title:
The Stable Planetary Geometry of the Exosystems in 2:1 Mean Motion
  Resonance

abstract:
  (Abridged) We have numerically explored the stable planetary geometry for the
multiple systems involved in a 2:1 mean motion resonance, and herein we mainly
concentrate on the study of the HD 82943 system by employing two sets of the
orbital parameters (Mayor et al. 2004). We find that all stable orbits are
related to the 2:1 commensurability for $10^{7}$ yr, and the apsidal
phase-locking between two orbits can further enhance the stability for this
system. For HD 82943, there exist three possible stable configurations:(1) Type
I, only $\theta_{1} \approx 0^{\circ}$,(2) Type II,
$\theta_{1}\approx\theta_{2}\approx\theta_{3}\approx 0^{\circ}$ (aligned case),
and (3) Type III, $\theta_{1}\approx 180^{\circ}$,
$\theta_{2}\approx0^{\circ}$, $\theta_{3}\approx180^{\circ}$ (antialigned
case), here the lowest eccentricity-type mean motion resonant arguments are
$\theta_{1} = \lambda_{1} - 2\lambda_{2} + \varpi_{1}$ and $\theta_{2} =
\lambda_{1} - 2\lambda_{2} + \varpi_{2}$, the relative apsidal longitudes
$\theta_{3} = \varpi_{1}-\varpi_{2}=\Delta\varpi$. In addition, we also propose
a semi-analytical model to study $e_{i}-\Delta\varpi$ Hamiltonian contours.
With the updated fit, we examine the dependence of the stability of this system
on the orbital parameters. Moreover, we numerically show that the assumed
terrestrial bodies cannot survive near the habitable zones for HD 82943 and
low-mass planets can be dynamically habitable in the GJ 876 system at $\sim 1$
AU in the numerical surveys.


title: The abundance of galactic planets from OGLE-III 2002 microlensing data

abstract:
  From the 389 2002 OGLE-III observations of Galactic Bulge microlensing events
we select 321 that are well described by a point-source point-lens lightcurve
model. From this sample we identify n=1 event, 2002-BLG-055, which we regard as
a strong planetary lensing candidate, and another, 2002-BLG-140, which is a
possible candidate. If each of the 321 lens stars has 1 planet with a mass
ratio q=m/M=10^{-3} and orbit radius a=R_E, the Einstein ring radius, analysis
of detection efficiencies indicates that 14 planets should have been detectable
with \Delta\chi^2 > 25. Assuming our candidate is due to planetary lensing,
then the abundance of planets with q=10^{-3} and a=R_E is n_p \approx n/14 =
7%. Conversion to physical units (M_Jup, and AU) gives the abundance of `cool
Jupiters' (m \approx M_Jup, a \approx 4 AU) per lens star as n_p \approx n/5.5
= 18%. The detection probability scales roughly with q and
(\Delta\chi^2)^{-1/2}, and drops off from a peak at a \approx 4 AU like a
Gaussian with a dispersion of 0.4 dex.


title:
OVI, NV, and CIV in the Galactic Halo: I. Velocity-Dependent Ionization
  Models

abstract:
  We explore theoretical models of the ionization ratios of the Li-like
absorbers NV, OVI, and CIV, in the Galactic halo. These ions are believed to
form in nonequilibrium processes such as shocks, evaporative interfaces, or
rapidly cooling gas, all of which trace the dynamics of the interstellar
medium. As a useful new diagnostic, we focus on velocity-resolved signatures of
several common physical structures: (1) a cooling Galactic fountain flow that
rises, cools, and recombines as it returns to the disk; (2) shocks moving
toward the observer; (3) a conductive interface with the observer located in
the hotter gas. This last geometry occurs with the solar system inside a hot
bubble, or when one looks out through the fragmenting top shell of our local
bubble blown into the halo as part of the Galactic fountain. In Paper II, these
models are compared to ionization-ratio data from FUSE and Hubble Space
Telescope.


title:
OVI, NV and CIV in the Galactic Halo: II. Velocity-Resolved Observations
  with Hubble and FUSE

abstract:
  We present a survey of NV and OVI (and where available CIV) in the Galactic
halo, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the
Hubble Space Telescope (HST) along 34 sightlines. These ions are usually
produced in nonequilibrium processes such as shocks, evaporative interfaces, or
rapidly cooling gas, and thus trace the dynamics of the interstellar medium.
Searching for global trends in integrated and velocity-resolved column density
ratios, we find large variations in most measures, with some evidence for a
systematic trend of higher ionization (lower NV/OVI column density ratio) at
larger positive line-of-sight velocities. The slopes of log[N(NV)/N(OVI)] per
unit velocity range from -0.015 to +0.005, with a mean of
-0.0032+/-0.0022(r)+/-0.0014(sys) dex/(km/s). We compare this dataset with
models of velocity-resolved high-ion signatures of several common physical
structures. The dispersion of the ratios, OVI/NV/CIV, supports the growing
belief that no single model can account for hot halo gas, and in fact some
models predict much stronger trends than are observed. It is important to
understand the signatures of different physical structures to interpret
specific lines of sight and future global surveys.


title:
VLT spectropolarimetry of two powerful radio galaxies at z~1.4: UV
  continuum, emission-line properties and the nature of high-redshift dust

abstract:
  (Abridged) Deep VLT spectropolarimetric observations are presented for two
powerful radio galaxies, 0850-206 and 1303+091. These observations cover the
rest-frame wavelength range ~ 1450 - 3750 A. New radio observations and
continuum images of the same sources are also presented. These galaxies are the
first two observed from a complete sample of nine radio sources with redshifts
in the range 1.3 < z < 1.5 (selected from the equatorial sample of powerful
radio sources of Best, Rottgering & Lehnert), as part of a project aimed to
investigate the multi-component nature of the UV continuum in radio galaxies
and any variations of the continuum properties with the radio source age.
  The larger radio source of the two, 0850-206, presents a high continuum
fractional polarization, averaging 17% across the observed wavelength range and
reaching 24% at rest-frame wavelengths of <2000 A. The smaller radio source,
1303+091, shows a lower continuum polarization, averaging 8% and rising to 11%
for rest-frame wavelengths >3000 A. For both galaxies, the position angle of
the electric vector is generally constant with wavelength and within ~15
degrees of perpendicular to the radio axis. Both their total flux spectra and
polarized flux spectra reveal the 2200 A dust feature, and comparison with dust
scattering models suggests that the composition of the dust in these galaxies
is similar to that of Galactic dust. In 0850-206, scattered quasar radiation
dominates the UV continuum emission, with the nebular continuum accounting for
no more than ~22% and no requirement for any additional emission component such
as emission from young stars. By contrast, in 1303+091, unpolarized radiation
could be a major constituent of the UV continuum emission, with starlight
accounting for up to ~50% and the nebular continuum accounting for ~11%.


title: The SDSS Damped Lya Survey: Data Release 1

abstract:
  We present the results from an automated search for damped Lya (DLA) systems
in the quasar spectra of Data Release 1 from the Sloan Digital Sky Survey
(SDSS-DR1). At z~2.5, this homogeneous dataset has greater statistical
significance than the previous two decades of research. We derive a statistical
sample of 71 damped Lya systems (>50 previously unpublished) at z>2.1 and
measure HI column densities directly from the SDSS spectra. The number of DLA
systems per unit redshift is consistent with previous measurements and we
expect our survey has >95% completeness. We examine the cosmological baryonic
mass density of neutral gas Omega_g inferred from the damped Lya systems from
the SDSS-DR1 survey and a combined sample drawn from the literature. Contrary
to previous results, the Omega_g values do not require a significant correction
from Lyman limit systems at any redshift. We also find that the Omega_g values
for the SDSS-DR1 sample do not decline at high redshift and the combined sample
shows a (statistically insignificant) decrease only at z>4. Future data
releases from SDSS will provide the definitive survey of DLA systems at z~2.5
and will significantly reduce the uncertainty in Omega_g at higher redshift.


title: Theory of Cosmic Microwave Background Polarization

abstract:
  These lectures introduce some of the basic theory of cosmic microwave
background (CMB) polarization with the primary aim of developing the theory of
CMB polarization from inflationary gravitational waves, as well as some of the
related theory of weak gravitational lensing (cosmic shear) of CMB
polarization. We begin with production of polarization by Thomson scattering.
We then discuss tensor-harmonic analysis (the ``grad-curl'' or ``E-B''
decomposition) on a flat and full sky in some detail. The Boltzmann/Einstein
equations required to predict the CMB temperature/polarization pattern due to
primordial gravitational waves are derived. We show that gravitational waves
produce a curl component of the CMB polarization while density perturbations
(at linear order) do not. We then show how cosmic shear induces a curl
component from a curl-free surface of last scattering. We describe, though in
less detail, how higher-order correlations can be used to subtract the
cosmic-shear--induced curl. Several exercises are provided.


title: Shock Compression of Deuterium and the Interiors of Jupiter and Saturn

abstract:
  Recently, deuterium has been the focus of a high level of experimental and
theoretical activity that was sparked by a disagreement on the experimental
value of the maximum compression along the Hugoniot. The behavior of deuterium
at Mbar pressures is not well understood.
  It is of great interest to understand how the current uncertainty on the
hydrogen/deuterium EOS affects the inferred structures of Jupiter and Saturn.
In particular, the mass of a core of heavy elements (other than H and He) and
the total mass of those heavy elements in these two planets are quite sensitive
to the EOS of hydrogen and constitute important clues to their formation
process. We present a study of the range of structures allowed for Jupiter and
Saturn by the current uncertainty in the hydrogen EOS and astrophysical
observations of the two planets. An improved experimental understanding of
hydrogen at Mbar pressures and better determinations of the gravitational
moments of both planets are necessary to put tight bounds on their internal
structure.


title: Millisecond Oscillations During Thermonuclear X-ray Bursts

abstract:
  I review the basic phenomenology and theory of the millisecond brightness
oscillations observed during thermonuclear X-ray bursts from 13 of
approximately 70 accreting neutron stars in low-mass X-ray binaries. Compelling
observations indicate that the oscillations are produced by surface brightness
patterns on the rapidly rotating neutron stars. However, it remains to be
understood (1) why the brightness patterns producing them persist for up to 15
s during an X-ray burst, whereas the burning should cover the entire surface in
less than 1 s, and (2) why the frequencies drift upward by about 5 Hz during
the course of the burst. These peculiarities can probably be explained by
taking into account the expansion of the surface layers caused by the burning,
zonal flows that form due to pressure gradients between the equator and poles,
and Rossby-Alfven modes that are excited in the surface ocean. Further progress
toward understanding how burning progresses on the surface of the neutron star
can be made with a next-generation X-ray timing mission, which would provide a
larger sample of sources with oscillations, detect sideband signals produced by
the spectrum of modes that should be excited in the neutron star ocean, and
measure harmonic structure in the profiles of the oscillations. These
observations would be crucial for measuring the distribution of the rotation
rates of neutron stars, the progression of unstable nuclear burning in the
accreted ocean, and the curvature of the space-time around the neutron star.


title:
Cooler and bigger than thought? Planetary host stellar parameters from
  the InfraRed Flux Method

abstract:
  Effective temperatures and radii for 92 planet-hosting stars as determined
from the InfraRed Flux Method (IRFM) are presented and compared with those
given by other authors using different approaches. The IRFM temperatures we
have derived are systematically lower than those determined from the
spectroscopic condition of excitation equilibrium, the mean difference being as
large as 110 K. They are, however, consistent with previous IRFM studies and
with the colors derived from Kurucz and MARCS model atmospheres. Comparison
with direct measurements of stellar diameters for 7 dwarf stars, which
approximately cover the range of temperatures of the planet-hosting stars,
suggest that the IRFM radii and temperatures are reliable in an absolute scale.
A better understanding of the fundamental properties of the stars with planets
will be achieved once this discrepancy between the IRFM and the spectroscopic
temperature scales is resolved.


title: Jets from Accreting White Dwarfs

abstract:
  Collimated outflows from accreting white dwarfs have an important role to
play in the study of astrophysical jets. Observationally, collimated outflows
are associated with systems in which material is accreted though a disk.
Theoretically, accretion disks provide the foundation for many jet models.
Perhaps the best-understood of all accretion disks are those in cataclysmic
variable stars (CVs). Since the disks in other accreting white-dwarf (WD)
binaries are probably similar to CV disks (at least to the extent that one does
not expect complications such as, for example, advection-dominated flows), with
WD accretors one has the advantage of a relatively good grasp of the region
from which the outflows are likely to originate. We briefly compare the
properties of the three main classes of WD accretors, two of which have members
that produce jets, and review the cases of three specific jet-producing WD
systems.


title:
The Luminosity - E_p Relation within Gamma--Ray Bursts and Implications
  for Fireball Models

abstract:
  Using a sample of 2408 time-resolved spectra for 91 BATSE gamma-ray bursts
(GRBs) presented by Preece et al., we show that the relation between the
isotropic-equivalent luminosity (L_iso) and the spectral peak energy (E_p) in
the cosmological rest frame, L_iso \propto E_p^2, not only holds within these
bursts, but also holds among these GRBs, assuming that the burst rate as a
function of redshift is proportional to the star formation rate. The possible
implications of this relation for the emission models of GRBs are discussed. We
suggest that both the kinetic-energy-dominated internal shock model and the
magnetic-dissipation-dominated external shock model can well interpret this
relation. We constrain the parameters for these two models, and find that they
are in a good agreement with the parameters from the fittings to the afterglow
data (abridged).


title: The inner annular Gap for pulsar radiation: gamma-ray and radio emission

abstract:
  The inner annular gap (IAG), a new type of inner gap whose magnetic field
lines intersect the null charge surface (NCS), is proposed to explain
$\gamma$-ray and radio emission from pulsars. The IAG can be an important
source for high-energy particles. The particles can radiate between the NCS and
the IAG. Some observational characteristics in both $\gamma$-ray and radio
bands, such as the $\gamma$-ray emission beams of Crab-like, Vela-like and
Geminga-like, can be reproduced by numerical method. It is predicted that the
view angle $\zeta$ should be larger than the inclination angle
($\zeta>\alpha$), otherwise the $\gamma$-ray radiation will have little
possibility to be observed. Whether the inner annular gap (or cap) is sparking
(or free flow) depends on the surface binding energy of the pulsar. In stead of
neutron star models, the scenario of the IAG is favorable for bare strange star
models, because bare strange stars can easily satisfy the requisite condition
to form an IAG for both pulsars ($\vec{\Omega}\cdot \vec{B}<0$) and
anti-pulsars ($\vec\Omega \cdot \vec{B}>0$).


title:
The Rates of Hypernovae and Gamma-Ray Bursts: Implications for their
  Progenitors

abstract:
  A critical comparison of estimates for the rates of hypernovae (HNe) and
gamma-ray bursts (GRBs) is presented. Within the substantial uncertainties, the
estimates are shown to be quite comparable and give a Galactic rate of
$10^{-6}$ -- $10^{-5} $yr$^{-1}$ for both events. These rates are several
orders of magnitude lower than the rate of core-collapse supernovae, suggesting
that the evolution leading to a HN/GRB requires special circumstances, very
likely due to binary interactions. Various possible binary channels are
discussed, and it is shown that these are generally compatible with the
inferred rates.


title:
Heterogeneity of solid neutron-star matter: transport coefficients and
  neutrino emissivity

abstract:
  Calculations of weak-interaction transition rates and of nuclear formation
enthalpies show that in isolated neutron stars, the solid phase, above the
neutron-drip threshold, is amorphous and heterogeneous in nuclear charge. The
neutrino emissivities obtained are very dependent on the effects of proton
shell structure but may be several orders of magnitude larger than the electron
bremsstrahlung neutrino-pair emissivity at temperatures of 10^9 K. In this
phase, electrical and thermal conductivities are much smaller than for a
homogeneous bcc lattice. In particular, the reduced electrical conductivity,
which is also temperature-independent, must have significant consequences for
the evolution of high-multipole magnetic fields in neutron stars.


title: The faint X-ray Source Population near 3C 295

abstract:
  We present a statistical analysis of the Chandra observation of the source
field around the 3C 295 galaxy cluster (z=0.46) aimed at the search for
clustering of X-ray sources. We applied three different methods of analysis,
all suggesting a strong clustering in the field on scales of a few arcmin. In
particular 1) the logN-logS computed separately for the four ACIS-I chips
reveals that there is a significant (3.2 sigma in the 0.5-2 keV, 3.3 sigma in
the 2-10 keV and 4.0 sigma in the 0.5-10 keV band) excess of sources to the
North-North East and a void to the South of the central cluster. 2) the two
point, two-dimensional Kolmogorov-Smirnov (KS) test, shows the probability that
the sources are uniformly distributed is only a few percent. 3) a strong
spatial correlation emerges from the study of the angular correlation function
of the field: the angular correlation function (ACF) shows a clear signal on
scales of 0.5 - 5 arcmin, correlation angle in the 0.5-7 keV band theta =
8.5^{+6.5}_{-4.5}, 90% confidence limit (assuming a power law ACF with slope
gamma=1.8). This correlation angle is 2 times higher than that of a sample of 8
ACIS-I field at the 2.5 sigma confidence level. The above scales translate to
0.2 - 2 Mpc at the cluster redshift, higher than the typical cluster core
radius, and more similar to the size of a ``filament'' of the large scale
structure.


title:
Chemical Abundances in the Secondary Star in the Black Hole Binary
  A0620-00

abstract:
  Using a high resolution spectrum of the secondary star in the black hole
binary A0620-00, we have derived the stellar parameters and veiling caused by
the accretion disk in a consistent way. We have used a chi^2 minimization
procedure to explore a grid of 800 000 LTE synthetic spectra computed for a
plausible range of both stellar and veiling parameters. Adopting the best model
parameters found, we have determined atmospheric abundances of Fe, Ca, Ti, Ni
and Al. The Fe abundance of the star is [Fe/H]=0.14 +- 0.20. Except for Ca, we
found the other elements moderately over-abundant as compared with stars in the
solar neighborhood of similar iron content. Taking into account the small
orbital separation, the mass transfer rate and the mass of the convection zone
of the secondary star, a comparison with element yields in supernova explosion
models suggests a possible explosive event with a mass cut comparable to the
current mass of the compact object. We have also analyzed the Li abundance,
which is unusually high for a star of this spectral type and relatively low
mass.


title: Structural parameters of nearby emission-line galaxies

abstract:
  We present the results of an investigation on the main structural properties
derived from VRI and Halpha surface photometry of galaxies hosting nuclear
emission-line regions (including Seyfert 1, Seyfert 2, LINER and starburst
galaxies) as compared with normal galaxies. Our original sample comprises 22
active galaxies, 4 starbursts and 1 normal galaxy and has been extended with
several samples obtained from the literature. Bulge and disc parameters, along
with B/D relation, have been derived applying an iterative procedure. The
resulting parameters have been combined with additional data in order to reach
a statistically significant sample. We find some differences in the bulge
distribution across the different nuclear types that could imply familes of
bulges with different physical properties. Bulge and disc characteristic
colours have been defined and derived for our sample and compared with a
control sample of early type objects. The results suggest that bulge and disc
stellar populations are comparable in normal and active galaxies.


title: Soft X-ray excess emission from clusters of galaxies

abstract:
  This is the first meeting specifically devoted to the topic of cluster soft
excess and related phenomena. It calls together a group of some 40 scientists,
mostly experts in the field, to present their findings on the observational
aspects of emission from clusters, signature of the WHIM in the cluster,
intergalactic, and local environment, theoretical modeling of the WHIM in
cosmological hydrodynamic simulations, theory and observations of cluster
cosmic rays, magnetic fields, radio data and the use of the Sunyaev-Zeldovich
effect as a means of constraining the important parameters. We are particularly
grateful to F.J. Lockman and S.L. Snowden for presenting their latest picture
of the cold gas distribution in the interstellar medium, as this affects our
ability to model extragalactic EUV and soft X-ray data via Galactic absorption
by HI and HeI. Papers given on future hardware concepts to further the spatial
and spectral diagnosis of diffuse soft X-ray emission in general are also
included.


title: Gravitational lensing in the weak field limit by a braneworld black hole

abstract:
  Braneworld black holes existing today may be of primordial origin, or may
even be produced in high energy particle collisions in the laboratory and in
cosmic ray showers as well. These black holes obey a modified mass-radius
relationship compared to standard Schwarzschild black holes. Using the
variational principle we calculate the bending angle of a light ray near the
horizon of a braneworld black hole in the weak field limit. We next derive the
expressions of several lensing quantities like the Einstein radius and the
magnification for a point light source. These expressions are modified compared
to the lensing quantities for standard Schwarzschild black holes and contain
the scale of the extra dimensions.


title:
Relativistic models of two low-luminosity radio jets: B2 0326+39 and B2
  1553+24

abstract:
  We apply the intrinsically symmetrical, decelerating relativistic jet model
developed by Laing & Bridle for 3C 31 to deep, full-synthesis 8.4-GHz VLA
imaging of the two low-luminosity radio galaxies B2 0326+39 and B2 1553+24.
After some modifications to the functional forms used to describe the geometry,
velocity, emissivity and magnetic-field structure, these models can accurately
fit our data in both total intensity and linear polarization. We conclude that
the jets in B2 0326+39 and B2 1553+24 are at angles of 64 +/- 5 deg and 7.7 +/-
1.3 deg to the line of sight, respectively. In both objects, we find that the
jets decelerate from 0.7 - 0.8c to <0.2c over a distance of approximately 10
kpc, although in B2 1553+24 this transition occurs much further from the
nucleus than in B2 0326+39 or 3C 31. The longitudinal emissivity profiles can
be divided into sections, each fit accurately by a power law; the indices of
these power laws decrease with distance from the nucleus. The magnetic fields
in both objects are dominated by the longitudinal component in the
high-velocity regions close to the nucleus and by the toroidal component
further out, but B2 0326+39 also has a significant radial component at large
distances, whereas B2 1553+24 does not. Simple adiabatic models fail to fit the
emissivity variations in the regions of high velocity but provide good
descriptions of the emissivity after the jets have decelerated. Given the small
angle to the line of sight inferred for B2 1553+24, there should be a
significant population of similar sources at less extreme orientations. Such
objects should have long (>200 kpc), straight, faint jets and we show that
their true sizes are likely to have been underestimated in existing images.
(Slightly abridged.)


title: Kinetic theory viscosity

abstract:
  We show how the viscous evolution of Keplerian accretion discs can be
understood in terms of simple kinetic theory. Although standard physics texts
give a simple derivation of momentum transfer in a linear shear flow using
kinetic theory, many authors, as detailed by Hayashi & Matsuda 2001, have had
difficulties applying the same considerations to a circular shear flow. We show
here how this may be done, and note that the essential ingredients are to take
proper account of, first, isotropy locally in the frame of the fluid and,
second, the geometry of the mean flow.


title:
EVN observations of water masers towards the high-mass young stellar
  object in AFGL 5142

abstract:
  We have conducted multi-epoch EVN observations of the 22.2 GHz water masers
towards the high-mass young stellar object in AFGL 5142. With four observing
epochs, spanning a time of ~1 year, 12 distinct maser features have been
detected, 7 out of these detected in more than one epoch. The positions and the
velocities of the VLBI features agree well with those of the emission centers
previously identified by means of VLA observations. For a few features,
persistent over three or four epochs, accurate values of the proper motions are
derived. On the basis of their spatial distribution, the observed maser
features can be divided into two groups. A model fit to the positions and
velocities of the maser features of Group I, detected in the same region
(within ~500 mas) where the massive YSO should be located, demonstrates that
these might arise on the surface of a nearly edge-on Keplerian disk, rotating
around a massive young stellar object. The maser features of Group II, found at
large distances from the YSO (> 1 arcsec), have positions and line-of-sight
velocities in agreement with the blue-shifted lobe of a large scale molecular
outflow (traced by the HCO+ and SiO emission), and might result from the
interaction between the gas flowing away from the young stellar object and the
ambient gas of the progenitor molecular core.


title: Observations of millisecond X-ray pulsars

abstract:
  I present an observational review of the five accretion-driven millisecond
X-ray pulsars currently known, focusing on the results obtained with the Rossi
X-ray Timing Explorer (RXTE) satellite. A prominent place in this review is
given to the first such system discovered, SAX J1808.4-3658. Currently four
outbursts have been detected from this source, three of which have been studied
using RXTE. This makes this source the best studied example of all
accretion-driven millisecond pulsars. Its October 2002 outburst is of
particular interest because of the discovery of kilohertz quasi-periodic
oscillations and burst oscillations during its thermonuclear X-ray bursts. The
other four accreting millisecond pulsars were discovered within the last two
years and only limited results have been published so far. A more extended
review can be found at http://zon.wins.uva.nl/~rudy/admxp/


title:
Probing the RGB-phase transition: Near-IR photometry of six intermediate
  age LMC clusters

abstract:
  This is the first of a series of papers devoted to a global study of the
photometric properties of the red stellar sequences in a complete sample of the
Large Magellanic Cloud clusters, by means of near infrared array photometry.
Deep J,H,Ks photometry and accurate Color Magnitude Diagrams down to K=18.5,
i.e. 1.5 mag below the red He-clump, for six intermediate age clusters (namely
NGC1987, NGC2108, NGC2190, NGC2209, NGC2231, NGC2249) are presented. A
quantitative estimate of the population ratios (by number and luminosity)
between Red Giant Branch and He-clump stars for each target cluster is provided
and discussed in the framework of probing the so-called Red Giant Branch phase
transition (RGB Ph-T). By using the Elson & Fall s-parameter as an age
indicator, the observed RGB population shows a sharp enhancement (both in
number and luminosity) at s=36. Obviously, the corresponding absolute age
strictly depends on the details of theoretical models adopted to calibrate the
s-parameter. Curiously, the currently available calibrations of the s-parameter
in term of age based on canonical (by Elson & Fall 1988) and overshooting
(Girardi et al. 1995) models provide ages that well agree within 10%,
suggesting that the full development of the Red Giant Branch occurs at t=700
Myr and be a relatively fast event (delta t=300 Myr). However, the RGB Ph-T
epoch derived from the overshooting calibration of the s-parameter turns out to
be significantly earlier than the epoch provided by the recent evolutionary
tracks by Girardi et al. (2000). A new calibration of the s-parameter based on
high quality Color Magnitude Diagrams and updated models is urged to address
the origin of this discrepancy and finally establish the epoch of the RGB Ph-T.


title:
Linear Temperature-Mass relation and Local virial relation: Two
  hypotheses for self-gravitating systems

abstract:
  We propose two hypotheses which characterize the quasi-equilibrium state that
realizes after a cold collapse of self-gravitating system. The first hypothesis
is the linear temperature-mass (TM) relation, which yields a characteristic
non-Gaussian velocity distribution. The second is the local virial (LV)
relation, which, combining the linear TM relation, determines a unique mass
density profile as $\rho(r)={\rho}%_{0}r^{-4}e^{-r_0/r}$. Although this density
profile is unphysical in the central region, the region is just inner a few
percent around the center of a bound region in cumulative mass, which is beyond
the resolution of our numerical simulations. Hence posing two hypotheses is
compatible to the numerical simulations for almost the whole region of the
virialized bound state. Actually, except for this inner part, this density
profile fits well to the data of cold collapse simulations. Two families of
spherical and isotropic models, polytropes and King models, are examined from a
view point of these two hypotheses. We found that the LV relation imposes a
strong constraint on these models: only polytropes with index $n \sim 5$ such
as Plummer's model are compatible with the numerical results characterized by
the two hypotheses among these models. King models with the concentration
parameter $% c \sim 2$ violate the LV relation while they are consistent with
the $R^{1/4} $ law for the surface brightness. Hence the above characteristics
can serve as a guideline to build up the models for the bound state after a
cold collapse, besides the conventional criteria concerning the asymptotic
behavior.


title: Imaging the Disk around TW Hya with the Submillimeter Array

abstract:
  We present ~2"-4" aperture synthesis observations of the circumstellar disk
surrounding the nearby young star TW Hya in the CO J=2--1 and J=3--2 lines and
associated dust continuum obtained with the partially completed Submillimeter
Array. The extent and peak flux of the 230 and 345 GHz dust emission follow
closely the predictions of the irradiated accretion disk model of Calvet et al.
(2002). The resolved molecular line emission extends to a radius of at least
200 AU, the full extent of the disk visible in scattered light, and shows a
clear pattern of Keplerian rotation. Comparison of the images with 2D Monte
Carlo models constrains the disk inclination angle to 7+/-1 degrees. The CO
emission is optically thick in both lines, and the kinetic temperature in the
line formation region is ~20K. Substantial CO depletion, by an order of
magnitude or more from canonical dark cloud values, is required to explain the
characteristics of the line emission.


title:
XMM-Newton Spectra of Intermediate-Mass Black Hole Candidates:
  Application of a Monte-Carlo Simulated Model

abstract:
  We present a systematic spectral analysis of six ultraluminous X-ray sources
(NGC1313 X-1/X-2, IC342 X-1, HoIX X-1, NGC5408 X-1 and NGC3628 X-1) observed
with XMM-Newton Observatory. These extra-nuclear X-ray sources in nearby
late-type galaxies have been considered as intermediate-mass black hole
candidates. We have performed Monte-Carlo simulations of Comptonized
multi-color black-body accretion disks. This unified and self-consistent
spectral model assumes a spherically symmetric, thermal corona around each disk
and accounts for the radiation transfer in the Comptonization. We find that the
model provides satisfactory fits to the XMM-Newton spectra of thesources. The
characteristic temperatures of the accretion disks (T_in), for example, are in
the range of ~ 0.05-0.3 keV, consistent with the intermediate-mass black hole
interpretation. We find that the black hole mass is typically about a few times
10^3 M_\odot and has an accretion rate ~ 10^{-6} - 10^{-5} M_\odot yr^{-1}. For
the spectra considered here, we find that the commonly used multi-color
black-body accretion disk model with an additive power law component, though
not physical, provides a good mathematical approximation to the Monte-Carlo
simulated model. However, the latter model provides additional constraints on
the properties of the accretion systems, such as the disk inclination angles
and corona optical depths.


title:
Deep CCD Surface Photometry of Galaxy Clusters II: Searching for
  Intracluster Starlight in non-cD clusters

abstract:
  We report the search for intracluster light in four Abell Type II/III
(non-cD) galaxy clusters: Abell 801, 1234, 1553, & 1914. We find on average
that these clusters contain $\sim$ 10% of their detected stellar luminosity in
a diffuse component. We show that for two of the clusters the intracluster
light closely follows the galaxy distribution, but in the other two cases,
there are noticeable differences between the spatial distribution of the
galaxies and the intracluster light. We report the results of a search for
intracluster tidal debris in each cluster, and note that Abell 1914 in
particular has a number of strong tidal features likely due to its status as a
recent cluster merger. One of the Abell 1914 features appears to be spatially
coincident with an extension seen in weak lensing maps, implying the feature
traces a large amount of mass. We compare these results to numerical
simulations of hierarchically-formed galaxy clusters, and find good general
agreement between the observed and simulated images, although we also find that
our observations sample only the brightest features of the intracluster light.
Together, these results suggest that intracluster light can be a valuable tool
in determining the evolutionary state of galaxy clusters.


title: Puzzling wind properties of young massive stars in SMC-N81

abstract:
  We present a quantitative study of the stellar and wind properties of massive
stars in the compact star forming region SMC-N81. Non-LTE spherically extended
atmosphere models including line-blanketing have been computed with the code
CMFGEN (Hillier & Miller 1998) and the analysis of UV STIS spectra lead to the
following results: 1) The SMC-N81 components are young (~ 0-4 Myrs) O stars
with Teff compatible with medium to late subtypes and with luminosities lower
than average Galactic O dwarfs, rendering them possible ZAMS candidates; 2) The
winds are extremely weak: the mass loss rates (~1e-8/1e-9 Msol/yr) and the
modified wind momenta are 1 to 2 orders of magnitude lower than observed so far
for Galactic stars, and are lower than the predictions of the most recent
hydrodynamical models. The reasons for such weak winds are investigated with
special emphasis on the modified wind momenta: 1) There may be a break-down of
the wind momentum - luminosity relation (WLR) for dwarf stars at low luminosity
(log L/Lsol < 5.5). However, reasons for such a breakdown remain unknown; 2)
The slope of the WLR may be steeper at low metallicity. This is predicted by
the radiation driven wind theory, but the current hydrodynamical simulations do
not show any change of the slope at SMC metallicity. Moreover, there are
indications that some Galactic objects have wind momenta similar to those of
the SMC stars; 3) Decoupling in the atmosphere may lead to multicomponent
winds, but various tests indicate that this is not likely to be the case for
the SMC-N81 stars. Hence, the origin of the weakness of the wind observed in
these objects remains unknown. We suggest that this weakness may be linked with
the youth of these stars and represents possibly the onset of stellar winds in
recently formed massive stars.


title:
The Hanle Effect as a Diagnostic of Magnetic Fields in Stellar Envelopes
  IV. Application to Polarized P Cygni Wind Lines

abstract:
  The Hanle effect has been proposed as a new diagnostic of circumstellar
magnetic fields for early-type stars, for which it is sensitive to field
strengths in the 1-300 G range. In this paper we compute the polarized P-Cygni
line profiles that result from the Hanle effect. For modeling the polarization,
we employ a variant of the ``last scattering approximation''. For cases in
which the Sobolev optical depths are greater than unity, the emergent line
intensity is assumed to be unpolarized; while for smaller optical depths, the
Stokes source functions for the Hanle effect with optically thin line
scattering are used. For a typical P Cygni line, the polarized emission forms
in the outer wind, because the Sobolev optical depth is large at the inner
wind. For low surface field strengths, weak P Cygni lines are needed to measure
the circumstellar field. For high values of the surface fields, both the Zeeman
and Hanle diagnostics can be used, with the Zeeman effect probing the
photospheric magnetic fields, and the Hanle effect measuring the magnetic field
in the wind flow. Polarized line profiles are calculated for a self-consistent
structure of the flow and the magnetic geometry based on the WCFields model,
which is applicable to slowly rotating stellar winds with magnetic fields drawn
out by the gas flow. For surface fields of a few hundred Gauss, we find that
the Hanle effect can produce line polarizations in the range of a few tenths of
a percent up to about 2 percent.


title: MeV-mass dark matter and primordial nucleosynthesis

abstract:
  The annihilation of new dark matter candidates with masses $m_X$ in the MeV
range may account for the galactic positrons that are required to explain the
511 keV $\gamma$-ray flux from the galactic bulge. We study the impact of
MeV-mass thermal relic particles on the primordial synthesis of $^2$H, $^4$He,
and $^7$Li. If the new particles are in thermal equilibrium with neutrinos
during the nucleosynthesis epoch they increase the helium mass fraction for
$m_X\alt 10$ MeV and are thus disfavored. If they couple primarily to the
electromagnetic plasma they can have the opposite effect of lowering both
helium and deuterium. For $m_X=4$--10 MeV they can even improve the overall
agreement between the predicted and observed $^2$H and $^4$He abundances.


title:
Submillimeter Array Observations of CS J=14--13 Emission from the
  Evolved Star IRC+10216

abstract:
  We present imaging observations of the evolved star IRC+10216 in the CS
J=14--13 line at 685.4 GHz and associated submillimeter continuum at about 2''
resolution made with the partially constructed Submillimeter Array. The CS
J=14--13 line emission from the stellar envelope is well resolved both
spatially and spectrally. The strong central concentration of the line emission
provides direct evidence that CS is a parent molecule that forms close to the
stellar photosphere, in accord with previous images of the lower excitation CS
J=2--1 line and inferences from unresolved observations of vibrationally
excited transitions. The continuum emission is dominated by a compact,
unresolved component, consistent with the photospheric emission, that accounts
for about 20% of the broadband 450 micron flux. These are the first
interferometer imaging observations made in the semi-transparent 450 micron
atmospheric window.


title:
Implications of the Lyman alpha Emission Line from a Candidate z=10
  Galaxy

abstract:
  The recently discovered z=10 galaxy (Pello et al 2004) has a strong Lyman
alpha emission line that is consistent with being surprisingly symmetric, even
given the relatively poor quality of its spectrum. The blue wing of a Lyman
alpha line originating at high redshift should be strongly suppressed by
resonant hydrogen absorption along the line of sight, an expectation borne out
by the observed asymmetric shapes of the existing sample of Lyman alpha
emitting sources at lower redshifts (3< z < 6.7). Absorption on the blue side
of the line of the Pello et al. source could be reduced if the intergalactic
medium (IGM) in the vicinity of the galaxy is highly ionized, but we show that
this requires an unrealistically high ionizing emissivity. We suggest instead
that the Lyman alpha emitting gas be receding relative to the surrounding gas
with a velocity of >= 35km/s, a large velocity that is plausible only if the
galaxy is part of a larger system (group of galaxies) with a velocity
dispersion >= 35km/s. We find that with this velocity shift, the observed
strength and shape of the line is still consistent with the galaxy being
surrounded by its own Stromgren sphere embedded in a fully neutral IGM. More
generally, we predict that at any given redshift, the bright Lyman alpha
emitters with broader lines would exhibit stronger asymmetry than fainter ones.
Bright galaxies with symmetric Lyman alpha lines may be signposts for groups
and clusters of galaxies, within which they can acquire random velocities
comparable to or larger than their linewidths.


title:
Interpreting the Colour-Magnitude Diagrams of Open Star Clusters through
  Numerical Simulations

abstract:
  We present detailed comparisons between high quality observational
colour-magnitude diagrams (CMDs) of open star clusters and synthetic CMDs based
on MonteCarlo numerical simulations. The comparisons account for all of the
main parameters which determine the shape of the CMD for a stellar population.
For the four clusters studied, NGC 6819, NGC 2099 (M37), NGC 2168 (M35) and NGC
2323 (M50), we derive reddening, distance, age, binary fraction, star formation
rate and indicative metallicity by comparing the locations and density of
points in the observed CMDs to the simulated CMDs. We estimate the
uncertainties related to stellar evolution theories by adopting various sets of
stellar models for all of the synthetic CMDs and discuss which stellar models
provide the theoretical CMDs that best reproduce the observations.


title: The Case for a Misaligned Relativistic Jet from SN 2001em

abstract:
  SN 2001em, identified as a Type Ic supernova, has recently been detected in
the radio and X-rays, $\gtrsim$ 2 yr after the explosion. The high luminosities
at such late times might arise from a relativistic jet viewed substantially
off-axis that becomes visible only when it turns mildly relativistic and its
emission is no longer strongly beamed away from us. Alternatively, the emission
might originate from the interaction of the SN shell with the circumstellar
medium. We find that the latter scenario is hard to reconcile with the observed
rapid rise in the radio flux and optically thin spectrum,
$F_\nu\propto\nu^{-0.36\pm 0.16}t^{1.9\pm 0.4}$, while these features arise
naturally from a misaligned relativistic jet. The high X-ray luminosity
provides an independent and more robust constraint -- it requires $\sim
10^{51}$ erg in mildly relativistic ejecta. The source should therefore
currently have a large angular size ($\sim$ 2 mas) which could be resolved in
the radio with VLBA. It is also expected to be bipolar and is thus likely to
exhibit a large degree of linear polarization ($\sim 10%-20%$). The presence of
a relativistic outflow in SN 2001em would have interesting implications. It
would suggest that several percent of SNe Ib/c produce mildly relativistic
jets, with an initial Lorentz factor $\Gamma_0\gtrsim 2$, while the fraction
that produce GRB jets (with $\Gamma_0\gtrsim 100$) is $\sim 100$ times smaller.
This could considerably increase the expected number of transients similar to
orphan GRB afterglows in the radio, and to a lesser extent in the optical and
X-rays, if there is a continuous distribution in $\Gamma_0$. Furthermore, this
may give further credence to the idea that core collapse SNe, and in particular
SNe Type Ib/c, are triggered by bipolar jets.


title: TeV Gamma-Ray Observations of the Galactic Center

abstract:
  We report a possible detection of TeV gamma-rays from the Galactic Center by
the Whipple 10m gamma-ray telescope. Twenty-six hours of data were taken over
an extended period from 1995 through 2003 resulting in a total significance of
3.7 standard deviations. The measured excess corresponds to an integral flux of
\Flux above an energy of $2.8 \mathrm{TeV}$, roughly 40% of the flux from the
Crab Nebula at this energy. The 95% confidence region has an angular extent of
about 15 arcmin and includes the position of Sgr A*. The detection is
consistent with a point source and shows no evidence for variability.


title:
Evolution and Color-Dependence of the Galaxy Angular Correlation
  Function: 350,000 Galaxies in 5 Square Degrees

abstract:
  When applied to deep photometric catalogs, the two-point angular correlation
function, w(theta), is a sensitive probe of the evolution of galaxy clustering
properties. Here we present measurements of w(theta) as a function of I_AB
magnitude and (R-I) color to a depth of I_AB=24, using a sample of ~350,000
galaxies covering 5 degrees^2 in total over 5 separate fields. Using redshifts
of 3319 galaxies in early DEEP2 Galaxy Redshift Survey data, we construct
robust galaxy redshift distributions as a function of I_AB and R_AB magnitude
and (R-I) color for galaxies between 0<z<2. We constrain models of the redshift
evolution of galaxy clustering and find that significant growth of clustering
has occurred from z>1 to z=0. A model in which the comoving scale-length, x_0,
evolves linearly with redshift, x_0(z)=x_0(0)(1-Bz), fits the data better than
the 'epsilon' model proposed by Groth and Peebles (1977). The clustering
properties depend strongly on observed (R-I) color, with both the reddest and
bluest galaxies exhibiting large clustering amplitudes and steeper slopes.
Different observed (R-I) color ranges are sensitive to very disparate redshift
regimes. Red galaxies with (R-I)~1.5 lie in a narrow redshift range centered at
z~0.85 and have a comoving scale length of clustering at z=0.85 of x_0=5.0
+/-0.3 Mpc/h. These galaxies have early-type spectra and are likely progenitors
of massive local ellipticals. The bluest galaxies with (R-I)~0 appear to be a
mix of star-forming galaxies, both relatively local (z~0.3-0.6) dwarfs and
bright z>1.4 galaxies, and broad-line AGN. We find that local blue dwarfs are
relatively unclustered, with x_0=1.6 +/-0.2 Mpc/h. The z>1.4 blue galaxies have
a larger clustering scale-length, x_0>5 Mpc/h.


title: The Variability of Gamma-Ray Bursts that Create Afterglows

abstract:
  We consider whether the variability properties of Gamma-Ray Bursts (GRBs)
that produce bright optical and longer wavelength transient afterglows (A-GRBs)
are the same as a larger, inclusive sample of bright, long-duration GRBs,
selected only by their gamma-ray emission. This sample may include a
significant population of physically distinct ``dark'' or ``faint-afterglow''
GRBs with different variability properties, or may be composed of a single
population, some of which lack afterglows only because of observational
selection effects. We argue that the structure function is the most appropriate
method for measuring the variability of bursts because of their transient and
aperiodic nature. We define a simple statistic: the ratio of the integrated
structure function from 0.1 to 1 s compared to that from 0.1 to 10 s, as
measured in the observer frame. To avoid instrumental effects we restrict our
analysis to GRBs with BATSE data. Comparing 10 A-GRBs to a ``main'' sample of
about 500 bursts, we find there is a probability of only 0.03 of the samples
being drawn from the same population, with the A-GRBs tending to have
relatively less power on sub-second timescales. We conclude that this result is
tentative evidence for variations in the properties of GRB progenitors that
affect both the gamma-ray and afterglow properties of long-duration GRBs. In
addition, our method of analyzing variability identifies a characteristic
timescale of ~1 s, below which variability is suppressed, and finds a trend of
increased short timescale variability at higher gamma-ray energies. The
long-duration GRBs that we identify as having the most sub-second timescale
variability, may be relatively bright examples of short-duration GRBs.


title:
Orbital capture of stars by a massive black hole via exchanges with
  compact remnants

abstract:
  We propose a dynamical mechanism for capturing stars around a massive black
hole (MBH), which is based on the accumulation there of a very dense cluster of
compact stellar remnants. This study is motivated by the presence of ~10 young
massive stars (M*~3-15 Mo, ~B9V--O8V) less than 0.04 pc from the MBH in the
Galactic center (GC). Their existence in the extreme environment so close to a
MBH is a challenge for theories of star formation and stellar dynamics. We show
that young stars, which formed far from the MBH and were then scattered into
eccentric orbits, repeatedly cross a cluster of stellar black holes (SBHs),
where they may undergo rare direct 3-body exchanges with a MBH-SBH "binary".
The interaction between two objects of similar mass ejects the SBH and captures
the star on a tight orbit around the MBH. Such captures can naturally explain
trends observed in the orbits of the young stars. We derive the capture
cross-section, validate it by Monte-Carlo simulations, and calculate the number
of captured stars in the GC using the currently uncertain estimates of the
numbers of SBHs inside 0.04 pc and of young stars in the inner few pc of the
GC. We find that under favorable conditions 3-body exchange can account for
\~25% of the observed stars, mostly at the fainter end of the observed range.
We discuss additional effects that possibly increase the capture efficiency.
Future observations will establish whether there are enough SBHs and young
stars for exchange captures to singly account for the central young stars. We
estimate that there are also ~35 lower mass stars (M*~1-3 Mo, ~G2V--A0V) inside
0.04 pc similarly captured by exchanges with neutron stars. Ongoing replacement
of compact remnants by main sequence stars may regulate the accumulation of
compact remnants near the MBH.


title: Resonant Scattering and Recombination in CAL 87

abstract:
  The eclipsing supersoft X-ray binary CAL 87 has been observed with Chandra on
August 13/14, 2001 for nearly 100 ksec, covering two full orbital cycles and
three eclipses. The shape of the eclipse light curve derived from the
zeroth-order photons indicates that the size of the X-ray emission region is
about 1.5 solar radii. The ACIS/LETG spectrum is completely dominated by
emission lines without any noticeable continuum. The brightest emission lines
are significantly redshifted and double-peaked, suggestive of emanating in a
2000 km/s wind. We model the X-ray spectrum by a mixture of recombination and
resonant scattering. This allows us to deduce the temperature and luminosity of
the ionizing source to be kT = 50-100 eV and L_X = 5E37 erg/s.


title: Bremsstrahlung photons from the bare surface of a strange quark star

abstract:
  The photon emissivity from the bremsstrahlung process ee-> ee\gamma occuring
in the electrosphere at the bare surface of a strange quark star is calculated.
For surface temperatures T<10^9K, the photon flux exceeds that of e+e- pairs
that are produced via the Schwinger mechanism in the presence of a strong
electric field that binds electrons to the surface of the quark star. The
average energy of photons emitted from the bremsstrahlung process can be 0.5
MeV or more, which is larger than that in e+e- pair annihilation. The
observation of this distinctive photon spectrum would constitute an
unmistakable signature of a strange quark star and shed light on color
superconductivity at stellar densities.


title:
Polarization of pulsar radiation in the two-pole caustic model and in
  the outer gap model

abstract:
  We present linear polarization characteristics of pulsar radiation as
predicted by two models of high-energy radiation from extended regions in the
outer magnetosphere: the recently proposed two-pole caustic model, and the
outer gap model.


title: High Density Molecular Gas in the IR-bright Galaxy System VV114

abstract:
  New high resolution CO(3-2) interferometric map of the IR-bright interacting
galaxy system VV114 observed with the Submillimeter Array (SMA) reveal a
substantial amount of warm and dense gas in the IR-bright but optically
obscured galaxy, VV114E, and the overlap region connecting the two nuclei. A
1.8 x 1.4 kpc concentration of CO(3-2) emitting gas with a total mass of 4 x
10^9 Msun coincides with the peaks of NIR, MIR, and radio continuum emission
found previously by others, identifying the dense fuel for the AGN and/or the
starburst activity there. Extensive CO(2-1) emission is also detected,
revealing detailed distribution and kinematics that are consistent with the
earlier CO(1-0) results. The widely distributed molecular gas traced in CO(2-1)
and the distributed discrete peaks of CO(3-2) emission suggest that a spatially
extended intense starbursts may contribute significantly to its large IR
luminosity. These new observations further support the notion that VV114 is
approaching its final stage of merger, when violent central inflow of gas
triggers intense starburst activity possibly boosting the IR luminosity above
the ultraluminous threshold.


title: High resolution observations of 6.7-GHz methanol masers with the LBA

abstract:
  We have used the Australian Long Baseline Array (LBA) to produce
milliarcsecond images of five sites of methanol maser emission at 6.7 GHz.
These are all sites that have linear morphologies at arcsecond resolutions,
which have been hypothesised to be due to the masers forming in edge-on
circumstellar disks. We find that a simple disk model cannot explain the
observations. We discuss various alternatives, and suggest a new model which
explains how linear velocity gradients can be produced in methanol masers that
arise in planar shocks propagating nearly perpendicular to the line of sight.


title:
Automated Clustering Algorithms for Classification of Astronomical
  Objects

abstract:
  Data mining is an important and challenging problem for the efficient
analysis of large astronomical databases and will become even more important
with the development of the Global Virtual Observatory. In this study, learning
vector quantization (LVQ), single-layer perceptron (SLP) and support vector
machines (SVM) were put forward for multi-wavelength data classification. A
feature selection technique was used to evaluate the significance of the
considered features to the results of classification. From the results, we
conclude that in the situation of less features, LVQ and SLP show better
performance. In contrast, SVM shows better performance when considering more
features. The focus of the automatic classification is on the development of
efficient feature-based classifier. The classifiers trained by these methods
can be used for preselecting AGN candidates.


title: The VSOP 5 GHz Continuum Survey, recent results

abstract:
  In February 1997 the Japanese radio astronomy satellite Halca was launched to
provide the space-bourne element for the VSOP mission. Approximately
twenty-five percent of the mission time has been dedicated to the VSOP Survey,
a 5 GHz survey of bright, compact AGN. Both the final, calibrated, high
resolution images and plots of visibility amplitude versus uv distance for the
first 102 of the sources have been prepared and has been submitted. Papers on
the methods and the models from fitting the cumulative {\em uv} amplitudes will
also be submitted. The analysis of the second half is well underway.


title: The VSOP 2 mission: Imaging capabilities

abstract:
  Given the scientific goals of VSOP-2, including the possibility of
observations of the shadows of black holes, we have investigated the fidelity
of the recovered images given a typical uv-coverage. We find that we can
achieve a dynamic range of better than 1000:1.


title: Hydrodynamic modelling of accretion flows

abstract:
  In the proceedings of this, and of several recent close binary conferences,
there have been several contributions describing smoothed particle
hydrodynamics simulations of accretion disks. It is apposite therefore to
review the numerical scheme itself with emphasis on its advantages for disk
modelling, and the methods used for modelling viscous processes.


title:
High speed photometry of faint Cataclysmic Variables: IV. V356 Aql,
  Aqr1, FIRST J1023+0038, Ha 0242-2802, GI Mon, AO Oct, V972 Oph, SDSS 0155+00,
  SDSS 0233+00, SDSS 1240-01, SDSS 1556-00, SDSS 2050-05, FH Ser

abstract:
  We present results from high speed photometry of a further thirteen faint
cataclysmic variables. V356 Aql (Nova Aql 1936) shows flare-like outbursts with
recurrence time scales ~ 3000 s, but no coherent periodicities. Aqr1 is an
intermediate polar with a spin period of 6.7284 min and a probable orbital
period P(orb) = 3.226 h derived from orbital sidebands. Its orbital sideband
frequencies show very variable amplitudes. The published spectroscopic period
of 2.0 h suggests that Aqr1 is similar to GW Lib and FS Aur in having an
additional periodicity of unknown origin. FIRST J1023+0038 has P(orb) = 4.7548
h with an orbital modulation of range 0.45 mag, probably caused by reflection
effect from a hot white dwarf primary; as such it may have been a nova sometime
in the past few decades. Ha 0242 is a deeply eclipsing very low mass-transfer
rate system, probably a dwarf nova of very long outburst interval, with P(orb)
= 1.792 h. GI Mon, an old nova, has optical modulations at 4.325 h and possibly
also at 48.6 min and is thus a candidate intermediate polar. AO Oct, an SU UMa
type dwarf nova, shows orbital modulation at quiescence with P(orb) = 94.097
min. V972 Oph (Nova Ophiuchi 1957) showed no flickering activity during one set
of observations, but did so at a later time, confirming the correctness of the
identification of this object, but it shows no orbital modulation. SDSS 0155 is
a deeply eclipsing polar with an orbital period of 87.13 min. SDSS 0233 shows
flaring activity but no discernible periodicity. No periodicity was found in
the new AM CVn candidate SDSS 1240. SDSS 1556 shows a periodic modulation at
1.778 h which is possibly due to orbital motion. SDSS 2050 is an eclipsing
polar with P(orb) = 1.5702 h. FH Ser (Nova Serpentis 1970) has strong
flickering activity but no detectable orbital modulation.


title: SN1987A and the properties of neutrino burst

abstract:
  We reanalyze the neutrino events from SN1987A in IMB and Kamiokande-II (KII)
detectors, and compare them with the expectations from simple theoretical
models of the neutrino emission. In both detectors the angular distributions
are peaked in the forward direction, and the average cosines are 2 sigma above
the expected values. Furthermore, the average energy in KII is low if compared
with the expectations; but, as we show, the assumption that a few (probably
one) events at KII have been caused by elastic scattering is not in contrast
with the 'standard' picture of the collapse and yields a more satisfactory
distributions in angle and (marginally) in energy. The observations give useful
information on the astrophysical parameters of the collapse: in our
evaluations, the mean energy of electron antineutrinos is <E> =12-16 MeV, the
total energy radiated around (2-3)*1.E53 erg, and there is a hint for a
relatively large radiation of non-electronic neutrino species. These properties
of the neutrino burst are not in disagreement with those suggested by the
current theoretical paradigm, but the data leave wide space to non-standard
pictures, especially when neutrino oscillations are included.


title: Measurement of the proper motion of Vela with the LBA

abstract:
  The first accurate measurements of Vela's proper motion were produced using
the Parkes-Tidbinbilla Interferometer (PTI) (Bailes et al 1989). This 275 km
baseline at 1.6 GHz gave a resolution of 140 mas and detected the proper motion
and thus, by extrapolation, the birth site. We have extended this work to allow
the third dimension to be derived via the parallax. We find the offset between
the spin axis and the proper motion vector to be $9^o$, which limits
acceleration time from the SN blast.


title: The Vela pulsar, the key?

abstract:
  Of all pulsars known Vela has been one of the most productive in terms in
understanding pulsars and their characteristics. We present the latest results
derived from Australian telescopes. These include a more accurate pulsar
distance, a more precise pulsar local space velocity, a new model of the spin
up and the association of a radio nebula with the X-ray pulsar wind nebula.


title: Warm high velocity CO in the wind of Sakurai's Object (= V4334 Sgr)

abstract:
  We present UKIRT UIST spectra of Sakurai's Object (=V4334 Sgr) showing CO
fundamental band absorption features around 4.7 microns. The line-centres are
at heliocentric radial velocity of -170+/-30 km/s. The number and relative
strengths of the lines indicate a CO gas temperature of 400+/-100 K and CO
column density of 7(+3/-2)x10^17 per square cm. The gas was moving away from
the central star at an average speed of 290+/-30 km/s in 2003 September. The
lines appeared sometime between mid 1999 (well after the opaque dust shell
formed) and mid 2000 and may have been somewhat more blue--shifted initially
than they are now. The observed CO velocity and temperature indicate the
continued presence of a fast wind in the object, previously seen in the He I
1.083 micron line beginning just prior to massive dust formation, and more
recently in atomic and ionized lines. The dust continuum is consistent with a
temperature of 350+/-30 K, indicating continued cooling of the shell. The
similar CO temperature suggests that the bulk of the CO absorption occurs just
outside of the dust continuum surface.


title: Stability of cold fronts in clusters: is magnetic field necessary?

abstract:
  Cold fronts - sharp discontinuities recently discovered by Chandra in many
clusters of galaxies - are believed to be due to a hot gas flow over a colder
gravitationally bound gas cloud. We analyze the stability of the fronts with
respect to Kelvin-Helmholtz instability and show that an intrinsic width of the
interface of the order of a few per cent of the curvature radius strongly
limits the growth of perturbation. For the best studied case of a front in the
Cluster Abell 3667 we conclude that current observational data on the width and
extent of the front can be explained even in the absence of dynamically
important magnetic fields.


title: Temperature distribution in magnetized neutron star crusts

abstract:
  We investigate the influence of different magnetic field configurations on
the temperature distribution in neutron star crusts. We consider axisymmetric
dipolar fields which are either restricted to the stellar crust, ``crustal
fields'', or allowed to penetrate the core, ``core fields''. By integrating the
two-dimensional heat transport equation in the crust, taking into account the
classical (Larmor) anisotropy of the heat conductivity, we obtain the crustal
temperature distribution, assuming an isothermal core. Including quantum
magnetic field effects in the envelope as a boundary condition, we deduce the
corresponding surface temperature distributions. We find that core fields
result in practically isothermal crusts unless the surface field strength is
well above $10^{15}$ G while for crustal fields with surface strength above a
few times $10^{12}$ G significant deviations from isothermality occur at core
temperatures inferior or equal to $10^8$ K. At the stellar surface, the cold
equatorial region produced by the quantum suppression of heat transport
perpendicular to the field in the envelope, present for both core and crustal
fields, is significantly extended by the classical suppression at higher
densities in the case of crustal fields. This can result, for crustal fields,
in two small warm polar regions which will have observational consequences: the
neutron star has a small effective thermally emitting area and the X-ray pulse
profiles are expected to have a distinctively different shape compared to the
case of a neutron star with a core field. These features, when compared with
X-ray data on thermal emission of young cooling neutron stars, will open a way
to provide observational evidence in favor, or against, the two radically
different configurations of crustal or core magnetic fields.


title:
Modelling the variability of the Fe K alpha line in accreting black
  holes

abstract:
  The variability of the Fe K alpha line near 6.5 keV seems to be reduced
compared to the variability of the hard X-rays which presumably drive the line
emission. This is observed both in active galactic nuclei and galactic black
hole binaries. We point out that such reduced variability, as well as lack of
coherence between the variations of the line and the continuum, are a natural
prediction of a propagation model of variability in the geometry of inner hot
accretion flow. We compute detail model predictions of the variability
characteristics which could be compared with current and future data. We also
point out that the model requires a gradual disappearance of the cold disc,
rather than a sharp transition from the cold disc to a hot flow.


title: A dipping black-hole X-ray binary candidate in NGC 55

abstract:
  XMM-Newton EPIC observations have revealed a bright point-like X-ray source
in the nearby Magellanic-type galaxy NGC 55. At the distance of NGC 55, the
maximum observed X-ray luminosity of the source, designated as XMMU
J001528.9-391319, is L(x) ~ 1.6 x 10^{39} erg/s, placing the object in the
ultraluminous X-ray source (ULX) regime. The X-ray lightcurve exhibits a
variety of features including a significant upward drift over the 60 ks
observation. Most notably a series of X-ray dips are apparent with individual
dips lasting for typically 100-300 s. Some of these dips reach almost 100
percent diminution of the source flux in the 2.0-4.5 keV band. The EPIC CCD
spectra can be modelled with two spectral components, a very soft powerlaw
continuum (Gamma ~ 4) dominant below 2 keV, plus a multi-colour disc (MCD)
component with an inner-disc temperature kT ~ 0.8 keV. The observed upperward
drift in the X-ray flux can be attributed to an increase in the level of the
MCD component, whilst the normalisation of the powerlaw continuum remains
unchanged. The dipping episodes correspond to a loss of signal from both
spectral components, although the blocking factor is at least a factor two
higher for the MCD component. XMMU J001528.9-391319 can be considered as a
candidate black-hole binary (BHB) system. A plausible explanation of the
observed temporal and spectral behaviour is that we view the accretion disc
close to edge-on and that, during dips, orbiting clumps of obscuring material
enter our line of sight and cause significant blocking or scattering of the
hard thermal X-rays emitted from the inner disc. In contrast, the more extended
source of the soft powerlaw flux is only partially covered by the obscuring
matter during the dips.


title:
The distance to the Pleiades from orbital solution of the double-lined
  eclipsing binary HD 23642

abstract:
  Combining precise B,V photoelectric photometry and radial velocities, we have
been able to derive a firm orbital solution and accurate physical parameters
for the newly discovered eclipsing binary HD 23642 in the Pleiades open
cluster. The resulting distance to the binary, and therefore to the cluster, is
132 +/- 2 pc. This closely confirms the distance modulus obtained by classical
main sequence fitting methods (m-M = 5.60 or 132 pc), moving cluster techniques
and the astrometric orbit of Atlas. This is the first time the distance to a
member of the Pleiades is derived by orbital solution of a double-lined
eclipsing binary, and it is intended to contribute to the ongoing discussion
about the discordant Hipparcos distance to the cluster.


title: Cosmological Black Holes as Seeds of Voids in Galaxy Distribution

abstract:
  Deep surveys indicate a bubbly structure of cosmological large scale which
should be the result of evolution of primordial density perturbations. Several
models have been proposed to explain origin and dynamics of such features but,
till now, no exhaustive and fully consistent theory has been found. We discuss
a model where cosmological black holes, deriving from primordial perturbations,
are the seeds for large-scale-structure voids. We give details of dynamics and
accretion of the system voids-cosmological black holes from the epochs
$(z\simeq10^{3})$ till now finding that void of $40h^{-1}Mpc$ of diameter and
under-density of -0.9 will fits the observations without conflicting with the
homogeneity and isotropy of cosmic microwave background radiation.


title: An outline of Weyl geometric models in cosmology

abstract:
  Already the simplest examples of Weyl geometry, the static space-time models
of general relativity modified by an additional time-homogeneous Weylian length
connection lead to beautiful cosmological models (Weyl universes) . The
magnitude-redshift relation of recent supernovae Ia measurements is in perfect
agreement with the prediction of decrease of energy flux in the Weyl models.
These data allow to estimate the (ex-ante) spacelike curvature of Weyl
universes. Quasar frequency data from the SDSS provide strong evidence of a
positive ex-ante curvature. Thus an Einstein-Weyl universe, i.e., an Einstein
universe endowed with a Weylian length connection, is in good agreement with
supernovae and quasar data.
  The relative mass-energy density with respect to the critical density of the
standard approach, and the relative contribution of the ``vacuum term'' are
time-independent in Weyl gauge. Thus the time-evolution anomaly of vacuum
energy does not arise. The intervals given in the literature for the
dynamically determined matter density parameter are consistent with other data
in the Weyl geometric approach. An explanation of the cosmic microwave
background by a maximal entropy state of the quantized Maxwell equation,
according to a proposal by I.E. Segal for the conformal Einstein universe,
translates directly to the Weyl approach. It leads to quantitative estimations
for the temperature of the Planck radiation between 2 and 5.3 deg K. Moreover,
the anisotropy angles, expected to arise in an Einstein-Weyl universe agrees
with the results of multipole measurements of CMB anisotropies.


title:
Classical novae from the POINT-AGAPE microlensing survey of M31 -- I.
  The nova catalogue

abstract:
  The POINT-AGAPE survey is an optical search for gravitational microlensing
events towards the Andromeda Galaxy (M31). As well as microlensing, the survey
is sensitive to many different classes of variable stars and transients. Here
we describe the automated detection and selection pipeline used to identify M31
classical novae (CNe) and we present the resulting catalogue of 20 CN
candidates observed over three seasons. CNe are observed both in the bulge
region as well as over a wide area of the M31 disk. Nine of the CNe are caught
during the final rise phase and all are well sampled in at least two colours.
The excellent light-curve coverage has allowed us to detect and classify CNe
over a wide range of speed class, from very fast to very slow. Among the
light-curves is a moderately fast CN exhibiting entry into a deep transition
minimum, followed by its final decline. We have also observed in detail a very
slow CN which faded by only 0.01 mag day$^{-1}$ over a 150 day period. We
detect other interesting variable objects, including one of the longest period
and most luminous Mira variables. The CN catalogue constitutes a uniquely
well-sampled and objectively-selected data set with which to study the
statistical properties of classical novae in M31, such as the global nova rate,
the reliability of novae as standard-candle distance indicators and the
dependence of the nova population on stellar environment. The findings of this
statistical study will be reported in a follow-up paper.


title:
Evidence of Planetesimal infall on to the very young Herbig Be star
  LkH$_\alpha$234

abstract:
  We report here the first evidence for planetesimal infall onto the very young
Herbig Be star LkH$_\alpha$234. These results are based on observations
acquired over 31 days using spectroscopy of the sodium D lines, the He I
5876\AA, and hydrogen H$_\alpha$ lines. We find Redshifted Absorption
Components (RAC) with velocities up to 200 km/s and very mild Blueshifted
Absorption Components (BEC) up to 100 km/s in the Na I lines. No correlation is
observed between the appearance of the Na I RAC & BEC and the H$_\alpha$ and He
I line variability, which suggests that these (Na I RAC & BEC) are formed in a
process unrelated to the circumstellar gas accretion. We interpret the Na I RAC
as evidence for an infalling evaporating body, greater than 100 km in diameter,
which is able to survive at distances between 2.0 to 0.1 AU from the star. The
dramatic appearance of the sodium RAC and mild BEC is readily explained by the
dynamics of this infalling body making LkH$_\alpha$234 the youngest (age $\sim$
0.1 Myr) system with evidence for the presence of planetesimals.


title: Hard-X-Ray Optics Development at Marshall Space Flight Center

abstract:
  This paper summarizes the current status of the development of hard-X-ray
optics using nickel replication at NASA's Marshall Space Flight Center.


title:
GRB 020410: A Gamma-Ray Burst Afterglow Discovered by its Supernova
  Light

abstract:
  We present the discovery and monitoring of the optical transient (OT)
associated with GRB 020410. The fading OT was found by Hubble Space Telescope
(HST) observations taken 28 and 65 days after burst at a position consistent
with the X-ray afterglow. Subsequent re-examination of early ground based
observations revealed that a faint OT was present 6 hours after burst,
confirming the source association with GRB 020410. A deep non-detection after
one week requires that the OT re-brightened between day 7 and day 28, and
further late time HST data taken approximately 100 days after burst imply that
it is very red.We compare both the flux and color of the excess with supernova
models and show that the data are best explained by the presence of a Type Ib/c
supernova at a redshift z ~ 0.5, which occured roughly coincident with the day
of GRB.


title: The supernova 2003lw associated with X-ray flash 031203

abstract:
  The X-Ray Flash (XRF), 031203 with a host galaxy at z=0.1055, is, apart from
GRB980425, the closest Gamma-Ray Burst (GRB) or XRF known to date. We monitored
its host galaxy from 1-100 days after the burst. In spite of the high
extinction to the source and the bright host, a significant increase and
subsequent decrease has been detected in the apparent brightness of the host,
peaking between 10 and 33 days after the GRB. The only convincing explanation
is a supernova (SN) associated with the XRF, SN2003lw. This is the earliest
time at which a SN signal is clearly discernible in a GRB/XRF (apart from
SN1998bw). SN2003lw is extremely luminous with a broad peak and can be
approximately represented by the lightcurve of SN1998bw brightened by ~0.55
mag, implying a hypernova, as observed in most GRB-SNe. The XRF-SN association
firmly links XRFs with the deaths of massive stars and further strengthens
their connection with GRBs. The fact that SNe are also associated with XRFs
implies that Swift may detect a significant population of intermediate redshift
SNe very soon after the SN explosions, a sample ideally suited for detailed
studies of early SN physics.


title:
Optical Imaging and Spectroscopy of the Edge-On Sbc Galaxy UGC10043:
  Evidence for a Galactic Wind and a Peculiar Triaxial Bulge

abstract:
  We present new optical imaging and spectroscopy of the peculiar, edge-on Sbc
galaxy UGC10043. B & R imaging reveals that the inner bulge of UGC10043 is
elongated perpendicular to the major axis. At larger r, the bulge isophotes
twist to become oblate and nearly circular, suggesting the bulge is triaxial.
Based on stellar and ionized gas kinematics, the bulge shows no clear evidence
for rotation about either its major or minor axis. The southwestern quadrant of
the bulge is girdled by a narrow dust lane parallel to the minor axis that may
be part of an inner polar ring. The stellar disk of UGC10043 has a low optical
surface brightness, a small scale height, a mild integral sign warp, and a
dusty, inner region that appears tilted relative to the outlying disk. The HA
and [NII] emission lines in UGC10043 resolve into multiple velocity components,
indicating the presence of a large-scale galactic wind with an outflow velocity
of ~104 km/s. HA+[NII] imaging reaffirms this picture by revealing ionized gas
extended to |z|~3.5kpc in a biconical structure. The [NII]/HA line intensity
ratio increases with increasing distance from the plane, reaching values as
high as 1.7. Unlike most galaxies with large-scale winds, UGC10043 has only a
modest global star formation rate (~1M_sun/yr), implying the wind is powered by
a rather feeble central starburst. We discuss evolutionary scenarios that could
account for both the structural complexities of UGC10043 and its large-scale
wind. [Abridged]


title: GMRT Discovery of A Millisecond Pulsar in a Very Eccentric Binary System

abstract:
  We report the discovery of the binary millisecond pulsar J0514-4002A, which
is the first known pulsar in the globular cluster NGC 1851 and the first pulsar
discovered using the Giant Metrewave Radio Telescope (GMRT). The pulsar has a
rotational period of 4.99 ms, an orbital period of 18.8 days, and the most
eccentric pulsar orbit yet measured (e = 0.89). The companion has a minimum
mass of 0.9 M_sun and its nature is presently unclear. After accreting matter
from a low-mass companion star which spun it up to a (few) millisecond spin
period, the pulsar eventually exchanged the low-mass star for its more massive
present companion. This is exactly the same process that could form a system
containing a millisecond pulsar and a black hole; the discovery of NGC 1851A
demonstrates that such systems might exist in the Universe, provided that
stellar mass black holes exist in globular clusters.


title:
R=100,000 Mid-IR Spectroscopy of UCHII Regions: High Resolution is Worth
  it!

abstract:
  Ultracompact HII regions are signposts of massive star formation and their
properties provide diagnostics for the characteristics of very young O stars
embedded in molecular clouds. While radio observations have given us a good
picture of the morphology of these regions, they have not provided clear
information about the kinematics. Using high spectral resolution observations
of the 12.8 micron [NeII] line, it has been possible for the first time to
trace the internal kinematics of several ultracompact HII regions. We find that
the motions in the cometary ultracompact HII regions MonR2 and G29.96-0.02 are
highly organized. The velocity patterns are consistent with parabolic ionized
flows along a neutral boundary layer.


title: Evolution Since z=1 of the Morphology-density Relation of Galaxies

abstract:
  We measure the morphology-density relation of galaxies at z=1 across the full
three orders of magnitude in projected galaxy density available in low-redshift
studies. Our study adopts techniques that are comparable with those applied at
lower redshifts, allowing a direct investigation of how the morphological
segregation of galaxies has evolved over the last 8 Gyr. Although the
morphology-density relation, as described by the fraction of early-type (E+S0)
galaxies, was in place at z=1, its form differs from that observed at both z=0
and z=0.5. In the highest density regions the early-type fraction has increased
steadily with time from f(E+S0)=0.7+/-0.1 at z=1 to f(E+S0)=0.9+/-0.1 at the
present epoch. However, in intermediate density regions corresponding to groups
and the accretion regions of rich clusters, significant evolution appears to
begin only after z=0.5. Finally, at the lowest densities, no evolution is
observed for the early-type fraction of field galaxies which remains constant
at f(E+S0)=0.4+/-0.1 at all epochs. We examine a simple picture consistent with
these observations where the early-type population at z=1 is comprised largely
of elliptical galaxies. Subsequent evolution in both intermediate and dense
regions is attributed to the transformation of spirals into lenticulars.
Further progress in verifying our hypothesis may be achieved through
distinguishing ellipticals and lenticulars at these redshifts through resolved
dynamical studies of representative systems.


title:
SparsePak: A Formatted Fiber Field Unit for The WIYN Telescope Bench
  Spectrograph. I. Design, Construction, and Calibration

abstract:
  We describe the design and construction of a formatted fiber field-unit,
SparsePak, and characterize its optical and astrometric performance. This array
is optimized for spectroscopy of low-surface brightness, extended sources in
the visible and near-infrared. SparsePak contains 82, 4.7" fibers subtending an
area of 72"x71" in the telescope focal plane, and feeds the WIYN Bench
spectrograph. Together, these instruments are capable of achieving spectral
resolutions of lambda/dlambda ~ 20000 and an area--solid-angle product of ~140
arcsec^2 m^2 per fiber. Laboratory measurements of SparsePak lead to several
important conclusions on the design of fiber termination and cable curvature to
minimize focal ratio degradation. SparsePak itself has throughput >80% redwards
of 5200 A, and 90-92% in the red. Fed at f/6.3, the cable delivers an output
90% encircled energy at nearly f/5.2. This has implications for performance
gains if the WIYN Bench Spectrograph had a faster collimator. Our approach to
integral-field spectroscopy yields an instrument which is simple and
inexpensive to build, yet yields the highest area--solid-angle product per
spectrum of any system in existence. An Appendix details the fabrication
process in sufficient detail for others to repeat. SparsePak was funded by the
National Science Foundation and the University of Wisconsin-Madison Graduate
School, and is now publicly available on the WIYN Telescope through the
National Optical Astronomical Observatories.


title: Explaining Low Redshift Quasar Evolution

abstract:
  We have developed a flexible framework for constructing physical models of
quasar evolution that can incorporate a wide variety of observational
constraints, such as multi-wavelength quasar luminosity functions (QLFs),
estimated masses and accretion rates of active black holes, space densities of
quasar host galaxies, clustering measurements, and the mass function of black
holes in the local universe. In this brief contribution we focus on the
observed decline in the QLF break luminosity at $z<2$, which can be explained
either by a shift toward lower characteristic accretion rates at low $z$ or by
preferential suppression of activity in higher mass black holes.


title:
GRAPES, Grism Spectroscopy of the Hubble Ultra Deep Field: Description
  and Data Reduction

abstract:
  We present deep unbiased spectroscopy of the Hubble Ultra Deep Field (UDF)
carried out using the slitless grism spectroscopy mode of the Advance Camera
for Surveys on the Hubble Space Telescope (HST). The GRIsm ACS Program for
Extragalactic Science (GRAPES) achieves continuum detection as faint as
$z_{AB}=27.2$ using 40 orbits ($9.2 \times 10^4$ seconds) on HST. The data were
taken at four orientation angles to correct for the overlap of spectra. GRAPES
data provide a unique, uninterrupted, low resolution (R=100) spectral coverage
for $5500\AA < \lambda < 10500\AA$, and allow us to detect high redshift
galaxies at $4 < z < 7$ whether they have $\lya$ lines or just show the Lyman
Break, as well as find low luminosity AGNs in an unbiased fashion. This paper
describes in detail the observations and the data reduction, and examines the
quality of the extracted spectra. Subsequent papers will deal with the analysis
of the data. The extracted and calibrated GRAPES spectra will be available from
MAST at STScI.


title:
Constraints on Planetary Companions in the Magnification A=256
  Microlensing Event: OGLE-2003-BLG-423

abstract:
  We develop a new method of modeling microlensing events based on a Monte
Carlo simulation that incorporates both a Galactic model and the constraints
imposed by the observed characteristics of the event. The method provides an
unbiased way to analyze the event especially when parameters are poorly
constrained by the observed lightcurve. We apply this method to search for
planetary companions of the lens in OGLE-2003-BLG-423, whose maximum
magnification A_max=256+-43 (or A_max=400+-115 from the lightcurve data alone)
is the highest among single-lens events ever recorded. The method permits us,
for the first time, to place constraints directly in the
planet-mass/projected-physical-separation plane rather than in the
mass-ratio/Einstein-radius plane as was done previously. For example,
Jupiter-mass companions of main-sequence stars at 2.5 AU are excluded with 80%
efficiency.


title: A cool disk in the Galactic Center?

abstract:
  We study the possibility of a cool disk existing in the Galactic Center in
the framework of the disk-corona evaporation/condensation model. Assuming an
inactive disk, a hot corona should form above the disk since there is a
continuous supply of hot gas from stellar winds of the close-by massive stars.
Whether the cool disk can survive depends on the mass exchange between the disk
and corona. If the disk-corona interaction is dominated by evaporation and the
rate is larger than the Bondi accretion rate in the Galactic Center, the disk
will be depleted within a certain time period and no persistent disk will
exist. On the other hand, if the interaction results in hot gas steadily
condensing into the disk, an inactive cool disk might survive. For this case we
further investigate the Bremsstrahlung radiation from the hot corona and
compare it with the observed X-ray luminosity. Our model shows that, for
standard viscosity in the corona (alpha=0.3), the mass evaporation rate is much
higher than the Bondi accretion rate and the coronal density is much larger
than that inferred from Chandra observations. An inactive disk can not survive
such strong evaporation. For small viscosity (alpha<0.07) we find condensation
solutions. But detailed computations show that in this case there is too much
X-ray radiation from the corona to be in agreement with the observations.
Therefore, we conclude that there should be no thin/inactive disk presently in
the Galactic Center. However, we do not exclude that the alternative
non-radiative model of Nayakshin (2004) might instead be realized in nature.


title:
Early Afterglow Emission from a Reverse Shock as a Diagnostic Tool for
  GRB Outflows

abstract:
  The Gamma-Ray burst (GRB) - afterglow transition is one of the most
interesting and least studied GRB phases. During this phase the relativistic
ejecta begins interacting with the surrounding matter. A strong short lived
reverse shock propagates into the ejecta (provided that it is baryonic) while
the forward shock begins to shape the surrounding matter into a Blandford-McKee
profile. We suggest a parametrization of the early afterglow light curve and we
calculate (analytically and numerically) the observed parameters that results
from a reverse shock emission (in an interstellar medium [ISM] environment). We
present a new fingerprint of the reverse shock emission that is added to the
well known $t^{-2}$ optical decay. Observation of this signature would indicate
that the reverse shock dominates the emission during the early afterglow. The
existence of a reverse shock will in turn imply that the relativistic ejecta
contains a significant baryonic component. This signature would also imply that
the surrounding medium is an ISM. We further show that: (i) The reverse shock
optical flash depends strongly on initial conditions of the relativistic
ejecta. (ii) Previous calculations have generally overestimated the strength of
this optical flash. (iii) If the reverse shock dominates the optical flash then
detailed observations of the early afterglow light curve would possibly enable
us to determine the initial physical conditions within the relativistic ejecta
and specifically to estimate its Lorentz factor and its width.


title: UV light from young stars in GEMS quasar host galaxies at 1.8<z<2.75

abstract:
  We have performed HST imaging of a sample of 23 high-redshift (1.8<z<2.75)
AGN, drawn from the COMBO-17 survey. The sample contains moderately luminous
quasars (M_B ~ -23). The data are part of the GEMS imaging survey that provides
high resolution optical images obtained with ACS in two bands (F606W and
F850LP), sampling the rest-frame UV flux of the targets. To deblend the AGN
images into nuclear and resolved (host galaxy) components we use a PSF
subtraction technique that is strictly conservative with respect to the flux of
the host galaxy. We resolve the host galaxies in both filter bands in 9 of the
23 AGN, whereas the remaining 14 objects are considered non-detections, with
upper limits of less than 5% of the nuclear flux. However, when we coadd the
unresolved AGN images into a single high signal-to-noise composite image we
find again an unambiguously resolved host galaxy. The recovered host galaxies
have apparent magnitudes of 23.0<F606W<26.0 and 22.5<F850LP<24.5 with
rest-frame UV colours in the range -0.2<(F606W-F850LP)_obs<2.3. The rest-frame
absolute magnitudes at 200 nm are -20.0<M_200nm<-22.2. The photometric
properties of the composite host are consistent with the individual resolved
host galaxies. We find that the UV colors of all host galaxies are
substantially bluer than expected from an old population of stars with
formation redshift z=5, independent of the assumed metallicities. These UV
colours and luminosities range up to the values found for Lyman-break galaxies
(LBGs) at z=3. Our results agree with the recent discovery of enhanced blue
stellar light in AGN hosts at lower redshifts. [abridged]


title:
The Spectra and Variability of X-ray Sources in a Deep Chandra
  Observation of the Galactic Center

abstract:
  We examine the X-ray spectra and variability of the sample of X-ray sources
with L_X = 10^{31}-10^{33} erg s^{-1} identified within the inner 9' of the
Galaxy. Very few of the sources exhibit intra-day or inter-month variations. We
find that the spectra of the point sources near the Galactic center are very
hard between 2--8 keV, even after accounting for absorption. When modeled as
power laws the median photon index is Gamma=0.7, while when modeled as thermal
plasma we can only obtain lower limits to the temperature of kT>8 keV. The
combined spectra of the point sources is similarly hard, with a photon index of
Gamma=0.8. Strong line emission is observed from low-ionization, He-like, and
H-like Fe, both in the average spectra and in the brightest individual sources.
The line ratios of the highly-ionized Fe in the average spectra are consistent
with emission from a plasma in thermal equilibrium. This line emission is
observed whether average spectra are examined as a function of the count rate
from the source, or as a function of the hardness ratios of individual sources.
This suggests that the hardness of the spectra may in fact to due local
absorption that partially-covers the X-ray emitting regions in the Galactic
center systems. We suggest that most of these sources are intermediate polars,
which (1) often exhibit hard spectra with prominent Fe lines, (2) rarely
exhibit either flares on short time scales or changes in their mean X-ray flux
on long time scales, and (3) are the most numerous hard X-ray sources with
comparable luminosities in the Galaxy.


title:
Abundance analysis of targets for the COROT / MONS asteroseismology
  missions II. Abundance analysis of the COROT main targets

abstract:
  One of the goals of the ground-based support program for the COROT and Roemer
satellite missions is to characterize suitable target stars for the part of the
missions dedicated to asteroseismology. We present the detailed abundance
analysis of nine of the potential COROT main targets using the semi-automatic
software VWA. For two additional COROT targets we could not perform the
analysis due to the high rotational velocity of these stars. For five stars
with low rotational velocity we have also performed abundance analysis by a
classical equivalent width method in order to test the reliability of the VWA
software. The agreement between the different methods is good. We find that it
is necessary to measure abundances extracted from each line relative to the
abundances found from a spectrum of the Sun in order to remove systematic
errors. We have constrained the global atmospheric parameters Teff, log g, and
[Fe/H] to within 70-100 K, 0.1-0.2 dex, and 0.1 dex for five stars which are
slow rotators (v sin i < 15 km/s). For most of the stars stars we find good
agreement with the parameters found from line depth ratios, H-alpha lines,
Str\"omgren indices, previous spectroscopic studies, and also log g determined
from the HIPPARCOS parallaxes. For the fast rotators v sin i > 60 km/s it is
not possible to constrain the atmospheric parameters.


title: Dust and gas obscuration in ELAIS Deep X-ray Survey reddened quasars

abstract:
  Hard X-ray surveys have uncovered a large population of heavily obscured AGN.
They also reveal a population of quasars with moderate obscuration at both
visible and X-ray wavelengths. We use Chandra selected samples of quasars from
the ELAIS Deep X-ray Survey (EDXS) and CDF-N to investigate the obscuration
towards the nuclei of moderately obscured AGN. We find an inverse correlation
between the optical to X-ray flux ratio and the X-ray hardness ratio which can
be interpreted as due to obscuration at visible and X-ray wavelengths. We
present detailed optical and near-infrared data for a sample of optically-faint
(R>23) quasars from the EDXS. These are used to constrain the amount of
rest-frame UV/optical reddening towards these quasars. It is found that
optically-faint quasars are mostly faint due to obscuration, not because they
are intrinsically weak. After correcting for reddening, the optical magnitudes
of most of these quasars are similar to the brighter quasars at these X-ray
fluxes. Combining with gas column densities inferred from the X-ray
observations we consider the gas-to-dust ratios of the obscuring matter. We
find that the quasars generally have higher gas-to-dust absorption than that
seen in the Milky Way - similar to what has been found for nearby Seyfert
galaxies. We consider the possible existence of a large population of X-ray
sources which have optical properties of Type 1 (unobscured) quasars, but X-ray
properties of Type 2 (obscured) quasars. We show that the observed distribution
of optical-to-X-ray flux ratios of quasars at z>1 is skewed to low values
compared to the intrinsic distribution...


title: X-ray Luminosity Functions of Active Galactic Nuclei

abstract:
  In this proceedings paper, I overview the current status of the X-ray
luminosity function of AGNs in the soft (0.5-2 keV) band, extended using
XMM-Newton and Chandra survey data. We found that the number density of low
luminosity AGNs peaks later in the history of the universe (z~1) than the that
of high luminosity AGNs (z~1.7-3). I also describe the basic results of a
spectroscopic followup project of a complete HEAO-1 hard X-ray limited sample
of AGNs using ASCA and XMM-Newton and present separate intrinsic hard X-ray
luminosity functions for unabsorbed and absorbed AGNs. We found that the
absorbed AGN XLF drops more rapidly at high luminosities, indicating a
deficiency of absorbed luminous AGNs.