title:
Optical variability of the BL Lacertae object GC 0109+224. Multiband
  behaviour and time scales from a 7-years monitoring campaign

abstract:
  We present the most continuous data base of optical $BVR_{c}I_{c}$
observations ever published on the BL Lacertae object GC 0109+224, collected
mainly by the robotic telescope of the Perugia University Observatory in the
period November 1994-February 2002. These observations have been complemented
by data from the Torino Observatory, collected in the period July 1995-January
1999, and Mt. Maidanak Observatory (December 2000). GC 0109+224 showed rapid
optical variations and six major outbursts were observed at the beginning and
end of 1996, in fall 1998, at the beginning and at the end of 2000, and at the
beginning of 2002. Fast and large-amplitude drops characterized its flux
behaviour. The $R_c$ magnitude ranged from 13.3 (16.16 mJy) to 16.46 (0.8 mJy),
with a mean value of 14.9 (3.38 mJy). In the periods where we collected
multi-filter observations, we analyzed colour and spectral indexes, and the
variability patterns during some flares. The long-term behaviour seems
approximatively achromatic, but during some isolated outbursts we found
evidence of the typical loop-like hysteresis behaviour, suggesting that rapid
optical variability is dominated by non-thermal cooling of a single emitting
particle population. We performed also a statistical analysis of the data,
through the discrete correlation function (DCF), the structure function (SF),
and the Lomb-Scargle periodogram, to identify characteristic times scales, from
days to months, in the light curves, and to quantify the mode of variability.
We also include the reconstruction of the historical light curve and a
photometric calibration of comparison stars, to favour further extensive
optical monitoring of this interesting blazar.


title: A Polarization Survey of SiO Maser Variability in Evolved Stars

abstract:
  We have monitored the SiO (v = 1, J = 2 -> 1) maser polarization in 17
variable stars (Miras, OH-IR stars, and supergiants) to investigate the
long-term persistence of masers. The 8 epochs of observations span 2.5 years,
thereby sampling multiple cycles for these stars with typical periods of ~1
year. The average polarization was 23% with a typical dispersion of 7%,
although the variability differed substantially from star to star. In the
Stokes q and u spectra of individual stars, a few strong maser features tended
to dominate the polarization, with the maser features persisting for less than
one stellar cycle for some stars, and for multiple cycles for a few stars.
Because individual masers are not resolved in our beam-averaged total intensity
spectra, we correlated the polarization spectra between epochs to measure the
characteristic lifetimes of the features rather than attempting to trace the
evolution of separate line components. We found that individual maser feature
lifetimes ranged from a few months or less to >2 years. These data indicate
that for the sample of stars as a whole, the masers are not reset at a
particular stellar phase.


title: Recent discoveries of energetic young radio pulsars

abstract:
  The observed population of young radio pulsars has grown substantially in
recent years due to a combination of large-scale surveys and deep targeted
searches. Many of the pulsars are associated with supernova remnants and/or
unidentified gamma-ray sources. This review summarises the state of play and
looks ahead to likely advances in the near future.


title: Stroboscopic optical observations of the Crab pulsar

abstract:
  Photometric data of the Crab pulsar, obtained in stroboscopic mode over a
period of more than eight years, are presented here. The applied Fourier
analysis reveals a faint 60 second modulation of the pulsar's signal, which we
interpret as a free precession of the pulsar.


title: Distant globular clusters with anomalously small masses

abstract:
  We found that 10 metal-poor globular clusters are greately distinguished for
anomalously small masses on the "destruction rate--mass" plain. As it turned
out, these poor clusters, situated 15 kpc farther from the Galactic centre, are
somewhat younger than the bulk of the metal-poor globulars, and have
anomalously red horizontal branches. All these clusters are supposed to belong
to the "young halo" subsystem, i.e. they are supposed to have been captured by
the Galaxy at different stages of their evolution. We discovered a significant
correlation between the ages found from isochrones and masses of globulars
which lie at galactocentric distances greater than the radius of the solar
orbit. At the same time, deficiency of distant massive clusters is noticeable
with increasing distance from the galactic centre. So we see unticorrelation
between the galactocentric distance and masses of distant clusters. Both
relations are negligible for the inner clusters of the Galaxy. We assume that
favourable conditions for violent dissipation with considerable loss of mass
are realised inside the protoglobulars which formed far from the Galactic
centre.


title: Particle Energization in an Expanding Magnetized Relativistic Plasma

abstract:
  Using a 2-1/2-dimensional particle-in-cell (PIC) code to simulate the
relativistic expansion of a magnetized collisionless plasma into a vacuum, we
report a new mechanism in which the magnetic energy is efficiently converted
into the directed kinetic energy of a small fraction of surface particles. We
study this mechanism for both electron-positron and electron-ion (mi/me=100, me
is the electron rest mass) plasmas. For the electron-positron case the pairs
can be accelerated to ultra-relativistic energies. For electron-ion plasmas
most of the energy gain goes to the ions.


title: Lx-SFR relation in star forming galaxies

abstract:
  We compare the results of Grimm et al. (2003) and Ranalli et al. (2003) on
the Lx-SFR relation in normal galaxies. Based on the Lx-stellar mass dependence
for LMXBs, we show, that low SFR (SFR<1 Msun/year) galaxies in the Ranalli et
al. sample are contaminated by the X-ray emission from low mass X-ray binaries,
unrelated to the current star formation activity.
  The most important conclusion from our comparison is, however, that after the
data are corrected for the ``LMXB contamination'', the two datasets become
consistent with each other, despite of their different content, variability
effects, difference in the adopted source distances, X-ray flux and star
formation rate determination and in the cosmological parameters used in
interpreting the HDF-N data. They also agree well, both in the low and high SFR
regimes, with the predicted Lx-SFR dependence derived from the parameters of
the ``universal'' HMXB luminosity function. This encouraging result emphasizes
the potential of the X-ray luminosity as an independent star formation rate
indicator for normal galaxies.


title: Gigahertz-Peaked Spectrum Radio Sources

abstract:
  The study of compact active galactic nuclei (AGN) that possess convex radio
spectra (the gigahertz-peaked spectrum radio sources) offers a unique
opportunity to probe both the early evolutionary stages of relativistic AGN
jets and their immediate nuclear environments. In this article I trace Ken
Kellermann's early investigations of these sources, which played a major role
in justifying the development of modern-day VLBI techniques. I describe how our
understanding of these AGN has progressed since Kellermann's early discoveries,
and discuss several ways in which the current classification scheme can be
simplified to reflect intrinsic source characteristics, rather than
observer-biased quantities. Finally, I discuss recent results from the VLBA 2
cm survey concerning the relativistic jet kinematics of the two-sided
peaked-spectrum sources 4C +12.50 (PKS 1345+125) and OQ 208 (1404+286).


title: The Speed and Orientation of the Parsec-Scale Jet in 3C 279

abstract:
  We have calculated inverse-Compton Doppler factors for 3C 279 using the
collection of VLBI data recently published by us, and the collection of
multiwavelength spectra recently published by Hartman et al. From the Doppler
factor and superluminal apparent speed, we then calculate the Lorentz factor
and angle to the line-of-sight of the parsec-scale relativistic jet. We model
the jet components as homogeneous spheres and the VLBI core as an unresolved
inhomogeneous conical jet. The conical-jet model can be made to match both the
observed X-ray emission and the VLBI properties of the core with a suitable
choice of Doppler factor, implying the core makes a significant contribution to
the X-ray emission. The parameters of the conical models indicate the jet is
particle dominated at the radii that produce significant emission, and is not
in equipartition. At the inner radius of the conical jet the magnetic field is
of order 0.1 G and the relativistic-particle number density is of order 10
cm^{-3}. When all components are included in the calculation, then on average
the core produces about half of the X-rays, with the other half being split
between the long-lived component C4 and the brightest inner-jet component. We
calculate an average speed and angle to the line-of-sight for the region of the
jet interior to 1 mas of v=0.992c (gamma=8) and 4 degrees, and an average speed
and angle to the line-of-sight for C4 (at a distance from the core of 3 mas) of
v=0.997c (gamma=13) and 2 degrees. These values imply average Doppler factors
of delta=12 for the inner jet, and delta=21 for C4.


title: Physics of SNeIa and Cosmology

abstract:
  We give an overview of the current understanding of Type Ia supernovae
relevant for their use as cosmological distance indicators. We present the
physical basis to understand their homogeneity of the observed light curves and
spectra and the observed correlations. This provides a robust method to
determine the Hubble constant, 67 +- 8 (2 sigma) km/Mpc/sec, independently from
primary distance indicators.
  We discuss the uncertainties and tests which include SNe Ia based distance
determinations prior to delta-Ceph. measurements for the host galaxies. Based
on detailed models, we study the small variations from homogeneities and their
observable consequences. In combination with future data, this underlines the
suitability and promises the refinements needed to determine accurate relative
distances within 2 to 3 % and to use SNe Ia for high precision cosmology.


title: The Circumstellar Disk of the Butterfly Star in Taurus

abstract:
  We present a model of the circumstellar environment of the so-called
``Butterfly Star'' in Taurus (IRAS 04302+2247). The appearance of this young
stellar object is dominated by a large circumstellar disk seen edge-on and the
light scattering lobes above the disk. The model is based on multi-wavelength
continuum observations: Millimeter maps and high-resolution near-infrared
images obtained with HST/NICMOS.
  It was found that the disk and envelope parameters are comparable with those
of the circumstellar environment of other young stellar objects. A main result
is that the dust properties must be different in the circumstellar disk and in
the envelope: While a grain size distribution with grain radii up to 100 micron
is required to reproduce the millimeter observations of the disk, the envelope
is dominated by smaller grains similar to those of the interstellar medium.
  Preprint with high figure quality available at:
http://spider.ipac.caltech.edu/staff/swolf/homepage/public/preprints/i04302.ps


title:
Cuts and penalties: comment on "The clustering of ultra-high energy
  cosmic rays and their sources"

abstract:
  In a series of papers we have found statistically significant correlations
between arrival directions of ultra-high energy cosmic rays and BL Lacertae
objects. Recently, our calculations were partly repeated by Evans, Ferrer and
Sarkar with different conclusions. We demonstrate that the criticism of Evans,
Ferrer and Sarkar is incorrect. We also present the details of our method.


title: High-redshift clusters from NVSS: The TexOx Cluster (TOC) Survey

abstract:
  The TexOx Cluster (TOC) Survey uses overdensities of radiosources in the NVSS
to trace clusters of galaxies. The links between radiosources and rich
environments make this a powerful way to find clusters which may potentially be
overlooked by other selection techniques. By including constraints from optical
surveys, TOC is an extremely efficient way to find clusters at high redshift.
One such field, TOC J0233.3+3021, contains at least one galaxy cluster (at z ~
1.4) and has been detected using the Sunyaev-Zel'dovich (SZ) effect. Even in
targetted deep optical observations, however, distinguishing the cluster
galaxies from the background is difficult, especially given the tendency of TOC
to select fields containing multiple structures at different redshifts.


title:
Galaxy Formation in Triaxial Halos: Black Hole-Bulge-Dark Halo
  Correlation

abstract:
  The masses of supermassive black holes (SBHs) show correlations with bulge
properties in disk and elliptical galaxies. We study the formation of galactic
structure within flat-core triaxial haloes and show that these correlations can
be understood within the framework of a baryonic component modifying the
orbital structure in the underlying potential. In particular, we find that
terminal properties of bulges and their central SBHs are constrained by the
destruction of box orbits in the harmonic cores of dark haloes and the
emergence of progressively less eccentric loop orbits there. SBH masses, M_SBH,
should exhibit a tighter correlation with bulge velocity dispersions, sigma_B,
than with bulge masses, M_B, in accord with observations, if there is a
significant scatter in the M_H-sigma_H relation for the halo. In the context of
this model the observed M_SBH-sigma_B relation implies that haloes should
exhibit a Faber-Jackson type relationship between their masses and velocity
dispersions. The most important prediction of our model is that halo properties
determine the bulge and SBH parameters. The model also has important
implications for galactic morphology and the process of disk formation.


title:
The ESO-Sculptor Survey: Luminosity functions of galaxies per spectral
  type at redshifts 0.1-0.5

abstract:
  [ABRIDGED] We present the first statistical analysis of the complete
ESO-Sculptor redshift survey (ESS). The flux-calibrated sample of 617 galaxy
spectra with R_c<20.5 is separated into 3 spectral classes (early,
intermediate, and late). We report in detail on the spectral classification,
the polynomial K-corrections, and all sources of corresponding random and
systematic errors. The derived luminosity functions (LF) in the Johnson-Cousins
B and Rc bands are in agreement with the results from the comparable CNOC2
survey (Lin et al. 1999), whereas the ESS provides the first estimates of LFs
per spectral type in the Johnson V band. A renewed interpretation of the galaxy
LFs from a redshift survey are obtained by fitting the ESS LFs with composite
functions based on the local LFs per morphological type (Sandage, Binggeli &
Tammann 1985; Jerjen & Tammann 1997). As good or better fits than with pure
Schechter functions are obtained using: for the early-type LF, a two-wing
Gaussian; for the intermediate-type LF, the sum of a Gaussian modeling the
Spiral galaxies and a steep Schechter function (alpha=-1.5) representing the
dwarf elliptical galaxies; for the late-type LF, a similar composite function
with a flat or weaker slope (-0.8<alpha<-0.3) for the Schechter component which
represents the dwarf Irregular galaxies. This analysis illustrates how LFs per
spectral type may be affected by morphological type mixing, and emphasizes the
need for a quantitative morphological classification at z>0.1 which separates
the giant and dwarf galaxy populations.


title:
External Shock Model for the Prompt Phase of Gamma Ray Bursts:
  Implications for GRB Source Models

abstract:
  An external shock model for the prompt gamma-ray luminous phase of gamma-ray
bursts (GRBs) is treated both analytically and numerically. A widely cited
derivation claiming that an external shock model for rapidly variable GRBs must
be very inefficient employs an incorrect expression for the angular timescale.
Numerical results show that variable GRBs can be formed with >10% efficiency to
transform the directed kinetic energy of the relativistic fireball to
gamma-rays. Successes of the external shock model and difficulties with an
internal wind/colliding shell model are summarized. An impulsive external shock
model is consistent with the supranova model.


title: Halo Concentration and the Dark Matter Power Spectrum

abstract:
  We explore the connection between halo concentration and the dark matter
power spectrum using the halo model. We fit halo model parameters to non-linear
power spectra over a large range of cosmological models. We find that the
non-linear evolution of the power spectrum generically prefers the
concentration at non-linear mass scale to decrease with the effective slope of
the linear power spectrum, in agreement with the direct analysis of the halo
structure in different cosmological models. Using these analyses, we compute
the predictions for non-linear power spectrum beyond the current resolution of
N-body simulations. We find that the halo model predictions are generically
below the analytical non-linear models, suggesting that the latter may
overestimate the amount of power on small scales.


title:
The Cosmic Gamma-Ray Bursts and Their Host Galaxies in a Cosmological
  Context

abstract:
  Studies of the cosmic gamma-ray bursts (GRBs) and their host galaxies are now
starting to provide interesting or even unique new insights in observational
cosmology. Observed GRB host galaxies have a median magnitude R ~ 25 mag, and
show a range of luminosities, morphologies, and star formation rates, with a
median redshift z ~ 1. They represent a new way of identifying a population of
star-forming galaxies at cosmological redshifts, which is mostly independent of
the traditional selection methods. They seem to be broadly similar to the
normal field galaxy populations at comparable redshifts and magnitudes, and
indicate at most a mild luminosity evolution over the redshift range they
probe. Studies of GRB optical afterglows seen in absorption provide a powerful
new probe of the ISM in dense, central regions of their host galaxies, which is
complementary to the traditional studies using QSO absorption line systems.
Some GRB hosts are heavily obscured, and provide a new way to select a
population of cosmological sub-mm sources. A census of detected optical
tranistents may provide an important new way to constrain the total obscured
fraction of star formation over the history of the universe. Finally, detection
of GRB afterglows at high redshifts (z > 6) may provide a unique way to probe
the primordial star formation, massive IMF, early IGM, and chemical enrichment
at the end of the cosmic reionization era.


title:
Clues on the Evolution of Cluster Galaxies From The Analysis of Their
  Orbital Anisotropies

abstract:
  We study the evolution of galaxies in clusters by the analysis of a sample of
about 3000 galaxies, members of 59 clusters from the ESO Nearby Abell Cluster
Survey (ENACS). We distinguish four cluster galaxy populations, based on their
radial and velocity distributions within the clusters. Using the class of
ellipticals and S0's (excluding the very bright ellipticals), we determine the
average cluster mass profile, that we compare with mass models available from
numerical simulations. We then use this cluster mass profile to solve for the
anisotropy profiles of the three other cluster galaxy populations, viz. the
very bright ellipticals, the early spirals, and the late spirals with the
emission-line galaxies. We discuss the implications of our findings for the
evolution of cluster galaxies.


title:
QPO frequencies and mass-outflow rates in black hole powered galactic
  microquasars

abstract:
  For all available pseudo-Schwarzschild potentials, we provide a
non-self-similar model of coupled accretion-outflow system in connection to the
Quasi Periodic Oscillation (QPO) of the black hole powered galactic
microquasars and the emergence of barionic jets out of these objects. We use
the vertically integrated 1.5 dimensional model to describe the disc structure
where the equations of motion are written on the equatorial plane of the
central accretor, assuming the flow to be in hydrostatic equilibrium in the
transverse direction. First we formulate and solve the equations governing
axisymmetrically rotating, advective, multi-transonic black hole accretion
which may contain the Rankine Hugoniot Shock Waves (RHSW), and then we
calculate the associated QPO frequencies ${\nu}_{QPO}$ in terms of relevant
accretion parameters. We then argue that the post-shock region for such flows
may serve as an efficient source of outflow generation; and we calculate, for
{\it same} set of accretion parameters used to calculate the ${\nu}_{QPO}$s,
what fraction of the accreting material, denoted by $R_{\dot m}$, is being
blown as shock generated outflow. In this way we theoretically study the
relation between ${\nu}_{QPO}$s and $R_{\dot m}$s for galactic microquasars and
compare our theoretically obtained result with observational data.


title: The afterglow of GRB021211: Another case of reverse shock emission

abstract:
  GRB021211 was first detected by HETE II and its early afterglow has been
observed. There is a break in its afterglow light curve at about 12 minutes
after the bursts, before the break the optical flux decays with a power-law
index of about -1.6, while at late time the power-law slope is about -1
(Chornock et al. 2002). Here we will show that the afterglow light curve of
GRB021211 can be explained within the framework of the standard fireball model.
We show that the afterglow emission before the break time is the contribution
of the emission from both the reverse shock and the forward shock, while the
afterglow emission after the break time is mainly due to the forward shock
emission. From the fitting we can give constraints on the parameters: the
initial Lorentz factor $250\leq \gamma_0 \leq 900$, the surrounding medium
density $n\geq 1.6\times 10^{-3}$ atoms ${\rm cm^{-3}}$, and
$0.077\epsilon_{\rm B}^{3/16} \leq \epsilon_{\rm B}^{1/4}(\frac{\epsilon_{\rm
e}}{0.1}) \leq 0.14$, where $\epsilon_{\rm B}$ and $\epsilon_{\rm e}$ are the
fractions of the shock energy given to the magnetic field and electrons. We
propose that since the values of $\epsilon_{\rm B}$ and $\epsilon_{\rm e}$ are
somewhat smaller for GRB021211, so the peak energy of the reverse shock
emission is well below the optical band, and thus it is substantially fainter
than 990123 at similar epochs. Also we suggest that such a break might be a
common feature in early optical afterglows.


title: On the Progenitor of Supernova 2001du in NGC 1365

abstract:
  Hubble Space Telescope (HST) WFPC2 archival images obtained years prior to
the explosion of the Type II-plateau supernova (SN) 2001du in NGC 1365
previously have been analyzed to isolate the progenitor star. The SN site was
located using precise astrometry applied to the HST images, with significant
uncertainty, leaving three possible progenitor candidates. Images of the fading
SN have recently become publicly available in the HST archive, allowing us to
pinpoint the SN's exact location on the pre-explosion images. We show that the
SN occurred in very close proximity to one of the blue candidate stars, but we
argue that this star is not the actual progenitor. Instead, the progenitor was
not detected on the pre-SN images, and we constrain the progenitor's mass to be
less than 13 (+7, -4) Msuns. This is consistent with previous constraints on
the progenitor masses of other Type II-plateau supernovae (SNe), suggesting
that such SNe arise from the iron core collapse of massive stars at the lower
extreme of the possible mass range.


title:
Grazing Eclipsing Dwarf Nova CW Monocerotis: Dwarf Nova-Type Outburst in
  a Possible Intermediate Polar?

abstract:
  We observed the 2002 October-November outburst of the dwarf nova CW Mon. The
outburst showed a clear signature of a premaximum halt, and a more rapid
decline after reaching the outburst maximum. On two separate occasions, during
the premaximum stage and near the outburst maximum, shallow eclipses were
recorded. This finding confirms the previously suggested possibility of the
grazing eclipsing nature of this system. The separate occurrence of the
eclipses and the premaximum halt can be understood as a result of a combination
of two-step ignition of an outburst and the inside-out propagation of the
heating wave. We detected a coherent short-period (0.02549 d) signal on two
subsequent nights around the optical maximum. This signal was likely present
during the maximum phase of the 2000 January outburst. We interpret this signal
as a signature of the intermediate polar (IP) type pulses. The rather strange
outburst properties, strong and hard X-ray emission, and the low luminosity of
the outburst maximum might be understood as consequences of the supposed IP
nature. The ratio between the suggested spin period and the orbital period,
however, is rather unusual for a system having an orbital period of ~0.176 d.


title: The magnetisation of protoplanetary disks

abstract:
  The remanent magnetisation of meteorite material in the solar system
indicates that magnetic fields of several Gauss are present in the
protoplanetary disk. It is shown that such relativelystrong magnetic fields can
be generated in dusty protoplanetary disks by relative shear motions of the
charged dust and the neutral gas components. Self-consistent multi-fluid
simulations show that for typical plasma parameters shear flows with
collisional momentum transfer between the different components of the dusty
plasma result in a very efficient generation of magnetic fields with strengths
of about 0.1-1 Gauss on spatial scales of two astronomical units in about one
year. Based on the simulations one may predict that future measurements will
reveal the strong magnetisation of circumstellar disks around young stellar
objects.


title: Yet MORE PM Survey Discoveries....?

abstract:
  The Parkes Multibeam (PM) survey has found nearly 50% of the >1400 known
pulsars and detected 20% of the pulsars in binary systems (75% within the
survey area), few of these are millisecond pulsars with orbits of less than one
day. It is known that the normal search techniques used in the PM Survey have
selected against finding binary pulsars, due to the long integration times
used. The relative performance of the search techniques used and the
improvements made prior to the complete reprocessing of the data currently
being undertaken are discussed. The processing is being done on COBRA - the new
supercomputer at Jodrell Bank. The results of the reprocessing, as well as
adding more solitary pulsars, will give more confidence on the population and
types of binaries in the Galactic plane. However, it can be shown that for
millisecond pulsars in binary orbits of between 20min and a few hours, the
search techniques are still relatively insensitive.


title:
A dual output polarimeter devoted to the study of the Cosmic Microwave
  Background

abstract:
  We have developed a correlation radiometer at 33 GHz devoted to the search
for residual polarization of the Cosmic Microwave Background (CMB). The two
instruments`s outputs are linear combination of two Stokes Parameters (Q and U
or U and V). The instrument is therefore directly sensitive to the polarized
component of the radiation (respectively linear and circular). The radiometer
has a beam-width oif 7 or 14 deg, but it can be coupled to a telescope
increasing the resolution. The expected CMB polarization is at most a part per
milion. The polarimeter has been designed to be sensitive to this faint signal,
and it has been optimized to improve its long term stability, observing from
the ground. In this contribution the performances of the instrument are
presented, together with the preliminary test and observations.


title: The spin periods of magnetic cataclysmic variables

abstract:
  We have used a model of magnetic accretion to investigate the rotational
equilibria of magnetic cataclysmic variables (mCVs). This has enabled us to
derive a set of equilibrium spin periods as a function of orbital period and
magnetic moment which we use to estimate the magnetic moments of all known
intermediate polars. We further show how these equilibrium spin periods relate
to the polar synchronisation condition and use these results to calculate the
theoretical histogram describing the distribution of magnetic CVs as a function
of P_spin / P_orb. We demonstrate that this is in remarkable agreement with the
observed distribution assuming that the number of systems as a function of
white dwarf magnetic moment is distributed according to N(mu_1) d mu_1 ~
mu_1^{-2} d mu_1.


title: Simulations of Buoyant Bubbles in Galaxy Clusters

abstract:
  It is generally argued that most clusters of galaxies host cooling flows in
which radiative cooling in the centre causes a slow inflow. However, recent
observations by Chandra and XMM conflict with the predicted cooling flow rates.
Here we report highly resolved hydrodynamic simulations which show that buoyant
bubbles can offset the cooling in the inner regions of clusters and can
significantly delay the deposition of cold gas. The subsonic rise of bubbles
uplifts colder material from the central regions of the cluster. This colder
material appears as bright rims around the bubbles. The bubbles themselves
appear as depressions in the X-ray surface brightness as observed in a growing
number of clusters.


title: The Apsidal Antialignment of the HD 82943 System

abstract:
  We perform numerical simulations to explore the dynamical evolution of the HD
82943 planetary system. By simulating diverse planetary configurations, we find
two mechanisms of stabilizing the system: the 2:1 mean motion resonance between
the two planets can act as the first mechanism for all stable orbits. The
second mechanism is a dynamical antialignment of the apsidal lines of the
orbiting planets, which implies that the difference of the periastron
longitudes $\theta_{3}$ librates about $180^{\circ}$ in the simulations. We
also use a semi-analytical model to explain the numerical results for the
system under study.


title: Search for distortions in the spectrum of the Cosmic Microwave Radiation

abstract:
  We present preliminary results of TRIS, an experiment dedicated to the search
of deviations from a pure planckian distribution in the spectrum of the Cosmic
Microwave Background at frequencies close to 1 GHz


title: When you wish upon a star: Future developments in astronomical VLBI

abstract:
  In this paper, I present the likely technological development of VLBI, and
its impact on the astronomical community over the next 1-5 years. VLBI is
currently poised to take advantage of the rapid development in commercial
off-the-shelf (COTS) PC-based products. The imminent deployment of disk-based
recording systems will enable Gbps data rates to be achieved routinely by both
cm and mm-VLBI networks. This, together with anticipated improvements in
collecting area, receiver systems and coherence time is set to transform the
performance of VLBI in terms of both baseline and image noise sensitivity. At
the same time the feasibility of using fibre based communication networks as
the basis for production, real-time VLBI networks will begin. Fantastic new
correlator output data rates, and the ability to deal with these via powerful
PC clusters promises to expand the typical VLBI field-of-view to scales
previously reserved for connected, short baseline interferometers. By
simultaneously sampling the summed response of all compact radio sources within
(and indeed beyond) the half-power point of the VLBI telescope primary beam,
simple self-calibration of the target field will ALWAYS be possible at
frequencies below a few GHz. Unbiased, broad-band continuum surveys will be
conducted over huge areas of sky, and (redshifted) spectral-features will be
detected too. By the end of the decade the microJy radio sky will be accessible
to VLBI: dozens of sources will be simultaneosuly observed, correlated,
detected and fully analysed all within the same day.


title: Triggers and alerts with GLAST

abstract:
  We present preliminary results on Gamma Ray Burst (GRB) triggers with the
Gamma-ray Large Area Space Telescope (GLAST). After a brief summary of the
detector layout, GLAST expected performances on GRB detection are recalled.
Status report on the simulation software and preliminary triggers studies are
then reported, already showing significant improvement on EGRET results.


title: Dynamical shear instability

abstract:
  The dynamical shear instability is an important mixing process in the
advanced stages of the evolution of massive stars. We calculated different
models of 15 Mo with an initial rotational velocity, v(rot,ini)= 300 km/s to
investigate its efficiency. We found that the dynamical shear instability has a
timescale shorter than Oxygen burning timescale and that it slightly enlarges
the convective zones and smoothens the omega gradients throughout the
evolution.
  However, its effect is too localized to slow down the core of the star.


title: Particle acceleration in three-dimensional tearing configurations

abstract:
  In three-dimensional electromagnetic configurations that result from unstable
resistive tearing modes particles can efficiently be accelerated to
relativistic energies. To prove this resistive magnetohydrodynamic simulations
are used as input configurations for successive test particle simulations. The
simulations show the capability of three-dimensional non-linearly evolved
tearing modes to accelerate particles perpendicular to the plane of the
reconnecting magnetic field components. The simulations differ considerably
from analytical approaches by involving a realistic three-dimensional electric
field with a non-homogenous component parallel to the current direction. The
resulting particle spectra exhibit strong pitch-angle anisotropies. Typically,
about 5-8 % of an initially Maxwellian distribution is accelerated to the
maximum energy levels given by the macroscopic generalized electric potential
structure. Results are shown for both, non-relativistic particle acceleration
that is of interest, e.g., in the context of auroral arcs and solar flares, and
relativistic particle energization that is relevant, e.g., in the context of
active galactic nuclei.


title: Field-guided proton acceleration at reconnecting X-points in flares

abstract:
  An explicitly energy-conserving full orbit code CUEBIT, developed originally
to describe energetic particle effects in laboratory fusion experiments, has
been applied to the problem of proton acceleration in solar flares. The model
fields are obtained from solutions of the linearised MHD equations for
reconnecting modes at an X-type neutral point, with the additional ingredient
of a longitudinal magnetic field component. To accelerate protons to the
highest observed energies on flare timescales, it is necessary to invoke
anomalous resistivity in the MHD solution. It is shown that the addition of a
longitudinal field component greatly increases the efficiency of ion
acceleration, essentially because it greatly reduces the magnitude of drift
motions away from the vicinity of the X-point, where the accelerating component
of the electric field is largest. Using plasma parameters consistent with flare
observations, we obtain proton distributions extending up to gamma-ray-emitting
energies (>1MeV). In some cases the energy distributions exhibit a bump-on-tail
in the MeV range. In general, the shape of the distribution is sensitive to the
model parameters.


title: Observing the dark matter density profile of isolated galaxies

abstract:
  Using the Sloan Digital Sky Survey (SDSS), we probe the halo mass
distribution by studying the velocities of satellites orbiting isolated
galaxies. In a subsample that covers 2500 sq. degrees on the sky, we detect
about 3000 satellites with absolute blue magnitudes going down to M_B = -14;
most of the satellites have M_B=-16 to -18, comparable to the magnitudes of M32
and the Magellanic Clouds. After a careful, model-independent removal of
interlopers, we find that the line-of-sight velocity dispersion of satellites
declines with distance to the primary. For an L* galaxy the r.m.s.
line-of-sight velocity changes from ~120 km/s at 20 kpc to ~60 km/s at 350 kpc.
This decline agrees remarkably well with theoretical expectations, as all
modern cosmological models predict that the density of dark matter in the
peripheral parts of galaxies declines as rho_DM propto r^{-3}. Thus, for the
first time we find direct observational evidence of the density decline
predicted by cosmological models; we also note that this result contradicts
alternative theories of gravity such as MOND. We also find that the velocity
dispersion of satellites within 100 kpc scales with the absolute magnitude of
the central galaxy as sigma propto L^{0.3}; this is very close to the
Tully-Fisher relation for normal spiral galaxies.


title: Tomography of the atmosphere of long-period variable stars

abstract:
  This paper reviews the results obtained so far with the newly developed
tomographic technique, which probes the velocity field across the atmosphere of
long-period variable (LPV) stars. The method cross-correlates the optical
spectrum with numerical masks constructed from synthetic spectra and probing
layers of increasing depths. This technique reveals that the line doubling
often observed in LPV stars around maximum light is the signature of the shock
wave propagating in the atmosphere of these pulsating stars. Applications to
the Mira variables RT Cyg and RY Cep are presented, revealing the outward
propagation of the shock.


title:
EGRET upper limits on the high-energy gamma-ray emission of galaxy
  clusters

abstract:
  We report EGRET upper limits on the high-energy gamma-ray emission from
clusters of galaxies. EGRET observations between 1991 and 2000 were analyzed at
positions of 58 individual clusters from a flux-limited sample of nearby X-ray
bright galaxy clusters. Subsequently, a coadded image from individual galaxy
clusters has been analyzed using an adequately adapted diffuse gamma-ray
foreground model. The resulting 2 sigma upper limit for the average cluster is
\~ 6 x 10^{-9} cm^{-2} s^{-1} for E > 100 MeV. Implications of the
non--detection of prominent individual clusters and of the general inability to
detect the X-ray brightest galaxy clusters as a class of gamma-ray emitters are
discussed. We compare our results with model predictions on the high-energy
gamma-ray emission from galaxy clusters as well as with recent claims of an
association between unidentified or unresolved gamma-ray sources and Abell
clusters of galaxies and find these contradictory.


title: Stable 1:2 Resonant Periodic Orbits in Elliptic Three-Body Systems

abstract:
  The results of an extensive numerical study of the periodic orbits of planar,
elliptic restricted three-body planetary systems consisting of a star, an inner
massive planet and an outer mass-less body in the external 1:2 mean-motion
resonance are presented. Using the method of differential continuation, the
locations of the resonant periodic orbits of such systems are identified and
through an extensive study of their phase-parameter space, it is found that the
majority of the resonant periodic orbits are unstable. For certain values of
the mass and the orbital eccentricity of the inner planet, however, stable
periodic orbits can be found. The applicability of such studies to the 1:2
resonance of the extrasolar planetary system GJ876 is also discussed.


title: Far-Ultraviolet Emission from Elliptical Galaxies at z=0.33

abstract:
  We present far-ultraviolet (far-UV) images of the rich galaxy cluster
ZwCl1358.1+6245, taken with the Space Telescope Imaging Spectrograph on board
the Hubble Space Telescope (HST). When combined with archival HST observations,
our data provide a measurement of the UV-to-optical flux ratio in 8 early-type
galaxies at z=0.33. Because the UV flux originates in a population of evolved,
hot, horizontal branch (HB) stars, this ratio is potentially one of the most
sensitive tracers of age in old populations -- it is expected to fade rapidly
with lookback time. We find that the UV emission in these galaxies, at a
lookback time of 3.9 Gyr, is significantly weaker than it is in the current
epoch, yet similar to that in galaxies at a lookback time of 5.6 Gyr. Taken at
face value, these measurements imply different formation epochs for the massive
ellipticals in these clusters, but an alternative explanation is a "floor" in
the UV emission due to a dispersion in the parameters that govern HB
morphology.


title: Dark Matter Spikes and Indirect Detection

abstract:
  Annihilation radiation from supersymmetric particles at the Galactic center
could be greatly enhanced if the dark matter density is peaked around the
supermassive black hole. Arguments for and against the existence of density
spikes are reviewed. Spikes are destroyed during mergers, and there is strong
evidence for this effect in stellar density profiles. The dark matter spike at
the Galactic center probably suffered this fate.


title: Quasars Clustering at z approx 3 on Scales less sim 10 h^{-1} Mpc

abstract:
  We test the hypothesis whether high redshift QSOs would preferentially appear
in small groups or pairs, and if they are associated with massive, young
clusters. We carried out a photometric search for \Ly emitters on scales
$\lesssim 10 h^{-1}$ Mpc, in the fields of a sample of 47 $z\approx3$ known
QSOs. Wide and narrow band filter color-magnitude diagrams were generated for
each of the $6'.6\times6'.6$ fields. A total of 13 non resolved objects with a
significant color excess were detected as QSO candidates at a redshift similar
to that of the target. All the candidates are significantly fainter than the
reference QSOs, with only 2 of them within 2 magnitudes of the central object.
Follow-up spectroscopic observations have shown that 5, i.e., about 40% of the
candidates, are QSOs at the same redshift of the target; 4 are QSOs at
different z (two of them probably being a lensed pair at z = 1.47); 2
candidates are unresolved HII galaxies at z$\sim$0.3; one unclassified and one
candidate turned out to be a CCD flaw. These data indicate that at least 10% of
the QSOs at z$\sim$3 do have companions.
  We have also detected a number of resolved, rather bright \Ly Emitter
Candidates. Most probably a large fraction of them might be bright galaxies
with [OII] emission, at z$\approx$ 0.3. The fainter population of our
candidates corresponds to the current expectations. Thus, there are no strong
indication for the existence of an overdensity of \Ly galaxies brighter than m
$\approx$ 25 around QSOs at $z\approx$ 3.


title:
Chandra Temperature Map of Abell 754 and Constraints on Thermal
  Conduction

abstract:
  We use Chandra data to derive a detailed gas temperature map of the nearby,
hot, merging galaxy cluster A754. Combined with the X-ray and optical images,
the map reveals a more complex merger geometry than previously thought,
possibly involving more than two subclusters or a cool gas cloud sloshing
independently from its former host subcluster. In the cluster central region,
we detect spatial variations of the gas temperature on all linear scales, from
100 kpc (the map resolution) and up, which likely remain from a merger shock
passage. These variations are used to derive an upper limit on effective
thermal conductivity on a 100 kpc scale, which is at least an order of
magnitude lower than the Spitzer value. This constraint pertains to the bulk of
the intracluster gas, as compared to the previously reported estimates for cold
fronts (which are rather peculiar sites). If the conductivity in a tangled
magnetic field is at the recently predicted higher values (i.e., about 1/5 of
the Spitzer value), the observed suppression can be achieved, for example, if
the intracluster gas consists of magnetically isolated domains.


title: Circumstellar Interaction Around Supernovae

abstract:
  Circumstellar interaction has been observed around all types of massive star
supernovae, especially at radio and X-ray wavelengths. The interaction shells
in Type Ib/c supernovae appear to be moving rapidly, although SN 1998bw remains
the only case for which the evidence points to relativistic expansion. Type IIP
supernovae have relatively low mass loss rates, consistent with moderate mass
single stars at the ends of their lives. Type IIb and some IIL and IIn
supernovae can have strong mass loss leading up to the explosion, which occurs
in a star with little H on it. The mass loss may be driven by the luminosity of
the late burning stages.


title: STACEE Observations of Mrk 421 During the 2001 Flare

abstract:
  STACEE is a ground based gamma-ray observatory that uses a heliostat array,
built for solar energy research, to detect atmospheric Cherenkov radiation from
gamma-ray initiated extensive air showers. During the first half of 2001, a
prototype detector, STACEE-48, was used to detect the blazar Markarian 421,
which was in an extremely active state. Observations from March to May of 2001
yielded an integral flux of (8.0+/-0.7_{stat}+/-1.5_{sys})x 10^-10 1/cm^2/s at
energies above 140+/-20 GeV, and provide some evidence of correlated trends on
time scales of a week or more in the GeV and X-ray bands.


title: Pulsar Wind Nebulae: Theoretical Aspects and Observational Constraints

abstract:
  Of the known pulsar wind nebulae, 8 are good candidates for being in the
early stage of evolution where the wind nebula is interacting with the freely
expanding supernova ejecta. Several of these have been identified with
historical supernovae. Although the identification of SN 1181 with 3C 58 has
been thought to be relatively secure, the large size of the nebula, the amount
of swept up mass, and the internal energy indicate a larger age. For G11.2-0.3,
the nebular size and internal energy are consistent with the identification
with the possible supernova of 386. Although the Crab Nebula appears to have
approximate energy equipartition between particles and the magnetic field, the
nebulae 3C 58 and MSH 15-52 appear to be particle dominated. The low magnetic
field is consistent with models in which the nebulae are created by a shocked
pulsar wind.


title: A Deep Chandra Catalog of X-ray Point Sources toward the Galactic Center

abstract:
  (abridged) We present a catalog of 2357 point sources detected during 590 ks
of Chandra observations of the 17-by-17 arcminute field around Sgr A*. This
field encompasses a physical area of 40 by 40 pc at a distance of 8 kpc. The
completeness limit of the sample at the Galactic center is 10^{31} erg s^{-1}
(2.0--8.0 keV), while the detection limit is an order of magnitude lower. The
281 sources detected below 1.5 keV are mainly in the foreground of the Galactic
center, while comparisons to the Chandra deep fields at high Galactic latitudes
suggest that only about 100 of the observed sources are background AGN. The
surface density of absorbed sources (not detected below 1.5 keV) falls off as
1/theta away from Sgr A*, in agreement with the distribution of stars in
infrared surveys. Point sources brighter than our completeness limit produce
10% of the flux previously attributed to diffuse emission. The log(N)-log(S)
distribution of the Galactic center sources is extremely steep (power-law slope
alpha = 1.7). If this distribution extends down to a flux of 10^{-17} erg
cm^{-1} s^{-1} (10^{29} erg s^{-1} at 8 kpc, 2.0--8.0 keV) with the same slope,
then point sources would account for all of the previously reported diffuse
emission. Therefore, the 2.0--8.0 keV luminosity distribution must flatten
between 10^{29} - 10^{31} erg s^{-1}. Finally, the spectra of more than half of
the Galactic center sources are very hard, and can be described by a power law
($E^{-Gamma}) with photon index Gamma < 1. Such hard spectra have been seen
previously only from magnetically accreting white dwarfs and wind-accreting
neutron stars, suggesting that there are large numbers of these systems in our
field.


title: SiO Maser Survey of Cold IRAS Sources

abstract:
  We present the results of observations of cold IRAS sources in the Galactic
disk area, -10 < l < 100 and |b|<5, in the SiO J=1-0, v=1 and 2 maser lines.
SiO masers were detected in 51 out of 143 observed sources; 45 were new
detections in SiO masers. The selected IRAS sources were objects with dust
temperatures of between 160 and 280 K. According to a confirmation using 2MASS
near-infrared images, a majority of the sample are AGB or post-AGB stars,
although dense cores in the star-forming regions (or dusty HII regions) are
involved in part of the sample. Among new detections, two were candidates for
post-AGB stars: IRAS 18450-0148 (W 43A), and 19312+1950. We found that the
intensity ratios of the SiO J= 1-0, v=2 to the v=1 line of the objects clearly
correlate with those IRAS colors. The detection rates of SiO masers tend to
increase toward the Galactic center as well as the cases of previous SiO maser
surveys of typical AGB stars. No strong associations of the objects to the
spiral arms were found. The radial-velocity dispersion of the present sample is
comparable with the dispersion of the SiO maser sample of typical AGB stars.
These facts suggest that the present sample of cold IRAS sources with SiO
masers has a kinematic property very similar with that of typical AGB stars.


title: Supernovae, Gamma-Ray Bursts, and Stellar Rotation

abstract:
  One of the most dramatic possible consequences of stellar rotation is its
influence on stellar death, particularly of massive stars. If the angular
momentum of the iron core when it collapses is such as to produce a neutron
star with a period of 5 ms or less, rotation will have important consequences
for the supernova explosion mechanism. Still shorter periods, corresponding to
a neutron star rotating at break up, are required for the progenitors of
gamma-ray bursts (GRBs). Current stellar models, while providing an excess of
angular momentum to pulsars, still fall short of what is needed to make GRBs.
The possibility of slowing young neutron stars in ordinary supernovae by a
combination of neutrino-powered winds and the propeller mechanism is discussed.
The fall back of slowly moving ejecta during the first day of the supernova may
be critical. GRBs, on the other hand, probably require stellar mergers for
their production and perhaps less efficient mass loss and magnetic torques than
estimated thus far.


title:
Presupernova Evolution of Rotating Massive Stars and the Rotation Rate
  of Pulsars

abstract:
  Rotation in massive stars has been studied on the main sequence and during
helium burning for decades, but only recently have realistic numerical
simulations followed the transport of angular momentum that occurs during more
advanced stages of evolution. The results affect such interesting issues as
whether rotation is important to the explosion mechanism, whether supernovae
are strong sources of gravitational radiation, the star's nucleosynthesis, and
the initial rotation rate of neutron stars and black holes. We find that when
only hydrodynamic instabilities (shear, Eddington-Sweet, etc.) are included in
the calculation, one obtains neutron stars spinning at close to critical
rotation at their surface -- or even formally in excess of critical. When
recent estimates of magnetic torques (Spruit 2002) are added, however, the
evolved cores spin about an order of magnitude slower. This is still more
angular momentum than observed in young pulsars, but too slow for the collapsar
model for gamma-ray bursts.


title:
Discovery of an ultra-cool subdwarf: LSR1425+7102, first star with
  spectral type sdM8.0

abstract:
  We report the discovery of the coolest subdwarf reported to date. The star
LSR1425+7102 was discovered in our survey for faint high proper motion stars in
the northern sky. Follow-up spectroscopy revealed the star to be a very red
object with the characteristic signature of M subdwarfs: strong CaH bands but
relatively weaker TiO bands. The CaH molecular band at $\approx\lambda$6900\AA\
is particularly strong. By extrapolating the empirical relationship between the
strength of the CaH molecular band and the subdwarf subtype, we conclude that
LSR1425+7102 is the first star to be discovered with spectral type sdM8.0.


title: The Discovery of Two Nearby Carbon Dwarfs

abstract:
  The comparison of optical and 2MASS near-infrared photometry for large
samples of catalogued proper motion stars has the potential to discover
previously unrecognized nearby objects of rare type. In this paper we present
the discovery of two new carbon dwarfs, LSR 2105+2514 and LP 758-43, which were
drawn from proper motion lists and which lie in a sparsely populated part of
optical/near-IR color-color space. Their optical spectra, exhibiting
absorptions by C_2 and/or CN, are discussed. LSR 2105+2514 is believed to lie
within 200 pc and would have M_(K_s) < 6.7, making it lower in luminosity than
any carbon dwarf with a measured trigonometric parallax. LP 758-43, which is
not as red but still probably cooler than the best studied carbon dwarfs, is
believed to lie within 360 pc. Using our optical/near-infrared selection
technique on published lists of proper motion stars, we hope in the near future
to expand further the current sample of carbon dwarfs, which numbers only 31
objects at this writing.


title: Discovery of Early Optical Emission from GRB 021211

abstract:
  We report our discovery and early time optical, near-infrared, and radio
wavelength follow-up observations of the afterglow of the gamma-ray burst GRB
021211. Our optical observations, beginning 21 min after the burst trigger,
demonstrate that the early afterglow of this burst is roughly three magnitudes
fainter than the afterglow of GRB 990123 at similar epochs, and fainter than
almost all known afterglows at an epoch of 1d after the GRB. Our near-infrared
and optical observations indicate that this is not due to extinction. Combining
our observations with data reported by other groups, we identify the signature
of a reverse shock. This reverse shock is not detected to a 3-sigma limit of
110 uJy in an 8.46-GHz VLA observation at t=0.10d, implying either that the
Lorentz factor of the burst gamma <~ 200, or that synchrotron self-absorption
effects dominate the radio emission at this time. Our early optical
observations, near the peak of the optical afterglow (forward shock), allow us
to characterize the afterglow in detail. Comparing our model to flux upper
limits from the VLA at later times, t >~ 1 week, we find that the late-time
radio flux is suppressed by a factor of two relative to the >~ 80 uJy peak flux
at optical wavelengths. This suppression is not likely to be due to synchrotron
self-absorption or an early jet break, and we suggest instead that the burst
may have suffered substantial radiative corrections.


title:
The initial Helium content of Galactic Globular Cluster stars from the
  R-parameter: comparison with the CMB constraint

abstract:
  Recent precise determinations of the primordial He-abundance (Y_p) from
cosmic microwave background (CMB) analyses and cosmological nucleosynthesis
computations, provide Y_p=0.248$\pm$0.001. On the other hand, recent works on
the initial He-abundance of Galactic globular cluster (GGC) stars, making use
of the R parameter as He-indicator, have consistently obtained
$Y_{GGC}\sim$0.20.
  In light of this serious discrepancy that casts doubt on the adequacy of low
mass He-burning stellar models, we have rederived the initial He-abundance for
stars in two large samples of GGCs, by employing theoretical models computed
using new and more accurate determinations of the Equation of State for the
stellar matter, and of the uncertain $^{12}$C$(\alpha,\gamma)^{16}$O reaction
rate. Our models include semiconvection during the central convective
He-burning phase, while the breathing pulses are suppressed, in agreement with
the observational constraints coming from the measurements of the R_2 parameter
in a sample of clusters. By taking into account the observational errors on the
individual R-parameter values, as well as uncertainties in the GGC [Fe/H]
scale, treatment of convection and $^{12}$C$(\alpha,\gamma)^{16}$O reaction
rate, we have obtained, respectively, a mean $Y_{GGC}$=0.243$\pm$0.006 and
$Y_{GGC}$=0.244$\pm$0.006 for the two studied GGC samples. These estimates are
now fully consistent with Y_p obtained from CMB studies. Moreover, the trend of
the individual He-abundances with respect to [Fe/H] is consistent with no
appreciable He-enrichment along the GGC metallicity range.


title: Evolution of an afterglow with a hard electron spectrum

abstract:
  Diffusive shock acceleration theory suggests that the ``universal'' energy
spectrum of electrons with a power-law index p approximately equal to 2.3,
commonly used to model GRB afterglows, cannot extend below an electron lorentz
factor gamma_e equal to the bulk lorentz factor of the blast wave multiplied by
the ratio of proton and electron masses. We suggest that the electron energy
distribution has a slope p < 2 below this limit, down to an appropriate
gamma_m. A two-slope spectrum such as this provides a good model for the
afterglow of GRB010222.


title: The origin of sdB stars (II)

abstract:
  We have carried out a detailed binary populations synthesis (BPS) study of
the formation of subdwarf B (sdB) stars and related objects (sdO, sdOB stars)
using the latest version of the BPS code developed by Han et al.(1994, 1995a,
1995b, 1998, 2001). We systematically investigate the importance of the five
main evolutionary channels in which the sdB stars form after one or two
common-envelope (CE) phases, one or two phases of stable Roche-lobe overflow
(RLOF) or as the result of the merger of two helium white dwarfs (WD) (see Han
et al. 2002, Paper I). Our best BPS model can satisfactorily explain the main
observational characteristics of sdB stars, in particular their distributions
in the orbital period - minimum companion mass diagram and in the effective
temperature - surface gravity diagram, their distributions of orbital period,
log (g theta^4), and mass function, their binary fraction and the fraction of
sdB binaries with WD companions, their birthrates and their space density. We
obtain a Galactic formation rate, a total number in the Galaxy, the intrinsic
binary fraction for sdB stars. We also predict a distribution of masses for sdB
stars that is wider than is commonly assumed and that some sdB stars have
companions of spectral type as early as B. The percentage of A type stars with
sdB companions can in principle be used to constrain some of the important
parameters in the binary evolution model. We conclude that (a) the first RLOF
phase needs to be more stable than is commonly assumed; (b) mass transfer in
the first stable RLOF phase is non-conservative, and the mass lost from the
system takes away a specific angular momentum similar to that of the system;
(c) common-envelope ejection is very efficient.


title: Star Formation in Turbulent Interstellar Gas

abstract:
  Understanding the star formation process is central to much of modern
astrophysics. For several decades it has been thought that stellar birth is
primarily controlled by the interplay between gravity and magnetostatic
support, modulated by ambipolar diffusion. Recently, however, both
observational and numerical work has begun to suggest that supersonic
interstellar turbulence rather than magnetic fields controls star formation.
Supersonic turbulence can provide support against gravitational collapse on
global scales, while at the same time it produces localized density
enhancements that allow for collapse on small scales. The efficiency and
timescale of stellar birth in Galactic molecular clouds strongly depend on the
properties of the interstellar turbulent velocity field, with slow,
inefficient, isolated star formation being a hallmark of turbulent support, and
fast, efficient, clustered star formation occurring in its absence.


title:
Experimental f-value and isotopic structure for the Ni I line blended
  with [OI] at 6300A

abstract:
  We have measured the oscillator strength of the Ni I line at 6300.34 \AA,
which is known to be blended with the forbidden [O I] $\lambda$6300 line, used
for determination of the oxygen abundance in cool stars. We give also
wavelengths of the two isotopic line components of $^{58}$Ni and $^{60}$Ni
derived from the asymmetric laboratory line profile. These two line components
of Ni I have to be considered when calculating a line profile of the 6300 \AA\
feature observed in stellar and solar spectra. We also discuss the labelling of
the energy levels involved in the Ni I line, as level mixing makes the
theoretical predictions uncertain.


title:
Simultaneous Chandra and RXTE observations of the nearby bright Seyfert
  2 galaxy NGC4945

abstract:
  We analyze recent simultaneous Chandra/RXTE observations of the Seyfert 2
galaxy NGC 4945. The unprecedented spatial resolution of Chandra means we are
able to separate the spectra of the nucleus, starburst and superwind regions,
while the RXTE data extend the spectrum to higher energies. The extreme
absorbing column of $N_H\sim 4\times 10^{24}$ cm$^{-2}$ means that the nucleus
is only seen directly above 8--10 keV, while the lower energy spectrum from the
nuclear region in Chandra is dominated by reflection. By contrast, the
superwind is dominated by emission from hot plasma, but the starburst region
contains both hot plasma and reflection signatures. To form a reflected
spectrum requires that the starburst region contains clumps of cool, optically
thick material, perhaps star forming cores, which are irradiated by 7--10 keV
photons from the nucleus. Since photons of this energy are obscured along the
line sight then this confirms the result of Madejski et al. (2000) that the
extreme absorbtion material is disk-like rather than a torus. However, the
IR/optical limits on the lack of high excitation emission lines show that by
contrast the lower energy photons from the nucleus are obscured in all
directions. We discuss the complex absorption structure revealed by these
observations, and propose an an overall source geometry in which the nucleus is
completely embedded in material with $N_H\sim 10^{23}$ cm$^{-2}$


title:
Electromagnetic Catastrophe in Ultrarelativistic Shocks and the Prompt
  Emission of Gamma-Ray Bursts

abstract:
  It is shown that an ultrarelativistic shock with the Lorentz factor of order
of tens or higher propagating in a moderately dense interstellar medium
(density above $\sim 1000 $ cm$^{-3}$) undergoes a fast dramatic transformation
into a highly radiative state. The process leading to this phenomenon resembles
the first order Fermi acceleration with the difference that the energy is
transported across the shock front by photons rather than protons. The
reflection of the energy flux crossing the shock front in both directions is
due to photon-photon pair production and Compton scattering. Such mechanism
initiates a runaway nonlinear pair cascade fed directly by the kinetic energy
of the shock. Eventually the cascade feeds back the fluid dynamics, converting
the sharp shock front into a smooth velocity gradient and the runaway evolution
changes to a quasi-steady state regime. This effect has been studied
numerically using the nonlinear Large Particle Monte-Carlo code for the
electromagnetic component and a simplified hydrodynamic description of the
fluid. The most interesting application of the effect is the phenomenon of
gamma-ray bursts where it explains a high radiative efficiencyand gives a
perspective to explain spectra of GRBs and their time variability. The results
predict a phenomenon of ``GeV bursts'' which arise if the density of the
external medium is not sufficiently high to provide a large compactness.


title: Major Mergers and the Origin of Elliptical Galaxies

abstract:
  The formation of elliptical galaxies as a result of the merging of spiral
galaxies is discussed. We analyse a large set of numerical N-Body merger
simulations which show that major mergers can in principle explain the observed
isophotal fine structure of ellipticals and its correlation with kinematical
properties. Equal-mass mergers lead to boxy, slowly rotating systems,
unequal-mass mergers produce fast rotating and disky ellipticals. However,
several problems remain. Anisotropic equal mass mergers appear disky under
certain projections which is not observed. The intrinsic ellipticities of
remnants are often larger than observed. Finally, although unequal-mass mergers
produce fast rotating ellipticals, the remnants are in general more anisotropic
than expected from observations. Additional processes seem to play an important
role which are not included in dissipationless mergers. Resolving these
problems might provide interesting new information on the structure and gas
content of the progenitors of early-type galaxies.


title:
Dust emissivity in the Submm/Mm: SCUBA and SIMBA observations of Barnard
  68

abstract:
  We have observed the dark cloud Barnard 68 with SCUBA at 850 um and with
SIMBA at 1.2 mm. The submillimetre and millimetre dust emission correlate well
with the extinction map of Alves, Lada and Lada (2001).The A_V/850um
correlation is clearly not linear and suggests lower temperatures for the dust
in the inner core of the cloud. Assuming a model for the temperature gradient,
we derive the cloud-averaged dust emissivities (normalised to the V-Band
extinction efficiency) at 850 um and 1.2 mm. We find k_850um/k_V = 4.0 +/- 1.0
x 10^-5 and k_1.2mm/k_V = 9.0 +/- 3.0 x 10^-6. These values are compared with
other determinations in this wavelength regime and with expectations for models
of diffuse dust and grain growth in dense clouds.


title: Gamma-ray bursts: optical afterglows in the deep Newtonian phase

abstract:
  Gamma-ray burst remnants become trans-relativistic typically in days to tens
of days, and they enter the deep Newtonian phase in tens of days to months,
during which the majority of shock-accelerated electrons will no longer be
highly relativistic. However, a small portion of electrons are still
accelerated to ultra-relativistic speeds and capable of emitting synchrotron
radiation. The distribution function for electrons is re-derived here so that
synchrotron emission from these relativistic electrons can be calculated. Based
on the revised model, optical afterglows from both isotropic fireballs and
highly collimated jets are studied numerically, and compared to analytical
results. In the beamed cases, it is found that, in addition to the steepening
due to the edge effect and the lateral expansion effect, the light curves are
universally characterized by a flattening during the deep Newtonian phase.


title: "The Carina Project": color magnitude diagram and radial distribution

abstract:
  We present B, V photometric data of the Carina Dwarf Spheroidal Galaxy
collected with the Wide Field Imager (WFI) available at the 2.2m MPI/ESO
telescope. We briefly discuss the main features of the color magnitude diagram
and in particular the mix of stellar populations present in this galaxy. A
preliminary analysis of the spatial distribution of these populations over a
substantial fraction of the body of the galaxy is also presented.


title: The cannonball model of gamma ray bursts

abstract:
  The cannonball model (CB) of gamma ray bursts (GRBs) is incredibly more
successful than the standard blast-wave models (SM) of GRBs, which suffer from
profound inadequacies and limited predictive power. The CB model is falsifiable
in its hypothesis and results. Its predictions are summarized in simple
analytical expressions, derived, in fair approximations, from first principles.
It provides a good description on a universal basis of the properties of
long-duration GRBs and of their afterglows (AGs).


title: Hard GRB spectra: thermal vs non-thermal emission

abstract:
  We consider the evidence for very hard low energy spectra during the prompt
phase of Gamma Ray Bursts (GRB). In particular we examine the spectral
evolution of GRB 980306 together with the detailed analysis of some other
bursts already presented in the literature (GRB 911118, GRB 910807, GRB 910927
and GRB 970111), and check for the significance of their hardness by applying
different tests. The hard spectra of these bursts and their evolution constrain
several non--thermal emission models, which appear inadequate to account for
these cases. The extremely hard spectra at the beginning of their prompt
emission are also compared with a black body spectral model: the resulting fits
are remarkably good. These findings on the possible thermal character of the
evolving spectrum and their implications on the GRB physical scenario can be
considered in the frameworks of photospheric models for a fireball which is
becoming optically thin, and of the Compton drag model. Both models appear to
be qualitatively and quantitatively consistent with the found spectral
characteristics.


title: Formation of polar ring galaxies

abstract:
  Polar ring galaxies are peculiar systems in which a gas rich, nearly polar
ring surrounds an early-type or elliptical host galaxy. Two formation scenarios
for these objects have been proposed: they are thought to form either in major
galaxy mergers or by tidal accretion of the polar material from a gas rich
donor galaxy. Both scenarios are studied through N-body simulations including
gas dynamics and star formation. Constraints on physical parameters are drawn
out, in order to determine which scenario is the most likely to occur. Polar
ring galaxies from each scenario are compared with observations and we discuss
whether the accretion scenario and the merging scenario account for
observational properties of polar ring galaxies. The conclusion of this study
is that the accretion scenario is both the most likely and the most supported
by observations. Even if the merging scenario is rather robust, most polar ring
galaxies are shown to be the result of tidal gas accretion events.


title: Nucleosynthesis in Baryon-Rich Outflows Associated With Gamma-Ray Bursts

abstract:
  Robust generation of gamma-ray bursts (GRBs) implies the formation of
outflows with very low baryon loads and highly relativistic velocities, but
more baryon-rich, slower outflows are also likely to occur in most GRB central
engine scenarios, either as ``circum-jet winds'' or ``failed GRBs''. Here we
study the possibility of nucleosynthesis within such baryon-rich outflows by
conducting detailed reaction network calculations in the framework of the basic
fireball model. It is shown that high baryon load fireballs attaining mildly
relativistic velocities can synthesize appreciable quantities of heavy neutron
capture elements with masses up to the platinum peak and beyond. Small but
interesting amounts of light elements such as deuterium and boron can also be
produced. Depending on the neutron excess and baryon load, the combination of
high entropy, rapid initial expansion and gradual expansion at later times can
cause the reaction flow to reach the fission regime, and its path can be
intermediate between those of the $r$- and $s$-processes (``$n$-process''). The
nucleosynthetic signature of these outflows may be observable in the companion
stars of black hole binary systems and in the most metal-poor stars,
potentially offering an important probe of the inner conditions of the GRB
source. Contribution to the solar abundances for some heavy elements may also
be possible. The prospects for further developments in various directions are
discussed.


title: Kinematics, turbulence and evolution of planetary nebulae

abstract:
  This paper discusses the location of a sample of planetary nebulae on the HR
diagram. We determine the internal velocity fields of 14 planetary nebulae from
high-resolution echelle spectroscopy, with the help of photoionization models.
The mass averaged velocity is shown to be a robust, simple parameter describing
the outflow. The expansion velocity and radius are used to define the dynamical
age; together with the stellar temperature, this gives a measurement of the
luminosity and core mass of the central star. The same technique is applied to
other planetary nebulae with previously measured expansion velocities, giving a
total sample of 73 objects. The objects cluster closely around the Schoenberner
track of 0.61 M_sun, with a very narrow distribution of core masses. The masses
are higher than found for local white dwarfs. The luminosities determined in
this way tend to be higher by a factor of a few than those derived from the
nebular luminosities. The discrepancy is highest for the hottest (most evolved)
stars. We suggest photon leakage as the likely cause. The innermost regions of
the non-[WC] nebulae tend to show strong acceleration. Together with the
acceleration at the ionization front, the velocity field becomes 'U'-shaped.
The presence of strong turbulent motions in [WC] nebulae is confirmed. Except
for this, we find that the [WC] stars evolve on the same tracks as non-[WC]
stars.


title: Latitude-dependent effects in the stellar wind of Eta Carinae

abstract:
  The Homunculus reflection nebula around eta Carinae provides a rare
opportunity to observe the spectrum of a star from multiple latitudes. We
present STIS spectra of several positions in the Homunculus, showing directly
that eta Car has an aspherical stellar wind. P Cygni absorption in Balmer lines
depends on latitude, with high velocities and strong absorption near the poles.
Stronger absorption at high latitudes is surprising, and it suggests higher
mass flux toward the poles, perhaps resulting from radiative driving with
equatorial gravity darkening on a rotating star. Reflected profiles of He I
lines are more puzzling, offering clues to the wind geometry and ionization
structure. During eta Car's high-excitation state in March 2000, the wind was
fast and dense at the poles, with higher ionization at low latitudes.
  Older STIS data obtained since 1998 reveal that this global stellar-wind
geometry changes during eta Car's 5.5 year cycle, and may suggest that this
star's spectroscopic events are shell ejections. Whether or not a companion
star triggers these outbursts remains ambiguous. The most dramatic changes in
the wind occur at low latitudes, while the dense polar wind remains relatively
undisturbed during an event. The apparent stability of the polar wind also
supports the inferred bipolar geometry. The wind geometry and its variability
have critical implications for understanding the 5.5 year cycle and long-term
variability, but do not provide a clear alternative to the binary hypothesis
for generating eta Car's X-rays.


title: Conditions for Generating Scale-Invariant Density Perturbations

abstract:
  We analyze the general conditions on the equation of state $w$ required for
quantum fluctuations of a scalar field to produce a scale-invariant spectrum of
density perturbations, including models which (in the four dimensional
effective description) bounce from a contracting to an expanding phase. We show
that there are only two robust cases: $w\approx -1$ (inflation) and $w \gg 1$
(the ekpyrotic/cyclic scenario). All other cases, including the $w \approx 0$
case considered by some authors, require extreme fine-tuning of initial
conditions and/or the effective potential. For the ekpyrotic/cyclic ($w \gg 1$)
case, we also analyze the small deviations from scale invariance.


title:
A study of velocity fields in the transition region of Epsilon Eri (K2
  V)

abstract:
  Analyses of the widths and shifts of optically thin emission lines in the
ultraviolet spectrum of the active dwarf Epsilon Eri (K2 V) are presented. The
spectra were obtained using the Space Telescope Imaging Spectrograph on the
Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. The line
widths are used to find the non-thermal energy density and its variation with
temperature from the chromosphere to the upper transition region. The energy
fluxes that could be carried by Alfven and acoustic waves are investigated, to
test their possible roles in coronal heating. Acoustic waves do not appear to
be a viable means of coronal heating. There is, in principle, ample flux in
Alfven waves, but detailed calculations of wave propagation are required before
definite conclusions can be drawn about their viability. The high sensitivity
and spectral resolution of the above instruments have allowed two-component
Gaussian fits to be made to the profiles of the stronger transition region
lines. The broad and narrow components which result share some similarities
with those observed in the Sun, but in Epsilon Eri the broad component is
redshifted relative to the narrow component and contributes more to the total
line flux. The possible origins of the two components and the energy fluxes
implied are discussed. On balance our results support the conclusion of Wood,
Linsky & Ayres, that the narrow component is related to Alfven waves reaching
to the corona, but the origin of the broad component is not clear.


title: Probing Distant Massive Black Holes with LISA

abstract:
  Idealized models are used to illustrate the potential of the Laser
Interferometer Space Antenna (LISA) as a probe of the largely unknown
population of cosmologically-distant Massive Black Holes (MBHs) and as a tool
to measure their masses with unprecedented accuracy. The models suggest that
LISA will most efficiently probe a MBH population of lower mass than the one
found in bright quasars and nearby galactic nuclei. The mass spectrum of these
MBHs could constrain formation scenarios for high-redshift, low-mass galaxies.


title: Scintillation Caustics in Planetary Occultation Light Curves

abstract:
  We revisit the GSC5249-01240 light curve obtained during its occultation by
Saturn's North polar region. In addition to refractive scintillations, the
power spectrum of intensity fluctuations shows an enhancement of power between
refractive and diffractive regimes. We identify this excess power as due to
high amplitude spikes in the light curve and suggest that these spikes are due
to caustics associated with ray crossing situations. The flux variation in
individual spikes follows the expected caustic behavior, including diffraction
fringes which we have observed for the first time in a planetary occultation
light curve. The presence of caustics in scintillation light curves require an
inner scale cut off to the power spectrum of underlying density fluctuations
associated with turbulence. Another possibility is the presence of gravity
waves in the atmosphere. While occultation light curves previously showed the
existence of refractive scintillations, a combination of small projected
stellar size and a low relative velocity during the event have allowed us to
identify caustics in this occultation. This has led us to re-examine previous
data sets, in which we have also found likely examples of caustics.


title: Gravitational Lensing by Dark Matter Caustics

abstract:
  Dark matter caustics have specific density profiles and, therefore, precisely
calculable gravitational lensing properties. We present a formalism which
simplifies the relevant calculations, and apply it to four specific cases. In
the first three, the line of sight is tangent to a smooth caustic surface. The
curvature of the surface at the tangent point is positive, negative or zero. In
the fourth case the line of sight passes near a cusp. For each we derive the
map between the image and source planes. In some cases, a point source has
multiple images and experiences infinite magnification when the images merge.
Unfortunately, for the dark matter caustics expected in realistic galactic halo
models, the angular resolution required to resolve the multiple images is not
presently achievable. A more promising approach aims to observe the distortions
caused by dark matter caustics in the images of extended sources such as radio
jets.


title: Variability Studies with SDSS

abstract:
  The potential of the Sloan Digital Sky Survey for wide-field variability
studies is illustrated using multi-epoch observations for 3,000,000 point
sources observed in 700 deg2 of sky, with time spans ranging from 3 hours to 3
years. These repeated observations of the same sources demonstrate that SDSS
delivers ~0.02 mag photometry with well behaved and understood errors. We show
that quasars dominate optically faint (r > 18) point sources that are variable
on time scales longer than a few months, while for shorter time scales, and at
bright magnitudes, most variable sources are stars.


title:
SiO Maser Survey toward the Inner Galactic Disk: 40 < l < 70 and |b| <
  10

abstract:
  We present the results of an SiO maser survey for color-selected IRAS sources
in the area 40 < l < 70 and |b| < 10 in the SiO J=1-0, v=1 and 2 transitions.
We detected 134 out of 272 observed sources in SiO masers; 127 were new
detections. A systematic difference in the detection rates between SiO and OH
maser searches was found. Especially, in the color ranges with
log(F_{25}/F_{12}) smaller than -0.1, the detection rate of the SiO masers is
significantly higher than that of OH masers. We found a possible kinematic
influence of the galactic arm on the distribution of SiO maser sources. It was
found that the velocity dispersion of SiO maser sources tends to decrease with
the galactocentric distance. Using the present and previous data of SiO maser
surveys, we found that the local velocity gradient of the rotational velocity
of the Galaxy is consistent with the values obtained from other kinds of disk
population stars within a statistical uncertainty. The Oort's constants, "A"
and "B", were computed from the gradient of the rotation curve for the present
data, and were consistent with the IAU standard values. In addition, in order
to check the reliability of IRAS positions, we observed toward the MSX
positions for 5 MSX counterparts, which are located more than 20" away (but
within 60") from IRAS positions. We detected all of these 5 sources in SiO
masers.


title:
Three-dimensional MHD Simulations of Radiatively Inefficient Accretion
  Flows

abstract:
  We present three-dimensional MHD simulations of rotating radiatively
inefficient accretion flows onto black holes. In the simulations, we
continuously inject magnetized matter into the computational domain near the
outer boundary, and we run the calculations long enough for the resulting
accretion flow to reach a quasi-steady state. We have studied two limiting
cases for the geometry of the injected magnetic field: pure toroidal field and
pure poloidal field. In the case of toroidal field injection, the accreting
matter forms a nearly axisymmetric, geometrically-thick, turbulent accretion
disk. The disk resembles in many respects the convection-dominated accretion
flows found in previous numerical and analytical investigations of viscous
hydrodynamic flows. Models with poloidal field injection evolve through two
distinct phases. In an initial transient phase, the flow forms a relatively
flattened, quasi-Keplerian disk with a hot corona and a bipolar outflow.
However, when the flow later achieves steady state, it changes in character
completely. The magnetized accreting gas becomes two-phase, with most of the
volume being dominated by a strong dipolar magnetic field from which a thermal
low-density wind flows out. Accretion occurs mainly via narrow slowly-rotating
radial streams which `diffuse' through the magnetic field with the help of
magnetic reconnection events.


title: Photometric redshift using the far-infrared SED

abstract:
  A method for using the sub-millimeter band to determine photometric redshifts
of luminous high-z dusty galaxies is presented. It is based on the observation
that local ultra-luminous IR galaxies show an average spectral energy
distribution which has a remarkably small dispersion for wavelengths >50
microns. The shape of the long wavelength part is independent on whether the
local ULIRG possesses an AGN or not. A local template is derived from a sample
of ULIRG data presented by Klaas et al. (2001). Using this template and the
internal dispersion in its shape, it is shown that observations at two fixed
submm wavelengths can be used to determine the photometric redshift of galaxies
in the redshift range 1<z<5. The uncertainty in the redshift arising from the
template SED amounts to \Delta z/z ~ 0.3.


title:
3-D Simulations of the Chemical and Dynamical Evolution of the Galactic
  Bulge

abstract:
  A three-dimensional hydrodynamical N-body model for the formation of the
Galaxy is presented with special attention to the formation of the bulge
component. Starting with cosmologically motivated initial conditions, we obtain
a qualitatively similar stellar system to the Galaxy. Then we analyze the
chemical and kinematic properties of the bulge stars in our model and find
qualitative agreement with observational data. The early evolution of our model
has revealed that most bulge stars form during the sub-galactic merger (merger
component of the bulge stars). Because of the strong star burst induced by the
merger, the metallicity distribution function of such stars becomes as wide as
observed. We find that another group of the bulge stars forms later in the
inner region of the disk (non-merger component of the bulge stars). Because of
the difference in the formation epoch, the main source of iron for this group
of stars is different from the merger component. Iron in the merger and
non-merger components comes mainly from Type II and Type Ia supernovae,
respectively. Since a Type Ia supernova ejects $\sim$ 10 times more iron than a
Type II supernova, [Fe/H] of the non-merger component tends to be higher than
that of the merger component, which widens the metallicity distribution
function. From these results, we suggest that the Galactic bulge consists of
two chemically different components; one has formed quickly through the
sub-galactic clump merger in the proto-galaxy and the other has formed
gradually in the inner disk.


title: Is There a Disc in the Superluminal Quasars?

abstract:
  We present a new evidence of the accretion disc in active galactic nuclei, by
examining the properties of the Ha emission line versus viewing angle, in a
sample of superluminal (SL) quasars. Both line velocity width (FWHM) and rest
equivalent width (EW) correlate with viewing angle. These correlations are
quantitatively consistent with a disc geometry for both the line and the
underlying continuum source.


title: The First Sources of Light

abstract:
  We review recent theoretical results on the formation of the first stars and
quasars in the universe, and emphasize related open questions. In particular,
we list important differences between the star formation process at high
redshifts and in the present-day universe. We address the importance of heavy
elements in bringing about the transition from an early star formation mode
dominated by massive stars, to the familiar mode dominated by low mass stars,
at later times. We show how gamma-ray bursts can be utilized to probe the first
epoch of star formation. Finally, we discuss how the first supermassive black
holes could have formed through the direct collapse of primordial gas clouds.


title: CNO abundances in the Damped Ly-alpha clouds

abstract:
  Damped Ly alpha clouds provide information on the chemistry of distant and
metal poor regions of the universe. In these clouds for observational
difficulties N and O are among the last elements to be measured, and C has
still to be measured with precision. In combining the extant CNO abundances, we
avail of a sample which includes 33 N measurements or significant limits, a
dozen of O measurements, and only few tentative measurements for C. O is found
to track both S and Si rather closely without signatures of any peculiar
behaviour and the few [O/Zn] ratios available show a mild alpha/iron-peak
enhancement which reinforces earlier evidence. The few tentative C measurements
point to roughly solar [C/Zn] and [C/Si] ratios. N abundances are rather
complex with N/alpha ratios showing a bimodal distribution. The majority of the
values form a first plateau at [N/Si]=-0.82 (+/- 0.13) and about 25 % form a
second plateau at [N/Si]= -1.45 (+/- 0.05). The high values are at the level of
the Blue Compact Dwarfs but they extend further towards lower metallicities.
The lower plateau is a new feature of DLAs with no other counterparts. The two
plateaux are found for different values of the N abundance with the transition
at [N/H] ~ -3.0. We argue that this results from the delayed release of N
between massive and intermediate mass stars with the lower plateau produced by
massive stars (M> 8 M_sun) only, which accounts for the small dispersion. The
systems on the lower plateau are relatively young and imply a continuous
formation of the DLAs. While the interpretation of the N/O in the DLAs needs to
be confirmed, these observations could ultimately prove crucial for the
interpretation of the early N nucleosynthesis.


title:
Spectral modeling of the three spectral states of the Galactic
  microquasar GRS 1915+105

abstract:
  We have analyzed Rossi X-ray Timing Explorer spectral data of the Galactic
micro-quasar GRS 1915+105 in its various spectral states, as defined by Belloni
et al. (2000). In states A and B the spectra are dominated by a strong soft
thermal component, accompanied by a weak harder tail. The soft component is
rather complex and cannot be described as a simple accretion disk emission.
Relativistic effects in Kerr metric contribute to the complexity of the soft
component but are not sufficient to fully account for it. As found previously,
state C spectra are dominated by a Comptonized component, with small
contribution from disk photons. The X-ray reprocessed component is highly
significant in those spectra and, in contrast to the usual hard state spectra
from accreting black holes, it is highly ionized.


title: Temperature determination via STJ optical spectroscopy

abstract:
  ESA's Superconducting Tunnel Junction (STJ) optical photon-counting camera
(S-Cam2) incorporates an array of pixels with intrinsic energy sensitivity.
Using the spectral fitting technique common in X-ray astronomy, we fit black
bodies to nine stellar spectra, ranging from cool flare stars to hot white
dwarfs. The measured temperatures are consistent with literature values at the
expected level of accuracy based on the predicted gain stability of the
instrument. Having also demonstrated that systematic effects due to count rate
are likely to be small, we then proceed to apply the temperature determination
method to four cataclysmic variable (CV) binary systems. In three cases we
measure the temperature of the accretion stream, while in the fourth we measure
the temperature of the white dwarf. The results are discussed in the context of
existing CV results. We conclude by outlining the prospects for future versions
of S-Cam.


title: The Effects of Stellar Yields with Rotation on Chemical Evolution Models

abstract:
  We summarise the results of recent work investigating the effects of stellar
yields which take into account rotation on the predictions of chemical
evolution models for early populations of galaxies.


title: A Tidally-Disrupted Asteroid Around the White Dwarf G29-38

abstract:
  The infrared excess around the white dwarf G29-38 can be explained by
emission from an opaque flat ring of dust with an inner radius 0.14 of the
radius of the Sun and an outer radius approximately equal to the Sun's. This
ring lies within the Roche region of the white dwarf where an asteroid could
have been tidally destroyed, producing a system reminiscent of Saturn's rings.
Accretion onto the white dwarf from this circumstellar dust can explain the
observed calcium abundance in the atmosphere of G29-38. Either as a bombardment
by a series of asteroids or because of one large disruption, the total amount
of matter accreted onto the white dwarf may have been comparable to the total
mass of asteroids in the Solar System, or, equivalently, about 1% of the mass
in the asteroid belt around the main sequence star zeta Lep.


title: Blue Horizontal Branch Stars in Old, Metal-Rich Stellar Systems

abstract:
  Twenty years ago, Burstein et al. (1984)suggested that strong CN and Hbeta
absorption meant younger ages among globular clusters in the Andromeda galaxy
(M31), unless blue stars above the main-sequence turnoff or on the horizontal
branch were uncommonly prominent. Here we test these suggestions by fitting the
detailed mid-ultraviolet (2280-3120A) and optical (3850-4750A) spectra of one
moderately metal-rich M31 globular cluster, G1. We explore the effects of a
wide range of non-solar temperatures and abundance ratios, by combining a small
set of theoretical stellar spectra like those of Peterson et al. (2001) that
were calculated using extensively updated atomic-line constants. To match the
mid-UV fluxes of G1, we find that hot components with Teff >= 8000K must be
included. We obtain a very good fit with cool and hot blue horizontal branch
(BHB) stars, but less satisfactory fits for blue straggler stars, those hotter
than the main-sequence turnoff.
  The G1 color-magnitude diagram does show cool BHB stars, and the color of its
giant branch supports the metallicity of one-sixth the solar value that we
deduce. The turnoff temperature of the best-fit model is consistent with that
of turnoff stars in galactic globular clusters and the field halo, indicating
G1 is comparably old. Because metal-rich cool BHB and extremely blue HB stars
have now been found within our own Galaxy, we suggest that these hot
horizontal-branch stars be considered in fitting spectra of metal-rich
populations such as the Andromeda globular clusters, to avoid possible
underestimates of their ages. We plan to make the relevant spectral
calculations available as part of our Hubble Treasury Program.


title: VLBI imaging of the RS CVn binary star system HR 5110

abstract:
  We present VLBI images of the RS CVn binary star HR 5110 (=BH CVn; HD
118216), obtained from observations made at 8.4 GHz on 1994 May 29/30 in
support of the NASA/Stanford Gravity Probe B project. Our images show an
emission region with a core-halo morphology. The core was 0.39 +/- 0.09 mas
(FWHM) in size, or 66% +/- 20% of the 0.6 +/- 0.1 mas diameter of the
chromospherically active K subgiant star in the binary system. The halo was
1.95 +/- 0.22 mas (FWHM) in size, or 1.8 +/- 0.2 times the 1.1 +/- 0.1 mas
separation of the centers of the K and F stars. The core increased
significantly in brightness over the course of the observations and seems to
have been the site of flare activity that generated an increase in the total
flux density of ~200% in 12 hours. The fractional circular polarization
simultaneously decreased from ~10% to 2.5%.


title: The Extinction and Distance of Maffei 1

abstract:
  We have obtained low- and high-resolution spectra of the core of the
highly-reddened elliptical galaxy Maffei 1. From these data, we have obtained
the first measurement of the Mg2 index, and have measured the velocity
dispersion and radial velocity with improved accuracy. To evaluate the
extinction, a correlation between the Mg2 index and effective V-I colour has
been established for elliptical galaxies. Using a new method for correcting for
effective wavelength shifts, we find A_V = 4.67 +/- 0.19 mag, which is lower by
0.4 mag than previously thought. To establish the distance, the Fundamental
Plane for elliptical galaxies has been constructed in I. The velocity
dispersion of Maffei 1, measured to be 186.8 +/- 7.4 km/s, in combination with
modern wide-field photometry in I, leads to a distance of 2.92 +/- 0.37 Mpc.
The Dn-sigma relation, which is independently calibrated, gives 3.08 +/- 0.85
Mpc and 3.23 +/- 0.67 Mpc from photometry in B and K`, respectively. The
weighted mean of the three estimates is 3.01 +/- 0.30 Mpc. The distance and
luminosity make Maffei 1 the nearest giant elliptical galaxy. The radial
velocity of Maffei 1 is +66.4 +/- 5.0 km/s, significantly higher than the
accepted value of -10 km/s. The Hubble distance corresponding to the mean
velocity of Maffei 1, Maffei 2 and IC342 is 3.5 Mpc. Thus, it is unlikely that
Maffei 1 has had any influence on Local Group dynamics.


title: The Early Ultraviolet Evolution of the ONeMg Nova V382 Velorum 1999

abstract:
  We present a multiwavelength study of the ONeMg Galactic nova V382 Velorum
1999 using HST/STIS and FUSE ultraviolet spectra and comparisons with published
groundbased optical spectra. We find a close match to the basic phenomenology
of another well-studied ONeMg nova, V1974 Cygni (Nova Cygni 1992), in
particular to the spectral development through the start of the nebular phase.
Following an ``iron curtain'' phase, the nova proceeded through a stage of P
Cygni line profiles on all important resonance lines, as in many ONeMg novae
and unlike the CO class. Emergent emission lines displayed considerable
structure, as seen in V1974 Cyg, indicating fragmentation of the ejecta at the
earliest stages of the outburst. Analysis and modeling of our ultraviolet
spectra suggest that 4 - 5 $\times$ 10$^{-4}$M$_{\odot}$ of material was
ejected and that the distance to the nova is $\simeq 2.5$ kpc. Relative to
solar values, we find the following abundances: He = 1.0, C = 0.6$\pm$0.3, N =
17$\pm$4, O = 3.4$\pm$0.3, Ne = 17$\pm$3, Mg = 2.6$\pm$0.1, Al = 21$\pm$2, and
Si = 0.5$\pm$0.3. Finally, we briefly draw comparisons with Nova LMC 2000,
another ONeMg nova, for which similar data were obtained with HST and FUSE.


title:
Self-Consistency and Calibration of Cluster Number Count Surveys for
  Dark Energy

abstract:
  Cluster number counts offer sensitive probes of the dark energy if and only
if the_evolution_ of the cluster mass versus observable relation(s) is well
calibrated. We investigate the potential for internal calibration by demanding
consistency in the counts as a function of the observable. In the context of a
constant dark energy equation of state, known initial fluctuation amplitude
expected from the CMB, universal underlying mass function, and an idealized
selection, we find that the ambiguity from the normalization of the
mass-observable relationships, or an extrapolation of external mass-observable
determinations from higher masses, can be largely eliminated with a
sufficiently deep survey, even allowing for an arbitrary evolution. More
generally, number counts as a function of both the redshift and the observable
enable strong consistency tests on assumptions made in modelling the
mass-observable relations and cosmology.