title:
Generalized Fermi-Dirac Functions and Derivatives: Properties and
  Evaluation

abstract:
  The generalized Fermi-Dirac functions and their derivatives are important in
evaluating the thermodynamic quantities of partially degenerate electrons in
hot dense stellar plasmas. New recursion relations of the generalized
Fermi-Dirac functions have been found. An effective numerical method to
evaluate the derivatives of the generalized Fermi-Dirac functions up to third
order with respect to both degeneracy and temperature is then proposed,
following Aparicio. A Fortran program based on this method, together with a
sample test case, is provided. Accuracy and domain of reliability of some
other, popularly used analytic approximations of the generalized Fermi-Dirac
functions for extreme conditions are investigated and compared with our
results.


title: Cosmic shear from STIS Pure Parallels: I Data

abstract:
  Following the second HST servicing mission in 1997 when the STIS instrument
was installed and the capability for parallel observations was enhanced, a
substantial archive of non-proprietary parallel data has been accumulating. In
this paper, we discuss the use of unfiltered STIS imaging data for a project
that requires deep observations along as many independent lines-of-sight as
possible. We have developed a technique to determine which datasets in the
archive can safely be co-added together and have developed an iterative
co-addition technique which enabled us to produce 498 high-quality, deep
images. The principal motivation for this work is to measure the Cosmic Shear
on small angular scales and a value derived from these data will be presented
in a subsequent paper. A valuable by-product of this work is a set of high
quality combined fields which can be used for other projects. The data are
publicly available at http://www.stecf.org/projects/shear/


title:
VLT Observations of the Peculiar Globular Cluster NGC6712, III: The
  Evolved Stellar Population

abstract:
  We present extensive UBVR photometry of the Galactic globular cluster (GGC)
NGC6712 obtained with the ESO Very Large Telescope (VLT) which reach down to
two magnitudes below the main sequence turn-off and allows us for the first
time to determine the age of this cluster. By using the apparent luminosity of
the zero age horizontal branch (ZAHB), $V_{ZAHB}=16.32\pm0.05$ and the stellar
main sequence (MS) turn--off (TO) magnitude $V_{TO}=19.82\pm0.10$, we obtain
$\Delta V_{TO}^{HB}=3.5\pm0.1$ (a value fully compatible with that derived for
other clusters) which suggests that, at an age of $\sim 12$ Gyr, NGC 6712 is
coeval with other GGC of similar metallicity.
  We derive interstellar reddening by comparing the position and morphology of
the red giant branch (RGB) with a wide variety of reference clusters and find
$E(B-V)=0.33\pm0.05$, a value significantly lower than had been determined
previously. Assuming this value for the reddening, we determine a true distance
modulus of $(m-M)_0 = 14.55$, corresponding to a distance of $\sim 8$ kpc.
  We find a population of 108 candidate blue straggler stars (BSS),
surprisingly large when compared with the typical BSS content of other low
concentration clusters. Moreover, we detect a very bright blue star in the core
of NGC6712 that might be a post-AGB star. These results, combined with those
already presented in two companion papers, strongly support the hypothesis that
NGC6712 was, at some early epoch of its history, much more massive and
concentrated. The continued interaction with the bulge and the disk of the
Galaxy has driven it toward dissolution, and what we now observe is nothing but
the {\it remnant} core of a cluster that once was probably one of the most
massive in the Galaxy.


title: Cluster Evolution in the ROSAT North Ecliptic Pole Survey

abstract:
  The deepest region of the ROSAT All-Sky Survey, at the North Ecliptic Pole,
has been studied to produce a complete and unbiased X-ray selected sample of
clusters of galaxies. This sample is used to investigate the nature of cluster
evolution and explore potential implications for large-scale structure models.
The survey is 99.6% optically identified. Spectroscopic redshifts have been
measured for all the extragalactic identifications. In this Letter, first
results on cluster evolution are presented based on a comparison between the
number of the observed clusters in the North Ecliptic Pole survey and the
number of expected clusters assuming no-evolution models. At z>0.3 there is a
deficit of clusters with respect to the local universe which is significant at
> 4.7sigma. The evolution appears to commence at L_{0.5-2.0} > 1.8x10^{44} erg
s^{-1} in our data. The negative evolution goes in the same direction as the
original EMSS result, the results from the 160 deg^{2} survey by Vikhlinin et
al. (1998) and the recent results from the RDCS (Rosati et al. 2000). At lower
redshifts there is no evidence for evolution, a result in agreement with these
and other cluster surveys.


title:
Dust emission from 3C radio galaxies and quasars: New ISO observations
  favour the unified scheme

abstract:
  In order to test the unified scheme for luminous radio galaxies and quasars
we observed 10 galaxy/quasar pairs from the 3CR catalogue with ISOPHOT at
infrared wavelengths between 5 and 180 micron. Each pair was selected such that
both the 178 MHz luminosity and the redshift match as close as possible between
the radio galaxy and the quasar in order to minimize effects of cosmic
evolution. 13 of the 20 sources were detected in at least one waveband. 12
sources show clear evidence of a thermal bump at FIR wavelength, while in the
remaining 7 sources the upper limits are still compatible with the presence of
luminous dust emission. In agreement with the predictions of the unified
scheme, the quasars and galaxies in our sample cannot be distinguished by their
observed mid- and far-infrared properties. This is in contrast to the IRAS
results which indicated that radio galaxies radiate significantly less mid- to
far-infrared emission than quasars. However, the IRAS samples are dominated by
low-redshift sources (z < 0.5), while our sample contains several of the most
luminous radio galaxies at redshift z ~ 1. The latter have already been
suspected to contain a hidden quasar for other reasons, e.g. an extended
emission line region aligned with the radio axis. From the ratio between FIR
luminosity emitted by dust and the radio power at 178 MHz, we conclude that the
radio galaxy/quasar unification might be perfectly valid for the most luminous
3C sources at high redshift (z > 0.8). At lower redshifts (z < 0.5), however,
some of the FRII radio galaxies contain active nuclei which emit less
UV-optical continuum than the quasars of similar radio power. (abrigded)


title: Global Probes of the Impact of Baryons on Dark Matter Halos

abstract:
  The halo mass function, dn/dM, predicted by hierarchical clustering models
can be measured indirectly using dynamical probes like the distribution of
gravitational lens image separations, dn/dDelta-theta, or halo circular
velocities, dn/d v_c. These dynamical variables depend on the halo structure as
well as the halo mass. Since baryonic physics, particularly cooling,
significantly modifies the central density structure of dark matter halos, both
observational distributions show a feature corresponding to the mass scale
below which the baryons in the halo can cool (i.e. galaxies versus clusters).
We use simplified but self-consistent models to show that the structural
changes to the halos produced by the cooling baryons explain both
distributions. Given a fixed halo mass function, matching the observed image
separation distribution or local velocity function depends largely on Omega_b
through its effects on the cooling time scales. These baryonic effects on the
halo structure also affect the evolution of the velocity function of galaxies
with redshift.


title:
Repetitive rebrightening of EG Cancri: evidence for viscosity decay in
  the quiescent disk?

abstract:
  A WZ Sge-type dwarf nova, EG Cancri, exhibited six consecutive mini-outbursts
with a mean interval of about seven days after the end of the main outburst in
1996/1997. Most unusual was that the star abruptly entered into a deep faint
minimum after such frantic activities. We propose that this peculiar phenomenon
may be understoodin terms of viscosity decay in the cold disk. In this picture,
the viscosity is produced by MHD turbulence due to the magneto-rotational
instability ('Balbus-Hawley instability') and dies down exponentially with time
when the disk becomes cold because the magnetic fields decay due to finite
conductivity in the cold disk (Gammie & Menou 1998). But the viscosity is
refreshed to a high value every time when a mini-outburst occurs (i.e., the
disk becomes hot again). It is argued that a sudden cessation of repetitive
mini-outbursts may be brought about by a very small reduction in viscosity or a
small increase in its decay rate, which may in turn be produced most likely by
stochastic fluctuations of magnetic fields. Numerical simulations based on a
simple model reproduce the observed light curve of EG Cancri very well. We
discuss possible causes why the reflares after the main outburst occur mostly
in the WZ Sge-type stars.


title: Radio Observations of New Galactic Bulge Planetary Nebulae

abstract:
  We observed 64 newly identified galactic bulge planetary nebulae in the radio
continuum at 3 and 6 cm with the Australia Telescope Compact Array. We present
their radio images, positions, flux densities, and angular sizes. The survey
appears to have detected a larger ratio of more extended planetary nebulae with
low surface brightness than in previous surveys. We calculated their distances
according to Van de Steene & Zijlstra (1995). We find that most of the new
sample is located on the near side around the galactic center and closer in
than the previously known bulge PNe. Based on H-alpha images and spectroscopic
data, we calculated the total H-alpha flux. We compare this flux value with the
radio flux density and derive the extinction. We confirm that the distribution
of the extinction values around the galactic center rises toward the center, as
expected.


title:
Observations of radio galaxy MRC 1138-262: merging galaxies embedded in
  a giant Lyman alpha halo

abstract:
  The radio galaxy MRC 1138-262 at z=2.16 is most likely a brightest cluster
galaxy in an early stage of evolution. Here we present observations of the
luminous emission line halo and the stellar components of this radio galaxy.
Optical narrow band imaging shows a very extended (about 160 kpc) and luminous
Lyman alpha halo. Infrared narrow band imaging reveals a much smaller H alpha
halo with a very different morphology. We advocate a model in which the inner
part of the halo is photoionized by direct AGN illumination or by UV photons
from young stars. Far from the nucleus (about 25 kpc), there is a region of
greatly enhanced Lyman alpha emission. At this location, it is likely that
shock ionization is important as indicated by a bend in the radio jet.
Spectroscopy of several continuum clumps in the halo shows that, although there
are striking differences between the emission and absorption features of the
spectra of various regions, they have properties similar to those of
Lyman-break galaxies. This is further evidence for a scenario in which massive
galaxies form hierarchically from smaller building blocks.


title: Layer Formation in Semiconvection

abstract:
  Layer formation in a thermally destabilized fluid with stable density
gradient has been observed in laboratory experiments and has been proposed as a
mechanism for mixing molecular weight in late stages of stellar evolution in
regions which are unstable to semiconvection. It is not yet known whether such
layers can exist in a very low viscosity fluid: this work undertakes to address
that question. Layering is simulated numerically both at high Prandtl number
(relevant to the laboratory) in order to describe the onset of layering
intability, and the astrophysically important case of low Prandtl number. It is
argued that the critical stability parameter for interfaces between layers, the
Richardson number, increases with decreasing Prandtl number. Throughout the
simulations the fluid has a tendency to form large scale flows in the first
convecting layer, but only at low Prandtl number do such structures have
dramatic consequences for layering. These flows are shown to drive large
interfacial waves whose breaking contributes to significant mixing across the
interface. An effective diffusion coefficient is determined from the simulation
and is shown to be much greater than the predictions of both an enhanced
diffusion model and one which specifically incorporates wave breaking. The
results further suggest that molecular weight gradient interfaces are
ineffective barriers to mixing even when specified as initial conditions, such
as would arise when a compositional gradient is redistributed by another
mechanism than buoyancy, such as rotation or internal waves.


title:
Implications of the BOOMERANG and MAXIMA-I results for the Baryon Mass
  Fraction in Clusters of galaxies

abstract:
  Recent BOOMERANG and MAXIMA-I analyses of the angular power spectrum of the
Cosmic Microwave Background put more stringent constraints on the cosmological
parameters. I show that these constraints are consistent with the observed
baryon budget in clusters of galaxies, allowing any further contribution to
this budget from baryons not in stars and not X-ray emitting to be less than 14
per cent at the 90 per cent level of confidence.


title: Computational Methods for Gravitational Lensing

abstract:
  Modern applications of strong gravitational lensing require the ability to
use precise and varied observational data to constrain complex lens models. I
discuss two sets of computational methods for lensing calculations. The first
is a new algorithm for solving the lens equation for general mass
distributions. This algorithm makes it possible to apply arbitrarily
complicated models to observed lenses. The second is an evaluation of
techniques for using observational data including positions, fluxes, and time
delays of point-like images, as well as maps of extended images, to constrain
models of strong lenses. The techniques presented here are implemented in a
flexible and user-friendly software package called gravlens, which is made
available to the community.


title: A Catalog of Mass Models for Gravitational Lensing

abstract:
  Many different families of mass models are used in modern applications of
strong gravitational lensing. I review a wide range of popular models, with two
points of emphasis: (1) a discussion of strategies for building models suited
to a particular lensing problem; and (2) a summary of technical results for a
canonical set of models. All of the models reviewed here are included in
publicly-available lensing software called gravlens.


title: Radio Pulses from Cosmic Ray Air Showers

abstract:
  The first experiment in which radio emission was detected from high energy
particles is described. An array of dipoles was operated by a team of British
and Irish physicists in 1964-5 at the Jodrell Bank Radio Observatory in
conjunction with a simple air shower trigger. The array operated at 44 MHz with
2.75 MHz bandwidth. Out of 4,500 triggers a clear bandwidth-limited radio pulse
was seen in 11 events. This corresponded to a cosmic ray trigger threshold of
5x10^16 eV and was of intensity close to that predicted. The early experiments
which followed this discovery and their interpretation is described.


title: Superfluid vortices in neutron stars

abstract:
  A microscopic, quantum mechanical model for neutron vortices in the crust of
a neutron star is presented. After a brief introduction to the Bogoliubov- de
Gennes equations, which form the basis for our calculations, we present results
for density distributions, vortex core sizes and vortex energies, both for an
isolated neutron vortex and for the case when the vortex core overlaps with a
cylindrical nucleus. Earlier results on the vortex core size are confirmed,
indicating a much less dramatic variation of the vortex core size with density
than predicted by the BCS formula.


title: Quintessence and Cosmic Microwave Background

abstract:
  Analytic formulas for the position of the first acoustic peak in the CMB are
derived and discussed. They are generalized to the case of a time-dependent
dark energy component and it is shown how the cosmic parameters $\Omega_M$ and
$\Lambda_{\Lambda}$, extracted from observations, have an intrinsic uncertainty
until one knows whether the dark energy density is, or is not, time dependent.


title: A Search for OH Megamasers at z > 0.1. II. Further Results

abstract:
  We present current results of an ongoing survey for OH megamasers in luminous
infrared galaxies at the Arecibo Observatory. The survey is now two-thirds
complete, and has resulted in the discovery of 35 new OH megamasers at z > 0.1,
24 of which are presented in this paper. We discuss the properties of each
source in detail, including an exhaustive survey of the literature. We also
place upper limits on the OH emission from 107 nondetections and list their IR,
radio, and optical properties. The survey detection rate is 1 OH megamaser for
every 6 candidates overall, but is a strong function of the far IR luminosity
of candidates and may depend on merger stage or on the central engine
responsible for the IR luminosity in the merging galaxy pair. We also report
the detection of IRAS 12032+1707, a new OH gigamaser.


title: Optical photometry of V4334 Sgr (Sakurai's Object)

abstract:
  The optical photometric evolution of the final helium flash object V4334 Sgr
from 1994 to 2000 is described. The rise to optical maximum (1994 - 1996) is
characterized by a continuous increase of color indices, indicating a slowly
expanding, cooling pseudo-photosphere. This photosphere became stationary in
1997. In the following years, the object underwent brightness declines of
increasing strength, which are similar in character to the ``red declines'' of
R CrB stars. The fading of V4334 Sgr is more dramatic than any brightness
decline of an R CrB star: at present, only 1/100000 of the visual light reaches
the observer. Most radiation is absorbed by the dust envelope and re-radiated
in the infrared. The sparse optical data of 2000 show that the obscuration has
not increased in strength any more. The light curve of V4334 Sgr is similar to
that of the final helium flash object V605 Aql which erupted in 1919.


title: The light curve of V605 Aql

abstract:
  ``Nova Aquilae No. 4'', discovered in 1919, later renamed V605 Aql, was
recognized to be a final helium flash object only in the 1980s. Clayton and De
Marco (1997) gave a detailed description of the available spectroscopic and
photometric material. Here we try to re-analyze the photometric record. The
photographic material is still available and has been used to construct a
revised light curve. Only fragments of the visual observations were published;
the remainder appears to be lost.


title:
Discovery of Associated Absorption Lines in an X-Ray Warm Absorber:
  HST-FOS Observations of MR2251-178

abstract:
  The presence of a ``warm absorber'' was first suggested to explain spectral
variability in an X-ray spectrum of the radio-quiet QSO MR2251-178. A unified
picture, in which X-ray warm absorbers and ``intrinsic'' UV absorbers are the
same, offers the opportunity to probe the nuclear environment of active
galactic nuclei. To test this scenario and understand the physical properties
of the absorber, we obtained a UV spectrum of MR2251-178 with the Faint Object
Spectrograph (FOS) onboard the Hubble Space Telescope (HST). The HST spectrum
clearly shows absorption due to Ly-alpha, NV and CIV, blueshifted by 300 km/sec
from the emission redshift of the QSO. The rarity of both X-ray and UV
absorbers in radio-quiet QSOs suggests these absorbers are physically related,
if not identical. Assuming the unified scenario, we place constraints on the
physical parameters of the absorber and conclude the mass outflow rate is
essentially the same as the accretion rate in MR2251-178.


title: Unitarity Bounds and the Cuspy Halo Problem

abstract:
  Conventional Cold Dark Matter cosmological models predict small scale
structures, such as cuspy halos, which are in apparent conflict with
observations. Several alternative scenarios based on modifying fundamental
properties of the dark matter have been proposed. We show that general
principles of quantum mechanics, in particular unitarity, imply interesting
constraints on two proposals: collisional dark matter proposed by Spergel &
Steinhardt, and strongly annihilating dark matter proposed by Kaplinghat, Knox
& Turner. Efficient scattering required in both implies m < 12 GeV and m < 25
GeV respectively. The same arguments show that the strong annihilation in the
second scenario implies the presence of significant elastic scattering,
particularly for large enough masses. Recently, a variant of the collisional
scenario has been advocated to satisfy simultaneously constraints from dwarf
galaxies to clusters, with a cross section that scales inversely with velocity.
We show that this scenario likely involves super-elastic processes, and the
associated kinetic energy change must be taken into account when making
predictions. Exceptions and implications for experimental searches are
discussed.


title: Gas, Dust, and Young Stars in the Outer Disk of M 31

abstract:
  Using the Canada-France-Hawaii Telescope we have obtained deep
high-resolution CCD images in V and I of a 28'x28' field in the outer disk of M
31 at ~ 116' from the center along the major axis to the south-west, and
covering a range of projected galactocentric distance from about 23 to 33 kpc.
The field was chosen to correspond with extended HI features recorded near the
HI edge of the galaxy.
  The many tens of thousands of objects detected in this large field have been
classified using an automatic algorithm which distinguishes unresolved from
resolved structures and provides photometry on them. For the most part the
unresolved objects are stars in M 31. The V-I colors of these stars are highly
correlated with the column density of HI in the field. Assuming a Galactic
extinction law, this yields a minimum extinction/atomic-gas ratio about 1/3 of
that in the Solar neighbourhood. The ISM in this outer disk of M 31 therefore
contains substantial amounts of dust.
  We have identified a population of B stars in the field whose distribution is
also well correlated with the extended HI distribution. Evidently, star
formation is both ongoing and wide spread in the outer disk of M 31. According
to the current view of the star formation process, molecular gas is therefore
also expected to be present.


title: A New SX Phe Star in the Globular Cluster M15

abstract:
  A new SX Phe star (labelled SXP1) found from $BV$ CCD photometry is the first
to be discovered in the globular cluster M15. It is a blue straggler and is
located $102\arcsec.8$ north and $285\arcsec.6$ west of the center of M15
\citep{har96}. Mean magnitudes of SXP1 are $<$$B$$>$ = 18$\fm$671 and $<$$V$$>$
= 18$\fm$445. The amplitude of variability of SXP1 is measured to be $\Delta V
\approx 0.15$. From multiple-frequency analysis based on the Fourier
decomposition method, we detect two very closely separated pulsating
frequencies: the primary frequency at $f_1=24.630$ c/d for both $B$- and
$V$-bands, and the secondary frequency at $f_2=24.338$ c/d for the $B$-band and
24.343 c/d for the $V$-band. This star is the second among known SX Phe stars
found to pulsate with very closely separated frequencies ($f_2/f_1\ge0.95$).
These frequencies may be explained by excitation of nonradial modes; however,
we have an incomplete understanding of this phenomenon in the case of SX Phe
stars with relatively high amplitudes. The metallicity-period and the
variability amplitude-period relations for SXP1 in M15 are found to be
consistent with those for SX Phe stars in other globular clusters.


title:
Sunyaev-Zel'dovich Predictions for the Planck Surveyor Satellite using
  the Hubble Volume Simulations

abstract:
  We use the billion-particle Hubble Volume simulations to make statistical
predictions for the distribution of galaxy clusters that will be observed by
the Planck Surveyor satellite through their effect on the cosmic microwave
background -- the Sunyaev-Zel'dovich effect. We utilize the lightcone datasets
for both critical density (tauCDM) and flat low-density (LambdaCDM)
cosmologies: a `full-sky' survey out to $z \sim 0.5$, two `octant' datasets out
to beyond $z=1$ and a 100 square degree dataset extending to $z \sim 4$. Making
simple, but robust, assumptions regarding both the thermodynamic state of the
gas and the detection of objects against an unresolved background, we present
the expected number of SZ sources as a function of redshift and angular size,
and also by flux (for both the thermal and kinetic effects) for 3 of the
relevant HFI frequency channels. We confirm the expectation that Planck will
detect around $5\times 10^4$ clusters, though the exact number is sensitive to
the choice of several parameters including the baryon fraction, and also to the
cluster density profile, so that either cosmology may predict more clusters. We
also find that the majority of detected sources should be at $z<1.5$, and we
estimate that around one per cent of clusters will be spatially resolved by
Planck, though this has a large uncertainty.


title: Solar models and electron screening

abstract:
  We investigate the sensitivity of the solar model to changes in the nuclear
reaction screening factors. We show that the sound speed profile as determined
by helioseismology certainly rules out changes in the screening factors
exceeding more than 10%. A slightly improved solar model could be obtained by
enhancing screening by about 5% over the Salpeter value. We also discuss how
envelope properties of the Sun depend on screening, too. We conclude that the
solar model can be used to help settling the on-going dispute about the
``correct'' screening factors.


title:
The Munich Near-Infrared Cluster Survey - I. Field selection, object
  extraction, and photometry

abstract:
  The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep,
photometric survey selected in the K' band. It covers an area of roughly one
square degree in the K' and J near-IR pass-bands. The survey area consists of
16 6' x 6' fields targeted at QSOs with redshifts 0.5 < z < 2 and 7 28' x 13'
stripes targeted at `random' high Galactic latitude fields. Ten of the QSO
fields were additionally imaged in R and I, and 0.6 square degrees of the
randomly selected fields were also imaged in the V, R, and I bands. The
resulting object catalogues were strictly selected in K', having a limiting
magnitude (50 per cent completeness) of K' ~ 19.5 mag and J ~ 21 mag,
sufficiently deep to detect passively evolving systems up to a redshift of z ~
1.5 and luminosity of 0.5 L*. The optical data reach a depth of roughly R ~
23.5 mag. The project's main scientific aims are the identification of galaxy
clusters at redshifts around unity and the selection of a large sample of field
early-type galaxies at 0 < z < 1.5 for evolutionary studies. In this paper -
the first in a series - we describe the survey's concept, the selection of the
survey fields, the near-IR and optical imaging and data reduction, object
extraction, and the construction of photometric catalogues. Finally, we show
the J-K' vs. K' colour-magnitude diagramme and the R-J vs. J-K', V-I vs. J-K',
and V-I vs. V-R colour-colour diagrammes for MUNICS objects, together with
stellar population-synthesis models for different star-formation histories, and
conclude that the data set presented is suitable for extracting a catalogue of
massive field galaxies in the redshift range 0.5 < z < 1.5 for evolutionary
studies and follow-up observations.


title: Dynamics of Cosmological Models in the Brane-world Scenario

abstract:
  We present the results of a systematic investigation of the qualitative
behaviour of the Friedmann-Lemaitre-Robertson-Walker (FLRW) and Bianchi I and V
cosmological models in Randall-Sundrum brane-world type scenarios.


title:
Monitoring of the optical and 2.5-11.7 micron spectrum and mid-IR
  imaging of the Seyfert 1 galaxy Mrk279 with ISO

abstract:
  Mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO
satellite are presented together with the results of a one-year monitoring
campaign of the 2.5-11.7 micron spectrum. Contemporaneous optical photometric
and spectrophotometric observations are also presented. The galaxy appears as a
point-like source at the resolution of the ISOCAM instrument, 4-5". The
2.5-11.7 micron average spectrum of the nucleus in Mrk 279 shows a strong power
law continuum with a spectral index alpha = -0.80+/-0.05 and weak PAH emission
features. The Mrk 279 spectral energy distribution shows a mid-IR bump, which
extends from 2 to 15-20 micron . The mid-IR bump is consistent with thermal
emission from dust grains at a distance of >= 100 light-days. No significant
variations of the mid-IR flux have been detected during our observing campaign,
consistent with the relatively low amplitude (~10 % rms) of the optical
variability during the campaign. The time delay for the Hbeta line emission in
response to the optical continuum variations is 16.7 +5.3/5.6 days, consistent
with previous measurements.


title: The peculiar B-type supergiant HD327083

abstract:
  Coude spectroscopic data of a poorly-studied peculiar supergiant, HD327083,
are presented. Halpha and Hbeta line profiles have been fitted employing a
non-LTE code adequate for spherically expanding atmospheres. Line fits lead to
estimates of physical parameters. These parameters suggest that HD327083 may be
close to the Luminous Blue Variable phase but it is also possible that it could
be a B[e] Supergiant.


title: The cosmological evolution of colour gradients in spheroids

abstract:
  The analysis of the four-colour maps of galaxies in the Hubble Deep Field has
revealed in the sample of 0.4<z<1 early-type field galaxies the existence of
ellipticals with a predominantly old coeval stellar population. However, there
is another, unexpected, category of HDF early-type galaxies, in which the
galaxy core is significantly bluer than the outer regions. We demonstrate that
these colour gradients are predicted by the multi-zone chemodynamical model for
the evolution of elliptical galaxies. We suggest that the colour gradient could
be used as a chronometer of the evolution of elliptical galaxies: galaxies
younger than a few Gyr exhibit cores bluer than the surrounding galaxy, due to
ongoing star formation, while more evolved galaxies have redder cores, due to
metallicity gradients increasing towards the centre.


title: The angular diameter and distance of the Cepheid Zeta Geminorum

abstract:
  Cepheids are the primary distance indicators for extragalactic astronomy and
therefore are of very high astrophysical interest. Unfortunately, they are rare
stars, situated very far from Earth.Though they are supergiants, their typical
angular diameter is only a few milliarcseconds, making them very challenging
targets even for long-baseline interferometers. We report observations that
were obtained in the K prime band (2-2.3 microns), on the Cepheid Zeta
Geminorum with the FLUOR beam combiner, installed at the IOTA interferometer.
The mean uniform disk angular diameter was measured to be 1.64 +0.14 -0.16 mas.
Pulsational variations are not detected at a significant statistical level, but
future observations with longer baselines should allow a much better estimation
of their amplitude. The distance to Zeta Gem is evaluated using Baade-Wesselink
diameter determinations, giving a distance of 502 +/- 88 pc.


title: INTEGRAL capabilities for faint Gamma-Ray Bursts

abstract:
  We discuss the INTEGRAL capabilities to detect a high redshift population of
gamma-ray bursts (GRBs). First a simple comparison between other past or
planned experiments (BATSE, SAX, HETE-2, Romer, Swift) and INTEGRAL
instrumentation (IBIS, JEM-X) is shown. After this first view we will be
focused on comparing the capabilities of the two most sensitive missions
(INTEGRAL/IBIS and Swift) of detecting a further population of GRBs. We
conclude that, if the GRB rate is proportional to the star formation rate, the
capabilities of studying GRBs of INTEGRAL are complementary to the ones of
missions like Swift and HETE-2, specially devoted to prompt localizations of
GRBs. Whereas Swift and HETE-2 would detect a higher number of GRBs than
INTEGRAL (~8 and ~22 more detections than IBIS and JEM-X respectively),
INTEGRAL and specially IBIS would detect very high redshift (z > 15) GRBs,
unreachable for Swift and HETE-2. This fact is very relevant for studying a
population of GRBs further than z=15, which would be associated with the
population III of stars. Therefore, the INTEGRAL mission (precisely IBIS) will
be a very valuable tool to trace the primitive star formation rate at the early
universe.


title:
Discovery of pulsations from the Be/X-ray binary RX J0101.3-7211 in the
  SMC by XMM-Newton

abstract:
  We report pulsations in the X-ray flux of RX J0101.3-7211 in the Small
Magellanic Cloud (SMC) with a period of 455+/-2 s in XMM-Newton EPIC-PN data.
The X-ray spectrum can be described by a power-law with a photon index of
0.6+/-0.1. Timing analysis of ROSAT PSPC and HRI archival data confirms the
pulsations and indicates a period increase of ~5 s since 1993. RX J0101.3-7211
varied in brightness during the ROSAT observations with timescales of years
with a maximum unabsorbed flux of 6 x 10^-13 erg cm^-2 s^-1 (0.1 - 2.4 keV).
The flux during the XMM-Newton observation in the ROSAT band was lower than
during the faintest ROSAT detection. The unabsorbed luminosity derived from the
EPIC-PN spectrum is 2 x 10^35 erg s^-1 (0.2 - 10.0 keV) assuming a distance of
60 kpc. Optical spectra of the proposed counterpart taken at the 2.3 m
telescope of MSSSO in Australia in August 2000 show strong Halpha emission and
indicate a Be star. The X-ray and optical data confirm RX J0101.3-7211 as a
Be/X-ray binary pulsar in the SMC.


title: Observation of a Black-Hole X-ray Nova in Outburst with INTEGRAL

abstract:
  We simulate the observation of a bright Nova Musca-like X-ray nova during
outburst with INTEGRAL, the next ESA gamma-ray space observatory. We will show
how performances of the INTEGRAL instruments allow deep study of X-ray Novae
and will evaluate the scientific output that INTEGRAL will provide on this
class of transient gamma-ray sources, which are now believed to contain black
holes in low mass binary systems. The variable high-energy feature around 511
keV observed from X-ray Nova Musca in 1991 by the SIGMA telescope would be
detected by INTEGRAL at very high significance level. INTEGRAL data will permit
to set important constraints on the models and allow to distinguish between
electron-positron or nuclear de-excitation origin of the line. Characteristic
spectral and timing features detected by INTEGRAL instruments over a very large
energy band will also provide clues to understand physics of accretion in these
black holes binaries and in particular to distinguish between thermal and
non-thermal origin of radiation and to assess the role of bulk motion
comptonization.


title: INTEGRAL observations of Galaxy Clusters

abstract:
  Cluster of galaxies are the largest concentrations of visible mass in the
Universe and therefore a fundamental topic of cosmology and astrophysics.
Recent radio, EUV, and X-ray observations suggest that clusters contain large
populations of diffuse nonthermal relativistic and/or superthermal particles.
These particles may be produced by acceleration in cluster merger shocks, AGNs,
and/or supernovae in cluster galaxies. Models for the nonthermal populations in
clusters indicate that they should produce substantial hard X-ray and $\gamma$
luminosities. The possible role of nonthermal particles in the dynamics of
clusters is one of the greatest uncertainties in their use as cosmological
probes. INTEGRAL offers, for the first time, the possibility of simultaneous
medium resolution imaging (~ 12 arcmin) and high resolution spectroscopy
(DeltaE/E ~ 2 keV @ 1.3 MeV) with exceptional sensitivity in the hard
X-ray/soft gamma-ray band. The spatial resolution will allow discrete sources,
such as AGNs, to be separated from the diffuse emission of the cluster. For
nearby clusters, the spatial distribution of emission can be determined and
compared to models for the nonthermal particle populations and observations in
other wavebands. The spectral capabilities may allow different components of
the nonthermal population to be detected separately. We present simulations of
INTEGRAL observations of nearby galaxy clusters that show its capability for
detecting the different phenomena responsible of clusters emission.


title:
Deep VLT spectroscopy of high redshift radio galaxy MRC 2104-242:
  Evidence for a metallicity gradient

abstract:
  In this contribution we will present deep VLT spectroscopy observations of
the giant emission line halo around the z=2.49 radio galaxy MRC 2104-242. The
morphology of the halo is dominated by two spatially resolved regions. Lya is
extended by >12" along the radio axis, C IV and He II are extended by ~8". The
overall spectrum is typical for that of high redshift radio galaxies.
Interestingly, N V is present in the spectrum of the region associated with the
center of the galaxy hosting the radio source, the northern region, while
absent in the southern region. Using a simple photoionization model, the
difference in N V can be explained due to a metallicity gradient within the
halo. This is consistent with a scenario in which the halo is formed by a
massive cooling flow or originates from the debris of the merging of two or
more galaxies. However, also other mechanisms such as jet-cloud interactions or
starburst-winds could be important.


title:
3-D ionization structure (in stereoscopic view) of Planetary Nebulae:
  the case of NGC 1501

abstract:
  Long-slit echellograms of the high excitation planetary nebula NGC1501,
reduced according to the methodology developed by Sabbadin et al. (2000a, b),
allowed us to obtain the ``true'' distribution of the ionized gas in the eight
nebular slices covered by the spectroscopic slit. A 3-D rendering procedure is
described and applied, which assembles the tomographic maps and rebuilds the
spatial structure. The images of NGC 1501, as seen in 12 directions separated
by 15 deg, form a series of stereoscopic pairs giving surprising 3-D views in
as many directions. The main nebula consists of an almost oblate ellipsoid of
moderate ellipticity (a=44 arcsec, a/b=1.02, a/c=1.11), brighter in the
equatorial belt, deformed by several bumps, and embedded in a quite
homogeneous, inwards extended cocoon. Some reliability tests are applied to the
rebuilt nebula; the radial matter profile, the small scale density fluctuations
and the 2-D (morphology) - 3-D (structure) correlation are presented and
analysed. The wide applications of the 3-D reconstruction to the morphology,
physical conditions, ionization parameters and evolutionary status of expanding
nebulae in general (planetary nebulae, nova and supernova remnants, shells
around Population I Wolf-Rayet stars, nebulae ejected by symbiotic stars,
bubbles surrounding early spectral type main sequence stars etc.) are
introduced.


title: Gamma ray bursts from superconducting cosmic strings

abstract:
  Cusps of superconducting strings can serve as GRB engines. A powerful beamed
pulse of electromagnetic radiation from a cusp produces a jet of accelerated
particles, whose propagation is terminated by the shock responsible for GRB. A
single free parameter, the string scale of symmetry breaking $\eta \sim 10^{14}
GeV$, together with reasonable assumptions about the magnitude of cosmic
magnetic fields and the fraction of volume that they occupy, explains the GRB
rate, duration and fluence, as well as the observed ranges of these quantities.
The wiggles on the string can drive the short-time structures of GRB. This
model predicts that GRBs are accompanied by strong bursts of gravitational
radiation which should be detectable by LIGO, VIRGO and LISA detectors. Another
prediction is the diffuse X- and gamma-ray radiation at 8 MeV - 100 GeV with a
spectrum and flux comparable to the observed. The weakness of the model is the
prediction of too low rate of GRBs from galaxies, as compared with
observations. This suggests that either the capture rate of string loops by
galaxies is underestimated in our model, or that GRBs from cusps are
responsible for only a subset of the observed GRBs not associated with
galaxies.


title: Hydrodynamical simulations of the Lyman-Alpha forest: data comparisons

abstract:
  Numerical hydrodynamical simulations are used to predict the expected
absorption properties of the Lyman-Alpha forest for a variety of Cold Dark
Matter dominated cosmological scenarios: CHDM, OCDM, LCDM, SCDM, and tCDM.
Synthetic spectra are constructed duplicating the resolution, signal-to-noise
ratio, and wavelength coverage of several published high resolution spectra,
and their statistical properties compared on the basis of the flux distribution
of the spectra, the distribution of coefficients in a wavelet decomposition of
the spectra, and the distributions of absorption line profile parameters.
Agreement between the measured and predicted cumulative distributions is found
at the few to several percent level. The best-fitting models to the flux
distribution correspond to normalizations on the scale of the cosmological
Jeans length of 1.3 < sigma_J < 1.7 at z=3. No single model provides an
acceptable match to all the distributions. Larger median Doppler parameters are
found in the measured spectra than predicted by all but the lowest
normalization models (CHDM and tCDM), which provide poor fits to the flux
distributions. The discrepancy in Doppler parameters is particularly large for
absorption systems optically thin at the Lyman-Alpha line-centre. This may
indicate the need to introduce additional energy injection throughout the IGM,
as may be provided by late HeII reionization (z_HeII~3.5) or supernovae-driven
winds from young galaxies. The models require a hydrogen ionization rate at
redshifts 1.7<z<3.5 within a factor of 2 of that predicted from QSOs alone as
the sources of the UV photoionization background, although with a slower rate
of decline with redshift at z>3.5 than predicted from current QSO counts.


title:
The effect of distant large scale structure on weak lensing mass
  estimates

abstract:
  We quantify the uncertainty in weak lensing mass estimates of clusters of
galaxies, caused by distant (uncorrelated) large scale structure along the line
of sight. We find that the effect is fairly small for deep observations
(20<R<26) of massive clusters (sigma=1000 km/s) at intermediate redshifts,
where the bulk of the sources are at high redshifts compared to the cluster
redshift. If the lensing signal is measured out to 1.5 h_{50}^{-1} Mpc the
typical 1sigma relative uncertainty in the mass is about 6%. However, in other
situations the induced uncertainty can be larger. For instance, in the case of
nearby clusters, such as the Coma cluster, background structures introduce a
considerable uncertainty in the mass, limiting the maximum achievable S/N-ratio
to \sim 7, even for deep observations. The noise in the cluster mass estimate
caused by the large scale structure increases with increasing aperture size,
which will also complicate attempts to constrain cluster mass profiles at large
distances from the cluster centre. However, the distant large scale structure
studied here can be considered an additional (statistical) source of error, and
by averaging the results of several clusters the noise is decreased.


title:
Stellar luminosity functions of rich star clusters in the Large
  Magellanic Cloud

abstract:
  We show the results of deep V and I HST photometry of 6 rich star clusters in
the Large Magellanic Cloud with different ages and metallicities. The number of
stars with measured magnitudes in each cluster varies from about 3000 to 10000.
We build stellar density and surface brightness profiles for the clusters and
extract half-light radii and other structural parameters for each. We also
obtain luminosity functions, Phi (Mv), down to Mv ~ 6 (m/msun > 0.6), and
investigate their dependence with distance from the cluster centre well beyond
their half-light radius. In all clusters we find a systematic increase in the
luminosity function slope with radial distance from the centre. Among the
clusters displaying significant mass segregation are the two youngest in the
sample: NGC 1805 and NGC 1818. For these two clusters we obtain present-day
mass functions. The NGC 1818 mass function is in excellent agreement with that
derived by other authors, also using HST data. They young cluster mass function
slopes differ, that of NCG 1805 being systematically steeper than NGC 1818.
Since these are very young stellar systems (age < 40 Myrs), these variations
may reflect the initial conditions rather than evolution due to internal
dynamics.


title: Chandra Observations of Two High-Redshift Quasars

abstract:
  We report the first high-resolution X-ray spectra of two high-redshift
quasars, S5 0836+710 and PKS 2149-306, obtained with the Chandra High Energy
Transmission Grating Spectrometer (HETGS). The primary goal of this observation
is to use the high spectral resolving power of the HETGS to detect X-ray
absorption produced by a hot intergalactic medium. The continuum of both
quasars can be fitted by absorbed power laws. The power law photon index
(Gamma) of S5 0836+710 is consistent with that found in previous observations
with ROSAT and ASCA, while the power law of PKS 2149-306 is harder than found
in a previous observation by ASCA. Excess continuum absorption above the
Galactic value is found in S5 0836+710, as evidenced in ASCA and ROSAT
observations. No significant emission or absorption feature is detected in
either source at 3 sigma level. Based on the detection limits we constrain the
properties of possible emitters and absorbers. The upper limit of the
equivalent width of Fe K emission lines could be as low as ~ 10 eV. Absorbers
with a column density higher than 8e16 cm^{-2} for O VIII or 5e16 cm^{-2} for
Si XIV would have been detected. We propose a method to constrain the
cosmological parameters (namely Omega_0 and Omega_b) via the X-ray forest
theory, but current data do not give significant constraints. However, we
estimate that observing ~ 7 bright quasars should give at least one O VIII and
more O VII absorption lines at 95% possibility. We also find that combined with
the constraints from the distortion of the CMB spectrum, the X-ray
Gunn-Peterson test can marginally constrain a uniform, enriched IGM.


title:
The prompt energy release of gamma-ray bursts using a cosmological
  k-correction

abstract:
  The fluences of gamma-ray bursts (GRBs) are measured with a variety of
instruments in different detector energy ranges. A detailed comparison of the
implied energy releases of the GRB sample requires, then, an accurate
accounting of this diversity in fluence measurements which properly corrects
for the redshifting of GRB spectra. Here, we develop a methodology to
``k-correct'' the implied prompt energy release of a GRB to a fixed co-moving
bandpass. This allows us to homogenize the prompt energy release of 17
cosmological GRBs (using published redshifts, fluences, and spectra) to two
common co-moving bandpasses: 20-2000 keV and 0.1 keV-10 MeV (``bolometric'').
While the overall distribution of GRB energy releases does not change
significantly by using a k-correction, we show that uncorrected energy
estimates systematically undercounts the bolometric energy by ~5% to 600%,
depending on the particular GRB. We find that the median bolometric
isotropic-equivalent prompt energy release is 2.2 x 10^{53} erg with an r.m.s.
scatter of 0.80 dex. The typical estimated uncertainty on a given k-corrected
energy measurement is ~20%.


title: Redshift-Space Distortions of Group and Galaxy Correlations

abstract:
  The two-point correlation function is computed for galaxies and groups of
galaxies selected using 3-dimensional information from the Updated Zwicky
Galaxy Catalog - (UZC). The redshift space distortion of the correlation
function $\xi(\sigma,\pi)$ in the directions parallel and perpendicular to the
line of sight, induced by pairwise group peculiar velocities is evaluated. Two
methods are used to characterize the pairwise velocity field of groups and
galaxies. The best fitting parameters are $\gamma=-1.89 \pm 0.17$ and $r_0=9.7
\pm 4.5$ $h^{-1}$ Mpc for groups, and $\gamma=-2.00 \pm 0.03$ and $r_0=5.29 \pm
0.21$ $h^{-1}$ Mpc for galaxies. We find $\beta_{gx}=0.51 \pm 0.15$ for
galaxies, while for groups we obtain a noisy estimate $\beta < 1.5$.


title: Modern theory of Fermi acceleration: a new challenge to plasma physics

abstract:
  One of the main features of astrophysical shocks is their ability to
accelerate particles to extremely high energies. The leading acceleration
mechanism, the diffusive shock acceleration is reviewed. It is demonstrated
that its efficiency critically depends on the injection of thermal plasma into
acceleration which takes place at the subshock of the collisionless shock
structure that, in turn, can be significantly smoothed by energetic particles.
Furthermore, their inhomogeneous distribution provides free energy for MHD
turbulence regulating the subshock strength and injection rate. Moreover, the
MHD turbulence confines particles to the shock front controlling their maximum
energy and bootstrapping acceleration. Therefore, the study of the MHD
turbulence in a compressive plasma flow near a shock is a key to understanding
of the entire process. The calculation of the injection rate became part of the
collisionless shock theory. It is argued that the further progress in diffusive
shock acceleration theory is impossible without a significant advance in these
two areas of plasma physics.


title: Properties of Globular Cluster Systems in Nearby Early-type Galaxies

abstract:
  We present a study of globular clusters (GCs) in 17 relatively nearby
early-type galaxies, based on deep HST/WFPC2 F555W and F814W images. We compare
color distributions, cluster sizes and luminosity functions with those of GCs
in the Milky Way. In nearly all cases, a KMM test returns a high confidence
level for the hypothesis that a sum of two Gaussians provides a better fit to
the observed color distribution than a single Gaussian, although histograms of
the V-I distribution are not always obviously bimodal. The blue and red peak
colors both correlate with absolute host galaxy B band magnitude and central
velocity dispersion (at about the 2-3 sigma level), but we see no clear
correlation with host galaxy V-I or J-K color. Red GCs are generally smaller
than blue GCs by about 20%. The size difference is seen at all radii and exists
also in the Milky Way and Sombrero (M104) spiral galaxies. Fitting t5 functions
to the luminosity functions of blue and red GC populations separately, we find
that the V-band turn-over of the blue GCs is generally brighter than that of
the red ones by about 0.3 mag, as expected if the two GC populations have
similar ages and mass distributions but different metallicities. Brighter than
M_V ~ -7.5, the luminosity functions (LFs) are well approximated by power-laws
with an exponent of about -1.75. This is similar to the LF for young star
clusters, suggesting that young and old globular clusters form by the same
basic mechanism. We discuss scenarios for GC formation and conclude that our
data appear to favor ``in-situ'' models in which all GCs in a galaxy formed
after the main body of the proto-galaxy had assembled into a single potential
well.


title:
Correlations Between Spectral Properties and Spin-Down Rate in Soft
  Gamma-Ray Repeaters and Anomalous X-ray Pulsars

abstract:
  Anomalous x-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are x-ray
sources with unusual properties distinguishing them from both rotation-powered
and most accretion-powered pulsars. Using archival ASCA data over the energy
range 0.5-10.0 keV, we have studied the spectra of the persistent emission from
these sources and their variation with spin-down rate. Using a single power law
spectral model, we find that the overall hardness of the spectra increase with
increasing spin-down rate, and therefore the spectral and spin-down mechanism
are inextricably linked in these objects. In terms of the two-component
blackbody plus power law spectral models, this correlation is seen as an
increasing hardness of the high energy component with increasing spin-down
rate, with the temperature of the low energy blackbody component remaining
essentially constant. Also for the two component spectral model: the ratio of
the 2-10 keV power law and bolometric blackbody luminosities gradually
increases with the spin-down rate. We discuss these results in terms of the
various theoretical models for SGRs and AXPs.


title:
Wide-field (sub)millimeter continuum surveys of protoclusters: Clues to
  the origin of the IMF

abstract:
  Recent (sub)millimeter continuum surveys of nearby star-forming regions have
revealed a wealth of new, cold cloud fragments. Those which are small-scale
(diameter < 10000 AU), starless, and gravitationally bound are good candidates
for being the direct progenitors of protostars, i.e., the structures within
which individual protostellar collapse is initiated. The mass spectrum of these
protocluster condensations is reminiscent of the stellar initial mass function
(IMF), suggesting the IMF is partly determined by cloud fragmentation at the
pre-stellar stage of star formation.


title: Young Supernova Remnants in the Magellanic Clouds

abstract:
  There are a half-dozen or so young supernova remnants in the Magellanic
Clouds that display one or more of the following characteristics: high velocity
(>1000 km/s) emission, enhanced metallicity, or a rapidly rotating pulsar. I
summarize the current state of knowledge of these remnants and present some
recent results mostly from the new X-ray astronomy satellites.


title:
Cosmic Microwave Background polarization and the ionization history of
  the Universe

abstract:
  We point out that polarization measurements as planned for the upcoming
PLANCK mission can significantly enhance the accuracy of cosmic parameter
estimation compared to the temperature anisotropy spectrum alone. In order to
illustrate this, we consider a standard cosmological model and several
modifications that adjust one parameter each to fit the recently published
Maxima-1 data. While all models produce acceptable fits as far as the power
spectrum is concerned, their corresponding polarization spectra differ widely.
The strongest differences are expected for a model with delayed recombination,
reflecting the fact that polarization measurements are most sensitive to the
processes governing the epoch of recombination.


title: Formation of High Mass X-ray Black Hole Binaries

abstract:
  The discrepancy in the past years of many more black-hole soft X-ray
transients (SXTs), of which a dozen have now been identified, had challenged
accepted wisdom in black hole evolution. The sheer number of inferred SXTs
requires that many, if not most, stars of ZAMS masses $20-35\msun$ end up as
black holes (Portegies Zwart et al. 1997; Ergma & van den Heuvel 1998). In this
paper we show that this can be understood by challenging the accepted wisdom
that the result of helium core burning in a massive star is independent of
whether the core is covered by a hydrogen envelope, or "naked" while it burns.
The latter case occurs in binaries when the envelope of the more massive star
is transferred to the companion by Roche Lobe overflow while in either main
sequence or red giant stage. For solar metallicity, whereas the helium cores
which burn while naked essentially never go into high-mass black holes, those
that burn while clothed do so, beginning at ZAMS mass $\sim 20\msun$, the
precise mass depending on the $^{12}C(\alpha,\gamma)^{16}$O rate as we outline.
In this way the SXTs can be evolved, provided that the H envelope of the
massive star is removed only following the He core burning. We also show that
in order to evolve a black hole of mass $\gsim 10\msun$ such as observed in Cyg
X-1, even employing extremely massive progenitors of ZAMS mass $\gsim 60\msun$
for the black hole, the core must be covered by hydrogen during a substantial
fraction of the core burning. In other words, the progenitor must be a WNL
star. We evolve Cyg X-1 in an analogous way to which the SXTs are evolved, the
difference being that the companion in Cyg X-1 is more massive than those in
the SXTs, so that Cyg X-1 shines continuously.


title:
Emissivity Statistics in Turbulent, Compressible MHD Flows and the
  Density-Velocity Correlation

abstract:
  In this paper we test the results of a recent analytical study by Lazarian
and Pogosyan, on the statistics of emissivity in velocity channel maps, in the
case of realistic density and velocity fields obtained from numerical
simulations of MHD turbulence in the interstellar medium (ISM). To compensate
for the lack of well-developed inertial ranges in the simulations due to the
limited resolution, we apply a procedure for modifying the spectral slopes of
the fields while preserving the spatial structures. We find that the density
and velocity are moderately correlated in space and prove that the analytical
results by Lazarian and Pogosyan hold in the case when these fields obey the
fluid conservation equations. Our results imply that the spectra of velocity
and density can be safely recovered from the position-position-velocity (PPV)
data cubes available through observations, and confirm that the relative
contributions of the velocity and density fluctuations to those of the
emissivity depend on the velocity resolution used and on the steepness of the
density spectral index. Furthermore, this paper supports previous reports that
an interpretation of the features in the PPV data cubes as simple density
enhancements (i.e., ``clouds'') can be often erroneous, as we observe that
changes in the velocity statistics substantially modify the statistics of
emissivity within the velocity data cubes.


title: Evidence For Intrinsic Magnetic Moments in Black Hole Candidates

abstract:
  We present evidence that the power law part of the quiescent x-ray emissions
of neutron stars in low mass x-ray binaries is magnetospheric in origin. It can
be very accurately calculated from known rates of spin and magnetic moments
determined from the the $\sim 10^{3 - 4}$ times brighter luminosity at the
transition to the hard spectral state. This strongly suggests that the spectral
state transition for neutron stars is a magnetospheric propeller effect. We
test the hypothesis that the similar spectral state switches and quiescent
power law emissions of the black hole candidates might also be magnetospheric
effects. In the process we derive proposed magnetic moments and rates of spin
for them and accurately predict their quiescent luminosities. This constitutes
an observational test for the physical realization of event horizons and
suggests that they may not be formed during the gravitational collapse of
ordinary matter.


title:
The Center of Our Galaxy: Activity and High-Energy Emission of the
  Closest Massive Black Hole

abstract:
  The Center of our Galaxy is a peculiar region where a number of crucial
astrophysical phenomena take place, from star formation to SN explosions and
accretion onto a massive black hole. The quest for a massive black hole in the
Galactic Nucleus is of course of particular relevance because, it would be the
closest of such extreme objects, which are now believed to reside in most of
the galactic nuclei of the universe. I will review here the main observational
characteristics of the Galactic Center with particular attention to the the
problem of existence, physical condition and activity of the 3 10E6 Mo black
hole coincident with the compact radio source Sgr A*. I will report historical
and recent results of high energy observations of the central degree of our
Galaxy, along with the specific accretion models proposed to account for the
apparent lack of high energy activity from Sgr A*. The scientific perspectives
of the next X and gamma-ray missions in the domain of the Galactic Center
physics are also mentioned.


title: AGB and Post-AGB Evolution: Structural and Chemical Changes

abstract:
  Structural and chemical changes during the AGB and post-AGB evolution are
discussed with respect to two recent observational and theoretical findings. On
the one hand, high-resolution infrared observations revealed details of the
dynamical evolution of the fragmented, bipolar dust shell around the
far-evolved carbon star IRC+10216 giving evidence for rapid changes of an
already PPN-like structure during the very end of the AGB evolution. On the
other hand, stellar evolution calculations considering convective overshoot
have shown how thermal pulses during the post-AGB stage lead to the formation
of hydrogen-deficient post-AGB stars with abundance patterns consistent with
those observed for Wolf-Rayet central stars.


title: Caustic Crossing in the Gravitational Lens Q2237+0305

abstract:
  The monitoring of the gravitational lens Q2237+0305 carried out by the OGLE
group during 1997--1999 is analyzed. The significant light amplifications in
the C and A quasar components with maxima in mid- and late 1999, respectively,
are interpreted as the crossing of microlens caustics by the source. A
constraint on the emitting-region size R < 10^(15) cm has been obtained from
the light-curve shape by assuming a power-law quasar brightness distribution
(r^2+R^2)^(-p). To estimate the exponent p ~ 1.2 requires refining the standard
model for the quasar continuum formation in an optically thick accretion disk
with p = 1.5


title: Optical Color Gradients in Star-Forming Ring Galaxies

abstract:
  We compute radial color gradients produced by an outwardly propagating
circular wave of star formation and compare our results with color gradients
observed in the classical ring galaxy, the ``Cartwheel''. We invoke two
independent models of star formation in the ring galaxies. The first one is the
conventional density wave scenario, in which an intruder galaxy creates a
radially propagating density wave accompanied by an enhanced star formation
following the Schmidt law. The second scenario is a pure self-propagating star
formation model, in which the intruder only sets off the first burst of stars
at the point of impact. Both models give essentially the same results.
Systematic reddening of B-V, V-K colors towards the center, such as that
observed in the Cartwheel, can be obtained only if the abundance of heavy
elements in the star-forming gas is a few times below solar. The B-V and V-K
color gradients observed in the Cartwheel can be explained as a result of
mixing of stellar populations born in a star-forming wave propagating through a
low-metallicity gaseous disk, and a pre-existing stellar disk of the size of
the gaseous disk with color properties typical to those observed in nearby disk
galaxies.


title: Gamma-Ray Imaging with the Coded Mask IBIS Telescope

abstract:
  The IBIS telescope onboard INTEGRAL, the ESA gamma-ray space mission to be
launched in 2002, is a soft gamma-ray (20 keV - 10 MeV) device based on a coded
aperture imaging system. We describe here basic concepts of coded masks, the
imaging system of the IBIS telescope, and the standard data analysis procedures
to reconstruct sky images. This analysis includes, for both the low-energy
detector layer (ISGRI) and the high energy layer (PICSIT), iterative procedures
which decode recorded shadowgrams, search for and locate sources, clean for
secondary lobes, and then rotate and compose sky images. These procedures will
be implemented in the Quick Look and Standard Analysis of the INTEGRAL Science
Data Center (ISDC) as IBIS Instrument Specific Software.


title:
Star clusterings in the Carina complex: UBVRI photometry of NGC 3324 and
  Loden 165

abstract:
  We report on UBVRI photometry of two $5^{\prime} \times 5^{\prime}$ fields in
the region of the young open cluster NGC 3324. One of our fields covers the
core region, while the other is closer to the tidal radius of the cluster. Our
study provides the first CCD photometry of NGC 3324. We find that the cluster
is very young and probably contains several pre Main Sequence (MS) stars. 25
members are identified on the basis of their position in the (U-B) vs (B-V)
diagram. We investigate the relation of the red super-giant HD 92207 with NGC
3324, suggesting that it probably does not belong to the cluster. Our second
field is close to Loden 165, a possible cluster of stars that has never been
studied so far. We show that this object is a probable open cluster, much older
than NGC 3324 and much closer to the Sun.


title: Symbiotic stars on Asiago archive plates. I

abstract:
  The rich plate archive of the Asiago observatory has been searched for plates
containing the symbiotic stars AS 323, Ap 3-1, CM Aql, V1413 Aql (=AS 338),
V443 Her, V627 Cas (=AS 501) and V919 Sgr. The program objects have been found
on 602 plates, where their brightness has been estimated against the UBVRI
photometric sequences calibrated by Henden and Munari (2000, A&AS 143, 343). AS
323 is probably eclipsing, with a preliminary P=197.6 day period. If confirmed,
it would be the shortest orbital period known among symbiotic stars. CM Aql
does not seem to undergo a series of outbursts, its lightcurve being instead
modulated by a large amplitude sinusoidal variation with a P~1058 day period.
V627 Cas presents a secular trend in agreement with the possible post-AGB
nature of its cool component.


title: Recent developments in the search for baryonic dark matter

abstract:
  Cosmological nucleosynthesis calculations imply that many of the baryons in
the Universe must be dark. We discuss the likelihood that some of these dark
baryons may reside in galaxies as Massive Compact Halo Objects (MACHOs), the
remnants of a first generation of pregalactic or protogalactic stars. Various
candidates have been proposed for such remnants and we review the many types of
observations which can be used to detect or exclude them. Claims to have found
positive evidence for some of the candidates have generally turned out to be
spurious or questionable, so the status of the MACHO scenario remains
controversial. However, it would be premature to reject MACHOs altogether and
further observations are likely to resolve the issue soon.


title:
Primordial black holes as a probe of the early universe and a varying
  gravitational constant

abstract:
  We discuss recent developments in the study of primordial black holes,
focussing particularly on their formation and quantum evaporation. Such studies
can place important constraints on models of the early Universe. An especially
interesting development has been the realization that such constraints may be
severely modified if the value of the gravitational "constant" G varies with
cosmological epoch, a possibility which arises in many scenarios for the early
Universe. The nature of the modification depends upon whether the value of $G$
near a black hole maintains the value it had at its formation epoch
(corresponding to gravitational memory) or whether it tracks the background
cosmological value. This is still uncertain but we discuss various approaches
which might help to resolve the issue.


title: Evidence for TeV gamma ray emission from Cassiopeia A

abstract:
  232 hours of data were accumulated from 1997 to 1999, using the HEGRA
Stereoscopic Cherenkov Telescope System to observe the supernova remnant
Cassiopeia A. TeV gamma ray emission was detected at the 5 sigma level, and a
flux of (5.8 +- 1.2(stat) +- 1.2(syst)) 10^(-9) ph m^(-2) s^(-1) above 1 TeV
was derived. The spectral distribution is consistent with a power law with a
differential spectral index of -2.5 +- 0.4(stat) +- 0.1(syst) between 1 and 10
TeV. As this is the first report of the detection of a TeV gamma ray source on
the "centi-Crab" scale, we present the analysis in some detail. Implications
for the acceleration of cosmic rays depend on the details of the source
modeling. We discuss some important aspects in this paper.


title: When Photoionization Is Not Enough

abstract:
  It is well-known that photoionization is the major mechanism powering nebulae
emission-lines. For about 30 years, numerical simulations using photoionization
codes have been employed to analyze HII regions, planetary nebulae and active
galactic nuclei. Although these models can reproduce most of the observed
features, some remain unexplained. Two possible causes for the discrepancies
between observations and model predictions are discussed in this paper: (a) the
models are not realistic enough; (b) an additional energy source is needed. The
discussion here is mainly based on the results of photoionization models for
the NW knot of I Zw 18.


title: On the estimation of galaxy structural parameters: the Sersic Model

abstract:
  This paper addresses some questions which have arisen from the use of the
S\'ersic r^{1/n} law in modelling the luminosity profiles of early type
galaxies. The first issue deals with the trend between the half-light radius
and the structural parameter n. We show that the correlation between these two
parameters is not only real, but is a natural consequence from the previous
relations found to exist between the model-independent parameters: total
luminosity, effective radius and effective surface brightness. We also define a
new galaxy concentration index which is largely independent of the image
exposure depth, and monotonically related with n. The second question concerns
the curious coincidence between the form of the Fundamental Plane and the
coupling between <I>_e and r_e when modelling a light profile. We explain,
through a mathematical analysis of the S\'ersic law, why the quantity
r_e<I>_e^{0.7} appears almost constant for an individual galaxy, regardless of
the value of n (over a large range) adopted in the fit to the light profile.
Consequently, Fundamental Planes of the form r_e<I>_e^{0.7} propto sigma_0^x
(for any x, and where sigma_0 is the central galaxy velocity dispersion) are
insensitive to galaxy structure. Finally, we address the problematic issue of
the use of model-dependent galaxy light profile parameters versus
model-independent quantities for the half-light radii, mean surface brightness
and total galaxy magnitude. The former implicitly assume that the light profile
model can be extrapolated to infinity, while the latter quantities, in general,
are derived from a signal-to-noise truncated profile. We quantify
(mathematically) how these parameters change as one reduces the outer radius of
an r^{1/n} profile, and reveal how these can vary substantially when n>4.


title: Local Gravitational Instability of Magnetized Shear Flows

abstract:
  The effect of magnetic shear and shear flow on local gravitationally induced
instabilities is investigated. A simple model is constructed allowing for an
arbitrary entropy gradient and a shear plasma flow in the Boussinesq
approximation. A transformation to shearing magnetic coordinates achieves a
model with plasma flow along the magnetic field lines where the coordinate
lines are coincident with the field lines. The solution for the normal modes of
the system depends on two parameters: the Alfven Mach number of the plasma flow
and the entropy gradient. The behavior of the unstable normal modes of this
system is summarized by a stability diagram. Important characteristics of this
stability diagram are the following: magnetic shear is stabilizing and the
entropy gradient must exceed a threshold value for unstable mode growth to
occur; flow acts to suppress mode growth in a substantially unstable regime as
expected, yet near marginal stability it can lessen the stabilizing effect of
magnetic shear and enhance the growth rates of the instability; and, as the
Alfven Mach number approaches one, the instability is completely stabilized.
Analytical work is presented supporting the characteristics of the stability
diagram and illuminating the physical mechanisms controlling the behavior of
the model. The implications of this work for astrophysical and fusion
applications and the potential for future research extending the results to
include compressibility are discussed.


title:
Optical Identification of the X-ray Burster in the Globular Cluster
  NGC1851

abstract:
  We have obtained exposures of the field of X0512-401 in the globular cluster
NGC1851, in X-rays with the Chandra X-ray Observatory, and in the far-UV with
the Hubble Space Telescope. We derive an accurate new X-ray position within ~1"
for X0512-401, which enables us to confirm that the only plausible candidate
for the optical/UV counterpart is the Star A, which we previously identified
from WFPC2 imaging. We find no evidence for X-ray or UV flux modulation on the
ultra-short (<1 hr) expected binary period, which implies a low system
inclination. In addition, we have detected and spatially resolved an X-ray
burst event, confirming the association of the burster, quiescent X-ray source,
and optical object. The very large Lx/Lopt of this object implies an
extraordinarily compact system, similar to the sources in NGC6624 and NGC6712.


title: Mass and Light in the Universe

abstract:
  We present a weak lensing and photometric study of six half by half degree
fields observed at the CFHT using the UH8K CCD mosaic camera. The fields were
observed for a total of 2 hours each in I and V, resulting in catalogs
containing ~ 20 000 galaxies per passband per field. We use V-I color and I
magnitude to select bright early type galaxies at redshifts 0.1 < z < 0.9. We
measure the gravitational shear from faint galaxies in the range 21 < m_I < 25
from a composite catalog and find a strong correlation with that predicted from
the early types if they trace the mass with mass-to-light ratio 300\pm75 h (in
solar units) for a flat (Omega_m0 = 0.3, Omega_l0 = 0.7) lambda cosmology and
400\pm100 h for Einstein-de Sitter. We make two-dimensional reconstructions of
the mass surface density. Cross-correlation of the measured mass surface
density with that predicted from the early type galaxy distribution shows a
strong peak at zero lag (significant at the 5.2-sigma level). We azimuthally
average the cross- and auto-correlation functions. We conclude that the
profiles are consistent with early type galaxies tracing mass on scales of > 45
arcsec (> 200 kpc at z = 0.5). We sub-divide our bright early type galaxies by
redshift and obtain similar conclusions. These mass-to-light ratios imply
\Omega_m0 = 0.10\pm0.02 (\Omega_m0 = 0.13\pm0.03 for Einstein-de Sitter) of
closure density.


title:
A Near-Infrared Stellar Census of Blue Compact Dwarf Galaxies: The
  Wolf-Rayet Galaxy I Zw 36

abstract:
  We report the results of near-IR imaging in J and H, of I Zw 36
($\approx$Z$_{\odot}$/14) with the Hubble Space Telescope. Whereas imaging with
the pre-COSTAR Faint Object Camera (FOC) previously resolved hot and massive
stars in the near-UV, the NICMOS data furnish a census of the cool,
intermediate- and low-mass stars. There clearly was star formation in I Zw 36
prior to the activity which earned it its Blue Compact Dwarf/Wolf-Rayet galaxy
classification. The detection of luminous, asymptotic giant branch stars
requires that stars formed vigorously several hundred Myr ago. The
well-populated red giant branch indicates stars with ages of at least 1-2 Gyr
(and possibly older than 10 Gyr). We use the tip-of-the-red-giant-branch method
to derive a distance of $\geq$5.8 Mpc. This is the third in a series of papers
on near-IR---resolved Blue Compact Dwarf galaxies. We notice that the
color-magnitude diagrams of VII Zw 403, Mrk 178, and I Zw 36 do not exhibit the
gaps expected from an episodic mode of star formation. Using simulated
color-magnitude diagrams we demonstrate for I Zw 36 that star formation did not
stop for more than a few 10$^8$ yrs over the past 10$^9$ yrs, and discuss the
implications of this result.


title: Self-Similar Hot Accretion Flow onto a Neutron Star

abstract:
  We present analytical and numerical solutions which describe a hot, viscous,
two-temperature accretion flow onto a neutron star or any other compact star
with a surface. We assume Coulomb coupling between the protons and electrons,
and free-free cooling from the electrons. Outside a thin boundary layer, where
the accretion flow meets the star, we show that there is an extended settling
region which is well-described by two self-similar solutions: (1) a
two-temperature solution which is valid in an inner zone $r\le10^{2.5}$ ($r$ is
in Schwarzchild units), and (2) a one-temperature solution at larger radii. In
both zones, $\rho\propto r^{-2}, \Omega\propto r^{-3/2}, v\propto r^0,\
T_p\propto r^{-1}$; in the two-temperature zone, $T_e\propto r^{-1/2}$. The
luminosity of the settling zone arises from the rotational energy of the star
as the star is braked by viscosity; hence the luminosity is independent of
$\dot M$. The settling solution is convectively and viscously stable and is
unlikely to have strong winds or outflows. The flow is thermally unstable, but
the instability may be stabilized by thermal conduction. The settling solution
described here is not advection-dominated, and is thus different from the
self-similar ADAF found around black holes. When the spin of the star is small
enough, however, the present solution transforms smoothly to a (settling) ADAF.


title:
Generation of Magnetic Fields and Jitter Radiation in GRBs. I. Kinetic
  Theory

abstract:
  We present a theory of generation of strong (sub-equipartition) magnetic
fields in relativistic collisionless GRB shocks. These fields produced by the
kinetic two-stream instability are tangled on very small spatial scales. This
has a clear signature in the otherwise synchrotron(-self-Compton) $\gamma$-ray
spectrum. Second, we present an analytical theory of jitter radiation, which is
emitted when the correlation length of the magnetic field is smaller then the
gyration (Larmor) radius of the accelerated electrons. We demonstrate that the
spectral power $P(\nu)$ for pure jitter radiation is well-described by a
sharply broken power-law: $P(\nu)\propto\nu^1$ for $\nu<\nu_j$ and
$P(\nu)\propto\nu^{-(p-1)/2}$ for $\nu>\nu_j$, where $p$ is the electron
power-law index and $\nu_j$ is the jitter break, which is independent of the
magnetic field strength and depends on the shock energetics and kinematics.
Here we mostly focus on the first problem. The radiation theory and comparison
with observations will be discussed in the forthcoming publications.


title: Self-Interacting Dark Matter with Flavor Mixing

abstract:
  The crisis of the cold dark matter and problems of the self-interacting dark
matter models is resolved by postulating flavor mixing of dark matter
particles. Flavor-mixed particles segregate in the gravitational field to form
dark halos composed of heavy mass eigenstates. Since these particles are mixed
in the interaction basis, elastic collisions convert some of heavy eigenstates
into light ones which leave dense central regions of the halo. This
annihilation-like process will soften dense central cusps of halos. The
proposed model accumulates most of the attractive features of self-interacting
and annihilating dark matter models, but does not suffer from their severe
drawbacks. This model is natural; it does not require fine tuning.


title:
A Jet Model With a Hard Electron Distribution for the Afterglow of GRB
  000301c

abstract:
  The parameters of the GRB 000301c afterglow are determined within the usual
framework of synchrotron emission from relativistic ejecta, through fits to the
available radio-to-optical data. It is found that 1) the jet energy after the
GRB phase is ~3x10^{50} erg, 2) the initial opening angle of the jet is ~13
deg, 3) the medium that decelerates the afterglow has a density ~25/cm^3, 4)
the power-law distribution of the shock-energized electrons is hard, with an
index around 1.5, and 5) the cooling frequency was located below the optical
domain. Furthermore we find that the collimation of ejecta alone cannot explain
the sharp, large magnitude break observed in the R-band emission of this
afterglow at few days, and that a high energy break in the electron
distribution, corresponding to an electron energy close to equipartition,
together with the lateral spreading of the jet accommodate better this break.
Microlensing by a star in an intervening galaxy produces only a flattening of
the afterglow emission and cannot explain the mild brightening exhibited by the
optical emission of 000301c at ~4 days.


title: The Cosmic Microwave Background

abstract:
  This set of lectures provides an overview of the basic theory and
phenomenology of the cosmic microwave background. Topics include a brief
historical review; the physics of temperature and polarization fluctuations;
acoustic oscillations of the primordial plasma; the space of inflationary
cosmological models; current and potential constraints on these models from the
microwave background; and constraints on inflation.


title: The electron temperature in ionized nebulae

abstract:
  We discuss the role of the electron temperature in abundance determinations
in ionized nebulae (planetary nebulae and giant HII regions). We show that,
even when observations provide a direct estimate of Te, abundance
determinations may sometimes be significantly in error for reasons other than
hypothetical temperature fluctuations or uncertainties in ionization correction
factors, and we show striking examples both in the high and the low metallicity
regimes. On the other hand, even without a direct measure of Te and under
certain conditions, it is possible to give rough estimates (or limits) on the
abundances, both in GHRs and in PNe. Although the main mechanisms determining
the electron temperature in ionized nebulae have been known for half a century,
we emphasize that there are still important problems to be solved. Finally, we
advocate for a different description of temperature inhomogeneities than the
scheme generally used.


title: Absorption and Reddening in the Seyfert Galaxy NGC 3227

abstract:
  We have obtained low-dispersion spectra of NGC 3227 with the Space Telescope
Imaging Spectrograph (STIS) to study the intrinsic UV absorption and the
reddening of the nucleus in this Seyfert 1 galaxy. The UV spectra show a wealth
of absorption lines at the systemic redshift that span a wide range in
ionization state (Mg I to N V). The equivalent widths of the lines are
consistent with our earlier prediction that a ``lukewarm absorber'' (T= 18,000
K at the ionized face) with a substantial column of gas [N(H) = 2 x 10^21
cm^-2] is present and likely responsible for the reddening of the nucleus. The
lukewarm absorber is also responsible for most of the absorption in the X-rays
at energies less than 1 keV, although a more highly ionized ``warm absorber''
is needed to account for the O VII and O VIII ionization edges. In addition, we
require a small column [N(H) = 5 x 10^19 cm^-2] of cold gas to match the
strengths of the neutral and singly-ionized lines in the UV spectra. NGC 3227
is the first Seyfert galaxy in which a strong link between the reddening and
intrinsic UV absorption has been found. By comparing our STIS UV and optical
spectra with those of the unreddened Seyfert NGC 4151, we have determined a
reddening curve for the nuclear continuum source in NGC 3227 over the 1150 -
10,200 A range. The reddening curve does not show a 2200 AA bump, and is
steeper in the UV than reddening curves derived for the Galaxy, LMC, and SMC,
suggesting a preponderence of small dust grains near the nucleus.


title:
The radial velocities of the RS CVn star UX Ari. A triple system with a
  binary on the same line of sight

abstract:
  UX Ari belongs to the class of very active RS CVn stars and has recently been
the target of surface (Doppler) imaging. Although this technique needs a quite
accurate determination of the orbit (in order to have the correct period for
phasing and the correct Doppler shift correction of the line profiles) we found
only one, quite old orbit solution, which has subsequently been used by
everyone.
  We used published radial velocities (RVs), supplemented by a large number
(124) of our own recent, high-accuracy RVs of both the primary (K0 IV) and the
secondary (G5 V) to improve the orbit of UX Ari. In addition to the improved
set of parameters, we found that the gamma velocity of the system is
systematically changing over time. It seems that UX Ari is a triple system.
Actually, a third star is weakly present in the spectrum. While its RV is also
changing, it is not a member of the system, but happens to be on the same line
of sight.
  Finally, conclusions about the physical parameters of the objects from the
orbits are presented.


title:
Gaussianity of Degree-Scale Cosmic Microwave Background Anisotropy
  Observations

abstract:
  We present results from a first test of the Gaussianity of degree-scale
cosmic microwave background (CMB) anisotropy. We investigate Gaussianity of the
CMB anisotropy by studying the topology of CMB anisotropy maps from the QMAP
and Saskatoon experiments. We also study the QMASK map, a combination map of
the QMAP and Saskatoon data. We measure the genus from noise-suppressed
Wiener-filtered maps at an angular scale of about 1.5 degrees. To test the
Gaussianity of the observed anisotropy, we compare these results to those
derived from a collection of simulated maps for each experiment in a Gaussian
spatially-flat cosmological constant dominated cold dark matter model. The
genus-threshold level relations of the QMAP and Saskatoon maps are consistent
with Gaussianity. While the combination QMASK map has a mildly non-Gaussian
genus curve which is not a consequence of known foreground contamination, this
result is not statistically significant at the 2 sigma level. These results
extend previous upper limits on the non-Gaussianity of the large angular scale
(> 10 degrees) CMB anisotropy (measured by the COBE DMR experiment) down to
degree angular scales.


title:
Submillimeter mapping and analysis of cold dust condensations in the
  Orion M42 star forming complex

abstract:
  We present here the continuum submillimeter maps of the molecular cloud
around the M42 Nebula in the Orion region. These have been obtained in four
wavelength bands (200, 260, 360 and 580 microns) with the ProNaOS two meter
balloon-borne telescope. The area covered is 7 parsecs wide (50 arcmin at a
distance of 470 pc) with a spatial resolution of about 0.4 parsec. Thanks to
the high sensitivity to faint surface brightness gradients, we have found
several cold condensations with temperatures ranging from 12 to 17 K, within 3
parsecs of the dense ridge. The statistical analysis of the temperature and
spectral index spatial distribution shows an evidence of an inverse correlation
between these two parameters. Being invisible in the IRAS 100 micron survey,
some cold clouds are likely to be the seeds for future star formation activity
going on in the complex. We estimate their masses and we show that two of them
have masses higher than their Jeans masses, and may be gravitationally
unstable.


title: Reconsidering the Identification of M101 Hypernova Remnant Candidates

abstract:
  Using a deep Chandra AO-1 observation of the face-on spiral galaxy M101, we
examine three of five previously optically-identified X-ray sources which are
spatially correlated with optical supernova remnants (MF54, MF57, and MF83).
The X-ray fluxes from these objects, if due to diffuse emission from the
remnants, are bright enough to require a new class of objects, with the
possible attribution by Wang to diffuse emission from hypernova remnants. Of
the three, MF83 was considered the most likely candidate for such an object due
to its size, nature, and close positional coincidence. However, we find that
MF83 is clearly ruled out as a hypernova remnant by both its temporal
variability and spectrum. The bright X-ray sources previously associated with
MF54 and MF57 are seen by Chandra to be clearly offset from the optical
positions of the supernova remnants by several arc seconds, confirming a result
suggested by the previous work. MF54 does have a faint X-ray counterpart,
however, with a luminosity and temperature consistent with a normal supernova
remnant of its size. The most likely classifications of the sources are as
X-ray binaries. Although counting statistics are limited, over the 0.3--5.0 keV
spectral band the data are well fit by simple absorbed power laws with
luminosities in the 10^38 to 10^39 ergs/s range. The power law indices are
softer than those of Milky Way LMXB of similar luminosities, and are more
consistent with those of the Large Magellanic Cloud. Both the high luminosity
and the soft spectral shape favor these being accreting black hole binaries in
high soft states.


title: A speckle interferometry survey of lambda Bootis stars

abstract:
  A search for duplicity of lambda Bootis stars has been made by using the
speckle camera installed at the Telescopio Nazionale Galileo. The operation
mode and the reduction procedure allow one to obtain not only the separation,
but also the magnitude difference between the components; the latter parameter
is fundamental for determining the degree of contamination from the secondary
component of a binary system and thus the importance of the veiling effect that
produces absorption lines weaker than normal. Two stars, HD 38545 and HD
290492, are close binaries with values of the separation and of the magnitude
difference such that only a composite spectrum can be observed. For another 15
lambda Bootis candidates, observed with negative results, the upper limits of a
possible companion separation are given.


title:
Broad Absorption Line Quasars in the Sloan Digital Sky Survey with
  VLA-FIRST Radio Detections

abstract:
  We present 13 Broad Absorption Line (BAL) quasars, including 12 new objects,
which were identified in the Sloan Digital Sky Survey (SDSS) and matched within
2'' to sources in the FIRST radio survey catalog. The surface density of this
sample of radio-detected BAL quasars is 4.5 +- 1.2 per 100 deg^2, i.e.
approximately 4 times larger than previously found by the shallower FIRST
Bright Quasar Survey (FBQS). A majority of these radio-detected BAL quasars are
moderately radio-loud objects. The fraction of BAL quasars in the entire radio
quasar sample, 4.8 +- 1.3 %, is comparable to the fraction of BAL quasars among
the SDSS optical quasar sample (ignoring selection effects). We estimate that
the true fraction of BAL quasars (mostly HiBALs) in the radio sample is 9.2 +-
2.6 % once selection effects are accounted for. We caution that the absorption
troughs of 4 of the 13 radio-detected quasars considered do not strictly
satisfy the standard BALnicity criterion. One or possibly two of the new
radio-detected BAL quasars are of the rare ``iron LoBAL'' type. BAL quasars are
generally redder than the median SDSS quasar at the same redshift.


title:
The Chandra Deep Survey of the Hubble Deep Field North Area. IV. An
  Ultradeep Image of the HDF-N

abstract:
  We present results from a 479.7 ks Chandra exposure of the Hubble Deep Field
North (HDF-N) and its immediate vicinity. In our X-ray image, the deepest ever
reported with a 0.5-2.0 keV flux limit of about 4.9 x 10^{-17} erg/cm^2/s, we
detect four new HDF-N X-ray sources bringing the total number of such sources
to 12. The new sources include two optically bright (R=18.3-18.8), low-redshift
(z<0.15) galaxies, a Fanaroff-Riley I radio galaxy, and an edge-on spiral
hosting either a powerful starburst or a low-luminosity active galactic nucleus
(AGN). Notably, we have now detected X-ray emission from all luminous galaxies
(M_V<-18) with z<0.15 known in the HDF-N. We have also detected the remarkable
microJy radio source VLA J123642.09+621331.4, which is located just outside the
HDF-N and has a likely redshift of z=4.424. We have detected X-ray variability
from two of the previously known HDF-N X-ray sources, and spectral fitting
shows clear evidence for X-ray absorption in the brightest X-ray source in the
HDF-N, a z=0.960 broad-line AGN with associated Mg II absorption. Stacking
analyses of optically bright HDF-N galaxies not individually detected in X-rays
have provided estimates of their average X-ray fluxes, and we find that the
X-ray luminosities of `normal' spirals at z~0.5 are not more than a factor of
\~2 larger (per unit B-band luminosity) than those of spirals in the local
Universe (z<0.01). This constrains models for the evolution of low-mass X-ray
binary populations in galaxies in response to the declining cosmic
star-formation rate. Monte-Carlo simulations support the validity of the
stacking analyses and show that the Chandra Advanced CCD Imaging Spectrometer
(ACIS) performs source detection well even with effective exposure times of ~8
Ms. (Abridged)


title: Constraints on the nuclear emission from the Circinus galaxy: the torus

abstract:
  In the context of the unified model of Seyfert galaxies, we use observations
from the literature and a radiative transfer model to investigate the near-IR
to mm emission produced by the presumed torus in the Circinus galaxy, from
2microns to 1.3mm. From the infrared SED modelling, we find that the total
luminosity (L_{IR}) in this wavelength range, consists of similar contributions
from the torus and starburst with a ratio of nuclear luminosity to starburst
luminosity (L_{NUC}/L_{SB}) approx. 0.8.
  By using a similar torus model to that of NGC1068, but without the conical
dust, we find an upper limit to the outer torus radius of approx. 12pc with a
best fit of approx. 2pc. The upper limit torus size estimated from the
radiative transfer modelling is consistent with the 16pc torus radius estimated
from near-IR imaging polarimetry of Circinus.


title: A Survey of the Host Galaxies of Gamma-Ray Bursts

abstract:
  We used 45 orbits of Hubble Space Telescope time in Cycle 9 to obtain deep
STIS/CCD images of the host galaxies of eleven gamma-ray bursts. Our goals are
to study the morphologies of the host galaxies, to obtain precise locations of
gamma-ray bursts within their host galaxies, and to determine star-formation
rates in the hosts. We present preliminary results for GRB 980425/SN1998bw, GRB
980613, and GRB 9809703.


title: A Variety of Decays of Gamma-Ray Burst Pulses

abstract:
  We find and study a variety of the spectral-temporal behavior during the
decay phase of the light curve of long and bright pulse structures in gamma-ray
bursts. It was earlier found that for about half of these decays, the
instantaneous photon flux is consistent with a power law in time, where the
photon flux $\propto$ 1/time. This decay behavior is a consequence of the
validity of both a power law hardness-intensity correlation (HIC) and an
exponential hardness-fluence correlation (HFC). Beside this behavior, we find
that the other cases approximately behave as 1/(time)$^3$. For a few of these
latter decays, the two correlations (HIC and HFC) are constrained and found to
be consistent with the light curve behavior. For these cases, the HIC is still
a power law while the HFC is described by a generalized function. We study and
describe these behaviors analytically and examine actual burst data from the
complete catalog of the BATSE on the CGRO.


title:
Acceleration and collimation of relativistic plasmas ejected by fast
  rotators

abstract:
  A stationary self-consistent outflow of a magnetised relativistic plasma from
a rotating object with an initially monopole-like magnetic field is
investigated in the ideal MHD approximation under the condition $\sigma/U_0^2
>1$, where $\sigma$ is the ratio of the Poynting flux over the mass energy flux
at the equator and the surface of the star, with $U_0=\gamma_0v_0/c$ and
$\gamma_0$ the initial four-velocity and Lorentz factor of the plasma. The
mechanism of the magnetocentrifugal acceleration and self-collimation of the
relativistic plasma is investigated. A jet-like relativistic flow along the
axis of rotation is found in the steady-state solution under the condition
$\sigma/U_0^2 >1$ with properties predicted analytically. The amount of the
collimated matter in the jet is rather small in comparison to the total mass
flux in the wind. An explanation for the weak self-collimation of relativistic
winds is given.


title: Evolution of spiral shocks in U Gem during outburst

abstract:
  Time resolved spectroscopic observations of U Gem during its March 2000
outburst show strong spiral shocks in the accretion disk. During the plateau at
maximum brightness the spiral shocks contribute 14% to the total He II flux.
The two arms of the spiral show a distinctly different evolution during the
outburst and decline, which indicates an asymmetric evolution in the disk.


title: The ages and colours of cool helium-core white dwarf stars

abstract:
  The purpose of this work is to explore the evolution of helium-core white
dwarf stars in a self-consistent way with the predictions of detailed non-gray
model atmospheres and element diffusion. To this end, we consider helium-core
white dwarf models with stellar masses of 0.406, 0.360, 0.327, 0.292, 0.242,
0.196 and 0.169 solar masses and follow their evolution from the end of mass
loss episodes during their pre-white dwarf evolution down to very low surface
luminosities. We find that when the effective temperature decreases below
4000K, the emergent spectrum of these stars becomes bluer within time-scales of
astrophysical interest. In particular, we analyse the evolution of our models
in the colour-colour and colour-magnitude diagrams and we find that helium-core
white dwarfs with masses ranging from approx. 0.18 to 0.3 solar masses can
reach the turn-off in their colours and become blue again within cooling times
much less than 15 Gyr and then remain brighter than M_V approx. 16.5. In view
of these results, many low-mass helium white dwarfs could have had time enough
to evolve to the domain of collision-induced absorption from molecular
hydrogen, showing blue colours.