title: Red Giant Branch stars: the theoretical framework

abstract:
  Theoretical predictions of Red Giant Branch stars' effective temperatures,
colors, luminosities and surface chemical abundances are a necessary tool for
the astrophysical interpretation of the visible--near infrared integrated light
from unresolved stellar populations, the Color-Magnitude-Diagrams of resolved
stellar clusters and galaxies, and spectroscopic determinations of red giant
chemical abundances. On the other hand, the comparison with empirical
constraints provides a stringent test for the accuracy of present generations
of red giant models. We review the current status of red giant stars'
modelling, discussing in detail the still existing uncertainties affecting the
model input physics (e.g., electron conduction opacity, treatment of the
superadiabatic convection), and the adequacy of the physical assumptions built
into the model computations. We compare theory with several observational
features of the Red Giant Branch in galactic globular clusters, such as the
luminosity function bump, the luminosity of the Red Giant Branch tip and the
envelope chemical abundance patterns, to show the level of agreement between
current stellar models and empirical data concerning the stellar luminosities,
star counts, and surface chemical abundances.


title: Variations of Core Luminosity and Solar Neutrino Fluxes

abstract:
  In a Dynamic Solar Model (DSM) the temperature dependences of the pp cycle
neutrinos will be different from the ones determined by solar model
calculations with the luminosity constraint. Instead of the usual neutrino
fluxes pp ~ T^{-1/2}, Be ~ T^8, B ~ T^{18}, we determined by the nuclear
reaction rates formulas pp ~ T^{4.2}, Be ~ T^{-1/2}, B ~ T^{13.5}, for $\tau <
10^2$ years. These latter relations have high significance at estimating the
uncertainties of the solar central temperatures without assuming the luminosity
constraint. Although the purely astrophysical solutions seem to be ruled out,
this is not the case for a model in which astrophysical effects are included
besides the neutrino oscillations. Therefore a combined, DSM+MSW model is
suggested to calculate the observed solar neutrino fluxes. The combined SSM+MSW
fits to the rates+spectra+D/N changes give a bad fit to the total rates,
indicating the need to include the astrophysical factors besides the MSW
effect. The DSM suggest that the core dynamics is induced by intermittent
events of dissipation of rotational energy in the solar core, in relation to
angular momentum dissipation arising from the relative motion of the Sun and
the mass center of the Solar System, and it shifts the allowed ranges of the
MSW parameters into a more acceptable region. The role of the astrophysical
factors in the solar neutrino problem is behind the fact why the ``smoking
guns'' of neutrino oscillations are not found yet.


title:
The Physical Origin of the Scattering Polarization of the Na I D-Lines
  in the Presence of Weak Magnetic Fields

abstract:
  We demonstrate that the atomic alignment of the hyperfine-structure
components of the ground level S$_{1/2}$ of Na {\sc i} and of the upper level
P$_{1/2}$ of the D$_1$ line are practically negligible for magnetic strengths
$B>10 \rm G$, and virtually zero for $B\ga 100 \rm G$. This occurs
independently of the magnetic-field inclination on the stellar surface (also,
in particular, for vertical fields). Consequently, the characteristic
antisymmetric linear-polarization signature of the scattered light in the D$_1$
line is practically suppressed in the presence of magnetic fields larger than
10 G, regardless of their inclination. Remarkably, we find that the scattering
polarization amplitude of the D$_2$ line increases steadily with the magnetic
strength, for vertical fields above 10 G, while the contribution of alignment
to the polarization of the D$_1$ line rapidly decreases. Therefore, we suggest
that spectropolarimetric observations of the ``quiet'' solar chromosphere
showing significant linear polarization peaks in both D$_1$ and D$_2$ cannot be
interpreted in terms of one-component magnetic field models, implying that the
magnetic structuring of the solar chromosphere could be substantially more
complex than previously thought.


title: Infrared Photometric Variability of GX13+1 and GX17+2

abstract:
  We present infrared photometry of the Galactic Bulge X-ray binary systems
GX13+1 and GX17+2 obtained in 1997 July and August using OSIRIS on the 1.8m
Perkins Telescope at Lowell Observatory. GX13+1 clearly varies over ~0.6
magnitudes in the K-band. Our light curve suggests a modulation on a timescale
of ~20 days, which is in agreement with previously proposed orbital periods for
the system. The IR counterpart of GX17+2 is also variable in the K-band over
\~0.8 magnitudes on a timescale of days to weeks, extending the variability
first seen by Naylor, Charles, & Longmore (1991). We discuss the implications
our data have for Deutsch et al's (1999) identification of ``star A'' as the
true IR counterpart of GX17+2. The variability observed in our photometry of
the blend of star A and the foreground star NP Ser implies a ~4 magnitude
intrinsic variation in the K-band for GX17+2.


title:
The origin of the UV excess in powerful radio galaxies: spectroscopy and
  polarimetry of a complete sample of intermediate redshift radio galaxies

abstract:
  We present spectroscopic and polarimetric observations of a complete,
optically unbiased sample of 2Jy radio galaxies at intermediate redshifts (0.15
< z < 0.7). These data -- which cover the nuclear regions of the target
galaxies -- allow us to quantify for the first time the various components that
contribute to the UV excess in the population of powerful, intermediate
redshift radio galaxies. We find that, contrary to the results of previous
surveys -- which have tended to be biased towards the most luminous and
spectacular objects in any redshift range -- the contribution of scattered
quasar light to the UV excess is relatively minor in most of the objects in our
sample. Only 7 objects (32% of the complete sample) show significant
polarization in the rest-frame UV, and none of the objects in our sample is
polarized in the near-UV at the P > 10% level. Careful measurement and
modelling of our spectra have allowed us to quantify the contributions of other
components to the UV excess. We show that nebular continuum (present in all
objects at the 3 -- 40% level), direct AGN light (significant in 40% of
objects), and young stellar populations (significant in 15 -- 50% of objects)
all make important contributions to the UV continuum in the population of
powerful radio galaxies. These results serve to emphasise the multi-component
nature of the UV continuum in radio galaxies. The results also point to an
interesting link betweeen the optical/UV and far-IR properties of our sample
objects, in the sense that the objects with the clearest evidence for
optical/UV starburst activity are also the most luminous at far-IR wavelengths.
This supports the idea that the cooler dust components in radio galaxies are
heated by starbursts rather than by AGN.


title:
Three-Dimensional Studies of the Warm Ionized Medium in the Milky Way
  using WHAM

abstract:
  The Wisconsin H-Alpha Mapper (WHAM) is a high throughput Fabry-Perot facility
developed specifically to detect and explore the warm, ionized component of the
interstellar medium at high spectral resolution. It began operating at Kitt
Peak, Arizona in 1997 and has recently completed the WHAM Northern Sky Survey
(WHAM-NSS), providing the first global view of the distribution and kinematics
of the warm, diffuse H II in the Milky Way. This H-alpha survey reveals a
complex spatial and kinematic structure in the warm ionized medium and provides
a foundation for studies of the temperature and ionization state of the gas,
the spectrum and strength of the ionizing radiation, and its relationship to
other components of the interstellar medium and sources of ionization and
heating within the Galactic disk and halo. More information about WHAM and the
Survey can be found at http://www.astro.wisc.edu/wham/.


title:
An Adaptive Optics Survey of M8-M9 Stars: Discovery of 4 Very Low mass
  Binaries With at Least One System Containing a Brown Dwarf Companion

abstract:
  Use of the highly sensitive Hokupa'a/Gemini curvature wavefront sensor has
allowed for the first time direct adaptive optics (AO) guiding on M8-M9 very
low mass (VLM) stars. An initial survey of 20 such objects (SpT=M8-M9)
discovered 4 binaries. Three of the systems have separations of less than 4.2
AU and similar mass ratios (Delta K<0.8 mag; 0.85<q<1.0). One system, however,
did have the largest Delta K=2.38 mag and sep=14.4 AU yet observed for a VLM
star with a brown dwarf companion. Based on our initial flux limited (Ks<12
mag) survey of 20 M8-M9 stars over 14:26<RA<4:30 hours from the sample of Gizis
et al. (2000) we find a binary fraction in the range 14-24% for M8-M9 binaries
with sep>3 AU. This is likely consistent with the 23+/-5% measured for more
massive (M0-M6) stars over the same separation range. It appears M8-M9 binaries
have a much smaller semi-major axis distribution peak (~4 AU; with no systems
wider than 15 AU) compared to M and G stars which have a broad peak at larger
\~30 AU separations.


title: The Princeton Variability Survey

abstract:
  The Princeton Variability Survey (PVS) is a robotic survey which makes use of
readily available, ``off-the-shelf'' type hardware products, in conjunction
with a powerful set of commercial software products, in order to monitor and
discover variable objects in the night sky. The main goal of the PVS has been
to devise an automated telescope and data reduction system, requiring only
moderate technical and financial resources to assemble, which may be easily
replicated by the dedicated amateur, a student group, or a professional and
used to study and discover a variety of variable objects, such as stars. This
paper describes the hardware and software components of the PVS device as well
as observational results from the initial season of the PVS, including the
discovery of a new bright variable star.


title:
A Thermal Bremsstrahlung Model For the Quiescent X-ray Emission from
  Sagittarius A*

abstract:
  I consider the thermal bremsstrahlung emission from hot accretion flows
(Bondi/ADAFs), taking into account the finite size of the observing telescope's
beam (R_beam) relative to the Bondi accretion radius (R_A). For R_beam >> R_A
soft X-ray emission from the hot interstellar medium surrounding the black hole
dominates the observed emission while for R_beam << R_A hard X-ray emission
from the accretion flow dominates. I apply these models to Chandra observations
of the Galactic Center, for which R_beam ~ R_A. I argue that bremsstrahlung
emission accounts for most of the ``quiescent'' (non-flaring) flux observed by
Chandra from Sgr A*; this emission is spatially extended on scales ~ R_A ~ 1''
and has a relatively soft spectrum, as is observed. If accretion onto the
central black hole proceeds via a Bondi or ADAF flow, a hard X-ray power law
should be present in deeper observations with a flux ~ 1/3 of the soft X-ray
flux; nondetection of this hard X-ray component would argue against ADAF/Bondi
models. I briefly discuss the application of these results to other
low-luminosity AGN.


title:
Constraints on the [Omega_Matter-Omega_Lambda]-plane from Elliptical
  Galaxy Counts ?

abstract:
  Here we present a pilot study into whether elliptical galaxy counts alone,
can place a useful constraint on the Omega_M - Omega_Lambda-plane. The
elliptical galaxy counts are drawn from three surveys: The Millennium Galaxy
Catalogue (16 > B_KPNO > 20), the B-band Parallel Survey (20 > B_AB >24) and
the Hubble Deep Fields (23 > B_AB > 28). The elliptical luminosity function
used in the modeling was derived from a combination of the Millennium Galaxy
Catalogue, the two-degree field galaxy redshift survey and the Sloan Digital
Sky Survey (M_*=-19.90, phi_*=0.0019/Mpc^3 and alpha =-0.75 for
H_o=75km/s/Mpc). We adopt a benchmark model and tweak the various input
parameters by their uncertainties to determine the impact upon the counts. We
find that IF the faint-end slope of the elliptical galaxy luminosity function
is known to better than 0.1$, then over the magnitude range 16 < B < 23 the
counts depend most critically upon the cosmology, and can be used to place a
weak constraint on the [Omega_Matter-Omega_Lambda]-plane.


title: Discovery of the CV ROTSE3 J015118.59-022300.1

abstract:
  We report on the discovery of an outburst from a previously unknown high-
latitude CV we designate ROTSE3 J015118.59-022300.1. The object was first
detected on 2001 Oct 13.291 at m-ROTSE3=14.71+-0.06, after which it faded by
more than 2 magnitudes over 13 d. Spectral analysis confirms a Galactic
location, despite unusual properties that render classification difficult.


title:
Formation of Turbulent Cones in Accretion Disk Outflows and Application
  to Broad Line Regions of Active Galactic Nuclei

abstract:
  We consider the stability of an accretion disk wind to cloud formation when
subject to a central radiation force. For a vertical launch velocity profile
that is Keplerian or flatter and the presence of a significant radiation
pressure, the wind flow streamlines cross in a conical layer. We argue that
such regions are highly unstable, and are natural sites for supersonic
turbulence and, consequently, density compressions. We suggest that combined
with thermal instability these will all conspire to produce clouds. Such clouds
can exist in dynamical equilibrium, constantly dissipating and reforming. As
long as there is an inner truncation radius to the wind, our model emerges with
a biconical structure similar to that inferred by Elvis (2000) for the broad
line region (BLR) of active galactic nuclei (AGN). Our results may also apply
to other disk-wind systems.


title: GRB 010921: Discovery of the First HETE Afterglow

abstract:
  We report the discovery of the optical and radio afterglow of GRB 010921, the
first gamma-ray burst afterglow to be found from a localization by the High
Energy Transient Explorer (HETE) satellite. We present optical spectroscopy of
the host galaxy which we find to be a dusty and apparently normal star-forming
galaxy at z = 0.451. The unusually steep optical spectral slope of the
afterglow can be explained by heavy extinction, A_V > 0.5 mag, along the line
of sight to the GRB. Dust with similar A_V for the the host galaxy as a whole
appears to be required by the measurement of a Balmer decrement in the spectrum
of the host galaxy. Thanks to the low redshift, continued observations of the
afterglow will enable the strongest constraints, to date, on the existence of a
possible underlying supernova.


title: The Expected Redshift Distribution of Gamma-Ray Bursts

abstract:
  We predict the redshift distribution of Gamma-Ray Bursts (GRBs) assuming that
they trace the cosmic star formation history. We find that a fraction >~50% of
all GRBs on the sky originate at a redshift z >~5, even though the fraction of
the total stellar mass formed by z~5 is only ~15%. These two fractions are
significantly different because they involve different cosmological factors
when integrating the star formation rate over redshift. Hence, deep
observations of transient events, such as GRB afterglows or supernovae, provide
an ideal strategy for probing the high-redshift universe. We also show that the
intrinsic distribution of GRB durations is bimodal but significantly narrower
and shifted towards shorter durations than the observed distribution.


title: Galactic Cannibalism: the Origin of the Magellanic Stream

abstract:
  We are in a privileged location in the Universe which allows us to observe
galactic interactions from close range -- the merger of our two nearest dwarf
satellite galaxies, the LMC and SMC. It is important to understand the local
merger process before we can have confidence in understanding mergers at high
redshift. We present high resolution Nbody+SPH simulations of the disruption of
the LMC and SMC and the formation of the Magellanic Stream, and discuss the
implications for galaxy formation and evolution.


title:
Radial orbital anisotropy and the Fundamental Plane of elliptical
  galaxies

abstract:
  The existence of the Fundamental Plane (FP) imposes strong constraints on the
structure and dynamics of elliptical galaxies, and thus contains important
information on the processes of their formation and evolution. Here we focus on
the relations between the FP thinness and tilt and the amount of radial orbital
anisotropy. By using N-body simulations of galaxy models characterized by
observationally motivated density profiles, and also allowing for the presence
of live, massive dark matter halos, we explore the impact of radial orbital
anisotropy and instability on the FP properties. The numerical results confirm
a previous semi--analytical finding: the requirement of stability matches
almost exactly the thinness of the FP. In other words, galaxy models that are
radially anisotropic enough to be found outside the observed FP (with their
isotropic parent models lying on the FP) are unstable, and their end--products
fall back on the FP itself. We also find that a systematic increase of radial
orbit anisotropy with galaxy luminosity cannot explain by itself the whole tilt
of the FP, becoming the galaxy models unstable at moderately high luminosities:
at variance with the previous case their end--products are found well outside
the FP itself (abridged).


title: On the hard X-ray spectra of radio-loud active galaxies

abstract:
  Over the last few years X-ray observations of broad-line radio galaxies
(BLRGs) by ASCA, RXTE and BeppoSAX have shown that these objects seem to
exhibit weaker X-ray reflection features (such as the iron K\alpha line) than
radio-quiet Seyferts. This has lead to speculation that the optically-thick
accretion disc in radio-loud active galactic nuclei (AGN) may be truncated to
an optically-thin flow in the inner regions of the source. Here, we propose
that the weak reflection features are a result of reprocessing in an ionized
accretion disc. This would alleviate the need for a change in accretion
geometry in these sources. Calculations of reflection spectra from an ionized
disc for situations expected in radio-loud AGN (high accretion rate,
moderate-to-high black hole mass) predict weak reprocessing features. This idea
was tested by fitting the ASCA spectrum of the bright BLRG 3C 120 with the
constant density ionized disc models of Ross & Fabian. A good fit was found
with an ionization parameter of \xi ~4000 erg cm s^{-1} and the reflection
fraction fixed at unity. If observations of BLRGs by XMM-Newton show evidence
for ionized reflection then this would support the idea that a high accretion
rate is likely required to launch powerful radio jets.


title: The influence of binary stars on the kinematics of low-mass galaxies

abstract:
  In this paper, the influence of binary stars on the measured kinematics of
dwarf galaxies is investigated. Using realistic distributions of the orbital
parameters (semi-major axis, eccentricity, ...), analytical expressions are
derived for the changes induced by the presence of binary stars in the measured
velocity moments of low-mass galaxies (such as the projected velocity
dispersion and the 4th order Gauss-Hermite coefficient h4). It is shown that
there is a noticeable change in the observed velocity dispersion if the
intrinsic velocity dispersion of a galaxy is of the same order as the binary
velocity dispersion. The kurtosis of the line-of-sight velocity distribution
(LOSVD) is affected even at higher values of the intrinsic velocity dispersion.


title: Cosmological Perturbations

abstract:
  The aim of these lecture notes is to familiarize graduate students and
beginning postgraduates with the basic ideas of linear cosmological
perturbation theory and of structure formation scenarios. We present both the
Newtonian and the general relativistic approaches, derive the key equations and
then apply them to a number of characteristic cases. The gauge problem in
cosmology and ways to circumvent it are also discussed. We outline the basic
framework of the baryonic and the non-baryonic structure formation scenarios
and point out their strengths and shortcomings. Fundamental concepts, such as
the Jeans length, Silk damping and collisionless dissipation, are highlighted
and the underlying mathematics are presented in a simple and straightforward
manner.


title: The Intrinsic Ellipticity of Spiral Disks

abstract:
  We have measured the distribution of intrinsic ellipticities for a sample of
28 relatively face-on spiral disks. We combine H-alpha velocity fields and R
and I-band images to determine differences between kinematic and photometric
inclination and position angles, from which we estimate intrinsic ellipticities
of galaxy disks. Our findings suggest disks have a log-normal distribution of
ellipticities (mean epsilon =0.06) and span a range from epsilon= 0 (circular)
to epsilon=0.2. We are also able to construct a tight Tully-Fisher relation for
our face-on sample. We use this to assess the contribution of disk ellipticity
on the observed Tully-Fisher scatter.


title: WIYN Integral-Field Kinematics of Disk Galaxies

abstract:
  We have completed a new fiber array, SparsePak, optimized for
low-surface-brightness studies of extended sources on the WIYN telescope. We
are now using this array as a measuring engine of velocity and
velocity-dispersion fields of stars and ionized gas in disk galaxies from high
to low surface-brightness. Here we present commissioning data on the velocity
ellipsoids, surface densities and mass-to-light ratios in two blue, high
surface-brightness, yet small disks. If our preliminary results survive further
observation and more sophisticated analysis, then NGC 3949 has sigma_z/sigma_R
>> 1, implying strong vertical heating, while NGC 3982's disk is substantially
sub-maximal. These galaxies are strikingly unlike the Milky Way, and yet would
be seen more easily at high redshift.


title: Quark Stars and Color Superconductivity: A GRB connection ?

abstract:
  At this conference many interesting talks were presented on the plausible
existence of Quark Stars. Other talks dealt with the exotic new phases of quark
matter at very high density. Here, I show how combining these two elements
might offer a new way of tackling the Gamma Ray Burst puzzle.


title:
Selective Absorption Processes as the Origin of Puzzling Spectral Line
  Polarization from the Sun

abstract:
  Magnetic fields play a key role in most astrophysical systems, from the Sun
to active galactic nuclei. They can be studied through their effects on atomic
energy levels, which produce polarized spectral lines. In particular,
anisotropic radiation pumping processes (which send electrons to higher atomic
levels) induce population imbalances that are modified by weak magnetic fields.
Here we report peculiarly polarized light in the He I 10830-\AA multiplet
observed in a coronal filament located at the centre of the solar disk. We show
that the polarized light arises from selective absorption from the ground level
of the triplet system of helium, and that it implies the presence of magnetic
fields of the order of a few gauss that are highly inclined with respect to the
solar radius vector. This disproves the common belief that population
imbalances in long-lived atomic levels are insignificant in the presence of
inclined fields with strengths in the gauss range, and demonstrates the
operation of the ground-level Hanle effect in an astrophysical plasma.


title: Large scale extragalactic jets powered by very-high energy gamma rays

abstract:
  The radiative cooling of electrons responsible for the nonthermal synchrotron
emission of large scale jets of radiogalaxies and quasars requires quasi
continuous (in time and space) production of relativistic electrons throughout
the jets over the scales exceeding 100 kpc. While in the standard paradigm of
large scale jets this implies in situ acceleration of electrons, in this letter
we propose a principally different ``non-acceleration'' origin of these
electrons, assuming that they are implemented all over the length of the jet
through effective development of electromagnetic cascades initiated by
extremely high energy gamma-rays injected into the jet from the central object.
This scenario provides a natural and very economic way to power the jets up to
distances of 100 kpc and beyond.


title: The mass ratio distribution of short period double degenerate stars

abstract:
  Short period double degenerates (DDs) are close white dwarf - white dwarf
binary stars which are the result of the evolution of interacting binary stars.
We present the first definitive measurements of the mass ratio for two DDs,
WD0136+768 and WD1204+450, and an improved measurement of the mass ratio for
WD0957-666. We compare the properties of the 6 known DDs with measured mass
ratios to the predictions of various theoretical models. We confirm the result
that standard models for the formation of DDs do not predict sufficient DDs
with mass ratios near 1. We also show that the observed difference in cooling
ages between white dwarfs in DDs is a useful constraint on the initial mass
ratio of the binary. A more careful analysis of the properties of the white
dwarf pair WD1704+481.2 leads us to conclude that the brighter white dwarf is
older than its fainter companion. This is the opposite of the usual case for
DDs and is caused by the more massive white dwarf being smaller and cooling
faster. The mass ratio in the sense (mass of younger star)/(mass of older star)
is then 1.43+-0.06 rather than the value 0.70+-0.03 given previously.


title:
A survey of extended radio jets in AGN with Chandra and HST: First
  Results

abstract:
  We present the first results from an X-ray and optical survey of a sample of
AGN radio jets with Chandra and HST. We focus here on the first six sources
observed at X-rays, in four of which a bright X-ray jet was detected for the
first time. In three out of four cases optical emission from the jet is also
detected in our HST images. We compare the X-ray morphology with the radio as
derived from improved processing of archival VLA data and we construct spectral
energy distributions (SED) for the most conspicuous emission knots. In most
cases the SEDs, together with the similarity of the X-ray and radio
morphologies, favor an inverse Compton origin of the X-rays. The most likely
origin of the seed photons is the Cosmic Microwave Background, implying the
jets are still relativistic on kiloparsec scales. However, in the first knot of
the PKS 1136-135 jet, X-rays are likely produced via the synchrotron process.
In all four cases bulk Lorentz factors of a few are required. The radio maps of
the two jets not detected by either Chandra or HST suggest that they are less
beamed at large scales than the other four detected sources. Our results
demonstrate that, at the sensitivity and resolution of Chandra, X-ray emission
from extragalactic jets is common, yielding essential information on their
physical properties.


title: The 3-D ionization structure of the planetary nebula NGC6565

abstract:
  A detailed study of the planetary nebula NGC6565 has been carried out on
long-slit echellograms at six, equally spaced position angles. The expansion
velocity field, the c(Hbeta) distribution and the radial profile of the
physical conditions (electron temperature and density) are obtained. The
distance, radius, mass and filling factor of the nebula and the temperature and
luminosity of the central star are derived. The radial ionization structure is
analyzed using both the classical method and the photo-ionization code CLOUDY.
Moreover, we present the spatial structure in a series of images from different
directions. NGC6565 is a young (2000--2500 years), patchy, optically thick
triaxial ellipsoid projected almost pole-on. The matter close to major axis was
swept-up by some accelerating agent forming two faint and asymmetric polar
cups. A large cocoon of almost neutral gas completely embeds the ionized
nebula. NGC6565 is in a recombination phase. The stellar decline started about
1000 years ago, but the main nebula remained optically thin for other 600 years
before the recombination phase occurred. In the near future the ionization
front will re-grow, since the dilution factor due to the expansion will prevail
on the slower and slower stellar decline. NGC6565 is at a distance of
2.0(+-0.5) Kpc and can be divided into three radial zones: the ``fully
ionized'' one, extending up to 0.029--0.035 pc at the equator (0.050 pc at the
poles), the ``transition'' one, up to 0.048--0.054 pc (0.080 pc), the ``halo'',
detectable up to 0.110 pc. The ionized mass (~0.03 Modot) is only a fraction of
the total mass (> 0.15 Modot), which has been ejected by an equatorial enhanced
superwind of 4(+-2)x10^(-5) Modot/yr lasted for 4(+-2)x10^3 years.


title: The VLBA Calibrator Survey - VCS1

abstract:
  A catalog containing milliarcsecond--accurate positions of 1332 extragalactic
radio sources distributed over the northern sky is presented - the Very Long
Baseline Array Calibrator Survey (VCS1). The positions have been derived from
astrometric analysis of dual-frequency 2.3 and 8.4 GHz VLBA snapshot
observations; in a majority of cases, images of the sources are also available.
These radio sources are suitable for use in geodetic and astrometric
experiments, and as phase-reference calibrators in high-sensitivity
astronomical imaging. The VCS1 is the largest high-resolution radio survey ever
undertaken, and triples the number of sources available to the radio astronomy
community for VLBI applications. In addition to the astrometric role, this
survey can be used in active galactic nuclei, Galactic, gravitational lens and
cosmological studies. The VCS1 catalog will soon be available at
www.nrao.edu/vlba/VCS1 .


title: HST/WFPC2 Images of the GG Tauri Circumbinary Disk

abstract:
  We present the first visible wavelength images of the GG Tauri circumbinary
ring, obtained with the Hubble Space Telescope's Wide Field and Planetary
Camera 2. Scattered light from the ring is detected in both V and I band
images. The images show that the ring is smooth, except for a small gap that
could be a shadow caused by material between the stars and the ring. The spokes
seen extending from the stars to the ring in ground-based adaptive optics
images are not seen in our data, which suggests that they may be image
artifacts. The nearside/farside surface brightness ratio is 6.9 in I band,
consistent with forward scattering by small dust grains. The azimuth of the
peak ring surface brightness appears offset by 13 degrees from the azimuth
closest to us, as seen in previous near-IR HST observations. This may indicate
that the ring is warped or somehow shadowed by the circumstellar disks. The
color of the ring is redder than the combined light from the stars as observed
by HST, confirming previous measurements that indicate that circumstellar disks
may introduce extinction of light illuminating the ring. We detect a bright,
compact arc of material 0.3 arcseconds from the secondary star at an azimuth
opposite the primary. It appears to be too large to be a circumstellar disk and
is not at the expected location for dust trapped at a Lagrange point.


title: Inner-shell 1s - 2p Soft X-ray Absorption Lines

abstract:
  The HULLAC atomic code is used to compute wavelengths and oscillator
strengths for the 1s - np inner-shell absorption lines in Li-like to F-like
ions of neon, magnesium, aluminum, silicon, sulfur, argon, calcium, and iron.
Many of these lines are expected to be observed in Chandra and XMM-Newton
high-resolution X-ray spectra of active galaxies. The new atomic data are
incorporated in the ION code for spectral modeling of photoionized plasmas. The
calculated spectra are subsequently compared with the spectrum of NGC 3783 and
show very good agreement. The usefulness of these lines as diagnostics for the
ionization state, column densities, and velocities in line-of-sight
photoionized gas is called attention to.


title:
Galaxies Associated with z~4 Damped Lya Systems: I. Imaging and
  Photometric Selection

abstract:
  This paper describes the acquisition and analysis of imaging data for the
identification of galaxies associated with z~4 damped Lya systems. We present
deep BRI images of three fields known to contain four z~4 damped systems. We
discuss the reduction and calibration of the data, detail the color criteria
used to identify z~4 galaxies, and present a photometric redshift analysis to
complement the color selection. We have found no galaxy candidates closer to
the QSO than 7'' which could be responsible for the damped Lya systems.
Assuming that at least one of the galaxies is not directly beneath the QSO, we
set an upper limit on this damped Lya system of L < L*/4. Finally, we have
established a web site to release these imaging data to the public.


title: Ground-based detection of a vibration-rotation line of HD in Orion

abstract:
  The v =1-0 R(5) line of HD at 2.46um has been detected at the position of
brightest line emission of shocked H2 in the Orion Molecular Cloud. The flux in
this HD line, when compared to that of the previously detected HD 0--0 R(5)
line at 19.43um, suggests that, like the v=1 levels of H2, the v=1 levels of HD
are populated in LTE, despite their much higher rates of spontaneous emission
compared to H2. The higher than expected population of vibrationally excited HD
may be due to chemical coupling of HD to H2 via the reactive collisions HD + H
<--> H2 + D in the shocked gas. The deuterium abundance implied by the
strengths of these lines relative to those of H2 is (5.1 pm 1.9 x 10^-6.


title:
Nonaxisymmetric Evolution of Magnetically Subcritical Clouds: Bar
  Growth, Core Elongation, and Binary Formation

abstract:
  We have begun a systematic numerical study of the nonlinear growth of
nonaxisymmetric perturbations during the ambipolar diffusion-driven evolution
of initially magnetically subcritical molecular clouds, with an eye on the
formation of binaries, multiple stellar systems and small clusters. In this
initial study, we focus on the $m=2$ (or bar) mode, which is shown to be
unstable during the dynamic collapse phase of cloud evolution after the central
region has become magnetically supercritical. We find that, despite the
presence of a strong magnetic field, the bar can grow fast enough that for a
modest initial perturbation (at 5% level) a large aspect ratio is obtained
during the isothermal phase of cloud collapse. The highly elongated bar is
expected to fragment into small pieces during the subsequent adiabatic phase.
Our calculations suggest that the strong magnetic fields observed in some
star-forming clouds and envisioned in the standard picture of single star
formation do not necessarily suppress bar growth and fragmentation; on the
contrary, they may actually promote these processes, by allowing the clouds to
have more than one (thermal) Jeans mass to begin with without collapsing
promptly. Nonlinear growth of the bar mode in a direction perpendicular to the
magnetic field, coupled with flattening along field lines, leads to the
formation of supercritical cores that are triaxial in general. It removes a
longstanding objection to the standard scenario of isolated star formation
involving subcritical magnetic field and ambipolar diffusion based on the
likely prolate shape inferred for dense cores. Continuted growth of the bar
mode in already elongated starless cores, such as L1544, may lead to future
binary and multiple star formation.


title:
The response of the Fe K\alpha line to changes in the X-ray illumination
  of accretion discs

abstract:
  X-ray reflection spectra from photoionized accretion discs in active galaxies
are presented for a wide range of illumination conditions. The energy,
equivalent width (EW) and flux of the Fe K line are shown to depend strongly on
the ratio of illuminating flux to disc flux, Fx/Fdisc, the photon index of the
irradiating power-law, \Gamma, and the incidence angle of the radiation, i.
When Fx/Fdisc \leq 2 a neutral Fe K line is prominent for all but the largest
values of \Gamma. At higher illuminating fluxes a He-like Fe K line at 6.7 keV
dominates the line complex. With a high-energy cutoff of 100 keV, the thermal
ionization instability seems to suppress the ionized Fe K line when \Gamma \leq
1.6. The Fe K line flux correlates with Fx/Fdisc, but the dependence weakens as
iron becomes fully ionized. The EW is roughly constant when Fx/Fdisc is low and
a neutral line dominates, but then declines as the line progresses through
higher ionization stages. There is a strong positive correlation between the Fe
K EW and \Gamma when the line energy is at 6.7 keV, and a slight negative one
when it is at 6.4 keV. This is a potential observational diagnostic of the
ionization state of the disc. Observations of the broad Fe K line which take
into account any narrow component would be able to test these predictions.
Ionized Fe K lines at 6.7 keV are predicted to be common in a simple magnetic
flare geometry. A model which includes multiple ionization gradients on the
disc is postulated to reconcile the results with observations.


title: Morphology of Galaxy Clusters and Sunyaev-Zel'dovich effect

abstract:
  Observations of the X-ray band wavelength reveal an evident ellipticity of
many galaxy clusters atmospheres. The modeling of the intracluster gas with an
ellipsoidal $\beta$-model leads to different estimates for the total
gravitational mass and the gas mass fraction of the cluster than those one
finds for a spherical beta-model. An analysis of a recent Chandra image of the
galaxy cluster RBS797 indicates a strong ellipticity and thus a pronounced
aspherical geometry. A preliminary investigation which takes into account an
ellipsoidal shape for this cluster gives different mass estimates than by
assuming spherical symmetry. We have also investigated the influence of
aspherical geometries of galaxy clusters, and of polytropic profiles of the
temperature on the estimate of the Hubble constant through the
Sunyaev-Zel'dovich effect. We find that the non-inclusion of such effects can
induce errors up to 40 per cent on the Hubble constant value.


title:
Solar Cycle Variation of the Solar Internal Rotation: Helioseismic
  Inversion and Dynamo Modelling

abstract:
  We report our first results on comparing the variations of the solar internal
rotation with solar activity, as predicted by non-linear solar dynamo
modelling, with helioseismic measurements using the SOHO MDI data.


title:
Chandra Observation of a 300 kpc Hydrodynamic Instability in the
  Intergalactic Medium of the Merging Cluster of Galaxies A3667

abstract:
  We present results from the combination of two Chandra pointings of the
central region of the cluster of galaxies A3667. From the data analysis of the
first pointing Vikhlinin et al. reported the discovery of a prominent cold
front which is interpreted as the boundary of a cool gas cloud moving through
the hotter ambient gas. Vikhlinin et al. discussed the role of the magnetic
fields in maintaining the apparent dynamical stability of the cold front over a
wide sector at the forward edge of the moving cloud and suppressing transport
processes across the front. In this Letter, we identify two new features in the
X-ray image of A3667: i) a 300 kpc arc-like filamentary X-ray excess extending
from the cold gas cloud border into the hotter ambient gas; ii) a similar
arc-like filamentary X-ray depression that develops inside the gas cloud. The
temperature map suggests that the temperature of the filamentary excess is
consistent with that inside the gas cloud while the temperature of the
depression is consistent with that of the ambient gas. We suggest that the
observed features represent the first evidence for the development of a large
scale hydrodynamic instability in the cluster atmosphere resulting from a major
merger. This result confirms previous claims for the presence of a moving cold
gas cloud into the hotter ambient gas. Moreover it shows that, although the gas
mixing is suppressed at the leading edge of the subcluster due to its magnetic
structure, strong turbulent mixing occurs at larger angles to the direction of
motion. We show that this mixing process may favor the deposition of a
nonnegligible quantity of thermal energy right in the cluster center, affecting
the development of the central cooling flow.


title: A Submillimeter Survey of Gravitationally Lensed Quasars

abstract:
  Submillimeter (and in some cases millimeter) wavelength continuum
measurements are presented for a sample of 40 active galactic nuclei (probably
all quasars) lensed by foreground galaxies. The object of this study is to use
the lensing boost, anywhere from ~3- 20 times, to detect dust emission from
more typical AGNs than the extremely luminous ones currently accessible without
lensing. The sources are a mix of radio loud and radio quiet quasars, and,
after correction for synchrotron radation (in the few cases where necessary),
23 of the 40 (58%) are detected in dust emission at 850um; 11 are also detected
at 450um. Dust luminosities and masses are derived after correction for lensing
magnification, and luminosities are plotted against redshift from z = 1 to z =
4.4, the redshift range of the sample. The main conclusions are (1)
Monochromatic submillimeter luminosities of quasars are, on average, only a few
times greater than those of local IRAS galaxies; (2) Radio quiet and radio loud
quasars do not differ significantly in their dust lumimosity; (3) Mean dust
luminosities of quasars and radio galaxies over the same redshift range are
comparable; (4) Quasars and radio galaxies alike show evidence for more
luminous and massive dust sources toward higher redshift, consistent with an
early epoch of formation and possibly indicating that the percentage of
obscured AGNs increases with redshift.


title: Evidence for a developing gap in a 10 Myr old protoplanetary disk

abstract:
  We have developed a self-consistent model of the disk around the nearby 10
Myr old star TW Hya which matches the observed spectral energy distribution and
7mm images of the disk. The model requires a significant dust size evolution
and a partially-evacuated inner disk region, as predicted by theories of planet
formation. The outer disk, which extends to at least 140 AU in radius, is very
optically thick at IR wavelengths and quite massive ~0.06 Msun for the
relatively advanced age of this T Tauri star. This implies long viscous and
dust evolution timescales, although dust must have grown to sizes of order ~1cm
to explain the sub-mm and mm spectral slopes. In contrast, the negligible
near-infrared excess emission of this system requires that the disk be
optically thin inside ~4 AU.This inner region cannot be completely evacuated;
we need ~0.5 lunar mass of ~1 micron particles remaining to produce the
observed 10 micron silicate emission. Our model requires a distinct transition
in disk properties at ~4 AU, separating the inner and outer disk. The inner
edge of the optically-thick outer disk must be heated almost frontally by the
star to account for the excess flux at mid-IR wavelengths. We speculate that
this truncation of the outer disk may be the signpost of a developing gap due
to the effects of a growing protoplanet; the gap is still presumably evolving
because material still resides in it, as indicated by the silicate emission,
the molecular hydrogen emission, and by the continued accretion onto the
central star (albeit at a much lower rate than typical of younger T Tauri
stars). TW Hya thus may become the Rosetta stone for our understanding of the
evolution and dissipation of protoplanetary disks.


title:
Faint Submillimeter Counts from Deep 850 Micron Observations of the
  Lensing Clusters A370, A851, and A2390

abstract:
  We present deep 850 micron maps of three massive lensing clusters, A370,
A851, and A2390, with well-constrained mass models. Our cluster exposure times
are more than 2 to 5 times longer than any other published cluster field
observations. We catalog the sources and determine the submillimeter number
counts. The counts are best determined in the 0.3 to 2 mJy range where the
areas are large enough to provide a significant sample. At 0.3 mJy the
cumulative counts are 3.3 (1.3,6.3) 10^4 per square degree, where the upper and
lower bounds in the brackets are the 90% confidence range. The surface density
at these faint count limits enters the realm of significant overlap with other
galaxy populations.The corresponding percentage of the extragalactic background
light (EBL) residing in this flux range is about 45-65%, depending on the EBL
measurement used. Given that 20-30% of the EBL is resolved at flux densities
between 2 and 10 mJy, most of the submillimeter EBL is arising in sources above
0.3 mJy. We also performed a noise analysis to obtain an independent estimate
of the counts. The upper bounds on the counts determined from the noise
analysis closely match the upper limits obtained from the direct counts. The
differential counts from this and other surveys can reasonably be described by
the parameterization n(S)=3 10^4/(0.7 + S^3) per square degree per mJy with S
in mJy, which also integrates to match the EBL.


title: Numerical studies of galaxy formation using special purpose hardware

abstract:
  I review recent progress in numerically simulating the formation and
evolution of galaxies in hierarchically clustering universes. Special emphasis
is given to results based on high-resolution gas dynamical simulations using
the N-body hardware integrator GRAPE. Applications address the origin of the
spin of disk galaxies, the structure and kinematics of damped Lyman-alpha
systems, and the origin of galaxy morphology and of galaxy scaling laws.


title:
On the Nature of Angular Momentum Transport in Nonradiative Accretion
  Flows

abstract:
  The principles underlying a proposed class of black hole accretion models are
examined. The flows are generally referred to as ``convection-dominated,'' and
are characterized by inward transport of angular momentum by thermal convection
and outward viscous transport, vanishing mass accretion, and vanishing local
energy dissipation. We examine the viability of these ideas by explicitly
calculating the leading order angular momentum transport of axisymmetric modes
in magnetized, differentially rotating, stratified flows. The modes are
destabilized by the generalized magnetorotational instability. There are no
inward transporting modes at all unless the magnitude of the (imaginary) Brunt
frequency is comparable to the epicyclic frequency, a condition requiring
substantial levels of dissipation. When inward transporting modes do exist,
they appear at long wavelengths, unencumbered by magnetic tension. Moreover,
very general thermodynamic principles prohibit the complete recovery of
irreversible dissipative energy losses, a central feature of
convection-dominated models. Dissipation of the free energy of differential
rotation inevitably requires outward angular momentum transport. Our results
are in good agreement with global MHD simulations, which find significant
levels of outward transport and energy dissipation, whether or not
destabilizing entropy gradients are present.


title:
A CO Survey of Gravitationally Lensed Quasars with the IRAM
  Interferometer

abstract:
  We present the results of a CO survey of gravitationally lensed quasars,
conducted with the Plateau de Bure Interferometer over the last three years.
Among the 18 objects surveyed, one was detected in CO line emission, while six
were detected in the continuum at 3mm and three in the continuum at 1mm. The
low CO detection rate may at least in part be due to uncertainties in the
redshifts derived from quasar broad emission lines. The detected CO source, the
z=3.2 radio quiet quasar MG0751+2716, is quite strong in the CO(4-3) line and
in the millimeter/submillimeter continuum, the latter being emission from cool
dust. The integrated CO line flux is 5.96 +- 0.45 Jy.km/s, and the total
molecular gas mass is estimated to be in the range M(H_2) = 1.6-3.1 X 10^9
solar masses.


title: Efficient Multi-Gaussian Expansion of galaxies

abstract:
  We describe a simple, efficient, robust and fully automatic algorithm for the
determination of a Multi-Gaussian Expansion (MGE) fit to galaxy images, to be
used as a parametrization for the galaxy stellar surface brightness. In most
cases the least-squares solution found by this method essentially corresponds
to the minimax, constant relative error, MGE approximation of the galaxy
surface brightness, with the chosen number of Gaussians. The algorithm is well
suited to be used with multiple resolution images (e.g., Hubble Space Telescope
[HST] and ground-based). It works orders of magnitude faster and is more
accurate than currently available methods. An alternative, more computing
intensive, fully linear algorithm, that is guaranteed to converge to the
smallest Chi^2 solution, is also discussed. Examples of MGE fits are presented
for objects with HST or ground-based photometry, including galaxies with
significant isophote twist.


title:
Hokupa'a-Gemini Discovery of Two Ultracool Companions to the Young Star
  HD 130948

abstract:
  We report the discovery of two faint ultracool companions to the nearby
(d~17.9 pc) young G2V star HD 130948 (HR 5534, HIP 72567) using the Hokupa'a
adaptive optics instrument mounted on the Gemini North 8-meter telescope. Both
objects have the same common proper motion as the primary star as seen over a 7
month baseline and have near-IR photometric colors that are consistent with an
early-L classification. Near-IR spectra taken with the NIRSPEC AO instrument on
the Keck II telescope reveal K I lines, FeH, and water bandheads. Based on
these spectra, we determine that both objects have spectral type dL2 with an
uncertainty of 2 spectral subclasses. The position of the new companions on the
H-R diagram in comparison with theoretical models is consistent with the young
age of the primary star (<0.8 Gyr) estimated on the basis of X-ray activity,
lithium abundance and fast rotation. HD 130948 B and C likely constitute a pair
of young contracting brown dwarfs with an orbital period of about 10 years, and
will yield dynamical masses for L dwarfs in the near future.


title: Twin jets as a potential distance detector

abstract:
  A preview study of using observational data of proper motions and Doppler
shifted velocities of twin-jets to determine the distance of sources inside and
outside our galaxy is made. We investigate the feasibility of this method by
studying the uncertainty of the distance caused by the uncertainties of the
measured quantities. It shows that, when the motion of components of the jet is
relativistic, then the uncertainty of the distance is within the same order of
the uncertainties of the measured values of proper motions and Doppler shifted
velocities. In particular, when assuming the pattern speed equals the flow
speed in the jet, for 10% uncertainties of the measured quantities, the
uncertainty of the distance caused by them would be well within 13%. With
current technique, this method is realizable. For the convenience of choosing
sources to observe, some sources as potential targets are also listed in this
paper.


title:
Bose-Einstein condensation in dense matter and the third family of
  compact stars

abstract:
  We investigate antikaon condensation in compact star matter using a
relativistic mean field model. Antikaon condensates make the equation of state
softer resulting in a smaller maximum mass star compared to the case without
condensate. It is found that the equation of state including antikaon
condensates gives rise to a stable sequence of compact stars called the third
family beyond the neutron star branch.


title:
Equation of state of dense matter and the minimum mass of cold neutron
  stars

abstract:
  Equilibrium configurations of cold neutron stars near the minimum mass are
studied, using the recent equation of state SLy, which describes in a unified,
physically consistent manner, both the solid crust and the liquid core of
neutron stars. Results are compared with those obtained using an older FPS
equation of state of cold catalyzed matter. The value of M_min\simeq 0.09M_sun
depends very weakly on the equation of state of cold catalyzed matter: it is
0.094 M_sun for the SLy model, and 0.088 M_sun for the FPS one. Central density
at M_min is significantly lower than the normal nuclear density: for the SLy
equation of state we get central density 1.7 10^{14} g/cm^3, to be compared
with 2.3 10^{14} g/cm^3 obtained for the FPS one. Even at M_min, neutron stars
have a small liquid core of radius of about 4 km, containing some 2-3% of the
stellar mass. Neutron stars with 0.09 M_sun <M<0.17 M_sun are bound with
respect to dispersed configuration of the hydrogen gas, but are unbound with
respect to dispersed Fe^56. The effect of uniform rotation on the minimum-mass
configuration of cold neutron stars is studied. Rotation increases the value of
M_min; at rotation period of 10 ms the minimum mass of neutron stars increases
to 0.13 M_sun, and corresponds to the mass-shedding (Keplerian) configuration.
In the case of the shortest observed rotation period of radio pulsars 1.56 ms,
minimum mass of uniformly rotating cold neutron stars corresponds to the
mass-shedding limit, and is found at 0.61 M_sun for the SLy EOS and 0.54 M_sun
for the FPS EOS.


title: The Shapes of Galaxies in the Sloan Digital Sky Survey

abstract:
  We estimate the distribution of apparent axis ratios $q$ for galaxies in the
Sloan Digital Sky Survey (SDSS) Early Data Release. We divide the galaxies by
profile type (de Vaucouleurs versus exponential) as well as by color ($u^* -
r^* \leq 2.22$ versus $u^* - r^* > 2.22$). The axis ratios found by fitting
models to the surface photometry are generally smaller than those found by
taking the second moments of the surface brightness distribution. Using the
axis ratios found from fitting models, we find that galaxies with de
Vaucouleurs profiles have axis ratio distributions which are inconsistent, at
the 99% confidence level, with their being a population of randomly oriented
oblate spheroids. Red de Vaucouleurs galaxies are slightly rounder, on average,
than blue de Vaucouleurs galaxies. By contrast, blue galaxies with exponential
profiles appear very much flatter, on average, than red galaxies with
exponential profiles. The red exponential galaxies are primarily disk galaxies
seen nearly edge-on, with reddening due to the presence of dust, rather than to
an intrinsically red stellar population.


title: What can we learn from EPIC X-ray spectra of Seyfert 1 galaxies?

abstract:
  The EPIC detectors on XMM-Newton provide the most sensitive broad band
(0.3-12 keV) X-ray spectra to date. Observations of 6 Seyfert 1 galaxies,
covering a wide luminosity range, are examined with the aim of identifying the
primary X-ray continuum and constraining superimposed emission and absorption
features. A soft excess emission component is seen in every case, but with a
spectral form which differs markedly with luminosity across our sample. Current
interpretations of the soft excess range from intrinsic thermal emission from
the accretion disc to reprocessing of harder radiation absorbed in the disc
skin. Visual examination of the broad-band EPIC spectra suggest that the
luminosity trend in the observed spectral profiles may be governed primarily by
differences in the line-of-sight absorption. In that case the underlying
continuum could have a common form across the sample. Examination of spectral
features in the Fe K band confirm the common presence of a narrow emission line
at 6.4 keV. Modelling of the EPIC spectra above 7 keV is shown to be critical
to quantifying (or confirming) a broad Fe K line in at least some cases.


title:
Is There a Metallicity--Luminosity Relationship in AGN? The Case of
  Narrow-Line Seyfert 1 Galaxies

abstract:
  The well known relationship between metallicity and luminosity in AGN is
addressed by introducing new metallicity measurements (based on the method of
Hamann & Ferland 1993; HF93) for a sample of narrow-line Seyfert 1 (NLS1)
galaxies. Our new results, based on a sample of 162 AGN, including 9 NLS1s,
indicate that, while broad-line AGN trace a metallicity--luminosity power law
with an index of ~0.2, NLS1s deviate significantly from this relationship at
low luminosities. Adopting the HF93 method based on the N V/C IV line ratio, we
find that NLS1 metallicities are similar to those of some high-redshift
high-luminosity quasars. We also examined the N IV]/C IV line ratio and
compared it with N V/C IV in a sample of 30 sources including several NLS1s. We
find that the two do not give a consistent answer regarding the N/C abundance
ratio. This result is marginal because of the quality of the data. We suggest
two alternative explanations to these results: 1) The HF93
metallicity--luminosity dependence is not a simple two-parameter dependence and
there is an additional hidden variable in this relationship that has not yet
been discovered. The additional parameter may be the accretion rate, the age of
the central stellar cluster or, perhaps, something else. 2) The strong line
ratios involving N V 1240A suggested by HF93 are not adequate metallicity
indicators for NLS1s and perhaps also other AGN for reasons that are not yet
fully understood.


title:
Maximum-likelihood estimation of the CMB power spectrum from
  interferometer observations

abstract:
  A maximum-likelihood method is presented for estimating the power spectrum of
anisotropies in the cosmic microwave background (CMB) from interferometer
observations. The method calculates flat band-power estimates in separate bins
in l-space, together with confidence intervals on the power in each bin. For
multifrequency data, the power spectrum of the other foreground components may
also be recovered. Advantage is taken of several characteristic properties of
interferometer data, which together allow the fast calculation of the
likelihood function. The method may be applied to single-field or mosaiced
observations, and proper account can be taken of non-coplanar baselines. The
method is illustrated by application to simulated data from the Very Small
Array.


title: Theory of Pulsar Winds

abstract:
  I discuss recent work on the nature of relativistic winds from Rotation
Powered Pulsars, on the physics of how they transport energy from the central
compact object to the surrrounding world, and how that energy gets converted
into observable synchrotron emission.


title: Properties of the background of EPIC onboard XMM-Newton

abstract:
  Understanding a background is crucial in particular for a study of low
surface brightness objects. In order to establish the background subtraction
method, we have studied properties of the EPIC background.
  Count rates of the background vary violently by two order of magnitude at the
maximum, while during the most quiet period, these are stable within 8 % at a 1
$\sigma$ level. The overall spectrum is dominated by particle events above 5
keV, and its spatial variation is also found.
  The long-term variation of the background is also investigated with CAL
CLOSED data, which is the data of calibration source with filter closed. The
average background count rate decreased by 20 % from March 2000 to January
2001, but it regained in February 2001.
  For the modeling of the background spectrum, we investigate correlations
between the 2-10 keV count rate and some characteristic parameters. The PN
background shows a good correlation with some parameters. On the other hands,
the MOS background does not shows a clear correlation. Further investigation is
needed for the MOS background.
  Our final goal is to establish a method to predict the background, for which
these results will be reflected in the background generator.


title: The Micro-Jansky Sky at 8.4 GHz

abstract:
  We present the results from two radio integrations at 8.4 GHz using the VLA.
One of the fields, at 13h,+43d (SA13 field), has an rms noise level of 1.49
microJy and is the deepest radio image yet made. Thirty-four sources in a
complete sample were detected above 7.5 microJy and 25 are optically identified
to a limit of I=25.8, using our deep HST and ground-based images. The radio
sources are usually located within 0.5" (typically 5 kpc) of a galaxy nucleus,
and generally have a diameter less than 2.5". The second field at 17h, +50d
(Hercules Field) has an rms noise of 35 microJy and contains 10 sources. We
have also analyzed a complete flux density-limited sample at 8.4 GHz of 89
sources from five deep radio surveys, including the Hubble deep field. Half of
all the optical counterparts are with galaxies brighter than I=23 mag, but 20%
are fainter than I=25.5 mag. We confirm the tendency for the micro-Jansky radio
sources to prefer multi-galaxy systems. The distribution of the radio spectral
index between 1.4 and 8.4 GHz peaks at alpha = -0.75~ with a median value of
-0.6. The average spectral index becomes steeper (lower values) for sources
below 35 microJy, and for sources identified with optical counterparts fainter
than I=25.5 mag. The differential radio count between 7.5 and 1000 microJy has
a slope of -2.11 +/-0.13 and a surface density of 0.64 sources per
square-arcmin with flux density greater than $7.5 microJy.


title: SED, Metallicity and Age of Halo Globular Clusters in M33

abstract:
  In this paper we study the properties of ten halo globular clusters in the
nearby spiral galaxy M33. CCD images of M33 were obtained as a part of the BATC
Colour Survey of the sky in 13 intermediate-band filters from 3800 to
10000{\AA}. By aperture photometry, we obtain the spectral energy distributions
(SEDs) of these globular clusters. We estimate the ages of our sample clusters
by comparing the photometry of each object with theoretical stellar population
synthesis models for different values of metallicity. Our results suggest that
eight of the ten sample halo globular clusters have ``intermediate'' ages, i.e.
between 1 and 8 Gyrs.


title:
Theoretical Uncertainties in the Subgiant--Mass Age Relation and the
  Absolute Age of Omega Cen

abstract:
  The theoretical uncertainties in the calibration of the relationship between
the subgiant mass and age in metal-poor stars are investigated using a Monte
Carlo approach. Assuming that the mass and iron abundance of a subgiant star
are known exactly, uncertainties in the input physics used to construct stellar
evolution models and isochrones lead to a Gaussian 1-sigma uncertainty of
+/-2.9% in the derived ages. The theoretical error budget is dominated by the
uncertainties in the calculated opacities.
  Observations of detached double lined eclipsing binary OGLEGC-17 in the
globular cluster Omega Cen have found that the primary is on the subgiant
branch with a mass of M = 0.809+/-0.012 M_sun and [Fe/H]= -2.29+/-0.15 (Kaluzny
et al. 2001). Combining the theoretical uncertainties with the observational
errors leads to an age for OGLEGC-17 of 11.10+/-0.67 Gyr. The one-sided, 95%
lower limit to the age of OGLEGC-17 is 10.06 Gyr, while the one-sided, 95%
upper limit is 12.27 Gyr.


title: Are galaxies shy ?

abstract:
  Until 1996, there was little evidence that most galaxies were ``shy'', i.e.
that they would hide their stars behind a veil of dust and turn red when
forming stars, radiating the bulk of their luminosity in the infrared (IR) at a
given epoch of their history. Ten years before, IRAS had unveiled a population
of luminous IR galaxies exhibiting such a ``shy'' behavior, the so-called LIGs
and ULIGs (with 12 < log(L[IR]/Lsol < 11 and L[IR]/Lsol > 12 respectively),
which are responsible for the shape of the bolometric luminosity function of
local galaxies above ~ 10^11 Lsol. But integrated over the whole local
luminosity function, LIGs and ULIGs only produce ~ 2 % of the total integrated
luminosity and overall only ~ 30 % of the bolometric luminosity of local
galaxies is radiated in the IR above ~ 5 microns. The discovery of an
extragalactic background in the IR at least as large as the UV-optical-near IR
one, the so-called cosmic infrared background (CIRB), with the COBE satellite
implied that shyness must have been more common among galaxies in the past than
it is today. New results from the Infrared Space Observatory suggest that the
bulk of present-day stars formed at a time when their host galaxies experienced
such a phase of shyness 5 to 10 Gyr ago, i.e. between z= 0.5 and 2. The shyness
of galaxies appears to be induced by galaxy encounters.


title:
ISOCAM observations of Galactic Globular Clusters: mass loss along the
  Red Giant Branch

abstract:
  Deep images in the 10 micron spectral region have been obtained for five
massive Galactic globular clusters, NGC 104 (=47 Tuc), NGC 362, NGC 5139 (omega
Cen), NGC 6388, NGC 7078 (=M15) and NGC 6715 (=M54) in the Sagittarius Dwarf
Spheroidal using ISOCAM in 1997. A significant sample of bright giants have an
ISOCAM counterpart but only < 20% of these have a strong mid-IR excess
indicative of dusty circumstellar envelopes. From a combined physical and
statistical analysis we derive mass loss rates and frequency. We find that i)
significant mass loss occurs only at the very end of the Red Giant Branch
evolutionary stage and is episodic, ii) the modulation timescales must be
greater than a few decades and less than a million years, and iii) mass loss
occurrence does not show a crucial dependence on the cluster metallicity.


title:
Photon Yields of Energetic Particles in the Interstellar Medium: an Easy
  Way to Calculate Gamma-ray Line Emission

abstract:
  A gamma-ray line production calculation in astrophysics depends on i) the
composition and energy source spectrum of the energetic particles, ii) the
propagation model, and iii) the nuclear cross sections. The main difficulty for
model predictions and data interpretation comes from the fact that the spectrum
of the particles which actually interact in the ISM - the propagated spectrum,
is not the same as the source spectrum coming out of the acceleration site, due
to energy-dependent energy losses and nuclear destruction. We present a
different approach to calculate gamma-ray line emission, based on the
computation of the total number of photons produced by individual energetic
nuclei injected in the interstellar medium at a given energy. These photon
yields take into account all the propagation effects once and for all, and
allow one to calculate quickly the gamma-ray line emission induced by energetic
particles in any astrophysical situation by using directly their source
spectrum. Indeed, the same photon yields can be used for any source spectrum
and composition, as well as any target composition. In addition, these photon
yields provide visual, intuitive tools for gamma-ray line phenomenology.


title:
FIRST 0747+2739: A FIRST/2MASS Quasar with an Overabundance of C IV
  Absorption Systems

abstract:
  We present a Keck ESI spectrum of FIRST 074711.2+273904, a K=15.4 quasar with
redshift 4.11 that is detected by both FIRST and 2MASS. The spectrum contains
at least 14 independent C IV absorption systems longward of the Ly-alpha
forest. These systems are found over a path length of Delta z = 0.984,
constituting one of the highest densities per unit redshift of C IV absorption
ever observed. One of the C IV systems is trough-like and resembles a weak
BAL-type outflow. Two of the C IV are ``associated'' absorption systems with
|v|<3000 km/s. Of the 11 remaining systems with v>3000 km/s, eight are either
resolved or require multiple discrete systems to fit the line profiles. In
addition to C IV absorption, there are two low-ionization Mg II absorption
systems along with two damped Ly-alpha systems, at least one of which may be a
C IV system. The overdensity of C IV absorption spans a redshift range of Delta
z=1. Superclusters along the line of sight are unlikely to cause an overdensity
stretching over such a long redshift path, thus the absorption may be an
example of narrow, high-velocity, intrinsic absorption that originates from the
quasar. We suggest that this quasar is a member of a transitional class of BAL
quasars where we are just barely seeing the spatial, density, or temporal edge
of the BAL-producing region (or period); the multiple high-velocity absorption
systems may be the remnants (or precursors) of a stronger BAL outflow. If
correct, then some simpler absorption line complexes in other quasars may also
be due to outflowing rather than intervening material.


title:
Virial masses of galactic halos from galaxy-galaxy lensing: theoretical
  modeling and application to SDSS

abstract:
  We present a theoretical analysis of galaxy-galaxy lensing in the context of
halo models with CDM motivated dark matter profiles. The model enables us to
separate between the central galactic and noncentral group/cluster
contributions. We apply the model to the recent SDSS measurements with known
redshifts and luminosities of the lenses. This allows one to accurately model
the mass distribution of a local galaxy population around and above
$L_{\star}$. We find that virial mass of L* galaxy is
M*=(5-10)x10^{11}h^{-1}M_{\sun}, depending on the color of the galaxy. This
value varies significantly with galaxy morphology with M* for late types being
a factor of 10 lower in u', 7 in g' and a factor of 2.5-3 lower in r', i' and
z' relative to early types. Fraction of noncentral galaxies in groups and
clusters is estimated to be below 10% for late types and around 30% for early
types. Using the luminosity dependence of the signal we find that for early
types the virial halo mass M scales with luminosity as M \propto L^1.4 in red
bands above L*. This shows that the virial mass to light ratio is increasing
with luminosity for galaxies above L*, as predicted by theoretical models. The
virial mass to light ratio in i' band is 17(45)hM_{\sun}/L_{\sun} at L* for
late (early) types. Combining this result with cosmological baryon fraction one
finds that 0.7(0.25)h^{-1}\Upsilon_i\Omega_m/12\Omega_b of baryons within the
virial radius are converted to stars at L*, where \Upsilon_i is the stellar
mass to light ratio in i' band. This indicates that both for early and late
type galaxies around L* a significant fraction of all the baryons in the halo
is transformed into stars.


title: Water maser emission in IC342

abstract:
  The detection of 22 GHz water vapor emission from IC342 is reported, raising
the detection rate among northern galaxies with 100 micron IRAS point source
fluxes > 50 Jy to 16%. The maser, associated with a star forming region 10-15
arcsec west of the nucleus, consists of a single 0.5 km/s wide feature and
reaches an isotropic luminosity of 0.01 solar luminosity (D = 1.8 Mpc). If the
time variability is intrinsic, the maser size is < 1.5 x 10^(16) cm (< 0.5 mas)
which corresponds to a brightness temperature of > 10^(9) K. The linewidth,
luminosity, and rapid variability are reminiscent of the 8 km/s super maser in
Orion-KL. A velocity shift of 1 km/s within two weeks and subsequent rapid
fading is explained in terms of a chance alignment of two dense molecular
clouds. Observations at 22 GHz toward Maffei2 are also reported, yielding a 5
sigma upper limit of 25 mJy for a channel spacing of 1.05 km/s.


title:
Constraints on galaxy halo profiles from galaxy-galaxy lensing and
  Tully-Fisher/fundamental plane relations

abstract:
  Observations of galaxy-galaxy lensing from Sloan Digital Sky Survey (SDSS)
are combined with the Tully-Fisher and fundamental plane relations to derive
constraints on galactic halo profiles.We show that both for early and late type
galaxies around L* the rotation velocity drops significantly from its peak
value at the optical radius to the virial radius, v_opt/v_200 \sim 1.8 with
about 20% uncertainty. Such a drop is expected in models in which the halo
profile is very concentrated, so that it declines steeper than isothermal at
large radii. This large drop can be explained as a result of both a
concentrated dark matter profile and a significant stellar contribution to the
rotation velocity at the optical radii. We model the stellar component with a
thin rotationally supported disk or a Hernquist profile and use adiabatic dark
matter response model to place limits on the halo concentration as a function
of the stellar mass to light ratio. For reasonable values of the latter we find
concentrations consistent with CDM predictions, suggesting there is no evidence
for low concentrations for the majority of halos in the universe. We also
discuss the origin of Faber-Jackson relation L \propto sigma^4 in light of L
\propto v_200^2.5 relation found for early type galaxies from galaxy-galaxy
lensing. This leads to a decrease in v_opt/v_{200} with luminosity above L*, so
that at 7L_* the ratio is 1.4. This is expected from the fundamental plane
relation and implies that relations such as Tully-Fisher and Faber-Jackson are
not simply relations between the mass of dark matter halo and galaxy
luminosity, but are also significantly influenced by the baryonic effects on
the rotation velocity at optical radii.


title: The population of massive X-ray binaries I. The Large Magellanic Cloud

abstract:
  We present high resolution blue spectroscopy of an almost complete sample of
optical counterparts to massive X-ray binaries in the Large Magellanic Cloud
(LMC) and derive their spectral classification. We find an spectral type B0II
for the optical counterpart to RX J0532.5-6551, confirming it as the first
wind-fed massive X-ray binary in the LMC. We also confirm the Be nature of the
proposed counterpart to RX J0535.0-6700. The proposed optical counterpart to RX
J0531.5-6518 is a B2V star with signs of emission in the Balmer lines. In
total, we give accurate spectral types for 14 counterparts. We find that the
overall observed population of massive X-ray binaries in the LMC has a
distribution not very different from the observed Galactic population and we
discuss different selection effects affecting our knowledge of this population.
The spectral distribution of the Be/X-ray binary population is also rather
similar to the Galactic one. This distribution implies that Be/X-ray binaries
must have preferentially formed from moderately massive binaries undergoing
semi-conservative evolution. The observation of several Be/X-ray binaries with
large eccentricities implies then the existence of supernova kicks.


title: Intracluster Planetary Nebulae

abstract:
  We review the progress of research on intracluster planetary nebulae (IPN).
In the past five years, hundreds of IPN candidates have been detected in the
Virgo and Fornax galaxy clusters and searches are also underway in poorer
galaxy groups. From the observations to date, and applying the known properties
of extragalactic planetary nebulae, the intracluster light in Virgo and Fornax:
1) is significant, at least 20% of the total cluster stellar luminosity, 2) is
elongated in Virgo along our line of sight, and 3) may derive from
lower-luminosity galaxies, consistent with some models of intracluster star
production. A fraction of IPN candidates are not true IPN, but emission-line
sources of very large observed equivalent width (> 200 A). The most likely
source for these contaminating objects are Lyman-alpha galaxies at z ~ 3.1.
Follow-up spectroscopy of the IPN candidates will be crucial to discriminate
against high redshift galaxies and to derive the velocity field of the
intracluster stellar population.


title:
Pristine CNO abundances from Magellanic Cloud B stars I. The LMC cluster
  NGC 2004 with UVES

abstract:
  We present chemical abundances for four main sequence B stars in the young
cluster NGC 2004 in the Large Magellanic Cloud (LMC). Apart from H II regions,
unevolved OB-type stars are currently the only accessible source of present-day
CNO abundances for the MCs not altered by stellar evolution. Using UVES on the
VLT, we obtained spectra of sufficient resolution (R = 20 000) and
signal-to-noise (S/N > 100) to derive abundances for a variety of elements (He,
C, N, O, Mg and Si) with NLTE line formation.
  This study doubles the number of main sequence B stars in the LMC with
detailed chemical abundances. More importantly and in contrast to previous
studies, we find no CNO abundance anomalies brought on by e.g. binary
interaction or rotational mixing. Thus, this is the first time that abundances
from H II regions in the LMC can sensibly be cross-checked against those from B
stars by excluding evolutionary effects. We confirm the H II-region CNO
abundances to within the errors, in particular the extraordinarily low nitrogen
abundance of epsilon(N) around 7.0. Taken at face value, the nebular carbon
abundance is 0.16 dex below the B-star value which could be interpreted in
terms of interstellar dust depletion. Oxygen abundances from the two sources
agree to within 0.03 dex.
  In comparison with the Galactic thin disk at MC metallicities, the Magellanic
Clouds are clearly nitrogen-poor environments.


title:
E1 transitions between states with n = 1 to 6 in helium-like carbon,
  nitrogen, oxygen, neon, silicon, and argon

abstract:
  Wavelengths and transition rates are given for E1 transitions between singlet
S, P, D, and F states, between triplet S, P, and D states, and between triplet
P and singlet S states in ions of astrophysical interest: helium-like carbon,
nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between
states with J < 4 and n < 7 are considered. Energy levels and wave functions
used in calculations of the transition rates are obtained from relativistic
configuration-interaction calculations that include both Coulomb and Breit
interactions.


title: Rotation and Activity in Mid-M to L Dwarfs

abstract:
  We analyze rotation velocities and chromospheric (H-alpha) activity, derived
from multi-year, high-resolution spectra, in 56 mid-M to L dwarfs. Rotational
velocities are found to increase from mid-M to L. This is consistent with a
lengthening of spin-down timescale with later type, though in the L types the
trend may also be a function of stellar age. From M5 to M8.5, a saturation-type
rotation-activity relation is seen, similar to that in earlier types. However,
the saturation velocity in our case is much higher, at about 12 km/s. A sharp
drop in activity is observed at about M9, with later types showing little or no
H-alpha emission, in spite of rapid rotation. This may be due to the very high
resistivities in the predominantly neutral atmospheres of these cool objects.


title: Europium Isotopic Abundances in Very Metal-poor Stars

abstract:
  Europium isotopic abundance fractions are reported for the very metal-poor,
neutron-capture-rich giant stars CS 22892-052, HD 115444, and BD +17 3248. The
abundance fractions, derived from analysis of several strong Eu II lines
appearing in high-resolution spectra of these stars, are in excellent agreement
with each other and with their values in the Solar System:
fraction(\iso{Eu}{151}) ~= fraction(\iso{Eu}{153}) ~= 0.5. Detailed abundance
studies of very metal-poor stars have previously shown that the total elemental
abundances of stable atoms with atomic numbers z >= 56 typically match very
closely those of a scaled solar-system r-process abundance distribution. The
present results for the first time extend this agreement to the isotopic level.


title: Wind Accretion and Binary Evolution of the Microquasar LS 5039

abstract:
  There is much evidence to suggest that stellar wind capture, rather than
Roche lobe overflow, serves as the accretion mechanism onto the compact
secondary object in the massive X-ray binary LS 5039. The lack of significant
emission combined with only a modest X-ray flux provide observational evidence
that no large-scale mass transfer is occurring (consistent with our estimate of
the radius of the O6.5 V((f)) optical star that is smaller than its critical
Roche radius). Here we determine the mass loss rate of the optical star from
the broad, residual emission in the H-alpha profile. Using a stellar wind
accretion model for a range in assumed primary mass, we compute the predicted
X-ray luminosity for the system. We compare our results to the observed X-ray
luminosity to determine the mass of the compact object for each case. The
companion appears to be a neutron star with a mass between 1 and 3 solar
masses. With our new constraints on the masses of both components, we discuss
their implications on the evolution of the system before and after the
supernova event that created the compact companion. The binary experienced
significant mass loss during the supernova, and we find that the predictions
for the resulting runaway velocity agree well with the observed peculiar space
velocity. LS 5039 may be the fastest runaway object among known massive X-ray
binaries.


title:
Faraday Rotation Measures in the Parsec-Scale Jets of the Radio Galaxies
  M87, 3C 111, and 3C 120

abstract:
  Parsec-scale Faraday rotation measure (RM) maps are presented for the radio
galaxies M87, 3C 111, and 3C 120. These Very Long Baseline Array observations
were made at 8, 12, and 15 GHz. M87 has an extreme RM distribution that varies
from -4000 radians m^-2 to more than 9000 radians m^-2 across a projected
distance of 0.3 pc in its jet. M87 has no polarized flux closer than 17 mas
from the core. 3C 111 and 3C 120 both show polarized emission in their cores
that is consistent with the expectations of unified schemes for these
broad-line radio galaxies. 3C 111 has an RM gradient that increases from -200
radians m^-2 four mas from the core to -750 radians m^-2 on the side of the jet
closest to the core. 3C 120 has a more moderate RM distribution in the jet of
approximately 100 radians m^-2, but this increases by an order of magnitude in
the core.


title: HI Observations of the Stephan's Quintet

abstract:
  Using the VLA, we have made spectral-line and continuum observations of the
neutral hydrogen in the direction of the compact group of galaxies Stephan's
Quintet. The high-velocity clouds between 5600 and 6600 km/s, the disk of the
foreground galaxy, NGC 7320, at 800 km/s, the extended continuum ridge near the
center of the group, and 3 faint dwarf-like galaxies in the surrounding field
were imaged with C, CS, and D arrays. Four of the HI clouds previously detected
are confirmed. The two largest HI features are coincident with and concentrated
mainly along separate large tidal tails that extend eastward. The most diffuse
of the four clouds is resolved into two clumps, one coincide with tidal
features south of NGC 7318a and the other devoid of any detectable stellar or
Halfa sources. The two compact clouds, along the same line of sight, have peak
emission at luminous infrared and bright Halfa sources probably indicative of
star-forming activity. The total amount of HI detected at high redshifts is ~
10**10Msol. As in previous HI studies of the group, no detectable emission was
measured at the positions of any high-redshift galaxies so that any HI still
bound to their disks must be less than 2.4 x 10**7Msol.


title: AGN-Galaxy Clustering with the Panoramic Deep Fields

abstract:
  The AGN-galaxy cross-correlation function of radio-quiet AGN and radio
galaxies has been measured with the Panoramic Deep Fields. Colour selection
criteria and photometric redshifts have been used to significantly increase the
signal-to-noise of the angular cross-correlation function. Radio-quiet AGN
environments are comparable to the environments of early-type galaxies at low
redshift. The radio galaxy-galaxy spatial cross-correlation function is very
strong though large variations are observed from field-to-field. These
variations appear to be caused by large-scale-structure on scales comparable to
the 5 degree field-of-view. The distribution and spatial cross-correlation
function of radio galaxies and clusters in the Panoramic Deep Fields is
consistent with these objects tracing the same structures at z<0.7. No evidence
is found for evolution of the AGN-galaxy spatial cross-correlation function
across the redshift range observed.


title: GRB010921: Localization and Observations by the HETE Satellite

abstract:
  On September 21 at 18950.56 SOD (05:15:50.56) UT the FREGATE gamma-ray
instrument on the High Energy Transient Explorer (HETE) detected a bright
gamma-ray burst (GRB). The burst was also seen by the X-detector on the WXM
X-ray instrument and was therefore well-localized in the X direction; however,
the burst was outside the fully-coded field-of-view of the WXM Y-detector, and
therefore information on the Y direction of the burst was limited.
Cross-correlation of the HETE and Ulysses time histories yielded an
Interplanetary Network (IPN) annulus that crosses the HETE error strip at a ~45
degree angle. The intersection of the HETE error strip and the IPN annulus
produces a diamond-shaped error region for the location of the burst having an
area of 310 square arcminutes. Based on the FREGATE and WXM light curves, the
duration of the burst is characterized by a t90 = 18.4 s in the WXM 4 - 25 keV
energy range, and 23.8 s and 21.8 s in the FREGATE 6 - 40 and 32 - 400 keV
energy ranges, respectively. The fluence of the burst in these same energy
ranges is 4.8 10^{-6}, 5.5 10^{-6}, and 11.4 10^{-6} erg cm^{-2}, respectively.
Subsequent optical and radio observations by ground-based observers have
identified the afterglow of GRB010921 and determined an apparent redshift of z
= 0.450.


title: CMBR constraints on $R^2$ gravity

abstract:
  Considering the inflation model based on a $f(R)$ gravity theory, we obtain
several important constraints from the large angular scale CMBR observations.
First, the ordinary slow-roll assumption during the inflation together with
Harrison-Zel'dovich spectral conditions chooses $R^2$ gravity as a unique
candidate. Second, the $R^2$ gravity leads to specific near scale-invariant
Harrison-Zel'dovich spectra both for the scalar and the tensor perturbations.
Third, using the COBE-DMR data we derive the strong constraints on the coupling
constant and the energy scale during the inflation. Also, our result shows the
gravitational wave contribution to the CMBR anisotropy is negligible. So, the
future observation can provide the strong constraints on the inflation model
based on $R^2$ gravity. This is a summary of a talk presented in COSMO-01, and
the more completed published version can be found in astro-ph/0102423.


title:
Early Enrichment of the Intergalactic Medium and its Feedback on Galaxy
  Formation

abstract:
  Supernova-driven outflows from early galaxies may have had a large impact on
the kinetic and chemical structure of the intergalactic medium (IGM). We use
three-dimensional Monte Carlo cosmological realizations of a simple linear
peaks model to track the time evolution of such metal-enriched outflows and
their feedback on galaxy formation. We find that at most 30% of the IGM by
volume is enriched to values above 10^-3 solar in models that only include
objects that cool by atomic transitions. The majority of enrichment occurs
relatively early (5 < z < 12) and resulting in a mass-averaged cosmological
metallicity between 10^-3 and 10^-1.5 solar. The inclusion of Population III
objects that cool through H2 line emission has only a minor impact on these
results: increasing the mean metallicity and filling factor by at most a factor
of 1.4, and moving the dawn of the enrichment epoch to a redshift of
approximately 14 at the earliest. Thus enrichment by outflowing galaxies is
likely to have been incomplete and inhomogeneous, biased to the areas near the
starbursting galaxies themselves. Models with a 10% star formation efficiency
can satisfactorily reproduce the nearly constant (2 < z < 5, Z approximately
3.5 x 10^-4 solar) metallicity of the low column density Ly-alpha forest
derived by Songaila (2001), an effect of the decreasing efficiency of metal
loss from larger galaxies. Finally, we show that IGM enrichment is intimately
tied to the ram-pressure stripping of baryons from neighboring perturbations.
This results in the suppression of at least 20% of the dwarf galaxies in the
mass range 10^8.5 to 10^9.5 solar, in all models with filling factors greater
than 2%, and an overall suppression of approximately 50% of dwarf galaxies in
the most observationally-favored model.


title: Alpha-process elements in the Galaxy: a possible GAIA contribution

abstract:
  The sensitivity of stellar spectra to alpha/Fe abundance changes is
investigated with the aim to be detected photometricly and employed for
scientific goals of the GAIA mission. A grid of plane parallel, line blanketed,
flux constant, LTE model atmospheres with different [alpha/Fe] ratios was
calculated. As a first step, the modelled stellar energy fluxes for solar-type
stars and giants were computed and intercompared. The spectral sensitivity
talpha/Fe abundance changes is noticeable and has to be taken into account when
selecting photometric filters for GAIA. The Ca II H and K lines and Mg I b
triplet are the most sensitive direct indicators of alpha/Fe abundance changes.


title: Neutron Star Masses, Radii and Equation of State

abstract:
  A review of current neutron star masses and radius measurements is given and
the resulting constraints on modern equation of states for nuclear matter.
Phase transitions in particular to quark matter is discussed and the novel
color superconducting mixed phases.


title: MHD inverse cascade in the early Universe

abstract:
  We have carried out numerical simulations of freely decaying
magnetohydrodynamic (MHD) turbulence in three dimensions, which can be applied
to the evolution of stochastic magnetic fields in the early Universe. For
helical magnetic fields an inverse cascade effect is observed in which magnetic
helicity and energy is transfered from smaller scales to larger scales,
accompanied by power law growth in the characteristic length scale of the
magnetic field. The magnetic field quickly reaches a scaling regime with
self-similar evolution, and power law behaviour at high wavenumbers. We also
find power law decay in the magnetic and kinematic energies.


title: On the nature of the Extremely Red Galaxies

abstract:
  We present a method based on two broad-band colors to investigate the nature
of the Extremely Red Objects (EROs), i.e., the galaxies selected to have very
red optical-to-infrared colors. Dusty starburst and old ellipticals at
redshifts between 1 and 2 appear to occupy two different regions of the J-K vs.
I-K color diagram, allowing for an easy classification. This diagnostic was
applied to a complete sample of 57 EROs: the two populations are found to be
present in the sample in similar abundances. The cosmic star formation density
in the dusty starbursts is found to be of the order of that in the Lyman-Break
Galaxies.


title: Discovery of a new Transient X-ray Pulsar in the Small Magellanic Cloud

abstract:
  Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have
revealed a previously unknown transient X-ray pulsar with a pulse period of
95s. Provisionally designated XTE SMC95, the pulsar was detected in three
Proportional Counter Array observations during an outburst spanning 4 weeks in
March/April 1999. The pulse profile is double peaked reaching a pulse fraction
\~0.8. The source is proposed as a Be/neutron star system on the basis of its
pulsations, transient nature and characteristically hard X-ray spectrum. The
2-10 keV X-ray luminosity implied by our observations is > 2x10^37 erg/s which
is consistent with that of normal outbursts seen in Galactic systems. This
discovery adds to the emerging picture of the SMC as containing an extremely
dense population of transient high mass X-ray binaries.


title:
Extended Power-Law Decays in BATSE Gamma-Ray Bursts: Signatures of
  External Shocks?

abstract:
  The connection between Gamma-Ray Bursts (GRBs) and their afterglows is
currently not well understood. Afterglow models of synchrotron emission
generated by external shocks in the GRB fireball model predict emission
detectable in the gamma-ray regime ($\gax 25$ keV). In this paper, we present a
temporal and spectral analysis of a subset of BATSE GRBs with smooth extended
emission tails to search for signatures of the ``early high-energy afterglow'',
i.e., afterglow emission that initially begins in the gamma-ray phase and
subsequently evolves into X-Ray, uv, optical, and radio emission as the blast
wave is decelerated by the ambient medium. From a sample of 40 GRBs we find
that the temporal decays are best described with a power-law $\sim t^{\beta}$,
rather than an exponential, with a mean index $<\beta > \approx -2$. Spectral
analysis shows that $\sim 20%$ of these events are consistent with fast-cooling
synchrotron emission for an adiabatic blast wave; three of which are consistent
with the blast wave evolution of a jet, with $F_{\nu} \sim t^{-p}$. This
behavior suggests that, in some cases, the emission may originate from a narrow
jet, possibly consisting of ``nuggets'' whose angular size are less than $1 /
\Gamma$, where $\Gamma$ is the bulk Lorentz factor.


title: Long-Range Correlations in Self-Gravitating N-Body Systems

abstract:
  Observed self-gravitating systems reveal often fragmented non-equilibrium
structures that feature characteristic long-range correlations. However, models
accounting for non-linear structure growth are not always consistent with
observations and a better understanding of self-gravitating $N$-body systems
appears necessary. Because unstable gravitating systems are sensitive to
non-gravitational perturbations we study the effect of different dissipative
factors as well as different small and large scale boundary conditions on
idealized $N$-body systems. We find, in the interval of negative specific heat,
equilibrium properties differing from theoretical predictions made for
gravo-thermal systems, substantiating the importance of microscopic physics and
the lack of consistent theoretical tools to describe self-gravitating gas.
Also, in the interval of negative specific heat, yet outside of equilibrium,
unforced systems fragment and establish transient long-range correlations. The
strength of these correlations depends on the degree of granularity, suggesting
to make the resolution of mass and force coherent. Finally, persistent
correlations appear in model systems subject to an energy flow.


title: [CII] at 158 mic as a star formation tracer in late-type galaxies

abstract:
  We present a calibration of the massive star formation rate vs. [CII]
luminosity relation based on a sample of nearby, late-type galaxies observed
with ISO-LWS and imaged in the Halpha+[NII] line. The relation holds for far-IR
luminosities 10^8 < L_{FIR} < 10^{10.5} L (solar units). The derived star
formation rates have an uncertainty of about a factor of 10. Part of this
uncertainty is due to the different mix of contributions to the [CII] emission
from the different components of the interstellar medium in individual
galaxies, as discussed in an appendix.


title: Detailed Analysis of Nearby Bulgelike Dwarf Stars II. Lithium Abundances

abstract:
  Li abundances are derived for a sample of bulgelike stars with isochronal
ages of 10-11 Gyr. These stars have orbits with pericentric distances, Rp, as
small as 2-3 kpc and Zmax < 1 kpc. The sample comprises G and K dwarf stars in
the metallicity range -0.80<[Fe/H]< +0.40. Few data of Li abundances in old
turn-off stars (> 4.5 Gyr) within the present metallicity range are available.
M67 (4.7 Gyr) and NGC 188 (6 Gyr) are the oldest studied metal-rich open
clusters with late-type stars. Li abundances have also been studied for few
samples of old metal-rich field stars. In the present work a high dispersion in
Li abundances is found for bulgelike stars for all the metallicity range,
comparable with values in M67. The role of metallicity and age on a Li
depletion pattern is discussed. The possible connection between Li depletion
and oxygen abundance due to atmospheric opacity effects is investigated.


title: The accretion flow in the discless intermediate polar V2400 Ophiuchi

abstract:
  RXTE observations confirm that the X-ray lightcurve of V2400 Oph is pulsed at
the beat cycle, as expected in a discless intermediate polar. There are no
X-ray modulations at the orbital or spin cycles, but optical line profiles vary
with all three cycles. We construct a model for line-profile variations in a
discless accretor, based on the idea that the accretion stream flips from one
magnetic pole to the other, and show that this accounts for the observed
behaviour over the spin and beat cycles. The minimal variability over the
orbital cycle implies that 1) V2400 Oph is at an inclination of only ~10 deg,
and 2) much of the accretion flow is not in a coherent stream, but is circling
the white dwarf, possibly as a ring of denser, diamagnetic blobs. We discuss
the light this sheds on disc formation in intermediate polars.


title: On the accretion mode of the intermediate polar V1025 Centauri

abstract:
  The long white-dwarf spin periods in the magnetic cataclysmic variables EX
Hya and V1025 Cen imply that if the systems possess accretion discs then they
cannot be in equilibrium. It has been suggested that instead they are discless
accretors in which the spin-up torques resulting from accretion are balanced by
the ejection of part of the accretion flow back towards the secondary. We
present phase-resolved spectroscopy of V1025 Cen aimed at deducing the nature
of the accretion flow, and compare this with simulations of a discless
accretor. We find that both the conventional disc-fed model and the
discless-accretor model have strengths and weaknesses, and that further work is
needed before we can decide which applies to V1025 Cen.


title: Stream-fed Accretion in Intermediate Polars

abstract:
  I review the observational evidence for stream-fed accretion in intermediate
polars. Recent work on the discless system V2400 Oph confirms the pole-flipping
model of stream-fed accretion, but this applies only to a minority of the flow.
The bulk of the flow is in the form of blobs circling the white dwarf, a state
which might have been a precursor to disc formation in other IPs. I also
discuss work on the systems with anomalously long spin periods, V1025 Cen and
EX Hya. There are arguments both for and against stream-fed accretion in V1025
Cen, and further work is necessary before reaching a conclusion about this
system.