title: X-Ray Spectra of Intermediate-Luminosity, Radio-Loud Quasars

abstract:
  We present new hard X-ray spectra of three radio-loud AGNs of moderately high
X-ray luminosity (L_x ~ 10^45 erg/s; PKS 2349-01, 3C 323.1, and 4C 74.26)
obtained with ASCA and BeppoSAX. The X-ray continua are described in all three
cases with a power law model with photon indices of Gamma~1.85, modified at low
energies by absorption in excess of the Galactic, which appears to be due to
neutral gas. At higher energies, an Fe Ka emission line is detected in PKS
2349-01 and 4C 74.26, and is tentatively detected in 3C 323.1. The equivalent
widths of the lines are consistent, albeit within large uncertainties, with the
values for radio-quiet AGN of comparable X-ray luminosity. The Fe Ka line is
unresolved in 4C 74.26. In the case of PKS 2349-01, however, the inferred
properties of the line depend on the model adopted for the continuum: if a
simple power-law model is used, the line is resolved at more than 99%
confidence with a full width at half maximum corresponding to approximately
50,000 km/s and a rest-frame equivalent width of 230 +/- 120 eV, but if a
Compton "reflection" model is used the line is found to be a factor of 2
weaker, for an assumed full width at half maximum of 50,000 km/s. In 4C 74.26,
a strong Compton "reflection" component is detected. Its strength suggests that
the scattering medium subtends a solid angle of 2pi to the illuminating source.
Overall, the spectral indices of these radio-loud quasars are remarkably
similar to those of their radio-quiet counterparts. On the other hand, if the
absorber is indeed neutral, as our results suggest, this would be consistent
with the typical properties of radio-loud AGNs.


title:
Orphan Afterglows of Collimated Gamma-Ray Bursts: Rate Predictions and
  Prospects for Detection

abstract:
  We make a quantitative prediction for the detection rate of orphan GRB
afterglows as a function of flux sensitivity in X-ray, optical, and radio
wavebands, based on a recent model of collimated GRB afterglows. We find that
the orphan afterglow rate strongly depends on the opening angle of the jet
(roughly \propto \theta_jet^{-2}), as expected from simple geometrical
consideration, if the total jet energy is kept constant as suggested by recent
studies. The relative beaming factor b_rel, i.e., the ratio of all afterglow
rate including orphans to those associated with observable prompt GRBs, could
be as high as b_rel >~ 100 for searches deeper than R ~ 24, depending on
afterglow parameters. To make the most plausible predictions, we average the
model emission for ten sets of afterglow parameters obtained through fits to
ten well-observed, collimated GRB jets, weighted by the sky coverage of each
jet. Our model expectations are consistent with the results (or constraints)
obtained by all past searches. We estimate the number of orphan afterglows in
the first 1500deg^2 field of the SDSS to be about 0.2. The relative beaming
factor b_rel is rapidly increasing with the search sensitivity: b_rel ~ 3 for
the SDSS sensitivity to transient objects in the northern sky (R ~ 19), ~14 for
the past high-z supernova searches (R ~ 23), and ~50 for the sensitivity of the
Subaru Suprime-Cam (R ~ 26). Predictions are made for the current facilities
and future projects in X-ray, optical, and radio bands. Among them, the
southern-sky observation of the SDSS (sensitive to transients down to R ~ 23)
could detect ~40 orphan afterglows during the five-year operation. Allen
Telescope Array would find about 200 afterglows in a radio band at ~0.1-1mJy
with b_rel ~ 15.


title: Wide field interferometric imaging with single-mode fibers

abstract:
  Classical single-mode fiber interferometers, using one fiber per aperture,
have very limited imaging capabilities and small field of view. Observations of
extended sources (resolved by one aperture) cannot be fully corrected for
wavefront aberrations: accurate measurements of object visibilities are then
made very difficult from ground-based fiber interferometers. These limitations
are very severe for the new generation of interferometers, which make use of
large telescopes equipped with adaptive optics, but can be overcome by using
several fibers per aperture. This technique improves the wide field imaging
capabilities of both ground-based and space interferometers.


title: Reflection Spectra from Photoionized Accretion Discs

abstract:
  We review recent progress on the modeling and use of reflection spectra from
irradiated and ionized accretion discs. On the computational side, calculations
of reflection spectra from discs with non-uniform density structure have shown
that thermal instabilities can effect the predictions. Ionized reflection
spectra have been used effectively in fitting data of Narrow-Line Seyfert 1
galaxies, and have placed constraints on the strength and shape of soft X-ray
emission lines.


title:
First XMM-Newton results on the Pulsar Wind Nebula in the composite
  supernova remnant G0.9+0.1

abstract:
  We report the results of the XMM-Newton observation of the Pulsar Wind Nebula
(PWN) in the composite supernova remnant G0.9+0.1 located in the Galactic
Center region. Thanks to the sensitivity of the EPIC cameras, we focus on the
first spectral analysis of large and small-scale structures of this PWN using
MOS and PN data in combination. Our spatially resolved spectral analysis at
large-scale offers a clear indication of a softening of the photon index with
distance from the centroid of the nebula (from
Gamma_{core}=1.12^{+0.45}_{-0.48} to Gamma=2.42^{+0.19}_{-0.19}), as observed
in other known X-ray plerions. A spectral analysis of the small-scale
structures in the central region of this PWN, delineates variations of the
spectral index within the arc-like feature observed with Chandra: the eastern
part has a hard photon index (Gamma ~ 1.2 pm 0.5), while the south-west part
has a softer photon index (Gamma ~ 2.8 pm 0.7).


title: Cosmology Rounding the Cape

abstract:
  A survey is made of the present observational status on cosmological
parameters from microwave background anisotropies. I then move to some
non-standard aspect of parameter extraction like quintessence, extra-background
of relativistic particles and variations in fundamental constants.


title: The discovery of X-rays from Venus with Chandra

abstract:
  On January 10 and 13, 2001, Venus was observed for the first time with an
X-ray astronomy satellite. The observation, performed with the ACIS-I and
LETG/ACIS-S instruments on Chandra, yielded data of high spatial, spectral, and
temporal resolution. Venus is clearly detected as a half-lit crescent, with
considerable brightening on the sunward limb. The morphology agrees well with
that expected from fluorescent scattering of solar X-rays in the planetary
atmosphere. The radiation is observed at discrete energies, mainly at the
O-K_alpha energy of 0.53 keV. Fluorescence radiation is also detected from
C-K_alpha at 0.28 keV and, marginally, from N-K_alpha at 0.40 keV. An
additional emission line is indicated at 0.29 keV, which might be the signature
of the C 1s --> pi* transition in CO2 and CO. Evidence for temporal variability
of the X-ray flux was found at the 2.6 sigma level, with fluctuations by
factors of a few times indicated on time scales of minutes. All these findings
are fully consistent with fluorescent scattering of solar X-rays. No other
source of X-ray emission was detected, in particular none from charge exchange
interactions between highly charged heavy solar wind ions and atmospheric
neutrals, the dominant process for the X-ray emission of comets. This is in
agreement with the sensitivity of the observation.


title: Variable Stars in the Field of Young Open Cluster NGC 581

abstract:
  We present results of the search for variable stars in the field of young
open cluster NGC 581. Based on 19 nights of observations, 6 new variable stars
were discovered. Two of them turned out to be eclipsing binary systems. Another
two detected variable stars are most probably of gamma Dor type. During our
observations one of the known Be stars located in our field of view showed
irregular variations of brightness, typical for this class of stars. The sixth
variable star is a pulsating red giant.


title:
A Large Area CCD Camera for the Schmidt Telescope at the Venezuelan
  National Astronomical Observatory

abstract:
  We have designed, constructed and put into operation a large area CCD camera
that covers a large fraction of the image plane of the 1 meter Schmidt
telescope at Llano del Hato in Venezuela. The camera consists of 16 CCD devices
arranged in a 4 x 4 mosaic covering 2.3 degrees x 3.5 degrees of sky. The CCDs
are 2048 x 2048 LORAL devices with 15 micron pixels. The camera is optimized
for drift scan photometry and objective prism spectroscopy. The design
considerations, construction features and performance parameters are described
in the following article.


title:
The information from muon arrival time distributions of high-energy EAS
  as measured with the KASCADE detector

abstract:
  Using the facilities of the KASCADE Central Detector EAS muon arrival time
distributions, observed with reference to the arrival time of the first locally
registered muon, and their correlations with other EAS observables have been
experimentally investigated. The experimental data enable a study of the
sensitivity of such local arrival time distributions to the mass composition of
cosmic rays in the energy region around the knee. For that purpose,
nonparametric multivariate even-by-event analyses have been performed specified
by three different mass groups for an estimate of the mass composition. It
turns out that local muon arrival time distributions display a minor
sensitivity to the mass of the EAS inducing particle, at least for distances
from the shower axis R < 100m. The measurements comprise a subset of all EAS
events registered by KASCADE due to the observation conditions of the arrival
time distributions, with a threshold of the muon energy E = 2.4 GeV and a
minimum multiplicity n for being accepted in the observed data samples. By
studying the event acceptance in the registered samples on basis of Monte Carlo
simulations a test of the consistency of the Monte Carlo simulations with the
data is enabled. Within the present uncertainties the results of such a test
show a remarkable agreement of the experimental findings with the Monte Carlo
simulations, using the QGSJET model as generator of the high-energy hadronic
interactions.


title: The X-ray Halo of GX 13+1

abstract:
  We present observations of the X-ray halo around the LMXB GX 13+1 from the
Chandra X-ray telescope. The halo is caused by scattering in interstellar dust
grains, and we use it to diagnose the line-of-sight position, size
distribution, and density of the grains. Using the intrinsic energy resolution
of Chandra's ACIS CCDs and the recent calibration observation of the Chandra
point spread function (PSF), we were able to extract the halo fraction as a
function of energy and off-axis angle. We define a new quantity, the ``halo
coefficient,'' or the total halo intensity relative to the source at 1 keV, and
measure it to be $1.5^{+0.5}_{-0.1}$ for GX 13+1. We find a relationship
between this value and the dust size, density, and hydrogen column density
along the line of sight to GX 13+1. We also conclude that our data does not
agree with ``fluffy'' dust models that earlier X-ray halo observations have
supported, and that models including an additional large dust grain population
are not supported by these data.


title: The AMANDA-II Neutrino-Telescope

abstract:
  The AMANDA-II telescope at the South Pole is constructed of 677 optical
modules at 19 strings. We describe the observation of atmospheric neutrinos
with the first stage 10-string detector AMANDA-B10, which establishes AMANDA as
a working neutrino telescope. The expected performance for the AMANDA-II
detector is discussed.


title:
The relation between the mid-infrared emission and Black Hole Mass in
  Active Galactic Nuclei: A direct way to probe black hole growth?

abstract:
  We use a large, heterogeneous sample of local active galactic nuclei (AGN)
that includes Seyfert 1s, Seyfert 2s and PG quasars to investigate for the
first time the relation between black hole mass (M_BH) and mid-infrared nuclear
emission. We find a clear relation between M_BH and the 10 micron nuclear
luminosity for these local AGNs. There are no significant differences between
type 1 and type 2 objects, implying that the reprocessing of the 10 micron
nuclear emission is not severely affected by geometric and optical depth
effects. We also confirm that M_BH is related to the 2-10keV X-ray luminosity,
but only for the Compton thin galaxies. We present a theoretical basis for
these empirical relations and discuss possible reasons for the observed
scatter. Our results show that rest-frame 10 micron and hard X-ray luminosities
(especially the former, which is applicable to all AGN types) can be powerful
tools for conducting a census of black hole masses at high redshift and for
probing their cosmological evolution.


title:
Interstellar Scintillation Velocities of a Relativistic Binary PSR
  B1534+12 and Three Other Millisecond Pulsars

abstract:
  We present interstellar scintillation velocity measurements for four
millisecond pulsars obtained from long-term monitoring observations with the
Arecibo radio telescope at 430 MHz. We also derive explicit expressions that
relate the measured scintillation velocity to the effective transverse velocity
responsible for the motion of the diffraction pattern for both binary and
solitary pulsars. For B1257+12, B1534+12, J1640+2224, and J1713+0747 we derive
velocity estimates of 197, 192, 38, and 82 km/s, respectively. These values are
in good agreement with proper motion measurements for the four pulsars. For PSR
B1534+12, we use the ISS velocity dependence on orbital phase to determine the
longitude of the ascending node (Omega) of the pulsar's orbit and to derive an
estimate of the effective scattering screen location. The two possible values
of Omega are 70+/-20 and 290+/-20 degrees and the approximate screen location
is 630+/-200 pc with the assumed pulsar distance of 1.1 kpc.


title: Fixed-delay Interferometry for Doppler Extra-solar Planet Detection

abstract:
  We present a new technique based on fixed-delay interferometry for high
throughput, high precision and multi-object Doppler radial velocity (RV)
surveys for extra-solar planets. The Doppler measurements are conducted through
monitoring the stellar fringe phase shifts of the interferometer. High Doppler
sensitivity is achieved through optimizing the optical delay in the
interferometer and reducing photon noise by measuring multiple fringes over a
broadband. This broadband operation is performed through coupling the
interferometer with a low to medium resolution post-disperser. The total
Doppler sensitivity of this approach is, in theory, independent of dispersing
power of the post-disperser, which allows development of new generation RV
machines with much reduced size, high stability and low cost compared to
echelles. This technique has the potential to improve RV survey efficiency by
2-3 orders of magnitude over cross-dispersed echelle spectroscopy approach to
allow a full sky RV survey for planets once the instrument is operated as a
multi-object instrument and optimized for high throughput.
  The simple interferometer response potentially allows this technique to be
operated at other wavelengths independent of popular iodine reference sources
to search for planets around early type stars, white dwarfs, and M, L and T
dwarfs for the first time.


title: Discovery of an Edge-On Disk in the MBM 12 Young Association

abstract:
  We report the discovery of a spatially-resolved edge-on protoplanetary disk
in the ~2-Myr-old MBM 12 young association. Our near-infrared images of LkHa
263C (MBM 12A 3C), obtained with the Hokupa'a adaptive optics system on the
Gemini North telescope, clearly show two elongated reflection nebulosities
separated by a dark lane, a morphology well-matched by scattered light models
of an optically thick (at near-infrared wavelengths) edge-on disk. An optical
spectrum of the scattered light nebulosity obtained with the Keck II telescope
exhibits a spectral type of M0 +/- 0.5 (T_eff = 3850 +/- 100 K) for the central
star and contains H_alpha and forbidden emission lines, which may indicate the
presence of a jet. The absence of a near-infrared point source implies A_K >
9.5 toward the unseen central star. The disk is flared and has a radius of ~150
AU (at a distance of 275 pc) and an inclination of 87 degrees. The aspect ratio
of the model disk in the J-band is 0.72. There is possible evidence for dust
settling to the disk midplane. LkHa 263C is 4.115" from the 0.415" binary LkHa
263 A and B (MBM 12A 3A and 3B), which is itself 15.5" from LkHa 262 (MBM 12A
2). Thus, LkHa 263C may be the first disk to be clearly resolved around an
individual star in a young quadruple system. The detection of a faint edge-on
disk near a bright star demonstrates both the high angular resolution and the
high sensitivity that can be achieved with adaptive optics imaging on large
telescopes.


title:
Future Galaxy Cluster Surveys: The Effect of Theory Uncertainty on
  Constraining Cosmological Parameters

abstract:
  Using the Fisher matrix formalism, we quantitatively investigate the
constraints on a 10 dimensional space of cosmological parameters which may be
obtained with future cluster surveys. We explore the dependence of the Omega_m
constraint on both angular coverage and depth of field. We show that in each
case there is a natural cutoff beyond which the constraints on Omega_m do not
significantly improve. We also investigate the sensitivity of the constraints
to changes in our knowledge of the Mass-Temperature (M-T) relation by including
its normalization and scatter as two of the parameters in the Fisher matrix. To
make our analysis more realistic, we have added, as priors, the Fisher matrices
from hypothetical supernova and CMB experiments. We find that X-ray cluster
surveys actually help to constrain the M-T relation, and explore the
implications of this result.


title: A Highly Ordered Faraday-Rotation Structure in the Interstellar Medium

abstract:
  We describe a Faraday-rotation structure in the Interstellar Medium detected
through polarimetric imaging at 1420 MHz from the Canadian Galactic Plane
Survey (CGPS). The structure, at l=91.8, b=-2.5, has an extent of ~2 degree,
within which polarization angle varies smoothly over a range of ~100 degree.
Polarized intensity also varies smoothly, showing a central peak within an
outer shell. This region is in sharp contrast to its surroundings, where
low-level chaotic polarization structure occurs on arcminute scales. The
Faraday-rotation structure has no counterpart in radio total intensity, and is
unrelated to known objects along the line of sight, which include a Lynds
Bright Nebula, LBN 416, and the star cluster M39 (NGC7092). It is interpreted
as a smooth enhancement of electron density. The absence of a counterpart,
either in optical emission or in total intensity, establishes a lower limit to
its distance. An upper limit is determined by the strong beam depolarization in
this direction. At a probable distance of 350 +/- 50 pc, the size of the object
is 10 pc, the enhancement of electron density is 1.7 cm-3, and the mass of
ionized gas is 23 M_sun. It has a very smooth internal magnetic field of
strength 3 microG, slightly enhanced above the ambient field. G91.8-2.5 is the
second such object to be discovered in the CGPS, and it seems likely that such
structures are common in the Magneto-Ionic Medium.


title: Thermal Evolution and Light Curves of Young Bare Strange Stars

abstract:
  The cooling of a young bare strange star is studied numerically by solving
the equations of energy conservation and heat transport for both normal and
superconducting strange quark matter inside the star. We show that the thermal
luminosity from the strange star surface, due to both photon emission and e+e-
pair production, may be orders of magnitude higher than the Eddington limit,
for about one day for normal quark matter but possibly for up to a hundred
years for superconducting quark matter, while the maximum of the photon
spectrum is in hard X-rays with a mean energy of ~ 100 keV or even more. This
differs both qualitatively and quantitatively from the photon emission from
young neutron stars and provides a definite observational signature for bare
strange stars. It is shown that the energy gap of superconducting strange quark
matter may be estimated from the light curves if it is in the range from ~ 0.5
MeV to a few MeV.


title: Temperature Variations from HST Imagery and Spectroscopy of NGC 7009

abstract:
  We present new HST/WFPC2 imagery and STIS long-slit spectroscopy of the
planetary nebula NGC 7009. The primary goal was to obtain high spatial
resolution of the intrinsic line ratio [O III] 4364/5008 and thereby evaluate
the electron temperature (T_e) and the fractional mean-square T_e variation
(t_A^2) across the nebula. The WFPC2 T_e map is rather uniform; almost all
values are between 9000 - 11,000 K, with the higher T_e's closely coinciding
with the inner He^++-zone. The results indicate very small values - <~ 0.01 -
for t_A^2 throughout. Our STIS data allow an even more direct determination of
T_e and t_A^2, albeit for a much smaller area than with WFPC2. We present
results from binning the data along the slit into tiles that are 0.5'' square
(matching the slit width). The average [O III] temperature using 45 tiles
(excluding the central star and STIS fiducial bars) is 10,139 K; t_A^2 is
0.0035. The measurements of T_e reported here are an average along each line of
sight. Therefore, despite finding remarkably low t_A^2, we cannot completely
rule out temperature fluctuations along the line of sight as the cause of the
large abundance discrepancy between heavy element abundances inferred from
collisionally excited emission lines compared to those derived from
recombination lines.


title:
Time evolution of the unstable two-fluid density fluctuations in
  Robertson-Walker Universes

abstract:
  We consider density fluctuations of a two-fluid model consisting of hydrogen
plasma and radiation prior to the cosmic hydrogen recombination. As
investigation method that of the dispersion relations is applied, which have
been derived from the general-relativistic sound-wave equations taking into
account the coupling between plasma and radiation carefully. We obtain growing
unstable acoustic modes within the mass range 2 \cdot 10^6 M_\odot < M < 6
\cdot 10^{12} M_\odot. In a second step the coupled differential equations for
the amplitudes of the unstable modes are integrated numerically with respect to
time where the integration extends from the initial time prior to the hydrogen
recombination up to the present time. We find a significant increase of the
amplitudes up to 4 orders of magnitude, if the Universe is described by a
cosmological model with a positive cosmological constant (\Lambda \simeq 2,2
\cdot 10^{-56} {cm}^{-2}) and a positive curvature (Lema\^\itre-Universe)
without an essential amount of cold dark matter. We conclude that the existence
of galaxies confirm these statements.


title: An HST study of three very faint GRB host galaxies

abstract:
  As part of the HST/STIS GRB host survey program we present the detection of
three faint gamma-ray burst (GRB) host galaxies based on an accurate
localisation using ground-based data of the optical afterglows (OAs). A common
property of these three hosts is their extreme faintness. The location at which
GRBs occur with respect to their host galaxies and surrounding environments are
robust indicators of the nature of GRB progenitors. The bursts studied here are
among the four most extreme outliers, in terms of relative distance from the
host center, in the recent comprehensive study of Bloom et al. 2002. We obtain
a revised and much higher probability that the galaxies identified as hosts
indeed are related to the GRBs (P(n_chance)=0.78, following Bloom et al. 2002),
thereby strengthening the conclusion that GRBs are preferentially located in
star-forming regions in their hosts. Apart from being faint, the three hosts
consist of multiple structures, indicative of merging and active
star-formation. For one of the hosts, GRB 980329, we estimate a photometric
redshift of z~3.5.


title:
Pulsation of the Delta Scuti star Theta2 Tau: New multisite photometry
  and modelling of instability

abstract:
  The results of a multisite photometric campaign of Theta2 Tau are reported.
This binary system consists of evolved and main-sequence A stars inside the
instability strip. The 12th Delta Scuti Network campaign included 152 hours of
high-precision photometry obtained at four observatories. This leads to the
derivation of 11 frequencies of pulsation in the 10.8 to 14.6 c/d range. These
frequencies confirm the results from previous Earth-based (1982-1986) as well
as satellite (2000) photometry,although amplitude variability on a time scale
of several years is present. We show that at least two high frequencies (26.18
and 26.73 c/d are also present in Theta 2 Tau. Arguments are given that these
high frequencies originate in the main-sequence companion and are not
combination frequencies, fi+fj, from the primary. Models for both the primary
and the secondary components were checked for the instability against radial
and nonradial oscillations. All hot models of the primary with Teff > 8000K are
stable in the observed frequency range. The best fit between the theoretical
and observed frequency ranges is achieved by models with Teff approximately
equal to 7800K (or slightly higher), in agreement with photometric
calibrations. The instability range spans two or three radial orders in the
range p4 to p6 for radial modes. Post-main-sequence models (with or without
overshooting) are preferable for the primary, but main-sequence models with
overshooting cannot be excluded. For the less luminous secondary component the
instability range is wider and spans 5 to 7 radial orders from p2 to p8. The
observed frequencies lie around radial modes p5 to p6. The main uncertainties
of these results are caused by a simple treatment of the convective flux in the
hydrogen ionization zone.


title: Correcting for lensing bias in the Hubble diagram

abstract:
  Gravitational lensing will cause a dispersion in the Hubble diagram for high
redshift sources. This effect will introduce a bias in the cosmological
parameter determination using the distance-redshift relation for Type Ia
supernovae. In this note we show how one can diagnose and correct for this bias
when doing precision cosmology with supernovae.


title: Vertical structure models of T Tauri and Herbig Ae/Be disks

abstract:
  In this paper we present detailed models of the vertical structure
(temperature and density) of passive irradiated circumstellar disks around T
Tauri and Herbig Ae/Be stars. In contrast to earlier work, we use full
frequency- and angle-dependent radiative transfer instead of the usual moment
equations. We find that this improvement of the radiative transfer has strong
influence on the resulting vertical structure of the disk, with differences in
temperature as large as 70 %. However, the spectral energy distribution (SED)
is only mildly affected by this change. In fact, the SED compares reasonably
well with that of improved versions of the Chiang & Goldreich (CG) model. This
shows that the latter is a reasonable model for the SED, in spite of its
simplicity. It also shows that from the SED alone, little can be learned about
the vertical structure of a passive circumstellar disk. The molecular line
emission from these disks is more sensitive to the vertical temperature and
density structure, and we show as an example how the intensity and profiles of
various CO lines depend on the adopted disk model. The models presented in this
paper can also serve as the basis of theoretical studies of e.g. dust
coagulation and settling in disks.


title: Gravitational Microlensing in NUT Space

abstract:
  We study the theoretical signature of magnetic masses on the light curve of
gravitational microlensing effect in NUT space. The light curves for
microlensing events in NUT space are presented and contrasted with those due to
lensing produced by normal matter. In the next step, associating magnetic mass
to massive astrophysical compact objects (MACHOs), we try to see its effect on
the light curves of microlensing candidates observered by the MACHO group.
Presence or absence of this feature in the observed microlensing events can
shed light on the question of the existence of magnetic masses in the Universe.


title:
Timing of Millisecond Pulsars in NGC 6752: Evidence for a High
  Mass-to-Light Ratio in the Cluster Core

abstract:
  Using pulse timing observations we have obtained precise parameters,
including positions with about 20 mas accuracy, of five millisecond pulsars in
NGC 6752. Three of them, located relatively close to the cluster center, have
line-of-sight accelerations larger than the maximum value predicted by the
central mass density derived from optical observation, providing dynamical
evidence for a central mass-to-light ratio >~ 10, much higher than for any
other globular cluster. It is likely that the other two millisecond pulsars
have been ejected out of the core to their present locations at 1.4 and 3.3
half-mass radii, respectively, suggesting unusual non-thermal dynamics in the
cluster core.


title: Faint star counts in the near-infrared

abstract:
  We discuss near-infrared star counts at the Galactic pole with a view to
guiding the NGST and ground-based NIR cameras. Star counts from deep K-band
images from the CFHT are presented, and compared with results from the 2MASS
survey and some Galaxy models. With appropriate corrections for detector
artifacts and galaxies, the data agree with the models down to K~18, but
indicate a larger population of fainter red stars. There is also a significant
population of compact galaxies that extend to the observational faint limit of
K=20.5. Recent Galaxy models agree well down to K$\sim$19, but diverge at
fainter magnitudes.


title: High resolution spectroscopy of ultracool M dwarfs

abstract:
  (abridged) We present high-resolution echelle spectroscopy of a
photometricaly-selected sample if thirty-nine dwarfs with spectral types
between M6.5 and L0.5. Two stars, 2MASSI 0253202+271333 and 2MASSW
0952219-192431, are double-lined spectroscopic binaries. We have used our
observations to search for Li I 6708 A absorption, characteristic of
sub-stellar mass; estimate the level of chromospheric activity through
measurement of H-alpha emission fluxes; measure rotational velocities via line
broadening; and determine radial velocities and Galactic space motions. Two
dwarfs have strong lithium absorption, the previously-known brown dwarf, LP
944-20, and 2MASSI J0335020+234235, which we identify as a probable 0.06 M_sun
brown dwarf, age ~1 Gyr. We have investigated the prospect of using the
observed frequency of lithium absorption amongst ultracool M dwarfs (M7 to
M9.5) as a probe of the initial mass function. The available observations are
difficult to reconcile with Salpeter-like power-law mass functions (alpha > 2)
for masses below 0.1M_Sun. A comparison between the rotational velocities and
-alpha fluxes shows no evidence for significant correlation. Velocity
dispersions are significantly lower than those measured for nearby M dwarfs,
but show remarkable similarity to results for earlier-type emission-line (dMe)
dwarfs. The latter are generally assigned ages of less than ~3 Gyrs.


title:
ISO observations of Hickson Compact Group 31 with the central Wolf-Rayet
  galaxy NGC 1741

abstract:
  Hickson Compact Group (HCG) 31, consisting of the Wolf-Rayet galaxy NGC 1741
and its irregular dwarf companions, was observed using the Infrared Space
Observatory. The deconvolved ISOCAM maps of the galaxies using the 7.7 micron
and 14.3 micron (LW6 and LW3) filters are presented, along with ISOPHOT
spectrometry of the central starburst region of NGC 1741 and the nucleus of
galaxy HCG 31A. Strong mid-IR emission was detected from the central burst in
NGC 1741, along with strong PAH features and a blend of features including [S
IV] at 10.5 micron. The 14.3/6.75 micron flux ratio, where the 6.75 micron flux
was synthesized from the PHT-S spectrum, and 14.3/7.7 micron flux ratios
suggest that the central burst within NGC 1741 may be moving towards the
post-starburst phase. Diagnostic tools including the ratio of the integrated
PAH luminosity to the 40 to 120 micron infrared luminosity and the far-infrared
colours reveal that despite the high surface brightness of the nucleus, the
properties of NGC 1741 can be explained in terms of a starburst and do not
require the presence of an AGN. The Tycho catalogue star TYC 04758-466-1, with
m$_{V}$ = 11.3 and spectral type F6, was detected at 7.7 and 14.3 microns.


title:
Finite size scaling in the solar wind magnetic field energy density as
  seen by WIND

abstract:
  Statistical properties of the interplanetary magnetic field fluctuations can
provide an important insight into the solar wind turbulent cascade. Recently,
analysis of the Probability Density Functions (PDF) of the velocity and
magnetic field fluctuations has shown that these exhibit non-Gaussian
properties on small time scales while large scale features appear to be
uncorrelated. Here we apply the finite size scaling technique to explore the
scaling of the magnetic field energy density fluctuations as seen by WIND. We
find a single scaling sufficient to collapse the curves over the entire
investigated range. The rescaled PDF follow a non Gaussian distribution with
asymptotic behavior well described by the Gamma distribution arising from a
finite range Levy walk. Such mono scaling suggests that a Fokker-Planck
approach can be applied to study the PDF dynamics. These results strongly
suggest the existence of a common, nonlinear process onthe time scale up to ~26
hours.


title:
Relativistic simulations of rotational core collapse. I. Methods,
  initial models, and code tests

abstract:
  We describe an axisymmetric general relativistic code for rotational core
collapse. The code evolves the coupled system of metric and fluid equations
using the ADM 3+1 formalism and a conformally flat metric approximation of the
Einstein equations. The relativistic hydrodynamics equations are formulated as
a first-order flux-conservative hyperbolic system and are integrated using
high-resolution shock-capturing schemes based on Riemann solvers. We assess the
quality of the conformally flat metric approximation for relativistic core
collapse and present a comprehensive set of tests which the code successfully
passed. The tests include relativistic shock tubes, the preservation of the
rotation profile and of the equilibrium of rapidly and differentially rotating
neutron stars (approximated as rotating polytropes), spherical relativistic
core collapse, and the conservation of rest-mass and angular momentum in
dynamic spacetimes. The application of the code to relativistic rotational core
collapse, with emphasis on the gravitational waveform signature, is presented
in an accompanying paper.


title:
Relativistic simulations of rotational core collapse. II. Collapse
  dynamics and gravitational radiation

abstract:
  We have performed hydrodynamic simulations of relativistic rotational
supernova core collapse in axisymmetry and have computed the gravitational
radiation emitted by such an event. Details of the methodology and of the
numerical code have been given in an accompanying paper. We have simulated the
evolution of 26 models in both Newtonian and relativistic gravity. Our
simulations show that the three different types of rotational supernova core
collapse and gravitational waveforms identified in previous Newtonian
simulations (regular collapse, multiple bounce collapse, and rapid collapse)
are also present in relativistic gravity. However, rotational core collapse
with multiple bounces is only possible in a much narrower parameter range in
relativistic gravity. The relativistic models cover almost the same range of
gravitational wave amplitudes and frequencies as the corresponding Newtonian
ones. For a given model, relativistic gravity can cause a large increase of the
characteristic signal frequency of up to a factor of five, which may have
important consequences for the signal detection. The gravitational wave signals
obtained in our study are within the sensitivity range of the first generation
laser interferometer detectors if the source is located within the Local Group.


title:
3D eclipse mapping in AM Herculis systems - `Genetically modified
  fireflies'

abstract:
  In order to map the 3-dimensional location and shape of the emission
originating within the accretion stream in AM Her systems, we have investigated
the possibilities of relaxing the hitherto-applied constraint of a
predetermined stream trajectory in modelling the eclipse profiles. We use
emission points which can be located anywhere in the Roche lobe of the primary,
together with a regularisation term which favours any curved stream structure,
connected at the secondary and white dwarf primary. Our results show that,
given suitable regularisation constraints, such inversion is feasible. We
investigate the effect of removing the regularisation term, and also the
sensitivity of the fit to input parameters such as inclination.


title:
The case of PSR J1911-5958A in the outskirts of NGC 6752: signature of a
  black hole binary in the cluster core?

abstract:
  We have investigated different scenarios for the origin of the binary
millisecond pulsar PSR J1911-5958A in NGC 6752, the most distant pulsar
discovered from the core of a globular cluster to date. The hypothesis that it
results from a truly primordial binary born in the halo calls for
accretion-induced collapse and negligible recoil speed at the moment of neutron
star formation. Scattering or exchange interactions off cluster stars are not
consistent with both the observed orbital period and its offset position. We
show that a binary system of two black holes with (unequal) masses in the range
of 3-100 solar masses can live in NGC 6752 until present time and can have
propelled PSR J1911-5958A into an eccentric peripheral orbit during the last ~1
Gyr.


title:
A new Monte Carlo code for star cluster simulations: II. Central black
  hole and stellar collisions

abstract:
  We have recently written a new code to simulate the long term evolution of
spherical clusters of stars. It is based on the pioneering Monte Carlo scheme
proposed by Henon in the 70's. Our code has been devised in the specific goal
to treat dense galactic nuclei. After having described how we treat relaxation
in a first paper, we go on and include further physical ingredients that are
mostly pertinent to galactic nuclei, namely the presence of a central (growing)
black hole (BH) and collisions between MS stars. Stars that venture too close
to the BH are destroyed by the tidal field. This process is a channel to feed
the BH and a way to produce accretion flares. Collisions between stars have
often been proposed as another mechanism to drive stellar matter into the
central BH. To get the best handle on the role of this process in galactic
nuclei, we include it with unpreceded realism through the use of a set of more
than 10000 collision simulations carried out with a SPH (Smoothed Particle
Hydrodynamics) code. Stellar evolution has also been introduced in a simple
way, similar to what has been done in previous dynamical simulations of
galactic nuclei. To ensure that this physics is correctly simulated, we
realized a variety of tests whose results are reported here. This unique code,
featuring most important physical processes, allows million particle
simulations, spanning a Hubble time, in a few CPU days on standard personal
computers and provides a wealth of data only rivalized by N-body simulations.


title: Bulk QCD Thermodynamics and Sterile Neutrino Dark Matter

abstract:
  We point out that the relic densities of singlet (sterile) neutrinos of
interest in viable warm and cold dark matter scenarios, depend on the
characteristics of the QCD transition in the early universe. In the most
promising of these dark matter scenarios the production of the singlets occurs
at or near the QCD transition. Since production of the singlets, their
dilution, and the disappearance of weak scatterers occur simultaneously, we
calculate these processes contemporaneously to obtain accurate predictions of
relic sterile neutrino mass density. Therefore, a determination of the mass and
superweak mixing of the singlet neutrino through, for example, its radiative
decay, along with a determination of its contribution to the critical density,
can provide insight into the finite-temperature QCD transition.


title: The r-Process and Chronometers

abstract:
  We present detailed abundance observations of the metal-poor ([Fe/H] = --2.0)
Galactic halo star BD+17 3248. We have detected gold in this star, for the
first time in any halo star. We also detected a weak line at 3859.60 A in the
spectrum of BD+17 3248 that we tentatively identify with uranium. This would be
only the second such detection of this radioactive element in any metal-poor
halo stars. Similarly to the case of CS 22892--052, the heavier n-capture
elements (Z >= 56) fall on the scaled solar system r-process abundance curve,
while the elements with Z = 40--50 in BD+17 3248 fall below that same solar
curve. Employing the newly detected Th, U and third r-process peak element
(e.g., Pt, Ir) abundances, chronometric age estimates have been made for BD+17
3248. The average value of the various chronometric pairs suggests an age of
13.8 +/- 4 Gyr for this star, consistent, within error limits, with other
chronometric age determinations for metal-poor Galactic halo stars.


title: Constraints on Omega_m and sigma_8 from weak lensing in RCS fields

abstract:
  We have analysed 53 square degrees of imaging data from the Red-Sequence
Cluster Survey (RCS), and measured the excess correlations in the shapes of
galaxies on scales out to ~1.5 degrees. We separate the signal into an ``E''-
(lensing) and ``B''-mode (systematics), which allows us to study residual
systematics. On scales larger than 10 arcminutes, we find no ``B''-mode. On
smaller scales we find a small, but significant ``B''-mode. This signal is also
present when we select a sample of bright galaxies. These galaxies are rather
insensitive to observational distortions, and we therefore conclude that the
oberved ``B''-mode is likely to be caused by intrinsic alignments. We therefore
limit the cosmic shear analysis to galaxies with 22<R_C<24. We derive joint
constraints on Omega_m and sigma_8, by marginalizing over Gamma, Omega_Lambda
and the source redshift distribution, using different priors. We obtain a
conservative constraint of $\sigma_8=0.45^{+0.09}_{-0.12} \Omega_m^{-0.55}$
(95% confidence). A better constraint is derived when we use Gaussian priors
redshift distribution. For this choice of priors, we find
$\sigma_8=(0.46^{+0.05}_{-0.07})\Omega_m^{-0.52}$ (95% confidence). Using our
setof Gaussian priors, we find that we can place a lower bound on Gamma:
Gamma>0.1+0.16\Omega_m$ (95% confidence). Comparison of the RCS results with
three other recent cosmic shear measurements shows excellent agreement. The
current weak lensing results are also in good agreement with CMB measurements,
when we allow the reionization optical depth tau and the spectral index n_s to
vary. We present a simple demonstration of how the weak lensing results can be
used as a prior in the parameter estimation from CMB measurements to derive
constraints on the reionization optical depth tau. (abridged)


title: Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6388

abstract:
  We have undertaken a search for variable stars in the metal-rich globular
cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables
were found in this survey, increasing the total number of variables found near
NGC 6388 to ~57. A significant number of the variables are RR Lyrae (~14), most
of which are probable cluster members. The periods of the fundamental mode RR
Lyrae are shown to be unusually long compared to metal-rich field stars. The
existence of these long period RRab stars suggests that the horizontal branch
of NGC 6388 is unusually bright. This implies that the metallicity-luminosity
relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388
are indeed metal-rich. We consider the alternative possibility that the stars
in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids
were also found. If they are members of the cluster, NGC 6388 would be the most
metal-rich globular cluster to contain Population II Cepheids. The mean V
magnitude of the RR Lyrae is found to be 16.85+/-0.05 resulting in a distance
of 9.0 to 10.3 kpc, for a range of assumed values of <M_V> for RR Lyrae. We
determine the reddening of the cluster to be E(B-V)=0.40+/-0.03 mag, with
differential reddening across the face of the cluster. We discuss the
difficulty in determining the Oosterhoff classification of NGC 6388 and NGC
6441 due to the unusual nature of their RR Lyrae, and address evolutionary
constraints on a recent suggestion that they are of Oosterhoff type II.


title: ESI, a new Keck Observatory echellette spectrograph and imager

abstract:
  The Echellette Spectrograph and Imager (ESI) is a multipurpose instrument
which has been delivered by the Instrument Development Laboratory of Lick
Observatory for use at the Cassegrain focus of the Keck II telescope. ESI saw
first light on August 29, 1999. ESI is a multi-mode instrument that enables the
observer to seamlessly switch between three modes during an observation. The
three modes of ESI are: An R=13,000-echellette mode; Low-dispersion prismatic
mode; Direct imaging mode. ESI contains a unique flexure compensation system
which reduces the small instrument flexure to negligible proportions.
Long-exposure images on the sky show FWHM spot diameters of 34 microns (0.34")
averaged over the entire field of view. These are the best non-AO images taken
in the visible at Keck Observatory to date. Maximum efficiencies are measured
to be 28% for the echellette mode and greater than 41% for low-dispersion
prismatic mode including atmospheric, telescope and detector losses. In this
paper we describe the instrument and its development. We also discuss the
performance-testing and some observational results.


title: Classifications of the Host Galaxies of Supernovae

abstract:
  Classifications on the DDO system are given for the host galaxies of 177
supernovae (SNe) that have been discovered since 1997 during the course of the
Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope.
Whereas SNe Ia occur in all galaxy types, it is found, at a high level of
statistical confidence, that SNe Ib, Ic, and II are strongly concentrated in
late-type galaxies. However, attention is drawn to a possible exception
provided by SN 2001I. This SN IIn occurred in the E2 galaxy UGC 2836, which was
not expected to harbor a massive young supernova progenitor.


title: Magnetorotational Instability in Liquid Metal Couette Flow

abstract:
  Despite the importance of the magnetorotational instability (MRI) as a
fundamental mechanism for angular momentum transport in magnetized accretion
disks, it has yet to be demonstrated in the laboratory. A liquid sodium
alpha-omega dynamo experiment at the New Mexico Institute of Mining and
Technology provides an ideal environment to study the MRI in a rotating metal
annulus (Couette flow). A local stability analysis is performed as a function
of shear, magnetic field strength, magnetic Reynolds number, and turbulent
Prandtl number. The later takes into account the minimum turbulence induced by
the formation of an Ekman layer against the rigidly rotating end walls of a
cylindrical vessel. Stability conditions are presented and unstable conditions
for the sodium experiment are compared with another proposed MRI experiment
with liquid gallium. Due to the relatively large magnetic Reynolds number
achievable in the sodium experiment, it should be possible to observe the
excitation of the MRI for a wide range of wavenumbers and further to observe
the transition to the turbulent state.


title:
Origin of the "Disk-Line" Feature in the X-Ray Energy Spectrum of a
  Seyfert Galaxy, NGC4151

abstract:
  We have studied the origin of the broad and skewed feature at 4.5-7.5 keV in
the energy spectra of NGC4151 using the ASCA and RXTE data. The feature
consists of a narrow peak at 6.4 keV and a broad wing extended between 4.5-7.5
keV. An analysis of the long-term variations revealed that the feature became
variable only on a time scale longer than 1.5x10^6 s. Through a comparison with
the continuum variabilities, we found that the emission region of the excess
flux at 4.5-7.5 keV has an extent of 10^17 cm. The broad and skewed feature at
4.5-7.5 keV may be explained by the so-called ``disk-line'' model. If so, the
size of the line-emitting region, 10^17 cm, should be equal to several or
ten-times the Schwarzschild radius of the central black hole. This results in a
black hole mass of 10^11 solar mass, which may be too large for NGC4151. We
propose an alternative explanation for the broad and skewed feature, i.e. a
``reflection'' model, which can also reproduce the overall energy spectra very
well. In this model, cold matter with a sufficiently large column density is
irradiated by X-rays to produce a reflected continuum, which constitutes the
broad wing of the feature, and narrow fluorescent lines. The equivalent width
of the iron fluorescent line (~2 keV) and the upper limit of its width (sigma <
92 eV) are also consistent with this model. From these results and
considerations, we conclude that the ``disk-line'' model has difficulty to
explain the spectral variations of NGC4151, and the reflection model is more
plausible.


title:
Dynamical condition of neutral hydrogen envelopes of dwarf galaxies and
  their possible morphological evolution

abstract:
  We investigate the star-formation history of gas-rich dwarf galaxies, taking
account of the dynamical evolution of their neutral hydrogen (H{\sc i})
envelope. Gas-rich dwarfs are classified into blue compact dwarfs (BCDs) and
dwarf irregulars (dIrrs). In this paper, their H{\sc i} envelope is clearly
shown not to be blown away by their stellar feedback. This is concluded since
the observed star-formation rate (SFR) of gas-rich dwarfs is generally smaller
than a critical SFR, $\psi_{\rm crit}$, at which stellar feedback accelerates
the H{\sc i} envelope to the escape velocity. From this standpoint and the
chemical property of sample BCDs, we suggest two possibilities; (1) The H{\sc
i} gas in the envelope of BCDs is consumed to fuel their star-formation; and
(2) BCDs have a similar star-formation history. We also discuss morphological
evolution among dwarf galaxies. As long as gas-rich dwarfs are isolated, it is
difficult for them to evolve into dwarf ellipticals (dEs). When the H{\sc i}
envelope in gas-rich dwarfs is consumed in subsequent star-formation, a
morphological exchange between BCDs and dIrrs is still expected, consistent
with previous studies. If the SFR of gas-rich dwarfs was much higher than
$\psi_{\rm crit}$ in the past, interestingly, an evolutionary scenario from dEs
to gas-rich dwarfs is possible.


title: Pulsed radiation from neutron star winds

abstract:
  The radiation of a pulsar wind is computed assuming that at roughly 10 to 100
light cylinder radii from the star, magnetic energy is dissipated into particle
energy. The synchrotron emission of heated particles appears periodic, with, in
general, both a pulse and an interpulse. The predicted spacing agrees well with
the Crab and Vela pulse profiles.Using parameters appropriate for the Crab
pulsar (magnetisation parameter at the light cylinder $\sigma=6\times10^4$,
Lorentz factor $\Gamma=250$) agreement is found with the observed total pulsed
luminosity. This suggests that the high-energy pulses from young pulsars
originate not in the corotating magnetosphere within the light cylinder (as in
all other models) but from the radially directed wind well outside it.


title:
Subarcsec emission in Seyfert galaxies: the nuclear component in the L-
  and M-bands

abstract:
  We present deep L- and M- band imaging with ISAAC on the ESO VLT with
unprecedented spatial resolution of the nearby Seyfert 2 galaxies NGC 7496 and
NGC 7582 and the Seyfert 1 galaxy NGC 7213. The unresolved nuclear component
dominates the emission within the central 90 pc region, while the host galaxy
accounts for up to 50 % of the integrated emission at both wavelengths within
the detected sizes of of 1 kpc in the L-band and 0.5 kpc in the M-band. The
overall morphology of the extended component follows the general isophote
pattern defined by the near-infrared continuum of the galaxies. However, the
central 300 pc regions show much more ordered elliptical isophotes than in the
near-infrared. In particular, emission in the L- and M-bands shows well defined
central point sources in the two Seyfert 2s.


title:
Associated Absorption Lines in the Radio-Loud Quasar 3C 351:
  Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope

abstract:
  As one of the most luminous radio-loud quasars showing intrinsic ultraviolet
(UV) and X-ray absorption, 3C 351 provides a laboratory for studying the
kinematics and physical conditions of such ionized absorbers. We present an
analysis of the intrinsic absorption lines in the high-resolution ($\sim$ 7
km/s) far-UV spectrum which was obtained from observations with the Space
Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope
(HST). The spectrum spans wavelengths from 1150 \AA to 1710 \AA, and shows
strong emission lines from O VI and Ly$\alpha$. Associated absorption lines are
present on the blue wings of the high-ionization emission doublets O VI
$\lambda\lambda$ 1032,1038 and N V $\lambda\lambda$ 1238,1242, as well as the
Lyman lines through Ly$\epsilon$. These intrinsic absorption features are
resolved into several distinct kinematic components, covering rest-frame
velocities from -40 to -2800 km/s, with respect to the systemic redshift of
$z_{em}=0.3721$. For the majority of these absorption line regions, strong
evidence of partial covering of both the background continuum source and the
BELR is found, which supports the intrinsic absorption origin and rules out the
possibility that the absorption arises in some associated cluster of galaxies.
The relationship between the far-UV absorbers and X-ray `warm' absorbers are
studied with the assistance of photoionization models. Most of the UV
associated absorption components have low values of the ionization parameter
and total hydrogen column densities, which is inconsistent with previous claims
that the UV and X-ray absorption arises in the same material. Analysis of these
components supports a picture with a wide range of ionization parameters,
temperatures, and column densities in AGN outflows.


title: Evidence for Synchrotron Bubbles from GRS 1915+105

abstract:
  We present GMRT observations of the Galactic microquasar GRS 1915+105 at 1.28
GHz for 8 days from 2001 June 18 to July 1. We have seen several isolated radio
flares of varying magnitudes (20 - 50 mJy) and durations (6 - 35 min) and we
model them as due to adiabatically expanding synchrotron emitting clouds
(synchrotron bubbles) ejected from the accretion disk. By applying this model,
we provide a new method to estimate the electron power-law index p, hence the
spectral index, from single frequency radio observations. This method does not
require correction for the optical depth time delay effects which may be
important in the case of optically thick radio emission. Using our estimated
value of p and simultaneous multiwavelength data from literature, we have
calculated the time of ejection of the synchrotron plasma and the time delays
at different observed frequencies. Our estimates are in good agreement with the
observed time delays.


title:
XMM-Newton observation of the distant (z=0.6) galaxy cluster RX
  J1120.1+4318

abstract:
  We report on a 20 ksec XMM observation of the distant cluster RXJ1120.1+4318,
discovered at z=0.6 in the SHARC survey. The cluster has a regular spherical
morphology, suggesting it is in a relaxed state. The combined fit of the
EPIC/MOS&pn camera gives a cluster mean temperature of kT=5.3\pm0.5 keV with an
iron abundance of 0.47\pm0.19. The temperature profile, measured for the first
time at such a redshift, is consistent with an isothermal atmosphere up to half
the virial radius. The surface brightness profile, measured nearly up to the
virial radius, is well fitted by a beta-model, with beta =0.78[+0.06,-0.04] and
a core radius of thetac = 0.44[+0.06,-0.04] arcmin. We compared the properties
of RXJ1120.1+4318 with the properties of nearby clusters for two cosmological
models: an Einstein - de Sitter Universe and a flat low density Universe with
Omega0=0.3. For both models, the scaled emission measure profile beyond the
core, the gas mass fraction and luminosity are consistent with the expectations
of the self-similar model of cluster formation, although a slightly better
agreement is obtained for a low density Universe. There is no evidence of a
central cooling flow, in spite of the apparent relaxed state of the cluster.
This is consistent with its estimated cooling time, larger than the age of the
Universe at the cluster redshift. The entropy profile shows a flat core with a
central entropy of ~ 140 keV cm^2, remarkably similar to the entropy floor
observed in nearby clusters, and a rising profile beyond typically 0.1 virial
radius. Implications of our results, in terms of non-gravitational physics in
cluster formation, are discussed.


title: Scalar Field Dark Matter and Galaxy Formation

abstract:
  We present a general description of the scalar field dark matter (SFDM)
hypothesis in the cosmological context. The scenario of structure formation
under such a hypothesis is based on Jeans instabilities of fluctuations of the
scalar field. It is shown that it is possible to form stable long lived objects
consisting of a wide range of typical galactic masses around $10^{12}M_{\odot}$
once the parameters of the effective theory are fixed with the cosmological
constraints. The energy density at the origin of such an object is smooth as it
should.


title: Parity properties of an advection-dominated solar $\alpha^2\Om$-dynamo

abstract:
  We have developed a high-precision code which solves the kinematic dynamo
problem both for given rotation law and meridional flow in the case of a low
eddy diffusivity of the order of $10^{11}$ cm$^2$/s known from the sunspot
decay. All our models work with an \alf-effect which is positive (negative) in
the northern (southern) hemisphere. It is concentrated in radial layers located
either at the top or at the bottom of the convection zone. We have also
considered an \alf-effect uniformly distributed in all the convection zone. In
the present paper the main attention is focused on i) the parity of the
solution, ii) the form of the butterfly diagram and iii) the phase relation of
the resulting field components. If the helioseismologically derived internal
solar rotation law is considered, a model without meridional flow of high
magnetic Reynolds number (corresponding to low eddy diffusivity) fails in all
the three issues in comparison with the observations. However, a meridional
flow with equatorial drift at the bottom of the convection zone of few meters
by second can indeed enforce the equatorward migration of the toroidal magnetic
field belts similar to the observed butterfly diagram but, the solution has
only a dipolar parity if the (positive) \alf-effect is located at the base of
the convection zone rather than at the top. We can, therefore, confirm the main
results of a similar study by Dikpati & Gilman (2001).


title:
Interaction between Ionized and Molecular Gas in the Active Star-Forming
  Region W31

abstract:
  We have carried out 21 cm radio continuum, H76_\alpha radio recombination
line, and various (CO, ^13CO, CS, & C^34S) molecular line observations of the
W31 complex. Our radio continuum data show that W31 is composed of two extended
HII regions, G10.2-0.3 and G10.3-0.1, each of which comprises an ultracompact
HII region, two or more compact components, and diffuse envelope. The W31 cloud
appears as an incomplete shell on the whole and consists of southern spherical
and northern flat components, which are associated with G10.2-0.3 and
G10.3-0.1, respectively. We detect two large and massive CS-emitting regions in
the northern and southern cloud components. The large amount of dense gas may
suggest that the W31 cloud has ability to form rich stellar clusters and that
star formation has only recently begun. The extended envelopes of both
G10.2-0.3 and G10.3-0.1 are likely to be results of the champagne flows, based
on the distributions of ionized and molecular gas and the velocity gradient of
H76_\alpha line emission. We find strong evidence of bipolar molecular outflows
associated with the two ultracompact HII regions. In the vicinity of the
ultracompact and compact HII regions in G10.3-0.1, the CO J=2-1/J=1-0 intensity
ratio is high (1.4) and a small but prominent molecular gas hollow exists.
These observations strongly indicate that the HII regions and their ionizing
stars are interacting with the molecular cloud. Therefore, it is most likely
that recently formed massive stars are actively disrupting their parental
molecular cloud in the W31 complex.


title:
Hierarchical Structure of HII Regions - Ultracompact, Compact, and
  Extended Components

abstract:
  We have observed extended emission physically associated with 15 out of 16 UC
HII regions with large ratios of single-dish to VLA fluxes. We discuss their
implications for the age problem of UC HII regions and the evolution of HII
regions.


title:
Generation of Flows in the Solar Chromosphere Due to Magnetofluid
  Coupling

abstract:
  It is shown that a generalized magneto-Bernoulli mechanism can effectively
generate high velocity flows in the Solar chromosphere by transforming the
plasma pressure energy into kinetic energy. It is found that at reasonable
heights and for realistic plasma parameters, there is a precipitous pressure
fall accompanied by a sharp amplification of the flow speed.


title:
Experience of high resolution VLBI imaging using generalized maximum
  entropy method

abstract:
  The generalized maximum entropy method (GMEM) is a special modification of
the standard maximum entropy method (MEM) which seeks solutions in the space of
complex functions. In this work a reduced version of the GMEM intended for
reconstructing real images with positive and negative values is used. As
compared with the standard MEM, intended for the reconstruction of only
non-negative images, the GMEM allows us to obtain higher-quality images with a
much lower level of nonlinear distortions caused by errors in the data. Here,
we present the results of the GMEM imaging of 36 selected extragalactic radio
sources with a resolution of 0.3-0.5 mas on astrometric and geodetic VLBI
observations at 8.2 GHz, obtained with a global array in the period from
1994-1996. In VLBI mapping practice this is the first experience of imaging
with such a high resolution using maximum entropy technique. A differential
maximum entropy method intended for increasing the dynamic range of images is
demonstrated on the radio source 0059+581. In the case of unreliable `closure'
phases, completely `phaseless' methods of mapping are recommended. Maps of two
sources 0615+820 and 0642+214 are obtained using one such method.


title: The structure of molecular clumps around high-mass young stellar objects

abstract:
  We have used the IRAM 30-m and FCRAO 14-m telescopes to observe the molecular
clumps associated with 12 ultracompact (UC) HII regions in the J=6-5, 8-7 and
13-12 rotational transitions of methyl-acetylene (CH3C2H). Under the assumption
of LTE and optically thin emission, we have derived temperature estimates
ranging from 30 to 56 K. We estimate that the clumps have diameters of 0.2-1.6
pc, H_2 densities of 10^5-10^6 {cm^{-3}}, and masses of 10^2-2 10^4 M_\odot. We
compare these values with those obtained by other authors from different
molecular tracers and find that the H_2 density and the temperature inside the
clumps vary respectively like n_{H_2} ~ R^{-2.6} and T ~ R^{-0.5}, with R
distance from the centre. We also find that the virial masses of the clumps are
~3 times less than those derived from the CH3C2H column densities: we show that
a plausible explanation is that magnetic fields play an important role to
stabilise the clumps, which are on the verge of gravitational collapse.
Finally, we show that the CH3C2H line width increases for decreasing distance
from the clump centre: this effect is consistent with infall in the inner
regions of the clumps. We conclude that the clumps around UC HII regions are
likely to be transient (~10^(5) yr) entities, remnants of isothermal spheres
currently undergoing gravitational collapse: the high mass accretion rates
(~10^{-2} M_\odot yr^{-1}) lead to massive star formation at the centre of such
clumps.


title:
Stability of the lattice formed in first-order phase transitions to
  matter containing strangeness in protoneutron stars

abstract:
  Well into the deleptonization phase of a core collapse supernova, a
first-order phase transition to matter with macroscopic strangeness content is
assumed to occur and lead to a structured lattice defined by negatively charged
strange droplets. The lattice is shown to crystallize for expected droplet
charges and separations at temperatures typically obtained during the
protoneutronstar evolution. The melting curve of the lattice for small
spherical droplets is presented. The one-component plasma model proves to be an
adequate description for the lattice in its solid phase with deformation modes
freezing out around the melting temperature. The mechanical stability against
shear stresses is such that velocities predicted for convective phenomena and
differential rotation during the Kelvin-Helmholtz cooling phase might prevent
the crystallization of the phase transition lattice. A solid lattice might be
fractured by transient convection, which could result in anisotropic neutrino
transport. The melting curve of the lattice is relevant for the mechanical
evolution of the protoneutronstar and therefore should be included in future
hydrodynamics simulations.


title: Ten Billion Years of Galaxy Evolution

abstract:
  Observations in the Hubble Deep Fields have been used to study the evolution
of galaxy morphology over time. The majority of galaxies with z < 1 are seen to
be disk like, whereas most objects with z > 2 appear to be either chaotic or
centrally concentrated ``blobs''. Such blobs might be the ancestral objects of
ellipticals or of galaxy bulges. About 1/3 of objects with z > 2 appear to be
in the process of merging. The region with 1 < z < 2 marks an important
transition in the global history of star formation from a merger dominated
regime at z > 2, to one at z < 1 in which most star formation takes place in
galactic disks. It is speculated that the break in the Madau plot at z sim 1.5
might be related to the transition from merger-dominated star formation at z >
2 to disk-dominated star formation at at z < 1.


title:
Dust-to-gas ratio and star formation history of blue compact dwarf
  galaxies

abstract:
  This paper investigates the origin of the observed large variety in
dust-to-gas ratio among blue compact dwarf galaxies (BCDs). By applying our
chemical evolution model, we find that the dust destruction can largely
suppress the dust-to-gas ratio when the metallicity of a BCD reaches
$12+\log{\rm (O/H)}\sim 8$, i.e., a typical metallicity level of BCDs. We also
show that dust-to-gas ratio is largely varied owing to the change of dust
destruction efficiency that has two effects: (i) a significant contribution of
Type Ia supernovae to total supernova rate; (ii) variation of gas mass
contained in a star-forming region. While mass loss from BCDs was previously
thought to be the major cause for the variance of dust-to-gas ratio, we suggest
that the other two effects are also important. We finally discuss the
intermittent star formation history, which naturally explains the large
dispersion of dust-to-gas ratio among BCDs.


title: HST NICMOS Observations of the Polarization of NGC 1068

abstract:
  We have observed the polarized light at 2 micron in the center of NGC 1068
with HST NICMOS Camera 2. The nucleus is dominated by a bright, unresolved
source, polarized at a level of 6.0 pm 1.2% with a position angle of 122degr pm
1.5degr. There are two polarized lobes extending up to 8'' northeast and
southwest of the nucleus. The polarized flux in both lobes is quite clumpy,
with the maximum polarization occurring in the southwest lobe at a level of 17%
when smoothed to 0.23'' resolution. The perpendiculars to the polarization
vectors in these two lobes point back to the intense unresolved nuclear source
to within one 0.076'' Camera 2 pixel, thereby confirming that this is the
illuminating source of the scattered light and therefore the probable AGN
central engine. Whereas the polarization of the nucleus is probably caused by
dichroic absorption, the polarization in the lobes is almost certainly caused
by scattering, with very little contribution from dichroic absorption. Features
in the polarized lobes include a gap at a distance of about 1'' from the
nucleus toward the southwest lobe and a ``knot'' of emission about 5''
northeast of the nucleus. Both features had been discussed by ground-based
observers, but they are much better defined with the high spatial resolution of
NICMOS. The northeast knot may be the side of a molecular cloud that is facing
the nucleus, which cloud may be preventing the expansion of the northeast radio
lobe at the head of the radio synchrotron-radiation-emitting jet. We also
report the presence of two ghosts in the Camera 2 polarizers. These had not
been detected previously (Hines et al. 2000) because they are relatively faint
and require observations of a source with a large dynamic range.


title: Survey of the ISM in Early-Type Galaxies. IV. The Hot Dust Component

abstract:
  We present mid-IR photometric properties for a sample of 28 early-type
galaxies observed at 6.75, 9.63 and 15 um with the ISOCAM instrument on board
the ISO satellite. We find total mid-IR luminosities in the range 3-48x10^8
L_sun. The spectral energy distribution (SED) of the galaxies were derived
using the mid-IR data together with previously published UV, optical and
near-IR data. These SEDs clearly show a mid-IR emission coming from dust heated
at T ~ 260 K. Dust grains properties are inferred from the mid-IR colors. The
masses of the hot dust component are in the range 10-400 M_sun. The
relationship between the masses derived from mid-IR observations and those
derived from visual extinction are discussed. The possible common heating
source for the gas and dust is investigated through the correlations between Ha
and mid-IR luminosities.


title: Soft X-ray emission lines in the early afterglow of gamma-ray bursts

abstract:
  We compute the luminosity of K_alpha emission lines produced by
astrophysically abundant elements in the soft X-ray spectra of the early
afterglow of gamma-ray bursts. We find that the detection of these lines can be
a diagnostic for the geometrical set-up of the reprocessing material. In
particular we can distinguish between a ``geometry dominated'' model, in which
the line emission is coming from an extended region and its duration arises
from light-travel-time effects and an ``engine dominated'' model, where the
line emitting gas is in a smaller region, irradiated for a longer period. These
lines therefore offer clues to the dynamics and time-scale of the explosion
leading to a gamma-ray burst.


title:
The Frequency Stability of Millisecond Oscillations in Thermonuclear
  X-Ray Bursts

abstract:
  We analyze the frequency evolution of millisecond oscillations observed
during type I X-ray bursts with the Rossi X-ray Timing Explorer in order to
establish the stability of the mechanism underlying the oscillations. Our
sample contains 68 pulse trains detected in a search of 159 bursts from 8
accreting neutron stars. As a first step, we confirm that the oscillations
usually drift upward in frequency by about 1% toward an apparent saturation
frequency. Previously noted anomalies, such as drifts toward lower frequencies
as the oscillations disappear (``spin-down'' episodes) and instances of two
signals present simultaneously at frequencies separated by a few Hz, occur in
5% of oscillations. Having verified the generally accepted description of burst
oscillations, we proceed to study the coherence of the oscillations during
individual bursts, and the dispersion in the asymptotic frequencies in bursts
observed over five years. On short time scales, we find that 30% of the
oscillation trains do not appear to evolve smoothly in phase. This suggests
either that two signals are present simultaneously with a frequency difference
too small to resolve (< 1 Hz), that the frequency evolution is discontinuous,
or that discrete phase jumps occur. On time scales of years, the maximum
frequencies of the oscillations exhibit fractional dispersions of < 0.004. In
the case of 4U 1636-536, this dispersion is uncorrelated with the known orbital
phase, which indicates that a mechanism besides orbital Doppler shifts prevents
the oscillations from appearing perfectly stable. We interpret these results
under the assumption that the oscillations originate from anisotropies in the
emission from the surfaces of these rotating neutron stars. (Abridged)


title: Ultraluminous X-ray Sources in M51

abstract:
  We present the results of Chandra observations of off-nuclear X-ray sources
in the spiral galaxy M51 (NGC 5194). 113 X-ray sources have been detected in
the field of view and 84 among them project within the disk of NGC 5194. Six
and twenty eight sources have luminosities exceeding 1x10^39 ergs s^-1 and
1x10^38 ergs s^-1 in the 0.5-8 keV band, respectively. The number of luminous
sources is much higher than normal spiral and elliptical galaxies and similar
to galaxies experiencing starburst activity. X-ray spectra of most of the
detected sources are consistent with a power law with a photon index between 1
and 2, while one source has an extremely hard spectrum and two sources have
soft spectra. The spectra of three ultraluminous sources are consistent with
both a power law and a multicolor disk blackbody (MCD) model, while a power law
model is preferable to a MCD model in two objects. One luminous object which
shows a remarkable spectrum, including emission lines, is also found and
discussed.


title:
New Constraints on Galaxy Evolution from the Optical Monitor on
  XMM-Newton

abstract:
  We use galaxies detected in a deep ultraviolet XMM-Newton Optical Monitor
image and a model that predicts UV galaxy counts based on local counts and
evolution parameters to constrain galaxy evolution to Z=1.2. The 17' square
2000 angstrom (UVW2 filter) image was taken as part of the XMM-OM team's
guaranteed time program. We detect sources in this image to a flux limit of 2.7
X 10^{-17} ergs/cm^2/s/A, (AB magnitude = 22). Since some of the sources may be
stars, we perform a number of checks, including shape, color and implied
distance to remove stars from the detected counts. We find galaxy number counts
as a function of magnitude roughly in agreement with previous studies, but
again find these counts are in excess of evolution models. The excess counts at
faint magnitudes may provide evidence for either a new population of galaxies
emerging around Z=0.7 or more dramatic evolution than some earlier predictions.
The integrated light from the detected galaxies totals 32--36 ph/cm^2/s/A/sr,
placing a firm lower limit on the integrated UV light from galaxies.


title: HI Survey Science with the Canadian Large Adaptive Reflector

abstract:
  The Canadian Large Adaptive Reflector (CLAR) is a proposed prototype of a new
concept for large, filled-aperture radio telescopes. The prototype would have a
300-metre aperture, working up to frequencies of at least 1.4 GHz, and would be
equipped with a multi-beam phased array providing a field-of-view of 0.8deg at
that frequency. The largest fully-steerable radio telescope in the world, and
endowed with a large field-of-view, the CLAR will be uniquely suited for deep
spectral imaging over large areas of the sky. Conducted over a period of three
to four years, a CLAR Northern-Sky Survey would allow us to simultaneously:
survey at arcminute scales the distribution and kinematics of the faint HI in
the halo of the Milky Way and High Velocity Clouds; chart the large scale
distribution of galaxies in HI out to redshift close to 1; reveal the structure
and dynamics of the cosmic web responsible for wide-spread Lyman $\alpha$
absorption systems; image the signal of the reionization of the Universe over a
large area with resolution of 10's of arcminutes.


title: Recent Dynamical Evolution of Galaxy Clusters

abstract:
  Evidence is presented for a recent evolution of the relaxation processes in
clusters of galaxies, using large optical and X-ray cluster samples. The
criteria of the cluster relaxation used are the cluster ellipticity, the ICM
temperature and X-ray cluster luminosity. We find evidence of varying strength
and significance of all three indicators evolving with redshift for z <0.15.
This result supports the view that clusters have mostly stopped undergoing
mergers and accreting matter, as expected in a low-Omega_matter Universe, and
are now in the process of gravitational relaxation, which reduces their
flattening, their ICM temperature (shock heated during the merging phase), and
their X-ray luminosity. These results support similar recent claims of Melott,
Chambers and Miller (2001).


title:
Primordial nucleosynthesis with a varying fine structure constant: An
  improved estimate

abstract:
  We compute primordial light-element abundances for cases with fine structure
constant alpha different from the present value, including many sources of
alpha dependence neglected in previous calculations. Specifically, we consider
contributions arising from Coulomb barrier penetration, photon coupling to
nuclear currents, and the electromagnetic components of nuclear masses. We find
the primordial abundances to depend more weakly on alpha than previously
estimated, by up to a factor of 2 in the case of ^7Li. We discuss the
constraints on variations in alpha from the individual abundance measurements
and the uncertainties affecting these constraints. While the present best
measurements of primordial D/H, ^4He/H, and ^7Li/H may be reconciled pairwise
by adjusting alpha and the universal baryon density, no value of alpha allows
all three to be accommodated simultaneously without consideration of systematic
error. The combination of measured abundances with observations of acoustic
peaks in the cosmic microwave background favors no change in alpha within the
uncertainties.


title: Collisional Stellar Dynamics, Gas Dynamics and Special Purpose Computing

abstract:
  Challenging stellar dynamical problems, such as the study of gravothermal
oscillations in star clusters, have in the past initiated the very successful
building of GRAPE special purpose computers. It is discussed, that present day
tasks such as the formation and evolution of galactic nuclei with one or more
massive black holes and the coupled stellar and gas dynamical processes in the
formation of nuclei and star clusters, demand a new kind of hybrid
architecture, using both GRAPE and a reconfigurable logics board called RACE.
For such a system we have developed first implementations and floating point
performance studies in the case of the SPH algorithm (smoothed particle
hydrodynamics), which will be of great advantage for SPH modelling and also for
direct $N$-body simulations using the more efficient Ahmad-Cohen neighbour
schemes.


title: Chaotic reheating

abstract:
  We discuss the structure of parametric resonance which occurs in the process
of reheating after inflation with two interacting scalar fields. It is found
that, for the case of a not too large coupling constant, a quasi-homogeneous
part of the second, initially subdominant scalar field may not be neglected due
to its stochastic growth during inflation. This fact has strong consequences
for the reheating stage: dynamics of background fields becomes chaotic after
inflation -- it consists of subsequent chaotic and regular eras, and a
tachyonic instability for inhomogeneous perturbations arises in the quantum
reheating problem. This instability may pose a problem for the standard
reheating scenario. In order to avoid it, the coupling constant should be
either sufficiently small, or very large.


title:
Calibration of the distance scale from galactic Cepheids:II Use of the
  HIPPARCOS calibration

abstract:
  New estimate of the distances of 36 nearby galaxies is presented. It is based
on the calibration of the V- and I-band Period-Lumi- nosity relations for
galactic Cepheids measured by the HIPPARCOS mission. The distance moduli are
obtained in a classical way. The statistical bias due to the incompleteness of
the sample is corrected according to the precepts introduced by Teerikorpi
(1987).
  We adopt a constant slope (the one obtained with LMC Cepheids). The
correction for incompleteness bias introduce an uncertainty which depends on
each galaxy. On the mean, this uncertainty is small (0.04 mag) but it may reach
0.3 mag. We show that the un- certainty due to the correction of the extinction
is small (propably less than 0.05 mag.). The correlation between the
metallicity and the morphological type of the host galaxy sug- gests us to
reduce the application to spiral galaxies in order to bypass the problem of
metallicity. We suspect that the adopted PL slopes are not valid for all
morphological types of galaxies. This may induce a mean systematic shift of 0.1
mag on distance moduli.
  A comparison with the distance moduli recently published by Freedman et al.
(2001) shows there is a reasonably good agreement with our distance moduli.


title:
The Y-Band at 1.035 um: Photometric Calibration and the Dwarf
  Stellar/Sub-Stellar Color Sequence

abstract:
  We define and characterize a photometric bandpass (called "Y") that is
centered at 1.035 um, in between the traditionally classified ``optical'' and
``infrared'' spectral regimes. We present Y magnitudes and Y-H and Y-K colors
for a sample consisting mostly of photometric and spectral standards, spanning
the spectral type range sdO to T5V. Deep molecular absorption features in the
near-infrared spectra of extremely cool objects are such that the Y-H and Y-K
colors grow rapidly with advancing spectral type especially from late M through
mid L, substantially more rapidly than J-H or H-K which span a smaller total
dynamic range. Consistent with other near-infrared colors, however, Y-H and Y-K
colors turn blueward in the L6-L8 temperature range with later T-type objects
having colors similar to those of warmer M and L stars. Use of the Y-band
filter is nonetheless promising for easy identification of low-mass stars and
brown dwarfs, especially at young ages. The slope of the interstellar reddening
vector within this filter is A_Y = 0.38 x A_V. Reddening moves stars nearly
along the YHK dwarf color sequence making it more difficult to distinguish
unambiguously very low mass candidate brown dwarf objects from higher mass
stars seen, e.g. through the galactic plane or towards star-forming regions.
Other diagrams involving the Y-band may be somewhat more discriminating.


title:
The carrier of the "30" micron emission feature in evolved stars. A
  simple model using magnesium sulfide

abstract:
  We present 2-45 micron spectra of a large sample of carbon-rich evolved stars
in order to study the ``30'' micron feature. We find the ``30'' micron feature
in sources in a wide range of sources: low mass loss carbon stars, extreme
carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles
from the sources by using a simple systematic approach to model the continuum.
We find large variations in the wavelength and width of the extracted profiles
of the ``30'' micron feature. We modelled the whole range of profiles in a
simple way by using magnesium sulfide (MgS) dust grains with a MgS grain
temperature different from the continuum temperature. The systematic change in
peak positions can be explained by cooling of MgS grains as the star evolves
off the AGB. In several sources we find that a residual emission excess at ~26
micron can also be fitted using MgS grains but with a different grains shape
distribution. The profiles of the ``30'' micron feature in planetary nebulae
are narrower than our simple MgS model predicts. We discuss the possible
reasons for this difference. We find a sample of warm carbon-stars with very
cold MgS grains. We discuss possible causes for this phenomenon. We find no
evidence for rapid destruction of MgS during the planetary nebula phase and
conclude that the MgS may survive to be incorporated in the ISM.


title: The age of the Sun and the relativistic corrections in the EOS

abstract:
  We show that the inclusion of special relativistic corrections in the revised
OPAL and MHD equations of state has a significant impact on the helioseismic
determination of the solar age. Models with relativistic corrections included
lead to a reduction of about $0.05 - 0.08 \gi $ with respect to those obtained
with the old OPAL or MHD EOS. Our best-fit value is $t_\mathrm{seis} = (4.57
\pm 0.11) \gi $ which is in remarkably good agreement with the meteoritic value
for the solar age. We argue that the inclusion of relativistic corrections is
important for probing the evolutionary state of a star by means of the small
frequency separations $\delta\nu_{{\ell,n}}=\nu_{{\ell,n}}-\nu_{{\ell+2,n-1}}$,
for spherical harmonic degrees $\ell = 0,1$ and radial order $n \gg \ell$.


title: The lithium content of the globular cluster NGC 6397

abstract:
  We make use of high resolution, high signal-to-noise ratio spectra of 12
turn-off stars in the metal-poor globular cluster NGC 6397 to measure its
lithium content. We conclude that they all have the same lithium abundance
A(Li) = 2.34 with a standard deviation of 0.056 dex. We use this result,
together with Monte Carlo simulations, to estimate that the maximum allowed
intrinsic scatter is of the order of 0.035 dex. This is a new stringent
constraint to be fulfilled by stellar models which predict Li depletion. We
argue that although a mild depletion of 0.1 -- 0.2 dex, as predicted by recent
models, cannot be ruled out, there is no compelling reason for it. This fact,
together with the good agreement with the Li abundance observed in field stars,
supports the primordial origin of lithium in metal-poor stars. Taking the above
value as the primordial lithium abundance implies a cosmic baryonic density
which is either Omega_b h^2 = 0.016 +/- 0.004 or Omega_b h^2 = 0.005
^{+0.0026}_{-0.0006}, from the predictions of standard big bang
nucleosynthesis. The high baryonic density solution is in agreement with recent
results on the primordial abundance of deuterium and 3He and on the estimates
derived from the fluctuations of the cosmic microwave background.


title: Blazars, Gamma Ray Bursts and Galactic superluminal sources

abstract:
  BeppoSAX is best known for its role in the disclosure of the Gamma-Ray Burst
mystery, but it has also improved our understanding of jetted sources in
general, and blazars in particular. On the interpretational side, we are
curious to see if all sources with relativistic jets (or "flying pancakes", as
in GRBs) are controlled by the same basic physics, despite the very different
lifetimes and behavior. To this end we explore some general characteristics of
blazars, GRBs and superluminal galactic sources, such as their bulk Lorentz
factors, the power of their jets compared with what they can extract through
accretion, and the value of the magnetic field, close to the black hole, needed
to extract the spin energy of a rotating black hole. We find remarkable
similarities, namely that the outflowing mass rate is of the order of 1 per
cent of the accretion mass rate in all systems, and that the value of the
magnetic field required to efficiently extract the spin energy of the black
hole is of the order of the gravitational energy density of the matter close to
the gravitational radius. We then go on to discuss the way in which the energy
in bulk relativistic motion can be transformed into beamed radiation, and
consider the possibility that all three classes of sources could work in the
same way, namely by a intermittent release of relativistic plasma at the base
of the jet and thus with similar efficiency. Different patches of material,
with slightly different velocities, collide at some distance from the black
hole, producing the radiation we see.


title:
Neutrino Emission from Superfluid Neutron-Star Cores: Various Types of
  Neutron Pairing

abstract:
  We calculate and provide analytic fits of the factors which describe the
reduction of the neutrino emissivity of modified Urca and nucleon-nucleon
bremsstrahlung processes by superfluidity of neutrons and protons in
neutron-star cores. We consider $^1$S$_0$ pairing of protons and either
$^1$S$_0$ or $^3$P$_2$ pairing of neutrons. We analyze two types of $^3$P$_2$
pairing: the familiar pairing with zero projection of the total angular
momentum of neutron pairs onto quantization axis, $m_J=0$; and the pairing with
$|m_J|=2$ which leads to the gap with nodes at the neutron Fermi surface.
Combining the new data with those available in the literature we fully describe
neutrino emission by nucleons from neutron star cores to be used in simulations
of cooling of superfluid neutron stars.


title:
Dark and luminous matter in the NGC 3992 group of galaxies, I. The large
  barred spiral NGC 3992

abstract:
  Detailed neutral hydrogen observations have been obtained of the large barred
spiral galaxy NGC 3992 and its three small companion galaxies, UGC 6923, UGC
6940, and UGC 6969. For the main galaxy, the HI distribution is regular with a
low level radial extension outside the stellar disc. However, at exactly the
region of the bar, there is a pronounced central HI hole in the gas
distribution. Likely gas has been transported inwards by the bar and because of
the emptyness of the hole no large accretion events can have happened in recent
galactic times. The gas kinematics is very regular and it is demonstrated that
the influence of the bar potential on the velocity field is negligible. A
precise and extended rotation curve has been derived showing some distinct
features which can be explained by the non-exponential radial light
distribution of NGC 3992. The decomposition of the rotation curve gives a
slight preference for a sub maximal disc, though a range of disc contributions,
up to a maximum disc situation fits nearly equally well. For such a maximum
disc contribution, which might be expected in order to generate and maintain
the bar, the required mass-to-light ratio is large but not exceptional.


title: Near-infrared spectra of ISO selected Chamaeleon I young stellar objects

abstract:
  We present 0.95--2.5 micron moderate (R = 500) resolution spectra of 19
ISOCAM detected sources in the Chamaeleon I dark cloud. Thirteen of these stars
are candidate very low mass members of the cloud proposed by Persi et al. (2000
A&A 357:219) on basis of the mid-IR color excess. The sample also includes a
bona-fide young brown dwarf (Cha Halpha 1), a transition
--stellar/sub-stellar-- object (Cha Halpha 2), one previously known T Tauri
star (Sz 33) and three ISOCAM sources with no mid-IR excess. The spectra of the
mid-IR color excess sources are relatively flat and featureless in this
wavelength range. Both atomic and molecular lines (when in absorption) are
partially veiled suggesting the presence of continuum emission from
circumstellar dust. In addition some of the sources show Paschen and Brackett
lines in emission. We apply the 2 micron water vapor index defined by Wilking
et al. (1999 AJ 117:469) to estimate spectral types. These stars have spectral
types M0--8. We use Persi et al.'s stellar luminosity determinations, in
combination with D'Antona & Mazzitelli latest pre-main sequence evolutionary
tracks, to estimate masses and ages. The ISOCAM detected mid-IR excess sources
have sub-solar masses down to the H-burning limit and a median age of few x
10^6 yr, in good agreement with the higher mass members of this cloud.


title: The X-ray transient XTE J1859+226 in Outburst & Quiescence

abstract:
  We present optical photometry and spectroscopy of the X-ray transient XTE
J1859+226, obtained during outburst and its subsequent decay to quiescence.
Both the X-ray and optical properties are very similar to those of well-studied
black hole soft X-ray transients. We have detected 3 minioutbursts, when XTE
J1859+226 was approaching quiescence, as has been previously detected in the
Soft X-Ray Transients GRO J0422+32 and GRS 1009-45. By 24 Aug 2000 the system
had reached quiescence with R=22.48+/-0.07. The estimated distance to the
source is ~11 kpc. Photometry taken during quiescence shows a sinusoidal
modulation with a peak to peak amplitude of about 0.4 mag. A period analysis
suggests that periods from 0.28 to 0.47 days are equally possible at the 68%
confidence level. The amplitude of the quiescent light curve and the relatively
low ratio of X-ray to optical flux, indicates that the binary inclination
should be high. The measured colours during the outburst allows us to obtain
the basic properties of the disc, which agrees well with irradiated disc model
predictions.


title:
Scaling in the space climatology of the auroral indices: Is SOC the only
  possible explanation ?

abstract:
  The study of the robust features of the magnetosphere is motivated both by
new "whole system" approaches, and by the idea of "space climate" as opposed to
"space weather". We enumerate these features for the AE index, and discuss
whether self-organised criticality (SOC) is the most natural explanation of the
"stylised facts" so far known for AE. We identify and discuss some open
questions, answers to which will clarify the extent to which AE's properties
provide evidence for SOC. We then suggest an SOC-like reconnection-based
scenario drawing on the result of Craig(2001) as an explanation of the very
recent demonstration by Uritsky et al(2001b) of power laws in several
properties of spatiotemporal features seen in auroral images.


title:
Metal Abundances and Kinematics of Bright Metal-Poor Giants Selected
  from the LSE Survey: Implications for the Metal-Weak Thick Disk

abstract:
  We report medium-resolution (1-2 A) spectroscopy and broadband (UBV)
photometry for a sample of 39 bright stars (the majority of which are likely to
be giants) selected as metal-deficient candidates from an objective-prism
survey concentrating on Galactic latitudes below |b| = 30 deg, the LSE survey
of Drilling & Bergeron. Although the primary purpose of the LSE survey was to
select OB stars (hence the concentration on low latitudes), the small number of
bright metal-deficient giant candidates noted during this survey provide
interesting information on the metal-weak thick disk (MWTD) population.
  The kinematics of the LSE giants indicate the presence of a rapidly rotating
population, even at quite low metallicity. We consider the distribution of
orbital eccentricity of the LSE giants as a function of [Fe/H], and conclude
that the local fraction (i.e., within 1 kpc from the Sun) of metal-poor stars
that might be associated with the MWTD is on the order of 30%-40% at abundances
below [Fe/H] = -1.0. Contrary to recent analyses of previous (much larger)
samples of non-kinematically selected metal-poor stars, we find that this
relatively high fraction of local metal-poor stars associated with the MWTD may
extend to metallicities below [Fe/H] = -1.6, much lower than had been
considered before. We identify a subsample of 11 LSE stars that are very likely
to be members of the MWTD, based on their derived kinematics; the lowest
metallicity among these stars is [Fe/H] = -2.35. Implications of these results
for the origin of the MWTD and for the formation of the Galaxy are considered.
(abridged)


title: A differential method of maximum entropy

abstract:
  We consider a differential method of maximum entropy that is based on the
linearity of Fourier transform and involves reconstruction of images from the
differences of the visibility function. The efficiency of the method is
demonstrated with respect to the recovery of source images with bright
components against the background of a sufficiently weak extended base. The
simulation results are given along with the maps of an extragalactic radio
source 0059+581, which were obtained using the standard and differential
methods of maximum entropy for three observation dates and show that the
principle of differential mapping allows us to increase considerably the
dynamic interval of images.


title: On the Atomic Polarization of the Ground Level of Na I

abstract:
  In a recent letter (Trujillo Bueno et al. 2002), we showed the remarkable
result that the atomic alignment of the levels P$_{1/2}$ and S$_{1/2}$ of the
D$_1$ line of Na I is practically destroyed in the presence of magnetic fields
sensibly larger than 10 G, irrespectively of the field direction. In this
paper, we demonstrate analytically that this property is a consequence of the
decoupling of the electronic and nuclear angular momenta, J and I, in the
excited state P$_{3/2}$, which is achieved when the Zeeman splitting from the
local magnetic field becomes much larger than the typical hyperfine separation
for that level.