title: Implications of the Sample Rate on Large Space Telescopes

abstract:
  The frequency at which a large space telescope's (e.g. NGST's) detector chips
are read, or the sample rate, is tightly coupled to many hardware and
operational aspects of the telescope's instrument and data handling elements.
In this paper we discuss many of the drivers and important implications fo the
sample rate: the data rate to the ground; onboard computer storage, bandwidth,
and speed; the number of A->D chips, and therefore the overall size and power
requirements of the analog electronics; cryocabling requirements; and detector
noise and power. We discuss and parametrize these and other elements related to
sample rate. Finally, we discuss the implications of sample rate in the context
of achieving the most important science goals under the constraint of fixed
cost.


title:
CG J1720-67.8: A Detailed Analysis of Optical and Infrared Properties of
  a New Ultracompact Group of Galaxies

abstract:
  We present here optical spectroscopy and BVRJHK(s) photometry of the recently
discovered ultra-compact group of galaxies CG J1720-67.8. This work represents
a considerable extension of the preliminary results we presented in a previous
paper. Despite the complicated morphology of the group, a quantitative
morphological classification of the three brightest members of the group is
attempted based on photometric analysis. We find that one galaxy is consistent
with a morphological type S0, while the other two are most probably late-type
spirals that are already losing their identity due tothe interaction process.
Information on the star formation activity and dust content derived from both
spectroscopic data and optical and near-infrared colors are complemented with a
reconstruction of far-infrared (FIR) maps from IRAS raw data. Enhanced star
formation activity is revealed in all the group's members, including the
early-type galaxy and the extended tidal tail, along which several tidal dwarf
galaxy candidates are identified. The metallicity of the gaseous component is
investigated and photoionization models are applied to the three main galaxies
of the group, while a detailed study of the tidal dwarf candidates will appear
in a companion paper. Subsolar metal abundances are found for all the three
galaxies, the highest values being shown by the early-type galaxy (Z ~ 0.5
Zsolar).


title:
Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS
  2397a

abstract:
  Using the adaptive optics system, Hokupa'a, at Gemini-North, we have directly
imaged a companion around the UKIRT faint standard M8 star, LHS 2397a (FS 129)
at a separation of 2.96 AU. Near-Infrared photometry of the companion has shown
it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to
be M8. We also derive a substellar mass of the companion of 0.068 Msun,
although masses in the range (0.061-0.069) are possible, and the primary mass
as 0.090 Msun (0.089-0.094). Reanalysis of archival imaging from HST has
confirmed the secondary as a common proper motion object. This binary
represents the first clear example of a brown dwarf companion within 4 AU of a
low mass star and should be one of the first late L dwarfs to have a dynamical
mass. As part of a larger survey of M8-L0 stars, this object may indicate that
there is no ``brown dwarf desert'' around low mass primaries.


title:
Are Massive Neutrinos Responsible for the Accelerated Expansion of the
  Universe?

abstract: Paper withdrawn by author. New treatment is in preparation.


title:
Stellar collisions in galactic centers: black hole growth and color
  gradients

abstract:
  We study the effects of stellar collisions, particularly on feeding massive
black holes (BHs) and color gradients, in realistic galactic centers. We find
that the mass released by stellar collisions is not sufficient to account for
the present BH mass in galactic centers, especially in bright galaxies. This
study, together with the study by Magorrian & Tremaine (1999) on tidal
disruption of stars by massive BHs, implies that the material for BH growth
(especially in galaxies brighter than ~10^9 Lsun) can only come from other
sources, for example, the mass released by stellar evolution in the initial ~1
Gyr of the galaxy's lifetime, or the gas that sinks to the galactic center in a
galaxy merger. We also analyze how the color of a stellar system is affected by
collisions of stars. We find that collisions between main-sequence stars cannot
cause observable color gradients in the visible bands at projected radius
R>0.1" in M31, M32 and other nearby galactic centers. This result is consistent
with the lack of an observable color gradient in M32 at R>0.1". At even smaller
radii, the color differences caused by collisions between main-sequence stars
are at most 0.08 mag at R=0.02". The averaged blueing due to stellar collisions
in the region R<0.1" of M32 should not be larger than 0.06 mag in color index
U-V and 0.02 mag in V-I. The observed blueing in the center of the galaxy M31
(in a 0.14"x0.14" box) must be caused by some mechanism other than collisions
between main-sequence stars.


title:
Can radiative cooling and nongravitational heating explain
  simultaneously the global X-ray properties of clusters and the unresolved
  cosmic X-ray background ?

abstract:
  Using a simple analytic approach we address the question of whether radiative
cooling, nongravitational heating and cooling plus heating models can
simultaneously explain the observed global X-ray properties (entropy and X-ray
luminosity distributions) of groups and clusters and the residual soft X-ray
background (XRB) after discrete sources are removed. Within the framework of
typical cold dark matter structure formation characterized by an amplitude of
matter power spectrum sigma_8=0.9, it is argued that while radiative cooling
alone is able to marginally reproduce the entropy floor detected in the central
regions of groups and clusters, it is insufficient to account for the
steepening of the X-ray luminosity - temperature relation for groups and the
unresolved soft XRB. A phenomenological preheating model, in which either an
extra specific energy budget or an entropy floor is added to the hot gas in
groups and clusters, fails in the recovery of at least one of the X-ray
observed features. Finally, the soft XRB predicted by our combined model of
cooling plus heating exceeds the observational upper limits by a factor of ~2,
if the model is required to reproduce the observed entropy and X-ray luminosity
- temperature relationships of groups and clusters. If the discrepancy is not a
result of the oversimplification of our analytic models, this implies that
either our current understanding of the physical processes of the hot gas is
still incomplete, or the normalization of the present power spectrum has been
systematically overestimated. For the latter, both the X-ray properties of
groups and clusters and the XRB predicted by preheating model and cooling plus
heating model can be reconciled with the X-ray observations if a lower value of
the normalization parameter sigma_8 \approx 0.7 is assumed.


title: Dynamical Instabilities in Extrasolar Planetary Systems

abstract:
  Instabilities and strong dynamical interactions between multiple giant
planets have been proposed as a possible explanation for the surprising orbital
properties of extrasolar planetary systems. In particular, dynamical
instabilities seem to provide a natural mechanism for producing the highly
eccentric orbits seen in many systems. Previously, we performed numerical
integrations for the dynamical evolution of planetary systems containing two
giant planets of equal masses initially in nearly circular orbits very close to
the dynamical stability limit. We found the ratio of collisions to ejections in
these simulations was greater than the ratio of circular orbits to eccentric
orbits among the known extrasolar planets. Further, the mean eccentricity of
the planets remaining after an ejection was larger than the mean eccentricity
of the known extrasolar planets. Recently, we have performed additional
integrations, generalizing to consider two planets of unequal masses. Our new
simulations reveal that the two-planet scattering model can produce a
distribution of eccentricities consistent with the observed eccentricity
distribution for plausible mass distributions. Additionally, this model
predicts a maximum eccentricity of about 0.8, in agreement with observations.
Early results from simulations of three equal-mass planets also reveal a
reduced frequency of collisions and a broad range of final eccentricities for
the retained inner planet.


title: Nova Populations

abstract:
  In this article we review the current status of the stellar population
assignment for novae. Observations in the Milky Way and in external galaxies
point out the existence of two nova populations: fast and bright novae, mainly
originated from massive white dwarfs and associated with the `thin disk/spiral
arm' stellar population, and slow and faint novae, originated from lighter
white dwarfs and associated with `thick-disk/bulge' population.


title:
A Model of the Temporal Variability of Optical Light from Extrasolar
  Terrestrial Planets

abstract:
  The light scattered by an extrasolar Earth-like planet's surface and
atmosphere will vary in intensity and color as the planet rotates; the
resulting light curve will contain information about the planet's properties.
Since most of the light comes from a small fraction of the planet's surface,
the temporal flux variability can be quite significant, $\sim$ 10-100%. In
addition, for cloudless Earth-like extrasolar planet models, qualitative
changes to the surface (such as ocean fraction, ice cover) significantly affect
the light curve. Clouds dominate the temporal variability of the Earth but can
be coherent over several days. In contrast to Earth's temporal variability, a
uniformly, heavily clouded planet (e.g. Venus), would show almost no flux
variability. We present light curves for an unresolved Earth and for Earth-like
model planets calculated by changing the surface features. This work suggests
that meteorological variability and the rotation period of an Earth-like planet
could be derived from photometric observations. The inverse problem of deriving
surface properties from a given light curve is complex and will require much
more investigation.


title:
The Optical Gravitational Lensing Experiment. BVI Maps of Dense Stellar
  Regions. III. The Galactic Bulge

abstract:
  We present the VI photometric maps of the Galactic bulge. They contain VI
photometry and astrometry of about 30 million stars from 49 fields of 0.225
square degree each in the Galactic center region. The data were collected
during the second phase of the OGLE microlensing project. We discuss the
accuracy of data and present color-magnitude diagrams of selected fields
observed by OGLE in the Galactic bulge.
  The VI maps of the Galactic bulge are accessible electronically for the
astronomical community from the OGLE Internet archive.


title: Can We See the Shape of the Universe?

abstract:
  This is a written version of a talk given at the Fifth Friedmann Seminar on
recent work in Observational Cosmic Topology done in partial collaboration with
Armando Bernui. We address three relevant questions related to the search for
the size and shape of our Universe: (i) How do the actual observation of
multiple images of certain cosmic objects, e.g. galaxy clusters, constrain the
possible models for the shape of our Universe?, (ii) What kind of predictions
can be done once a pair of cosmic objects have been identified to be
topological images related by a translation?, and (iii) Is it possible to
determine if two regions of space are topologically identified, even when
distortions on the distributions of cosmic sources due to observational
limitations are not negligible? We give examples answering the first two
questions using the suggestion of Roukema and Edge that the clusters RXJ
1347.5-1145 and CL 09104+4109 might be topological images of the Coma cluster.
For the third question, we suggest a method based on the analysis of PSH's
noise correlations which seems to give a positive answer.


title: X-Ray Spectroscopy and Atomic Data

abstract:
  The Laboratory Astrophysics program employing the Lawrence Livermore National
Laboratory (LLNL) Electron Beam Ion Trap (EBIT) has been providing useful
atomic data in support of the x-ray missions Chandra and XMM-Newton. Major
achievements have been made for Fe L-shell ions in hot, collisional plasmas,
relevant to stellar coronae, supernova remnants, elliptical galaxies, and
galaxy clusters. Measurements for L-shell ions of other cosmiscally important
elements are also required, some of which are in the LLNL EBIT pipeline. On the
other hand, data for inner-shelll excited lines relevant to photoionized
plasmas near accretion sources are largely lacking. Even the wavelengths of
these lines are only poorly known, which severely limits their use for
diagnostics, despite the great potential.


title: R Aquarii spectra revisited by SUMA

abstract:
  We analyse the optical spectra and the UV spectral evolution of the jets and
of the HII region inside the R Aquarii binary system by the code SUMA which
consistently accounts for shock and photoionization. The temperature of the hot
star results 80,000 K as for a white dwarf. We find that the shock velocity in
the NE jet increased between 1983 and 1989. The spectral evolution between 1989
and 1991 of the SW jet indicates that a larger contribution from low
density-velocity matter affects the 1991 spectra. The evolution of the UV
spectra from 8/11/1980 to 26/5/1991 in the HII region indicates that the
reverse shock is actually a standing shock. The results obtained by modelling
the line spectra are cross-checked by the fit of the continuum SED. It is found
that a black-body temperature of 2800 K reproduces the radiation from the red
giant. A black-body emission component corresponding to 1000 K is emitted by
dust in the surrounding of the red giant. Model calculations confirm that the
radio emission is of thermal origin. We found that the NE jet bulk emission is
at a distance of about 2 (15) cm from the internal system, while the distance
of the SW jet bulk is about 6 (14) cm. The distance of the reverse shock from
the hot source in the internal region is < 9 (13) cm.


title:
Dust formation in winds of long-period variables. V. The influence of
  micro-physical dust properties in carbon stars

abstract:
  We present self-consistent dynamical models for dust-driven winds of
carbon-rich AGB stars. The models are based on the coupled system of
frequency-dependent radiation hydrodynamics and time-dependent dust formation.
We investigate in detail how the wind properties of the models are influenced
by the micro-physical properties of the dust grains that are required by the
description of grain formation. The choice of dust parameters is significant
for the derived outflow velocity, the degree of condensation and the resulting
mass loss rates of the models. In the transition region between models with and
without mass loss the choice ofmicro-physical parameters turns out to be very
significant for whether a particular set of stellar parameters will give rise
to a dust-driven mass loss or not. We also calculate near-infrared colors to
test how the dust parameters influence the observable properties of the models,
however, at this point we do not attempt to fit particular stars.


title:
The All Sky Automated Survey. Variable Stars in the 0h - 6h Quarter of
  the Southern Hemisphere

abstract:
  This paper describes the first part of the photometric data from the 9x9 deg
ASAS cameras monitoring the whole southern hemisphere in V-band. Data
acquisition and reduction pipeline is described and preliminary list of
variable stars is presented. Over 1,300,000 stars brighter than V=15 on 40,000
frames were analyzed and 3126 were found to be variable (1046 eclipsing, 778
regular pulsating, 132 Mira and 1170 other, mostly SR, IR and LPV stars).
Periodic light curves have been classified using the fully automated algorithm,
which is described in detail. Basic photometric properties are presented in the
tables and thumbnail light curves are printed for reference. All photometric
data is available over the INTERNET at
http://www.astrouw.edu.pl/~gp/asas/asas.html or
http://archive.princeton.edu/~asas .


title: A New General Relativistic Cosmology

abstract:
  In this work, we outline a new general relativistic cosmology. In this
cosmology, the universe originates in the infinite past from sparsely
distributed neutral matter and ends in the infinite future as a hot,
relativistic plasma. The spatial distribution of matter on the "initial"
hyper-surface is {\em arbitrary}. Hence, observed structures can arise in this
cosmology from suitable "initial" density contrast. The red-shifts of different
objects in this cosmology are indicative of their different states of collapse
and need not possess any correlation to their distance from the observer.
Further, the microwave background radiation arises in this cosmology as
thermalized radiation from all the radiating matter in the universe. This
cosmology predicts that the temperature of the microwave background increases
with time. Thus, any conclusive evidence that the temperature of the Microwave
Background Radiation was more in the past can falsify this cosmology.


title:
Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators
  among Subdwarf B Stars

abstract:
  During the course of an ongoing CCD monitoring program to investigate
low-level light variations in subdwarf B (sdB) stars, we have serendipitously
discovered a new class of low amplitude, multimode sdB pulsators with periods
of the order of an hour. These periods are more than a factor of ten longer
than those of previously known multimode sdB pulsators (EC 14026 stars),
implying that they are due to gravity modes rather than pressure modes. The
longer period pulsators are found only among cooler sdB stars, where they are
surprisingly common. The iron opacity instability that drives the short period
EC 14026 stars is effective only in hot sdB's, leaving the driving mechanism
for the deeper gravity modes in cool sdB's currently unknown. We present the
first observational results for our newly identified sdB variables, and discuss
possible implications.


title: Particle acceleration in rotating and shearing jets from AGN

abstract:
  We model the acceleration of energetic particles due to shear and centrifugal
effects in rotating astrophysical jets. The appropriate equation describing the
diffusive transport of energetic particles in a collisionless, rotating
background flow is derived and analytical steady state solutions are discussed.
In particular, by considering velocity profiles from rigid, over flat to
Keplerian rotation, the effects of centrifugal and shear acceleration of
particles scattered by magnetic inhomogeneities are distinguished. In the case
where shear acceleration dominates, it is confirmed that power law particle
momentum solutions $f(p) \propto p^{-(3+\alpha)}$ exist, if the mean scattering
time $\tau_c \propto p^{\alpha}$ is an increasing function of momentum. We show
that for a more complex interplay between shear and centrifugal acceleration,
the recovered power law momentum spectra might be significantly steeper but
flatten with increasing azimuthal velocity due to the increasing centrifugal
effects. The possible relevance of shear and centrifugal acceleration for the
observed extended emission in AGN is demonstrated for the case of the jet in
the quasar 3C273.


title:
Searching for Stars in Compact High-Velocity Clouds. I First Results
  from VLT and 2MASS

abstract:
  We investigate the hypothesis that compact high-velocity clouds (CHVC) are
the "missing" dwarf galaxies of the Local Group, by searching them for
populations of resolved stars. To this end we conducted two distinct tests
based on optical and near-infrared single-star photometry. The optical and the
near-infrared experiments complement one another; the optical data help us to
rule out distant populations but they are restricted to the central regions of
the gas distributions, whereas the near-infrared photometry allows us to set
limits on nearby populations spread over the typical cloud size. First, we
discuss deep optical single-star photometry of five CHVCs in the V and I
filters, obtained with the FORS instrument at the Very Large Telecope (VLT). We
find that their optical colour-magnitude diagrams are indistinguishable from
that of a population of Galactic stars, and attribute all of the resolved stars
to Galactic foreground. We present simulations which address the question of
how much of a "normal" dwarf-galaxy type population we might hide in the data.
A Kolmogorov-Smirnov test allows us to set very stringent limits on the absence
of a resolved stellar population in CHVCs. Second, we also culled near infrared
single-star photometry in the J, H, and K_S bands for four of the CHVCs from
the Two Micron All Sky Survey (2MASS). The infrared data do not reveal any
stellar contents in the CHVCs which resembles that of nearby dwarf galaxies
either, and are explained with Galactic foreground as well. We interpret our
null detections to indicate that the five CHVCs investigated by us do not host
an associated stellar content which is similar to that of the known dwarf
galaxies of the Local Group. These CHVCs are very likely pure hydrogen clouds
in which no star formation has taken place over cosmic time.


title:
A simultaneous XMM-Newton and BeppoSAX observation of the archetypal
  Broad Line Seyfert 1 galaxy NGC 5548

abstract:
  We report the spectral analysis of a long XMM-Newton observation of the
well-studied, moderate luminosity Broad Line Seyfert 1 galaxy NGC 5548. The
source was at an historically average brightness and we find the hard (3-10
keV) spectrum can be well fitted by a power law of photon index gamma ~ 1.75,
together with reflection. The only feature in the hard X-ray spectrum is a
narrow emission line near 6.4 keV, with an equivalent width of ~ 60 eV. The
energy and strength of this line is consistent with fluorescence from `neutral'
iron distant from the central continuum source. We find no evidence for a broad
Fe K line, with an upper limit well below previous reports, suggesting the
inner accretion disc is now absent or highly ionised. The addition of
simultaneous BeppoSAX data allows the analysis to be extended to 200 keV,
yielding important constraints on the total reflection. Extrapolation of the
hard X-ray power law down to 0.3 keV shows a clear `soft excess' below ~ 0.7
keV. After due allowance for the effects of a complex warm absorber, measured
with the XMM-Newton RGS, we find the soft excess is better described as a
smooth upward curvature in the continuum flux below ~ 2 keV. The soft excess
can be modelled either by Comptonised thermal emission or by enhanced
reflection from the surface of a highly ionised disc.


title:
Radiative pumping of 1612 MHz OH masers: OH/IR sources with IRAS LRS
  spectra and 34.6 micrometer absorption feature

abstract:
  The population inversion which leads to the 1612 MHz OH maser emission has
long been thought to be radiatively pumped. Since OH rotational lines involved
in this pumping scheme lie in the far-infrared they became observable only
after the launch of the ISO satellite. With the aim to investigate the pumping
conditions of the 1612 MHz OH maser emission in more details we have searched
the ISO Archive for SWS observations around 34.6 um of 1024 OH/IR sources with
IRAS LRS spectra from compilation of Chen et al. (2001). Surprisingly, among 81
OH/IR sources which have appropriate SWS data only already reported objects: VY
CMa, IRC+10420 and the Galactic center, show clear 34.6 um absorption line. We
discuss possible reasons for non-detection of this pumping line.


title:
New Evolutionary Synthesis Tool for Modelling Young Star Clusters in
  Merging Galaxies

abstract:
  Globular cluster systems (GCSs) are vital tools for investigating the violent
star formation histories of their host galaxies. This violence could e.g. have
been triggered by galaxy interactions or mergers. The basic observational
properties of a GCS are its luminosity function and color distributions (number
of clusters per luminosity resp. color bin). A large number of observed GCSs
show bimodal color distributions, which, by comparison with evolutionary
synthesis (ES) models, can be translated into bimodality in metallicity and/or
age. An additional uncertainty comes into play when one considers extinction
within the host galaxy. These effects can be disentangled either by obtaining
spectroscopic data for the clusters or by imaging observations in at least four
passbands. This allows us then to discriminate between various formation
scenarios of GCSs, e.g. the merger scenario by Ashman & Zepf and the
multi-phase collapse model by Forbes et. al.. Young and metal-rich star cluster
populations are seen to form in interacting and merging galaxies. We analyse
multi-wavelength broad-band observations of these young cluster systems
provided by the ASTROVIRTEL project.


title:
Determination of the properties of the central engine in microlensed
  QSOs

abstract:
  We study a recently observed gravitational microlensing peak in the V-band
light curve of Q2237+0305A using a relatively simple, but highly consistent
with the data (the best-fit reduced \chi^2 is very close to 1), physical model.
The source quasar is assumed to be a Newtonian geometrically-thin and
optically-thick accretion disk. The disk has an arbitrary orientation, and both
blackbody and greybody emission spectra are considered. When the
electron-photon scattering plays a role, the greybody spectrum will be a
simplified version of the exact one. In our model the microlensing variability
result from the source crossing a caustic straight line. The main goal is to
estimate the black hole mass and the mass accretion rate in QSO 2237+0305 as
well as to discuss the power and the weakness of the technique, some possible
improvements, and the future prospects from multifrequency monitoring of new
microlensing peaks. We also put into perspective the new methodology and the
results on the central engine in QSO 2237+0305. From the fitted microlensing
parameters and reasonable dynamical/cosmological constraints, it is concluded
that QSO 2237+0305 harbours a central massive black hole: 10^7 M_Sun < M < 6
10^8 M_Sun. While the information about the central dark mass is very
interesting, the mass accretion rate is not so well constrained. The typical
values of the disk luminosity/Eddington luminosity ratio are in the
(1-20)*\epsilon range, where \epsilon \leq 1 is the emissivity relative to a
blackbody and the highest L/L_{Edd} ratio corresponds to the largest deflector
motion. Therefore, in order to verify L/L_{Edd} \leq 1, a relatively small
projected peculiar motion of the lens galaxy and a greybody emission seem to be
favored.


title: ASTRO-F - Super IRAS - The All Sky Infra-Red Survey

abstract:
  We review the next generation Japanese infrared space mission, ASTRO-F.
ASTRO-F will be the first survey of the entire sky at infrared wavelengths
since the IRAS mission almost 20 years ago. ASTRO-F will survey the entire sky
in 4 far-infrared bands from 50-200microns and 2 mid-infrared bands at 9 and
20microns to sensitivities of 10-1000 times deeper than the IRAS satellite at
angular resolutions of 25-45arcsec (c.f. IRAS 2-5arcmins). ASTRO-F can be
considered a SUPER-IRAS. Using the galaxy evolution model of Pearson (2001) we
produce expected numbers of sources under 3 different cosmological world
models. We predict that ASTRO-F will detect of the order of 10's millions of
sources in the far-infrared wavelength bands, most of which will be dusty
LIG/ULIGs of which as many as half will lie at redshifts greater than unity. We
produce number-redshift distributions, flux-redshift and colour-colour diagrams
for the survey and discuss various segregation and photometric redshift
techniques. Furthermore, we investigate the large scale structure scales that
will be accessed by ASTRO-F, discovering that ASTRO-F and SIRTF-SWIRE probe
both different scales and redshift domains and concluding that the 2 missions
will supplement rather than supplant one another.


title: Asymptotic models of meridional flows in thin viscous accretion disks

abstract:
  We present the results of numerical integrations yielding the structure of
and meridional flow in axisymmetric thin viscous accretion disk models. The
solutions are obtained by simplifying and approximating first the equations,
using systematic asymptotic expansions in the small parameter $\epsilon$,
measuring the relative disk thickness. The vertical structure is solved
including radiative transfer in the diffusion approximation. Carrying out the
expansion to second order in $\epsilon$ we obtain, for low enough values of the
viscosity parameter $\alpha$, solutions containing {\em backflows}. These
solutions are similar to the results first found by Urpin (1984), who used
approximations that are only valid for large radii and the asymptotic
analytical solutions of Klu\'zniak & Kita (1997), valid only for polytropic
disks. Our results may be important for several outstanding issues in accretion
disk theory.


title: Molecular gas freeze-out in the pre-stellar core L1689B

abstract:
  C17O (J=2-1) observations have been carried out towards the pre-stellar core
L1689B. By comparing the relative strengths of the hyperfine components of this
line, the emission is shown to be optically thin. This allows accurate CO
column densities to be determined and, for reference, this calculation is
described in detail. The hydrogen column densities that these measurements
imply are substantially smaller than those calculated from SCUBA dust emission
data. Furthermore, the C17O column densities are approximately constant across
L1689B whereas the SCUBA column densities are peaked towards the centre. The
most likely explanation is that CO is depleted from the central regions of
L1689B. Simple models of pre-stellar cores with an inner depleted region are
compared with the results. This enables the magnitude of the CO depletion to be
quantified and also allows the spatial extent of the freeze-out to be firmly
established. We estimate that within about 5000 AU of the centre of L1689B,
over 90% of the CO has frozen onto grains. This level of depletion can only be
achieved after a duration that is at least comparable to the free-fall
timescale.


title:
Ten eclipsing binaries in the Small Magellanic Cloud: fundamental
  parameters and SMC distance

abstract:
  We present the first results of an observational programme to measure the
fundamental parameters of over 100 eclipsing binaries in the Small Magellanic
Cloud (SMC). The spectroscopic data were obtained by using the 2dF multi-object
spectrograph on the 3.9-m Anglo-Australian Telescope, and are used in
conjunction with photometry from the OGLE database of SMC eclipsing binaries.
Ten systems are discussed in this first paper. Three are detached early-B
binaries, six are in a semi-detached configuration, and one is in a marginal
contact state. We conclude that the semi-detached systems are undergoing the
slow mass-transfer phase of case-A binary evolution, in which the mass donor
has reached its Roche lobe while still on the main sequence. Each system
provides a primary distance indicator. By constructing a new calibration
between spectral type and temperature for O and early B stars, we find a mean
distance modulus to the SMC of 18.89 +- 0.04 (statistical) +- 0.10
(systematic). This value represents one of the most precise determinations to
date of the distance to the SMC.


title:
An Exact General-Relativity Solution for the Motion and Intersections of
  Self-Gravitating Shells in the Field of a Massive Black Hole

abstract:
  The motion with intersections of relativistic gravitating shells in the
Schwarzschild gravitational field of a central body is considered. Formulas are
derived for calculating parameters of the shells after intersection via their
parameters before intersection. Such special cases as the Newtonian
approximation, intersections of light shells, and intersections of a test shell
with a gravitating shell are also considered. The ejection of one of the shells
to infinity in the relativistic region is described. The equations of motion
for the shells are analyzed numerically.


title: Astrophysics with High Energy Gamma Rays

abstract:
  Recent results, the present status and the perspectives of high energy
gamma-ray astronomy are described. Since the satellite observations by the
Compton Gamma Ray Observatory and its precursor missions have been reviewed
extensively, emphasis is on the results from the ground-based gamma-ray
telescopes. They concern the physics of Pulsar Nebulae, Supernova Remnants in
their assumed role as the Galactic sources of Cosmic Rays, Jets from Active
Galactic Nuclei, and the Extragalactic Background radiation field due to stars
and dust in galaxies. Since the gamma-ray emission is nonthermal, this kind of
astronomy deals with the pervasive high-energy nonequilibrium states in the
Universe. The present build-up of larger and more sensitive instruments, both
on the ground and in space, gives fascinating prospects also for observational
cosmology and astroparticle physics. Through realistically possible further
observational developments at high mountain altitudes a rapid extension of the
field is to be expected.


title:
The Digitized Second Palomar Observatory Sky Survey (DPOSS) II:
  Photometric Calibration

abstract:
  We present the photometric calibration technique for the Digitized Second
Palomar Observatory Sky Survey (DPOSS), used to create seamless catalogs of
calibrated objects over large sky areas. After applying a correction for
telescope vignetting, the extensive plate overlap regions are used to transform
sets of plates onto a common instrumental photometric system. Photometric
transformations to the Gunn gri system for each plate, for stars and galaxies,
are derived using these contiguous stitched areas and an extensive CCD imaging
library obtained for this purpose. We discuss the resulting photometric
accuracy, survey depth, and possible systematic errors.


title:
Does the proton-to-electron mass ratio vary in the course of
  cosmological evolution?

abstract:
  The possible cosmological variation of the proton-to-electron mass ratio was
estimated by measuring the H_2 wavelengths in the high-resolution spectrum of
the quasar Q~0347-382. Our analysis yielded an estimate for the possible
deviation of \mu value in the past, 10 Gyr ago: for the unweighted value
$\Delta \mu / \mu = (3.0\pm2.4)\times10^{-5}$; for the weighted value \[ \Delta
\mu / \mu = (5.02\pm1.82)\times10^{-5}\] Since the significance of the both
results does not exceed 3$\sigma$, further observations are needed to increase
the statistical significance. In any case, this result may be considered as the
most stringent estimate on an upper limit of a possible variation of \mu (95%
C.L.): \[ |\Delta \mu / \mu| < 8\times 10^{-5} \] This value serves as an
effective tool for selection of models determining a relation between possible
cosmological deviations of the fine-structure constant \alpha and the
elementary particle masses (m$_p$, m$_e$, etc.).


title:
Long-Term, Continuous Monitoring of the Broad Line Radio Galaxies 3C
  390.3 and 3C 120 With the Rossi X-Ray Timing Explorer

abstract:
  We present a study of the flux and spectral variability of the two broad-line
radio galaxies (BLRGs) 3C 390.3 and 3C 120, observed almost daily with RXTE for
nearly two months each in 1996 and 1997, respectively. Our original motivation
for this study was to search for systematic differences between BLRGs and their
radio-quiet counterparts, the Seyfert galaxies, whose temporal and spectral
behavior is better studied. We find that both 3C 390.3 and 3C 120 are highly
variable, but in a different way, and quantify this difference by means of a
structure function analysis. 3C 390.3 is significantly more variable than 3C
120, despite its jet larger inclination angle, implying either that the X-ray
variability is not dominated by the jet or that two different variability
processes are simultaneously at work in 3C 390.3. We performed an
energy-selected and time-resolved analysis based on the fractional variability
amplitude and found that the variability amplitude of both objects is strongly
anticorrelated with the energy. This last result, along with the correlated
change of the photon index with the X-ray continuum flux, can be qualitatively
explained within the scenario of thermal Comptonization, generally invoked for
radio-quiet active galaxies. Moreover, the time-resolved and energy-selected
fractional variability analyses show a trend opposite to that observed in
jet-dominated AGN (blazars), suggesting only a minor contribution of the jet to
the X-ray properties of BLRGs. Time-averaged spectral analysis indicates the
presence of a strong, resolved iron line with centroid at 6.4 keV and a weak
reflection component in both objects. The overall PCA+HEXTE spectra are best
fitted with the constant density ionization model of Ross & Fabian, but with a
modest ionization parameter(abridged).


title: Thermal components in the early X-ray afterglow of GRBs

abstract:
  The possible presence of thermal components in the early X-ray afterglows of
gamma-ray bursts is investigated. We discuss both the presence of a thermal
continuum and, in particular, of collisional X-ray emission lines. We compute
the predicted luminosity by a thin plasma for a range of metallicities for the
continuum and the K_alpha lines of the elements Mg, Si, S, Ar, Ca and Fe. We
show that light travel effects are dominant in the determination of the thermal
continuum and line luminosities, and derive the relevant equations. We conclude
that thermal lines and continua are unlikely to dominate the early afterglow of
GRBs, unless the explosion site is surrounded by a very massive and extremely
clumped shell of material. Such conditions are difficult to envisage in the
close environment of GRB progenitor, unless they are excited by some strong
precursor activity, like in the Supranova scenario.


title: A Catalogue of infrared star clusters and stellar groups

abstract:
  We compiled a catalogue of infrared star clusters in the Galaxy, which are
most of them embedded. It condenses the growing literature information. We also
include in the sample infrared stellar groups which are less dense than star
clusters, such as those embedded in the dark clouds Taurus-Auriga and Chamaleon
I. We provide galactic and equatorial coordinates, angular dimensions,
different designations and related objects such as nebulae. A total of 189
infrared clusters and 87 embedded stellar groups are included. A fraction of 25
% of the embedded clusters are projected close to each other in pair or triplet
systems, indicating that multiplicity plays an important role in star cluster
formation.


title: CMB observations with the Cosmic Background Imager (CBI) Interferometer

abstract:
  We review the recently published results from the CBI's first season of
observations. Angular power spectra of the CMB were obtained from deep
integrations of 3 single fields covering a total of 3 deg^2 and 3 shallower
surveys of overlapping (mosaiced) fields covering a total of 40 deg^2. The
observations show a damping of the anisotropies at high-l as expected from the
standard scenarios of recombination. We present parameter estimates obtained
from the data and discuss the significance of an excess at l>2000 observed in
the deep fields.


title:
Particle Accelerators in the Hot Spots of the Radio Galaxy 3C445 Imaged
  With the VLT

abstract:
  Hot spots (HSs) are regions of enhanced radio emission produced by supersonic
jets at the tip of the radio lobes of powerful radiosources. Obtained with the
Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C445 show
bright knots embedded in diffuse optical emission distributed along the post
shock region created by the impact of the jet into the intergalactic medium.
  The observations reported here confirm that relativistic electrons are
accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the
diffuse emission tracing the rims of the front shock and the multiple knots
demonstrate the presence of additional continuous re-acceleration processes of
electrons (Fermi-II).


title:
The Cosmic Microwave Background Anisotropy Power Spectrum measured by
  Archeops

abstract:
  We present a determination by the Archeops experiment of the angular power
spectrum of the cosmic microwave background anisotropy in 16 bins over the
multipole range l=15-350. Archeops was conceived as a precursor of the Planck
HFI instrument by using the same optical design and the same technology for the
detectors and their cooling. Archeops is a balloon-borne instrument consisting
of a 1.5 m aperture diameter telescope and an array of 21 photometers
maintained at ~100 mK that are operating in 4 frequency bands centered at 143,
217, 353 and 545 GHz. The data were taken during the Arctic night of February
7, 2002 after the instrument was launched by CNES from Esrange base (Sweden).
The entire data cover ~ 30% of the sky.This first analysis was obtained with a
small subset of the dataset using the most sensitive photometer in each CMB
band (143 and 217 GHz) and 12.6% of the sky at galactic latitudes above 30
degrees where the foreground contamination is measured to be negligible. The
large sky coverage and medium resolution (better than 15 arcminutes) provide
for the first time a high signal-to-noise ratio determination of the power
spectrum over angular scales that include both the first acoustic peak and
scales probed by COBE/DMR. With a binning of Delta(l)=7 to 25 the error bars
are dominated by sample variance for l below 200. A companion paper details the
cosmological implications.


title: Cosmological constraints from Archeops

abstract:
  We analyze the cosmological constraints that Archeops places on adiabatic
cold dark matter models with passive power-law initial fluctuations. Because
its angular power spectrum has small bins in l and large l coverage down to
COBE scales, Archeops provides a precise determination of the first acoustic
peak in terms of position at multipole l_peak=220 +- 6, height and width. An
analysis of Archeops data in combination with other CMB datasets constrains the
baryon content of the Universe, Omega(b)h^2 = 0.022 (+0.003,-0.004), compatible
with Big-Bang nucleosynthesis and with a similar accuracy. Using cosmological
priors obtainedfrom recent non-CMB data leads to yet tighter constraints on the
total density, e.g. Omega(tot)=1.00 (+0.03,-0.02) using the HST determination
of the Hubble constant. An excellent absolute calibration consistency is found
between Archeops and other CMB experiments, as well as with the previously
quoted best fit model.The spectral index n is measured to be 1.04 (+0.10,-0.12)
when the optical depth to reionization, tau, is allowed to vary as a free
parameter, and 0.96 (+0.03,-0.04) when tau is fixed to zero, both in good
agreement with inflation.


title: The double outburst of the unique object V838 Mon

abstract:
  We present spectroscopic and photometric observations of the recent peculiar
outburst of V838 Mon, carried out at Rozhen and Torun observatories. Our data
cover a period of three months beginning just before the second eruption. The
evolution of the outburst is divided into four phases. The changes of
particular spectral features for each of these phases are shortly discussed.


title:
Resolving the Source Populations that Contribute to the X-ray
  Background: The 2 Ms Chandra Deep Field-North Survey

abstract:
  With ~2 Ms of Chandra exposure, the Chandra Deep Field-North (CDF-N) survey
provides the deepest view of the Universe in the 0.5-8.0 keV band. Five hundred
and three (503) X-ray sources are detected down to on-axis 0.5-2.0 keV and 2-8
keV flux limits of ~1.5x10^{-17} erg cm^{-2} s^{-1} and ~1.0x10^{-16} erg
cm^{-2} s^{-1}, respectively. These flux limits correspond to L_{0.5-8.0
keV}~3x10^{41} erg s^{-1} at z=1 and L_{0.5-8.0 keV}~2x10^{43} erg s^{-1} at
z=6; thus this survey is sensitive enough to detect starburst galaxies out to
moderate redshift and Seyfert galaxies out to high redshift. We present the
X-ray observations, describe the broad diversity of X-ray selected sources, and
review the prospects for deeper Chandra exposures.


title: X-rays from the High-Redshift Universe: The Chandra view

abstract:
  The study of the X-ray properties of z>4 quasars has grown substantially over
the last few years, mostly thanks to Chandra. Here we focus on (1) the average
X-ray properties of an optically selected, luminous sample of nine z>4 Palomar
Digital Sky Survey quasars recently observed by Chandra, and (2) the X-ray
spectral properties of three z>4 AGNs in the Chandra Deep Field-North (CDF-N)
using the 2 Ms exposure.


title:
The AGN Source Population in the Chandra Deep Field-North Survey:
  Constraints from X-ray Spectroscopy and Variability

abstract:
  We briefly report here on our ongoing X-ray spectroscopy and variability
analyses of 136 faint X-ray sources discovered in the 2 Ms Chandra Deep Field
North observations spanning 1.4x10-15 to 2x10-13 ergs s-1 cm-2. Most sources
are adequatley fitted with a simple intrinsic absorption plus power-law model,
although the resulting photon index is much lower than the canonical average
unabsorbed spectral slope found locally (suggesting additional spectral
complexity). Among the 136 sources, 7% show significant Fe (Ka) emission
features, with equivalent widths in the range 0.1-1.3 keV. Two of these
emission-line sources appear to be Compton thick. For the subset of sources
with redshifts, we also find that fewer than 10% are likely to be Compton
thick. Finally, ~60% of the sample show signs of long-term variability. This
fraction climbs to ~90% for the bright sources (>500 cnts) or BLAGN.


title:
Correlation between galaxies and QSO in the SDSS:na signal from
  gravitational lensing magnification?

abstract:
  We report a detection of galaxy-QSO cross-correlation w_GQ in the Sloan
Digital Sky Survey (SDSS) Early Data Release (EDR) over 0.2-30 arc-minute
scales. We cross-correlate galaxy samples of different mean depths r'=19-22
(z_G =0.15-0.35) with the main QSO population (i'<19.1) at mean z_Q=1.6. We
find significant positive correlation in all cases except for the faintest
QSOs, as expected if the signal were due to weak lensing magnification. The
amplitude of the signal on arc-minute scales is about 20%. This is a few times
larger than currently expected from weak lensing in LCDM but confirms, at a
higher significance, previous measurements by several groups. When compared to
the galaxy-galaxy correlation w_GG, a weak lensing interpretation indicates a
strong and steep non-linear amplitude for the underlaying matter fluctuations:
sigma=400 on scales of 0.2 Mpc/h, in contradiction with non-linear modeling of
LCDM fluctuations. We also detect a normalized skewness (galaxy-galaxy-QSO
correlation) of S_3=21 +/-6 at z=0.15 (S_3= 14 +/- 4 at z=0.35), which several
sigma low, as compared to LCDM expectations. These observational trends can be
reconciled with lensing in a flat Lambda universe with sigma_8=1, provided the
linear spectrum is steeper (n = 1) than in the LCDM model on these small
(cluster) scales. Under this interpretation, the galaxy distribution traces the
matter variance with an amplitude that is 100 times smaller: ie galaxies are
anti-bias with b=0.1 on small scales, increasing to b=1 at 10 Mpc/h.


title:
A multiwavelength vision of star forming regions: What does lambda_1
  know about lambda_2?

abstract:
  In this contribution I show the physical limitations to the application of
standard synthesis models from 0 to 10 Gyr. I also present the multiwavelength
spectrum (from gamma-rays to radio) of young star forming regions based on
evolutionary population synthesis models that takes into account the
stochasticity of the star formation proces. I show how the correlation of
different observables can allow to establish a better understanding of the star
formation processes. Finally I compare the spectral energy distribution of AGNs
and star forming regions and I show the possible connection of Star Forming
Galaxies with Seyfert 2 AGNs.


title: Constraining the evolution of young radio-loud AGN

abstract:
  GPS and CSS radio sources are the objects of choice to investigate the
evolution of young radio-loud AGN. Previous investigations, mainly based on
number counts and source size distributions, indicate that GPS/CSS sources
decrease significantly in radio power when evolving into old, extended objects.
We suggest this is preceded by a period of increase in radio luminosity, which
lasts as long as the radio source is confined within the core-radius of its
host galaxy. We have selected a sample of nearby compact radio sources,
unbiased by radio spectrum, to determine their radio luminosity function, size
distribution, dynamical ages, and emission line properties in a complete and
homogeneous way. First results indicate that the large majority of objects
(>80%) exhibit classical GPS/CSS radio spectra, and show structures consistent
with the being compact double, or compact symmetric objects. This sample
provides and ideal basis to further test and constrain possible evolution
scenarios, and to investigate the relation between radio spectra and
morphologies, orientation and Doppler boosting in samples of young radio-loud
AGN, in an unbiased way.


title: Galaxies and Intergalactic Matter at Redshift z~3: Overview

abstract:
  We present the first results from a survey of the relative spatial
distributions of galaxies, intergalactic neutral hydrogen, and intergalactic
metals at high redshift. We obtained high-resolution spectra of 8 bright QSOs
at 3.1<z<4.1 and spectroscopic redshifts for 431 Lyman-break galaxies (LBGs) at
slightly lower redshifts. Comparing the locations of galaxies to the absorption
lines in the QSO spectra shows that the intergalactic medium contains less
neutral hydrogen than the global average within r<0.5h^-1 comoving Mpc of LBGs
and more than average at slightly larger distances 1<r<5 h^-1 comoving Mpc. The
intergalactic medium within the largest overdensities at z~3, which will
presumably evolve into the intracluster medium by z~0, is rich in neutral
hydrogen and CIV. The lack of HI absorption at small distances from LBGs
appears unlikely to be produced solely by the Lyman continuum radiation they
emit; it may show that the galaxies' supernovae-driven winds maintain their
measured outflow velocities of ~600 km/s for a few hundred million years and
drive away nearby intergalactic gas. We present correlation functions of
galaxies with Lyman-alpha forest flux decrements, with CIV systems, and with
other galaxies. We describe the association of galaxies with damped Lyman-a
systems and with intergalactic HeII opacity. A strong observed correlation of
galaxies with intergalactic metals supports the idea that Lyman-break galaxies'
winds have enriched their surroundings.


title: Measuring the Influence of Supernovae at High Redshift

abstract:
  Supernovae play a large but poorly understood role in our attempts to explain
the evolution of the baryonic universe. Numerous observations throughout
astronomy cannot be explained if we neglect their influence, yet our
quantitative understanding of the ways in which supernovae affect the universe
remains remarkably poor. This is one of the most embarrassing gaps in our
knowledge of the cosmos, and planned telescopes and surveys will probably not
do much to fill it. The problem is that these surveys will be optimized to
observe galaxies and intergalactic material independently of each other, while
(in the author's view) by far the best information will come from simultaneous
surveys of galaxies and the intergalactic material (IGM) in their vicinity.
Only this will show directly how galaxies affect their surroundings and provide
a rough energy scale for supernova-driven winds. Redshifts 1<z<3 are ideal for
the joint galaxy/IGM surveys we advocate, because the comoving density of star
formation is near its peak, because the Lyman-alpha forest is thin enough for
QSO spectra to reveal the locations of the dominant metallic species, and
because bright background QSOs are common. But a new UV-capable spectrograph in
space will be required.


title: The SCUBA Local Universe Galaxy Survey

abstract:
  The SCUBA local universe galaxy survey is the first systematic survey of the
local universe at submillimetre wavelengths. We have observed ~200 galaxies
from the IRAS bright galaxy catalogue and the CfA optical redshift survey. The
IRAS sample showed that our estimate of the luminosity function was potentially
biased if a cold population of galaxies existed which would not have appeared
in the IRAS BGS but would have been detected in a SCUBA blind survey. Here we
present preliminary results from the optically selected sample which suggest
that this is indeed the case.


title: Scaling Relations of Field Spirals at intermediate Redshift

abstract:
  In the last few years, galaxies at redshifts up to z~1 have become accessible
for medium-resolved spectroscopy thanks to the new generation of 10m-class
telescopes. With kinematic and photometric information on spiral galaxies in
this regime, well-known scaling relations like the Tully-Fisher relation (TFR)
can be studied over half a Hubble time. By comparison to local samples, these
studies facilitate simultaneous tests of the hierarchical merging scenario and
stellar population models. Using the Very Large Telescope, we obtained
spatially resolved rotation curves of 78 spiral galaxies in the FORS Deep Field
(FDF), covering all Hubble types from Sa to Sm/Irr at redshifts 0.1<z<1.0. We
find evidence for a B-band luminosity increase of up to 2mag for low-mass
spirals, whereas the most massive galaxies are of the same luminosity as their
local counterparts. In effect, the TFR slope decreases significantly. This
would explain the discrepant results of previous observational studies. We also
present the velocity-size relation and compare it to the predictions of
numerical simulations based on the hierarchical merging scenario.


title: Identifying Lenses with Small-Scale Structure. I. Cusp Lenses

abstract:
  The inability of standard models to explain the flux ratios in many 4-image
gravitational lenses has been cited as evidence for significant small-scale
structure in lens galaxies. That claim has generally relied on detailed lens
modeling, so it is both model dependent and somewhat difficult to interpret. We
present a more robust and generic method for identifying lenses with
small-scale structure. For a close triplet of images associated with a source
near a cusp caustic, the sum of the signed magnifications should approximately
vanish. We derive realistic upper bounds on the sum, and argue that lenses with
flux ratios that significiantly violate the bounds can be said to have
structure in the lens potential on scales smaller than the image separation.
Five observed lenses have such flux ratio ``anomalies'': B2045+265, 1RXS
J1131-1231, and SDSS J0924+0219 have strong anomalies; B0712+472 has a strong
anomaly at optical/near-IR wavelengths and a marginal anomaly at radio
wavelengths; and RX J0911+0551 appears to have an anomaly, but this conclusion
is subject to uncertainties about octopole modes in early-type galaxies.
Analysis of the cusp relation does not identify the known anomaly in B1422+231,
so methods that are more sophisticated (and less generic) than the cusp
relation may be necessary to uncover flux ratio anomalies in some systems.
Although these flux ratio anomalies might represent milli- or micro-lensing, we
cannot identify the cause; we can only conclude that the lenses have
significant structure in the potential on scales smaller than the separation
between the images. Additional arguments must be invoked to specify the nature
of this small-scale structure. [Abridged]


title: The True Incidence of Magnetism among Field White Dwarfs

abstract:
  We study the incidence of magnetism in white dwarfs from three large and
well-observed samples of hot, cool, and nearby white dwarfs in order to test
whether the fraction of magnetic degenerates is biased, and whether it varies
with effective temperature, cooling age, or distance. The magnetic fraction is
considerably higher for the cool sample of Bergeron, Ruiz, and Leggett, and the
Holberg, Oswalt, and Sion sample of local white dwarfs that it is for the
generally-hotter white dwarfs of the Palomar Green Survey. We show that the
mean mass of magnetic white dwarfs in this survey is 0.93 solar masses or more,
so there may be a strong bias against their selection in the magnitude-limited
Palomar Green Survey. We argue that this bias is not as important in the
samples of cool and nearby white dwarfs. However, this bias may not account for
all of the difference in the magnetic fractions of these samples.
  It is not clear that the magnetic white dwarfs in the cool and local samples
are drawn from the same population as the hotter PG stars. In particular, two
or threee of the cool sample are low-mass white dwarfs in unresolved binary
systems. Moreover, there is a suggestion from the local sample that the
fractional incidence may increase with decreasing temperature, luminosity,
and/or cooling age. Overall, the true incidence of magnetism at the level of 2
megagauss or greater is at least 10%, and could be higher. Limited studies
capable of detecting lower field strengths down to 10 kilogauss suggest by
implication that the total fraction may be substantially higher than 10%.


title:
Nonthermal Emissions from Particles Accelerated by Turbulence in
  Clusters of Galaxies

abstract:
  We consider nonthermal emission from clusters of galaxies produced by
particle acceleration by resonant scattering of Alfv\'{e}n waves driven by
fluid turbulence through the Lighthill mechanism in the intracluster medium. We
assume that the turbulence is driven by cluster mergers. We find that the
resonant Alfv\'{e}n waves can accelerate electrons up to
  \gamma ~10^5 through resonant scattering. We also find that the turbulent
resonant acceleration can give enough energy to electrons to produce the
observed diffuse radio relic emission from clusters if the clusters have a pool
of electrons with \gamma ~10^3.
  This mechanism can also explain the observed hard X-ray emission from
clusters if the magnetic field in a cluster is small enough (~<
  \mu G) or the fluid turbulence spectrum is flatter than the Kolmogorov law.
The fluid turbulence could be observed with Astro-E2 in the regions where
diffuse radio emission is observed. Although non-gravitational heating before
cluster formation (preheating) steepens a relation between radio luminosity and
X-ray temperature, our predicted relation is still flatter than the observed
one.


title: What If w < -1 ?

abstract:
  The cosmological "equation of state parameter", w, is equal to -1 for a true
cosmological constant, and is greater than -1 for quintessence. There is a
widespread reluctance to consider the remaining possibility, w < -1, though in
fact there is a variety of theoretical and observational evidence in favour of
this range. We briefly discuss some of the objections to w < -1 and show that
each of them can readily be circumvented. We also briefly consider what string
theory has to say about this.


title: Correlation-consistency cartography of the double inflation landscape

abstract:
  We show explicitly some exciting features of double-inflation: (i) it can
often lead to strongly correlated adiabatic and entropy (isocurvature) power
spectra. (ii) The two-field slow-roll consistency relations can be violated
when the correlation is large at Hubble crossing. (iii) The spectra of
adiabatic and entropy perturbations can be strongly scale-dependent and tilted
toward either the red or blue. These effects are typically due to a light or
time-dependent entropy mass and a non-negligible angular velocity in field
space during inflation. They are illustrated via a multi-parameter numerical
search for correlations in two concrete models. The correlation is found to be
particularly strong in a supersymmetric scenario due to rapid growth of entropy
perturbations in the tachyonic region separating the two inflationary stages.
Our analysis suggests that realistic double-inflation models will provide a
rich and fruitful arena for the application of future cosmic data sets and new
approximation schemes which go beyond slow-roll.


title: Effects of Preheated Clusters on the CMB Spectrum

abstract:
  Mounting evidence from $x$-ray observations reveals that bound objects should
receive some form of energy in the past injected from non-gravitaional sources.
We report that an instantaneous heating scheme, for which gases in dense
regions were subjected to a temperature jump of 1keV at $z=2$ whereas those in
rarified regions remained intact, can produce bound objects obeying the
observed mass-temperature and luminosity-temperature relations. Such preheating
lowers the peak Sunyaev-Zeldovich (SZ) power by a factor of 2 and exacerbates
the need for the normalization of matter fluctuations $\sigma_8$ to assume an
extreme high value $(\sim 1.1)$ for the SZ signals to account for the excess
anisotropy on 5-arcminute scale detected by the Cosmic Background Imager in the
cosmic microwave background radiation.


title: Spectroscopy of Main Sequence Stars in Globular Clusters

abstract:
  Although globular clusters are generally chemically homogeneous, substantial
abundance variations are sometimes seen even among unevolved main sequence
stars, especially for the CNO group of elements. Multi-object
intermediate-dispersion spectroscopic systems are now being used to determine
the patterns of abundance variations for large samples of stars, while high
dispersion spectrographs on 8m-class telescopes are providing good spectra of
individual faint stars. In some circumstances the spectra of many similar stars
can be combined to yield extremely high S/N spectra. The sample of clusters
which has been studied remains small, but it seems that many of the more
metal-rich clusters must have experienced some sort of self-enrichment, either
in a proto-cluster stage, or through successive episodes of star formation or
some other processes early in their lives. The metal-poor clusters provide
equally clear evidence for internal mixing and dredge-up of processed material
within evolving red giant stars.


title: Hidden Subluminous sd/wd among the FAUST UV sources toward OPHIUCHUS

abstract:
  A UV image in the direction of Ophiuchus, obtained with the FAUST instrument
is analysed. Suitable candidates as unrecognized subluminous stars are selected
comparing the observed UV flux to the predicted one. The uv-excess objects were
observed at the 1.0 m Wise telescope. This method yields to the detection of
eight broad Balmer lines objects. Six are classified as sds and two wds,
comparing the Hbeta line profile with that of stellar model atmospheres.


title: On the central black hole mass in Mkn~501

abstract:
  We analyse the apparent disagreement between the mass estimates of the
central black hole(s) in Mkn~501 based on (i) the observations of the host
galaxy, (ii) the high energy (HE) emission mechanism, and (iii) the modulation
of the beamed radiation by a black hole (BH) binary system. While method (i)
seems to imply a central mass > 5\times 10^8 M_{sun}, method (ii) suggests a BH
mass less than 6 \times 10^7 M_{sun}. We critically discuss the estimates
inferred from (i) showing that current uncertainties may permit a central mass
as low as ~(2-3)\times 10^8 M_{sun}. We demonstrate that in this case the
estimates (i) and (ii) might be brought into agreement by assuming a binary BH
system where the jet dominating the HE emission originates from the less
massive (secondary) BH as suggested by method (iii). On the other hand, if
Mkn~501 has in fact a high central BH mass of order 10^9 M_{sun}, a change of
fundamental assumptions seems to be required in the context of several HE
emission models. We show, that in this case a binary scenario following (iii)
may be still possible if the jet which dominates the emission emerges from the
more massive (primary) BH and if the binary evolution passes through phases of
super-Eddington accretion and/or decreased conversion efficiency.


title: Optical and Infrared Photometry of the Nearby Type Ia Supernova 2001el

abstract:
  We present well sampled optical (UBVRI) and infrared (JHK) light curves of
the nearby (~18.0 Mpc) Type Ia supernova SN 2001el, from 11 days before to 142
days after the time of B-band maximum. The data represent one of the best sets
of optical and infrared photometry ever obtained for a Type Ia supernova. Based
on synthetic photometry using optical spectra of SN 2001el and optical and
infrared spectra of SN 1999ee, we were able to devise filter corrections for
the BVJHK photometry of SN 2001el which to some extent resolve systematic
differences between SN 2001el datasets obtained with different
telescope/filter/instrument combinations. We also calculated V minus infrared
color curves on the basis of a delayed detonation model and showed that the
theoretical color curves match the unreddened loci for Type Ia SNe with
mid-range decline rates to within 0.2 mag. Given the completeness of the light
curves and the elimination of filter-oriented systematic errors to some degree,
the data presented here will be useful for the construction of photometric
templates, especially in the infrared. On the whole the photometric behavior of
SN 2001el was quite normal. The second H-band maximum being brighter than the
first H-band maximum is in accord with the prediction of Krisciunas et al.
(2000) for Type Ia SNe with mid-range decline rates. The photometry exhibits
non-zero host extinction, with total A_V = 0.57 +/- 0.05 mag along the line of
sight. NGC 1448, the host of SN 2001el, would be an excellent target for a
distance determination using Cepheids.


title: The X-ray afterglow of GRB 020322

abstract:
  The spectrum of the afterglow of GRB 020322 is the highest-quality X-ray
spectrum of a GRB afterglow available to date. It was detected by XMM-Newton in
an observation starting fifteen hours after the GRB with a mean 0.2--10.0 keV
observed flux of 3.5+/-0.2x10^-13 erg cm^-2 s^-1, making it the brightest X-ray
afterglow observed so far with XMM-Newton. The source faded; its lightcurve was
well fit by a power-law with a decay index of 1.26+/-0.23. The spectrum is
adequately fit with a power-law absorbed with neutral or ionised gas
significantly in excess of the foreground Galactic column, at redshift
1.8_{-1.1}^{+1.0} or with low metal abundances. No spectral line or edge
features are detected at high significance, in particular, a thermal emission
model fits the data poorly, the upper limit on its contribution to the spectrum
is 3.7x10^-14 erg cm^-2 s^-1, or at most ~10% of the total flux. No spectral
variability is observed.


title: Large-Scale Structure in the NIR-Selected MUNICS Survey

abstract:
  The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep,
photometric survey selected in the K' band. The project's main scientific aims
are the identification of galaxy clusters up to redshifts of unity and the
selection of a large sample of field early-type galaxies up to z < 1.5 for
evolutionary studies. We created a Large Scale Structure catalog, using a new
structure finding technique specialized for photometric datasets, that we
developed on the basis of a friends-of-friends algorithm. We tested the
plausibility of the resulting galaxy group and cluster catalog with the help of
Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach.


title: Chemistry and Dynamics in Pre-Protostellar Cores

abstract:
  We have compared molecular line emission to dust continuum emission and
modeled molecular lines using Monte Carlo simulations in order to study the
depletion of molecules and the ionization fraction in three preprotostellar
cores, L1512, L1544, and L1689B. L1512 is much less dense than L1544 and
L1689B, which have similar density structures. L1689B has a different
environment from those of L1512 and L1544. We used density and temperature
profiles, calculated by modeling dust continuum emission in the submillimeter,
for modeling molecular line profiles. In addition, we have used molecular line
profiles and maps observed in several different molecules toward the three
cores. We find a considerable diversity in chemical state among the three
cores. The molecules include those sensitive to different timescales of
chemical evolution such as CCS, the isotopes of CO and HCO+, DCO+, and N2H+.
The CO molecule is significantly depleted in L1512 and L1544, but not in
L1689B. CCS may be in the second enhancement of its abundance in L1512 and
L1544 because of the significant depletion of CO molecules. N2H+ might already
start to be depleted in L1512, but it traces very well the distribution of dust
emission in L1544. On the other hand, L1689B may be so young that N2H+ has not
reached its maximum yet. The ionization fraction has been calculated using
H13CO+ and DCO+. This study suggests that chemical evolution depends on the
absolute timescale during which a core stays in a given environment as well as
its density structure.


title: The Imprint of the Cosmic Dark Ages on the Near Infrared Background

abstract:
  The redshifted light of the first (Pop III) stars might substantially
contribute to the near infrared background (NIRB). By fitting recent data with
models including up-to-date Pop III stellar spectra, we find that such stars
can indeed account for the whole NIRB residual (i.e. after `normal' galaxy
contribution subtraction) if the high redshift star formation efficiency is f =
10%-50%, depending on the IMF (the top-heaviest requiring lowest efficiency)
and on the unknown galaxy contribution in the L band (our models, however,
suggest it to be negligible). Such epoch of Pop III star formation ends in all
models by z_end ~ 8.8, with a hard limit z_end < 9 set by J band observations.
To prevent an associated IGM over-enrichment with heavy elements compared to
observed levels in the IGM, pair-instability supernovae must be the dominant
heavy element sources. Alternative explanations must break the light-metal
production link by advocating very massive stars (M > 260 M_sun) locking their
nucleosynthetic products in the compact remnant or by postulating an extremely
inhomogeneous metal enrichment of the Ly alpha forest. We discuss these
possibilities in detail along with the uncertainties related to the adopted
zodiacal light model.


title: On the Nature of Hidden Broad Line Regions in Seyfert 2 Galaxies

abstract:
  We consider the sample of Tran (2001) to study the X-ray properties of
Seyfert 2 galaxies with and without polarized broad lines.


title: The afterglow of GRB 021004: surfing on density waves

abstract:
  We present a model for the early optical afterglow of GRB 021004. This burst
had one of the earliest detected optical afterglows, allowing a dense optical
sampling. The lightcurve was peculiar, since bright bumps were superimposed to
the regular power-law decay observed in many other events. We show that, given
their time scale and shape, the bumps are due to the interaction of the
fireball with moderate enhancements in the ambient medium density. The
enhancements have a density contrast of order 10, modifying only slightly the
dynamics of the fireball, which therefore surfs on them rather than colliding
onto them. A relativistic reverse shock does not develop. Since the interaction
takes place when the fireball is still hyper-relativistic it is not possible to
understand if the overdensities are localized in clumps or are spherically
symmetric around the GRB progenitor. The monotonic decrease of the contrast of
successive rebrightenings suggests however the presence of clumps in an average
uniform environment. Such an interpretation, complemented by the detection of
several high velocity absorption systems in the optical spectrum, strongly
suggests that GRB 021004 exploded within the remnant of a previous explosion.


title:
Measurement of the antiproton to proton ratio in cosmic rays using the
  Moon shadow with the L3+C detector

abstract:
  The observation of the Moon shadow effect with the L3+C detector is reported.
The expected offset and elongation of the Moon shadow due to the geomagnetic
field are clearly observed. A determination of the angular resolution and
pointing error has beem performed through this observation. A preliminary upper
limit of the antiproton to proton ratio in cosmic rays is given in the TeV
region.


title: The radial velocities and physical parameters of HD 553

abstract:
  HD 553 was discovered as an eclipsing binary by Hipparcos. Here, we present
the first radial velocity curve for this system. It is found that HD 553 is a
double-lined spectroscopic binary. Despite the large luminosity difference, the
two components of the system are of very simmilar mass. The primary, a
K0-giant, fills a large fraction of its Roche-lobe. The secondary is, despite
its very similar mass, still a late-type dwarf. The radial velocity curve
allows to constrain several stellar and system parameters.


title: Parsec Scale Properties of Radio Sources

abstract:
  We present a new complete sample of radio sources selected from the B2 and
3CR catalogues, with no bias respect to the jet velocity and orientation. Using
preliminary data we investigate the parsec scale properties of radio sources
with different radio power and kpc scale morphology. We stress the evidence for
high velocity pc scale jets in all sources and conclude that the properties of
parsec scale jets are similar regardless of the source total power and large
scale morphology. Moreover we show two epoch images of two nearby radio
galaxies: a low power compact source and a CSO. The comparison of the two epoch
images suggests that in both sources the size is increasing with time. We
derive a possible advance speed and estimate their dynamic age.


title: The Cool ISM in S0 Galaxies. I. A Survey of Molecular Gas

abstract:
  Lenticular galaxies remain remarkably mysterious as a class. Observations to
date have not led to any broad consensus about their origins, properties and
evolution, though they are often thought to have formed in one big burst of
star formation early in the history of the Universe, and to have evolved
relatively passively since then. In that picture, current theory predicts that
stellar evolution returns substantial quantities of gas to the interstellar
medium; most is ejected from the galaxy, but significant amounts of cool gas
might be retained. Past searches for that material, though, have provided
unclear results. We present results from a survey of molecular gas in a
volume-limited sample of field S0 galaxies, selected from the Nearby Galaxies
Catalog. CO emission is detected from 78 percent of the sample galaxies. We
find that the molecular gas is almost always located inside the central few
kiloparses of a lenticular galaxy, meaning that in general it is more centrally
concentrated than in spirals. We combine our data with HI observations from the
literature to determine the total masses of cool and cold gas. Curiously, we
find that, across a wide range of luminosity, the most gas rich galaxies have
about 10 percent of the total amount of gas ever returned by their stars. That
result is difficult to understand within the context of either monolithic or
hierarchical models of evolution of the interstellar medium.


title: Coupling nuclear reaction rates with temperature in explosive conditions

abstract:
  We present a straightforward integration method to compute the abundance and
temperature evolution in explosive scenarios. In this approach the thermal
equation is implicitely coupled with chemical equations in order to avoid
instabilities and ensure a gentle transition from the normal combustion regime
to the quasi (QSE) and complete nuclear statistical equilibrium (NSE). Two
nuclear networks, with 14 nuclei (alpha-network) and 86 nuclei (including
protons and neutrons) respectively, have been considered. The scheme is
suitable to cope with a variety of explosive burning regimes.


title:
Nucleosynthesis as a result of multiple delayed detonations in Type Ia
  Supernovae

abstract:
  The explosion of a white dwarf of mass 1.36 M$_\odot$ has been simulated in
three dimensions with the aid of a SPH code. The explosion follows the delayed
detonation paradigma. In this case the deflagration-detonation transition is
induced by the large corrugation of the flame front resulting from
Rayleigh-Taylor instability and turbulence. The nucleosynthetic yields have
been calculated, showing that some neutronized isotopes such as 54^Fe or 58^Ni
are not overproduced with respect to the solar system ratios. The distribution
of intermediate-mass elements is also compatible with the spectra of normal
SNIa. The excepcion is, however, the abundance of carbon and oxygen, which are
overproduced.


title:
A New Algorithm for Radiative Feedback and its Application to the
  Formation of Massive Stars

abstract:
  We have developed a simplified method of treating the radiative acceleration
of dusty flows. This method retains the sharp impulse at the dust destruction
radius that is a feature of frequency dependent radiative transfer, whilst
placing minimal demands on computing resources. As such, it is suitable for
inclusion in hydrodynamic codes. We have applied this method to the formation
of massive stars in spherical geometry, and find that the fraction of a cloud
which can accrete on to the central star is a strong function of the Jeans'
Number and density profile of the cloud. Massive star formation is favoured by
cold homogeneous conditions, as might result in regions where gas is swept up
by some external triggering agent. We find (in contrast to previous authors)
that massive star formation does not require a depleted dust mixture, although
the use of dust at typical interstellar abundances does reduce the final
stellar mass compared to cores formed from a depleted mixture.


title: Observations of r- and s-process elements in Population II stars

abstract:
  The framework for the interpretation of neutron-capture elements observed in
Population II stars, established 20-25 years ago, is that these stars primarily
exhibit r-process signatures, due to the inefficiency of the s-process at low
metallicity. A view developed later that the r-process might be universal,
which is to say that the same r-process element ratios would exist at high and
low metallicity. However, observations of s-process abundances in
low-metallicity environments, and departures from a universal r-process ratio
for the lightest neutron-capture elements have required revisions to the
framework. Observations indicating the need for and nature of these changes
will be presented.


title: H2O Masers and Supersonic Turbulence

abstract:
  We use unpublished and published VLBI results to investigate the geometry and
the statistical properties of the velocity field traced by H2O masers in five
galactic regions of star formation -- Sgr B2(M), W49N, W51(MAIN), W51N, and
W3(OH). In all sources the angular distribution of the H2O hot spots
demonstrates approximate self-similarity (fractality) over almost four orders
of magnitude in scale, with the calculated fractal dimension d between
(approximately) 0.2 and 1.0. In all sources, the lower order structure
functions for the line-of-sight component of the velocity field are
satisfactorily approximated by power laws, with the exponents near their
classic Kolmogorov values for the high-Reynolds-number incompressible
turbulence. These two facts, as well as the observed significant excess of
large deviations of the two-point velocity increments from their mean values,
strongly suggest that the H2O masers in regions of star formation trace
turbulence. We propose a new conceptual model of these masers in which maser
hot spots originate at the sites of ultimate dissipation of highly supersonic
turbulence produced in the ambient gas by the intensive gas outflow from a
newly-born star. Due to the high brightness and small angular sizes of masing
hot spots and the possibility of measuring their positions and velocities with
high precision, they become a unique probe of supersonic turbulence.


title: Cerium: the lithium substitute in post-AGB stars

abstract:
  In this letter we present an alternative identification for the line detected
in the spectra of s-process enriched low-mass post-AGB stars around 6708A and
which was interpreted in the literature as due to Li. Newly released line lists
of lanthanide species reveal, however, the likely identification of the line to
be due to a CeII transition. We argue that this identification is consistent
with the Ce abundance of all the objects discussed in the literature and
conclude that in none of the low-mass s-process enriched post-AGB stars there
is indication for Li-production.


title:
A multiwavelength approach to the SFR estimation in galaxies at
  intermediate redshifts

abstract:
  We use a sample of 7 starburst galaxies at intermediate redshifts (z ~ 0.4
and z ~ 0.8) with observations ranging from the observed ultraviolet to 1.4
GHz, to compare the star formation rate (SFR) estimators which are used in the
different wavelength regimes. We find that extinction corrected Halpha
underestimates the SFR, and the degree of this underestimation increases with
the infrared luminosity of the galaxies. Galaxies with very different levels of
dust extinction as measured with SFR(IR)/SFR(Halpha, uncorrected for
extinction) present a similar attenuation A[Halpha], as if the Balmer lines
probed a different region of the galaxy than the one responsible for the bulk
of the IR luminosity for large SFRs. In addition, SFR estimates derived from
[OII]3727 match very well those inferred from Halpha after applying the
metallicity correction derived from local galaxies. SFRs estimated from the UV
luminosities show a dichotomic behavior, similar to that previously reported by
other authors in galaxies at z <~ 0.4. Here we extend this result up to z ~
0.8. Finally, one of the studied objects is a luminous compact galaxy (LCG)
that may be suffering similar dust-enshrouded star formation episodes. These
results highlight the relevance of quantifying the actual L(IR) of LCGs, as
well as that of a much larger and generic sample of luminous infrared galaxies,
which will be possible after the launch of SIRTF.


title: Monte Carlo reconstruction of the inflationary potential

abstract:
  We present Monte Carlo reconstruction, a new method for ``inverting''
observational data to constrain the form of the scalar field potential
responsible for inflation. This stochastic technique is based on the flow
equation formalism and has distinct advantages over reconstruction methods
based on a Taylor expansion of the potential. The primary ansatz required for
Monte Carlo reconstruction is simply that inflation is driven by a single
scalar field. We also require a very mild slow roll constraint, which can be
made arbitrarily weak since Monte Carlo reconstruction is implemented at
arbitrary order in the slow roll expansion. While our method cannot evade
fundamental limits on the accuracy of reconstruction, it can be simply and
consistently applied to poor data sets, and it takes advantage of the attractor
properties of single-field inflation models to constrain the potential outside
the small region directly probed by observations. We show examples of Monte
Carlo reconstruction for data sets similar to that expected from the Planck
satellite, and for a hypothetical measurement with a factor of five better
parameter discrimination than Planck.


title: Evidence for a warm ISM in the Fornax dEs FCC046 and FCC207

abstract:
  We present Halpha+[NII] narrow-band imaging of FCC046 and FCC207, two dES in
the Fornax Cluster. B-R and B-I color-maps clearly show signs of
dust-absorption in FCC207. FCC046 has a very bright blue nucleus, offset by
about 1.1'' with respect to the outer isophotes. Moreover, FCC046 shows a
pronounced lopsided shape. The emitting regions differ considerably between the
two galaxies. Whereas FCC207 has only one central emission region, FCC046 also
contains fainter emission regions. Based on broad-band colours, its disturbed
shape and its very bright nucleus, FCC046 is akin to the class of amorphous
dwarfs. The central emission regions of both galaxies are resolved and we
estimate their diameters at about 60 pc. Their Halpha luminosities can be
explained as photo-ionisation by post-AGB stars in an old population. Some of
the emission regions in FCC046 are resolved and have diameters of the order of
50-150 pc and H$\alpha$ luminosities of the order of 10^30 W, comparable to
supernova remnants or nebulae around Wolf-Rayet stars. Hence, FCC046 is clearly
undergoing star-formation while for FCC207 the case is not as clearcut. We
estimate the mass of the HII gas in FCC046 at M(HII) = 40-150 Mo. The
ionised-gas content of FCC207 is somewhat higher : M(HII) = 60-190 Mo.


title:
A Search for Core-Collapse Supernova Progenitors In Hubble Space
  Telescope Images

abstract:
  Identifying the massive progenitor stars that give rise to core-collapse
supernovae (SNe) is one of the main pursuits of supernova and stellar evolution
studies. Using ground-based images of recent, nearby SNe obtained primarily
with KAIT, astrometry from 2MASS, and archival images from HST, we have
attempted the direct identification of the progenitors of 16 SNe II and SNe
Ib/c. We may have identified the progenitors of the SNe II 1999br, 1999ev, and
2001du as supergiant stars with M^0_V ~ -6 mag in all three cases. We may have
also identified the progenitors of the SNe Ib 2001B and 2001is as very luminous
supergiants with M^0_V ~ -8 to -9 mag, and possibly the progenitor of the SN Ic
1999bu as a supergiant with M^0_V ~ -7.5 mag. Additionally, we have recovered
at late times SNe 1999dn, 2000C, and 2000ew, although none of these had
detectable progenitors on pre-SN images. In fact, for the remaining SNe only
limits can be placed on the absolute magnitude and color (when available) of
the progenitor. The detected SN II progenitors and limits are consistent with
red supergiants as progenitor stars, although possibly not as red as we had
expected. Our results for the SNe Ib/c do not strongly constrain either
Wolf-Rayet stars or massive interacting binary systems as progenitors.


title:
A Flaring L5 Dwarf: The Nature of H\alpha Emission in Very Low Mass
  (Sub)Stellar Objects

abstract:
  Time series spectrophotometry of the L5 dwarf 2MASS 01443536-0716142 showed
strong H\alpha emission which declined by nearly 75% in four consecutive
exposures. The line was not detected in emission on a spectrum obtained eleven
months later. This behavior constrasts with that of 2MASSI J1315309-264951, an
L5 dwarf which has shown even stronger H\alpha emission on four separate
occasions. The observational database suggests that L dwarfs can be found in
such strong flares only occasionally, with a duty cycle of order 1%. In
contrast, the few, continuously-strong H\alpha emitters, including PC 0025+0447
and 2MASSI J1237392+652615, must either be (1) objects no older than 10-100
Myrs with continuously-active accretion and/or chromospheres, but which
apparently formed in isolation from known young stellar clusters and
associations, or (2) objects empowered by a different and unknown mechanism for
the H\alpha energy.


title: HI Imaging of LGS 3 and an Apparently Interacting High-Velocity Cloud

abstract:
  We present a 93' by 93' map of the area near the Local Group dwarf galaxy LGS
3, centered on an HI cloud 30' away from the galaxy. Previous authors
associated this cloud with LGS 3 but relied on observations made with a 36'
beam. Our high-resolution (3.4'), wide-field Arecibo observations of the region
reveal that the HI cloud is distinct from the galaxy and suggest an interaction
between the two. We point out faint emission features in the map that may be
gas that has been tidally removed from the HI cloud by LGS 3. We also derive
the rotation curve of the cloud and find that it is in solid-body rotation out
to a radius of 10', beyond which the rotation velocity begins to decline.
Assuming a spherical geometry for the cloud, the implied mass is 2.8 x 10^7
(d/Mpc) M_{Sun}, where d is the distance in Mpc. The observed HI mass is 5.5 x
10^6 (d/Mpc)^2 M_{Sun}, implying that the cloud is dark-matter dominated unless
its distance is at least 1.9 Mpc. We propose that the cloud is a high-velocity
cloud that is undergoing a tidal interaction with LGS 3 and therefore is
located roughly 700 kpc away from the Milky Way. The cloud then contains a
total mass of ~2.0 x 10^7 M_{Sun}, 82% of which consists of dark matter.


title: The Infrared Counterpart of the Microquasar GRS 1758-258

abstract:
  We present revised infrared (2.2 micron) astrometry of the field containing
the Galactic microquasar GRS 1758-258, using observations at the Keck I 10-m
telescope. We find three candidates for the microquasar within a 3 sigma error
circle, but none within 2 sigma. We show that if the 18.4 day X-ray period of
GRS 1758-258 is due to a binary orbit, then only one of the three candidates,
an early K-type giant, is large enough to power the microquasar via Roche lobe
overflow. We therefore identify this star as the infrared counterpart of GRS
1758-258, which we classify as a low mass X-ray binary. Long term infrared
monitoring of this source should provide further information about the
microquasar system, including a confirmation of the X-ray period and an
estimate of the compact object's mass.


title:
2MASS 1315-2649: A High Proper Motion L Dwarf with Strong H-alpha
  Emission

abstract:
  In Hall (2002) I reported that 2MASSI J1315309-264951 is an L dwarf with
strong H-alpha emission. Two spectroscopic epochs appeared to show that the
H-alpha was variable, decreasing from 121 Angstroms to 25 Angstroms EW, which I
interpreted as a flare during the first observation. Gizis (2002) independently
discovered this object, and his intermediate spectroscopic epoch shows H-alpha
with 97 Angstroms EW. A new fourth epoch of spectroscopy again shows a very
large H-alpha EW (124 Angstroms), confirming this object to be a persistent,
strong H-alpha emitter. Whether the H-alpha is steady (like 2MASS 1237+6526) or
from continuous strong flaring (like PC0025+0447) remains unclear. Imaging
confirms that 2MASS 1315-2649 has a high proper motion (0.71"/year),
corresponding to a transverse velocity of ~76 km/s at its distance of ~23 pc.
Thus 2MASS 1315-2649 is consistent with being >~2 Gyr old and therefore
relatively massive. If that is so, the correlation of H-alph activity with mass
found by Gizis et al. (2000) would seem to support the continuous strong
flaring scenario, though it does not rule out a brown dwarf binary accretion
scenario.


title:
On the Incidence of Strong Gravitational Lensing by Clusters in the Las
  Campanas Distant Cluster Survey

abstract:
  The observed incidence of strongly lensing clusters exceeds the predictions
of a Lambda-CDM model by about a factor of 10. We revisit the observational
side of this discrepancy by measuring the incidence of strong lensing in a
subsample of clusters drawn from the Las Campanas Distant Cluster Survey
(LCDCS). Among clusters with 0.5<= z <= 0.7, the redshift range in which we
focus our search, we find two strongly lensed systems within an effective
search area of 69 sq. deg. There is at least one other strongly lensed system
in the LCDCS outside of this redshift range, where we are less complete. Over
all redshifts, the Lambda-CDM model produces one large arc every 146 sq.
degrees. Assuming Poisson statistics, the probability of finding 3 or more
strongly lensing clusters in 69 sq. degrees is 0.012. The lensing incidence
within the LCDCS is in agreement with that derived from an X-ray selected
sample and what has been preliminarily presented from an independent optical
cluster survey. The origin of the disagreement between theory and observations,
which remains at least at the order of magnitude scale for the Lambda-CDM
model, lies either in the concordance cosmological model, in the
characteristics of the resulting cluster potentials, or in the adopted source
population.


title: Rates of reconnection in pulsar winds

abstract:
  Using the formulation of relativistic reconnection by Lyutikov & Uzdensky
(2002) we estimate the upper possible rates of reconnection in pulsar winds
using Bohm prescription for resistivity. We find that the velocity of plasma
inflow into the reconnection layer may be relativistic, of the order of the
speed of light in the plasma rest-frame. This in principle may allow efficient
dissipation of the magnetic field energy in the wind and/or destruction of the
toroidal magnetic flux.
  The efficiency of reconnection realized in pulsar winds remains an open
question: it should depend both on the microphysical properties of plasma and
on the three-dimensional structure of the reconnection flow.


title:
The Effects of Photoionization on Galaxy Formation -- III: Environmental
  Dependence in the Luminosity Function

abstract:
  Using semi-analytic modeling techniques, we calculate the luminosity function
of galaxy populations residing in cold dark matter halos of different mass. We
pay particular attention to the influence of the reionization of the Universe
on the number of faint galaxies and to the effects of dynamical friction and
tidal limitation of satellites on the number of bright galaxies. We find
substantial differences in the shapes of the galaxy luminosity functions in
halos of different mass which reflect generic features of the cold dark matter
model of galaxy formation and thus offer the opportunity to test it. We then
consider how the individual halo luminosity functions combine together to
produce the global luminosity function. Surprisingly, the global function ends
up having a shallower faint end slope than those of the constituent halo
luminosity functions. We compare our model predictions with the limited
datasets compiled by Trentham & Hodgkin. We find good agreement with the
luminosity functions measured in the Virgo and Coma clusters but significant
disagreement with the luminosity functions measured in the Local Group and Ursa
Minor cluster. We speculate on possible inadequacies in our modeling and in the
existing observational samples. The luminosity functions of galaxies in groups
and clusters identified in the 2dF and SDSS galaxy redshift surveys offer the
prospect of testing galaxy formation models in detail.


title:
Radio Spectral Index Variations and Physical conditions in Kepler's
  Supernova Remnant

abstract:
  A new epoch of VLA measurements of Kepler's supernova remnant was obtained to
make accurate measurements of the radio spectral index variations and
polarization. We have compared these new radio images with Halpha, infrared,
and X-ray data to better understand the three dimensional structure and
dynamics of Kepler, and to better understand the physical relationships between
the various nonthermal and thermal plasmas. Spatial variations in the radio
spectral index from -0.85 to -0.6 are observed between 6 cm and 20 cm. There is
a strong correspondence between the radial and azimuthal profiles of the radio,
X-ray, Halpha, and infrared emission in different locations around the remnant
although there is no single, global pattern. Spectral tomography shows that the
flat- and steep-spectrum radio emissions have distinct structures. The
flat-spectrum radio emission is found either at a larger radius than or
coincident with the steep-spectrum emission. We interpret these spectral
components as tracing forward- and reverse-shocked material, respectively. The
Halpha and IR images are very similar. Their leading edges are coincident and
are either in front of or coincident with the leading edges of the X-ray and
radio emission. The X-ray emission matches the Halpha and IR emission in
places, and in other places traces the steep-spectrum radio emission. In the
north there is also an anticorrelation in the azimuthal profiles around the
remnant of the flat-spectrum radio emission and the thermal X-ray, Halpha, and
IR emissions. We suggest that this could be due to a relative weakening of the
particle acceleration at the forward shock due to Alfven wave damping in
regions of high density.


title:
Observations of [S IV] 10.5 micron and [Ne II] 12.8 micron in Two Halo
  Planetary Nebulae: Implications for Chemical Self-Enrichment

abstract:
  We have detected the [S IV] 10.5 micron and [Ne II] 12.8 micron
fine-structure lines in the halo population planetary nebula (PN) DdDm 1, and
set upper limits on their intensities in the halo PN H 4-1. We also present new
measurements of optical lines from various ions of S, Ne, O, and H for DdDm 1,
based on a high-dispersion spectrum covering the spectral range 3800 A to 1
micron. These nebulae have similar O/H abundances, (O/H) = 1e-4, but S/H and
Ne/H are about half an order of magnitude lower in H 4-1 than in DdDm 1; thus H
4-1 appears to belong to a more metal-poor population. This supports previous
suggestions that PNe arising from metal-poor progenitor stars can have elevated
oxygen abundances due to internal nucleosynthesis and convective dredge-up. It
is generally accepted that high abundances of carbon in many PNe results from
self-enrichment. To the extent that oxygen can also be affected, the use of
nebular O/H values to infer the overall metallicity of a parent stellar
population (for example, in external galaxies) may be suspect, particularly for
low metallicities.


title: Timing analysis of the Seyfert-1 galaxy MCG-6-30-15 with XMM-Newton data

abstract:
  We present the main results of a deep timing analysis (in the 0.2-10 keV
energy band) of the bright Seyfert-1 galaxy MCG-6-30-15 performed on XMM-Newton
data. The light-curves and hardness ratios show that the source has large flux
and spectral variations on time-scales of a few kiloseconds at most. From the
analysis of both the power spectra and the structure function of the light
curves we detected a relevant source variability between time-scales of ~0.3
and ~10 ks. Based on this result, we extracted a characteristic size of the
X-ray emitting region of the order of 10^13 cm.