored.


title:
Gravitational waves emitted by solar-type stars excited by orbiting
  planets

abstract:
  The possibility of exciting the g-modes of a solar-type star as a consequence
of the gravitational interaction with a close companion (a planet or a brown
dwarf) is studied by a perturbative approach. The amplitude of the emitted
gravitational wave is computed and compared with the quadrupole emission of the
system, showing that in some cases it can be considerably larger. The effects
of radiation reaction are considered to evaluate the timescale of the emission
process, and a Roche lobe analysis is used to establish the region where the
companion can orbit without being disrupted by tidal interactions with the
star.


title: Gravitino production in the warm inflationary scenario

abstract:
  We estimate the production of gravitinos during and after the end of a period
of warm inflation, a model in which radiation is produced continuously as the
field rolls down the potential producing dissipation. We find that gravitino
production is efficient for models in the strong dissipation regime, with the
result that standard nucleosynthesis is disrupted unless the magnitude of the
inflaton potential is very small. Combining this with the constraint from the
thermal production of adiabatic density perturbations we find the dissipation
rate must be extraordinarily strong, or that the potential is very flat.


title:
Chandra Observations of Variable Embedded X-ray sources in Orion. Paper
  I: Resolving Orion Trapezium

abstract:
  We used the High Energy Transmission Grating Spectrometer (HETGS) onboard the
Chandra X-ray Observatory to perform two observations, separated by three
weeks, of the Orion Trapezium region. The zeroth order images on the Advanced
CCD Imaging Spectrometer (ACIS) provide spatial resolution of 0.5" and moderate
energy resolution. Within a 160"x140" region around the Orion Trapezium we
resolve 111 X-ray sources with luminosities between 7x10^{28} ergs/s and
2x10^{32} ergs/s. We do not detect any diffuse emission. Many sources appear
much more heavily absorbed, with N_H in the range of 10^22 to 10^23 cm^-2. The
main objective of this paper is to study the Orion Trapezium and its close
vicinity. Most spectra of the very early type members can be fit with a
two-temperature thermal spectrum with a soft component of kT ~ 0.8 keV and a
hard component of kT ~ 2 to 3 keV. We discuss these results in the context of
stellar wind models. We detect eight additional, mostly variable X-ray sources
in the close vicinity of the Trapezium. Five of these X-rays sources are
identified with proplyds and we argue that the X-ray emission originates from
class I, II and III protostars at the cores of the proplyds.


title: The solar tachocline and its variation (?)

abstract:
  The solar tachocline, located at the interface between the latitude-dependent
rotation of the convection zone and the rigid radiative interior, presents high
gradients of angular velocity which are of particular interest for the models
of the solar dynamo and angular momentum transport. Furthermore, latitudinal
and temporal variations of the tachocline parameters, if any, are also of
particular interest in order to constrain models. We present a review of some
of the theories of the tachocline and their predictions that may be tested by
helioseismology. We describethe methods for inferring the tachocline parameters
from observations and the associated difficulties. A review of results
previously obtained is given and an analysis of the new 6 years database of
LOWL observations is presented which yields no compelling evidence of
variations or general trend of the tachocline parameters during the ascending
phase of the current solar cycle (1994-2000).


title: Long-Term RXTE Monitoring of the Anomalous X-ray Pulsar 1E 1048.1-5937

abstract:
  We report on long-term monitoring of the anomalous X-ray pulsar (AXP) 1E
1048.1-5937 using the Rossi X-ray Timing Explorer (RXTE). The timing behavior
of this pulsar is different from that of other AXPs being monitored with RXTE.
In particular, we show that the pulsar shows significant deviations from simple
spin-down such that phase-coherent timing has not been possible over time spans
longer than a few months. We find that the deviations from simple spin down are
not consistent with single "glitch" type events, nor are they consistent with
radiative precession. We show that in spite of the rotational irregularities,
the pulsar exhibits neither pulse profile changes nor large pulsed flux
variations. We discuss the implications of our results for AXP models. In the
context of the magnetar model, we suggest that 1E 1048.1-5937 may be a
transition object between the soft gamma-ray repeater and AXP populations, and
the AXP most likely to one day undergo an outburst.


title: Verifying the use of supernovae as probes of the cosmic expansion

abstract:
  We present preliminary results of a follow-up survey which aims to
characterise in detail those galaxies which hosted Type Ia supernovae found by
the Supernova Cosmology Project (SCP). Our survey has two components: Hubble
Space Telescope imaging with STIS and Keck spectroscopy with ESI, the goal
being to classify each host galaxy into one of three broad
morphological/spectral classes and hence to investigate the dependence of
supernovae properties on host galaxy type over a large range in redshift. Of
particular interest is the supernova Hubble diagram characterised by host
galaxy class which suggests that most of the scatter arises from those
occurring in late-type irregulars. Supernovae hosted by (presumed dust-free)
E/S0 galaxies closely follow the adopted SCP cosmological model. Although
larger datasets are required, we cannot yet find any significant difference in
the light curves of distant supernovae hosted in different galaxy types.


title:
Seeing Galaxies Through Thick & Thin. III. HST Imaging of the Dust in
  Backlit Spiral Galaxies

abstract:
  We present analysis of WFPC2 imaging of two spiral galaxies partially backlit
by E/S0 systems in the pairs AM1316-241 and AM0500-620, and the spiral
foreground system in NGC 1275. Images in B and I are used to determine the
reddening curve of in these systems. The spiral component of AM1316-241 shows
dust strongly concentrated in discrete arms, with a reddening law very close to
the Milky Way mean. The dust distribution is scale-free between about 100 pc
and the arm scale. The spiral in AM0500-620 shows dust concentrated in arms and
interarm spurs, with measurable interarm extinction as well. Although its dust
properties are less well-determined, we find evidence for a steeper extinction
law here. The shape of the reddening law suggests that, at least in AM1316-241,
we have resolved most of the dust structure. In AM0500-620, the slope of the
fractal perimeter-scale relation steepens systematically from low to high
extinction. In AM1316-241, we cannot determine a unique fractal dimension from
the defining area-perimeter relation, so the projected dust distribution is
best defined as fractal-like. In neither galaxy do we see regions even on
single-pixel scales in spiral arms with AB > 2.5. The measurements in NGC 1275
are compromised by our lack of independent knowledge of the foreground system's
light distribution, but masked sampling of the absorption suggests an effective
reddening curve much flatter than the Milky Way mean (perhaps indicating that
the foreground system has been affected by immersion in the hot intracluster
gas).


title: X-ray intensity-hardness correlation in Cyg X-1

abstract:
  Using data from the All-Sky Monitor aboard the Rossi X-ray Timing Explorer
(RXTE), we found that the 1.5-12 keV X-ray count rate of Cyg X-1 is, on time
scales from 90 seconds to at least 10 days, strongly correlated with the
spectral hardness of the source in the soft state, but is weakly
anti-correlated with the latter in the hard state. The correlation shows an
interesting evolution during the 1996 spectral state transition. The entire
episode can be roughly divided into three distinct phases: (1) a 20-d
transition phase from the hard state to the soft state, during which the
correlation changes from being negative to positive, (2) a 50-d soft state with
a steady positive correlation, and (3) a 20-d transition back to the hard
state. The pointed RXTE observations confirmed the ASM results but revealed new
behaviors of the source at energies beyond the ASM pass band. We discuss the
implications of our findings.


title: Non-Uniform Free-Free Absorption in the GPS Radio Galaxy 0108+388

abstract:
  We have observed the canonical gigahertz-peaked spectrum source 0108+388 with
the VLBA at a range of frequencies above and below the spectral peak. The
activity that dominates the radio emission from 0108+388, which is also
classified as a Compact Symmetric Object, is thought to be less than 1000 years
old. We present strong evidence that the spectral turnover in 0108+388 results
from free-free absorption by non-uniform gas, possibly in the form of a disk in
the central tens of parsecs.


title: Emission Line Properties of the Large Bright Quasar Survey

abstract:
  We present measurements of the optical/UV emission lines for a large
homogeneous sample of 993 quasars from the Large Bright Quasar Survey. Our
largely automated technique accounts for continuum breaks and galactic
reddening, and we perform multicomponent fits to emission line profiles,
including the effects of blended iron emission, and of absorption lines both
galactic and intrinsic. Here we describe the fitting algorithm and present the
results of line fits to the LBQS sample, including upper limits to line
equivalent widths when warranted. The distribution of measured line parameters,
principally equivalent width and FWHM, are detailed for a variety of lines,
including upper limits. We thus initiate a large-scale investigation of
correlations between the high energy continuum and emission lines in quasars,
to be extended to complementary samples using similar techniques. High quality,
reproducible measurements of emission lines for uniformly selected samples will
advance our understanding of active galaxies, especially in a new era of large
surveys selected by a variety of complementary methods.


title:
H-alpha Imaging with HST+NICMOS of An Elusive Damped Ly-alpha Cloud at
  z=0.6

abstract:
  Despite previous intensive ground-based imaging and spectroscopic campaigns
and wide-band HST imaging of the z=0.927 QSO 3C336 field, the galaxy that hosts
the damped Ly-alpha system along this line-of-sight has eluded detection. We
present a deep narrow-band H-alpha image of the field of this z=0.656 damped
Ly-alpha absorber, obtained through the F108N filter of NICMOS 1 onboard the
Hubble Space Telescope. The goal of this project was to detect any H-alpha
emission 10 times closer than previous studies to unveil the damped absorber.
We do not detect H-alpha emission between 0.05'' and 6'' (0.24 and 30 $h^{-1}$
kpc) from the QSO, with a 3-sigma flux limit of $3.70 \times 10^{-17} h^{-2}$
erg/s/cm^2 for an unresolved source, corresponding to a star formation rate
(SFR) of $0.3 h^{-2}$ M_sun/yr. This leads to a 3-sigma upper limit of 0.15
M_sun/yr/kpc^2 on the SFR density, or a maximum SFR of 1.87 M_sun/yr assuming a
disk of 4 kpc in diameter. This result adds to the number of low redshift
damped Ly-alpha absorbers that are not associated with the central regions of
Milky-Way-like disks. Damped Ly-alpha absorption can arise from high density
concentrations in a variety of galactic environments including some that,
despite their high local HI densities, are not conducive to widespread star
formation.


title: Not enough stellar mass Machos in the Galactic halo

abstract:
  We present an update of results from the search for microlensing towards the
Large Magellanic Cloud (LMC) by EROS (Experience de Recherche d'Objets
Sombres). We have now monitored 25 million stars over three years. Because of
the small number of observed microlensing candidates (four), our results are
best presented as upper limits on the amount of dark compact objects in the
halo of our Galaxy. We discuss critically the candidates and the possible
location of the lenses, halo or LMC . We compare our results to those of the
MACHO group. Finally, we combine these new results with those from our search
towards the Small Magellanic Cloud as well as earlier ones from the EROS1 phase
of our survey. The combined data is sensitive to compact objects in the broad
mass range $ 10^{-7} - 10 $ solar masses. The derived upper limit on the
abundance of stellar mass MACHOs rules out such objects as the dominant
component of the Galactic halo if their mass is smaller than 2 solar masses.


title: Evolution of the Cluster Mass Function: Gpc^3 Dark Matter Simulations

abstract:
  High-resolution N-body simulations of four popular Cold Dark Matter
cosmologies (LCDM, OCDM, QCDM, and tilted SCDM), each containing 10^5 clusters
of galaxies in a cubic gigaparsec volume, are used to determine the evolution
of the cluster mass function from z=3 to z=0. The large volume and high
resolution of these simulations allow an accurate measure of the evolution of
cosmologically important (but rare) massive clusters at high redshift. The
simulated mass function is presented for cluster masses within several radii
typically used observationally (R=0.5, 1.0, and 1.5 Mpc/h, both comoving and
physical) in order to enable direct comparison with current and future
observations. The simulated evolution is compared with current observations of
massive clusters at redshifts 0.3<z<0.8. The Omega_m=1 tilted SCDM model, which
exhibits very rapid evolution of the cluster abundance, produces too few
clusters at z>0.3 and no massive clusters at z>0.5, in stark contradiction with
observations. The Omega_m=0.3 models- LCDM, OCDM, and QCDM- all exhibit
considerably weaker evolution and are consistent with current data. Among these
low density models, OCDM evolves the least. These trends are enhanced at high
redshift and can be used to discriminate between flat and open low density
models. The simulated mass functions are compared with the Press-Schechter
approximation. Standard Press-Schechter predicts too many low mass clusters at
z=0, and too few clusters at higher redshift. We modify the approximation by a
simple parameterization of the density contrast threshold for collapse, which
has a redshift dependence. This modified Press-Schechter approximation provides
a good fit to the simulated mass functions.


title:
The Chandra Multi-wavelength Project (ChaMP): a serendipitous survey
  with Chandra archival data

abstract:
  The launch of the Chandra X-ray Observatory in July 1999 opened a new era in
X-ray astronomy. Its unprecedented, <0.5" spatial resolution and low background
are providing views of the X-ray sky 10-100 times fainter than previously
possible. We have initiated a serendipitous survey (ChaMP) using Chandra
archival data to flux limits covering the range between those reached by
current satellites and those of the small area Chandra deep surveys. We
estimate the survey will cover ~5 sq.deg./year to X-ray fluxes (2-10 keV) in
the range 1E(-13)-6E(-16) erg/cm^2/s discovering ~2000 new X-ray sources, ~80%
of which are expected to be AGN. The ChaMP has two parts, the extragalactic
survey (ChaMP) and the galactic plane survey (ChaMPlane). ChaMP promises
profoundly new science return on a number of key questions at the current
frontier of many areas of astronomy including (1) locating and studying high
redshift clusters and so constraining cosmological parameters (2) defining the
true population of AGN, including those that are absorbed, and so constraining
the accretion history of the universe, (3) filling in the gap in the
luminosity/redshift plane between Chandra deep and previous surveys in studying
the CXRB, (4) studying coronal emission from late-type stars and (5) search for
CVs and quiescent Low-Mass X-ray Binaries (qLXMBs) to measure their luminosity
functions. In this paper we summarize the status, predictions and initial
results from the X-ray analysis and optical imaging.


title:
CMB Analysis of Boomerang & Maxima & the Cosmic Parameters
  {Omega_tot,Omega_b h^2,Omega_cdm h^2,Omega_Lambda,n_s}

abstract:
  We show how estimates of parameters characterizing inflation-based theories
of structure formation localized over the past year when large scale structure
(LSS) information from galaxy and cluster surveys was combined with the rapidly
developing cosmic microwave background (CMB) data, especially from the recent
Boomerang and Maxima balloon experiments. All current CMB data plus a
relatively weak prior probability on the Hubble constant, age and LSS points to
little mean curvature (Omega_{tot} = 1.08\pm 0.06) and nearly scale invariant
initial fluctuations (n_s =1.03\pm 0.08), both predictions of (non-baroque)
inflation theory. We emphasize the role that degeneracy among parameters in the
L_{pk} = 212\pm 7 position of the (first acoustic) peak plays in defining the
$\Omega_{tot}$ range upon marginalization over other variables. Though the CDM
density is in the expected range (\Omega_{cdm}h^2=0.17\pm 0.02), the baryon
density Omega_bh^2=0.030\pm 0.005 is somewhat above the independent 0.019\pm
0.002 nucleosynthesis estimate. CMB+LSS gives independent evidence for dark
energy (Omega_\Lambda=0.66\pm 0.06) at the same level as from supernova (SN1)
observations, with a phenomenological quintessence equation of state limited by
SN1+CMB+LSS to w_Q<-0.7 cf. the w_Q=-1 cosmological constant case.


title: The Quintessential CMB, Past & Future

abstract:
  The past, present and future of cosmic microwave background (CMB) anisotropy
research is discussed, with emphasis on the Boomerang and Maxima balloon
experiments. These data are combined with large scale structure (LSS)
information and high redshift supernova (SN1) observations to explore the
inflation-based cosmic structure formation paradigm. Here we primarily focus on
a simplified inflation parameter set, {omega_b,omega_{cdm},Omega_{tot},
Omega_Q,w_Q, n_s,tau_C, sigma_8}. After marginalizing over the other cosmic and
experimental variables, we find the current CMB+LSS+SN1 data gives
Omega_{tot}=1.04\pm 0.05, consistent with (non-baroque) inflation theory.
Restricting to Omega_{tot}=1, we find a nearly scale invariant spectrum, n_s
=1.03 \pm 0.07. The CDM density, omega_{cdm}=0.17\pm 0.02, is in the expected
range, but the baryon density, omega_b=0.030\pm 0.004, is slightly larger than
the current nucleosynthesis estimate. Substantial dark energy is inferred,
Omega_Q\approx 0.68\pm 0.05, and CMB+LSS Omega_Q values are compatible with the
independent SN1 estimates. The dark energy equation of state, parameterized by
a quintessence-field pressure-to-density ratio w_Q, is not well determined by
CMB+LSS (w_Q<-0.3 at 95%CL), but when combined with SN1 the resulting w_Q<-0.7
limit is quite consistent with the w_Q=-1 cosmological constant case. Though
forecasts of statistical errors on parameters for current and future
experiments are rosy, rooting out systematic errors will define the true
progress.


title:
H-alpha Equivalent Width Variations across the Face of a Microlensed K
  Giant in the Galactic Bulge

abstract:
  We present VLT FORS1 spectroscopy that temporally resolves the second caustic
crossing of the Bulge K giant source of microlensing event EROS 2000-BLG-5, the
first time this has been accomplished for several phases of a caustic transit.
The ~1 angstrom H-alpha equivalent width of the source star increases slightly
as the center of the star egresses the caustic and then plummets by 30% during
the final limb crossing. These changes are not seen in contemporaneous spectra
of control stars in the FORS1 slit, but are qualitatively consistent with
expectations from stellar atmosphere models as the caustic differentially
magnifies different portions of the stellar face of the target. Observations
such as these in a variety of stellar lines are equivalent to atmospheric
tomography and are expected to provide a direct test of stellar models.


title: The Cosmic Background Radiation circa nu2K

abstract:
  We describe the implications of cosmic microwave background (CMB)
observations and galaxy and cluster surveys of large scale structure (LSS) for
theories of cosmic structure formation, especially emphasizing the recent
Boomerang and Maxima CMB balloon experiments. The inflation-based cosmic
structure formation paradigm we have been operating with for two decades has
never been in better shape. Here we primarily focus on a simplified inflation
parameter set, {omega_b,omega_{cdm},Omega_{tot}, Omega_\Lambda,n_s,\tau_C,
\sigma_8}. Combining all of the current CMB+LSS data points to the remarkable
conclusion that the local Hubble patch we can access has little mean curvature
(Omega_{tot}=1.08\pm 0.06) and the initial fluctuations were nearly scale
invariant (n_s=1.03\pm 0.08), both predictions of (non-baroque) inflation
theory. The baryon density is found to be slightly larger than that preferred
by independent Big Bang Nucleosynthesis estimates (omega_b=0.030\pm 0.005 cf.
0.019\pm 0.002). The CDM density is in the expected range (omega_{cdm}=0.17 \pm
0.02). Even stranger is the CMB+LSS evidence that the density of the universe
is dominated by unclustered energy akin to the cosmological constant
(Omega_\Lambda=0.66\pm 0.06), at the same level as that inferred from high
redshift supernova observations. We also sketch the CMB+LSS implications for
massive neutrinos.


title: The Snake - a Reconnecting Coil in a Twisted Magnetic Flux Tube

abstract:
  We propose that the curious Galactic Center filament known as ``The Snake''
is a twisted giant magnetic flux tube, anchored in rotating molecular clouds.
The MHD kink instability generates coils in the tube and subsequent magnetic
reconnection injects relativistic electrons. Electrons diffuse away from a coil
at an energy-dependent rate producing a flat spectral index at large distances
from it. Our fit to the data of \citet{gray95a} shows that the magnetic field
$\sim 0.4 \> \rm mG$ is large compared to the ambient $\sim 7 \mu \> \rm G$
field, indicating that the flux tube is force-free. If the {\em relative} level
of turbulence in the Snake and the general interstellar medium are similar,
then electrons have been diffusing in the Snake for about $3 \times 10^5 \> \rm
yr$, comparable to the timescale at which magnetic energy is annihilated in the
major kink. Estimates of the magnetic field in the G359.19-0.05 molecular
complex are similar to our estimate of the magnetic field in the Snake
suggesting a strong connection between the physics of the anchoring molecular
regions and the Snake. We suggest that the physical processes considered here
may be relevant to many of the radio filaments near the Galactic Center. We
also suggest further observations of the Snake and other filaments that would
be useful for obtaining further insights into the physics of these objects.


title:
Studying the Galactic Bulge Through Spectroscopy of Microlensed Sources:
  I. Theoretical Considerations

abstract:
  The observed spectra of the microlensed sources towards the Galactic bulge
may be used as a tool for studying the kinematics and extinction effects in the
Galactic bulge. In this paper, we first investigate the expected distribution
of the microlensed sources as a function of depth within the Galactic bulge.
Our analysis takes a magnitude limited microlensing survey into account, and
includes the effects of extinction. We show that, in the current magnitude
limited surveys, the probability that the source lies at the far side of the
bulge is larger than the probability that the source lies at the near side. We
then investigate the effects of extinction on the observed spectra of
microlensed sources. Kurucz model spectra and the observed extinctions towards
the Galactic bulge have been used to demonstrate that the microlensed sources
should clearly show the effects of extinction which, in turn, can be used as a
statistical measure of the contribution of the disk lenses and bulge lenses at
different depths. The spectra of the microlensed sources provide a unique probe
to derive the radial velocities of a sample which lies preferentially at the
far side of the Galactic bulge. The radial velocities, coupled with the
microlensing time scales, can thus be useful in studying the 3-dimensional
kinematics of the Galactic bulge.


title: Apparent and actual galaxy cluster temperatures

abstract:
  The redshift evolution of the galaxy cluster temperature function is a
powerful probe of cosmology. However, its determination requires the
measurement of redshifts for all clusters in a catalogue, which is likely to
prove challenging for large catalogues expected from XMM--Newton, which may
contain of order 2000 clusters with measurable temperatures distributed around
the sky. In this paper we study the apparent cluster temperature, which can be
obtained without cluster redshifts. We show that the apparent temperature
function itself is of limited use in constraining cosmology, and so concentrate
our focus on studying how apparent temperatures can be combined with other
X-ray information to constrain the redshift. We also briefly study the
circumstances in which non-thermal spectral features can give redshift
information.


title:
A Giant Bipolar Shell around the WO star in the Galaxy IC 1613:
  Structure and Kinematics

abstract:
  Observations of the nebula associated with the WO star in the galaxy IC 1613
are presented. The observations were carried out with a scanning Interferometer
Fabry-Perot in H_alpha at the 6m Special Astrophysical Observatory telescope;
narrow-band H_alpha and [OIII] images were obtained with the 4-m KPNO
telescope. The monochromatic H_alpha image clearly reveals a giant bipolar
shell structure outside the bright nebula S3. The sizes of the southeastern and
northwestern shells are 112x77 pc and (186-192)x(214-224) pc, respectively. We
have studied the object's kinematics for the first time and found evidence for
expansion of both shells. The expansion velocities of the southeastern and
northwestern shells exceed 50 and 70 km/s, respectively. We revealed a
filamentary structure of the shells and several compact features in the S3
core. A scenario is proposed for the formation of the giant bipolar structure
by the stellar wind from the central WO star located at the boundary of a dense
``supercavity'' in the galaxy's H I distribution.


title: Are Radio Pulsars Strange Stars ?

abstract:
  A remarkably precise observational relation for pulse core component widths
of radio pulsars is used to derive stringent limits on pulsar radii, strongly
indicating that pulsars are strange stars rather than neutron stars. This is
achieved by inclusion of general relativistic effects due to the pulsar mass on
the size of the emission region needed to explain the observed pulse widths,
which constrain the pulsar masses to be less than 2.5 Solar masses and radii to
be smaller than 10.5 km.


title: The history of starburst galaxies

abstract:
  Dusty galaxies with luminosities in excess of 10^11 solar luminosities have
been detected out to redshifts of about unity by the Infrared Space Observatory
(ISO), and to higher redshifts using millimetre(mm)- and submm-wave cameras on
ground-based telescopes. The integrated properties of these more distant
galaxies are also constrained by measurements of the intensity of the
submm-wave background radiation. While it is generally unclear whether their
energy is released by gravitational accretion or by star formation,
circumstantial evidence favours star formation. Unless these high-redshift
galaxies are extremely massive, which is not expected from standard models of
galaxy evolution, this luminosity cannot be sustained for more than a fraction
of a Hubble time, and so they are undergoing some sort of `bursting' behaviour.
The interpretation and analysis of this population is discussed, and the key
observations for deriving a robust history of their evolution, which is likely
to be the history of starburst activity, are highlighted.


title:
Metal abundance of the eclipsing binary YZ Cas: discrepancy between
  atmospheric determinations for the Am component

abstract:
  We review current and new estimates of the eclipsing binary YZ Cassiopeiae
metallicity (Z). Since the individual components cover a quite large range of
mass (1.35-2.31 Solar masses), YZ Cas is potentially one of the best stellar
laboratories to understand the structure and evolution of 1 to 2 Solar masses
stars. The derivation of Z from IUE spectra, as well as from photometric
indices, provides the chemical composition of the atmosphere (Z_{atmospheric}),
while the fit of evolutionary tracks provides the initial chemical composition
(Z_{initial}). While a disagreement is expected between Z_{atmospheric} and
Z_{initial} because the primary component is an Am star (one expects
Z_{atmospheric} to be larger), we find some unexpected discrepancy between
atmospheric determinations of Z for this star.


title:
Constraining the black hole mass and accretion rate in the narrow-line
  Seyfert 1 RE J1034+396

abstract:
  We present a comprehensive study of the spectrum of the narrow-line Seyfert 1
galaxy RE J1034+396, summarizing the information obtained from the optical to
X-rays with observations from the William Herschel 4.2m Telescope (WHT), the
Hubble Space Telescope, the Extreme UltraViolet Explorer, ROSAT, ASCA and
BeppoSAX. The BeppoSAX spectra reveal a soft component which is
well-represented by two blackbodies with kT of about 60 eV and 160 eV,
mimicking that expected from a hot, optically-thick accretion disc around a
low-mass black hole. This is borne out by our modeling of the optical to X-ray
nuclear continuum, which constrains the physical parameters of a NLS1 for the
first time. The models demonstrate that RE J1034+396 is likely to be a system
with a nearly edge-on accretion disk (60 to 75 degrees from the disk axis),
accreting at nearly Eddington rates (0.3 to 0.7 L_edd) onto a low mass (about 2
million solar masses) black hole (abridged).


title:
Large-scale distribution and spectral properties of galaxies in the
  Shapley Concentration

abstract:
  We present the results of a redshift survey of both cluster and intercluster
galaxies in the central part of the Shapley Concentration, the richest
supercluster of clusters in the nearby Universe, consisting of ~2000 radial
velocities.
  We estimate the total overdensity in galaxies of the supercluster and its
mass and we discuss the cosmological implications of these results.
  Moreover, using a Principal Components Analysis technique, we study the
influence of the cluster and supercluster dynamics on the galaxy spectral
morphology.


title:
The violent environment of the Shapley Concentration: a multiwavelength
  view

abstract:
  Rich superclusters are the ideal environment for the detection of cluster
mergings, because the high peculiar velocities induced by the enhanced local
density of the large-scale structure favour the cluster-cluster collisions, in
the same way as seen in the simulations.
  The Shapley Concentration supercluster represents a unique laboratory where
it is possible to follow cluster mergings and to test related astrophysical
consequences, as the formation of shocks, radio halos, relics and wide angle
tail radiosources, and the presence of galaxies with enhanced star formation.
  We present the results of an extensive multiwavelength survey of the central
part of the Shapley Concentration, with the use of optical spectra, radio and
X-ray data.


title: Spectra of thermally unstable slim discs

abstract:
  Thermal instability driven by radiation pressure might be relevant for
intrinsically bright accreting sources. The most promising candidate where this
instability seems to be at work is one of the two known galactic superluminal
sources, GRS 1915+105 (Belloni et al. 1997). In spite of being of relevance,
this scenario has not yet been confirmed by proper time-dependent modelling.
Non-linear time-dependent calculations performed by Szuszkiewicz and Miller
(1998) show that thermally unstable discs undergo limit-cycle behaviour with
successive evacuation and refilling of the central parts of the disc. This
evolution is very similar to the one proposed by Belloni et al. (1997) in their
phenomenological model. Further investigations are needed to confirm the
thermal instability being operational in this source. First of all the spectra
emitted from the disc during its evolution should be calculated and compared
with observations. Here such spectra are computed assuming local blackbody
emission from the best studied transonic disc model.


title:
A Large Eddy Simulation of Turbulent Compressible Convection:
  Differential Rotation in the Solar Convection Zone

abstract:
  We present results of two simulations of the convection zone, obtained by
solving the full hydrodynamic equations in a section of a spherical shell. The
first simulation has cylindrical rotation contours (parallel to the rotation
axis) and a strong meridional circulation, which traverses the entire depth.
The second simulation has isorotation contours about mid-way between cylinders
and cones, and a weak meridional circulation, concentrated in the uppermost
part of the shell.
  We show that the solar differential rotation is directly related to a
latitudinal entropy gradient, which pervades into the deep layers of the
convection zone. We also offer an explanation of the angular velocity shear
found at low latitudes near the top. A non-zero correlation between radial and
zonal velocity fluctuations produces a significant Reynolds stress in that
region. This constitutes a net transport of angular momentum inwards, which
causes a slight modification of the overall structure of the differential
rotation near the top. In essence, the {\it thermodynamics controls the
dynamics through the Taylor-Proudman momentum balance}. The Reynolds stresses
only become significant in the surface layers, where they generate a weak
meridional circulation and an angular velocity `bump'.


title: Radio-quiet quasar environments at 0.5 < z < 0.8

abstract:
  We have quantified the galaxy environments around a sample of 0.5 < z < 0.8
radio-quiet quasars using the amplitude of the spatial galaxy--quasar
correlation function, B_gq. The quasars exist in a wide variety of
environments, some sources are located in clusters as rich as Abell class 1--2
clusters, whereas others exist in environments comparable to the field. We find
that on average, the quasars prefer poorer clusters of approximately Abell
class 0, which suggests that quasars are biased tracers of mass compared to
galaxies.
  The mean B_gq for the sample is found to be indistinguishable from the mean
amplitude for a sample of radio-loud quasars matched in redshift and optical
luminosity. These observations are consistent with recent studies of the hosts
of radio-quiet quasars at low to intermediate redshifts, and suggest that the
mechanism for the production of powerful radio jets in radio-loud quasars is
controlled by processes deep within the active galactic nucleus itself, and is
unrelated to the nature of the hosts or their environments.


title: The Relativistic Precession Model for QPOs in Low Mass X-ray Binaries

abstract:
  The relativistic precession model for quasi periodic oscillations, QPOs, in
low mass X-ray binaries is reviewed. The behaviour of three simultaneous types
of QPOs is well matched in terms of the fundamental frequencies for geodesic
motion in the strong field of the accreting compact object for reasonable star
masses and spin frequencies. The model ascribes the higher frequency kHz QPOs,
the lower frequency kHz QPOs and the horizontal branch oscillations to the
Keplerian, periastron precession and nodal precession frequencies of matter
inhomogeneities orbiting close to the inner edge of the accretion disk. The
remarkable correlation between the centroid frequency of QPOs in both neutron
star and black hole candidate low mass X-ray binaries is very well fit by the
model. QPOs from low mass X-ray binaries might provide an unprecedented
laboratory to test general relativity in the strong field regime.