title: Pulsar Parallaxes at 5 GHz with the Very Long Baseline Array

abstract:
  We present the first pulsar parallaxes measured with phase-referenced pulsar
VLBI observations at 5 GHz. Due to the steep spectra of pulsars, previous
astrometric measurements have been at lower frequencies. However, the strongest
pulsars can be observed at 5 GHz, offering the benefit of lower combined
ionospheric and tropospheric phase errors, which usually limit VLBI astrometric
accuracy. The pulsars B0329+54, B0355+54 and B1929+10 were observed for 7
epochs spread evenly over 2 years. For B0329+54, large systematic errors lead
to only an upper limit on the parallax (pi < 1.5 mas). A new proper motion and
parallax were measured for B0355+54 (pi = 0.91 +- 0.16 mas), implying a
distance of 1.04+0.21-0.16 kpc and a transverse velocity of 61+12-9 km/s. The
parallax and proper motion for B1929+10 were significantly improved (pi = 2.77
+- 0.07 mas), yielding a distance of 361+10-8 pc and a transverse velocity of
177+4-5 km/s. We demonstrate that the astrometric errors are correlated with
the angular separation between the phase reference calibrator and the target
source, with significantly lower errors at 5 GHz compared to 1.6 GHz. Finally,
based on our new distance determinations for B1929+10 and B0355+54, we derive
or constrain the luminosities of each pulsar at high energies. We show that,
for thermal emission models, the emitting area for X-rays from PSR B1929+10 is
roughly consistent with the canonical size for a heated polar cap, and that the
conversion of spin-down power to gamma-ray luminosity in B0355+54 must be low.
The new proper motion for B1929+10 also implies that its progenitor is unlikely
to have been the binary companion of the runaway O-star zeta-Ophiuchi.


title: Extrasolar Planet Orbits and Eccentricities

abstract:
  The known extrasolar planets exhibit many interesting and surprising
features--extremely short-period orbits, high-eccentricity orbits, mean-motion
and secular resonances, etc.--and have dramatically expanded our appreciation
of the diversity of possible planetary systems. In this review we summarize the
orbital properties of extrasolar planets. One of the most remarkable features
of extrasolar planets is their high eccentricities, far larger than seen in the
solar system. We review theoretical explanations for large eccentricities and
point out the successes and shortcomings of existing theories.


title: Simulations of small-scale turbulent dynamo

abstract:
  We report an extensive numerical study of the small-scale turbulent dynamo at
large magnetic Prandtl numbers Pm. A Pm scan is given for the model case of
low-Reynolds-number turbulence. We concentrate on three topics: magnetic-energy
spectra and saturation levels, the structure of the field lines, and the
field-strength distribution. The main results are (1) the folded structure
(direction reversals at the resistive scale, field lines curved at the scale of
the flow) persists from the kinematic to the nonlinear regime; (2) the field
distribution is self-similar and appears to be lognormal during the kinematic
regime and exponential in the saturated state; and (3) the bulk of the magnetic
energy is at the resistive scale in the kinematic regime and remains there
after saturation, although the spectrum becomes much shallower. We propose an
analytical model of saturation based on the idea of partial
two-dimensionalization of the velocity gradients with respect to the local
direction of the magnetic folds. The model-predicted spectra are in excellent
agreement with numerical results. Comparisons with large-Re, moderate-Pm runs
are carried out to confirm the relevance of these results. New features at
large Re are elongation of the folds in the nonlinear regime from the viscous
scale to the box scale and the presence of an intermediate nonlinear stage of
slower-than-exponential magnetic-energy growth accompanied by an increase of
the resistive scale and partial suppression of the kinetic-energy spectrum in
the inertial range. Numerical results for the saturated state do not support
scale-by-scale equipartition between magnetic and kinetic energies, with a
definite excess of magnetic energy at small scales. A physical picture of the
saturated state is proposed.


title:
The Theory of Relativistic Jet Formation in Galactic Sources: Towards a
  Unified MOdel

abstract:
  I review recent progress in the theory of relativistic jet production. The
presently favored mechanism is an electrodynamic one, in which charged plasma
is accelerated by electric fields that are generated by a rotating magnetic
field. The most pressing issues of current interest are understanding what
factors control the jet power, its speed, and its degree of collimation, and
how these properties determine the type of jet observed and its effect on its
environment. Recent observations of microquasars, pulsars, gamma-ray bursts
(GRBs) and core-collapse supernovae indicate that jets play an important, and
in some cases possibly dominant, role in each of these. The presence of a jet
in all cases may provide an important clue to how these sources may be related.
Based on these observations, and on recent theoretical investigations, I
propose an evolutionary scheme that attempts to unify all of these relativistic
galactic jet sources. I also discuss several important issues that must be
resolved before this (or another scheme) can be adopted.


title:
The Theory and Simulation of Relativistic Jet Formation: Towards a
  Unified Model For Micro- and Macroquasars

abstract:
  I review recent progress in the theory of relativistic jet production, with
special emphasis on unifying black hole sources of stellar and supermassive
size. Observations of both classes of objects, as well as theoretical
considerations, indicate that such jets may be launched with a spine/sheath
flow structure, having a much higher Lorentz factor ($\sim 50$) near the axis
and a lower speed ($\Gamma \sim 10$ or so) away from the axis. It has become
clear that one can no longer consider models of accretion flows without also
considering the production of a jet by that flow. Furthermore, the rotation
rate of the black hole also must be taken into account. It provides a third
parameter that should break the mass/accretion rate degeneracy and perhaps
explain why some sources are radio loud and some radio quiet. Slow jet
acceleration and collimation is expected theoretically, and can explain some of
the observed features of AGN jet sources. Finally, relativistic jets launched
by MHD/ED processes are Poynting flux dominated by nature, and are potentially
unstable if there is significant entrainment of thermal material.


title: SIMsim: An End-to-End Simulation of The Space Interferometer Mission

abstract:
  We present the basic elements and first results of an end-to-end simulation
package whose purpose is to test the validity of the Space Interferometer
Mission design. The fundamental simulation time step is one millisecond, with
substructure at 1/8 ms, and the total duration of the simulation is five years.
The end product of a given "wide-angle" astrometry run is an estimated grid
star catalog over the entire sky with an accuracy of about 4 micro-arcseconds.
  SIMsim is divided into five separate modules that communicate via data pipes.
The first generates the 'truth' data on the spacecraft structure and laser
metrology. The second module generates uncorrupted fringes for the three SIM
interferometers, based on the current spacecraft orientation, target stars'
positions, etc. The third module reads out the CCD white light fringe data at
specified times, corrupting that and the metrology data with appropriate
errors. The data stream out of this module represents the basic data stream on
the simulated spacecraft. The fourth module performs fringe-fitting tasks on
this data, recovering the total path delay, and the fifth and final module
inverts the entire metrology/delay dataset to ultimately determine the
instantaneous path delay on a fiducial baseline fixed in space. (Pathlength
feed forward is used every few milliseconds to re-position the interferometer
to keep the fringes in the delay window.) The average of all such delays over
an integration time (typically 30 s) is reported as one of several hundred
thousand measured stellar delays over the five-year period, which are then
inverted to produce the simulated catalog.
  Future plans include taking into account more sources of error from the SIM
error budget and including narrow angle observations in the observing plan.


title: MHD Supernova Jets: The Missing Link

abstract:
  We review recent progress in the theory of jet production, with particular
emphasis on the possibility of 1) powerful jets being produced in the first few
seconds after collapse of a supernova core and 2) those jets being responsible
for the asymmetric explosion itself. The presently favored jet-production
mechanism is an electrodynamic one, in which charged plasma is accelerated by
electric fields that are generated by a rotating magnetic field anchored in the
protopulsar. Recent observations of Galactic jet sources provide important
clues to how {\em all} such sources may be related, both in the physical
mechanism that drives the jet in the astrophysical mechanisms that create
conditions conducive to jet formation. We propose a grand evolutionary scheme
that attempts to unify these sources on this basis, with MHD supernovae
providing the missing link. We also discuss several important issues that must
be resolved before this (or another scheme) can be adopted.


title: Massive Field Stars and the Stellar Clustering Law

abstract:
  The distribution of N*, the number of OB stars per association or cluster,
appears to follow a universal power-law form $N*^{-2}$ in the local Universe.
We evaluate the distribution of N* in the Small Magellanic Cloud using recent
broadband optical and space-ultraviolet data, with special attention to the
lowest values of N*. We find that the power-law distribution in N* continues
smoothly down to N*=1. This strongly suggests that the formation of field
massive stars is a continuous process with those in associations, and that the
field stars do not originate from a different star formation mode. Our results
are consistent with the model that field massive stars represent the most
massive members in groups of smaller stars, as expected if the clustering law
applies to much lower masses as is expected from the stellar initial mass
function (IMF). These results are consistent with the simultaneous existence of
a universal IMF and a universal clustering law. Jointly, these laws imply that
the fraction of field OB stars typically ranges from about 35% to 7% for most
astrophysical situations, with an inverse logarithmic dependence on the most
populous cluster, and hence, on galaxy size and/or star formation rate. There
are important consequences for global feedback effects in galaxies: field stars
should therefore contribute proportionately to the volume of the warm ionized
medium, and equal relative contributions by superbubbles of all sizes to the
interstellar porosity are expected.


title:
Constrained Transport Algorithms for Numerical Relativity. I.
  Development of a Finite Difference Scheme

abstract:
  A scheme is presented for accurately propagating the gravitational field
constraints in finite difference implementations of numerical relativity. The
method is based on similar techniques used in astrophysical
magnetohydrodynamics and engineering electromagnetics, and has properties of a
finite differential calculus on a four-dimensional manifold. It is motivated by
the arguments that 1) an evolutionary scheme that naturally satisfies the
Bianchi identities will propagate the constraints, and 2) methods in which
temporal and spatial derivatives commute will satisfy the Bianchi identities
implicitly. The proposed algorithm exactly propagates the constraints in a
local Riemann normal coordinate system; {\it i.e.}, all terms in the Bianchi
identities (which all vary as $\partial^3 g$) cancel to machine roundoff
accuracy at each time step. In a general coordinate basis, these terms, and
those that vary as $\partial g\partial^2 g$, also can be made to cancel, but
differences of connection terms, proportional to $(\partial g)^3$, will remain,
resulting in a net truncation error. Detailed and complex numerical experiments
with four-dimensional staggered grids will be needed to completely examine the
stability and convergence properties of this method.
  If such techniques are successful for finite difference implementations of
numerical relativity, other implementations, such as finite element (and
eventually pseudo-spectral) techniques, might benefit from schemes that use
four-dimensional grids and that have temporal and spatial derivatives that
commute.


title: Ohm's Law in the Fast Lane: General Relativistic Charge Dynamics

abstract:
  Fully relativistic and causal equations for the flow of charge in curved
spacetime are derived. It is believed that this is the first set of equations
to be published that correctly describes the flow of charge, and evolution of
the electromagnetic field, in highly dynamical relativistic environments on
time scales much shorter than the collapse time ($GM/c^3$). The equations will
be important for correctly investigating problems such as the dynamical
collapse of magnetized stellar cores to black holes and the production of jets
and gravitational waves. This system of equations, given the name of `charge
dynamics', is analogous to those of hydrodynamics (which describe the flow of
{\em mass} in spacetime rather than the flow of charge). The most important one
in the system is the relativistic generalized Ohm's law, which is used to
compute time-dependent four-current. Unlike previous equations for the current,
this one ensures that charge drift velocities remain less than the speed of
light, takes into account the finite current rise time, is expressed in a
covariant form, and is suitable for general relativistic computations in an
arbitrary metric. It includes the standard known effects (Lorentz force, Hall
effect, pressure effect, and resistivity) and reduces to known forms of Ohm's
law in the appropriate limits. In addition, the plasma particles are allowed to
have highly relativistic drift velocities, resulting in an implicit equation
for the `current beaming factor' $\gamma_q$.


title: Magnesium isotope ratios in Hyades stars

abstract:
  Using classical model atmospheres and an LTE analysis, Mg isotope ratios
24Mg:25Mg:26Mg are measured in 32 Hyades dwarfs covering 4000K < Teff < 5000K.
We find no significant trend in any isotope ratio versus Teff and the mean
isotope ratio is in excellent agreement with the solar value. We determine
stellar parameters and Fe abundances for 56 Hyades dwarfs covering 4000K < Teff
< 6200K. For stars warmer than 4700K, we derive a cluster mean value of [Fe/H]
= 0.16 +/- 0.02 (sigma=0.1), in good agreement with previous studies. For stars
cooler than 4700K, we find that the abundance of Fe from ionized lines exceeds
the abundance of Fe from neutral lines. At 4700K [Fe/H]_II - [Fe/H]_I = 0.3 dex
while at 4000K [Fe/H]_II - [Fe/H]_I = 1.2 dex. This discrepancy between the Fe
abundance from neutral and ionized lines likely reflects inadequacies in the
model atmospheres and the presence of Non-LTE or other effects. Despite the
inability of the models to reproduce ionization equilibrium for Fe, the Mg
isotope ratios appear immune to these problems and remain a powerful tool for
studying Galactic chemical evolution.


title: 3-D Simulations of MHD Jets - The Stability Problem

abstract:
  Non-relativistic three-dimensional magnetohydrodynamic simulations of
Poynting-flux-dominated (PFD) jets are presented. Our study focuses on the
propagation of strongly magnetized hypersonic but sub-Alfv\'enic flow ($C_{\rm
s}^2 << V_{\rm jet}^2 < V_{\rm A}^2$) and the development of a current-driven
(CD) kink instability. This instability may be responsible for the "wiggled"
structures seen in VLBI-scale AGN jets. In the present paper we investigate the
nonlinear behavior of PFD jets in a variety of external ambient magnetized gas
distributions, including those with density, pressure, and temperature
gradients. Our numerical results show that PFD jets can develop kink
distortions in the trans-Alfv\'enic flow case, even when the flow itself is
still strongly magnetically dominated. In the nonlinear development of the
instability, a non-axisymmetric mode grows on time scales of order the Alfv\'en
crossing time (in the jet frame) and proceeds to disrupt the kinematic and
magnetic structure of the jet. Because of a large scale poloidal magnetic field
in the ambient medium, the growth of surface modes ({\it i.e.}, MHD
Kelvin-Helmholtz instabilities) is suppressed. The CD kink mode ($m = 1$) grows
faster than the other higher order modes ($m > 1$), driven in large part by the
radial component of the Lorentz force.


title:
The First Detailed X-ray Observations of High-Redshift,
  Optically-Selected Clusters: XMM-Newton Results for Cl 1324+3011 at z = 0.76
  and Cl 1604+4304 at z = 0.90

abstract:
  We present the first detailed X-ray observations of optically-selected
clusters at high redshift. Two clusters, Cl 1324+3011 at z = 0.76 and Cl
1604+4304 at z = 0.90, were observed with XMM-Newton. The optical center of
each cluster is coincident with an extended X-ray source whose emission is
detected out to a radius of 0.5 Mpc. The emission from each cluster appears
reasonably circular, with some indication of asymmetries and more complex
morphologies. Similarly to other optically-selected clusters at redshifts of z
> 0.4, both clusters are modest X-ray emitters with bolometric luminosities of
only Lx = 1.4 - 2.0 x 10^(44) erg/s. We measure gas temperatures of T = 2.88
(+0.71/-0.49) keV for Cl 1324+3011 and 2.51 (+1.05/-0.69) keV for Cl 1604+4304.
The X-ray properties of both clusters are consistent with the high-redshift
Lx-T relation measured from X-ray-selected samples at z > 0.5. However, based
on the local relations, their X-ray luminosities and temperatures are low for
their measured velocity dispersions (sigma). The clusters are cooler by a
factor of 2 - 9 compared to the local sigma-T relation. We briefly discuss the
possible explanations for these results.


title: X-ray Flux Related Timing and Spectral Features of 2S 1417-62

abstract:
  RXTE observations of the X-ray transient pulsar 2S 1417-62 between 1999
November and 2000 August with a total exposure of $\sim 394$ ksec were
analyzed. Observations include a main outburst followed by a series of mini
outbursts. Changes in pulse morphology and pulse fraction were found to be
related to the changes in X-ray flux. Particularly low X-ray flux regions were
found to have significantly lower pulse fractions with different pulse
morphologies. The 3-60 keV PCA-HEXTE main outburst spectrum was modeled with an
absorbed power law model with high energy cut-off and a Gaussian Iron line
complex feature. Using the same spectral model, individual 3-20 keV PCA spectra
were found to be softer and less absorbed in low X-ray flux regions between
outbursts. Spectral studies showed that hydrogen column density was correlated,
and the power law index was anti-correlated with the 3-20 keV X-ray flux. X-ray
flux related spectral and timing features in 2S 1417-62 except for low X-ray
flux regions were interpreted as a sign of disc accretion with a similar
accretion geometry with a varying mass accretion rate ($\dot{M}$), whereas
spectral and timing features of the low X-ray flux regions were interpreted as
a sign of possible temporary accretion geometry change prior to the next
periastron where $\dot{M}$ increases again to restore the original accretion
geometry.


title:
A newly identified Luminous Blue Variable in the galactic starburst
  cluster Westerlund 1

abstract:
  We present observations of the massive transitional star W243 in Westerlund
1. We find an apparent spectral type of early-mid A from our data, in contrast
to an earlier classification of B2I, made from data obtained in 1981. The
concurrent development of a rich emission line spectrum suggests a very high
mass loss rate; the continued presence of HeI emission suggesting that the
underlying star remains significantly hotter than implied by its apparent
spectral type. We suggest that W243 is a Luminous Blue Variable undergoing an
eruptive phase, leading to an extreme mass loss rate and the formation of a
pseudo photosphere.


title: The Skysoft Project

abstract:
  We present the Skysoft project (http://www.skysoft.org). Skysoft is a YAASD
(Yet Another Astronomical Software Directory), but with a different overall
approach. To be useful, Skysoft needs to be a long-lived project, setting
little pressure for maintenance, imposing a very low nuisance level to the
developers community, and requiring a low maintenance cost. Our aim is to
design Skysoft as a community-supported directory, to which everyone can
contribute, both developers and end-users.


title:
General Relativistic MHD Simulations of the Gravitational Collapse of a
  Rotating Star with Magnetic Field as a Model of Gamma-Ray Bursts

abstract:
  We have performed 2.5-dimensional general relativistic magnetohydrodynamic
(MHD) simulations of the gravitational collapse of a magnetized rotating
massive star as a model of gamma ray bursts (GRBs). This simulation showed the
formation of a disk-like structure and the generation of a jet-like outflow
inside the shock wave launched at the core bounce. We have found the jet is
accelerated by the magnetic pressure and the centrifugal force and is
collimated by the pinching force of the toroidal magnetic field amplified by
the rotation and the effect of geometry of the poloidal magnetic field. The
maximum velocity of the jet is mildly relativistic ($\sim$ 0.3 c).


title: An extragalactic HII region in the Virgo cluster

abstract:
  We present spectroscopic observations for six emission-line objects projected
onto the Virgo cluster. These sources have been selected from narrow band
(H\alpha+[NII]) images showing faint detectable continuum emission and EW>100
Angstrom. Five of these sources result [OIII]\lambda 5007 emitters at z ~ 0.31,
while one 122603+130724 is confirmed to be an HII region belonging to the Virgo
cluster. This point-like source has a recessional velocity of ~ 200 km/s, and
is associated with the giant galaxy VCC873 (NGC 4402). It has a higher
luminosity, star formation rate and metallicity than the extragalactic HII
region recently discovered near the Virgo galaxy VCC836 by Gerhard et al.
(2002).


title:
Comparative study of the two large flares from SGR1900+14 with the
  BeppoSAX Gamma-Ray Burst Monitor

abstract:
  We report on spectral and temporal results of the 40-700 keV observations,
obtained with the Gamma-Ray Burst Monitor (GRBM) on board BeppoSAX, of the two
large flares from the Soft Gamma-ray Repeater SGR1900+14 occurred on August 27,
1998 and April 18, 2001. From their intensity, fluence and duration, the first
one was classified as "giant" and the second as "intermediate". The spectral
results have been obtained with an improved response function of the GRBM. We
find that the two events have similar spectral properties, but different
temporal properties. The major difference concerns the time profiles of the
light curves, whereas the lack of evidence in the 2001 flare for the erratic
time variability found at high frequencies (10-1000 Hz) in the 1998 flare could
be ascribed to lower counting statistics. We discuss these results in the light
of the magnetar model proposed for SGR sources.


title:
AstroCat/CVcat: A catalogue on Cataclysmic Variables based on a new
  framework for online interactive astronomical databases

abstract:
  We report on the progress of the development of CVcat, an interactive
catalogue on Cataclysmic Variables, which is the first application based on
AstroCat, a general framework for the installation and maintenance of web-based
interactive astronomical databases. Registered users can contribute directly to
the catalogue content by adding new objects, object properties, literature
references, and annotations. The scientific quality control of the catalogue is
carried out by a distributed editorial team. Searches in CVcat can be performed
by object name, classification, certain properties or property ranges, and
coordinates. Search results can be retrieved in several output formats,
including XML. Old database states can be restored in order to ensure the
citability of the catalogue. Furthermore, CVcat is designed to serve as a
repository for reduced data from publications. Future prospects include the
integration of AstroCat-based catalogues in the international network of
Virtual Observatories.


title:
Photometric redshifts with the Multilayer Perceptron Neural Network:
  application to the HDF-S and SDSS

abstract:
  We present a technique for the estimation of photometric redshifts based on
feed-forward neural networks. The Multilayer Perceptron (MLP) Artificial Neural
Network is used to predict photometric redshifts in the HDF-S from an ultra
deep multicolor catalog. Various possible approaches for the training of the
neural network are explored, including the deepest and most complete
spectroscopic redshift catalog currently available (the Hubble Deep Field North
dataset) and models of the spectral energy distribution of galaxies available
in the literature. The MLP can be trained on observed data, theoretical data
and mixed samples. The prediction of the method is tested on the spectroscopic
sample in the HDF-S (44 galaxies). Over the entire redshift range, $0.1<z<3.5$,
the agreement between the photometric and spectroscopic redshifts in the HDF-S
is good: the training on mixed data produces sigma_z(test) ~ 0.11, showing that
model libraries together with observed data provide a sufficiently complete
description of the galaxy population. The neural system capability is also
tested in a low redshift regime, 0<z<0.4, using the Sloan Digital Sky Survey
Data Release One (DR1) spectroscopic sample. The resulting accuracy on 88108
galaxies is sigma_z(test) ~ 0.022. Inputs other than galaxy colors - such as
morphology, angular size and surface brightness - may be easily incorporated in
the neural network technique. An important feature, in view of the application
of the technique to large databases, is the computational speed: in the
evaluation phase, redshifts of 10^5 galaxies are estimated in few seconds.


title:
Intermediate scale structure of the interstellar medium towards NGC 6231
  in Sco OB1 with FUSE

abstract:
  The FUSE far-ultraviolet interstellar spectra toward seven targets in NGC
6231 show that the molecules H_2, HD, and CO as well as various atomic species
are distributed in several clouds. The main absorption component found on the
sight lines lies in the Lupus cloud region at a distance of about 150 pc, and
there is a weaker second one, presumably in the Sco OB1 shell surrounding NGC
6231 (d~1.8 kpc). H_2 excitation modelling is used to constrain the radiation
field and the density in the gas; HD is used to estimate the abundance of H+.
The small angular separation of the target stars allows column density
variations to be probed over the field of view, on scales of 0.05 pc in the
case of the Lupus cloud distance. They are 40% for H_2 and 60% for H I. A
rather strong radiation field inside the molecular clouds suggests a separation
of the gas into smaller cloudlets also along the line of sight.


title: A Multi-Year Photometric Study of IC 348

abstract:
  The extremely young cluster IC 348 has been monitored photometrically over 5
observing seasons from Dec 1998 to March 2003 in Cousins I with a 0.6 m
telescope at Van Vleck Observatory. Twenty-eight periodic variables and 16
irregular variables have been identified. Among the brighter stars, 14 of the
16 known K or M-type WTTS were found to be periodic variables, while all 5 of
the known CTTS were found to be irregular variables. In the full sample, which
includes 150 stars with I mag as faint as 18, we find that 40% of the 63 WTTS
are detected as variables, nearly all of them periodic, while 55% of the 20
CTTS are also detected as variable, with none of them periodic. Our study
suggests that 80-90% of all WTTS in young clusters will be detected as periodic
variables given sufficiently precise and extended monitoring, whereas CTTS will
reveal themselves primarily or solely as irregular variables. This has clear
consequences for PMS rotational studies based on photometric periods. We
examine the stability of the periodic light curves from season to season. All
periodic stars show modulations of their amplitude, mean brightness and light
curve shape on time scales of less than 1 yr, presumably due to changes in spot
configurations and/or physical characteristics. In no case, however, can we
find definitive evidence of a change in period, indicating that differential
rotation is probably much less on WTTS than it is on the Sun. Among the
non-periodic stars, we report the detection of two possible UXors as well as a
pre-main sequence star, HMW 15, which apparently undergoes an eclipse with a
duration exceeding three years.


title: Physical Conditions in the Narrow-Line Region of M51

abstract:
  We have investigated the physical conditions in the narrow-line region (NLR)
of M51 using long-slit spectra obtained with the Space Telescope Imaging
Spectrograph (STIS) aboard the Hubble Space Telescope (HST) and 3.6 cm radio
continuum observations obtained with the Very Large Array (VLA). Emission-line
diagnostics were employed for nine NLR clouds, which extend 2.5" (102 pc) from
the nucleus, to examine the electron density, temperature, and ionization state
of the NLR gas. The emission-line ratios are consistent with those typically
found in Seyfert nuclei and indicate that within the inner near-nuclear region
(r ~< 1") the ionization decreases with increasing radius. Upper-limits to the
[O III] electron temperature (T ~< 11,000 K) for the inner NLR clouds indicate
that photoionization is the dominant ionization mechanism close to the nucleus.
The emission-line fluxes for most of the NLR clouds can be reproduced
reasonably well by simple photoionization models using a central power-law
continuum source and supersolar nitrogen abundances. Shock+precursor models,
however, provide a better fit to the observed fluxes of an NLR cloud ~2.5"
south of the nucleus that is identified with the extra-nuclear cloud (XNC). The
large [O III] electron temperature of this cloud (T = 24,000 K) further
suggests the presence of shocks. This cloud is straddled by two radio knots and
lies near the location where a weak radio jet, ~2.5" (102pc) in extent,
connects the near-nuclear radio emission with a diffuse lobe structure spanning
\~4" (163 pc). It is plausible that this cloud represents the location where
the radio jet impinges on the disk ISM.


title: Modeling of Alpha Cen and Procyon using VLTI observations

abstract:
  We present a novel approach to model the nearby stars Alpha Cen A & B and
Procyon A using asteroseismic and interferometric constraints. Using the VINCI
instrument installed at the VLT Interferometer (VLTI), the angular diameters of
the Alpha Centauri system were measured with a relative precision of 0.2% and
0.6%, respectively. From these values, we derive linear radii of R[A] = 1.224
+/- 0.003 R_sun and R[B] = 0.863 +/- 0.005 R_sun. These radii are in excellent
agreement with the models of Thevenin et al. (2002), that use asteroseismic
frequencies as constraints (Bouchy & Carrier 2001; Bouchy & Carrier 2002). With
the same instrument, we also measured the angular diameter of Procyon A. Using
the Hipparcos parallax, we obtain a linear radius of 2.048 +/- 0.025 R_sun. We
use this result together with spectroscopic and photometric constraints to
model this star with the CESAM code. We also computed the adiabatic oscillation
spectrum of our model of Procyon A, giving a mean large frequency separation of
Delta nu_0 = 54.8 uHz, in agreement with the seismic observations by Martic et
al. (2001). Our model favours a mass around 1.4 M_sun for Procyon A.


title:
Star-Forming Galaxies in the Sloan Digital Sky Survey -- The View from
  Pittsburgh

abstract:
  We used data from the Data Release 1 (DR1) of the Sloan Digital Sky Survey
(SDSS) in order to define a catalog of about 13,000 star-forming galaxies
(SFG). We discuss the results of two projects. First, we matched our catalog
against the ROSAT All-Sky Survey (RASS) and catalogs of pointed ROSAT
observations. We identify eight X-ray emitting star-forming galaxies; four were
known previously, e.g., the famous "most metal-poor" dwarf galaxy I Zw 18, but
another four are new identifications. The data confirm the calibration of X-ray
luminosity to a star-formation rate (SFR) by Ranalli et al. (2003), and are
used to derive SFRs for these SDSS SFGs. We also suggest two new candidate
galaxy clusters. Second, after carefully eliminating all cases of "shredded"
SFGs, we derive total absolute blue magnitudes and ionized gas metallicities
(O/H ratios). We discuss the luminosity-metallicity (L-Z) relation for galaxies
of different physical size (compact, small and large depending on Petrosian
half-light radius, R$_e$). We report the discovery of evolution in the L-Z
relation for the redshift range from 0 to 0.3, in the sense that galaxies at
higher redshifts tend to have lower O/H ratios at a given luminosity. This
evolution is strongest for large galaxies, and weakest for compact galaxies.


title: On the galactic chemical evolution of sulfur

abstract:
  Sulfur abundances have been determined for ten stars to resolve a debate in
the literature on the Galactic chemical evolution of sulfur in the halo phase
of the Milky Way. Our analysis is based on observations of the S I lines at
9212.9, 9228.1, and 9237.5 A for stars for which the S abundance was obtained
previously from much weaker S I lines at 8694.0 and 8694.6 A. In contrast to
the previous results showing [S/Fe] to rise steadily with decreasing [Fe/H],
our results show that [S/Fe] is approximately constant for metal-poor stars
([Fe/H] < -1) at [S/Fe] = +0.3. Thus, sulfur behaves in a similar way to the
other alpha elements, with an approximately constant [S/Fe] for metallicities
lower than [Fe/H] = -1. We suggest that the reason for the earlier claims of a
rise of [S/Fe] is partly due to the use of the weak S I 8694.0 and 8694.6 A
lines and partly uncertainties in the determination of the metallicity when
using Fe I lines. The S I 9212.9, 9228.1, and 9237.5 A lines are preferred for
an abundance analysis of sulfur for metal-poor stars.


title:
An increased estimate of the merger rate of double neutron stars from
  observations of a highly relativistic system

abstract:
  The merger of close binary systems containing two neutron stars should
produce a burst of gravitational waves, as predicted by the theory of general
relativity. A reliable estimate of the double-neutron-star merger rate in the
Galaxy is crucial in order to predict whether current gravity wave detectors
will be successful in detecting such bursts. Present estimates of this rate are
rather low, because we know of only a few double-neutron-star binaries with
merger times less than the age of the Universe. Here we report the discovery of
a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic
double-neutron-star binary with an orbital period of 2.4 hours. This system
will merge in about 85 Myr, a time much shorter than for any other known
neutron-star binary. Together with the relatively low radio luminosity of PSR
J0737-3039, this timescale implies an order-of-magnitude increase in the
predicted merger rate for double-neutron-star systems in our Galaxy (and in the
rest of the Universe).


title: (Lack of) lensing constraints on cluster dark matter profiles

abstract:
  Using stellar dynamics and strong gravitational lensing as complementary
probes, Sand et al. (2002, 2003) have recently claimed strong evidence for
shallow dark matter density profiles in several lensing clusters, which may
conflict with predictions of the Cold Dark Matter paradigm. However, systematic
uncertainties in the analysis weaken the constraints. By re-analyzing their
data, we argue that the tight constraints claimed by Sand et al., were driven
by prior assumptions. Relaxing the assumptions, we find that no strong
constraints may be derived on the dark matter inner profile from the Sand et
al. data; we find satisfactory fits (with reasonable parameters) for a wide
range of inner slopes 0 < beta < 1.4. Useful constraints on the mass
distributions of lensing clusters can still be obtained, but they require
moving beyond mere measurements of lensing critical radii into the realm of
detailed lens modeling.


title:
Automated Determination of Stellar Population Parameters in Galaxies
  Using Active Instance-based Learning

abstract:
  In this work we focus on the determination of the relative distributions of
young, intermediate-age and old populations of stars in galaxies. Starting from
a grid of theoretical population synthesis models we constructed a set of model
galaxies with a distribution of ages, metallicities and intrinsic reddening.
Using this set we have explored a new fitting method that presents several
advantages over conventional methods. We propose an optimization technique that
combines active learning with an instance-based machine learning algorithm.
Experimental results show that this method can estimate with high speed and
accuracy the physical parameters of the stellar populations.


title:
Spectroscopy of the Millennium Outburst and Recent Variability of the
  Yellow Hypergiant Rho Cassiopeiae

abstract:
  In the summer and fall of 2000 the yellow hypergiant Rho Cassiopeiae dimmed
by more than a visual magnitude, while its effective temperature decreased from
\~7000 K to below 4000 K over ~200 d. We observed the highest mass-loss rate of
  ~5 % of the solar mass per year in a single stellar eruption so far (Lobel et
al. 2003, ApJ, 583, 923). We determine from newly formed TiO bands a gas
mass-loss rate of M_dot ~ 5.4 10^{-2} Msun/yr, which is of the same order of
magnitude as has been proposed for the giant outbursts of the Luminous Blue
Variable Eta Carinae. Over the past two years since the outburst event we
observe a very prominent inverse P Cygni profile in Balmer H alpha. Strong
Halpha emission has not before been observed in the hypergiant over this long
period of time, signaling an unusual strong collapse of the upper hydrogen
atmosphere, which we also observed in the months before the 2000 outburst.
Since the brightness decrease of March 2003 we observe a transformation of the
H alpha profile into a P Cygni profile, signaling a strong expansion of Rho
Cas's upper atmosphere, which could possibly result in a new outburst event.
High-resolution spectroscopic observations reveal that the lower photosphere
rapidly expanded until May-June 2003. Very recent high-resolution observations
of September 2003 show however that the photospheric absorption lines did not
shift far blueward as observed in July 2000 before the strong brightness
decrease of the outburst. The Fe I 5572 A is redshifted, signaling the collapse
of the lower photosphere. A new strong brightness decrease by more than a
magnitude in V for the fall and winter of 2003 is therefore not expected.


title: The Ages of Dwarf Ellipticals

abstract:
  We present narrow band photometry of 91 dwarf ellipticals in the Coma and
Fornax clusters taken through the Stromgren (uvby) filter system. Dividing the
sample by dwarf morphology into nucleated (dEN) and non-nucleated (dE) dwarfs
reveals two distinct populations of early-type systems based on integrated
colors. The class of dEN galaxies are redder in their continuum colors as
compared to bright cluster ellipticals and dE type dwarfs, and their position
in multi-color diagrams can only be explained by an older mean age for their
underlying stellar populations. By comparison with the narrow band photometry
of the M87 globular cluster system (Jordan et al. 2002), we find that dENs are
a higher metallicity continuation of the old, metal-poor color sequence of
galactic globulars and the blue population of M87 globulars. Bright ellipticals
and dE dwarfs, on the other hand, follow the color sequence of the metal-rich,
red population of M87 globulars. A comparison to SED models, convolved to a
simple metallicity model, finds that dENs and blue globulars are 3 to 4 Gyrs
older than cluster ellipticals and 5 Gyrs older than dE type galaxies. The
implication is that globulars and dEN galaxies are primordial and have
metallicities set by external constraints such as the enrichment of their
formation clouds. Bright ellipticals and dE galaxies have metallicities and
ages that suggest an extended phase of initial star formation to produce a
younger mean age, even if their formation epoch is similar to that of dENs and
blue globulars, and an internally driven chemical evolutionary history.


title: Spatially Resolved STIS Spectroscopy of Betelgeuse's Outer Atmosphere

abstract:
  We present spatially resolved spectra observed with HST-STIS of the upper
chromosphere and dust envelope of Alpha Orionis (M2 Iab). In the fall of 2002 a
set of five high-resolution near-UV spectra was obtained by scanning at
intensity peak-up position and four off-limb target positions up to one
arcsecond, using a small aperture, to investigate the thermal conditions and
flow dynamics in the outer atmosphere of this important nearby cool supergiant
star. Based on Mg II h & k, Fe II 2716 A, C II 2327 A, and Al II ] 2669 A
emission lines we provide the first evidence for the presence of warm
chromospheric plasma at least 1 arcsecond away from the star at ~40 R* (1
R*~700 Rsun). The STIS spectra reveal that Betelgeuse's upper chromosphere
extends far beyond the circumstellar H alpha envelope of ~5 R*, determined from
previous ground-based imaging. The flux in the broad and self-absorbed
resonance lines of Mg II decreases by a factor of ~700 compared to the flux at
chromospheric disk center. We observe strong asymmetry changes in the Mg II h
and Si I resonance line profiles when scanning off-limb, signaling the outward
acceleration of gas outflow in the upper chromosphere. From the radial
intensity distributions of Fe I and Fe II emission lines we determine the
radial non-LTE iron ionization balance. We compute that the local kinetic gas
temperatures of the warm chromospheric gas component in the outer atmosphere
exceed 2600 K, when assuming local gas densities of the cool gas component we
determine from radiative transfer models that fit the 9.7 um silicate dust
emission feature. The spatially resolved STIS spectra directly demonstrate that
warm chromospheric plasma co-exisists with cool gas in Betelgeuse's
circumstellar dust envelope.


title: Lithium abundance/surface activity connections in solar-type Pleiads

abstract:
  The relation between the lithium abundance, A_Li, and photospheric activity
of solar-type Pleiads is investigated for the first time via acquisition and
analysis of B and V-band data. Predictions of activity levels of target stars
were made according to the A_Li/(B-V) relation and then compared with new CCD
photometric measurements. Six sources behaved according to the predictions
while one star (HII 676), with low predicted activity, exhibited the largest
variability of the study; another star (HII 3197), with high predicted
activity, was surprisingly quiet. Two stars displayed non-periodic fadings,
this being symptomatic of orbiting disk-like structures with irregular density
distributions. Although the observation windows were not ideal for rotational
period detection, some periodograms provided possible values; the light-curve
obtained for HII 1532 is consistent with that previously recorded.


title:
Propagation of Extremely-high Energy Leptons in the Earth: Implications
  to their detection by the IceCube Neutrino Telescope

abstract:
  We present the results of numerical calculations on propagation of
Extremely-high energy (EHE) neutrinos and charged leptons in the earth for
trajectories in all phase space of nadir angles. Our comprehensive calculation
has shown that not only the secondary produced muons but also taus survive
without decaying in energy range of 10PeV-100PeV with intensity approximately
three orders of magnitude lower than the neutrino flux regardless of EHE
neutrino production models. They form detectable horizontal or downgoing events
in a 1km$^3$ underground neutrino telescope such as the IceCube detector. The
event rate and the resultant detectability of EHE signals in comparison with
the atmospheric muon background are also evaluated. The 90 % C.L. upperlimit of
EHE neutrino fluxes by a km$^2$ detection area would be placed at $E^2dF/dE
\simeq 3.7\times 10^{-8}$ GeV/cm$^2$ sec sr for $\nu_{\mu}$ and $4.6\times
10^{-8}$ for $\nu_{\tau}$ with energies of $10^9$ GeV in absence of signals
with energy-loss in a detection volume of 10PeV or greater.


title:
Variable stars in the Magellanic Clouds: II. The data and infrared
  properties

abstract:
  The data of 8,852 and 2,927 variable stars detected by OGLE survey in the
Large and Small Magellanic Clouds are presented. They are cross-identified with
the SIRIUS JHK survey data, and their infrared properties are discussed.
Variable red giants are well separated on the period-J - K plane, suggesting
that it could be a good tool to distinguish their pulsation mode and type.


title:
Detection of Gravitational Waves from the Coalescence of Population-III
  Remnants with Advanced LIGO

abstract:
  The comoving mass density of massive black hole (MBH) remnants from
pre-galactic star formation could have been similar in magnitude to the
mass-density of supermassive black holes (SMBHs) in the present-day universe.
We show that the fraction of MBHs that coalesce during the assembly of SMBHs
can be extracted from the rate of ring-down gravitational waves that are
detectable by Advanced LIGO. Based on the SMBH formation history inferred from
the evolution of the quasar luminosity function, we show that an observed event
rate of 1 per year will constrain the SMBH mass fraction that was contributed
by MBHs coalescence down to a level of ~10^-6 for 20 solar mass MBH remnants
(or ~10^-4 for 260 solar mass remnants).


title: Pulsar Radio Emission Altitude from Curvature Radiation

abstract:
  We assume that the relativistic sources moving along the dipolar magnetic
field lines emit curvature radiation. The beamed emission occurs in the
direction of tangents to the field lines, and to receive it, the sight line
must align with the tangent within the beaming angle 1/gamma, where gamma is
the particle Lorentz factor. By solving the viewing geometry in an inclined and
rotating dipole magnetic field, we show that, at any given pulse phase,
observer tends to receive radiation only from the specific heights allowed by
the geometry. We find outer conal components are emitted at higher altitudes
compared to inner components including the core. At any pulse phase, low
frequency emission comes from higher altitudes than high frequency emission. We
have modeled the emission heights of pulse components of PSR B0329+54, and
estimated field line curvature radii and particle Lorentz factors in the
emission regions.


title:
Stationary perturbation configurations in a composite system of stellar
  and coplanarly magnetized gaseous singular isothermal discs

abstract:
  We construct aligned and unaligned stationary perturbation configurations in
a composite system of stellar and coplanarly magnetized gaseous singular
isothermal discs (SIDs) coupled by gravity. In comparison with SID problems
studied earlier, there exist three possible classes of stationary solutions
allowed by more dynamic freedoms. Our exact global perturbation solutions and
critical points are valuable for testing numerical magnetohydrodynamic codes.
For galactic applications, our model analysis contains more realistic elements
and offer useful insights for structures and dynamics of disc galaxies
consisting of stars and magnetized gas.


title:
Survey for Transiting Extrasolar Planets in Stellar Systems: I.
  Fundamental Parameters of the Open Cluster NGC 1245

abstract:
  We derive fundamental parameters for the old, rich open cluster NGC 1245
using BVI photometry from the MDM 1.3m and 2.4m telescopes. Based on detailed
isochrone fitting, we find NGC 1245 has a slightly sub-solar metallicity,
[Fe/H]=-0.05 +- 0.03 (statistical) +- 0.08 (systematic), and an age of 1.04 +-
0.02 +- 0.09 Gyr. In contrast to previous studies, we find no evidence for
significant differential reddening. We determine an extinction of A_V=0.68 +-
0.02 +- 0.09 mag and a distance modulus of (m-M)o=12.27 +- 0.02 +- 0.12 mag,
which corresponds to a distance of 2.8 +- 0.2 Kpc. We derive a logarithmic
mass-function slope for the cluster of a=-3.12 +- 0.27, where a Salpeter slope
is a=-1.35. Fits to the radial surface-density profile yield a core radius of
r_c=3.10 +- 0.52 arcmin (2.57 +- 0.47 pc). NGC 1245 is highly relaxed and
contains a strongly mass segregated population. The mass function for the inner
cluster has a very shallow slope, b=-0.56 +- 0.28. In contrast, the outer
periphery of the cluster is enriched with low mass members and devoid of high
mass members out to the tidal radius, r_t=20 arcmin (16.5 pc). Based on the
observed surface-density profile and an extrapolated mass function, we derive a
total cluster mass, M=1300 +- 90 +- 170 M_(solar).


title: Volume Filling Factors of the DIG

abstract:
  Combining dispersion measures, distances and emission measures for 157
pulsars lying above \mid b \mid > 5 degree and between 60 degree < l < 360
degree we find the mean volume filling factor (\bar{f_v}) of the diffused
ionized gas in the Milky Way. This filling factor is inversely related to the
mean electron density (\bar{n_c}) in the clouds, \bar{f_v} = (0.0184 +/-
0.0014) \bar{n_c}^{-1.07 +/- 0.03}, implying a nearly constant average electron
density distribution within 3 kpc of the sun.


title: An unusual high-ionization nebula in NGC55

abstract:
  We report on the detection of a previously unknown extended low-density
nebula of very high temperature and excitation, TR001507.7-391206, located
above the midplane of NGC55. The nebular emission line spectrum, in which HeII
is present, is consistent with photoionization by about 3 very hot massive O3
or WR-type stars. There are no indications for shock ionization. The faint blue
optical continuum and XMM-Newton EPIC-pn and OM-data also support our
assumption that this nebula is not a supernova remnant. Galactic nebulae
harboring massive Wolf-Rayet (WR) stars may be appropriate examples, in
particular the highly ionized nebula G2.4+1.4 around WR 102 (aka Sk4 or
LSS4368). The relatively large diameter of the inhomogeneously expanding nebula
in NGC55 of about 58pc, compared to 11pc of G2.4+1.4, would also be consistent
with the number of ionizing stars.


title:
Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy
  Formation Come to an End?

abstract:
  Models of structure formation based on cold dark matter predict that most of
the small dark matter haloes that first formed at high redshift would have
merged into larger systems by the present epoch. Substructure in present-day
haloes preserves the remains of these ancient systems, providing the only
direct information we may ever have about the low-mass end of the power
spectrum. I describe some recent attempts to model halo substructure down to
very small masses, using a semi-analytic model of halo formation. I make a
preliminary comparison between the model predictions, observations of
substructure in lensed systems, and the properties of local satellite galaxies.


title:
VLT/NACO infrared adaptive optics images of small scale structures in
  OMC1

abstract:
  Near-infrared observations of line emission from excited H2 and in the
continuum are reported in the direction of the Orion molecular cloud OMC1,
using the European Southern Observatory Very Large Telescope UT4, equipped with
the NAOS adaptive optics system and the CONICA infrared array camera. Spatial
resolution has been achieved at close to the diffraction limit of the telescope
(0.08" - 0.12") and images show a wealth of morphological detail. Structure is
not fractal but shows two preferred scale sizes of 2.4" (1100 AU) and 1.2" (540
AU), where the larger scale may be associated with star formation.


title:
Resonance analysis of $^{147}$Sm(n,alpha) cross sections: Comparison to
  optical model calculations and indications of non-statistical effects

abstract:
  We have measured the $^{147}$Sm(\textit{n},$\alpha $) cross section from 3 eV
to 500 keV and performed an $\mathcal{R}$-matrix analysis in the resolved
region ($E_{n}$$<$ 700 eV) to extract $\alpha $ widths for 104 resonances. We
computed strength functions from these resonance parameters and compared them
to transmission coefficients calculated using optical model potentials similar
to those employed as inputs to statistical model calculations. The statistical
model often is used to predict cross sections and astrophysical reaction rates.
Comparing resonance parameters rather than cross sections allows more direct
tests of potentials used in the model and hence should offer greater insight
into possible improvements. In particular, an improved $\alpha $+nucleus
potential is needed for applications in nuclear astrophysics. In addition to
providing a more direct test of the $\alpha $% +nucleus potential, the $\alpha
$-width distributions show indications of non-statistical effects.


title: The polarization evolution of the optical afterglow of GRB 030329

abstract:
  We report 31 polarimetric observations of the afterglow of GRB 030329 with
high signal-to-noise and high sampling frequency. The data imply that the
afterglow magnetic field has small coherence length and is mostly random,
probably generated by turbulence.


title:
Ultra-Relativistic Magneto-Hydro-Dynamic Jets in the context of Gamma
  Ray Bursts

abstract:
  We present a detailed numerical study of the dynamics and evolution of
ultrarelativistic magnetohydrodynamic jets in the black hole-disk system under
extreme magnetization conditions. We find that Lorentz factors of up to 3000
are achieved and derived a modifiedMichel scaling (Gamma ~ sigma) which allows
for a wide variation in the flow Lorentz factor. Pending contamination induced
by mass-entrainment, the linear Michel scaling links modulations in the
ultrarelativistic wind to variations in mass accretion in the disk for a given
magnetization. The jet is asymptotically dominated by the toroidal magnetic
field allowing for efficient collimation. We discuss our solutions (jets) in
the context of Gamma ray bursts and describe the relevant features such as the
high variability in the Lorentz factor and how high collimation angles (~ 0-5
degrees), or cylindrical jets, can be achieved. We isolate a jet instability
mechanism we refer to as the "bottle-neck" instability which essentially relies
on a high magnetization and a recollimation of the magnetic flux surfaces. The
instability occurs at large radii where any dissipation of the magnetic energy
into radiation would in principle result in an optically thin emission.


title: Hints for a fast precessing relativistic radio jet in LS I +61 303

abstract:
  Here we discuss two consecutive MERLIN observations of the X-ray binary LS I
+61 303. The first observation shows a double-sided jet extending up to about
200 AU on both sides of a central source. The jet shows a bent S-shaped
structure similar to the one displayed by the well-known precessing jet of SS
433. The precession suggested in the first MERLIN image becomes evident in the
second one, showing a one-sided bent jet significantly rotated with respect to
the jet of the day before. We conclude that the derived precession of the
relativistic (beta=0.6) jet explains puzzling previous VLBI results. Moreover,
the fact that the precession is fast could be the explanation of the never
understood short term (days) variability of the associated gamma-ray source 2CG
135+01 / 3EG J0241+6103.


title:
The Cellular Burning Regime in Type Ia Supernova Explosions - I. Flame
  Propagation into Quiescent Fuel

abstract:
  We present a numerical investigation of the cellular burning regime in Type
Ia supernova explosions. This regime holds at small scales (i.e. below the
Gibson scale), which are unresolved in large-scale Type Ia supernova
simulations. The fundamental effects that dominate the flame evolution here are
the Landau-Darrieus instability and its nonlinear stabilization, leading to a
stabilization of the flame in a cellular shape. The flame propagation into
quiescent fuel is investigated addressing the dependence of the simulation
results on the specific parameters of the numerical setup. Furthermore, we
investigate the flame stability at a range of fuel densities. This is directly
connected to the questions of active turbulent combustion (a mechanism of flame
destabilization and subsequent self-turbulization) and a
deflagration-to-detonation transition of the flame. In our simulations we find
no substantial destabilization of the flame when propagating into quiescent
fuels of densities down to ~10^7 g/cm^3, corroborating fundamental assumptions
of large-scale SN Ia explosion models. For these models, however, we suggest an
increased lower cutoff for the flame propagation velocity to take the cellular
burning regime into account.


title: Non-linear electrodynamics and the acceleration of the universe

abstract:
  It is shown that the addition of a non-linear term to the Lagrangian of the
electromagnetic field yields a fluid with an asymptotically super-negative
equation of state, causing an accelerated expansion of the universe. Some
general properties of nonlinear electromagnetism in cosmology are also
discussed.


title:
Hot Very Small dust Grains in NGC 1068 seen in jet induced structures
  thanks to VLT/NACO adaptive optics

abstract:
  We present K, L and M diffraction-limited images of NGC 1068 obtained with
NAOS+CONICA at VLT/YEPUN over a 3.5" field around the central engine. Hot dust
(Tcol = 550-650 K) is found in three different regions : (a) in the true
nucleus, seen as a slightly NS elongated, core of extremely hot dust,
"resolved" in K and L with respective diameters of ~5 pc and 8.5 pc ; (b) along
the NS direction, as a "spiral arm" and a southern tongue ; (c) as a set of
parallel elongated nodules ("wave-like") bracketting the jet. Several
structures observed on radio maps, mid-IR or HST UV-visible maps are seen, so
that a precise registration can be done from UV to 6 cm. These results do
support the current interpretion that source (a) corresponds to emission from
dust near sublimation temperature delimiting the walls of the cavity in the
central obscuring torus. Structure (b) is thought to be a mixture of hot dust
and active star forming regions along a micro spiral structure that could trace
the tidal mechanism bringing matter to the central engine. Structure c)which
was not known, exhibits too high a temperature for "classical'' grains ; it is
most probably the signature of transiently heated very small dust grains (VSG)
: "nano-diamonds", which are resistant and can form in strong UV field or in
shocks, are very attractive candidates. The "waves'' can be condensations
triggered by jet induced shocks, as predicted by recent models. First
estimates, based on a simple VSG model and on a detailed radiative transfer
model, do agree with those interpretations, both qualitatively and
quantitatively.


title:
Cloud Structure and Physical Conditions in Star-forming Regions from
  Optical Observations. I. Data and Component Structure

abstract:
  We present high-resolution optical spectra (at ~0.6--1.8 km s-1) of
interstellar CN, CH, CH^+, \ion{Ca}{1}, \ion{K}{1}, and \ion{Ca}{2} absorption
toward 29 lines of sight in three star-forming regions, \rho Oph, Cep OB2, and
Cep OB3. The observations and data reduction are described. The agreement
between earlier measurements of the total equivalent widths and our results is
quite good. However, our higher resolution spectra reveal complex structure and
closely blended components in most lines of sight. The velocity component
structure of each species is obtained by analyzing the spectra of the six
species for a given sight line together. The tabulated column densities and
Doppler parameters of individual components are determined by using the method
of profile fitting. Total column densities along lines of sight are computed by
summing results from profile fitting for individual components and are compared
with column densities from the apparent optical depth method. A more detailed
analysis of these data and their implications will be presented in a companion
paper.


title: Variations in the spin period of the radio-quiet pulsar 1E 1207.4-5209

abstract:
  The X-ray source 1E 1207.4-5209 is a compact central object in the
G296.5+10.0 supernova remnant. Its spin period of 424 ms, discovered with the
Chandra X-ray Observatory, suggests that it is a neutron star. The X-ray
spectrum of this radio-quiet pulsar shows at least two absorption lines, first
spectral features discovered in radiation from an isolated neutron star. Here
we report the results of timing analysis of Chandra and XMM-Newton observations
of this source showing a non-monotonous behavior of its period. We discuss
three hypotheses which may explain the observational result. The first one
assumes that 1E 1207.$-5209 is a glitching pulsar, with frequency jumps of
\Delta f > 5 \muHz occurring every 1-2 years. The second hypothesis explains
the deviations from a steady spin-down as due to accretion, with accretion rate
varying from \sim 10^{13} to >10^{16} g s^{-1}, from a disk possibly formed
from ejecta produced in the supernova explosion. Finally, the period variations
could be explained assuming that the pulsar is in a wide binary system with a
long period, P_orb \sim 0.2-6 yr, and a low-mass companion, M_2 < 0.3 M_\odot.


title: The TESIS project: revealing massive early-type galaxies at z>1

abstract:
  We present the preliminary results of an on-going near-IR low resolution
spectroscopic follow-up of a complete sample of 30 bright (K'<18.5) EROs
selected over 360 arcmin^2 from the MUNICH survey. Among the 13 EROs observed
so far, 7 turned out to be early-type galaxies at 1.2<z<1.45 with stellar
masses in excess of 2x10^11 M\odot. These 7 early-types account for 40% of the
local population of bright ellipticals providing a lower limit to the density
of massive early-types at z>1.


title: The TESIS project: Are type 2 QSO hidden in X-ray emitting EROs?

abstract:
  Here we present the results obtained from the analysis of 75 ksec of
XMM-Newton observations of a sample of EROs selected from one MUNICS field
(K'<19.5 mag). We find 6 EROs with a X-ray counterpart down to a 2--10 keV flux
limit of ~10^{-15} cgs. For all of them the X-ray--to--optical flux ratios and
the 2--10 keV luminosities suggest the presence of AGN. In particular, a
complete X-ray spectral analysis shows that high luminosity, obscured AGNs
(i.e. QSO2 candidates) are present in 3 of them.


title: Molecular Gas in the Lensed Lyman Break Galaxy cB58

abstract:
  We have used the IRAM Plateau de Bure Interferometer to map CO(3-2) emission
from the gravitationally lensed Lyman break galaxy MS1512-cB58. This is the
first detection of a molecular emission line in any Lyman break system; its
integrated intensity implies a total molecular gas mass of 6.6e9 Msun, while
its width implies a dynamical mass of 1.0e10 csc^2i Msun (for a flat Lambda=0.7
cosmology). These estimates are in excellent concordance with nearly all
parameters of the system measured at other wavelengths, and yield a consistent
picture of past and future star formation with no obvious discrepancies
requiring explanation by differential lensing. In particular, we find that the
age and remaining lifetime of the current episode of star formation are likely
to be similar; the surface densities of star formation and molecular gas mass
are related by a Schmidt law; and the fraction of baryonic mass already
converted into stars is sufficient to account for the observed enrichment of
the interstellar medium to 0.4 Zsun. Barring substantial gas inflow or a major
merger, the stars forming in the current episode will have mass and coevality
at z=0 similar to those of a spiral bulge. Assuming cB58 is a typical Lyman
break galaxy apart from its magnification, its global parameters suggest that
the prescriptions for star formation used in some semi-analytic models of
galaxy evolution require moderate revision, although the general prediction
that gas mass fraction should increase with redshift is validated. [abridged]


title: The Star Formation History of the Small Magellanic Cloud

abstract:
  We present the spatially-resolved star formation and chemical enrichment
history of the Small Magellanic Cloud (SMC) across the entire central $4-degree
x 4.5-degree area of the main body, based on UBVI photometry from our
Magellanic Clouds Photometric Survey. We find that 1) approximately 50% of the
stars that ever formed in the SMC formed prior to 8.4 Gyr ago (z >1.2 for WMAP
cosmology), 2) the SMC formed relatively few stars between 8.4 and 3 Gyr ago,
3) there was a rise in the mean star formation rate during the most recent 3
Gyr punctuated by "bursts" at ages of 2.5, 0.4, and 0.06 Gyr, 4) the bursts at
2.5 and 0.4 Gyr are temporally coincident with past perigalactic passages of
the SMC with the Milky Way, 5) there is preliminary evidence for a large-scale
annular structure in the 2.5 Gyr burst, and 6) the chemical enrichment history
derived from our analysis is in agreement with the age-metallicity relation of
the SMC's star clusters. Consistent interpretation of the data required an ad
hoc correction of 0.1-0.2 mag to the B-V colors of 25% of the stars; the cause
of this anomaly is unknown, but we show that it does not strongly influence our
results.


title: The Cosmic Coalescence Rates for Double Neutron Star Binaries

abstract:
  This manuscript is an updated version of Kalogera et al. (2004) published in
ApJ Letters to correct our calculation of the Galactic DNS in-spiral rate. The
details of the original erratum submitted to ApJ Letters are given in page 6 of
this manuscript.
  We report on the newly increased event rates due to the recent discovery of
the highly relativistic binary pulsar J0737--3039 (Burgay et al. 2003). Using a
rigorous statistical method, we present the calculations reported by Burgay et
al., which produce a in-spiral rate for Galactic double neutron star (DNS)
systems that is higher by a factor of 5-7 compared to estimates made prior to
the new discovery. Our method takes into account known pulsar-survey selection
effects and biases due to small-number statistics. This rate increase has
dramatic implications for gravitational wave detectors. For the initial Laser
Interferometer Gravitational-Wave Observatory (LIGO) detectors, the most
probable detection rates for DNS in-spirals are one event per 10-630 yr; at 95%
confidence, we obtain rates up to one per 3 yr. For the advanced LIGO
detectors, the most probable rates are 10-500 events per year. These
predictions, for the first time, bring the expectations for DNS detections by
the initial LIGO detectors to the astrophysically relevant regime. We also use
our models to predict that the large-scale Parkes Multibeam pulsar survey with
acceleration searches could detect an average of four binary pulsars similar to
those known at present.


title: Discovery of the Faint Near-IR Afterglow of GRB 030528

abstract:
  We report on the discovery of the near-IR transient of the long-duration
gamma-ray burst GRB 030528 and its underlying host galaxy. The near-IR
transient was first observed in JHKs with SofI at the 3.6m ESO-NTT 16hrs after
the burst and later observations revealed a fading Ks-band afterglow. The
afterglow nature was confirmed by Chandra observations which found the source
to be a fading X-ray emitter. The lack of an optical afterglow and the early
faintness in the near-IR (Ks>18.5 mag) place GRB 030528 in a parameter space
usually populated by dark bursts. We find the host to be an elongated blue
galaxy.


title:
Particle Acceleration and Radiation associated with Magnetic Field
  Generation from Relativistic Collisionless Shocks

abstract:
  Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas.
Plasma waves and their associated instabilities (e.g., the Buneman instability,
two-streaming instability, and the Weibel instability) created in the shocks
are responsible for particle (electron, positron, and ion) acceleration. Using
a 3-D relativistic electromagnetic particle (REMP) code, we have investigated
particle acceleration associated with a relativistic jet front propagating
through an ambient plasma with and without initial magnetic fields. We find
only small differences in the results between no ambient and weak ambient
magnetic fields. Simulations show that the Weibel instability created in the
collisionless shock front accelerates particles perpendicular and parallel to
the jet propagation direction. The simulation results show that this
instability is responsible for generating and amplifying highly nonuniform,
small-scale magnetic fields, which contribute to the electron's transverse
deflection behind the jet head. The ``jitter'' radiation from deflected
electrons has different properties than synchrotron radiation which is
calculated in a uniform magnetic field. This jitter radiation may be important
to understanding the complex time evolution and/or spectral structure in
gamma-ray bursts, relativistic jets, and supernova remnants.


title:
X-ray Luminosity Function and Total Luminosity of LMXB in Early Type
  Galaxies

abstract:
  We have derived bias-corrected X-ray luminosity functions (XLFs) of sources
detected in a uniformly selected sample of 14 E and S0 galaxies observed with
Chandra ACIS-S3. The entire sample yields 985 point-like X-ray sources, with
typical detection of 30-140 sources per galaxy. After correcting for
incompleteness, the individual XLFs are statistically consistent with a single
power-law of a (differential) XLF slope b = 1.8 - 2.2 (with a typical error of
0.2-0.3). A break at or near LX,Eddington, as reported in the literature for
some of these galaxies, is not required in any case. Although the combined XLF
is marginally consistent with a single power-law (with b = 2.1 +- 0.1), a
broken power-law gives an improved fit. The best-fit slope is b = 1.8 +- 0.2 in
the low-luminosity range LX = a few x 1037 - 5 x 1038 ergs s-1. At higher
luminosities, the slope is steeper, b = 2.8 +- 0.6. The break luminosity is 5
+- 1.6 x 1038 ergs s-1 (with an error at 90%), which may be consistent with the
Eddington luminosity of neutron stars with the largest possible mass (3 Mo), of
He-enriched neutron star binaries, or low-mass stellar mass black holes. If the
change in XLF slope at high luminosities is real, our result would imply a
different population of high luminosity sources, instead of a beaming effect.
We confirm that the total X-ray luminosity of LMXBs is correlated with the
optical and more tightly with the near-IR luminosities, but in both cases the
scatter exceeds that expected from measurement errors. We find that the scatter
in LX(LMXB)/LK is marginally correlated with the specific frequency of globular
clusters.


title:
Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian
  509

abstract:
  To gain insight into four highly ionized high-velocity clouds (HVCs)
discovered by Sembach et al. (1999), we have analyzed data from the Hubble
Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the
PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in OVI and
column densities of multiple ionization stages of silicon (SiII/III/IV) and
carbon (CII/III/IV). We interpret this ionization pattern as a multiphase
medium that contains both collisionally ionized and photoionized gas. Toward
PKS 2155-304, for HVCs at -140 and -270 km/s, respectively, we measure
logN(OVI)=13.80+/-0.03 and log N(OVI)=13.56+/-0.06; from Lyman series
absorption, we find log N(HI)=16.37^(+0.22)_(-0.14) and 15.23^(+0.38)_(-0.22).
The presence of high-velocity OVI spread over a broad (100 km/s) profile,
together with large amounts of low-ionization species, is difficult to
reconcile with the low densities, n=5x10^(-6) cm^(-3), in the
collisional/photoionization models of Nicastro et al. (2002), although the HVCs
show a similar relation in N(SiIV)/N(CIV) versus N(CII)/N(CIV) as high-z
intergalactic clouds. Our results suggest that the high-velocity OVI in these
absorbers do not necessarily trace the WHIM, but instead may trace HVCs with
low total hydrogen column density. We propose that the broad high-velocity OVI
absorption arises from shock ionization, at bowshock interfaces produced from
infalling clumps of gas with velocity shear. The similar ratios of high ions
for HVC Complex C and these highly ionized HVCs suggest a common production
mechanism in the Galactic halo.


title: Linking star-formation and enivronment in the A901/902 supercluster

abstract:
  We investigate correlations between the location of galaxies in dense
environments and their degree of star-formation activity. Using photometric
redshifts and spectral classifications from the unique 17-band COMBO-17 survey
we are able to precisely isolate galaxies from the Abell 901/902 supercluster
within a thin redshift slice around z=0.16. We compare the detailed photometric
properties of the supercluster galaxies with the underlying dark matter density
field as revealed by weak gravitational lensing. We find strong evidence for
segregation by type, with the highest density regions populated almost
exclusively by galaxies classified according to their rest-frame U-V colours as
quiescent. We also observe a threshold surface mass density from lensing,
\kappa\sim 0.05 (corresponding to a physical density \Sigma = 2.5x10^(14)h
M_\sun Mpc^(-2)), above which star-formation activity is rapidly suppressed.
This abrupt transformation affects primarily the faint end of the star-forming
galaxy population and occurs at a local surface number density corresponding to
roughly 400h^2 Mpc^(-2) to a limit of M*_V+6. When only galaxies brighter than
M*+1 are considered the trends with environment remain, but are more gradual
and extend beyond 2h^(-1) Mpc radius.


title: The radio luminosity distribution of pulsars in 47 Tucanae

abstract:
  We have used the Australia Telescope Compact Array to seek the integrated
radio flux from all the pulsars in the core of the globular cluster 47 Tucanae.
We have detected an extended region of radio emission and have calibrated its
flux against the flux distribution of the known pulsars in the cluster. We find
the total 20-cm radio flux from the cluster's pulsars to be S = 2.0 +/- 0.3
mJy. This implies the lower limit to the radio luminosity distribution to be
L_1400 = 0.4 mJy kpc^2 and the size of the observable pulsar population to be N
< 30.


title: The infrared L'-band view of the Galactic Center with NAOS-CONICA at VLT

abstract:
  We report on Galactic Center L'-band observations made during NAOS/CONICA
Science Verification. Colors of the inner 2" stars reveal an infrared excess of
S2, the closest star to the black hole, that could sign the first thermal
infrared detection of Sgr A*. A multi-wavelength maximum likelihood analysis
has allowed us to eliminate all but two of the candidates for gravitational
lensing proposed by Alexander (2001). Our observations of the thin and
intersecting structures of the Northern Arm could trace several shocks heating
the neighbooring dust rather than a stream of matter in orbit around the
central mass as previously thought.


title: The Dark Matter Radial Profile in the Core of the Relaxed Cluster A2589

abstract:
  We present an analysis of a Chandra--ACIS observation of the galaxy cluster
A2589 to constrain the radial distribution of the total gravitating matter and
the dark matter in the core of the cluster. A2589 is especially well-suited for
this analysis because the hot gas in its core region (r < ~0.1 Rvir) is
undisturbed by interactions with a central radio source. From the largest
radius probed (r=0.07 Rvir) down to r ~0.02 Rvir dark matter dominates the
gravitating mass. Over this region the radial profiles of the gravitating and
dark matter are fitted well by the NFW and Hernquist profiles predicted by CDM.
The density profiles are also described well by power laws, rho ~r^{-alpha},
where alpha=1.37 +/- 0.14 for the gravitating matter and alpha=1.35 +/- 0.21
for the dark matter. These values are consistent with profiles of CDM halos but
are significantly larger than alpha ~0.5 found in LSB galaxies and expected
from self-interacting dark matter models.


title: Morphology of the supercluster-void network in LCDM cosmology

abstract:
  We report here the first systematic study of the supercluster-void network in
the LCDM concordance cosmology in which voids and superclusters are treated on
an equal footing. Superclusters are defined as individual members of an
over-dense excursion set and voids are defined as individual members of a
complementary under-dense excursion set at the same density threshold. We
determine the geometric, topological and morphological properties of the cosmic
web at a large set of density levels by computing Minkowski functionals for
every supercluster and void using SURFGEN. The properties of the largest
(percolating) supercluster and the complementary void are found to be very
different from properties of individual superclusters and voids. Individual
superclusters totally occupy no more than about 5% of the total volume and
contain no more than 20% of mass if the largest supercluster is excluded.
Likewise, individual voids totally occupy no more than 14% of volume and
contain no more than 4% of mass if the largest void is excluded. Although
superclusters are more massive and voids are more voluminous the difference in
maximum volumes is not greater than by an order of magnitude. The genus value
of individual superclusters can be 5 while the genus of individual voids can
reach 40, implying significant amount of substructure in superclusters and
especially in voids. One of our main results is that large voids, as defined
through the density field (read dark matter distribution) can be distinctly
non-spherical.


title: Sub-millimeter emission from type Ia supernova host galaxies at z=0.5

abstract:
  We present deep sub-millimetre observations of seventeen galaxies at z=0.5,
selected through being hosts of a type 1a supernova. Two galaxies are detected
directly, and the sample is detected statistically with a mean 850 micron flux
of 1.01mJy +/- 0.33mJy, which is 25% - 135% higher than locally. We infer that
the mean value of A_v in normal galaxies at z=0.5 is comparable to or greater
than the mean A_v in local normal galaxies, in agreement with galaxy chemical
evolution models and indirect observational evidence. Scaling from the local
value given by Rowan-Robinson (2003) gives a mean extinction at z=0.5 of A_v =
0.56 +/- 0.17. The dust in the brightest sub-mm object in our sample is best
interpreted as normal `cirrus' dust similar to that seen locally. The detection
rate of our sample suggests that some sources found in blank-field sub-mm
surveys may not be high redshift starbursts, but rather cirrus galaxies at
moderate redshifts and with lower star formation rates. Finally, an increase in
host dust extinction with redshift may impact the cosmological results from
distant supernova searches. This emphasizes the need to carefully monitor dust
extinction when using type Ia supernovae to measure the cosmological
parameters.


title:
Formation of star clusters in the LMC and SMC. I. Preliminary results on
  cluster formation from colliding gas clouds

abstract:
  We demonstrate that single and binary star clusters can be formed during
cloud-cloud collisions triggered by the tidal interaction between the Large and
Small Magellanic clouds. We run two different sets of self-consistent numerical
simulations which show that compact, bound star clusters can be formed within
the centers of two colliding clouds due to strong gaseous shocks, compression,
and dissipation, providing the clouds have moderately large relative velocities
(10-60 km s$^{-1}$). The impact parameter determines whether the two colliding
clouds become a single or a binary cluster. The star formation efficiency in
the colliding clouds is dependent upon the initial ratio of the relative
velocity of the clouds to the sound speed of the gas. Based on these results,
we discuss the observed larger fraction of binary clusters, and star clusters
with high ellipticity, in the Magellanic clouds.


title: Be-star rotation: how close to critical?

abstract:
  We argue that, in general, observational studies of Be-star rotation have
paid insufficient attention to the effects of equatorial gravity darkening. We
present new line-profile calculations that emphasize the insensitivity of line
width to rotation for fast rotators. Coupled with a critical review of
observational procedures, these calculations suggest that the observational
parameter v sin(i) may systematically underestimate the true projected
equatorial rotation velocity, ve sin(i), by some tens of per cent for rapid
rotators. The crucial implication of this work is that Be stars may be rotating
much closer to their critical velocities than is generally supposed, bringing a
range of new processes into contention for the elusive physical mechanism
responsible for the circumstellar disk thought to be central to the Be
phenomenon.


title:
Faint 6.7um Galaxies and their Contributions to the Stellar Mass Density
  in the Universe

abstract:
  We discuss the nature of faint 6.7um galaxies detected with the mid-infrared
camera ISOCAM on board the Infrared Space Observatory (ISO). The 23 hour
integration on the Hawaii Deep Field SSA13 has provided a sample of 65 sources
down to 6uJy at 6.7um. For 57 sources, optical or near-infrared counterparts
were found with a statistical method. All four Chandra sources, three SCUBA
sources, and one VLA/FIRST source in this field were detected at 6.7um with
high significance. Using their optical to mid-infrared colors, we divided the
6.7um sample into three categories: low redshift galaxies with past histories
of rapid star formation, high redshift ancestors of these, and other star
forming galaxies. Rapidly star forming systems at high redshifts dominate the
faintest end. Spectroscopically calibrated photometric redshifts were derived
from fits to a limited set of template SEDs. They show a high redshift tail in
their distribution with faint (<30uJy) galaxies at z>1. The 6.7um galaxies tend
to have brighter K magnitudes and redder I-K colors than the blue dwarf
population at intermediate redshifts. Stellar masses of the 6.7um galaxies were
estimated from their rest-frame near-infrared luminosities. Massive galaxies
(M_star~10e11M_sun) were found in the redshift range of z=0.2-3. Epoch
dependent stellar mass functions indicate a decline of massive galaxies'
comoving space densities with redshift. Even with such a decrease, the
contributions of the 6.7um galaxies to the stellar mass density in the universe
are found to be comparable to those expected from UV bright galaxies detected
in deep optical surveys.


title: Tidal Streams and Low Mass Companions of M31

abstract:
  We have imaged the extended HI environment of M31 with an unprecedented
combination of high resolution and sensitivity. We detect a number of distinct
High Velocity Cloud components associated with M31. A sub-set of the features
within 30 kpc appear to be tidal in origin. A filamentary ``halo'' component is
concentrated at the M31 systemic velocity and appears to extend into a
``bridge'' connecting M31 and M33. This may represent condensation in coronal
gas. A population of discrete clouds is detected out to radii of about 150 kpc.
Discrete cloud line-widths are correlated with HI mass and are consistent with
a 100:1 ratio of dark to HI mass. These may be the gaseous counterparts of
low-mass dark-matter satellites. The combined distribution of M31's HVC
components can be characterized by a spatial Gaussian of 55 kpc dispersion and
yields an N_HI distribution function which agrees well with that of low
red-shift QSOs.


title:
Optically bright Active Galactic Nuclei in the ROSAT-Faint Source
  Catalogue

abstract:
  To build a large, optically bright, X-ray selected AGN sample we have
correlated the ROSAT-FSC catalogue of X-ray sources with the USNO catalogue
limited to objects brighter than O=16.5 and then with the APS database. Each of
the 3,212 coincidences was classified using the slitless Hamburg spectra. 493
objects were found to be extended and 2,719 starlike. Using both the extended
objects and the galaxies known from published catalogues we built up a sample
of 185 galaxies with O_APS < 17.0 mag, which are high-probability counterparts
of RASS-FSC X-ray sources. 130 galaxies have a redshift from the literature and
for another 34 we obtained new spectra. The fraction of Seyfert galaxies in
this sample is 20 %. To select a corresponding sample of 144 high-probability
counterparts among the starlike sources we searched for very blue objects in an
APS-based color-magnitude diagram. Forty-one were already known AGN and for
another 91 objects we obtained new spectra, yielding 42 new AGN, increasing
their number in the sample to 83. This confirms that surveys of bright QSOs are
still significantly incomplete. On the other hand we find that, at a flux limit
of 0.02 count /-1 and at this magnitude, only 40 % of all QSOs are detected by
ROSAT.


title: Radio Properties of EROs in the Phoenix Deep Survey

abstract:
  Insensitive to dust obscuration, radio wavelengths are ideal to study
star-forming galaxies free of dust induced biases. Using data from the Phoenix
Deep Survey, we have identified a sample of star-forming extremely red objects
(EROs). Stacking of the radio images of the radio-undetected star-forming EROs
revealed a significant radio detection. Using the expected median redshift, we
estimate an average star-formation rate of 61 M_sun/yr for these galaxies.


title: XMM-Newton Observations of the Ultraluminous Nuclear X-ray Source in M33

abstract:
  We present observations with XMM-Newton of M33 X-8, the ultraluminous X-ray
source (L_{0.5-10 keV} ~ 2x10^39 erg/s) closest to the centre of the galaxy.
The best-fit model is similar to the typical model of Galactic black holes in
very high state. Comparison with previous observations indicates that the
source is still in a very high state after about 20 years of observations. No
state transition has been observed even during the present set of XMM-Newton
observations. We estimate the lower limit of the mass of the black hole >6
M_sun, but with proper parameters taking into account different effects, the
best estimate becomes 12 M_sun. Our analysis favours the hypothesis that M33
X-8 is a stellar mass black hole candidate, in agreement with the findings of
other authors. In addition, we propose a different model where the high
luminosity of the source is likely to be due to orientation effects of the
accretion disc and anisotropies in the Comptonized emission.


title: A young and complex binary star - HD 144432

abstract:
  The southern emission-line star HD 144432 has received considerable attention
due to its relative brightness (V ~ 8.17), its late spectral type (late A-type
or perhaps early F) and its relative isolation from a bona-fide active star
formation region. We present new imaging and spectroscopic data of this star,
which in the past has been classified as both evolved (post-AGB) object and an
isolated Herbig Ae/Be star. We confirm the presence of a faint companion source
located 1.4 arcseconds north, which appears physically associated with HD
144432. New infrared spectroscopy reveals this companion to be a late-type
(early-mid K) star, devoid of any emission lines. Furthermore, we confirm the
pre-main sequence nature of this object, report the detection of Li I 6707.8 AA
absorption toward the HD 144432 system, and its apparent association with Sco
OB2-2 located at 145 pc.


title: Galaxy luminosity evolution: how much is due to a model choice?

abstract:
  The cluster and field luminosity functions (LFs) determined on large
homogeneous samples (N>2200 galaxies each) are almost indistinguishable, down
to M^*+4 in the r and i filters, hence suggesting that the effect of the
cluster environment on the galaxy properties does not affect the galaxy
luminosity function in red bands. The similarity of the red band LFs in
different environments suggests that the galaxy mass function is preserved
during the galaxy infall in the cluster. By analyzing a large sample of
galaxies in clusters, ideal from many points of view (multicolor data, large
size, many clusters, metric magnitudes) we found that luminosity evolution is
required by the data but the latter do not unambiguously derive its flavour if
a differential luminosity evolution between bright and faint galaxies is
allowed. We show that the LF parameters (slope, characteristic magnitude and
their evolution) and errors depend on assumptions in a way seldom recognized in
literature. We also point out logical inconsistencies between hypothesis
assumed in deriving literature LF and presented results, suggesting caution in
interpreting similar published results.


title: The Effect of Metallicity on the Cepheid Period-Luminosity Relation

abstract:
  We present preliminary results of an observational campaign devoted at
establishing the influence of chemical composition on the Cepheid
Period-Luminosity relation. The data are in good agreement with theoretical
predictions based on non-linear convective models, suggesting a fairly strong
dependence of the Period-Luminosity relation on metallicity in the sense of
more metal rich stars being intrinsically fainter than otherwise expected. Our
data indicate that the error on the inferred distance can be as large as 10% if
the role of metallicity is neglected.


title:
Searching for Planets in the Hyades III: The Quest for Short-Period
  Planets

abstract:
  We have been using the Keck I High Resolution Spectrograph (HIRES) to search
for planetary companions in the Hyades cluster. We selected four stars from
this sample which showed significant radial velocity variability on short
timescales to search for short-period planetary companions. The radial
velocities of these four stars were monitored regularly with the Hobby Eberly
Telescope (HET) for approximately two months, while sparse data were also taken
over ~4 months: we also obtained near-simultaneous photometric observations
with one of the automatic photoelectric telescopes at Fairborn Observatory. For
three of the stars, we detect photometric variability with the same period
present in the radial velocity (rv) measurements, compatible with the expected
rotation rates for Hyades members. The fourth star continues to show rv
variations and minimal photometric variability but with no significant
periodicity. This study shows that for the three stars with periodic behavior,
a significant portion of the rv fluctuations are likely due primarily to
magnetic activity modulated by stellar rotation rather than planetary
companions. Using simple models for the rv perturbations arising from spot and
plage, we demonstrate that both are likely to contribute to the observed rv
variations. Thus, simultaneous monitoring of photometric (photospheric) and
spectroscopic (chromospheric) variations is essential for identifying the cause
of Doppler shifted absorption lines in more active stars.


title: Signature of HDM clustering at Planck angular scales

abstract:
  We present the CMB anisotropy induced by the non-linear perturbations in the
massive neutrino density associated to the non-linear gravitational clustering.
We show that the non-linear time varying potential induced by the gravitational
clustering process generates metric perturbations that affect the time
evolution of the density fluctuations in all the components of the expanding
Universe, leaving imprints on the CMB anisotropy power spectrum at subdegree
angular scales. For a neutrino fraction in agreement with that indicated by the
astroparticle and nuclear physics experiments and a cosmological accreting mass
comparable with the mass of known clusters, we find that CMB anisotropy
measurements with {\sc Planck} angular resolution and sensitivity possibly
combined to other precise cosmological observations will allow the detection of
the dynamical, linear and non-linear effects of the neutrino gravitational
clustering.


title: Can the Local Supercluster explain the low CMB multipoles?

abstract:
  We show that the thermal Sunyaev-Zeldovich effect caused by hot electrons in
the Local Supercluster (LSC) can explain the abnormal quadrupole and octopole
of the cosmic microwave background (CMB) that were measured by WMAP and COBE.
The distortion needed to account for the low observed quadrupole is a spot in
the direction of the LSC with a temperature decrease of order \Delta T \approx
- 7 \mu K for \nu ~ 20 -- 90 Ghz photons. The temperature and density of the
hot gas which can generate such an effect are consistent with observations of
the X-ray background. If this hypothetic foreground is subtracted from the WMAP
data, we find that the amplitude of the quadrupole (l=2) is substantially
increased, and that the ``planarity'' of both the quadrupole and the octopole
(l=3) are weakened. For smaller scales the effect decays and, at least in our
simplified model, it does not affect the angular power spectrum at l>10.
Moreover, since the Sunyaev-Zeldovich effect increases the temperature of
photons with frequencies above 218 GHz, observations sensitive in that range
(such as PLANCK's HFI) will be able to confirm whether the LSC indeed affects
the CMB.


title: Hot H2O Emission and Evidence for Turbulence in the Disk of a Young Star

abstract:
  We report on the detection and analysis of hot ro-vibrational H2O emission
from SVS-13, a young stellar object previously known to have strong CO overtone
bandhead emission. Modeling of the high-resolution infrared spectrum shows that
the H2O emission is characterized by temperatures ~ 1500 K, significantly lower
than the temperatures that characterize the CO bandhead emission. The widths
for the H2O lines are also found to be smaller than those for the CO lines. We
construct a disk model for the emission that reproduces the CO and H2O
spectrum. In this model, the H2O lines originate at somewhat larger disk radii
(<= 0.3 AU) than the CO overtone lines (<= 0.1 AU). We find that the H2O
abundance is about a factor of 10 lower than the calculated chemical
equilibrium abundance. Large, approximately transonic, local line broadening is
required to fit the profile of the CO bandhead. If this velocity dispersion is
identified with turbulence, it is of significant interest regarding the
transport of angular momentum in disks. Large local broadening is also required
in modeling CO overtone emission from other young stellar objects, suggesting
that large turbulent velocities may be characteristic of the upper atmospheres
of the inner disks of young stars.


title: Obscuration and circumnuclear medium in nearby and distant AGN

abstract:
  Some recent results on the physical and statistical properties of nearby and
distant AGN are presented. I first discuss the properties of "elusive" AGNs,
i.e. obscured AGNs which do not show a Seyfert-like spectrum in the optical.
Then I present preliminary results from a detailed study of the contribution of
obscured AGNs and of their host galaxies to the infrared cosmic background.
Finally I discuss an observational program aimed at investigating the
properties of the most distant quasars, of their circumnuclear medium and the
implications for their host galaxies.


title:
Quantifying the Drivers of Star Formation on Galactic Scales. I. The
  Small Magellanic Cloud

abstract:
  We use the star formation history of the Small Magellanic Cloud (SMC) to
place quantitative limits on the effect of tidal interactions and gas infall on
the star formation and chemical enrichment history of the SMC. The coincident
timing of two recent (< 4 Gyr) increases in the star formation rate and
SMC/Milky Way(MW) pericenter passages suggests that global star formation in
the SMC is driven at least in part by tidal forces due to the MW. The Large
Magellanic Cloud (LMC) is the other potential driver of star formation, but is
only near the SMC during the most recent burst. The poorly constrained LMC-SMC
orbit is our principal uncertainty. To explore the correspondence between
bursts and MW pericenter passages further, we model star formation in the SMC
using a combination of continuous and tidally-triggered star formation. The
behavior of the tidally-triggered mode is a strong inverse function of the
SMC-MW separation (preferred behavior ~ r^-5, resulting in a factor of ~100
difference in the rate of tidally-triggered star formation at pericenter and
apocenter). Despite the success of these closed-box evolutionary models in
reproducing the recent SMC star formation history and current chemical
abundance, they have some systematic shortcomings that are remedied by
postulating that a sizable infall event (~ 50% of the total gas mass) occured
about 4 Gyr ago. Regardless of whether this infall event is included, the
fraction of stars in the SMC that formed via a tidally triggered mode is > 10%
and could be as large as 70%.


title: High-energy gamma-rays from stellar associations

abstract:
  It is proposed that TeV gamma-rays and neutrinos can be produced by cosmic
rays (CRs) through hadronic interactions in the innermost parts of the winds of
massive O and B stars. Convection prevents low-energy particles from
penetrating into the wind, leading to an absence of MeV-GeV counterparts. It is
argued that groups of stars located close to the CR acceleration sites in OB
stellar associations may be detectable by ground-based Cherenkov telescopes.