title:
EUV/X-ray Emission and the Thermal and Ionization Structure of B Star
  Winds

abstract:
  We discuss the EUV and X-ray properties of B stars, focusing on $\epsilon$
CMa (B2 II) which is the only star with both emission lines and a photospheric
continuum detected with EUVE. We explore the modest effects of the photospheric
EUV continua on the wind, as well as the much stronger effects of the
short-wavelength EUV and soft X-ray emission lines. Attenuation of the EUV and
soft X-ray emission by the wind plays an important role, and leads to the
reprocessing of X-rays via He$^+$ ionization and the Bowen mechanism in the
wind. Finally, we explore some of the new diagnostics that will shortly become
available with the next generation of high spectral resolution X-ray
telescopes. All of this analysis is presented in the context of a two component
stellar wind--a dense component (clumps) that contains most of the mass but
fills a negligible fraction of the volume, and a rarefied component that fills
most of the volume but accounts for only a small fraction of the mass.


title: Cosmological Relativity: A New Theory of Cosmology

abstract:
  A general-relativistic theory of cosmology, the dynamical variables of which
are those of Hubble's, namely distances and redshifts, is presented. The theory
describes the universe as having a three-phase evolution with a decelerating
expansion followed by a constant and an accelerating expansion, and it predicts
that the universe is now in the latter phase. The theory is actually a
generalization of Hubble's law taking gravity into account by means of
Einstein's theory of general relativity. The equations obtained for the
universe expansion are elegant and very simple. It is shown, assuming
Omega_0=0.24, that the time at which the universe goes over from a decelerating
to an accelerating expansion, i.e. the constant expansion phase, occurs at
0.03tau from the big bang, where tau is the Hubble time in vacuum. Also, at
that time the cosmic radiation temperature was 11K. Recent observations of
distant supernovae imply, in defiance of expectations, that the universe growth
is accelerating, contrary to what has always been assumed that the expansion is
slowing down due to gravity. Our theory confirms these recent experimental
results by showing that the universe now is definitely in a stage of
accelerating expansion.


title: Topology of the Galaxy Distribution in the Hubble Deep Fields

abstract:
  We have studied topology of the distribution of the high redshift galaxies
identified in the Hubble Deep Field (HDF) North and South. The two-dimensional
genus is measured from the projected distributions of the HDF galaxies at
angular scales from $3.8''$ to $ 6.1''$. We have also divided the samples into
three redshift slices with roughly equal number of galaxies using photometric
redshifts to see possible evolutionary effects on the topology.
  The genus curve of the HDF North clearly indicates clustering of galaxies
over the Poisson distribution while the clustering is somewhat weaker in the
HDF South. This clustering is mainly due to the nearer galaxies in the samples.
We have also found that the genus curve of galaxies in the HDF is consistent
with the Gaussian random phase distribution with no significant redshift
dependence.


title:
Radiation pressure instability as a variability mechanism in the
  microquasar GRS 1915+105

abstract:
  Physical mechanism responsible for high viscosity in accretion disks is still
under debate. Parameterization of the viscous stress as $\alpha P$ proved to be
a successful representation of this mechanism in the outer parts of the disk,
explaining the dwarf novae and X-ray novae outbursts as due to ionization
instability. We show that this parameterization can be also adopted in the
innermost part of the disk where the adoption of the $\alpha$-viscosity law
implies the presence of the instability in the radiation pressure dominated
region. We study the time evolution of such disks. We show that the
time-dependent behavior of GRS 1915+105 can be well reproduced if
$\alpha$-viscosity disk model is calculated accurately (with proper numerical
coefficients in vertically averaged equations and with advection included), and
if the model is supplemented with (i) moderate corona dissipating 50% of energy
(ii) jet carrying luminosity-dependent fraction of energy. These necessary
modifications in the form of the presence of a corona and a jet are well
justified observationally. The model predicts outbursts at luminosity larger
than 0.16$\dot M_{Edd}$, as required, correct outburst timescales and
amplitudes, including the effect of increasing outburst timescale with mean
luminosity. This result strongly suggests that the $\alpha$-viscosity law is a
good description of the actual mechanism responsible for angular momentum
transfer also in the innermost, radiation pressure dominated part of the disk
around a black hole.


title:
R-mode oscillations of rapidly rotating Newtonian stars - A new
  numerical scheme and its application to the spin evolution of neutron stars

abstract:
  We have developed a new numerical scheme to solve r-mode oscillations of {\it
rapidly rotating polytropic stars} in Newtonian gravity. In this scheme, Euler
perturbations of the density, three components of the velocity are treated as
four unknown quantities together with the oscillation frequency. For the basic
equations of oscillations, the compatibility equations are used instead of the
linearized equations of motion.
  By using this scheme, we have solved the classical r-mode oscillations of
rotational equilibrium sequences of polytropes with the polytropic indices $N =
0.5, 1.0$ and 1.5 for $m = 2, 3$ and 4 modes. Here $m$ is the rank of the
spherical harmonics $Y_l^m$. These results have been applied to investigate
evolution of uniformly rotating hot young neutron stars by considering the
effect of gravitational radiation and viscosity. We have found that the maximum
angular velocities of neutron stars are around 10-20% of the Keplerian angular
velocity irrespective of the softness of matter. This confirms the results
obtained from the analysis of r-modes with the slow rotation approximation
employed by many authors.


title: Thermal and Viscous Instability of Accretion Disc in AGN

abstract:
  The standard accretion discs are known to be thermally and viscously unstable
over a certain range of temperatures. In the inner disc regions there may
develop radiation pressure driven instability, which is possibly related to the
rapid variability detected in AGNs in the UV range. In the outer disc develops
the ionization instability, similar to that in the cataclysmic variables, but
operating on much longer timescales. Due to this process the spectrum of the
accretion disc differs from that of a stationary one.


title: HI Recycling: Formation of Tidal Dwarf Galaxies

abstract:
  Galactic collisions trigger a number of phenomena, such as transportation
inward of gas from distances of up to kiloparsecs from the center of a galaxy
to the nuclear region, fuelling a central starburst or nuclear activity. The
inverse process, the ejection of material into the intergalactic medium by
tidal forces, is another important aspect and can be studied especially well
through detailed HI observations of interacting systems which have shown that a
large fraction of the gaseous component of colliding galaxies can be expelled.
Part of this tidal debris might fall back, be dispersed throughout the
intergalactic medium or recondense to form a new generation of galaxies: the
so-called tidal dwarf galaxies. The latter are nearby examples of galaxies in
formation. The properties of these recycled objects are reviewed here and
different ways to identify them are reviewed.


title:
Discovery of a new, third kHz QPO in 4U 1608-52, 4U 1728-34, and 4U
  1636-53. Sidebands to the lower kHz QPO?

abstract:
  We report the discovery of a third kilohertz quasi-periodic oscillation (kHz
QPO) in the power spectra of the low-mass X-ray binaries 4U 1608-52 (6.3
sigma), 4U 1728-34 (6.0 sigma), and 4U 1636-53 (3.7 sigma) which is present
simultaneously with the previously-known kHz QPO pair. The new kHz QPO is found
at a frequency that is 52.8+-0.9 Hz, 64+-2 Hz, 58.4+-1.9 Hz higher than the
frequency of the lower kHz QPO in 4U 1608-52, 4U 1728-34, and 4U 1636-53,
respectively. The difference between the frequency of the new kHz QPO and the
lower kHz QPO increased in 4U 1608-52 from 49.6+-1.4 Hz to 53.9+-0.5 Hz when
the frequency of the lower kHz QPO increased from 672 Hz to 806 Hz.
Simultaneously the difference between the frequency of the new kHz QPO and the
upper kHz QPO increased by ~60 Hz, suggesting that the new kHz QPO is unrelated
to the upper kHz QPO. In 4U 1636-53 a fourth, weaker, kHz QPO is simultaneously
detected (3 sigma) at the same frequency separation below the lower kHz QPO,
suggesting the new kHz QPOs are sidebands to the lower kHz QPO. We discuss the
nature of this new kHz QPO and its implications on the models for the kHz QPOs.


title: Gas Flow and Star Formation in the `Antennae' Galaxies NGC 4038/9

abstract:
  The prominent interacting galaxy pair NGC 4038/9 contains many active
star-forming regions and is continuously forming new star clusters. We present
a self-consistent n-body model for this system which includes an SPH gas
component. The model qualitatively explains the apparent concentration of gas
in the so-called overlap region between the two nuclei as a bridge of gas
connecting the two galaxies. Projected on the sky, the bridge appears as a
dense spot of gas. We discuss some implications for the evolution of
Ultra-luminous infrared galaxies.


title: Evolution of a Rotating Black Hole with a Magnetized Accretion Disk

abstract:
  The effect of an accretion disk on the Blandford-Znajek process and the
evolution of a black hole are discussed using a simplified system for the black
hole - accretion disk in which the accretion rate is supposed to be dominated
by the strong magnetic field on the disk. The evolutions of the mass and the
angular momentum of the black hole are formulated and discussed with numerical
calculations.


title:
Study of the Temporal Behavior of 4U 1728-34 as a Function of its
  Position in the Color-Color Diagram

abstract:
  We study the timing properties of the bursting atoll source 4U 1728-34 as a
function of its position in the X-ray color-color diagram. In the island part
of the color-color diagram (corresponding to the hardest energy spectra) the
power spectrum of 4U 1728-34 shows several features such as a band-limited
noise component present up to a few tens of Hz, a low frequency quasi-periodic
oscillation (LFQPO) at frequencies between 20 and 40 Hz, a peaked noise
component around 100 Hz, and one or two QPOs at kHz frequencies. In addition to
these, in the lower banana (corresponding to softer energy spectra) we also
find a very low frequency noise (VLFN) component below ~1 Hz. In the upper
banana (corresponding to the softest energy spectra) the power spectra are
dominated by the VLFN, with a peaked noise component around 20 Hz. We find that
the frequencies of the kHz QPOs are well correlated with the position in the
X-ray color-color diagram. For the frequency of the LFQPO and the break
frequency of the broad-band noise component the relation appears more complex.
These frequencies both increase when the frequency of the upper kHz QPO
increases from 400 to 900 Hz, but at this frequency a jump in the values of the
parameters occurs. We interpret this jump in terms of the gradual appearance of
a QPO at the position of the break at high inferred mass accretion rate, while
the previous LFQPO disappears. Simultaneously, another kind of noise appears
with a break frequency of ~7 Hz, similar to the NBO of Z sources. The 100 Hz
peaked noise does not seem to correlate with the position of the source in the
color-color diagram, but remains relatively constant in frequency. This
component may be similar to several 100 Hz QPOs observed in black hole
binaries.


title: ISO impact on stellar models and vice versa

abstract:
  We present a detailed spectroscopic study of a sample of bright, mostly cool,
stars observed with the Short-Wavelength Spectrometer (SWS) on board the
Infrared Space Observatory (ISO), which enables the accurate determination of
the stellar parameters of the cool giants, but also serves as a critical review
of the ISO-SWS calibration.


title:
Testing the Correlation of Ultra-High Energy Cosmic Rays with High
  Redshift Sources

abstract:
  We study the correlation between compact radio quasars or 3EG gamma-ray
blazars and the arrival directions of cosmic rays above 10^19 eV using an
updated list of air shower detections. Our Monte Carlo simulations reveal no
significant correlations above random and some previous positive results appear
to be an effect of the small sample size. Consequently, unless somehow severely
deflected, there is no evidence for ultra-high energy cosmic ray primaries
being new particles or particles with new interactions beyond the electroweak
scale, produced in high-redshift active galactic nuclei.


title: Particle and Astrophysics Aspects of Ultrahigh Energy Cosmic Rays

abstract:
  The origin of cosmic rays is one of the major unresolved astrophysical
questions. In particular, the highest energy cosmic rays observed possess
macroscopic energies and their origin is likely to be associated with the most
energetic processes in the Universe. Their existence triggered a flurry of
theoretical explanations ranging from conventional shock acceleration to
particle physics beyond the Standard Model and processes taking place at the
earliest moments of our Universe. Furthermore, many new experimental activities
promise a strong increase of statistics at the highest energies and a
combination with $\gamma-$ray and neutrino astrophysics will put strong
constraints on these theoretical models. Detailed Monte Carlo simulations
indicate that charged ultra-high energy cosmic rays can also be used as probes
of large scale magnetic fields whose origin may open another window into the
very early Universe. We give an overview over this quickly evolving research
field.


title: Supernovae and the IGM

abstract:
  An energetic argument implies that a galaxy like the Milky Way is blowing a
powerful wind that carries away most of the heavy elements currently
synthesized and has impacted the IGM out to at least 180 kpc. Rich clusters of
galaxies appear to be closed systems in which most heavy elements are ejected
from galaxies. More supernovae are required than the yield of core-collapse SNe
from a Salpeter IMF. X-ray observations imply that the IGM in groups and
clusters as been strongly preheated. SNe probably cannot supply the required
energy, which must come from AGN.


title:
Damped Lyman alpha systems at z=0.68 and z=1.15 towards HE 1122-1649 and
  HE 0515-4414

abstract:
  Detailed analysis of the spectral lines from two low redshift damped Lyman
alpha absorbers (DLA) confirms that they are a heterogeneous population. Both
systems have low metal abundances of approximately 0.05 to 0.1 solar. The
abundance pattern of the DLA at z=1.15 towards HE 0515-4414 shows dust
depletion comparable to that found in our Galaxy, while the system at z=0.68
towards HE 1122-1649 shows abundance ratios resembling metal-poor halo stars
with no dust depletion, for a comparable HI column. Constraints for N/Fe and
N/Si also hint at z=0.68 DLA as a galaxy with recent star formation. The trend
of increasing CI/HI with decreasing z is discussed. Only weak absorption from
highly-ionized species associated with the DLA at moderate z have been detected
and it probably originates in regions distinct from the low ionization gas. The
low-ion profiles show very complex structures and are too large to be explained
by the rotation of a disk: the system at z=0.68 spans over approximately 300
km/s and the z=1.15 DLA presents substructure over more than 700 km/s, the
largest velocity extent found up to date for a DLA.


title: Superhumps in Low-Mass X-Ray Binaries

abstract:
  We propose a mechanism for the superhump modulations observed in optical
photometry of at least two black hole X-ray transients (SXTs). As in extreme
mass-ratio cataclysmic variables (CVs), superhumps are assumed to result from
the presence of the 3:1 orbital resonance in the accretion disc. This causes
the disc to become non-axisymmetric and precess. However the mechanism for
superhump luminosity variations in low mass X-ray binaries (LMXBs) must differ
from that in CVs, where it is attributed to a tidally-driven modulation of the
disc's viscous dissipation, varying on the beat between the orbital and disc
precession period. By contrast in LMXBs, tidal dissipation in the outer
accretion disc is negligible: the optical emission is overwhelming dominated by
reprocessing of intercepted central X-rays. Thus a different origin for the
superhump modulation is required. Recent observations and numerical simulations
indicate that in an extreme mass-ratio system the disc area changes on the
superhump period. We deduce that the superhumps observed in SXTs arise from a
modulation of the reprocessed flux by the changing area. Therefore, unlike the
situation in CVs, where the superhump amplitude is inclination-independent,
superhumps should be best seen in low-inclination LMXBs, whereas an orbital
modulation from the heated face of the secondary star should be more prominent
at high inclinations. Modulation at the disc precession period (10s of days)
may indicate disc asymmetries such as warping. We comment on the orbital period
determinations of LMXBs, and the possibility and significance of possible
permanent superhump LMXBs.


title:
Ionization, Magneto-rotational, and Gravitational Instabilities in Thin
  Accretion Disks Around Supermassive Black Holes

abstract:
  We consider the combined role of the thermal ionization, magneto-rotational
and gravitational instabilities in thin accretion disks around supermassive
black holes. We find that in the portions of the disk unstable to the
ionization instability, the gas remains well coupled to the magnetic field even
on the cold, neutral branch of the thermal limit cycle. This suggests that the
ionization instability is not a significant source of large amplitude
time-dependent accretion in AGN. We also argue that, for accretion rates
greater than 10^{-2} solar masses per year, the gravitationally unstable and
magneto-rotationally unstable regions of the accretion disk overlap; for lower
accretion rates they may not. Some low-luminosity AGN, e.g. NGC 4258, may thus
be in a transient phase in which mass is building up in a non-accreting
gravitationally and magneto-rotationally stable ``dead zone.'' We comment on
possible implications of these findings.


title: Signature neutrinos from ultrahigh-energy photons

abstract:
  At high red shift, the temperature of cosmic microwave background is
sufficiently high for the ultrahigh-energy photons to pair-produce muons and
pions through interactions with the background photons. At the same time, the
radio background and magnetic fields are too weak to drain energy out of the
electromagnetic cascade before the muons and pions are produced. Decays of the
energetic muons and pions yield neutrinos with some distinctive spectral
properties that can be detected and can indicate the presence of
ultrahigh-energy photons at high red shift. The neutrino signature can help
identify the origin of cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff.


title: Dynamical Masses of T Tauri Stars and Calibration of PMS Evolution

abstract:
  We have used the high sensitivity and resolution of the IRAM interferometer
to produce sub-arcsecond 12CO 2-1 images of 9 protoplanetary disks surrounding
T Tauri stars in the Taurus-Auriga cloud (7 singles and 2 binaries). The images
demonstrate the disks are in Keplerian rotation around their central stars.
Using the least square fit method described in Guilloteau and Dutrey (1998), we
derive the disk properties, in particular its inclination angle and rotation
velocity, hence the dynamical mass. Since the disk mass is usually small, this
is a direct measurement of the stellar mass. Typically, we reach an internal
precision of 10% in the determinations of stellar mass. The over-all accuracy
is limited by the uncertainty in the distance to a specific star. In a distance
independent way, we compare the derived masses with theoretical tracks of
pre-main-sequence evolution. Combined with the mean distance to the Taurus
region (140 pc), for stars with mass close to 1 Msun, our results tend to favor
the tracks with cooler photospheres (higher masses for a given spectral type).
We find that in UZ Tau E the disk and the spectroscopic binary orbit appear to
have different inclinations.


title: Fragmentation of a Protostellar Core: The Case of CB230

abstract:
  The Bok globule CB230 (L1177) contains an active, low-mass star-forming core
which is associated with a double NIR reflection nebula, a collimated bipolar
molecular outflow, and strong mm continuum emission. The morphology of the NIR
nebula suggests the presence of a deeply embedded, wide binary protostellar
system. High-angular resolution observations now reveal the presence of two
sub-cores, two distinct outflow centers, and an embedded accretion disk
associated with the western bipolar NIR nebula. In terms of separation and
specific angular momentum, the CB230 double protostar system probably results
from core fragmentation and can be placed at the upper end of the pre-main
sequence binary distribution.


title: Magnetic Extraction of Spin Energy from a Black Hole

abstract:
  Numerous variations have been proposed on the original suggestion by
Blandford and Znajek that magnetic fields could be used to extract rotational
energy from black holes. A new categorization of these variations is proposed
so that they may be considered in a systematic way. "Black hole spindown" is
defined more precisely, distinguishing decrease in the spin parameter a/M from
decreases in angular momentum a and rotational kinetic energy, M - M_i. Several
key physical questions are raised: Can the "stretched horizon" of a black hole
communicate with the outside world? Do accretion disks bring any net magnetic
flux to the black holes at their centers? Is the magnetic field adjacent to a
black hole force-free everywhere?


title: The mass function of NGC288

abstract:
  We present NICMOS NIC3 observations of the Galactic globular cluster NGC 288,
taken South - East at 2.4 times the cluster's half-light radius in the J and H
bands. We have detected the cluster main sequence down to J~25 and H~24. The
corresponding luminosity function covers the range 3<M_H<9 and peaks at
M_H~6.8. The theoretical tracks of Baraffe et al. (1997) at [Fe/H]=-1.3 give a
mass function which is best fitted by a log-normal distribution with
characteristic mass m_c=0.42 Msolar and a standard deviation sigma=0.35. This
result is fully consistent with the global mass function derived by Paresce &
De Marchi (2000) for a sample of 12 globular clusters with very different
dynamical histories, thus confirming that near the cluster's half-light radius
the mass function appears ``undistorted'' by evaporation or tidal interactions
with the Galaxy and should then reflect the initial mass function.


title: SCUBA observations of Hawaii 167

abstract:
  We present the first submillimetre observations of the z=2.36 broad
absorption line system Hawaii 167. Our observations confirm the hypothesis that
Hawaii 167 contains a massive quantity of dust, the optical depth of which is
sufficient to completely extinguish our ultraviolet view of a central, buried
quasar. Hawaii~167's submillimetre luminosity and associated dust mass are
similar to the ultraluminous class of infrared galaxies, supporting the
existence of an evolutionary link between these and the active galaxy
population. Hawaii 167 appears to be a young quasar which is emerging from its
dusty cocoon.


title: Sensitivity of the Radial Velocity Technique in Detecting Outer Planets

abstract:
  The technique of radial velocity (RV) has produced spectacular discoveries of
short-period Jovian mass objects around a fraction (5 to 10%) of nearby G
stars. Although we expect Jovian planets to be located in long-period orbits of
decades or longer (if our solar system is any guide), detecting such planets
with RV technique is difficult due to smaller velocity amplitudes and the
limited temporal baseline (5-10 yr) of current searches relative to the
expected orbital periods. In this paper, we develop an analytical understanding
of the sensitivity of RV technique in the regime where the the orbital period
is larger than the total baseline of the survey. Moreover, we focus on the
importance of the orbital phase in this ``long-period'' regime, and develop a
Least Squares detection technique based on the amplitude and phase of the
fitted signal.
  To illustrate the benefits of this amplitude-phase analysis, we compare it to
existing techniques. Previous authors (e.g. Nelson & Angel 1998) have explored
the sensitivity of an amplitude-only analysis using Monte Carlo simulations.
Others have supplemented this by using the slope of the linear component of the
fitted sinusoid in addition (e.g. Walker et al. 1995; Cumming et al. 1999). In
this paper, we illustrate the benefits of Least Squares over periodogram
analysis, and demonstrate the superiority of an amplitude-phase technique over
previous analyses.


title: Strangeness in Neutron Stars

abstract:
  It is generally agreed on that the tremendous densities reached in the
centers of neutron stars provide a high-pressure environment in which numerous
novel particles processes are likely to compete with each other. These
processes range from the generation of hyperons to quark deconfinement to the
formation of kaon condensates and H-matter. There are theoretical suggestions
of even more exotic processes inside neutron stars, such as the formation of
absolutely stable strange quark matter, a configuration of matter even more
stable than the most stable atomic nucleus, iron. In the latter event, neutron
stars would be largely composed of pure quark matter, eventually enveloped in a
thin nuclear crust. No matter which physical processes are actually realized
inside neutron stars, each one leads to fingerprints, some more pronounced than
others though, in the observable stellar quantities. This feature combined with
the unprecedented progress in observational astronomy, which allows us to see
vistas with remarkable clarity that previously were only imagined, renders
neutron stars to nearly ideal probes for a wide range of physical studies,
including the role of strangeness in dense matter.


title:
Detectability of Gravitational Lensing Effect on the Two-point
  Correlation Function of Hotspots in the CMB maps

abstract:
  We present quantitative investigations of the weak lensing effect on the
two-point correlation functions of local maxima (hotspots),
  $\xipk(\theta)$, in the cosmic microwave background (CMB) maps. The lensing
effect depends on the projected mass fluctuations between today and the
redshift $z_{\rm rec}\approx1100$. If adopting the Gaussian assumption for the
primordial temperature fluctuations field, the peak statistics can provide an
additional information about the intrinsic distribution of hotspots that those
pairs have some characteristic separation angles. The weak lensing then
redistributes hotspots in the observed CMB maps from the intrinsic distribution
and consequently imprints non-Gaussian signatures onto $\xipk(\theta)$.
Especially, since the intrinsic $\xipk(\theta)$ has a pronounced depression
feature around the angular scale of $\theta\approx 70'$ for a flat universe,
the weak lensing induces a large smoothing at the scale. We show that the
lensing signature therefore has an advantage to effectively probe mass
fluctuations with large wavelength modes around $\lambda\approx 50 h^{-1}{\rm
Mpc}$. To reveal the detectability, we performed numerical experiments with
specifications of {\em MAP} and {\em Planck Surveyor} including the
instrumental effects of beam smoothing and detector noise. It is then found
that our method can successfully provide constraints on amplitude of the mass
fluctuations and cosmological parameters in a flat universe with and without
cosmological constant, provided that we use maps with 65% sky coverage expected
from Planck.


title: The warm circumstellar envelope and wind of the G9 IIb star HR 6902

abstract:
  IUE observations of the eclipsing binary system HR 6902 obtained at various
epochs spread over four years indicate the presence of warm circumstellar
material enveloping the G9 IIb primary. The spectra show Si IV and C IV
absorption up to a distance of 3.3 giant radii (R_g}. Line ratio diagnostics
yields an electron temperature of ~ 78000 K which appears to be constant over
the observed height range.
  Applying a least square fit absorption line analysis we derive column
densities as a function of height. We find that the inner envelope (< 3 R_g) of
the bright giant is consistent with a hydrostatic density distribution. The
derived line broadening velocity of ~ 70 kms^{-1} is sufficient to provide
turbulent pressure support for the required scale height. However, an improved
agreement with observations over the whole height regime including the emission
line region is obtained with an outflow model. We demonstrate that the common
beta power-law as well as a P \propto rho wind yield appropriate fit models.
Adopting a continuous mass outflow we obtain a mass-loss rate of M_loss= (0.8 -
3.4)*10^{-11} M_{sun}yr^{-1} depending on the particular wind model.


title: A New interpretation of chain galaxies at high redshift

abstract:
  We propose a possible new model for the formation of chain galaxies at high
redshift. Our model is summarized as follows. Step I: Successive merging of
subgalactic gas clumps results in the formation of a galaxy with a mass of
$10^{11-12} M_\odot$ at redshift $z \sim 5$. Step II: Subsequently, supernova
explosions occur inside the galaxy and then blow out as a galactic wind (or a
superwind). This wind expands into the intergalactic space and then causes a
large-scale shell with a radius of several hundreds of kpc. Since this radius
may be smaller than the typical separation between galaxies, interactions of
shells may also occur, resulting in the formation of a large-scale gaseous
slab. Step III: Since the shell or the slab can be regarded as a gaseous sheet,
filament-like gravitational instability is expected to occur. Step IV: Further
gravitational instability occurs in each filament, leading to intense star
formation along the filament. This is the chain galaxy phase. Step V: The
filament collapses gravitationally into one spheroidal system like an
elliptical galaxy within one dynamical timescale of the filament ($\sim 10^8$
yr). Therefore, it seems quite difficult to find remnants of chain galaxies. We
also discuss that shocked shells driven by superwinds may be responsible for
some Lyman limit systems and damped Ly$\alpha$ systems because their H {\sc i}
column densities are expected to be $N_{\rm HI} \gtrsim 10^{19}$ cm$^{-2}$.


title:
High redshift radio galaxies: Beacons to biased hierarchical galaxy
  formation within large scale structure

abstract:
  We summarize observations of the properties of powerful radio galaxies and
their environments from z = 0 to 5. These data show that some high redshift
radio galaxies inhabit regions of gas and galaxy over-densities indicative of
proto-cluster environments.


title: Chemical Evolution of Galaxies

abstract:
  Chemical evolution of galaxies brings together ideas on stellar evolution and
nucleosynthesis with theories of galaxy formation, star formation and galaxy
evolution, with all their associated uncertainties. In a new perspective
brought about by the Hubble Deep Field and follow-up investigations of global
star formation rates, diffuse background etc., it has become necessary to
consider the chemical composition of dark baryonic matter as well as that of
visible matter in galaxies.


title: On Solar System and Cosmic Rays Nucleosynthesis and Spallation Processes

abstract:
  A brief survey of nuclide abundances in the solar-system and in cosmic rays
and of the believed mechanisms of their synthesis is given. The role of
spallation processes in nucleosynthesis is discussed. A short review of recent
measurements, compilations, calculations, and evaluations of spallation cross
sections relevant to nuclear astrophysics is given as well. It is shown that in
some past astrophysical simulations, old experimental nuclear data and
theoretical cross sections that are in poor agreement with recent measurements
and calculations were used. New astrophysical simulations using recently
measured and reliably calculated nuclear cross sections, further researches in
obtaining better cross sections, and production of evaluated spallation cross
sections libraries for astrophysics are suggested.


title: Eros 2 proper motion survey for halo white dwarfs

abstract:
  Since 1996 EROS 2 has surveyed 440 square degrees at high Galactic latitude
in order to search for high proper motion stars in the Solar neighbourhood. We
present here the analysis of 250 square degrees for which we have three years
of data. No object with halo-like kinematics has been detected. Using a
detailed Monte-Carlo simulation of the observations, we calculate our detection
efficiency for this kind of object and place constraints on their contribution
to various halo models. If 14 Gyr old, the halo cannot be made of more than 18%
of hydrogen white dwarfs (95% C.L.).


title:
Abundance analysis of two extremely metal-poor stars from the
  Hamburg/ESO Survey

abstract:
  We report on the first high spectral resolution analysis of extremely
metal-poor halo stars from the Hamburg/ESO objective-prism survey (HES). The
spectra were obtained with UVES at VLT-UT2. The two stars under investigation
(\object {HE 1303--2708} and \object {HE 1353--2735}) are main-sequence
turnoff-stars having metal abundances of [Fe/H]=-2.85 and -3.20, respectively.
The stellar parameters derived from the UVES spectra are in very good agreement
with those derived from moderate-resolution follow-up spectra. HE 1353--2735 is
a double-lined spectroscopic binary.
  The two stars nicely reproduce the strong scatter in [Sr/Fe] observed for
extremely metal-poor stars. While we see a strong Sr II $\lambda 4215$ {\AA}
line in the spectrum of HE 1303--2708 ([Sr/Fe]=-0.08), we can only give an
upper limit for HE 1353--2735 ([Sr/Fe]<-1.2), since the line is not detected.
We report abundances of Mg, Ca, Sc, Ti, Cr for both stars, and Co, Y for
respect to known trends for metal-poor stars.Lithium is also detected in these
stars, to a level which places them among Lithium-plateau metal-poor dwarfs.


title: Evidences for two Gamma-Ray Burst afterglow emission regimes

abstract:
  We applied cosmological and absorption corrections to the X-ray and optical
afterglow fluxes of a sample of Gamma-Ray Burst sources of known distance. We
find a good correlation in X-rays and that the GRBs in our sample form two well
defined classes. We tentatively interpret them as radiative and adiabatic
afterglow behaviours in the framework of the fireball model for GRBs. We do not
observe this correlation at optical wavelengths. This discrepancy with the
model may be due to the absorption in the source vicinity.


title: Hubble Redshift

abstract:
  The dependence of luminosity distance on observed resdhift and the
cosmological parameters H and q is derived for a contracting Friedmann universe
with no cosmological constant. The result is consistent with recent supernovae
observations.


title: Variable Galaxies in the Hubble Deep Field

abstract:
  We present results from a study to detect variable galaxies in the Hubble
Deep Field North. The goal of this project is to investigate the number density
of AGN at z=1 through the detection of variable galaxy nuclei. The advantage of
HST is the ability to do accurate photometry within smaller apertures, thus
allowing us to probe much lower AGN/host galaxy luminosity ratios than can be
done from the ground. The primary data sets analyzed for galactic variability
follow from the original HDF-N observations in December 1995 and a second epoch
obtained two years later.
  We have detected nuclear variability at or above the 3 sigma level in 8 of
633 HDF galaxies at I<27. Only 2 detections would be expected by chance in a
normal distribution. At least one of these 8 has been spectroscopically
confirmed as a Seyfert 1 galaxy. Based on the AGN structure function for
variability, the estimated luminosity of the varying component in each galaxy
lies in the range -19.5<M<-15.0. We construct an upper limit to the luminosity
function for the variable nuclei and compare this to the local Seyfert LF and
the LF for QSOs at z=1. Assuming we have detected all Seyfert-like nuclei in
the HDF-N, we find no evidence for an increase in the number density of AGN at
M=-19. We estimate that ~1-3% of field galaxies with I<27 may contain a nuclear
AGN.


title: Chandra Observations of the Young Pulsar PSR B0540-69

abstract:
  The young pulsar PSR B0540-69 was one of the first targets observed with the
Chandra X-Ray Observatory. The high angular resolution of Chandra allows us to
resolve the compact nebula surrounding the pulsar. We have determined a
position for PSR B0540-69 of R.A. = 05h 40m 11s.221, decl. = -69o 19' 54".98
(J2000) with a 1-sigma radial uncertainty of 0.7". Combining our measurements
of the pulsar period with previous measurements covering a span of 12 years, we
derive a braking index of 2.08. The spectrum of the pulsed emission is
consistent with a power-law with a photon index of 1.83 +/- 0.13. The compact
nebula has a softer spectrum with a photon index of 1.85 to 2.26.


title: Evolution of Proto-Neutron stars with kaon condensates

abstract:
  We present simulations of the evolution of a proto-neutron star in which
kaon-condensed matter might exist, including the effects of finite temperature
and trapped neutrinos. The phase transition from pure nucleonic matter to the
kaon condensate phase is described using Gibbs' rules for phase equilibrium,
which permit the existence of a mixed phase. A general property of neutron
stars containing kaon condensates, as well as other forms of strangeness, is
that the maximum mass for cold, neutrino-free matter can be less than the
maximum mass for matter containing trapped neutrinos or which has a finite
entropy. A proto-neutron star formed with a baryon mass exceeding that of the
maximum mass of cold, neutrino-free matter is therefore metastable, that is, it
will collapse to a black hole at some time during the Kelvin-Helmholtz cooling
stage.
  The effects of kaon condensation on metastable stars are dramatic. In these
cases, the neutrino signal from a hypothetical galactic supernova (distance
$\sim8.5$ kpc) will stop suddenly, generally at a level above the background in
the SuperK and SNO detectors, which have low energy thresholds and backgrounds.
This is in contrast to the case of a stable star, for which the signal
exponentially decays, eventually disappearing into the background. We find the
lifetimes of kaon-condensed metastable stars to be restricted to the range
40--70 s and weakly dependent on the proto-neutron star mass, in sharp contrast
to the significantly larger mass dependence and range (1--100 s) of
hyperon-rich metastable stars.


title:
Constraints on Galaxy Density Profiles from Strong Gravitational
  Lensing: The Case of B 1933+503

abstract:
  We consider a wide range of parametric mass models for B 1933+503, a
ten-image radio lens, and identify shared properties of the models with the
best fits. The approximate rotation curves varies by less than 8.5% from the
average value between the innermost and the outermost image (1.5h^{-1} kpc to
4.1h^{-1} kpc) for models within 1 \sigma of the best fit, and the radial
dependence of the shear strength and angle also have common behavior for the
best models. The time delay between images 1 and 6, the longest delay between
the radio cores, is \Delta t = (10.6^{+2.4}_{-1.1})h^{-1} days (\Omega_0=0.3,
\lambda_0=0.7) including all the modeling uncertainties. Deeper infrared
observations, to more precisely register the lens galaxy with the radio images
and to measure the properties of the Einstein ring image of the radio source's
host galaxy, would significantly improve the model constraints and further
reduce the uncertainties in the mass distribution and time delay.


title: A Shock-Induced PDR in the HH 80/81 Flow. Far Infrared Spectroscopy

abstract:
  The two spectrometers on board the Infrared Space Observatory were used to
observe the Herbig-Haro objects HH 80, 81 and 80N, as well as their candidate
exciting source IRAS 18162-2048. The fine structure lines of [OI]63um,
[OI]145um and [CII]158um are detected everywhere, while [NII]122um and
[OIII]88um are only detected toward the HH objects; line ratios confirm for the
first time the collisionally excited HH nature of HH 80N. No molecular line is
detected in any of the observed positions. We use a full shock code to diagnose
shock velocities vs~100 km/s toward the HH objects, as expected from the
optical spectroscopy. Since proper motions suggest velocities in excess of 600
km/s, the HH objects probably represent the interface between two flow
components with velocity differing by ~vs. Aside from the flow exciting source,
the [CII]158um line is everywhere brighter than the [OI]63um line, indicating
the presence of a Photo-Dissociation Region (PDR) all along the flow. Continuum
emission from the HH objects and from other positions along the flow is only
detected longword of ~50 micron, and its proportionality to the [CII]158um line
flux suggests it is PDR in origin. We propose that the FUV continuum irradiated
by the HH objects and the jet is responsible for the generation of a PDR at the
walls of the flow cavity. We develop a very simple model which strengthens the
plausibility of this hypothesis.


title: The Real Space Power Spectrum of the PSCz Survey from 0.01 to 300 h/Mpc

abstract:
  We report a measurement of the real space (not redshift space) power spectrum
of galaxies over four and a half decades of wavenumber, 0.01 to 300 h/Mpc, from
the IRAS Point Source Catalog Redshift Survey (PSCz). Since estimates of power
are highly correlated in the nonlinear regime, we also report results for the
prewhitened power spectrum, which is less correlated. The inferred bias between
optically-selected APM and IRAS-selected PSCz galaxies is about 1.15 at linear
scales < 0.3 h/Mpc, increasing to about 1.4 at nonlinear scales > 1 h/Mpc. The
nonlinear power spectrum of PSCz shows a near power-law behaviour to the
smallest scales measured, with mild upward curvature in the broad vicinity of
1.5 h/Mpc. Contrary to the prediction of unbiased Dark Matter models, there is
no prominent inflection at the linear-nonlinear transition scale, and no
turnover at the transition to the stable clustering regime. The nonlinear power
spectrum of PSCz requires scale-dependent bias: all Dark Matter models without
scale-dependent bias are ruled out with high confidence.


title: A Monte Carlo Study of the 6.4 keV Emission at the Galactic Center

abstract:
  Strong fluorescent Fe line emission at 6.4 keV has been observed from the Sgr
B2 giant molecular cloud located in the Galactic Center region. The large
equivalent width of this line and the lack of an apparent illuminating nearby
object indicate that a time-dependent source, currently in a low-activity
state, is causing the fluorescent emission. It has been suggested that this
illuminator is the massive black hole candidate, Sgr A*, whose X-ray luminosity
has declined by an unprecedented six orders of magnitude over the past 300
years. We here report the results of our Monte Carlo simulations for producing
this line under a variety of source configurations and characteristics. These
indicate that the source may in fact be embedded within Sgr B2, although
external sources give a slightly better fit to the data. The weakened
distinction between the internal and external illuminators is due in part to
the instrument response function, which accounts for an enhanced equivalent
width of the line by folding some of the continuum radiation in with the
intrinsic line intensity. We also point out that although the spectrum may be
largely produced by K$\alpha$ emission in cold gas, there is some evidence in
the data to suggest the presence of warm (~10^5 K) emitting material near the
cold cloud.


title: Quasar-galaxy associations revisited

abstract:
  Gravitational lensing predicts an enhancement of the density of bright,
distant QSOs around foreground galaxies. We measure this QSO-galaxy correlation
w_qg for two complete samples of radio-loud quasars, the southern 1Jy and
Half-Jansky samples. The existence of a positive correlation between z~1
quasars and z~0.15 galaxies is confirmed at a p=99.0% significance level
(>99.9%) if previous measurements on the northern hemisphere are included). A
comparison with the results obtained for incomplete quasar catalogs (e.g. the
Veron-Cetty and Veron compilation) suggests the existence of an `identification
bias', which spuriously increases the estimated amplitude of the quasar-galaxy
correlation for incomplete samples. This effect may explain many of the
surprisingly strong quasar-galaxy associations found in the literature.
Nevertheless, the value of w_qg that we measure in our complete catalogs is
still considerably higher than the predictions from weak lensing. We consider
two effects which could help to explain this discrepancy: galactic dust
extinction and strong lensing.


title: Stellar Populations, Bars and Secular Evolution in Late-Type Galaxies

abstract:
  We have done a robust statistical analysis of UBV color profiles of 257 Sbc
barred and unbarred galaxies. We found that there is an excess of barred
galaxies among the objects with null or positive (bluish inward) color
gradients, which seems to indicate that bars act as a mechanism of
homogenization of the stellar population along galaxies. Moreover, the
relationship found between total and bulge colors shows that, in the process of
homogenization, the stellar population of bulges are getting bluer, whereas the
total color of galaxies remains the same. These characteristics are expected in
a secular evolutionary scenario, and seem incompatible with both the monolithic
and the hierarchical scenarios for spiral galaxy formation.


title: Composite Spectra from the FIRST Bright Quasar Survey

abstract:
  We present a very high signal-to-noise ratio composite spectrum created using
657 radio-selected quasars from the FIRST Bright Quasar Survey. The spectrum
spans rest-frame wavelengths 900 - 7500 Angstroms. Additionally we present
composite spectra formed from subsets of the total data set in order to
investigate the spectral dependence on radio loudness and the presence of broad
absorption. In particular, radio-loud quasars are red compared to radio-quiet
quasars, and quasars showing low-ionization broad absorption lines are red
compared to other quasars. We compare our composites with those from the Large
Bright Quasar Survey. Composite quasar spectra have proven to be valuable tools
for a host of applications, and in that spirit we make these publically
available via the FIRST survey web page.


title: Some Consequences of Magnetic Fields in High Energy Sources

abstract:
  Magnetic fields likely play a fundamental intermediary role between gravity
and radiation in many astrophysical rotators. They can, among other things, 1)
induce and be amplified by turbulence, 2) energize coronae, 3) launch and
collimate outflows in ``spring'' or ``fling'' mechanisms. The first is widely
recognized to be important for angular momentum transport, but can also produce
intrinsic variability and possibly vorticity growth. The second leads to the
production of high energy flares, and also facilitates a test of general
relativity from AGN observations. The third can operate from rotators with a
large scale fields, though the origin of the requisite large scale fields is
somewhat unresolved. I discuss these three points in more detail below,
emphasizing some open questions.


title:
A new era of spectroscopy: SINFONI, NIR integral field spectroscopy at
  the diffraction limit of an 8m telescope

abstract:
  SINFONI, the SINgle Faint Object Near-infrared Investigation, is an
instrument for the Very Large Telescope (VLT), which will start its operation
mid 2002 and allow for the first time near infrared (NIR) integral field
spectroscopy at the diffraction limit of an 8-m telescope. SINFONI is the
combination of two state-of-the art instruments, the integral field
spectrometer SPIFFI, built by the Max-Planck-Institut fuer extraterrestrische
Physik (MPE), and the adaptive optics (AO) system MACAO, built by the European
Southern Observatory (ESO). It will allow a unique type of observations by
delivering simultaneously high spatial resolution (pixel sizes 0.025arcsec to
0.25arcsec) and a moderate spectral resolution (R~2000 to R~4500), where the
higher spectral resolution mode will allow for software OH suppression. This
opens new prospects for astronomy.


title:
Thermodynamical properties of stellar matter: II. Internal energy,
  temperature and density exponents and specific heats for stellar interiors

abstract:
  Starting from the Helmholtz free energy we calculate analytically first- and
second-order derivatives, as internal energy and specific heats, for the ideal
system and the exchange and correlation interactions covering a broad range of
degeneracy and relativity. The complex physics of Coulomb interactions is
expressed by Pade Approximants, which reflect the actual state of our knowledge
with high accuracy. We assume complete ionization and provide a base system of
thermodynamical functions from which any other thermodynamical quantities can
be calculated. We chose for the base system the free energy, the pressure, the
internal energy, the isothermal compressibility (or density exponent), the
coefficient of strain (or temperature exponent), and the isochoric specific
heat. By means of the latter potentials entropy, isobaric specific heat and
adiabatic temperature gradient can be determined. We give comparisons with
quantities which are composed by numerical second-order derivatives of the free
energy and show that numerical derivatives of the free energy as calculated,
for instance, from EOS tables, may produce discontinuities for astrophysically
relevant quantities as, e.g., the adiabatic temperature gradient. Adiabatic
temperature gradients are shown for different chemical compositions (hydrogen,
helium, carbon). Finally the used formalism of Pade Approximants allows
immediate incorporation of recent results from many particle statistics.


title:
S 10947 Aql = RX J2009.8+1557: A probable RS CVn star which sometimes
  stops its eclipses

abstract:
  We report the discovery of a new variable star, called S 10947 Aql, as the
likely optical counterpart of RX J2009.8+1557. The optical variability pattern
as well as the detected X-ray emission suggest that it is a chromospherically
active binary of the RS Canum Venaticorum type. We discovered an occasional
disappearance of the eclipsing minima as well as large variations in the
eclipse amplitude. We discuss possible causes of this peculiarity.


title:
Discovery of a Close Pair of z = 4.25 Quasars from the Sloan Digital Sky
  Survey

abstract:
  We report the discovery of a pair of z = 4.25 quasars with a separation of 33
arcseconds. The brighter of the two objects was identified as a high-redshift
quasar candidate from Sloan Digital Sky Survey multicolor imaging data, and the
redshift was measured from a spectrum obtained with the Hobby-Eberly Telescope.
The slit orientation of this observation {\it by chance} included another
quasar, approximately one magnitude fainter and having the same redshift as the
target. This is the third serendipitous discovery of a z > 4 quasar. The
differences in the relative strengths and profiles of the emission lines
suggest that this is a quasar pair and not a gravitational lens. The two
objects are likely to be physically associated; the projected physical
separation is approximately 210 $h_{50}^{-1}$ kpc and the redshifts are
identical to $\approx$ 0.01, implying a radial physical separation of 950
$h_{50}^{-1}$ kpc or less. The existence of this pair is strong circumstantial
evidence that $z \sim 4$ quasars are clustered.


title: First UVES observations of beryllium in very metal-poor stars

abstract:
  We report on a attempt to detect beryllium in two dwarf stars of the Galactic
halo with metallicities below one thousandth solar. The data were obtained
during the Commissioning of the Ultraviolet and Visible Echelle Spectrograph
(UVES) mounted on the ESO VLT Kueyen telescope, and show the potential of UVES
for studies in the UV-optical domain. We claim a beryllium detection in LP
815--43 ([Fe/H]~-2.95,[Be/H]=-13.09) at the 99.7% confidence level, while only
an upper limit can be set for the second target CD -24 17504 ([Fe/H]~-3.30,
[Be/H]~-13.39). These results suggest that the trend of beryllium with
metallicity keeps decreasing as lower metallicities are probed, with no
evidence for flattening. In CD -24 17504 we also analyzed the Li I line at
6708A, and derived a lithium abundance close to the Spite plateau.


title:
The Effects of Dust on the Spectral Energy Distributions of Star-Forming
  Galaxies

abstract:
  I review the effects of dust, both in absorption and in emission, on the
spectral energy distributions (SEDs) of Local star-forming galaxies. The energy
balance between the stellar light absorbed by dust at UV-optical-nearIR
wavelengths and the energy re-emitted by dust in the far infrared (FIR) shows
that the amount of dust extinction affecting the galaxy can be predicted with
simple prescriptions applied to the UV-optical data. The implications of these
results for high redshift galaxies are discussed. Arguments can be given to
support the view that Local starbursts are representative of high-redshift
(z>2), UV-detected, star-forming galaxies. If this is the case, the high
redshift FIR emission will be generally undetected in sub-mm surveys, unless
(1) the bolometric luminosity of the high-z galaxies is comparable to or larger
than that of Local ultraluminous FIR galaxies and (2) their FIR SED contains a
cool dust component.


title:
Broad-Band Spectral Energy Distributions of Active Galactic Nuclei from
  an Accretion Disk with Advective Coronal Flow

abstract:
  We construct a disk-corona model which accounts for the optical-to-X-ray
spectral properties of Seyfert nuclei and QSOs. We study emission spectrum
emerging from a vertical disk-corona structure composed of two-temperature
plasma by solving hydrostatic equilibrium and radiative transfer
self-consistently. A fraction $f$ of viscous heating is assumed to be
dissipated in a corona with a Thomson optical depth of $\tau_c$, where
advective cooling is also included, and a remaining fraction, $1-f$, dissipates
within a main body of the disk. Our model can nicely reproduce the soft X-ray
excess with a power-law shape and the hard tail extending to $\sim$ 50 keV. The
different spectral slopes ($\alpha \sim$ 1.5 below 2keV and $\sim$ 0.5 above,
where $\Fnu \propto \nu^{- \alpha}$) are the results of different emission
mechanisms and different sites; the former slope is due to unsaturated
Comptonization from the innermost zone and the latter is due to a combination
of the Comptonization, bremsstrahlung and a reflection of the coronal radiation
at the disk-corona boundary from the inner to surrounding zone ($\leq$ 300
Schwarzschild radii). The emergent optical spectrum is redder ($\alpha \sim
0.3$) than that of the standard disk ($\alpha \sim -0.3$), being consistent
with observations, due to the different efficiencies of spectral distortion of
disk emission at different radii. Further, we find that the cut-off frequency
of the hard X-ray ($\sim$ coronal electron temperature) and broad-band spectral
shape are insensitive to the black-hole mass, while the peak frequency of the
big blue bump is sensitive to the mass as the peak frequency $\propto
\Mbh^{-1/4}$.


title:
A Search for Point Sources of Cosmic Primary Rays Which Produce Single
  Muon Tracks at Ground Level

abstract:
  An increased data sample of identified secondary muons is collected at
detection level. Project GRAND identifies secondary cosmic ray muons from
electrons utilizing a thin steel absorber and tracking (PWC) chambers. The
resulting angular resolution for the primary is about +/- 5 degrees. Since
there is a 1.5% probability that a 100 GeV gamma primary will produce a single
muon track at ground level, the high statistics allows a search for angular
enhancements due to gammas. More than 100 billion muons are identified and
analyzed. A table of stellar sources is examined.


title:
A Near-Infrared Photometric Survey of Metal-Poor Inner Spheroid Globular
  Clusters and Nearby Bulge Fields

abstract:
  Images recorded through J, H, K, 2.2 micron continuum and CO filters have
been obtained of a sample of metal-poor ([Fe/H] < -1.3) globular clusters in
the inner spheroid of the Galaxy. The shape and color of the upper giant branch
on the (K, J-K) CMD, combined with the K brightness of the RGB-tip, are used to
estimate the metallicity, reddening, and distance of each cluster. CO indices
are used to identify bulge stars, which will bias metallicity and distance
estimates if not removed from the data. Bulge fields were also observed near
each cluster. The slope of the bulge giant branch luminosity function does not
vary between most fields, although the LFs in Baade's Window and near NGC 6273
are significantly shallower than average. The data also suggest that the HB
content may not be uniform throughout the bulge, in the sense that a larger
than average number of red HB stars may occur in fields closest to the Galactic
Center.


title: Corrections to the Predicitions for Atmospheric Neutrino Observations

abstract:
  The theoretical Monte Carlo calculations of the production of neutrinos via
cosmic rays incident upon the earth's atmosphere are examined. The calculations
are sensitive to the assumed ratio of pi+ / pi- production cross sections; this
ratio appears to be underestimated in the theory relative to the experimentally
measured ratio. Since the neutrino detection cross section is three times
larger than that for the antineutrino, the theoretical predicted detection
ratio (nu_mu / nu_e) is correspondingly too large.


title: Oxygen Absorption in M87: Evidence for a Warm+Hot ISM

abstract:
  We present a re-analysis of the ROSAT PSPC data within the central 100 kpc of
M87 to search for intrinsic oxygen absorption similar to that recently measured
in several galaxies and groups. Using a spatial-spectral deprojection analysis
we find the strongest evidence to date for intrinsic oxygen absorption in the
hot gas of a galaxy, group, or cluster. Single-phase plasma models modified by
intervening Galactic absorption cannot fit the 0.2-2.2 keV PSPC data as they
under-predict the 0.2-0.4 keV region and over-predict the 0.5-0.8 keV region
where the emission and absorption residuals are obvious upon visual inspection
of the spectral fits. Since the excess emission between 0.2-0.4 keV rules out
intrinsic absorption from cold gas or dust, the most reasonable model for the
excess emission and absorption features is warm, collisionally ionized gas with
a temperature of ~10^6 K. Simple multiphase models (cooling flow, two phases)
modified by both intervening Galactic absorption and by a single oxygen edge
provide good fits and yield temperatures and Fe abundances of the hot gas that
agree with previous determinations by ASCA and SAX. The multiphase models of
M87 inferred from the PSPC can account for the excess EUV emission observed
with EUVE and the excess X-ray absorption inferred from EINSTEIN and ASCA data
above 0.5 keV. Although the total mass of the warm gas implied by the oxygen
absorption is consistent with the matter deposited by a cooling flow, the
suppression of the mass deposition rate and the distortion of the X-ray
isophotes in the region where the radio emission is most pronounced suggest
some feedback effect from the AGN on the cooling gas. (Abridged)


title:
The South Atlantic Magnetic Field Anomaly and Its Effect on the
  Calculated Production of Atmospheric Neutrinos

abstract:
  The theoretical calculations of the production of neutrinos via cosmic rays
incident upon the earth's atmosphere (Barr et al., 1989; Becker-Szendy et al.,
1992; Bugaev & Naumov, 1989; Gaisser et al, 1988; Honda et al., 1995) are
examined. These calculations use a one-dimensional approximation in the
production, transport, and decay of the produced particles. Examined are
various additional effects of the earth's magnetic field and the
three-dimensional nature of the problem which have the effect of decreasing the
calulated ratio of muon neutrinos to electron neutrinos.


title: The X-ray Spectrum and Light Curve of Supernova 1995N

abstract:
  We report on multi-epoch X-ray observations of the Type IIn (narrow emission
line) supernova SN 1995N with the ROSAT and ASCA satellites. The January 1998
ASCA X-ray spectrum is well fitted by a thermal bremsstrahlung (kT~10 keV,
N_H~6e20 cm^-2) or power-law (alpha~1.7, N_H~1e21 cm^-2) model. The X-ray light
curve shows evidence for significant flux evolution between August 1996 and
January 1998: the count rate from the source decreased by 30% between our
August 1996 and August 1997 ROSAT observations, and the X-ray luminosity most
likely increased by a factor of ~2 between our August 1997 ROSAT and January
1998 ASCA observations, although evolution of the spectral shape over this
interval is not ruled out. The high X-ray luminosity, L_X~1e41 erg/sec, places
SN 1995N in a small group of Type IIn supernovae with strong circumstellar
interaction, and the evolving X-ray luminosity suggests that the circumstellar
medium is distributed inhomogeneously.


title:
Exploring the Structure of Distant Galaxies with Adaptive Optics on the
  Keck-II Telescope

abstract:
  We report on the first observation of cosmologically distant field galaxies
with an high order Adaptive Optics (AO) system on an 8-10 meter class
telescope. Two galaxies were observed at 1.6 microns at an angular resolution
as high as 50 milliarcsec using the AO system on the Keck-II telescope. Radial
profiles of both objects are consistent with those of local spiral galaxies and
are decomposed into a classic exponential disk and a central bulge. A
star-forming cluster or companion galaxy as well as a compact core are detected
in one of the galaxies at a redshift of 0.37+/-0.05. We discuss possible
explanations for the core including a small bulge, a nuclear starburst, or an
active nucleus. The same galaxy shows a peak disk surface brightness that is
brighter than local disks of comparable size. These observations demonstrate
the power of AO to reveal details of the morphology of distant faint galaxies
and to explore galaxy evolution.


title: Quintessence Model and Cosmic Microwave Background

abstract:
  A particular kind of quintessence is considered, with equation of motion
$p_Q/\rho_Q = -1$, corresponding to a cosmological term with time-dependence
$\Lambda(t) = \Lambda(t_0) (R(t_0)/R(t))^{P}$ and we examine how values of
$\Omega_m$ and $\Omega_{\Lambda}$ depend on $P$.


title: The state of two neutrinos moving in the opposite directions

abstract:
  This paper has been withdrawn by the author due to the presented idea is
wrong.


title:
Detection of a Series of X-ray Dips Associated with a Radio Flare in GRS
  1915+105

abstract:
  We report the detection of a series of X-ray dips in the Galactic black hole
candidate GRS 1915+105 during 1999 June 6-17 from observations carried out with
the Pointed Proportional Counters of the Indian X-ray Astronomy Experiment on
board the Indian satellite IRS-P3. The observations were made after the source
made a transition from a steady low-hard state to a chaotic state which
occuered within a few hours. Dips of about 20-160 seconds duration are observed
on most of the days. The X-ray emission outside the dips shows a QPO at ~ 4 Hz
which has characteristics similar to the ubiquitous 0.5 - 10 Hz QPO seen during
the low-hard state of the source. During the onset of dips this QPO is absent
and also the energy spectrum is soft and the variability is low compared to the
non-dip periods. These features gradually re-appear as the dip recovers. The
onset of the occurrence of a large number of such dips followed the start of a
huge radio flare of strength 0.48 Jy (at 2.25 GHz). We interpret these dips as
the cause for mass ejection due to the evacuation of matter from an accretion
disk around the black hole. We propose that a super-position of a large number
of such dip events produces a huge radio jet in GRS 1915+105.


title: Explorations in Hubble Space: A Quantitative Tuning Fork

abstract:
  In order to establish an objective framework for studying galaxy morphology,
we have developed a quantitative two-parameter description of galactic
structure that maps closely on to Hubble's original tuning fork. Any galaxy can
be placed in this "Hubble space", where the x-coordinate measures position
along the early-to-late sequence, while the y-coordinate measures in a
quantitative way the degree to which the galaxy is barred. The parameters
defining Hubble space are sufficiently robust to allow the formation of
Hubble's tuning fork to be mapped out to high redshifts. In the present paper,
we describe a preliminary investigation of the distribution of local galaxies
in Hubble space, based on the CCD imaging atlas of Frei et al. (1996). We find
that barred, weakly-barred, and unbarred galaxies are remarkably well-separated
on this diagnostic diagram. The spiral sequence is clearly bimodal and indeed
approximates a tuning fork: strongly-barred and unbarred spirals do not simply
constitute the extrema of a smooth unimodal distribution of bar strength, but
rather populate two parallel sequences. Strongly barred galaxies lie on a
remarkably tight sequence, strongly suggesting the presence of an underlying
unifying physical process. Rather surprisingly, weakly barred systems do not
seem to correspond to objects bridging the parameter space between unbarred and
strongly barred galaxies, but instead form an extension of the regular spiral
sequence. This relation lends support to models in which the bulges of
late-type spirals originate from secular processes driven by bars.


title: A Magnetic Dynamo Origin For The Sub-mm Excess In Sgr A*

abstract:
  The sub-mm bump observed in the spectrum of Sgr A* appears to indicate the
existence of a compact emitting component within several Schwarzschild radii,
$r_S$, of the nucleus at the Galactic Center. This is interesting in view of
the predicted circularized flow within $\sim 5-10 r_S$, based on detailed
multi-dimensional hydrodynamic simulations of Bondi-Hoyle accretion onto this
unusual object. In this paper, we examine the physics of magnetic field
generation by a Keplerian dynamo subject to the conditions pertaining to Sgr
A*, and show that the sub-mm bump can be produced by thermal synchrotron
emission in this inner region. This spectral feature may therefore be taken as
indirect evidence for the existence of this circularization. In addition, the
self-Comptonization of the sub-mm bump appears to produce an X-ray flux
exceeding that due to bremsstrahlung from this region, which may account for
the X-ray counterpart to Sgr A* discovered recently by {\it Chandra}. However,
the required accretion rate in the Keplerian flow is orders of magnitude
smaller than that predicted by the Bondi-Hoyle simulations. We speculate that
rapid evaporation, in the form of a wind, may ensue from the heating associated
with turbulent mixing of gas elements with large eccentricity as they settle
down into a more or less circular (i.e., low eccentricity) trajectory. The
spectrum of Sgr A* longward of $\sim 1-2$ mm may be generated outside of the
Keplerian flow, where the gas is making a transition from a quasi-spherical
infall into a circularized pattern.


title:
The Nuclear and Circum-nuclear Stellar Population in Seyfert 2 Galaxies:
  Implications for the Starburst-AGN Connection

abstract:
  We report the results of a spectroscopic investigation of a sample of 20 of
the brightest type 2 Seyfert nuclei. Our goal is to search for the direct
spectroscopic signature of massive stars, and thereby probe the role of
circumnuclear starbursts in the Seyfert phenomenon. The method used is based on
the detection of the higher order Balmer lines and HeI lines in absorption and
the Wolf-Rayet feature at $\sim$4680 \AA in emission. These lines are strong
indicators of the presence of young (a few Myrs) and intermediate-age (a few
100 Myrs) stellar populations. In over half the sample, we have detected HeI
and/or strong stellar absorption features in the high-order (near-UV) Balmer
series together with relatively weak lines from an old stellar population. In
three others we detect a broad emission feature near 4680 \AA that is most
plausibly ascribed to a population of Wolf-Rayet stars (the evolved descendants
of the most massive stars). We therefore conclude that the blue and near-UV
light of over half of the sample is dominated by young and/or intermediate age
stars. The ``young'' Seyfert 2's have have larger far-IR luminosities, cooler
mid/far-IR colors, and smaller [OIII]/H$\beta$ flux ratios than the ``old''
ones. These differences are consistent with a starburst playing a significant
energetic role in the former class. We consider the possibility that there may
be two distinct sub-classes of Seyfert 2 nuclei (``starbursts'' and ``hidden
BLR''). However, the fact that hidden BLRs have been found in three of the
``young'' nuclei argues against this, and suggests that nuclear starbursts may
be a more general part of the Seyfert phenomenon.


title:
The peculiar motions of early-type galaxies in two distant regions -
  VII. Peculiar velocities and bulk motions

abstract:
  We present peculiar velocities for 84 clusters of galaxies in two large
volumes at distances between 6000 and 15000 km/s in the directions of
Hercules-Corona Borealis and Perseus-Pisces-Cetus. These velocities are based
on Fundamental Plane (FP) distance estimates for early-type galaxies in each
cluster. We fit the FP using a maximum likelihood algorithm which accounts for
both selection effects and measurement errors, and yields FP parameters with
smaller bias and variance than other fitting procedures. We find a best-fit FP
with coefficients consistent with the best existing determinations. We measure
the bulk motions of the sample volumes using the 50 clusters with the
best-determined peculiar velocities. We find the bulk motions in both regions
are small, and consistent with zero at about the 5% level. The EFAR results are
in agreement with the small bulk motions found by Dale et al. (1999) on similar
scales, but are inconsistent with pure dipole motions having the large
amplitudes found by Lauer & Postman (1994) and Hudson et al. (1999). The
alignment of the EFAR sample with the Lauer & Postman dipole produces a strong
rejection of a large-amplitude bulk motion in that direction, but the rejection
of the Hudson et al. result is less certain because their dipole lies at a
large angle to the main axis of the EFAR sample. We find the bulk motion of our
sample is consistent with most cosmological models that approximately reproduce
the shape and normalisation of the observed galaxy power spectrum. We conclude
that existing measurements of large-scale bulk motions provide no significant
evidence against standard models for the formation of structure.


title: Cosmological Microlensing

abstract:
  Variability in gravitationally lensed quasars can be due to intrinsic
fluctuations of the quasar or due to ``microlensing'' by compact objects along
the line of sight. If disentangled from each other, microlens-induced
variability can be used to study two cosmological issues of great interest, the
size and brightness profile of quasars on one hand, and the distribution of
compact (dark) matter along the line of sight on the other. In particular,
multi-waveband observations are useful for this goal.
  In this review recent theoretical progress as well as observational evidence
for quasar microlensing over the last few years will be summarized. Comparison
with numerical simulations will show where we stand. Particular emphasis will
be given to the questions microlensing can address regarding the search for
dark matter, both in the halos of lensing galaxies and in a cosmologically
distributed form. A discussion of desired observations and required theoretical
studies will be given as a conclusion/outlook.


title: Revealing deuterium Balmer lines in HII regions with VLT-UVES

abstract:
  The search for deuterium Balmer lines with VLT-UVES is reported in HII
regions of the Galaxy and the Magellanic Clouds. The DI lines appear as faint,
narrow emission features in the blue wings of the HI Balmer lines and can be
distinguished from high-velocity HI emission. The previous identification to
deuterium is re-inforced beyond doubt. The detection of D-alpha and D-beta in
Orion (Hebrard et al. 2000) is confirmed and deuterium lines are now detected
up to at least D-eta. The UVES observations provide the first detection of
Balmer DI lines in four new HII regions (M 8, M 16, M 20, and DEM S 103 in
SMC), demonstrating that these lines are of common occurence.


title: Photometric deprojection of edge-on galaxies

abstract:
  Photometric deprojection is used to determine the stellardisk and bulge
parameters for several edgeon galaxies from the FGC catalog. The assumption
that the galaxies of our sample belonging to the fourth (i.e., lowest)
surfacebrightness class in the FGC are edgeon, lowsurfacebrightness (LSB)
galaxies is considered.


title: Can dark matter see itself?

abstract:
  Many independent high-resolution simulations of structure formation in cold
dark matter models show that galactic halos should have singular core profiles.
This is in stark contrast with observations of both low- and high-surface
brightness galaxies, which indicate that the dark matter has almost constant
density in the central parts of halos. Basically there are three possible
avenues to a solution to the problem, which we discuss in turn. Observations of
halo profiles could be more uncertain than previously thought, and higher
resolution observations could reveal that spirals do have a singular core
feature. The highest resolution simulations do not include a baryonic
component, and it is conceivable that violent star formation processes and
similar phenomena can destroy the singular dark matter core and lead to an
almost constant density core profile. Finally, we discuss in more detail the
intriguing possibility that the discrepancy hints at some new exotic physics of
the dark matter. Warm dark matter and self-interacting dark matter are two of
the most promising candidates.


title: s- and r-process elements in two very metal-poor stars

abstract:
  New measurements of neutron-capture elements are presented for two very
metal-poor stars ([Fe/H] ~ -3). One (LP 625-44) has an s-process signature
believed to be due to mass transfer from a now-extinct metal-poor AGB
companion, and the second (CS 22897-008) is one of a number of very metal-poor
stars having high [Sr/Ba] ratios which is not expected from the r-process. In
the s-process star, many elements including lead have been detected, providing
strong constraints on the 13C pocket in the now-extinct AGB star. In the
Sr-rich star, Zn, Y, and Zr are also seen to be overabundant, and several
possible nucleosynthesis mechanisms are discussed.


title:
Spectral Signatures of KiloHertz Quasi-Periodic Oscillations from
  Accreting Neutron Stars

abstract:
  Correlations discovered between millisecond timing properties and spectral
properties in neutron star x-ray binaries are described and then interpreted in
relation to accretion flows in the systems. Use of joint timing and spectral
observations to test for the existence of the marginally stable orbit, a key
prediction of strong field general relativity, is described and observations of
the neutron star x-ray binary 4U1820-303 which suggest that the signature of
the marginally stable orbit has been detected are presented.


title: On the Absorption of X-rays in the Interstellar Medium

abstract:
  We present an improved model for the absorption of X-rays in the ISM intended
for use with data from future X-ray missions with larger effective areas and
increased energy resolution such as Chandra and XMM, in the energy range above
100eV. Compared to previous work, our formalism includes recent updates to the
photoionization cross section and revised abundances of the interstellar
medium, as well as a treatment of interstellar grains and the H2molecule. We
review the theoretical and observational motivations behind these updates and
provide a subroutine for the X-ray spectral analysis program XSPEC that
incorporates our model.


title:
Accelerated Electrons in Cassiopeia A: An Explanation for the Hard X-ray
  Tail

abstract:
  We propose a model for the hard X-ray (> 10 keV) emission observed from the
supernova remnant Cas A. Lower hybrid waves are generated in strong (mG)
magnetic fields, generally believed to reside in this remnant, by shocks
reflected from density inhomogeneities. These then accelerate electrons to
energies of several tens of keV. Around 4% of the x-ray emitting plasma
electrons need to be in this accelerated distribution, which extends up to
electron velocities of order the electron Alfven speed, and is directled along
magnetic field lines. Bremsstrahlung from these electrons produces the observed
hard x-ray emission. Such waves and accelerated electrons have been observed in
situ at Comet Halley, and we discuss the viability of the extrapolation from
this case to the parameters relevant to Cas A.


title:
The Solar Helium Abundance in the Outer Corona Determined from
  Observations with SUMER/SOHO

abstract:
  At altitudes of about 1.05 solar radii or more, the corona above quiet solar
regions becomes essentially isothermal. This obviates many of the difficulties
associated with the inverse problem of determining emission measure
distributions, and allows for fairly straightforward relative element abundance
measurements. We present new values for the He abundance. The first is based on
a reanalysis of the He/O ratio studied previously using data acquired by SUMER.
A more thorough evaluation of the atomic physics for He II, including a
detailed treatment of radiative recombination, increases the predicted emission
in the He II Balmer series compared to earlier analyses. We use a recently
revised value of the O abundance to derive an He/H abundance ratio of 0.038,
(mass fraction, Y=0.13), with an error of ~17% coming mainly from the O
abundance uncertainty. We demonstrate that this result may be affected by
gravitational settling of O relative to He. We also derive an abundance for He
by direct comparison to emission lines of the H I Lyman series, with the result
He/H =0.052 +/- 0.005 (Y=0.17), a value similar to He abundances determined in
the slow speed solar wind.


title:
The Chemical Compositions of the SRd Variable Stars. III. KK Aquilae, AG
  Aurigae, Z Aurigae, W Leo Minoris, and WW Tauri

abstract:
  Chemical compositions are derived from high-resolution spectra for five field
SRd variables. These supergiants not previously analysed are shown to be
metal-poor: KK Aql with [Fe/H] = -1.2, AG Aur with [Fe/H] = -1.8, Z Aur with
[Fe/H] = -1.4, W LMi with [Fe/H] = -1.1, and WW Tau with [Fe/H] = -1.1. Their
compositions are, except for two anomalies, identical to within the measurement
errors with the compositions of subdwarfs, subgiants, and less evolved giants
of the same [Fe/H]. One anomaly is an s-process enrichment for KK Aql, the
first such enrichment reported for a SRd variable. The second and more
remarkable anomaly is a strong lithium enrichment for W LMi, also a first for
field SRds. The Li I 6707 A profile is not simply that of a photospheric line
but includes strong absorption from red-shifted gas, suggesting, perhaps, that
lithium enrichment results from accretion of Li-rich gas. This potential clue
to lithium enrichment is discussed in light of various proposals for lithium
synthesis in evolved stars.


title: Evidence for a Massive Dark Object in NGC 4350

abstract:
  In this work we build a detailed dynamic model for a S0 galaxy possibly
hosting a central massive dark object (MDO). We show that the photometric
profiles and the kinematics along the major and minor axes, including the h3
and h4 profiles, imply the presence of a central MDO of mass M = 1.5 - 9.7 10^8
solar masses, i.e. 0.3-2.8% of the mass derived for the stellar spheroidal
component. Models without MDO are unable to reproduce the kinematic properties
of the inner stars and of the rapidly rotating nuclear gas.
  The stellar population comprise of an exponential disc (27% of the light) and
a diffuse spheroidal component (73% of the light) that cannot be represented by
a simple de Vaucouleurs profile at any radius. The M/L ratios we found for the
stellar components (respectively 3.3 and 6.6) are typical of those of disc and
elliptical galaxies.


title:
An algorithm for cleaning extended interferences in radio astronomical
  records

abstract:
  An algorithm is described for removing extended interferences, for instance
from a radar, which are shorter than the time of passage of a radio source
across the beam of the radio telescope. The algorithm is developed on the basis
of robust procedures with the application of extreme statistics. A procedure of
removing ``jumps'' in observational records is also described. The results of
performance of the algorithms are illustrated in the figures. The cleaning
procedures are included in the standard data reduction system of RATAN-600.


title: Radio identification of decametric sources. I. Catalogue

abstract:
  We describe a method of plotting continuous spectra for radio sources on the
basis of entries of various source catalogues in comparatively large error
boxes around a given sky position. Sources from the UTR-2 catalogue (Braude et
al., 1978, 1979, 1981, 1985, 1994), observed at decametric wavelengths (10--25
MHz) with an antenna beam of about 40', were cross-identified with entries from
other radio catalogues at higher frequencies. Using the CATS database we
extracted all sources within 40' around UTR positions to find candidate
identifications. The spectrum for each source was fitted with a set of curves
using the least squares method to find the best fit. We preferentially selected
radio counterparts whose radio spectrum extrapolated to low frequencies matched
the UTR decametric flux densities, and whose coordinates were close to the
gravity centre of UTR positions. Among all 1822 sources in the UTR catalogue we
found about 350 sources to be blends of two or more sources. As the most
probable true coordinates of the radio counterparts we used positions from the
FIRST, NVSS, TXS, GB6, or PMN catalogues. Using low-frequency sources (26, 38,
85 MHz) from CATS we checked the reliability of some of our identifications. We
show examples `of the above methods, including raw and ``cleaned'' spectra.
Identifications with objects from optical, X-ray and infrared catalogues, as
well as a subsample of UTR sources with ultra-steep spectrum are presented.


title:
Conditions for Shock Revival by Neutrino Heating in Core-Collapse
  Supernovae

abstract:
  Energy deposition by neutrinos can rejuvenate the stalled bounce shock and
can provide the energy for the supernova explosion of a massive star. This
neutrino-heating mechanism, however, is not finally accepted or proven as the
trigger of the explosion. Part of the problem is that the complexity of the
hydrodynamic models often hampers a clear and simple interpretation of the
results. This demands a deeper theoretical understanding of the requirements of
a successful shock revival. A toy model is presented here for discussing the
neutrino heating phase analytically by a time-dependent treatment, which allows
one to calculate the radius and velocity of the supernova shock from global
properties of the gain layer as solutions of an initial value problem. A
criterion is derived for the requirements of shock revival. It confirms the
existence of a minimum neutrino luminosity needed for shock expansion, but also
demonstrates the importance of a sufficiently large mass infall rate to the
shock. The possibility of very energetic neutrino-driven explosions seems
excluded because the total specific energy transferred to nucleons is limited
by about 1e52 ergs per solar mass (about 5 MeV per nucleon) and the total mass
in the gain layer is typically only around 0.1 solar masses. Energy transport
by convection from the region of maximum heating to radii closer behind the
shock is found to support the explosion by reducing the energy loss associated
with the inward advection of neutrino-heated matter through the gain radius.
(abridged)


title:
Disk-jet connection in GRS 1915+105: X-ray soft dips as cause of radio
  flares

abstract:
  We have examined the radio emission characteristics of the micro-quasar GRS
1915+105 during its X-ray emission states as classified by Belloni et al.
(2000). We find that the radio emission is high during the 'chi_1' and 'chi_3'
states (the radio ``plateau'' state) and also during the 'beta' and 'theta'
states when X-ray soft dips are present in the X-ray light curve. For all the
other X-ray states we find that the radio emission is low (< 20 mJy at 2.25
GHz). This result supports the suggestion made by Naik et al. (2000) that the
radio flares are caused by a series of X-ray dip events. To further confirm
this result, we have made a systematic study of all the PCA RXTE observations
for those days when a radio flare was present. We find 11 such observations and
find that all of them are of class 'beta', 'theta' or 'chi'. Further, we have
classified all the RXTE PCA observations obtained from 1996 November to 2000
February (when the radio data is available) and confirm that the radio flux, on
an average, is much higher during the states 'beta', 'theta' and 'chi'. Based
on these results, we argue that the radio flares are caused by the X-ray dips
in the source.


title: The Age of the Inner Halo Globular Cluster NGC 6652

abstract:
  HST (V,I) photometry has been obtained for the inner halo globular cluster
NGC 6652. The photometry reaches approximately 4 mag below the turn-off and
includes a well populated horizontal branch. This cluster is located close to
the Galactic center at a galactocentric distance of approximately 2.0 kpc with
a reddening of E(V-I) = 0.15 +/- 0.02 and has a metallicity of [Fe/H]
approximately -0.85. Based upon Delta(V) between the point on the sub-giant
branch which is 0.05 mag redder than the turn-off and the horizontal branch,
NGC 6652 is 11.7 +/- 1.6 Gyr old. Using this same Delta(V), precise
differential ages for 47 Tuc (a thick disk globular), M107 and NGC 1851 (both
halo clusters) were obtained. NGC 6652 appears to be the same age as 47 Tuc and
NGC 1851 (within +/- 1.2 Gyr), while there is a slight suggestion that M107 is
older than NGC 6652 by 2.3 +/- 1.5 Gyr. As this is a less than 2-sigma result,
this issue needs to be investigated further before a definitive statement
regarding the relative age of M107 and NGC 6652 may be made.


title:
HST observations of star clusters in NGC 1023: Evidence for three
  cluster populations?

abstract:
  Using HST images we have carried out a study of cluster populations in the
nearby S0 galaxy NGC 1023. In two WFPC2 pointings we have identified 221
cluster candidates. The small distance (~9 Mpc) combined with deep F555W and
F814W images allows us to reach about two magnitudes below the expected
turn-over of the globular cluster luminosity function. NGC 1023 appears to
contain at least three identifiable cluster populations: the brighter clusters
show a clearly bimodal color distribution with peaks at V-I = 0.92 and at V-I =
1.15 and in addition there are a number of fainter, more extended objects with
predominantly red colors. Among the brighter clusters, we find that the blue
clusters have somewhat larger sizes than the red ones with mean effective radii
of R(eff) ~ 2 and R(eff) ~ 1.7 pc, respectively. These clusters have luminosity
functions (LFs) and sizes consistent with what is observed for globular
clusters in other galaxies. Fitting Gaussians to the LFs of the blue and red
compact clusters we find turn-over magnitudes of M(TO,blue)=-7.58 and
M(TO,red)=-7.37 in V and dispersions of sigma(V,blue)=1.12 and
sigma(V,red)=0.97. The fainter, more extended clusters have effective radii up
to R(eff) ~ 10-15 pc and their LF appears to rise at least down to M(V) ~ -6,
few of them being brighter than M(V) = -7. We suggest that these fainter
objects may have a formation history distinct from that of the brighter GCs.


title: Bekenstein model and the time variation of the strong coupling constant

abstract:
  We propose to generalize Bekenstein model for the time variation of the fine
structure "constant" $\alpha_{em}$ to QCD strong coupling constant $\alpha_S$.
We find that, except for a ``fine tuned'' choice of the free parameters, the
extension can not be performed trivially without being in conflict with
experimental constraints and this rules out $\alpha_S$ variability. This is due
largely to the huge numerical value of the QCD vacuum gluon condensate when
compared to the matter density of the universe.


title:
A comparison between Pa alpha and H alpha emission: The relation between
  HII region mean reddening, local gas density and metallicity

abstract:
  We measure reddenings to HII regions in NGC 2903, NGC 1512, M51, NGC 4449 and
NGC 6946 from Hubble Space Telescope Pa alpha and H alpha images. Extinctions
range from A_V ~ 5 - 0 depending upon the galaxy. For the galaxies with HST
images in both lines, NGC 2903, NGC 1512 and M51, the Pa alpha and H alpha
emission are almost identical in morphology which implies that little emission
from bright HII regions is hidden from view by regions of comparatively high
extinction. The scatter in the measured extinctions is only +- 0.5 mag.
  We compare the reddenings we measure in five galaxies using the Pa alpha to H
alpha ratios to those measured previously from the Balmer decrement in the LMC
and as a function of radius in M101 and M51. We find that luminosity weighted
mean extinctions of these ensembles of HI regions are correlated with gas
surface density and metallicity. The correlation is consistent with the mean
extinction depending on dust density where the dust to gas mass ratio scales
with the metallicity. This trend is expected if HII regions tend to be located
near the mid-plane of a gas disk and emerge from their parent molecular clouds
soon after birth. In environments with gas densities below a few hundred
Msol/pc^2 star formation rates estimated from integrated line fluxes and mean
extinctions are likely to be fairly accurate.


title:
Clusters AgeS Experiment. Hot subdwarfs and luminous white dwarf
  candidates in the field of the globular cluster M4

abstract:
  We present UBV color magnitude diagrams (CMDs) for the globular cluster M4.
The CMDs show a sequence of four luminous blue stars (V<20, U-V<-0.6) which
appear to be cluster hot subdwarfs. We present spectra for the three brightest
ones. We also note the presence of a population of faint blue objects, likely
to be hot, young white dwarfs (WDs) belonging to the cluster. We have selected
five objects above V=22 mag, bright enough for follow-up ground-based
spectroscopy and present their coordinates and finding charts. We show a
spectrum for variable V46 (Kaluzny et al. 1997) which suggests that it is a hot
subdwarf, along with a new light curve obtained with the ISIS image subtraction
package (Alard 2000). The light curve is unstable, but only one period of
variability is apparent. Two new variables have been discovered, both located
on the cluster red giant branch (RGB). We also present a differential E(B-V)
reddening map and a fiducial sequence for the main sequence, subgiant branch
and red giant branch on the V/B-V CMD for a selected region with uniform
reddening. Based on a comparison with the M5 fiducial sequence we obtain a
reddening estimate of E(B-V)=0.41 mag towards M4, consistent with previous
determinations.


title: AST/RO Observations of Atomic Carbon near the Galactic Center

abstract:
  We present a coarsely-sampled map of the region |l|<=2 degrees, |b|<=0.1
degrees in the 492 GHz 3P1-->3P0 fine structure transition of neutral carbon,
observed with the Antarctic Submillimeter Telescope and Remote Observatory
(AST/RO). The distribution of C[I] emission is similar on the large scale to
that of CO J=1-->0. On average, the ratio of the integrated intensities, I_{C
I}/I_{12CO}, is higher in the Galactic disk than in the Galactic Center region.
This result is accounted for by the absorption of 12CO within the clouds
located in the outer Galactic disk. I_{C I}/I_{12CO} is surprisingly uniform
over the variety of environments near the Galactic Center. On average, C[I] is
optically thin (or as optically thin as 13CO(J=1-->0)) even in the dense
molecular clouds of the Galactic Center region.


title: The Supergiant Shell LMC2: II. Physical Properties of the 10^6 K Gas

abstract:
  LMC2 has the highest X-ray surface brightness of all know supergiant shells
in the Large Magellanic Cloud (LMC). The X-ray emission peaks within the
ionized filaments that define the shell boundary, but also extends beyond the
southern border of LMC2 as an X-ray bright spur. ROSAT HRI images reveal the
X-ray emission from LMC2 and the spur to be truly diffuse, indicating a hot
plasma origin. We have obtained ROSAT PSPC and ASCA SIS spectra to study the
physical conditions of the hot gas interior to LMC2 and the spur. Raymond-Smith
thermal plasma model fits to the X-ray spectra, constrained by HI 21-cm
emission-line measurements of the column density, show the plasma temperature
of the hot gas interior of LMC2 to be kT = 0.1 - 0.7 keV and of the spur to be
kT = 0.1 - 0.5 keV. We have compared the physical conditions of the hot gas
interior to LMC2 with those of other supergiant shells, superbubbles, and
supernova remnants (SNRs) in the LMC. We find that our derived electron
densities for the hot gas inside LMC2 is higher than the value determined for
the supergiant shell LMC4, comparable to the value determined for the
superbubble N11, and lower than the values determined for the superbubble N44
and a number of SNRs.


title: N-Body Simulations of Compact Young Clusters near the Galactic Center

abstract:
  We investigate the dynamical evolution of compact young star clusters (CYCs)
near the Galactic center (GC) using Aarseth's Nbody6 codes. The relatively
small number of stars in the cluster (5,000-20,000) makes real-number N-body
simulations for these clusters feasible on current workstations. Using
Fokker-Planck (F-P) models, Kim, Morris, & Lee (1999) have made a survey of
cluster lifetimes for various initial conditions, and have found that clusters
with a mass <~ 2x10^4 Msun evaporate in ~10 Myr. These results were, however,
to be confirmed by N-body simulations because some extreme cluster conditions,
such as strong tidal forces and a large stellar mass range participating in the
dynamical evolution, might violate assumptions made in F-P models. Here we find
that, in most cases, the CYC lifetimes of previous F-P calculations are 5-30%
shorter than those from the present N-body simulations. The comparison of
projected number density profiles and stellar mass functions between N-body
simulations and HST/NICMOS observations by Figer et al. (1999) suggests that
the current tidal radius of the Arches cluster is ~1.0 pc, and the following
parameters for the initial conditions of that cluster: total mass of 2x10^4
Msun and mass function slope for intermediate-to-massive stars of 1.75 (the
Salpeter function has 2.35). We also find that the lower stellar mass limit,
the presence of primordial binaries, the amount of initial mass segregation,
and the choice of initial density profile (King or Plummer models) do not
significantly affect the dynamical evolution of CYCs.


title:
VSOP observation of the quasar PKS 2215+020: a new laboratory for
  core-jet physics at z=3.572

abstract:
  We report results of a VSOP (VLBI Space Observatory Programme) observation of
a high redshift quasar PKS 2215+020 (z=3.572). The ~1 milliarcsecond resolution
image of the quasar reveals a prominent `core-jet' structure on linear scales
from 5/h to 300/h pc ($H_0=100*h km/(s*Mpc). The brightness temperatures and
sizes of bright features identified in the jet are consistent with emission
from relativistic shocks dominated by adiabatic energy losses. The jet is
powered by the central black hole with estimated mass of ~4*10^9 solar masses.
Comparisons with VLA and ROSAT observations indicate a possible presence of an
extended radio/X-ray halo surrounding 2215+020.


title: Third-dredge-up oxygen in planetary nebulae

abstract:
  The planetary nebulae He 2-436 and Wray 16-423 in the Sagittarius dwarf
galaxy appear to result from nearly twin stars, except that third-dredge-up
carbon is more abundant in He 2-436. A thorough photoionization-model analysis
implies that ratios Ne/O, S/O and Ar/O are significantly smaller in He 2-436,
indicative of third-dredge-up oxygen enrichment. The enrichment of oxygen with
respect to carbon is (7 +/- 4)%. Excess nitrogen in Wray 16-423 suggests third
dredge-up of late CN-cycle products even in these low-mass,
intermediate-metallicity stars.