title:
An interferometric-spectroscopic orbit for the binary HD 195987: Testing
  models of stellar evolution for metal-poor stars

abstract:
  We report spectroscopic and interferometric observations of the moderately
metal-poor double-lined binary system HD 195987, with an orbital period of 57.3
days. By combining our radial-velocity and visibility measurements we determine
the orbital elements and derive absolute masses for the components of M(A) =
0.844 +/- 0.018 Msun and M(B) = 0.6650 +/- 0.0079 Msun, with relative errors of
2% and 1%, respectively. We also determine the orbital parallax, pi(orb) =
46.08 +/- 0.27 mas, corresponding to a distance of 21.70 +/- 0.13 pc. The
parallax and the measured brightness difference between the stars in V, H, and
K yield the component absolute magnitudes in those bands. We also estimate the
effective temperatures of the stars as Teff(A) = 5200 +/- 100 K and Teff(B) =
4200 +/- 200 K. Together with detailed chemical abundance analyses from the
literature giving [Fe/H] approximately -0.5 (corrected for binarity) and
[alpha/Fe] = +0.36, we use these physical properties to test current models of
stellar evolution for metal-poor stars. Among the four that we considered, we
find that no single model fits all observed properties at the measured
composition, although we identify the assumptions in each one that account for
the discrepancy and we conclude that a model with the proper combination of
assumptions should be able to reproduce all the radiative properties. The
indications from the isochrone fits and the pattern of enhancement of the
metals in HD 195987 are consistent with this being a thick disk object, with an
age of 10-12 Gyr.


title:
Intrinsic/Extrinsic Density-Ellipticity Correlations and Galaxy-Galaxy
  Lensing

abstract:
  We compute both extrinsic (lensing) and intrinsic contributions to the
(galaxy-)density-ellipticity correlation function, the latter done using
current analytic theories of tidal alignment. The gravitational lensing
contribution has two components: one is analogous to galaxy-galaxy lensing and
the other arises from magnification bias -- that gravitational lensing induces
a modulation of the galaxy density as well as ellipticity. On the other hand,
the intrinsic alignment contribution vanishes, even after taking into account
source clustering corrections, which suggests the density-ellipticity
correlation might be an interesting diagnostic in differentiating between
intrinsic and extrinsic alignments. {\it However}, an important assumption,
commonly adopted by current analytic alignment theories, is the Gaussianity of
the tidal field. Inevitable non-Gaussian fluctuations from gravitational
instability induces a non-zero intrinsic density-ellipticity correlation, which
we estimate. We also argue that non-Gaussian contributions to the intrinsic
{\it ellipticity-ellipticity} correlation are often non-negligible. This leads
to a linear rather than, as is commonly assumed, quadratic scaling with the
power spectrum on sufficiently large scales. Finally, we estimate the
contribution of intrinsic alignment to low redshift galaxy-galaxy lensing
measurements (e.g. SDSS), due to the partial overlap between foreground and
background galaxies: the intrinsic contamination is about 10 - 30 % at 10'.
Uncertainties in this estimate are discussed.


title:
The KPNO/Deeprange Distant Cluster Survey: I. The Catalog & the Space
  Density of Intermediate Redshift Clusters

abstract:
  We have conducted an automated search for galaxy clusters within a contiguous
16 square degree I-band survey in the north Galactic hemisphere. A matched
filter detection algorithm identifies 444 cluster candidates in the range 0.2
<= z <= 1.2. The full catalog is presented along with the results from a
follow-up spectroscopic survey. The estimated redshift distribution of the
cluster candidates is consistent with a constant comoving density over the
range 0.2 <= z_est <= 0.8. A decline in the cluster space density by more than
a factor of 3 over this redshift range is rejected at >99.9% confidence level.
We find that the space density of Lambda_CL >= 40 clusters in our survey lies
in the range (1.6 - 1.8) x 10^{-5} h_{75}^{3} Mpc^{-3}, ~1.5 times higher than
the local distribution of comparably rich Abell RC >= 0 clusters. The Lambda_CL
distribution is consistent with a power-law. The discrepancy between the space
density of Abell clusters and the clusters in this survey declines quickly as
Lambda_CL increases, suggesting that the difference at lower richness is due to
significant incompleteness in the Abell catalog. A percolation analysis reveals
that 10 - 20% of the spectroscopically confirmed distant clusters are linked
into superclusters at overdensities between 10 < {\delta\rho \over \rho} < 50,
similar to what is seen in the local cluster distribution. This suggests that
there has been little evolution of the cluster-cluster correlation length for z
<= 0.5.


title: A Dynamical Analysis of the 47 UMa Planetary System

abstract:
  The mass and period ratios of the two planets orbiting 47 UMa suggest a
possible kinship to the Jupiter-Saturn pair in our solar system. We explore the
current dynamical state of the 47 UMa system with numerical integrations, and
compare the results with analytic secular theory. We find that the planets in
the system are likely participating in a secular resonance in which the
difference in the longitudes of pericenter librates around zero. Alternately,
it is possible that the system is participating in the 7:3 mean motion
resonance. We show that stability considerations restrict the mutual
inclination between the two planets to 40 degrees or less, and that this result
is relatively insensitive to the total mass of the two planets. We present
hydrodynamical simulations which measure the torques exerted on the planets by
a hypothesized external protoplanetary disk. We show that planetary migration
in response to torques from the disk may have led to capture of the system into
a 7:3 mean-motion resonance, although it is unclear how the eccentricities of
the planets would have been damped after capture occured. We show that
Earth-mass planets can survive for long periods in some regions of the
habitable zone of the nominal co-planar system. A set of planetary accretion
calculations, however, shows that it is unlikely that large terrestrial planets
can form in the 47 UMa habitable zone.


title: Workshop Summary: The Dynamics, Structure and History of Galaxies

abstract:
  In July/August last year, a group of 50 galactic astronomers convened at Dunk
Island, Australia to celebrate Prof. Ken Freeman's 60th birthday. The
overarching theme of the meeting reflected Ken's wish to understand ``the chain
of events that occurred during the formation of the Galaxy", to quote from his
Annual Reviews article in 1987. The workshop was divided into four parts:
galaxy structure and dynamics, haloes and environments, HI and dark matter,
galaxy formation and evolution.


title:
High Resolution CO and H2 Molecular Line Imaging of a Cometary Globule
  in the Helix Nebula

abstract:
  We report high resolution imaging of a prominent cometary globule in the
Helix nebula in the CO J=1-0 (2.6 mm) and H2 v=1-0 S(1) (2.12 micron) lines.
The observations confirm that globules consist of dense condensations of
molecular gas embedded in the ionized nebula. The head of the globule is seen
as a peak in the CO emission with an extremely narrow line width (0.5 km/s) and
is outlined by a limb-brightened surface of H2 emission facing the central star
and lying within the photo-ionized halo. The emission from both molecular
species extends into the tail region. The presence of this extended molecular
emission provides new constraints on the structure of the tails, and on the
origin and evolution of the globules.


title: Testing the Halo Model Against the SDSS Photometric Survey

abstract:
  We present halo model predictions for the expected angular clustering and
associated errors from the completed Sloan Digital Sky Survey (SDSS)
photometric galaxy sample. These results are used to constrain halo model
parameters under the assumption of a fixed LCDM cosmology using standard Fisher
matrix techniques. Given the ability of the five-color SDSS photometry to
separate galaxies into sub-populations by intrinsic color, we also use
extensions of the standard halo model formalism to calculate the expected
clustering of red and blue galaxy sub-populations as a further test of the
galaxy evolution included in the semi-analytic methods for populating dark
matter halos with galaxies. The extremely small sample variance and Poisson
errors from the completed SDSS survey should result in very impressive
constraints (~1-10%) on the halo model parameters for a simple
magnitude-limited sample and should provide an extremely useful check on the
behavior of current and future N-body simulations and semi-analytic techniques.
We also show that similar constraints are possible using a narrow selection
function, as would be possible using photometric redshifts, without making
linear assumptions regarding the evolution of the underlying power spectra. In
both cases, we explore the effects of uncertainty in the selection function on
the resulting constraints and the degeneracies between various combinations of
parameters.


title: Excursions into the Evolution of Early-Type Galaxies in Clusters

abstract:
  Recent observations have revealed that early-type galaxies (ETG) in clusters
comprise an old galaxy population that is evolving passively. We review some
recent observations from the ground and from HST that show that ETG have
undergone a significant amount of luminosity evolution. This evolution is
traced by two projections of the fundamental plane (FP): the size-magnitude
relation (SMR) and the color-magnitude relation (CMR). We will briefly discuss
the relevance of all these results in the context of the universality of the
IMF.


title: Submillimeter Dust Continuum Studies of Low and High Mass Star Formation

abstract:
  Studying the physical environments of low mass and high mass cores using dust
continuum emission provides important observational constraints on theoretical
models of star formation. The motivation and procedure for modeling dust
continuum emission is reviewed and the results of recent surveys towards low
mass and high mass star forming regions are compared.


title: Domain Walls as Dark Energy

abstract:
  The possibility that the energy density of the Universe is dominated by a
network of low-tension domain walls provides an alternative to the commonly
discussed cosmological constant and scalar-field quintessence models of dark
energy. We quantify the lower bound on the number density of the domain walls
that follows from the observed near-isotropy of the cosmic microwave background
radiation. This bound can be satisfied by a strongly frustrated domain wall
network. No fine-tuning of the parameters of the underlying field theory model
is required. We briefly outline the observational consequences of this model.


title:
First spectroscopic evidence for carbon stars outside the Local Group:
  properties of a massive star cluster in NGC 7252

abstract:
  We present near-IR spectroscopy of the massive intermediate age star cluster
W3 in the merger remnant galaxy NGC 7252, obtained with the NTT telescope. This
cluster has an age when the integrated near-IR properties of a stellar
population are dominated by the cool and luminous AGB stars. We compare the
data with instantaneous curst model predictions from new evolutionary synthesis
models that include: (1) the computation of the evolution through the TP-AGB
for low- and intermediate-massive stars, with the initial mass and metallicity
dependent formation of carbon stars; (2) spectroscopic data from a new stellar
library in which differences betwenn static giants, vriable O-rich TPAGB stars
and carbon stars are accounted for. The comparison of the data to the models
clearly shows that carbon stars are present: for the first time, carbon star
spectral features are thus detected directly outside the Local Group (abriged)


title:
The modelling of intermediate-age stellar populations: I- near-infrared
  properties

abstract:
  In this paper, we discuss how the integrated properties of intermediate-age
single burst population, especially in the near-infrared, behave as a function
of age and metallicity. Our models take into account all stellar evolutionary
phases that affect the evolution of the integrated optical and near-infrared
spectrum of such a population. Particular care was dedicated to the Asymptotic
Giant Brach stars, which can be dominant at near-infrared wavelengths. First we
present new synthetic model that takes into account the relevant physical
processes that control the evolution through the thermally pulsing AGB. In the
isochrone presented in this paper the lifetime and the nature of the AGB stars
are established as consequences of the interplay between the physical processes
that control the AGB star evolution. The contribution of these stars to the
integrated light of the population is thus obtained in a consistent way. We
optimize our models by using a new stellar library that explicitly takes into
account the spectral features thar characterize only AGB stars in comparison to
other cool and luminous stars (abriged)


title:
A Nulling Wide Field Imager for Exoplanets Detection and General
  Astrophysics

abstract:
  We present a solution to obtain a high-resolution image of a wide field with
the central source removed by destructive interference. The wide-field image is
created by aperture synthesis with a rotating sparse array of telescopes in
space. Nulling of the central source is achieved using a phase-mask
coronagraph. The full (u,v) plane coverage delivered by the 60m, six 3-meter
telescope array is particularly well-suited for the detection and
characterization of exoplanets in the infrared (DARWIN and Terrestrial Planet
Finder (TPF) missions) as well as for other generic science observations.
Detection (S/N=10) of an Earth-like planet is achieved in less than 10 hours
with a 1 micron bandwidth at 10 micron.


title:
A collimated flow driven by radiative pressure from the nucleus of
  quasar Q~1511+091

abstract:
  High velocity outflows from quasars are revealed by the absorption signatures
they produce in the spectrum of the quasar. Clues on the nature and origin of
these flows are important for our understanding of the dynamics of gas in the
central regions of the Active Galactic Nucleus (AGNs) but also of the metal
enrichment of the intergalactic space. Line radiation pressure has often been
suggested to be an important process in driving these outflows, however no
convincing evidence has been given so far. Here we report observation of a
highly structured flow, toward Q~1511+091, where the velocity separations
between distinct components are similar to O VI, N V and C IV doublet
splittings with some of the profiles matching perfectly. This strongly favors
the idea that the absorbing clumps originate at similar physical location and
are driven by radiative acceleration due to resonance lines. The complex
absorption can be understood if the flow is highly collimated so that the
different optically thick clouds are aligned and cover the same region of the
background source. One component shows saturated H I Lyman series lines
together with absorptions from excited levels from C II and Si II but covers
only 40% of the source of continuum. The fact that clouds cover only part of
the small continuum source implies that the flow is located very close to it.


title:
Discovery of Extremely Large-Amplitude Quasi-Periodic Photometric
  Variability in WC9-Type Wolf-Rayet Binary, WR 104

abstract:
  We discovered that the Wolf-Rayet (WR)+OB star binary, WR 104, renowned for
its associated "dusty pinwheel nebula" recently spatially resolved with
infrared interferometry, exhibits strong quasi-periodic optical variations with
a full amplitude of 2.7 mag. Such a large-amplitude, continuous variation has
been unprecedented in a WR star. The optical quasi-period (~241 d) is in almost
perfect agreement with the interferometric period (243.5+/-3 d). The remarkable
agreement of the dominant period in optical variability with the orbital period
supports that the strongly varying dust obscuration is physically related to
the binary motion, rather than sporadic dust-forming episodes. Considering the
low orbital inclination (11+/-7 deg) and the nearly circular orbit inferred
from the interferometric observations, the strongly variable line-of-sight
extinction suggests that the highly structured extinction can be being formed
via an ejection of dust in the direction of the binary rotation axis. Another
viable explanation is that the three-dimensional structure of the shock front,
itself is the obscuring body. Depending on the geometry, the dusty shock front
near the conjunction phase of the binary can completely obscure the inner
WR-star wind and the OB star, which can explain the amplitude of optical fading
and the past observation of remarkable spectral variation.


title:
Possible Formation Scenario of the Quark Star of Maximum Mass around 0.7
  solar mass

abstract:
  If there exists the quark star of maximum mass $\sim 0.7\sol$ as suggested by
recent Chandra observations, we show that the general relativistic collapse of
a neutron star of mass greater than the maximum mass of the neutron star with
angular momentum parameter $q\equiv cJ/GM^2 > 1$ may lead to such a strange
star. Here $J$ and $M$ are the angular momentum and the gravitational mass of
the neutron star, respectively. Under the cosmic censorship hypothesis, such a
star can not be a black hole directly. The jet formed in the soft core might
explode the outer envelope and leave the quark star of mass $\sim 0.7\sol$. The
remnant quark star has $\lesssim 10^{53}$ erg rotational energy so that the
formation of the quark star may be related to the central engine of GRBs. The
detailed numerical simulations are urgent to confirm or refute this scenario.


title: On the Nature of MeV-blazars

abstract:
  Broad-band spectra of the FSRQ (flat-spectrum-radio quasars) detected in the
high energy gamma-ray band imply that there may be two types of such objects:
those with steep gamma-ray spectra, hereafter called MeV-blazars, and those
with flat gamma-ray spectra, GeV-blazars. We demonstrate that this difference
can be explained in the context of the ERC (external-radiation-Compton) model
using the same electron injection function. A satisfactory unification is
reachable, provided that: (a) spectra of GeV-blazars are produced by internal
shocks formed at the distances where cooling of relativistic electrons in a jet
is dominated by Comptonization of broad emission lines, whereas spectra of
MeV-blazars are produced at the distances where cooling of relativistic
electrons is dominated by Comptonization of near-IR radiation from hot dust;
(b) electrons are accelerated via a two step process and their injection
function takes the form of a double power-law, with the break corresponding to
the threshold energy for the diffusive shock acceleration. Direct predictions
of our model are that, on average, variability time scales of the MeV-blazars
should be longer than variability time scales of the GeV-blazars, and that both
types of the blazar phenomenon can appear in the same object.


title: Models of infrared spectra of Sakurai's Object (V4334 Sgr) in 1997

abstract:
  Theoretical spectral energy distributions computed for a grid of
hydrogen-deficient and carbon-rich model atmospheres have been compared with
the observed infrared (1--2.5 $\mu$m) spectra of V4334 Sgr (Sakurai's Object)
on 1997 April 21 and July 13. The comparison yields an effective temperature of
\Tef = 5500 $\pm$ 200 K for the April date and \Tef = 5250 $\pm$ 200 K for
July. The observed spectra are well fitted by Asplund et al. (1999) abundances,
except that the carbon abundance is higher by 0.3 dex. Hot dust produces
significant excess continuum at the long wavelength ends of the 1997 spectra.
\keywords{Stars: individual: V4334 Sgr (Sakurai's Object) -- Stars: AGB and
post-AGB evolution -- Stars: model atmospheres -- Stars: energy distributions
-- Stars: effective temperatures}


title: Origin of the X-Ray Background and AGN Unification: New Perspectives

abstract:
  We critically review the basic assumptions of the standard model for the
synthesis of the XRB in the light of new data from ultradeep surveys by Chandra
and XMM, resolving major parts of it. Important constraints come in particular
from the observed z-distributions of faint hard X-ray sources -- showing large
excesses at redshifts (z~0.8) much lower than expected by the synthesis models
-- and from their X/optical/IR SEDs combined with the IR counts of type-II
AGNs. Our analysis, although supporting the general scheme which interprets the
XRB as due to absorbed AGNs with broad N_H distributions, requires major
revision of the other postulate of the XRB synthesis models: the AGN
unification. We argue that the unification scheme based on a simple orientation
effect fails at high redshifts, where galaxy activity is induced by strong
interactions and mergers among gas-rich systems. This helps explaining the
observational evidence that type-I and II AGNs follow different evolutionary
patterns, with type-I quasars providing a very biased trace of this activity.
Combined deep X-ray and IR surveys consistently find that the universe has
experienced a violent phase of galaxy activity around z~1, probably related
with the assembly of massive galaxies, involving both SF and obscured AGN
fueling. Roughly 10 to 20% of this activity has involved substantial AGN
emission, this fraction likely reflecting the AGN/starburst duty cycle during
the activation phase.


title: Evidence for Stellar Substructure in the Halo and Outer Disk of M31

abstract:
  We report the discovery of significant stellar substructure in the halo and
outer disk of our nearest large galactic neighbour, M31. Our deep panoramic
survey with the Isaac Newton Telescope Wide Field Camera currently maps out an
area of ~25 square degrees around M31, extending along the semi-major axis to
55 kpc, and is the first to allow an uninterrupted study of the density and
color distribution of individual red giant branch stars across a large fraction
of the halo of an external spiral galaxy. We find evidence for both spatial
density and metallicity (as inferred from colour information) variations, which
are often, but not always, correlated. In addition to the previously reported
giant stellar stream (Ibata 2001b), the data reveal the presence of significant
stellar overdensities at large radii close to the south-western major axis, in
the proximity of the very luminous globular cluster G1, and near the
north-eastern major axis, coinciding with and extending beyond the
previously-known `northern spur'. The most prominent metallicity variations are
found in the southern half of the halo, where two large structures with above
average metallicites are apparent; one of these coincides with the giant
stellar stream while the other corresponds to a much lower-level stellar
enhancement. Our findings contrast with, but do not conflict with, past studies
of the M31 halo and outer disk which have suggested a rather homogeneous
stellar population at large radius: the bulk of our newly-detected substructure
lies in the previously-uncharted far outer regions of the galaxy. We discuss
the possible origin of the substructure observed and the implications it has
for constraining the galaxy assembly process.


title: NGC4258: a jet-dominated low-luminosity AGN?

abstract:
  Low-luminosity AGNs (LLAGNs) are a very important class of sources since they
occupy a significant fraction of local galaxies. Their spectra differ
significantly from the canonical luminous AGNs, most notably by the absence of
the ``big blue bump''. In the present paper, taking a typical
LLAGN--NGC4258--as an example, we investigate the origin of their spectral
emission. The observational data of NGC4258 is extremely abundant, including
water maser emission, putting very strict constraints to its theoretical
models. The infrared (IR) spectrum is well described by a steep power-law form
$f_{\nu}\propto \nu^{-1.4}$, and may extend to the optical/UV band. Up until
now there is no model which can explain such a steep spectrum, and we here
propose a coupled jet plus accretion disk model for NGC4258. The accretion disk
is composed of an inner ADAF (or radiatively inefficient accretion flow) and an
outer standard thin disk. A shock occurs when the accretion flow is ejected out
of the ADAF to form the jet near the black hole, accelerating the electrons
into a power-law energy distribution. The synchrotron and self-Comptonized
emission from these electrons greatly dominates over the underlying accretion
disk and can well explain the spectrum ranging from IR to X-ray bands. The
further propagation of the shocked gas in the jet can explain the flat radio
spectrum of NGC4258. Several predictions of our model are presented for testing
against future observations, and we briefly discuss the application of the
model to other LLAGNs.


title:
Density dependent hadron field theory for neutron stars with antikaon
  condensates

abstract:
  We investigate $K^-$ and $\bar K^0$ condensation in $\beta$-equilibrated
hyperonic matter within a density dependent hadron field theoretical model. In
this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by
the exchange of mesons. Density dependent meson-baryon coupling constants are
obtained from microscopic Dirac Brueckner calculations using Groningen and Bonn
A nucleon-nucleon potential. It is found that the threshold of antikaon
condensation is not only sensitive to the equation of state but also to
antikaon optical potential depth. Only for large values of antikaon optical
potential depth, $K^-$ condensation sets in even in the presence of negatively
charged hyperons. The threshold of $\bar K^0$ condensation is always reached
after $K^-$ condensation. Antikaon condensation makes the equation of state
softer thus resulting in smaller maximum mass stars compared with the case
without any condensate.


title: The unusual pulsation spectrum of the cool ZZ Ceti star HS 0507+0434B

abstract:
  We present the analysis of one week of single-site high-speed CCD photometric
observations of the cool ZZ Ceti star HS 0507+0434B. Ten independent
frequencies are detected in the star's light variations: one singlet and three
nearly-equally spaced triplets. We argue that these triplets are due to
rotationally split modes of spherical degree l=1. This is the first detection
of consistent multiplet structure in the amplitude spectrum of a cool ZZ Ceti
star and it allows us to determine the star's rotation period: 1.70 +/- 0.11 d.
  We report exactly equal frequency, not period, spacings between the detected
mode groups. In addition, certain pairs of modes from the four principal groups
have frequency ratios which are very close to 3:4 or 4:5; while these ratios
are nearly exact (within one part in 10^4), they still lie outside the computed
error bars. We speculate that these relationships between different frequencies
could be caused by resonances. One of the three triplets may not be constant in
amplitude and/or frequency.
  We compare our frequency solution for the combination frequencies (of which
we detected 38) to Wu's (1998, 2001) model thereof. We obtain consistent
results when trying to infer the star's convective thermal time and the
inclination angle of its rotational axis. Theoretical combination-frequency
amplitude spectra also resemble those of the observations well, and direct
theoretical predictions of the observed second-order light-curve distortions
were also reasonably successful assuming the three triplets are due to l=1
modes. Attempts to reproduce the observed combination frequencies adopting all
possible l=2 identifications for the triplets did not provide similarly
consistent results, supporting their identification with l=1.


title:
Similarity of structuring in the range 10^{-5} cm to 10^23 cm hints at a
  baryonic cold dark skeleton of the Universe

abstract:
  The presence of skeletal structures of the same distinctive topology
(cartwheels, tubules, etc.), in the range 10^{-5} - 10^23 cm, and a trend
toward self-similarity of these structures are found. These evidences come from
the electron micrography of dust deposits in tokamak (10^{-6} - 10^{-3}cm), the
images of plasma taken in laboratory electric discharges -- tokamaks,
Z-pinches, plasma focus and vacuum spark (10^{-2} - 10 cm), hail particles
(1-10 cm), the images of tornado (10^3 - 10^5 cm), the Hubble Space Telescope
and Chandra X-Ray Observatory public archives' images (up to 10^23 cm). The
redshift surveys of galaxies and quasars suggests the possibility to draw the
above similarity farther, up to 10^26 cm. The above similarity hints at the
presence of a baryonic cold dark skeleton (BCDS) of the Universe, which -- in
the entire range 10^{-5} - 10^26 cm -- may contain ordinary matter in a fractal
condensed form like that in the above-mentioned dust skeletons and hail
particles. The probable compatibility of the BCDS with the major cosmological
facts (Hubble's expansion and cosmic microwave background) is suggested. Our
former hypotheses (and the respective proof-of-concept studies) for the
probable microscopic mechanisms of skeleton's assembling, chemical composition,
and survivability in ambient hot plasmas are discussed briefly. The respective
major cosmological implication is that the purely gravitational description of
the large-scale structure of the Universe is likely to be appended with a
contribution of quantum electromagnetism, presumably in the form of a skeleton
self-assembled from tubular nanostructures (carbon nanotubes or similar
nanostructures of other chemical elements).


title: Broad-band X-ray measurements of the black hole candidate XTE J1908+094

abstract:
  XTE J1908+094 is an X-ray transient that went into outburst in February 2002.
After two months it reached a 2-250 keV peak flux of 1 to 2 X 10-8 erg/s/cm2.
Circumstantial evidence points to an accreting galactic black hole as the
origin of the the X-radiation: pulsations nor thermonuclear flashes were
detected that would identify a neutron star and the spectrum was unusually hard
for a neutron star at the outburst onset. We report on BeppoSAX and RXTE All
Sky Monitor observations of the broad-band spectrum of XTE J1908+094. The
spectrum is consistent with a model consisting of a Comptonization component by
a ~40 keV plasma (between 2 and 60 keV this component can be approximated by a
power law with a photon index of 1.9 to 2.1), a multicolor accretion disk
blackbody component with a temperature just below 1 keV and a broad emission
line at about 6 keV. The spectrum is heavily absorbed by cold interstellar
matter with an equivalent hydrogen column density of 2.5 X 10+22 cm-2, which
makes it difficult to study the black body component in detail. The black body
component exhibits strong evolution about 6 weeks into the outburst. Two weeks
later this is followed by a swift decay of the power law component. The
broadness of the 6 keV feature may be due to relativistic broadening or Compton
scattering of a narrow Fe-K line.


title:
A graphical selection method for parametric models in noisy
  inhomogeneous regression

abstract:
  A common problem in physics is to fit regression data by a parametric class
of functions, and to decide whether a certain functional form allows for a good
fit of the data. Common goodness of fit methods are based on the calculation of
the distribution of certain statistical quantities under the assumption that
the model under consideration {\it holds true}. This proceeding bears
methodological flaws, e.g. a good ``fit'' - albeit the model is wrong - might
be due to over-fitting, or to the fact that the chosen statistical criterion is
not powerful enough against the present particular deviation between model and
true regression function. This causes particular difficulties when models with
different numbers of parameters are to be compared. Therefore the number of
parameters is often penalised additionally. We provide a methodology which
circumvents these problems to some extent. It is based on the consideration of
the error distribution of the goodness of fit criterion under a broad range of
possible models - and not only under the assumption that a given model holds
true. We present a graphical method to decide for the most evident model from a
range of parametric models of the data. The method allows to quantify
statistical evidence {\it for} the model (up to some distance between model and
true regression function) and not only {\it absence of evidence} against, as
common goodness of fit methods do. Finally we apply our method to the problem
of recovering the luminosity density of the Milky Way from a de-reddened {\it
COBE/DIRBE} L-band map. We present statistical evidence for flaring of the
stellar disc inside the solar circle.


title: EROS 2 proper motion survey: Constraints on the halo white dwarfs

abstract:
  We are conducting a 377-square-degree proper motion survey in the ~V and I
bands in order to determine the cool white dwarf contribution to the Galactic
dark matter. Using the 250 square degrees for which we possess three epochs,
and applying selection criteria designed to isolate halo-type objects, we find
no candidates in a 5500 pc^3 effective volume for old, fast M_V=17 white
dwarfs. We check the detection efficiency by cross-matching our catalogue with
Luyten's NLTT catalogue.
  The halo white dwarf contribution cannot exceed 5% (95% C.L.) for objects
with M_V=17 and 1<V-I<1.5. The same conclusion applies to a 14Gyr halo composed
of white dwarfs with hydrogen atmosphere, as modeled by Chabrier (99).


title: Instability of the Gravitational N-Body Problem in the Large-N Limit

abstract:
  We use a systolic N-body algorithm to evaluate the linear stability of the
gravitational N-body problem for N up to 1.3 x 10^5, two orders of magnitude
greater than in previous experiments. For the first time, a clear ~ln
N-dependence of the perturbation growth rate is seen. The e-folding time for N
= 10^5 is roughly 1/20 of a crossing time.


title: A Chandra Observation of the Luminous NLS1 1H 0707-495

abstract:
  We present preliminary results from a long Chandra HETG observation of the
luminous Narrow-line Seyfert 1 galaxy 1H 0707-495. We find a complex X-ray
spectrum comprised of a two-component continuum with superimposed emission and
absorption lines. The short time scale X-ray variability is different than
observed in other AGN: the soft X-rays vary markedly less than the hard X-rays.
This behavior is similar to that of high-state Galactic black holes. We also
investigated the long time scale variability, and discovered an apparent
bimodal flux distribution. We postulate that the bimodality is the signature of
the radiation pressure instability, and note that this instability may be
expected in luminous NLS1s.


title: Statistical Investigations of 1315 Radio Pulsars

abstract:
  In this paper we have used the data of 1315 pulsars (Guseinov et al. 2002)
for statistical analysis and showed the changes in pulsar parameters since the
appearance of Taylor et al. (1996) catalog. Here we present the space
distribution of pulsars, dispersion measures, distances from the galactic plane
and from the Sun, electron density, luminosity distributions at 400 and 1400
MHz, the relations between luminosities of pulsars at 400 and 1400 MHz and the
dependence of luminosity on age and on magnetic field. We also present the
updated P-Pdot diagram.


title: Single-dish monitoring of circumstellar water masers

abstract:
  We present an overview of the long-term water maser monitoring program of a
sample of late-type stars, carried out with the Medicina 32-m and Effelsberg
100-m telescopes, and describe the results in some detail. The role the SRT
(Sardinia Radio Telescope) could play in this program is outlined.


title:
The Explosive Yields Produced by the First Generation of Core Collapse
  Supernovae and the Chemical Composition of Extremely Metal Poor Stars

abstract:
  We present a detailed comparison between an extended set of elemental
abundances observed in some of the most metal poor stars presently known and
the ejecta produced by a generation of primordial core collapse supernovae. We
used five stars which form our initial database and define a "template" ultra
metal poor star which is then compared to the theoretical predictions. Our main
findings are as follows: a) the fit to [Si/Mg] and [Ca/Mg] of these very metal
poor stars seems to favor the presence of a rather large C abundance at the end
of the central He burning; in a classical scenario in which the border of the
convective core is strictly determined by the Schwarzschild criterion, such a
large C abundance would imply a rather low C12(alpha,gamma)O16 reaction rate;
b) a low C abundance left by the central He burning would imply a low [Al/Mg]
(<-1.2 dex) independently on the initial mass of the exploding star while a
rather large C abundance would produce such a low [Al/Mg] only for the most
massive stellar model; c) at variance with current beliefs that it is difficult
to interpret the observed overabundance of [Co/Fe], we find that a mildly large
C abundance in the He exhausted core (well within the present range of
uncertainty) easily and naturally allows a very good fit to [Co/Fe]; d) our
yields allow a reasonable fit to 8 out of the 11 available elemental
abundances; e) within the present grid of models it is not possible to find a
good match of the remaining three elements, Ti, Cr and Ni (even for an
arbitrary choice of the mass cut); f) the adoption of other yields available in
the literature does not improve the fit; g) since no mass in our grid provides
a satisfactory fit to these three elements, even an arbitrary choice of the
initial mass function would not improve their fit.


title: The Chemical Yields Produced by Zero Metal Massive Stars

abstract:
  In this review we compare the three existing sets of theoretical yields of
zero metal massive stars available in the literature. We also show how each of
these three different sets of yields fits the element abundance ratios observed
in the extremely metal poor star CD 38245. We find that, at present, no
theoretical set of yields of zero metal massive stars is able to satisfactorily
reproduce the elemental ratios [X/Fe] of this star.


title: A model independent approach to the dark energy equation of state

abstract:
  The consensus of opinion in cosmology is that the Universe is currently
undergoing a period of accelerated expansion. With current and proposed high
precision experiments it offers the hope of being able to discriminate between
the two competing models that are being suggested to explain the observations,
namely a cosmological constant or a time dependent `Quintessence' model. The
latter suffers from a plethora of scalar field potentials all leading to
similar late time behaviour of the universe, hence to a lack of predictability.
In this paper, we develop a model independent approach which simply involves
parameterizing the dark energy equation of state in terms of known observables.
This allows to analyse the impact dark energy has had on cosmology without the
need to refer to particular scalar field models and opens up the possibility
that future experiments will be able to constrain the dark energy equation of
state in a model independent manner.


title: Perturbations growth and bias during acceleration

abstract:
  In most models of dark energy the structure formation stops when the
accelerated expansion begins. In contrast, we show that the coupling of dark
energy to dark matter may induce the growth of perturbations even in the
accelerated regime. In particular, we show that this occurs in the models
proposed to solve the cosmic coincidence problem, in which the ratio of dark
energy to dark matter is constant. Moreover, if the dark energy couples only to
dark matter and not to baryons, as requested by the constraints imposed by
local gravity measurements, the baryon fluctuations develop a constant,
scale-independent, large-scale bias which is in principle directly observable.


title:
Understanding the Results of Galaxy-Galaxy Lensing using Galaxy-Mass
  Correlation in Numerical Simulations

abstract:
  McKay et al. (2002) have recently used measurements of weak galaxy-galaxy
lensing in the Sloan Digital Sky Survey to estimate the cross correlation
between galaxies and the projected dark matter density field. They derive a
relation between aperture mass within a radius of $260\kpch$, $M_{260}$, and
lens galaxy luminosity, that does not depend on galaxy luminosity, type or
environment. In this paper, we study the cross-correlation between galaxies and
dark matter using galaxy catalogs constructed from a high-resolution N-body
simulation of a $\Lambda$CDM Universe. We show that our simulations reproduce
the McKay et al. results reasonably well. In the simulation, $M_{260}$ is
approximately equal to the halo virial mass for $L_*$ galaxies. $M_{260}$
overestimates the virial mass for fainter galaxies and underestimates it for
brighter galaxies. We use the simulations to show that under certain
circumstances the halo virial mass may be recovered by fitting an NFW profile
to the projected galaxy-mass correlation function. If we apply our method to
the observations, we find that $L_*$ galaxies typically reside in halos of
$\sim 2\times 10^{12} h^{-1} \msun$, consistent with halo masses estimated from
the observed Tully-Fisher relation. In the simulations, the halo virial mass
scales with galaxy luminosity as $L^{1.5}$ for central galaxies in halos and
for galaxies in low-density regions. For satellite galaxies, and for galaxies
in high-density regions, there is no simple relation between galaxy luminosity
and halo mass and care must be exercised when interpreting the lensing results.


title: EVN observations of 6.7 GHz methanol masers from Medicina survey

abstract:
  We report VLBI observations of methanol masers in the brightest 5(1)-6(0) A+
transition at 6.7 GHz in NGC 281W, 18151-1208 and 19388+2357. Using the fringe
rate method absolute positions were obtained for all observed sources. A linear
ordered structure with a velocity gradient was revealed in NGC 281W. Under
assumption that such structure is an edge-on Keplerian disk around the central
object with a mass of 30Msun located at a distance of 3.5 kpc from the Sun, we
estimated that methanol masers are situated at the distance about 400 a.u. from
the center of the disk. A second epoch of observations was reported for L1206,
GL2789 and 20062+3550. The upper limits on the relative motions of maser spots
are estimated to be 4.7 km/s and 28 km/s for L1206 and GL2789 respectively.


title: A Gamma-Ray Burst Trigger Toolkit

abstract:
  (Abbreviated) The detection rate of a GRB detector can be increased by using
a count rate trigger with many accumulation times Dt and energy bands DE, but
the nominal sensitivity is less important than how much fainter a burst could
be at the detection threshold as Dt and DE are changed. Predictions of the
detection rate depend on the assumed burst population, which can be wildly in
error. I base the fiducial rate on the BATSE observations: 550 bursts per sky
above a peak flux of 0.3 ph/cm^2/s averaged over Dt=1.024s and DE=50-300 keV. I
find that triggering on any value of Dt decreases the average threshold peak
flux on the 1.024s timescale by a factor of 0.6. Extending DE to lower energies
includes the large flux of the X-ray background, increasing the background
count rate; a low energy DE is advantageous only for very soft bursts. Whether
a large fraction of the population of bright bursts is soft is disputed; the
new population of X-ray Flashes is soft but relatively faint.


title: On the XMM-Newton spectra of soft X-ray selected QSOs

abstract:
  We study the XMM-Newton spectra of a sample of 32 soft X-ray selected QSOs.
  Our goal is to check, using the spectra of moderate redshift (z~1.5), faint
  (f (0.2-8 keV) > 5x10^-15 cgs) broad-line QSOs, previous claims for either
significant intrinsic absorption or spectral hardening at high energies.
  We derive hardness ratios for all sources and furthermore we perform spectral
fits for the 11 brighter sources. The majority of sources have steep spectra
  (photon index >1.9). We find a few QSOs with large amounts of intrinsic
absorption, as high as N_H~10^23 cm-2. We find no strong evidence for spectral
hardening above 2 keV. The coadded QSO spectrum is well described by a single
power-law with photon index of ~1.9, demonstrating that, on average, any
effects of absorption are not important. This suggests that the discrepancy
between the X-ray background and the (soft X-ray selected) QSO spectrum holds
well at the faint fluxes probed here.


title:
Simultaneous single-pulse observations of radio pulsars: II. Orthogonal
  polarization modes in PSR B1133+16

abstract:
  In this paper, we present a study of orthogonal polarization modes in the
radio emission of PSR B1133+16, conducted within the frame of simultaneous,
multi-frequency, single-pulse observations. Simultaneously observing at two
frequencies (1.41 GHz and 4.85 GHz) provides the means to study the bandwidth
of polarization features such as the polarization position angle. We find two
main results. First, that there is a high degree of correlation between the
polarization modes at the two frequencies. Secondly, the modes occur more
equally and the fractional linear polarization decreases towards higher
frequencies. We discuss this frequency evolution and propose propagation
effects in the pulsar magnetosphere as its origin.


title: Radio Observations of GRB Afterglows

abstract:
  Since 1997 the afterglow of gamma-ray bursting sources (GRBs) has
occasionally been detected in the radio, as well in other wavelengths bands. In
particular, the interesting and unusual gamma-ray burst GRB980425, thought to
be related to the radio supernova SN1998bw, is a possible link between the two
classes of objects. Analyzing the extensive radio emission data avaliable for
SN1998bw, one can describe its time evolution within the well established
framework available for the analysis of radio emission from supernovae. This
then allows relatively detailed description of a number of physical properties
of the object. The radio emission can best be explained as the interaction of a
mildly relativistic shock with a dense preexplosion stellar wind-established
circumstellar medium (CSM) that is highly structured both azimuthally, in
clumps or filaments, and radially, with observed density enhancements. Because
of its unusual characteristics for a Type Ib/c supernova, the relation of
SN1998bw to GRB980425 is strengthened and suggests that at least some classes
of GRBs originate in supernova (SN) massive star explosions. Thus, employing
the formalism for describing the radio emission from supernovae (SNe) and
following the link through SN1998bw/GRB980425, it is possible to model the
gross properties of the radio and optical/infrared (OIR) emission from the
half-dozen GRBs with extensive radio observations. From this we conclude that
at least some members of the ``slow-soft'' class of GRBs can be attributed to
the explosion of a massive star in a dense, highly structured CSM that was
presumably established by the preexplosion stellar system.


title: Review of X-Ray Bursters in the Galactic Center Region

abstract:
  Results of observations of X-ray bursters in the Galactic Center region
carried out with the RXTE observatory and the ART-P telescope on board GRANAT
are presented. Eight X-ray bursters (A1742-294, SLX1744-299/300, GX3+1,
GX354-0, SLX1732-304, 4U1724-307, KS1731-260) were revealed in this region
during five series of observations which were performed with the ART-P
telescope in 1990-1992 and more than 100 type I X-ray bursts from these sources
were observed. For each of the sources we investigated in detail the recurrence
times between bursts, the bursts time profiles and their dependence on the
bursts flux, the spectral evolution of sources emission in the persistent state
and during the bursts. Two bursters (SLX1732-304, 4U1724-307) located in the
globular clusters Terzan 1 and 2, were investigated using the RXTE data as
well.


title:
Warps and correlations with intrinsic parameters of galaxies in the
  visible and radio

abstract:
  From a comparison of the different parameters of warped galaxies in the
radio, and especially in the visible, we find that: a) No large galaxy (large
mass or radius) has been found to have high amplitude in the warp, and there is
no correlation of size/mass with the degree of asymmetry of the warp. b) The
disc density and the ratio of dark to luminous mass show an opposing trend:
smaller values give more asymmetric warps in the inner radii (optical warps)
but show no correlation with the amplitude of the warp; however, in the
external radii neither is there any correlation with the asymmetry. c) A third
anticorrelation arises from a comparison of the amplitude and degree of
asymmetry in the warped galaxies. Hence, it seems that very massive dark matter
haloes have nothing to do with the formation of warps but only with the degree
of symmetry in the inner radii, and are unrelated to the warp shape for the
outermost radii. Denser discs show up the same dependence.


title: Constraints on the Circumstellar Disk Masses in the IC 348 Cluster

abstract:
  A 5.2' x 5.2' region toward the young cluster IC 348 has been imaged in the
millimeter continuum at 4.0" x 4.9" resolution with the OVRO interferometer to
a RMS noise level of 0.75 mJy/beam at 98 GHz. The data are used to constrain
the circumstellar disk masses in a cluster environment at an age of about 2
Myr. The mosaic encompasses 95 known members of the IC 348 cluster with a
stellar mass distribution that peaks at 0.2-0.5 Msun. None of the stars are
detected in the millimeter continuum at an intensity level of 3 sigma or
greater. The mean observed flux for the ensemble of 95 stars is 0.22 +/- 0.08
mJy. Assuming a dust temperature of 20 K, a mass opacity coefficient of kappa_o
= 0.02 cm^2/g at 1300 um, and a power law index of beta=1 for the particle
emissivity, these observations imply that the 3 sigma upper limit to the disk
mass around any individual star is 0.025 Msun, and that the average disk mass
is 0.002 +/- 0.001 Msun. The absence of disks with masses in excess of 0.025
Msun in IC 348 is different at the about 3 sigma confidence level from Taurus,
where about 14% of the stars in an optically selected sample have such disk
masses. Compared with the minimum mass needed to form the planets in our solar
system (about 0.01 Msun), the lack of massive disks and the low mean disk mass
in IC 348 suggest either that planets more massive than a few Jupiter masses
will form infrequently around 0.2-0.5 Msun stars in IC 348, or that the process
to form such planets has significantly depleted the disk of small dust grains
on time scales less than the cluster age of about 2 Myr.


title:
Large Magellanic Cloud Bump Cepheids: Probing the Stellar
  Mass-Luminosity Relation

abstract:
  We present the results of non-linear pulsation modelling of 20 bump Cepheids
in the LMC. By obtaining a optimal fit to the observed V,R MACHO lightcurves we
have placed tight constraints on stellar parameters of M, L, Teff and well as
quantities of distance modulus and reddening. We describe the mass-luminosity
relation for core-He burning for intermediate mass stars. The mass-luminosity
relation depends critically on the level of mixing within the stellar interior
over the course of the main-sequence lifetime. Our sample is significantly more
luminous than predicted by classical stellar evolutionary models that do not
incorporate extension to the convective core. Under the paradigm of convective
core overshoot our data implies $\Lambda_c$ of 0.65$\pm0.03l/H_p$. We derive a
LMC distance modulus of 18.55$\pm$0.02.


title: On the Physical Origin of OVI Absorption-Line Systems

abstract:
  We present a unified analysis of the O{\sc vi} absorption-lines seen in the
disk and halo of the Milky Way, high velocity clouds, the Magellanic Clouds,
starburst galaxies, and the intergalactic medium. We show that these disparate
systems define a simple relationship between the O{\sc vi} column density and
absorption-line width that is independent of the Oxygen abundance over the
range O/H $\sim$ 10% to twice solar. We show that this relation is exactly that
predicted theoretically as a radiatively cooling flow of hot gas passes through
the coronal temperature regime - independent of its density or metallicity (for
O/H $\gtrsim$ 0.1 solar). Since most of the intregalactic O{\sc vi} clouds obey
this relation, we infer that they can not have metallicities less than a few
percent solar. In order to be able to cool radiatively in less than a Hubble
time, the intergalactic clouds must be smaller than $\sim$1 Mpc in size. We
show that the cooling column densities for the O{\sc iv}, O{\sc v}, Ne{\sc v},
and Ne{\sc vi} ions are comparable to those seen in O{\sc vi}. This is also
true for the Li-like ions Ne{\sc viii}, Mg{\sc x}, and Si{\sc xii} (if the gas
is cooling from $T \gtrsim 10^6$ K). All these ions have strong resonance lines
in the extreme-ultraviolet spectral range, and would be accessible to $FUSE$ at
$z \gtrsim$ 0.2 to 0.8. We also show that the Li-like ions can be used to probe
radiatively cooling gas at temperatures an order-of-magnitude higher than where
their ionic fraction peaks. We calculate that the H-like (He-like) O, Ne, Mg,
Si, and S ions have cooling columns of $\sim10^{17}$ cm$^{-2}$. The O{\sc vii},
O{\sc viii}, and Ne{\sc ix} X-ray absorption-lines towards PKS 2155-304 may
arise in radiatively cooling gas in the Galactic disk or halo.


title: Problems and Progress in Astrophysical Dynamos

abstract:
  Astrophysical objects with negligible resistivity are often threaded by large
scale magnetic fields. The generation of these fields is somewhat mysterious,
since a magnetic field in a perfectly conducting fluid cannot change the flux
threading a fluid element, or the field topology. Classical dynamo theory
evades this limit by assuming that magnetic reconnection is fast, even for
vanishing resistivity, and that the large scale field can be generated by the
action of kinetic helicity. Both these claims have been severely criticized,
and the latter appears to conflict with strong theoretical arguments based on
magnetic helicity conservation and a series of numerical simulations. Here we
discuss recent efforts to explain fast magnetic reconnection through the
topological effects of a weak stochastic magnetic field component. We also show
how mean-field dynamo theory can be recast in a form which respects magnetic
helicity conservation, and how this changes our understanding of astrophysical
dynamos. Finally, we comment briefly on why an asymmetry between small scale
magnetic and velocity fields is necessary for dynamo action, and how it can
arise naturally.


title:
System description and first light-curves of HAT, an autonomous
  observatory for variability search

abstract:
  Having been operational at Kitt Peak for more than a year, the prototype of
the Hungarian Automated Telescope (HAT-1) has been used for all-sky variability
search of the northern hemisphere. The small autonomous observatory is
recording brightness of stars in the range of I~6--13m with a telephoto lens
and its 9x9 degree field of view, yielding a data rate of ~10^6 photometric
measurements per night. We give brief hardware and software description of the
system, controlled by a single PC running RealTime Linux operating system. We
overview site-specific details, and quantify the astrometric and photometric
capabilities of HAT. As a demonstration of system performance we give a sample
of 60 short period variables in a single selected field, all bright, with I <
13m, of which only 14 were known before. Depending on the observing strategy,
search for extrasolar planet transits is also a feasible observing program. We
conclude with a short discussion on future directions. Further information can
be found at the HAT homepage: http://www-cfa.harvard.edu/~gbakos/HAT/


title:
Photometric Mapping with ISOPHOT using the "P32" Astronomical
  Observation Template

abstract:
  The ``P32'' Astronomical Observation Template (AOT) provided a means to map
large areas of sky (up to 45x45 arcmin) in the FIR at high redundancy and with
sampling close to the Nyquist limit using the ISOPHOT C100 (3x3) and C200 (2x2)
detector arrays on board ISO. However, the transient response behaviour of the
Ga:Ge detectors, if uncorrected, can lead to severe systematic photometric
errors and distortions of source morphology on maps. Here we describe the basic
concepts of an algorithm which can successfully correct for transient response
artifacts in P32 observations. Examples are given demonstrating the photometric
and imaging performance of ISOPHOT P32 observations corrected using the
algorithm.


title:
Theories of Massive Star Formation: Collisions, Accretion and the View
  from the "I" of Orion

abstract:
  I review the arguments motivating models for massive star formation via
stellar collisions. I then describe how the standard accretion scenario,
involving the collapse of a quasi-hydrostatic gas core, can produce high-mass
stars in the pressurized regions of forming star clusters. I argue that the
observational evidence, particularly in the Orion hot core, favors the standard
accretion paradigm.


title: The Central Engines of Gamma-Ray Bursts

abstract:
  Leading models for the "central engine" of long, soft gamma-ray bursts (GRBs)
are briefly reviewed with emphasis on the collapsar model. Growing evidence
supports the hypothesis that GRBs are a supernova-like phenomenon occurring in
star forming regions, differing from ordinary supernovae in that a large
fraction of their energy is concentrated in highly relativistic jets. The
possible progenitors and physics of such explosions are discussed and the
important role of the interaction of the emerging relativistic jet with the
collapsing star is emphasized. This interaction may be responsible for most of
the time structure seen in long, soft GRBs. What we have called "GRBs" may
actually be a diverse set of phenomena with a key parameter being the angle at
which the burst is observed. GRB 980425/SN 1988bw and the recently discovered
hard x-ray flashes may be examples of this diversity.


title: On the Progenitors of Collapsars

abstract:
  We study the evolution of stars that may be the progenitors of common
(long-soft) GRBs. Bare rotating helium stars, presumed to have lost their
envelopes due to winds or companions, are followed from central helium ignition
to iron core collapse. Including realistic estimates of angular momentum
transport (Heger, Langer, & Woosley 2000) by non-magnetic processes and mass
loss, one is still able to create a collapsed object at the end with sufficient
angular momentum to form a centrifugally supported disk, i.e., to drive a
collapsar engine. However, inclusion of current estimates of magnetic torques
(Spruit 2002) results in too little angular momentum for collapsars.


title: Gravitational Lens Time Delays in CDM

abstract:
  In standard CDM halo models, the time delay of a gravitational lens is
determined by the cold baryon mass fraction, f, of the visible galaxy relative
to the overall halo. The observed time delays in PG1115+080, SBS1520+530,
B1600+434 and HE2149-2745 give Hubble constants consistent with the HST Key
Project value of H0=72+/-8 km/s Mpc only if f>0.2 (1-sided 68% confidence),
which is larger than the upper bound of fmax=Omega_b/Omega_0=0.15+/-0.05
estimated from the CMB. If all available baryons cool and f=fmax then the time
delays imply H0=65+/-6 km/s Mpc (95% confidence). If local inventories of cold
baryons, f=0.013/h70, are correct, then H0=52+/-6 km/s Mpc and the halo
parameters closely match isothermal mass models. Isothermal models are also
consistent with strong and weak lens studies, stellar dynamics and X-ray
observations on these scales, while significantly more centrally concentrated
models are not. There is a a conflict between gravitational lens time delays,
the local distance scale and standard CDM halo models.


title: The plasma-solid equilibrium an in Debye plasma

abstract:
  Using the Salpeter criterion and known results from solid state physics,the
Debye temperature of a solid in equilibrium with a Debye-Huckel plasma was
calculated.This result could have interesting applications in studies of
various kinds of interstellar clouds.


title:
Globular cluster formation from gravitational tidal effects of merging
  and interacting galaxies

abstract:
  We investigate the spatial, kinematic and chemical properties of globular
cluster systems formed in merging and interacting galaxies using N-body/SPH
simulations. Although we can not resolve individual clusters in our simulation,
we assume that they form in collapsing molecular clouds when the local external
gas pressure exceeds 10$^5$ $k_B$ (where $k_B$ is the Boltzmann constant).
Several simulations are carried out for a range of initial conditions and
galaxy mass ratios. The input model spirals are given a halo globular cluster
system similar to those observed for the Milky Way and M31. Gravitational tidal
effects during galaxy merging and interaction leads to a dramatic increase in
gas pressure, which exceeds our threshold and hence triggers new globular
cluster formation. We investigate the properties of the globular cluster system
in the remnant galaxy, such as number density, specific frequency, kinematic
properties and metallicity distribution. Different orbital conditions and mass
ratios give rise to a range in globular cluster properties, particularly for
the interaction models. Our key results are the following: The newly formed
metal-rich clusters are concentrated at the centre of the merger remnant
elliptical, whereas the metal-poor ones are distributed to the outer parts due
to strong angular momentum transfer. (abridged version)


title: The plasma-solid transition:some implications in astrophysics

abstract:
  Using a criterion proposed by Salpeter,and standard solid state physics,we
have determined the Debye temperature of a solid in equilibrium with the
electron gas surrounding it.The results obtained can have implications in
studies of the interstellar medium.


title: Plane waves in a general Robertson-Walker background

abstract:
  We present an exact solution for the plane wave mode functions of a massless,
minimally coupled scalar propagating in an arbitrary homogeneous, isotropic and
spatially flat geometry. Our solution encompasses all previous solvable special
cases such as de Sitter and power law expansion. Moreover, it can generate the
mode functions for gravitons. We discuss some of the many applications that are
now possible.


title:
Accretion disks around black holes: dynamical evolution, meridional
  circulations and gamma ray bursts

abstract:
  We study the hydrodynamical evolution of massive accretion disks around black
holes, formed when a neutron star is disrupted by a black hole in a binary
system. Initial conditions are taken from 3D calculations of coalescing
binaries. Assuming azimuthal symmetry, we follow the time dependence of the
disk structure for 0.2 seconds. We use an ideal gas e.o.s., and assume that all
the dissipated energy is radiated away. The disks evolve due to viscous
stresses, modeled with an alpha law. We study the disk structure, and the
strong meridional circulations that are established and persist throughout our
calculations. These consist of strong outflows along the equatorial plane that
reverse direction close to the surface of the disk and converge on the
accretor. In the context of GRBs, we estimate the energy released from the
system in neutrinos and through magnetic-dominated mechanisms, and find it can
be as high as 10^52 erg and 10^51 erg respectively, during an estimated
timescale of 0.1-0.2 seconds. neutrino-anti neutrino annihilation is likely to
produce bursts from only an impulsive energy input (the annihilation luminosity
scales as t^(-5/2)) and so would be unable to account for a large fraction of
bursts with complicated light curves. However a gas mass ~0.1-0.25 Msun
survives in the orbiting debris, enabling strong magnetic fields (~10^16 Gauss)
to be anchored in the dense matter long enough to power short GRBs. We also
investigate the continuous energy injection that arises as the black hole
slowly swallows the rest of the disk and discuss its consequences on the GRB
afterglow emission.


title: Measurement of Arcminute Scale Anisotropy with the BIMA Array

abstract:
  We report the results of our continued study of arcminute scale anisotropy in
the Cosmic Microwave Background (CMB) with the Berkeley-Illinois-Maryland
Array. The survey consists of ten independent fields selected for low infrared
dust emission and lack of bright radio point sources. With observations from
the Very Large Array (VLA) at 4.8 GHz, we have identified point sources which
could act as contaminants in estimates of the CMB power spectrum and removed
them in the analysis. Modeling the observed power spectrum with a single flat
band power with average multipole of \ell_{eff}=6864, we find
dT=14.2^{+4.8}_{-6.0} \mu K at 68% confidence. The signal in the visibility
data exceeds the expected contribution from instrumental noise with 96.5%
confidence. We have also divided the data into two bins corresponding to
different spatial resolutions in the power spectrum. We find
dT_1=16.6^{+5.3}_{-5.9} \mu K at 68% confidence for CMB flat band power
described by an average multipole of \ell_{eff}=5237 and dT_2<26.5 \mu K at 95%
confidence for \ell_{eff}=8748.


title:
Face-on, stream-fed intermediate polars: an alternative model for RX
  J1914.4+2456 and RX J0806.3+1527

abstract:
  RX J1914.4+2456 and RX J0806.3+1527 have been proposed as double degenerate
binaries with orbital periods of 569s and 321s respectively. An alternative
model, in which the periods are related to the spin of a magnetic white dwarf
in an intermediate polar system, has been rejected by other authors. We show
that a face-on, stream-fed intermediate polar model for the two systems is
viable and preferable to the other models. In each case, the X-ray modulation
periods then represent the rotation of the white dwarf in the binary reference
frame. The model explains the fully modulated X-ray pulse profiles, the X-ray
spectra, the antiphase between X-ray and optical/infrared modulation, the lack
of longer period modulation, and the low level of polarization. The optical
spectrum of RX J0806.3+1527 suggests that Balmer series lines are present,
blended with HeII lines. This is unlike the spectra of any of the known AM CVn
stars and suggests that the system is not a double degenerate binary. The
optical spectrum of RX J1914.4+2456 has spectral features that are consistent
with those of a K star, ruling out the double degenerate models in this case.
The lack of optical/infrared emission lines in RX J1914.4+2456 may be
attributed to a high mass accretion rate and its face-on orientation. Its
reported period decrease may be a short term spin-up episode driven by the
current high M-dot. Finally we suggest that there is an observational selection
effect such that the face-on intermediate polars that are detected will all
have a stream-fed component, and the purely stream-fed intermediate polars that
are detected will all be face-on systems.


title:
Efficient Cosmological Parameter Estimation from Microwave Background
  Anisotropies

abstract:
  We revisit the issue of cosmological parameter estimation in light of current
and upcoming high-precision measurements of the cosmic microwave background
power spectrum. Physical quantities which determine the power spectrum are
reviewed, and their connection to familiar cosmological parameters is
explicated. We present a set of physical parameters, analytic functions of the
usual cosmological parameters, upon which the microwave background power
spectrum depends linearly (or with some other simple dependence) over a wide
range of parameter values. With such a set of parameters, microwave background
power spectra can be estimated with high accuracy and negligible computational
effort, vastly increasing the efficiency of cosmological parameter error
determination. The techniques presented here allow calculation of microwave
background power spectra $10^5$ times faster than comparably accurate direct
codes (after precomputing a handful of power spectra). We discuss various
issues of parameter estimation, including parameter degeneracies, numerical
precision, mapping between physical and cosmological parameters, and systematic
errors, and illustrate these considerations with an idealized model of the MAP
experiment.


title: The milliarcsecond-scale jet in the quasar J1625+4134

abstract:
  We present Very Long Baseline Array (VLBA) observations of the radio source
J1625+4134 at 22 and 15 GHz and analyze them in concurrence with other existing
VLBI data on this source. The high resolution images at 15 and 22 GHz show a
short and bending jet which has about $270\degr$ difference in position angle
with the northern jet detected at lower frequencies. The new high resolution
data, combined with the data available in the literature, allow us to estimate
the spectral index of the components and identify one of the compact components
as the VLBI core based on its flat spectrum between 5 and 22 GHz. Relative to
this core component, the jet appears to be bi-directional. The proper motion
measurement of the component C2 and the estimate of the Doppler boosting factor
suggest that the orientation of the jet is close to the line of sight. The
projection effect of an intrinsically sharply bending jet within a few mas from
the core or the erratic change in the nozzle direction of the jet may account
for the uncommon bi-directional structure of the jet in J1625+4134.


title:
A HR-like Diagram for Solar/Stellar Flares and Corona -- Emission
  Measure vs Temperature Diagram

abstract:
  In our previous paper, we have presented a theory to explain the observed
universal correlation between the emission measure ($EM=n^2 V$) and temperature
(T) for solar/stellar flares on the basis of the magnetic reconnection model
with heat conduction and chromospheric evaporation. Here n is the electron
density and V is the volume. By extending our theory to general situations, we
examined the EM-T diagram in detail, and found the following properties: 1) The
universal correlation sequence (``main sequence flares'') with $EM \propto
T^{17/2}$ corresponds to the case of constant heating flux or equivalently the
case of constant magnetic field strength in the reconnection model. 2) The EM-T
diagram has a forbidden region, where gas pressure of flares exceeds magnetic
pressure. 3) There is a coronal branch with $EM \propto T^{15/2}$ for $T< 10^7$
K, and $EM \propto T^{13/2}$ for $T> 10^7$ K. This branch is situated left side
of the main sequence flares in the EM-T diagram. 4) There is another forbidden
region determined by the length of flare loop; a lower limit of flare loop is
$10^7$ cm. Small flares near this limit correspond to nanoflares observed by
SOHO/EIT. 5) We can plot flare evolution track on the EM-T diagram. A flare
evolves from the coronal branch to main sequence flares, then returns to the
coronal branch eventually. These properties of the EM-T diagram are similar to
those of the HR diagram for stars, and thus we propose that the EM-T diagram is
quite useful to estimate the physical quantities (loop length, heating flux,
magnetic field strength, total energy and so on) of flares and corona when
there is no spatially resolved imaging observations.


title: Modeling Core-Collapse Supernovae in 3-Dimensions

abstract:
  We present the first complete 3-dimensional simulations of the core-collapse
of a massive star from the onset of collapse to the resultant supernova
explosion. We compare the structure of the convective instabilities that occur
in 3-dimensional models with those of past 2-dimensional simulations. Although
the convective instabilities are clearly 3-dimensional in nature, we find that
both the size-scale of the flows and the net enhancement to neutrino heating
does not differ greatly between 2- and 3-dimensional models. The explosion
energy, explosion timescale, and remnant mass does not differ by more than 10%
between 2- and 3-dimensional simulations.


title: Chandra Snapshot Observations of LINERs with a Compact Radio Core

abstract:
  The results of Chandra snapshot observations of 11 LINERs (Low-Ionization
Nuclear Emission-line Regions), three low-luminosity Seyfert galaxies, and one
HII-LINER transition object are presented. Our sample consists of all the
objects with a flat or inverted spectrum compact radio core in the VLA survey
of 48 low-luminosity AGN (LLAGN) by Nagar et al. (2000). An X-ray nucleus is
detected in all galaxies except one and their X-ray luminosities are in the
range 5x10^38 to 8x10^41 ergs s^-1. The X-ray to Halpha luminosity ratios for
11 out of 14 objects are in good agreement with the value characteristic of
LLAGNs and more luminous AGNs, and indicate that their optical emission lines
are predominantly powered by a LLAGN. For three objects, this ratio is less
than expected. Comparing with multi-wavelength results, we find that these
three galaxies are most likely to be heavily obscured AGN. We compare the radio
to X-ray luminosity ratio of LLAGNs with those of more-luminous AGNs, and
confirm the suggestion that a large fraction of LLAGNs are radio loud.


title: Chemo-dynamical evolution of Globular Cluster Systems

abstract:
  We studied the relation between the ratio of rotational velocity to velocity
dispersion and the metallicity (<v_{rot}>/\sigma_{v}-metallicity relation) of
globular cluster systems (GCS) of disk galaxies by comparing the relation
predicted from simple chemo-dynamical models for the formation and evolution of
disk galaxies with the observed kinematical and chemical properties of their
GCSs. We conclude that proto disk galaxies underwent a slow initial collapse
that was followed by a rapid contraction and derive that the ratio of the
initial collapse time scale to the active star formation time scale is \sim 6
for our Galaxy and \sim 15 for M31. The fundamental formation process of disk
galaxies was simulated based on simple chemo-dynamical models assuming the
conservation of their angular momentum. We suggest that there is a typical
universal pattern in the <v_{rot}>/\sigma_{v}-metallicity relation of the GCS
of disk galaxies. This picture is supported by the observed properties of GCSs
in the Galaxy and in M31. This relation would deviate from the universal
pattern, however, if large-scale merging events took major role in
chemo-dynamical evolution of galaxies and will reflect the epoch of such
merging events. We discuss the properties of the GCS of M81 and suggest the
presence of past major merging event.


title:
The Effects of Thermonuclear Reaction Rate Variations on Nova
  Nucleosynthesis: A Sensitivity Study

abstract:
  We investigate the effects of thermonuclear reaction rate uncertainties on
nova nucleosynthesis. One-zone nucleosynthesis calculations have been performed
by adopting temperature-density-time profiles of the hottest hydrogen-burning
zone (i.e., the region in which most of the nucleosynthesis takes place). We
obtain our profiles from 7 different, recently published, hydrodynamic nova
simulations covering peak temperatures in the range from Tpeak=0.145-0.418 GK.
For each of these profiles, we individually varied the rates of 175 reactions
within their associated errors and analyzed the resulting abundance changes of
142 isotopes in the mass range below A=40. In total, we performed 7350 nuclear
reaction network calculations. We use the most recent thermonuclear reaction
rate evaluations for the mass ranges A=1-20 and A=20-40. For the theoretical
astrophysicist, our results indicate the extent to which nova nucleosynthesis
calculations depend on presently uncertain nuclear physics input, while for the
experimental nuclear physicist our results represent at least a qualitative
guide for future measurements at stable and radioactive ion beam facilities. We
find that present reaction rate estimates are reliable for predictions of Li,
Be, C and N abundances in nova nucleosynthesis. However, rate uncertainties of
several reactions have to be reduced significantly in order to predict more
reliable O, F, Ne, Na, Mg, Al, Si, S, Cl and Ar abundances. Results are
presented in tabular form for each adopted nova simulation.


title: The AMS-02 Time of Flight System

abstract:
  The Time-of-Flight (TOF) system of the AMS detector gives the fast trigger to
the read out electronics and measures velocity, direction and charge of the
crossing particles. The first version of the detector (called AMS-01) has flown
in 1998 aboard of the shuttle Discovery for a 10 days test mission, and
collected about $10^8$ events. The new version (called AMS-02) will be
installed on the International Space Station and will operate for at least
three years, collecting roughly $10^{10}$ Cosmic Ray (CR) particles. The TOF
system of AMS-01 successfully operated during the test mission, obtaining a
time resolution of 120 ps for protons and better for other CR ions. The TOF
system of AMS-02 will be different due to the strong fringing magnetic field
and weight constraints


title: Imaging and spectroscopy of DENIS-P J104814-395606

abstract:
  We obtained deep H- and K-band images of DENIS-P J104814-395606 using SofI
and the speckle camera SHARP-I at the ESO-3.5m-NTT as well as QUIRC at the
Mauna Kea 2.2m telescope between December 2000 and June 2001. The target was
recently discovered as nearby M9-dwarf among DENIS sources (Delfosse et al.
2001). We detect parallactic motion on our images and determine the distance to
be 4.6 pm 0.3 pc, more precise than previously known. From the available
colors, the distance, and the spectral type, we conclude from theoretical
models that the star has a mass of ~0.075 to 0.09 M_sun and an age of ~1 to 2
Gyrs. We also obtained H- and K-band spectra of this star with ISAAC at the
VLT. A faint companion candidate is detected 6 arc sec NNW of the star, which
is 6.4 pm 0.5 mag fainter in H. However, according to another image taken
several month later, the companion candidate is not co-moving with the
M9-dwarf. Instead, it is a non-moving background object. Limits for undetected
companion candidates are such that we can exclude any stellar companions
outside of ~0.25 arc sec (1 AU), any brown dwarf companions (above the
deuterium burning mass limit) outside of ~2 arc sec (9 AU), and also any
companion down to ~40 M_jup with \ge 0.15 arc sec (0.7 AU) separation, all
calculated for an age of 2 Gyrs. Our observations show that direct imaging of
sub-stellar companions near the deuterium burning mass limit in orbit around
nearby ultra-cool dwarfs is possible, even with separations that are smaller
than the semi-major axis of the outermost planet in our solar system, namely a
few tens of AU.


title:
Non-vacuum initial states for the cosmological perturbations and the
  back-reaction problem of inflation

abstract:
  In the framework of Inflationary theory, the assumption that the quantum
state of the perturbations is a non-vacuum state leads to a difficulty:
non-vacuum initial states imply, in general, a large energy density of inflaton
field quanta, not of a cosmological term type, that could prevent the
inflationary phase. In this short note, we discuss in detail why this is so,
keeping an eye on possible non-Gaussian features due to considering generic
non-vacuum initial states.


title: Thermal Radiation from Neutron Stars: Chandra Results

abstract:
  The outstanding capabilities of the Chandra X-ray observatory have greatly
increased our potential to observe and analyze thermal radiation from the
surfaces of neutron stars (NSs). Such observations allow one to measure the
surface temperatures and confront them with the predictions of the NS cooling
models. Detection of gravitationally redshifted spectral lines can yield the NS
mass-to-radius ratio. In rare cases when the distance is known, one can measure
the NS radius, which is particularly important to constrain the equation of
state of the superdense matter in the NS interiors. Finally, one can infer the
chemical composition of the NS surface layers, which provides information about
formation of NSs and their interaction with the environment. We overview the
recent Chandra results on the thermal radiation from various types of NSs --
active pulsars, young radio-quiet neutron stars in supernova remnants, old
radio-silent ``dim'' neutron stars -- and discuss their implications.


title: Modeling Neutron Star Atmospheres

abstract:
  Models of thermal emission of neutron stars, presumably formed in their
atmospheres, are needed to infer the surface temperatures, magnetic fields,
chemical composition, and neutron star masses and radii from the observational
data. This information, supplemented with model equations of state and neutron
star cooling models, is expected to move us further in understanding the
fundamental properties of the superdense matter in the neutron star interiors.
The neutron star atmospheres are very different from those of usual stars due
to the immense gravity and huge magnetic fields. In this presentation we review
the current status of the neutron star atmosphere modeling and present most
important results.


title:
Constraints of the Clumpyness of Dark Matter Halos Through Heating of
  the Disk Galaxies

abstract:
  Motivated by the presence of numerous dark matter clumps in the Milky
  Way's halo as expected from the cold dark matter cosmological model, we
conduct numerical simulations to examine the heating of the disk. We construct
an initial galaxy model in equilibrium, with a stable thin disk.
  The disk interacts with dark matter clumps for about 5 Gyr. Three physical
effects are examined : first the mass spectrum of the dark matter clumps,
second the initial thickness of the galactic disk, and third the spatial
distribution of the clumps. We find that the massive end of the mass spectrum
determines the amount of disk heating. Thicker disks suffer less heating. There
is a certain thickness at which the heating owing to the interaction with the
clumps becomes saturates. We also find that the heating produced by the model
which mimics the distribution found in
  Standard CDM cosmology is significant and too high to explain the
observational constraints. On the other hand, our model that corresponds to the
clump distribution in a $\Lambda$CDM cosmology produces no significant heating.
This result suggests that the $\Lambda$CDM cosmology is preferable with respect
to the Standard CDM cosmology in explaining the thickness of the Milky Way.


title: Caby Photometry of the Hyades: Comparisons to the Field Stars

abstract:
  Intermediate-band photometry of the Hyades cluster on the Caby system is
presented for dwarf stars ranging from spectral type A through late K. A mean
hk, b-y relation is constructed using only single stars without anomalous
atmospheres and compared to the field stars of the solar neighborhood. For the
F dwarfs, the Hyades relation defines an approximate LOWER bound in the
two-color diagram, consistent with an [Fe/H] between +0.10 and +0.15. These
index-color diagrams follow the common convention of presenting stars with
highest abundance at the bottom of the plot although the index values for the
metal-rich stars are numerically larger. For field F dwarfs in the range [Fe/H]
between +0.4 and -1.0, [Fe/H] = -5.6 delta-hk + 0.125, with no evidence for a
color dependence in the slope. For the G and K dwarfs, the Hyades mean relation
crosses the field star distribution in the two-color diagram, defining an
approximate UPPER bound for the local disk stars. Stars found above the Hyades
stars fall in at least one of three categories: [Fe/H] below -0.7, [Fe/H] above
that of the Hyades, or chromospherically active. It is concluded that, contrary
to the predictions of model atmospheres, the hk index for cool dwarfs at a
given color hits a maximum value for stars below solar composition and, with
increasing [Fe/H] above some critical value, declines. This trend is
consistent, however, with the predictions from synthetic indices based upon
much narrower Ca filters where the crossover is caused by the metallicity
sensitivity of b-y.


title: A fast X-ray timing capability on XEUS

abstract:
  Fast X-ray timing can be used to probe strong gravity fields around collapsed
objects and constrain the equation of state of dense matter in neutron stars.
These studies require extremely good photon statistics. In view of the huge
collecting area of its mirrors, XEUS could make a unique contribution to this
field. For this reason, we propose to include a fast X-ray timing capability in
the focal plane of the XEUS mirrors. We briefly outline the scientific
motivation for such a capability. We compute some sensitivity estimates, which
indicate that XEUS could provide better than an order of magnitude sensitivity
improvement over the Rossi X-ray Timing Explorer. Finally, we present a
possible detector implementation, which could be an array of small size silicon
drift detectors operated out of focus.


title: Far infrared and Radio emission in dusty starburst galaxies

abstract:
  We revisit the nature of the FIR/Radio correlation by means of the most
recent models for star forming galaxies. We model the IR emission with our
population synthesis code, GRASIL (Silva et al. 1998). As for the radio
emission, we revisit the simple model of Condon & Yin (1990). We find that a
tightFIR/Radio correlation is natural when the synchrotron mechanism dominates
over the inverse Compton, and the electrons cooling time is shorter than the
fading time of the supernova rate. Observations indicate that both these
conditions are met in star forming galaxies. However since the radio non
thermal emission is delayed, deviations are expected both in the early phases
of a starburst, when the radio thermal component dominates, and in the
post-starburst phase, when the bulk of the NT component originates from less
massive stars. This delay allows the analysis of obscured starbursts with a
time resolution of a few tens of Myrs, unreachable with other star formation
indicators. We suggest to complement the analysis of the deviations from the
FIR/Radio correlation with the radio slope to obtain characteristic parameters
of the burst. The analysis of a sample of compact ULIRGs shows that they are
intense but transient starbursts, to which one should not apply usual SF
indicators devised for constant SF rates. We also discuss the possibility of
using the q- radio slope diagram to asses the presence of obscured AGN. A firm
prediction of the models is an apparent radio excess during the post-starburst
phase, which seems to be typical of a class of star forming galaxies in rich
cluster cores. We discuss how deviations from the correlation, due to the
evolutionary status of the starburst, affect the technique of photometric
redshift determination widely used for high-z sources.


title: Pulsar Luminosity Function

abstract:
  We construct and investigate the pulsar luminosity function using the new
catalogue which includes data for 1315 radio pulsars. The luminosity functions
are constructed for 400 and 1400 MHz separately, and they are compared. Also,
the luminosity functions excluding the binary millisecond pulsars and other
pulsars with low magnetic fields are constructed. The 1400 MHz luminosities as
a function of characteristic age and as a function of magnetic field for radio
pulsars, anomalous X-ray pulsars and dim radio quiet neutron stars are
presented and the implications of the pulsar luminosity function on these new
kind of neutron stars are discussed.


title: Optically-selected clusters at 0.8 < z < 1.3 in the EIS Cluster Survey

abstract:
  This paper presents preliminary results of a spectroscopic survey being
conducted at the VLT of fields with optically-selected cluster candidates
identified in the EIS I-band survey. Here we report our findings for three
candidates selected for having estimated redshifts in the range z=0.8-1.1. New
multi-band optical/infrared data were used to assign photometric redshifts to
galaxies in the cluster fields and to select possible cluster members in
preparation of the spectroscopic observations. Based on the available
spectroscopic data, which includes 147 new redshifts for galaxies with
Iab<22-23, we confirm the detection of four density enhancements at a
confidence level >99%. The detected concentrations include systems with
redshifts z=0.81, z=0.95, z=1.14 and the discovery of the first
optically-selected cluster at z=1.3. The latter system, with three concordant
redshifts, coincides remarkably well with the location of a firm X-ray
detection (>5sigma) in a ~80ksec XMM-Newton image taken as part of this program
which will be presented in a future paper (Neumann et al. 2002). The z>1
systems presented here are possibly the most distant identified so far by their
optical properties alone.


title:
Inflation: flow, fixed points and observables to arbitrary order in slow
  roll

abstract:
  I generalize the inflationary flow equations of Hoffman and Turner to
arbitrary order in slow roll. This makes it possible to study the predictions
of slow roll inflation in the full observable parameter space of tensor/scalar
ratio $r$, spectral index $n$, and running $d n / d \ln k$. It also becomes
possible to identify exact fixed points in the parameter flow. I numerically
evaluate the flow equations to fifth order in slow roll for a set of randomly
chosen initial conditions and find that the models cluster strongly in the
observable parameter space, indicating a ``generic'' set of predictions for
slow roll inflation. I comment briefly on the the interesting proposed
correspondence between flow in inflationary parameter space and renormalization
group flow in a boundary conformal field theory.


title: X-rays from star-forming regions: New objects, new physics, new visions

abstract:
  Star-forming regions have been the targets of X-ray observations since the
dawn of satellite X-ray astronomy. The increase in sensitivity and/or spatial
resolution offered by XMM-Newton and Chandra allows a dramatic improvement,
both qualitative and quantitative, on our knowledge of high-energy phenomena in
these regions and the underlying physical processes. We summarize here some
recent developments: the Orion Nebula Cluster and its 1000+ stellar X-ray
sources; Herbig-Haro objects and their high-speed shocks; protostars, brown
dwarfs and their unusual magnetic activity; and the discovery of diffuse X-ray
emission from HII regions, presumably related to strong winds from massive
stars. The role that future X-ray missions may play in the field is already
starting to be visible.


title:
Decapitating the Duck: The (non)association of PSR B1757-24 and
  supernova remnant G5.4-1.2

abstract:
  We have made the first direct interferometric proper motion measurements of
the radio pulsar B1757-24, which sits at the tip of the "beak" of the putative
"Duck" supernova remnant. The peculiar morphology of this radio complex has
been used to argue alternately that the pulsar's space motion was either
surprisingly high or surprisingly low. In fact, we show that the pulsar's
motion is so small that it and its associated nonthermal nebula G5.27-0.9 (the
"head") are almost certainly unrelated to the much larger G5.4-1.2 (the
"wings").


title: Helium-Core White Dwarfs in Globular Clusters

abstract:
  We examine the theoretical implications of a population of low-mass
helium-core white dwarfs in globular clusters. In particular, we focus on the
observed population in the core of NGC 6397, where several low-mass white dwarf
canditates have been identified as ``non-flickerers'' by Cool and
collaborators. Age and mass estimates from cooling models, combined with
dynamical and evolutionary considerations, lead us to infer that the dark
binary companions are C/O white dwarfs rather than neutron stars. Furthermore,
we find that the progenitor binaries very likely underwent an exchange
interaction within the last 1.e9 years. We examine the prospects for detecting
a similar population in other globular clusters, with particular attention to
the case of 47 Tuc.


title:
Gamma-Ray Constraints on Neutralino Dark Matter Clumps in the Galactic
  Halo

abstract:
  According to high resolution cold dark matter (CDM) simulations, large
virialized halos are formed through the constant merging of smaller halos
formed at earlier times. In particular, the halo of our Galaxy may have
hundreds of dark matter clumps. The annihilation of dark matter particles such
as the neutralino in these clumps generates $\gamma$-ray fluxes that can
potentially be detected by future experiments such as GLAST. We find that,
depending on the parameters of the clump density profile and on the
distribution of clumps in the Galactic halo, the contribution to the diffuse
$\gamma$-ray background from clumps can constrain the properties of neutralinos
such as the mass and annihilation cross section. We model the density profile
of clumps by three representative dark matter profiles: singular isothermal
spheres (SIS), Moore profiles, and Navarro, Frenk and White (NFW) density
profiles and calculate the spectrum and angular distribution in the sky of the
$\gamma$-ray flux due to neutralino annihilation in the clumpy halo of the
Galaxy. The calculations are carried out in the context of two different
scenarios for the distribution of clumps in the Galaxy and their
concentrations, which result in very different conclusions.


title: The Formation of Massive Stars from Turbulent Cores

abstract:
  Observations indicate that massive stars form in regions of very high surface
density, ~1 g cm^-2. Clusters containing massive stars and globular clusters
have a comparable column density. The total pressure in clouds of such a column
density is P/k~10^8-10^9 K cm^-3, far greater than that in the diffuse ISM or
the average in GMCs. Observations show that massive star-forming regions are
supersonically turbulent, and we show that the molecular cores out of which
individual massive stars form are as well. The protostellar accretion rate in
such a core is approximately equal to the instantaneous mass of the star
divided by the free-fall time of the gas that is accreting onto the star
(Stahler, Shu, & Taam 1980). The star-formation time in this Turbulent Core
model for massive star formation is several mean free-fall timesscales of the
core, but is about equal to that of the region in which the core is embedded.
The typical time for a massive star to form is about 10^5 yr and the accretion
rate is high enough to overcome radiation pressure due to the luminosity of the
star. For the typical case we consider, in which the cores out of which the
stars form have a density structure varying as r^{-1.5}, the protostellar
accretion rate grows linearly with time. We calculate the evolution of the
radius of a protostar and determine the accretion luminosity. At the high
accretion rates that are typical in regions of massive star formation,
protostars join the main sequence at about 20 solar masses. We apply these
results to predict the properties of protostars thought to be powering several
observed hot molecular cores, including the Orion hot core and W3(H2O). In the
Appendixes, we discuss the pressure in molecular clouds and we argue that
``logatropic'' models for molecular clouds are incompatible with observation.


title:
The Origin of Molecular Cloud Turbulence and its role on Determining the
  Star Formation Efficiency

abstract:
  We suggest that molecular cloud (MC) turbulence is a consequence of the very
process of MC formation by collisions of larger-scale flows in the diffuse
atomic gas, which generate turbulence in the accumulated gas through bending-
mode instabilities. Turbulence is thus maintained for as long as the
accumulation process lasts ($\sim$ several Myr). Assuming that supersonic
turbulence in MCs has the double role of preventing global collapse while
promoting the formation of smaller-scale structures by turbulent compression
(``turbulent fragmentation''), we then note the following properties: a)
Turbulent fragmentation necessarily deposits progressively smaller fractions of
the total mass in regions of progressively smaller sizes, because the smaller
structures are subsets of the larger ones. b) The turbulent spectrum implies
that smaller scales have smaller velocity differences. Therefore, below some
scale, denoted $l_{\rm eq}$, the turbulent motions become subsonic. This is an
energy {\it distribution} phenomenon, not a dissipative one. On this basis, we
propose that the star formation efficiency (SFE) is determined by the fraction
of the total mass that is deposited in clumps with masses larger than $M_{\rm
J}(l_{\rm eq})$, the Jeans mass at scale $l_{\rm eq}$, because subsonic
turbulence cannot promote any further subfragmentation. In this scenario, the
SFE should be a monotonically increasing function of the sonic and turbulent
equality scale, $l_{\rm eq}$. We present preliminary numerical tests supporting
this prediction, and thus the suggestion that (one of the) relevant
parameter(s) is $l_{\rm eq}$, and compare with previous proposals that the
relevant parameter is the energy injection scale.