title: Magnetars and pulsars: a missing link

abstract:
  There is growing evidence that soft gamma-ray repeaters (SGRs) and anomalous
X-ray pulsars (AXPs) are isolated neutron stars with superstrong magnetic
fields, i.e., magnetars, marking them a distinguished species from the
conventional species of spindown-powered isolated neutron stars, i.e., radio
pulsars. The current arguments in favor of the magnetar interpretation of
SGR/AXP phenomenology will be outlined, and the two energy sources in
magnetars, i.e. a magnetic dissipation energy and a spindown energy, will be
reviewed. I will then discuss a missing link between magnetars and pulsars,
i.e., lack of the observational evidence of the spindown-powered behaviors in
known magnetars. Some recent theoretical efforts in studying such behaviors
will be reviewed along with some predictions testable in the near future.


title: The Chandra Observations of the Two Pulsars PSR 0628-28 and PSR 1813-36

abstract:
  PSR B0628-28 is an X-ray emitting radio pulsar which was observed with
Advanced CCD Imaging Spectrometer (ACIS) on board Chandra on 2001 November 04
and on 2002 March 25 for 2000 s and 17000 s, respectively. The source countrate
was 0.0111+-0.0013 cps. Making PSR B0628-28 to be the longest period X-ray
emitting pulsar. The spectral distribution of counts can be described by
several model fits. A blackbody fit yields a temperature
kT=2.69_{-0.09}^{+0.09}x10^{6} K together with
N_{H}=0.082_{-0.03}^{+0.04}x10^{22} cm^{-2} and a powerlaw fit yields a photon
index of \gamma=2.65_{-0.29}^{+0.28} with a hydrogen column density of
N_{H}=0.13_{-0.021}^{+0.028}x10^{22} cm^{-2}. Confirming the previous ROSAT
pointed observation for PSR 1813-36, there was no positive detection from the
30ks Chandra ACIS observation on 2001 October 25. We obtained an upper limit
for the countrate of 2.3x10^{-4} cps.


title: Air Shower Simulations in a Hybrid Approach using Cascade Equations

abstract:
  A new hybrid approach to air shower simulations is described. At highest
energies, each particle is followed individually using the traditional Monte
Carlo method; this initializes a system of cascade equations which are
applicable for energies such that the shower is one-dimensional. The cascade
equations are solved numerically down to energies at which lateral spreading
becomes significant, then their output serves as a source function for a
3-dimensional Monte Carlo simulation of the final stage of the shower. This
simulation procedure reproduces the natural fluctuations in the initial stages
of the shower, gives accurate lateral distribution functions, and provides
detailed information about all low energy particles on an event-by-event basis.
It is quite efficient in computation time.


title: Helical surface structures

abstract:
  Over the past few years there has been growing interest in helical magnetic
field structures seen at the solar surface, in coronal mass ejections, as well
as in the solar wind. Although there is a great deal of randomness in the data,
on average the extended structures are mostly left-handed on the northern
hemisphere and right-handed on the southern. Surface field structures are also
classified as dextral (= right bearing) and sinistral (= left bearing)
occurring preferentially in the northern and southern hemispheres respectively.
Of particular interest here is a quantitative measurement of the associated
emergence rates of helical structures, which translate to magnetic helicity
fluxes. In this review, we give a brief survey of what has been found so far
and what is expected based on models. Particular emphasis is put on the scale
dependence of the associated fields and an attempt is made to estimate the
helicity flux of the mean field vs. fluctuating field.


title: Timescale Spectra in High Energy Astrophysics

abstract:
  A technique of timescale analysis performed directly in the time domain has
been developed recently. We have applied the technique to studying rapid
variabilities of hard X-rays from neutron star and black hole binaries,
gamma-ray bursts and terrestrial gamma-ray flashes. The results indicate that
the time domain method of spectral analysis is a powerful tool in revealing the
underlying physics in high-energy processes in objects.


title: Flat-fielding of ACS WFC grism data

abstract:
  In direct imaging, broad band flat-fields can easily be applied to correct
deviation from uniform sensitivity across the detector field. However for
slitless spectroscopy data the flat field is both field and wavelength
dependent. The effect of the wavelength dependent flat field for the slitless
G800L grism mode of the ACS Wide Field Channel (WFC) has been investigated from
observations of a flux calibrator at different positions in the field. The
results of various flat-fielding schemes are presented including application of
a flat field cube derived from in-orbit broad band filter flat fields.
Excellent results are reported with deviations in the extracted spectra <2%
across the WFC field.


title: Imaging in Hard X-ray Astronomy

abstract:
  The energy range of hard X-rays is a key waveband to the study of high energy
processes in celestial objects, but still remains poorly explored. In contrast
to direct imaging methods used in the low energy X-ray and high energy
gamma-ray bands, currently imaging in the hard X-ray band is mainly achieved
through various modulation techniques. A new inversion technique, the direct
demodulation method, has been developed since early 90s. With this technique,
wide field and high resolution images can be derived from scanning data of a
simple collimated detector. The feasibility of this technique has been
confirmed by experiment, balloon-borne observation and analyzing simulated and
real astronomical data. Based the development of methodology and
instrumentation, a high energy astrophysics mission -- Hard X-ray Modulation
Telescope (HXMT) has been proposed and selected in China for a four-year
Phase-A study. The main scientific objectives are a full-sky hard X-ray (20-200
keV) imaging survey and high signal-to-noise ratio timing studies of high
energy sources.


title: A Possible Planetary Event OGLE-2002-BLG-055

abstract:
  The microlensing event OGLE-2002-BLG-055 has a single, but very reliable data
point, deviating upward from a single source microlensing light curve by 0.6
mag. The simplest interpretation calls for a binary lens with a strong parallax
effect and the mass ratio in the range 0.01 - 0.001, putting the companion in
the Jupiter mass range. Given only a single deviant point it is impossible to
fit a unique model. We propose a modification of OGLE observing strategy:
instant verification of a reality of future deviant points, followed by a
frequent time sampling, to make a unique model fit possible.


title: Early Virtual Science: some lessons for the AVO

abstract:
  Experience with ASTROVIRTEL, scientific analysis of current large data sets,
and detailed preparation for the truly huge future missions especially GAIA,
provide important lessons for the Astrophysical Virtual Observatory. They
demonstrate that the science cases are impressive, specifically allowing new
thresholds to be crossed. The AVO is more than just faster cheaper better, it
allows the new. The example of use of pre-explosion imaging of supernova to
identify progenitors is used to illustrate some general challenges. Some
non-trivial technical astronomical issues arise, especially astrometry, to
complement the many technical implementation challenges. A critical scientific
lesson is the need to quantify data quality. How are we to ensure the Virtual
Observatory produces top science, and avoids being overwhelmed with mediocre
data?


title: Are X-ray flashes a peculiar class of (soft) gamma-ray bursts ?

abstract:
  Heise et al. (2001) have reported the identification of a new class of
sources by Beppo-SAX, the so-called X-ray flashes (XRFs), which have many
common properties with gamma-ray bursts (GRBs) but are not detected in the
gamma-ray range. In the framework of the internal shock model, we investigate
the possibility that XRFs have the same origin than GRBs but are intrinsically
softer due to different shock parameters.


title:
A catalog of warps in spiral and lenticular galaxies in the Southern
  hemisphere

abstract:
  A catalog of optical warps of galaxies is presented. This can be considered
complementary to that reported by
  Sanchez-Saavedra et al., with 42 galaxies in the northern hemisphere, and to
that by Reshetnikov & Combes, with 60 optical warps.
  The limits of the present catalog are: logr25 > 0.60, B_{t} < 14.5,
delta(2000) < 0, -2.5 < t < 7. Therefore, lenticular galaxies have also been
considered. This catalog lists 150 warped galaxies out of a sample of 276
edge-on galaxies and covers the whole southern hemisphere, except the Avoidance
Zone.
  It is therefore very suitable for statistical studies of warps. It also
provides a source guide for detailed particular observations. We confirm the
large frequency of warped spirals: nearly all galaxies are warped. The
frequency and warp angle do not present important differences for the different
types of spirals. However, no lenticular warped galaxy has been found within
the specified limits. This finding constitutes an important restriction for
theoretical models.


title: Optimising GAIA: How do we meet the science challenge?

abstract:
  GAIA has been approved to provide the data needed to quantify the formation
and evolution of the Milky Way Galaxy, and its near neighbours. That requires
study of all four key Galactic stellar populations: Bulge, Halo, Thick Disk,
Thin Disk. The complex analysis methodologies required to model GAIA kinematic
data are being developed, and in the interim applied to the relatively simple
cases of the satellite dSph galaxies. These methodologies, illustrated here,
show that we will be able to interpret the GAIA data. They also quantify what
data GAIA must provide.
  It is very unlikely in the present design that GAIA will be able to provide
either radial velocities or worthwhile photometry for study of two of the key
science goals: the Galactic Bulge and the (inner) Galactic old disk. The
implication is that the radial velocity spectrometer and the medium band
photometer should be optimised for study of low density fields -- suitable for
their low spatial resolution -- and the broad band photometry must be optimised
for inner galaxy astrophysical studies.


title: Photospheric radius expansion X-ray bursts as standard candles

abstract:
  We examined the maximum bolometric peak luminosities during type I X-ray
bursts from the persistent or transient luminous X-ray sources in globular
clusters. We show that for about two thirds of the sources the maximum peak
luminosities during photospheric radius expansion X-ray bursts extend to a
critical value of (3.79+/-0.15)x10^{38} erg/s, assuming the total X-ray burst
emission is entirely due to black-body radiation and the recorded maximum
luminosity is the actual peak luminosity. This empirical critical luminosity is
consistent with the Eddington luminosity limit for hydrogen poor material.
Since the critical luminosity is more or less always reached during
photospheric radius expansion X-ray bursts (except for one source), such bursts
may be regarded as empirical standard candles. However, because significant
deviations do occur, our standard candle is only accurate to within 15%. We
re-evaluated the distances to the twelve globular clusters in which the X-ray
bursters reside.


title: Oxygen in the Galactic thin and thick disks

abstract:
  First results from a study into the abundance trends of oxygen in the
Galactic thin and thick disks are presented. Oxygen abundances for 21 thick
disk and 42 thin disk F and G dwarf stars based on very high resolution spectra
(R\sim 215000) and high signal-to-noise (S/N>400) of the faint forbidden oxygen
line at 6300 A have been determined. We find that [O/Fe] for the thick disk
stars show a turn-down, i.e. the ``knee'', at [Fe/H] between -0.4 and -0.3 dex
indicating the onset of SNe type Ia. The thin disk stars on the other hand show
a shallow decrease going from [Fe/H] \sim -0.7 to the highest metallicities
with no apparent ``knee'' present indicating a slower star formation history.


title: The Shroud Around the Twin Radio Jets in NGC 1052

abstract:
  (Abridged) We discuss multiple VLBI continuum and spectral line observations
and WSRT spectroscopy of NGC 1052. Sub-parsec scale features move outward at
approximately 0.26c in bi-symmetric jets, most likely oriented near the plane
of the sky. Absorption and emission signatures reveal ionised, atomic, and
molecular components of the surrounding medium.
  Seven-frequency (1.4 to 43 GHz) VLBA observations show free-free absorption
in the inner parsec, probably together with synchrotron self-absorption. There
is apparently a geometrically thick but patchy structure oriented roughly
orthogonal to the jets. The western jet is receding: it is covered more deeply
and extensively. HI spectral line VLBI reveals atomic gas in front of both
jets. There appear to be three velocity systems. The deepest, at "high
velocities" (receding by 125 to 200 km/s), seems restricted to a shell 1 to 2
pc away from the core, within which this gas might be largely ionised. WSRT
spectroscopy has revealed 1667 and 1665 MHz OH absorption with their line ratio
varying roughly from 1:1 to 2:1 between -35 and 200 km/s. In the high velocity
system the OH profiles are similar to HI, suggesting co-location of that atomic
and molecular gas, and leaving unclear the connection to the H2O masing gas
seen elsewhere. We have also detected both 18cm OH satellite lines in the high
velocity system. They have conjugate profiles: 1612 MHz is in absorption, and
1720 MHz in emission.


title:
Chaos and Chaotic Phase Mixing in Galaxy Evolution and Charged Particle
  Beams

abstract:
  This paper discusses three new issues that necessarily arise in realistic
attempts to apply nonlinear dynamics to galaxy evolution, namely: (i) the
meaning of chaos in many-body systems, (ii) the time-dependence of the bulk
potential, which can trigger intervals of {\em transient chaos}, and (iii) the
self-consistent nature of any bulk chaos, which is generated by the bodies
themselves, rather than imposed externally. Simulations and theory both suggest
strongly that the physical processes associated with galactic evolution should
also act in nonneutral plasmas and charged particle beams. This in turn
suggests the possibility of testing this physics in real laboratory
experiments, an undertaking currently underway.


title:
Understanding the spectra of isolated Herbig stars in the frame of a
  passive disk model

abstract:
  We discuss spectral energy distributions of a sample of Herbig Ae/Be stars in
the context of a passive irradiated disk model. The data have been presented
earlier by Meeus et al (2001), and preliminary interpretations of these data
were given in that paper. While the spectra of Herbig Ae stars all show
similarities, there is significant variation between the spectra, in particular
in the shape of the mid-IR rise and in the presence or absence of a silicate
feature. We explore the hypothesis that all these different spectra can be
interpreted as pure disk spectra without additional components. Using the model
of Dullemond, Dominik and Natta (2001) we deduce the disk parameters of a
number of the sources, and find that for a large fraction of investigated
sources, satisfactory fits can be obtained. The derived model parameters show
that some group Ia sources can only be fit with radially increasing surface
densities, indicating the presence of depleted inner disk regions. The
steep-sloped SEDs of group IIa sources can be fit with very compact disks,
probably representing disks with collapsed outer regions. The largest
difficulties arise from sources that do not show significant silicate emission
features. Our attempts to explain these objects with a pure geometric effect
are only partially successful. It seems that these stars indeed require a
strong depletion of small silicate grains.


title:
TRIDENT: an infrared camera optimized for the detection of methanated
  substellar companions around nearby stars

abstract:
  A near-infrared (0.85-2.5 microns) camera in use at the Canada-France-Hawaii
Telescope and at the 1.6m telescope of the Observatoire du Mont-Megantic is
described. The camera is based on a Hawaii-1 1024x1024 HgCdTe array detector.
Its main feature is to acquire three simultaneous images at three wavelengths
(simultaneous differential imaging) across the methane absorption bandhead at
1.6 micron, enabling an accurate subtraction of the stellar point spread
function (PSF) and the detection of faint close methanated companions. The
instrument has no coronagraph and features a fast (1 MHz) data acquisition
system without reset anomaly, yielding high observing efficiencies on bright
stars. The performance of the instrument is described, and it is illustrated by
CFHT images of the nearby star Ups And. TRIDENT can detect (3 sigma) a
methanated companion with DeltaH=10 at 0.5 arcsec from the star in one hour of
observing time. Non-common path aberrations between the three optical paths are
the limiting factors preventing further PSF attenuation. Reference star
subtraction and instrument rotation improve the detection limit by one order of
magnitude.


title: X-Ray Lines and Absorption Edges in GRBs and Their Afterglows

abstract:
  Absorption and Reprocessing of Gamma-ray burst radiation in the environment
of cosmological GRBs can be used as a powerful probe of the elusive nature of
their progenitors. In particular, transient X-ray emission line and absorption
features in the prompt and early afterglows of GRBs are sensitive to details of
the location and density structure of the reprocessing and/or absorbing
material. To date, there have been only rather few detections of such features,
and the significance is marginal in most individual cases. However, transient
X-ray emission lines in GRB afterglows have now been found by four different
X-ray satellites, which may justify a more detailed theoretical investigation
of their origin. In this paper, I will first present a brief review of the
status of observations of transient X-ray emission line and absorption
features. I will then discuss general physics constraints which those results
impose on isotropy, homogeneity, and location of the reprocessing material with
respect to the GRB source, and review the various currently discussed, specific
models of GRBs and their environments in which the required conditions could
arise.


title:
X-ray and optical properties of X-ray sources in the 13hr
  XMM-Newton/Chandra deep survey

abstract:
  The 13hr XMM-Newton/Chandra deep survey is the first of two extremely deep
XMM-Newton fields observed by the XMM-OM consortium. A 120 ks Chandra mosaic,
covering 0.2 square degrees, provides sensitive, confusion-free point source
detection with sub-arcsecond positions, while the 200 ks XMM-Newton observation
provides high quality X-ray spectroscopy over the same sky area. We have
optical spectroscopic identifications for 70 X-ray sources. Of these, 42 are
broad emission-line AGN with a wide range of redshifts. The optical
counterparts of a further 23 sources are narrow emission line galaxies and
absorption line galaxies. These 23 sources all lie at z < 1 and typically have
lower X-ray luminosities than the broad-line AGN. About half of them show
significant X-ray absorption and are almost certainly intrinsically absorbed
AGN. However some of them have unabsorbed, AGN-like, power-law components in
their X-ray spectra, but do not show broad emission lines in their optical
spectra. These sources may be weak, unobscured AGN in bright galaxies and their
existence at low redshifts could be a consequence of the strong cosmological
evolution of AGN characteristic luminosities.


title: Radio observations of the XMM-Newton/Chandra 13hr deep survey field

abstract:
  Our VLA observations of the XMM-Newton/Chandra 13hr deep survey field (see
Page et al., this proceedings) result in one of the two deepest 1.4GHz radio
maps ever made. Within the 15' radius field covered by the deep X-ray data
(0.19 sq deg), a total of 556 radio sources are detected, down to a 4 sigma
flux limit of 28uJy. Of the 214 Chandra sources, 55 have radio counterparts.
The sub-arcsecond accuracy of the VLA and Chandra positions enable us to
determine with high confidence the sources common to both surveys. Here we
present the relationship between the X-ray and radio source populations at the
faintest radio flux limits yet probed by such a study. We discuss how the
X-ray/radio relationship differs as a function of optical morphology, ie
between unresolved `stellar' objects and well resolved galaxies. We then
discuss the origin of the X-ray and radio emission, ie AGN, starburst or a
mixture of both, in these two classes of object.


title: Super Soft Sources

abstract:
  The class of Super Soft Sources has been established after discoveries
performed with the Einstein and the ROSAT satellite. Only sources contributing
to the class of super-soft X-ray binaries are considered. The X-ray emission in
these sources is due to thermonuclear burning of accreted material on the
surface of a white dwarf. The physical process of nuclear burning is described.
The typical timescales of variability in these sources are discussed. The
appearance and modeling of supersoft X-ray spectra are described. The phenomena
related to the accretion disk in these sources are outlined. A discussion of
the nature and appearance of the donor star is given. The evolutionary state of
these sources and their likely progenitorship for Type Ia supernovae is shortly
outlined. A summary of recent discoveries with Chandra and XMM-Newton of
super-soft sources in nearby spiral and elliptical galaxies is given.


title:
The Discovery of H2O Maser Emission in Seven AGN and at High Velocities
  in the Circinus Galaxy

abstract:
  We report the discovery of H2O maser emission at 1.35 cm wavelength in seven
active galactic nuclei (at distances up to <80 Mpc) during a survey conducted
at the 70-m diameter antenna of the NASA Deep Space Network near Canberra,
Australia. The detection rate was (approx.) 4%. Two of the maser sources are
particularly interesting because they display satellite high-velocity emission
lines, which are a signature of emission from the accretion disks of
supermassive black holes when seen edge on. Three of the masers are coincident,
to within uncertainties of 0.''2, with continuum emission sources we observed
at about (lamda)1.3 cm. We also report the discovery of new spectral features
in the Circinus galaxy H2O maser that broaden the known velocity range of
emission therein by a factor of (approx.) 1.7. If the new spectral features
originate in the Circinus accretion disk, then molecular material must survive
at radii (approx.) 3 times smaller than had been believed previously [(approx.)
0.03 pc or (approx.) 2 x 105 Schwarzschild radii].


title: Effects of Quasi-Static Aberrations in Faint Companion Searches

abstract:
  We present the first results obtained at CFHT with the TRIDENT infrared
camera, dedicated to the detection of faint companions close to bright nearby
stars. The camera's main feature is the acquisition of three simultaneous
images in three wavelengths (simultaneous differential imaging) across the
methane absorption bandhead at 1.6 micron, that enables a precise subtraction
of the primary star PSF while keeping the companion signal. The main limitation
is non-common path aberrations between the three optical paths that slightly
decorrelate the PSFs. Two types of PSF calibrations are combined with the
differential simultaneous imaging technique to further attenuate the PSF:
reference star subtraction and instrument rotation to smooth aberrations. It is
shown that a faint companion with a DeltaH of 10 magnitudes would be detected
at 0.5 arcsec from the primary.


title: The Hydrodynamics and Chemical Evolution of Starburst-driven Outflows

abstract:
  The hydrodynamics and intrinsic properties of galactic-scale gaseous outflows
generated by violent starbursts are thoroughly discussed, taking into account
the hot gas chemical evolution and radiative cooling. It is shown that the
metallicity of superbubbles vary with time and can easily exceed the solar
value. Galactic superwinds driven by compact and powerful starbursts undergo
catastrophic cooling and establish a temperature distribution radically
different to that predicted by adiabatic solution. The observational properties
of supergalactic winds in X-rays and visible line regimes derived from our
calculations are compared with the standard adiabatic model predictions.


title: Microlensing induced absorption line variability

abstract:
  Gravitational microlensing has proven to be a powerful probe of both the
structure at the heart of quasars and the mass function of compact objects in
foreground lenses. This paper examines the potential of gravitational
microlensing in probing the scale of structure in absorbing material within the
lensing galaxy. We find that, in this high optical depth regime, significant
variations in the equivalent width of absorption features can be induced,
although the details of these are dependent upon the scale of structure of the
absorbing material. The paper concludes with an examination of the absorption
line variability observed in the gravitationally lensed quasar PKS1830-211,
demonstrating how this may indicate the presence of small scale structure in
the cold molecular gas present within the lensing galaxy.


title:
A new extragalactic distance determination method using the
  flux-weighted gravity of late B and early A supergiants

abstract:
  Stellar evolution calculations predict the flux-weighted gravity g/Teff^4 and
absolute bolometric magnitude of blue supergiants to be strongly correlated. We
use medium resolution multi-object spectroscopy of late B and early A
supergiants in two spiral galaxies, NGC 300 and NGC 3621, to demonstrate the
existence of such a relationship, which proves to be surprisingly tight. An
analysis of high resolution spectra of blue supergiants in Local Group galaxies
confirms this detection. We discuss the application of the relationship for
extragalactic distance determinations and conservatively conclude that once
properly calibrated it has the potential to allow for measurements of distance
moduli out to 30.5 mag with an accuracy of 0.1 mag or better.


title:
Electrodynamics of Outer-Gap Accelerator: Formation of Soft Power-law
  Spectrum Between 100 MeV and 3 GeV

abstract:
  We investigate a stationary pair production cascade in the outer
magnetosphere of a spinning neutron star. The charge depletion due to global
flows of charged particles, causes a large electric field along the magnetic
field lines. Migratory electrons and/or positrons are accelerated by this field
to radiate gamma-rays via curvature and inverse-Compton processes. Some of such
gamma-rays collide with the X-rays to materialize as pairs in the gap. The
replenished charges partially screen the electric field, which is
self-consistently solved together with the energy distribution of particles and
gamma-rays at each point along the field lines. By solving the set of Maxwell
and Boltzmann equations, we demonstrate that an external injection of charged
particles at nearly Goldreich-Julian rate does not quench the gap but shifts
its position and that the particle energy distribution cannot be described by a
power-law. The injected particles are accelerated in the gap and escape from it
with large Lorentz factors. We show that such escaping particles migrating
outside of the gap contribute significantly to the gamma-ray luminosity for
young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV
observed for the Vela pulsar can be explained by this component. We also
discuss that the luminosity of the gamma-rays emitted by the escaping particles
is naturally proportional to the square root of the spin-down luminosity.


title:
Faint dwarf spheroidals in the Fornax Cluster: A flat luminosity
  function

abstract:
  We have discovered about 70 very faint dwarf galaxies in the Fornax Cluster.
These dSphs candidates follow the same magnitude-surface brightness relation as
their counterparts in the Local Group, and even extend it to fainter limits.
The faintest dSph candidate in our sample has an absolute magnitude of M_V =
-8.8 mag and a central surface brightness of mu_V = 27 mag/arcsec^2. There
exists a tight color-magnitude relation for the early-type galaxies in Fornax
that extends from the giant to the dwarf regime. The faint-end slope of the
luminosity function of the early-type dwarfs is flat (alpha = -1.1+/-0.1),
contrary to the results obtained by Kambas et al. (2000).


title: Neutrinos from Gamma-Ray Bursts in Pulsar Wind Bubbles: \sim 10^{16} eV

abstract:
  The supranova model for Gamma-Ray Bursts (GRBs) is becoming increasingly more
popular. In this scenario the GRB occurs weeks to years after a supernova
explosion, and is located inside a pulsar wind bubble (PWB). Protons
accelerated in the internal shocks that emit the GRB may interact with the
external PWB photons producing pions which decay into \sim 10^{16} eV
neutrinos. A km^2 neutrino detector would observe several events per year
correlated with the GRBs.


title: X-ray bright groups and their galaxies

abstract:
  Combining X-ray data from the ROSAT PSPC and optical data drawn from the
literature, we examine in detail the relationship between the X-ray and optical
properties of X-ray bright galaxy groups. We find a relationship between
optical luminosity and X-ray temperature consistent with that expected from
self-similar scaling of galaxy systems, L_B \propto T^{1.6 +/- 0.2}. The
self-similar form and continuity of the L_B : T relation from clusters to
groups and the limited scatter seen in this relation, implies that the star
formation efficiency is rather similar in all these systems. We find that the
bright extended X-ray components associated with many central galaxies in
groups appear to be more closely related to the group than the galaxy itself,
and we suggest that these are group cooling flows rather than galaxy halos. In
addition we find that the optical light in these groups appears to be more
centrally concentrated than the light in clusters. We also use the optical and
X-ray data to investigate whether early or late type galaxies are primarily
responsible for preheating in groups. Using three different methods, we
conclude that spiral galaxies appear to play a comparable role to early types
in the preheating of the intragroup medium. This tends to favour models in
which the preheating arises primarily from galaxy winds rather than AGN, and
implies that spirals have played a significant role in the metal enrichment of
the intragroup medium.


title: The morphology-density relation in X-ray bright galaxy groups

abstract:
  We have examined the morphological make-up of X-ray bright groups. The
brighter galaxies in these groups exhibit clear morphology-density and
morphology-radius relations. The group morphology-density relation is offset
from the cluster relation in the sense that at a given surface density, X-ray
bright groups have a lower spiral fraction. After correcting for projection
effects the morphology-3D density relation is still shifted towards fewer
spirals for a given 3D density, in comparison with clusters. A simple model
which corrects the group data for the effects of projection and for the
expected higher merging rate in groups, brings the morphology-density relation
into good agreement with that of clusters, suggesting that the relation may be
driven by two-body interactions. The fraction of S0 galaxies in these X-ray
bright groups is at least as high as that observed in nearby clusters. Given
the low velocity dispersion of groups, this indicates that ram pressure
stripping is not the dominant mechanism for S0 formation.


title:
The Probability Distribution of the Double Neutron Star Coalescence Rate
  and Predictions for More Detections

abstract:
  We present an analysis method that allows us to estimate the Galactic
formation of radio pulsar populations based on their observed properties and
our understanding of survey selection effects. More importantly, this method
allows us to assign a statistical significance to such rate estimates and
calculate the allowed ranges of values at various confidence levels. Here, we
apply the method to the question of the double neutron star (NS-NS) coalescence
rate using the current observed sample, and we find calculate the most likely
value for the total Galactic coalescence rate to lie in the range 3-22
Myr^{-1}, for different pulsar population models. The corresponding range of
expected detection rates of NS--NS inspiral are (1-9)x10^{-3} yr^{-1} for the
initial LIGO, and 6-50 yr^{-1} for the advanced LIGO. Based on this newly
developed statistical method, we also calculate the probability distribution
for the expected number of pulsars that could be observed by the Parkes
Multibeam survey, when acceleration searches will alleviate the effects of
Doppler smearing due to orbital motions. We suggest that the Parkes survey will
probably detect 1-2 new binary pulsars like PSRs B1913+16 and/or B1534+12.


title: On the Spiral Structure of NGC 2915 and Dark Matter

abstract:
  NGC 2915 is a blue compact dwarf galaxy embedded in an extended, low surface
brightness HI disk exhibiting a two-armed spiral structure and a central
bar-like component. Commonly accepted mechanisms are unable to explain the
existence of these patterns and Bureau et al. proposed disk dark matter
(scaling with the HI distribution) or a rotating triaxial dark halo as
alternative solutions. In an attempt to explore these mechanisms,
hydrodynamical simulations were run for each case and compared to observations
using customized column density and kinematic constraints. The spiral structure
can be accounted for both by an unseen bar or triaxial halo, the former fitting
the observations slightly better. However, the large bar mass or halo pattern
frequency required make it unlikely that the spiral wave is driven by an
external perturber. In particular, the spin parameter is much higher than
predicted by current cold dark matter (CDM) structure formation scenarios. The
massive disk models show that when the observed gas surface density is scaled
up by a factor about 10, the disk develops a spiral structure resembling
closely the observed one, in perturbed density as well as perturbed velocity.
This is consistent with more limited studies in other galaxies and suggests
that the disk of NGC 2915 contains much more mass than is visible, tightly
linked to the neutral hydrogen. A classic (quasi-)spherical halo is
nevertheless still required, as increasing the disk mass further to fit the
circular velocity curve would make the disk violently unstable. Scaling the
observed surface density profile by an order of magnitude brings the disk and
halo masses to comparable values within the disk radius.


title:
One Parameter Solution of Spherically Symmetric Accretion in Various
  Pseudo-Schwarzschild Potentials

abstract:
  In this paper we have solved the hydrodynamic equations governing the
spherically symmetric isothermal accretion (wind) onto (away from) compact
objects using various pseudo-Schwarzschild potentials.These solutions are
essentially one parameter solutions in a sense that all relevant dynamical as
well as thermodynamic quantities for such a flow could be obtained (with the
assumption of a one-temperature fluid) if {\it only one} flow parameter
(temperature of the flow $T$) is given. Also we have investigated the transonic
behaviour of such a flow and showed that for a given $T$, transitions from
subsonic to the supersonic branch of accretion (wind) takes place at different
locations depending on the potentials used to study the flow and we have
identified these transition zones for flows in various such potentials.


title: Superbubble Activity in Star-Forming Galaxies

abstract:
  Mechanical feedback from massive stars, primarily from supernovae, can
dominate ISM structuring and phase balance, thereby profoundly affecting
galactic evolutionary processes. Our understanding of mechanical feedback is
based on the adiabatic, wind-driven bubble model, applied on size scales
ranging over three decades. Tests of the model, and our consequent
understanding of feedback, are reviewed. While the model is broadly successful,
critical unknowns still prevent a comprehensive understanding of the
consequences of feedback.


title: Discussion: Star Formation Within Galaxies

abstract:
  This Discussion session focused on star formation within galactic scales. We
attempt to identify the dominant physical processes and parameters that
characterize star formation, and to identify key questions that illuminate
these phenomena. The Discussion was delineated by the following cycle of three
questions: (A) Is the top of the HII LF physically distinct? (B) How does
massive star feedback affect the ISM and star formation? (C) How do ISM
properties affect the HII LF? Finally, is one of these three questions the
fundamental one of the cycle?
  Corresponding answers emerged from the Discussion: (A) The HII LF to date is
a continuous power law; (B) There are both positive and negative feedback
effects, which are poorly understood; (C) The HII LF appears remarkably
independent of ISM properties. Therefore, we suggest that the resultant
fundamental question is: ``Is the HII LF and parent stellar cluster membership
function universal?'' This is analogous to the related question of a universal
stellar IMF. Understanding the relationship, if any, between the IMF, cluster
membership function, and ISM properties may finally lead to a quantitative
theory of star formation.


title:
Low Noise Double-Sided Silicon Strip Detector for Multiple-Compton
  Gamma-ray Telescope

abstract:
  A Semiconductor Multiple-Compton Telescope (SMCT) is being developed to
explore the gamma-ray universe in an energy band 0.1--20 MeV, which is not well
covered by the present or near-future gamma-ray telescopes. The key feature of
the SMCT is the high energy resolution that is crucial for high angular
resolution and high background rejection capability. We have developed
prototype modules for a low noise Double-sided Silicon Strip Detector (DSSD)
system which is an essential element of the SMCT. The geometry of the DSSD is
optimized to achieve the lowest noise possible. A new front-end VLSI device
optimized for low noise operation is also developed. We report on the design
and test results of the prototype system. We have reached an energy resolution
of 1.3 keV (FWHM) for 60 keV and 122 keV at 0 degree C.


title:
Thermonuclear Supernovae: Simulations of the Deflagration Stage and
  Their Implications

abstract:
  Large-scale three-dimensional numerical simulations of the deflagration stage
of a thermonuclear supernova explosion show the formation and evolution of a
highly convoluted turbulent flame in a gravitational field of an expanding
carbon-oxygen white dwarf. The flame dynamics is dominated by the
gravity-induced Rayleigh-Taylor instability that controls the burning rate. The
thermonuclear deflagration releases enough energy to produce a healthy
explosion. The turbulent flame, however, leaves large amounts of unburnt and
partially burnt material near the star center, whereas observations imply these
materials only in outer layers. This disagreement could be resolved if the
deflagration triggers a detonation.


title: Relativistic Effects on the Appearance of a Clothed Black Hole

abstract:
  For an accretion disk around a black hole, the strong relativistic effects
affect every aspect of the radiation from the disk, including its spectrum,
light-curve, and image. This work investigates in detail how the images of a
thin disk around a black hole will be distorted, and what the observer will see
from different viewing angles and in different energy bands.


title: Gamma-ray emission from Outer-Gap of pulsar magnetosphere

abstract:
  We develop a model for gamma-ray emission from the outer magnetosphere of
pulsars (the outer-gap model). The charge depletion causes a large electric
field which accelerates electrons and positrons. We solve the electric field
with radiation and pair creation processes self-consistently, and calculate
curvature spectrum and Inverse-Compton (IC) spectrum. We apply this theory to
PSR B0833-45 (Vela) and B1706-44 for which their surface magnetic fields,
observed thermal X-rays are similar to each other. We find that each observed
cut-off energies of the gamma-rays are well explained. By inclusion of emission
outside the gap, the spectrum is in better agreement with the observations than
the spectrum arising only from the inside of the gap. The expected TeV fluxes
are much smaller than that observed by CANGAROO group in the direction of
B1706-44.


title:
Zero-metallicity stars II. Evolution of very massive objects with mass
  loss

abstract:
  We present evolutionary models of zero-metallicity very massive objects, with
initial masses in the range 120 Msun -- 1000 Msun, covering their quiescent
evolution up to central carbon ignition. In the attempt of exploring the
possible occurrence of mass loss by stellar winds, calculations are carried out
with recently-developed formalisms for the mass-loss rates driven by radiation
pressure (Kudritzki 2002) and stellar rotation (Maeder & Meynet 2000).The study
completes the previous analysis by Marigo et al. (2001) on the constant-mass
evolution of primordial stars. Our results indicate that radiation pressure
(assuming a minimum metallicity Z = 10^{-4} Zsun)is not an efficient driving
force of mass loss, except for very massive stars with M >= 750 Msun. On the
other hand, stellar rotation might play a crucial role in triggering powerful
stellar winds, once the (Omega-Gamma)-limit is approached. However, this
critical condition of intense mass loss can be maintained just for short, as
the loss of angular momentum due to mass ejection quickly leads to the spinning
down of the star. As by-product to the present work, the wind chemical yields
from massive zero-metallicity stars are presented. The helium and metal
enrichments, and the resulting Delta(Y)/Delta(Z) ratio are briefly discussed.


title: Carbon Chemistry in interstellar clouds

abstract:
  We discuss new developments of interstellar chemistry, with particular
emphasis on the carbon chemistry. We confirm that carbon chains and cycles are
ubiquitous in the ISM and closely chemically related to ea ch other, and to
carbon. Investigation of the carbon budget in shielded and UV illuminated gas
shows that the inventory of interstellar molecules is not complete and more
complex molecules with 4 or more carbon atoms must be present. Finally we
discuss the consequences for the evolution of clouds and conclude that the
ubiquitous presence of carbon chains and cycles is not a necessary consequence
of a very young age for interstellar clouds.


title:
Three-component Stackel potentials satisfying recent estimates of Milky
  Way parameters

abstract:
  We present a set of three-component Stackel potentials defined by five
parameters and designed to model the Milky Way. We review the fundamental
constraints that any model of the Milky Way must satisfy, including the most
recent ones derived from Hipparcos data, and we study how the parameters of the
presented potentials can vary in order to match these constraints. Five
different valid potentials are presented and analyzed in detail: they are
designed to be confronted with kinematical surveys in the future, by the
construction of three-integral analytic distribution functions.


title:
Thermodynamics of ionization and dissociation in hydrogen plasmas
  including fluctuations and magnetic fields

abstract:
  Applying Gibb's geometrical methods to the thermodynamics of H-plasmas we
explore the landscape of the free energy as a function of the degrees of
ionization and dissociation. Several approximations for the free energy are
discussed. We show that in the region of partial ionization/dissociation the
quantum Debye-Hueckel approximation (QDHA) yields a rather good but still
simple representation which allows to include magnetic field and fluctuation
effects. By using relations of Onsager-Landau-type the probability of
fluctuations and ionization/dissociation processes are described. We show that
the degrees of ionization/dissociation are probabilistic quantities which are
subject to a relatively large dispersion. Magnetic field effects are studied.


title:
Revision of the Selection Function of the Optical Redshift Survey using
  the Sloan Digital Sky Survey Early Data Release: Toward an Accurate Estimate
  of Source Number Density of Ultra-High Energy Cosmic Rays

abstract:
  If Ultra-High Energy Cosmic Rays (UHECRs) are originated from nearby
galaxies, modeling of the distribution of nearby galaxies is important to an
accurate estimate the source number density of UHECRs. We investigate
uncertainty of the selection function of the Optical Redshift Survey (ORS),
which we used to construct a source model of UHECRs. The investigation is based
on a comparison of numbe counts of ORS galaxies with those of the spectroscopic
sample of the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR). We
carefully count galaxies in the same absolute magnitude bin from the two
samples. We find a slight systematic overestimate of the ORS counts outside
5000 km s$^{-1}$ by about a factor of 2. We revise the selection function of
the ORS assuming that the SDSS counts are correct. Our revision is based on the
absorption given in the ORS catalog as well as that computed from Schlegel et
al. (1998), which is systematically larger than the former by $A_B \sim 0.1$
mag in the region of low absorption. It is found that introduction of Schlegel
et al.'s absorption changes one of the parameters of the ORS selection function
by more than 10%. The revision should be taken into account in the future
analysis of the source number density of UHECRs based on the ORS. Using the
revised selection function, we determine the global structure of the Local
Supercluster (LSC) with a source model of UHECRs, that is, a number-density
model consisting of a uniform spherical halo and an exponential disk. We find
that the revision is insignificant in terms of the structure of the LSC.
However, the revised selection function will be useful to other studies such as
peculiar velocity and correlation function.


title:
Equation of state and opacities for hydrogen atmospheres of neutron
  stars with strong magnetic fields

abstract:
  We present an equation of state and radiative opacities for a strongly
magnetized hydrogen plasma at magnetic fields B, temperatures T, and densities
\rho typical for atmospheres of isolated neutron stars. The first- and
second-order thermodynamic functions, monochromatic radiative opacities, and
Rosseland mean opacities are calculated and tabulated, taking account of
partial ionization, for 8x10^{11} G < B < 3x10^{13} G,
  2x10^5 K < T < 10^7 K, and a wide range of \rho. We show that bound-bound and
bound-free transitions give an important contribution to the opacities at T <
(1-5)x10^6 K in the considered range of B in the outer neutron-star atmosphere
layers, which may substantially modify the X-ray spectrum of a typical
magnetized neutron star. In addition, we re-evaluate opacities due to free-free
transitions, taking into account the motion of both interacting particles,
electron and proton, in a strong magnetic field. Compared to the previous
neutron-star atmosphere models, the free-free absorption is strongly suppressed
at photon frequencies below the proton cyclotron frequency.
  The latter result holds for any field strength, which prompts a revision of
existing theoretical models of X-ray spectra of magnetar atmospheres.
  Note added in v4: for free-free photoabsorption (Appendix B), equivalent but
much simpler expressions are available in Appendix B of Potekhin & Lai,
arXiv:astro-ph/0701285.


title: The linear MHD Taylor-Couette instability for liquid sodium

abstract:
  The linear stability of MHD Taylor-Couette flow of infinite vertical
extension is considered for liquid sodium with its small magnetic Prandtl
number Pm of order of 10^-5 and an uniform axial magnetic field. The sign of
the constant a in the basic rotation law \Omega=a+b/R^2 strongly influences the
presented results. It is negative for resting outer cylinder. The main point
here is that the subcritical excitation which occurs for large Pm disappears
for small Pm. This is the reason that the existence of the magnetorotational
instability remained unknown over decades. For rotating outer cylinder the
limiting case a=0 plays an exceptional role. The hydromagnetic instability
exists with certain Reynolds numbers at certain Hartmann numbers of the
magnetic field. These Reynolds numbers exactly scale with Pm^-1/2 resulting in
moderate values of order 10^4 for Pm=10^-5. However, already for the smallest
positive value of a the Reynolds numbers start to scale as 1/Pm leading to much
higher values of order 10^6 for Pm=10^-5. Also nonaxisymmetric modes have been
considered. With vacuum boundary conditions their excitation is always more
difficult than the excitation of axisymmetric modes; we never observed a
crossover of the lines of marginal stability. For conducting walls, however,
such crossovers exist for both resting and rotating outer cylinders, and this
might be essential for future dynamo experiments.


title:
Connection between PAHs and small hydrocarbons in the Horsehead Nebula
  Photo-Dissociation Region

abstract:
  We present recent observations of small hydrocarbons (C3H2, C2H, C4H) with
high abundances in the Photo-Dissociation Region of the Horsehead nebula. Our
results show for the first time observational indications that the small
hydrocarbon distribution follows the Aromatic Infrared Bands (AIBs) emission
traced by ISO-LW2 (5-8.5 microns), whereas it does not coincide with the CO and
isotopes large-scale distribution. The derived abundances are significantly
higher than in local clouds. This enhancement might be explained by an in situ
formation assisted by the release of carbonaceous molecules from UV-irradiated
aromatic particles.


title: Fluorescent iron lines as a probe of astrophysical black hole systems

abstract:
  (abridged) With most physicists and astrophysicists in agreement that black
holes do indeed exist, the focus of astrophysical black hole research has
shifted to the detailed properties of these systems. Nature has provided us
with an extremely useful probe of the region very close to an accreting black
hole - X-ray irradiation of relatively cold material in the vicinity of the
black hole can imprint characteristic features into the X-ray spectra of black
hole systems, most notably the Kalpha fluorescent line of iron. Detailed X-ray
spectroscopy of these features can be used to study Doppler and gravitational
redshifts, thereby providing key information on the location and kinematics of
the cold material. This is a powerful tool that allows us to probe within a few
gravitational radii, or less, of the event horizon. Here, we present a
comprehensive review of relativistic iron line studies for both accreting
stellar mass black holes (i.e., Galactic Black Hole Candidate systems; GBHCs),
and accreting supermassive black holes (i.e., active galactic nuclei; AGN).
After a pedagogical introduction to black hole astrophysics, we discuss studies
of relativistic iron lines in the AGN context and show how differences between
classes of AGN can be diagnosed using X-ray spectroscopy. Furthermore, through
a detailed discussion of one particular object (MCG--6-30-15), we illustrate
how the exotic physics of black hole spin are now open to observational study.
We proceed to discuss GBHCs, which turn out to possess rather more complicated
X-ray spectra, making robust conclusions more difficult to draw. However, even
in these cases, modern X-ray observatories are now providing convincing
evidence for relativistic effects. We conclude by discussing the science that
can be addressed by future X-ray observatories.


title:
UBVRI photopolarimetry of the long period eclipsing AM Herculis binary
  V1309

abstract:
  We report simultaneous UBVRI photo-polarimetric observations of the long
period (7.98 h) AM Her binary V1309 Ori. The length and shape of the eclipse
ingress and egress varies from night to night. We suggest this is due to the
variation in the brightness of the accretion stream. By comparing the phases of
circular polarization zero-crossovers with previous observations, we confirm
that V1309 Ori is well synchronized, and find an upper limit of 0.002 percent
for the difference between the spin and orbital periods. We model the
polarimetry data using a model consisting of two cyclotron emission regions at
almost diametrically opposite locations, and centered at colatitude 35 (deg)
and 145 (deg) on the surface of the white dwarf. We also present archive X-ray
observations which show that the negatively polarised accretion region is X-ray
bright.


title:
SPOrt: an Experiment Aimed at Measuring the Large Scale Cosmic Microwave
  Background Polarization

abstract:
  SPOrt (Sky Polarization Observatory) is a space experiment to be flown on the
International Space Station during Early Utilization Phase aimed at measuring
the microwave polarized emission with FWHM = 7deg, in the frequency range 22-90
GHz. The Galactic polarized emission can be observed at the lower frequencies
and the polarization of Cosmic Microwave Background (CMB) at 90 GHz, where
contaminants are expected to be less important. The extremely low level of the
CMB Polarization signal (< 1 uK) calls for intrinsically stable radiometers.
The SPOrt instrument is expressly devoted to CMB polarization measurements and
the whole design has been optimized for minimizing instrumental polarization
effects. In this contribution we present the receiver architecture based on
correlation techniques, the analysis showing its intrinsic stability and the
custom hardware development carried out to detect such a low signal.


title:
A New Prescription for Protogalactic Feedback and Outflows: Where Have
  All the Baryons Gone?

abstract:
  Up to half of the baryons inferred to once have been in our galaxy have not
yet been detected. Ejection would seem to provide the most attractive
explanation. Previous numerical studies may have underestimated the role of
winds. I propose a solution involving a multiphase model of the protogalactic
interstellar medium and the possibility of driving a superwind. Simulations do
not yet incorporate the small-scale physics that, I argue, drives mass-loading
of the cold phase gas and enhances the porosity, thereby ensuring that winds
are driven at a rate that depends primarily on the star formation rate.
  The occurrence of hypernovae, as claimed for metal-poor and possibly also for
starburst environments, and the possibility of a top-heavy primordial stellar
initial mass function are likely to have played important roles in allowing
winds to prevail in massive gas-rich starbursting protogalaxies as well as in
dwarfs. I discuss why such outflows are generically of order the rate of star
formation and may have been a common occurrence in the past.


title:
XMM observation of M~87 II. Abundance structure of the interstellar and
  intergalactic medium

abstract:
  Based on a detailed study of the temperature structure of the intracluster
medium in the halo of M~87, abundance profiles of 7 elements, O, Mg, Si, S, Ar,
Ca, and Fe are derived. In addition, abundance ratios are derived from the
ratios of line strengths, whose temperature dependences are small within the
temperature range of the ICM of M~87. The abundances of Si, S, Ar, Ca and Fe
show strong decreasing gradients outside 2$'$ and become nearly constant within
the radius at $\sim1.5$ solar. The Fe/Si ratio is determined to be 0.9 solar
with no radial gradient. In contrast, the O abundance is less than a half of
the Si abundance at the center and has a flatter gradient. The Mg abundance is
$\sim$1 solar within 2$'$, which is close to stellar abundance within the same
radius. The O/Si/Fe pattern of M~87 is located at the simple extension of that
of Galactic stars. The observed Mg/O ratio is about 1.25 solar, which is also
the same ratio as for Galactic stars. The O/Si/Fe ratio indicates that the SN
Ia contribution to Si and Fe becomes important towards the center and SN Ia
products have similar abundances of Si and Fe at least around M~87, which may
reflect dimmer SN Ia observed in old stellar systems. The S abundance is
similar to the Si abundance at the center, but has a steeper gradient. This
result suggests that the S/Si ratio of SN II products is much smaller than the
solar ratio.


title: XMM-Newton detection of warm/hot integalactic medium at z~0.01

abstract:
  We report a ~3 sigma detection of a 21.82 A absorption feature in the
direction of the BL Lac MRK 421 which is interpreted as OVII K(alpha) at
z~0.01. This corresponds to the redshift of a H absorber in a cosmic void
detected by HST along the line of sight of the same object. The 21.82 A line
proves the existence of warm/hot intergalactic medium (WHIM) outside the Local
Group, in agreement with current models of structure formation in the Universe.
The WHIM at z~0.01 has temperature <~(2.5-4)E6 K for gas densities in the range
1E-6 - 1 atom/cm3. We also detect OVII, OVIII and NeIX absorption lines with
zero velocity, possibly connected with WHIM in the Local Group.


title:
Determination of Primordial Metallicity and Mixing in the Type IIP
  Supernova 1993W

abstract:
  We present the results of a large grid of synthetic spectra and compare them
to early spectroscopic observations of SN 1993W. This supernova was discovered
close to its explosion date and at a recession velocity of 5400 km/s is located
in the Hubble flow. We focus here on two early spectra that were obtained
approximately 5 and 9 days after explosion. We parameterize the outer supernova
envelope as a power-law density profile in homologous expansion. In order to
extract information on the value of the parameters a large number of models was
required. We show that very early spectra combined with detailed models can
provide constraints on the value of the power law index, the ratio of hydrogen
to helium in the surface of the progenitor, the progenitor metallicity and the
amount of radioactive nickel mixed into the outer envelope of the supernova.
The spectral fits reproduce the observed spectra exceedingly well. The spectral
results combined with the early photometry predict that the explosion date was
4.7 \pm 0.7 days before the first spectrum was obtained. The ability to obtain
the metallicity from early spectra make SN IIP attractive probes of chemical
evolution in the universe and by showing that we have the ability to pin down
the parameters of the progenitor and mixing during the supernova explosion, it
is likely to make SN IIP useful cosmological distance indicators which are at
the same time complementary to SNe Ia.


title: High Latitude HI in NGC 2613: Buoyant Disk-Halo Outflow

abstract:
  We combine new VLA D array HI data of NGC 2613 with previous high resolution
data to show new disk-halo features in this galaxy. The global HI distribution
is modeled in detail using a technique which can disentangle the effects of
inclination from scale height and can also solve for the average volume density
distribution in and perpendicular to the disk. The model shows that the
galaxy's inclination is on the low end of the range given by Chaves & Irwin
(2001) and that the HI disk is thin (z_e = 188 pc), showing no evidence for
halo. Numerous discrete disk-halo features are observed, however, achieving z
heights up to 28 kpc from mid-plane. One prominent feature in particular, of
mass, 8X10^7 Msun and height, 22 kpc, is seen on the advancing side of the
galaxy at a projected galactocentric radius of 15.5 kpc. If this feature
achieves such high latitudes because of events in the disk alone, then input
energies of order ~ 10^{56} ergs are required. We have instead investigated the
feasibility of such a large feature being produced via buoyancy (with drag)
within a hot, pre-existing X-ray corona. Reasonable plume densities,
temperatures, stall height (~ 11 kpc), outflow velocities and ages can indeed
be achieved in this way. The advantage of this scenario is that the input
energy need only be sufficient to produce blow-out, a condition which requires
a reduction of three orders of magnitude in energy. If this is correct, there
should be an observable X-ray halo around NGC 2613.


title: HST observations of the metal rich globular clusters NGC6496 and NGC6352

abstract:
  Deep exposures of the metal-rich globular clusters NGC6496 and NGC6352 were
obtained with the WFPC2 camera on board the HST through the F606W and F814W
filters. The resulting colour-magnitude diagrams reach down to absolute
magnitude M_814~10-10.5, approximately 5 magnitudes below the main sequence
(MS) turn-off. The MS of the two clusters are sharp and well defined and their
fiducial lines overlap almost exactly throughout this range. Their colour is,
however, more than 0.1 mag redder than the MS fiducial line of the prototype
metal-rich globular cluster 47 Tuc, after proper correction for the relative
distances and reddening. This provides solid empirical evidence of a higher
metal content, which is not surprising if these objects belong indeed to the
bulge as their present location suggests. A good fit to the upper part of the
MS of both clusters is obtained with a 10 Gyr-old theoretical isochrone from
Baraffe et al. (1998) for a metallicity of [M/H]=-0.5, but at lower luminosity
all models depart considerably from the observations, probably because of a
deficiency in the treatment of the TiO opacity. The luminosity functions
obtained from the observed CMD are rather similar to one another and show a
peak at M_814~9. The present day mass functions (PDMF) are derived down to
m~0.2 Msolar and are consistent with power-law indices alpha=0.7 for NGC6496
and alpha=0.6 for NGC6352. The PDMF of 47 Tuc is twice as steep in the same
mass range (alpha=1.4). We investigate the origin of this discrepancy and show
that it can be understood if the two clusters contain a considerably higher
fraction of primordial binaries amongst their MS population, similar to that
expected in the bulge. We briefly discuss the implications of this finding on
the process of star and binary formation and on the universality of the IMF.


title: A Comprehensive Study of the L1551 IRS 5 Binary System

abstract:
  We model the Class I source L1551 IRS 5, adopting a flattened infalling
envelope surrounding a binary disk system and a circumbinary disk. With our
composite model, we calculate self-consistently the spectral energy
distribution of each component of the L1551 IRS 5 system, using additional
constraints from recent observations by ISO, the water ice feature from
observations with SpeX, the SCUBA extended spatial brightness distribution at
sub-mm wavelengths, and the VLA spatial intensity distributions at 7 mm of the
binary disks. We analyze the sensitivity of our results to the various
parameters involved. Our results show that a flattened envelope collapse model
is required to explain simultaneously the large scale fluxes and the water ice
and silicate features. On the other hand, we find that the circumstellar disks
are optically thick in the millimeter range and are inclined so that their
outer parts hide the emission along the line of sight from their inner parts.
We also find that these disks have lower mass accretion rates than the infall
rate of the envelope.


title:
Cosmological constraints from evolution of cluster baryon mass function
  at z~0.5

abstract:
  We present a new method for deriving cosmological constraints based on the
evolution of the baryon mass function of galaxy clusters, and implement it
using 17 distant clusters from our 160deg2 ROSAT survey. The method uses the
cluster baryon mass as a proxy for the total mass, thereby avoiding the large
uncertainties of the M_tot-T or M_tot-L_X relations used in all previous
studies. Instead, we rely on a well-founded assumption that the M_b/M_tot ratio
is a universal quantity, which should result in a much smaller systematic
uncertainty. Taking advantage of direct and accurate Chandra measurements of
the gas masses for distant clusters, we find strong evolution of the baryon
mass function between z>0.4 and the present. The observed evolution defines a
narrow band in the Omega_m-Lambda plane, Omega_m + 0.23Lambda = 0.41+-0.10 at
68% confidence, which intersects with constraints from the Cosmic Microwave
Background and supernovae Ia near Omega_m=0.3 and Lambda=0.7.


title: A Local One-Zone Model of MHD Turbulence in Dwarf Nova Disks

abstract:
  The evolution of the magnetorotational instability (MRI) during the
transition from outburst to quiescence in a dwarf nova disk is investigated
using three-dimensional MHD simulations. The shearing box approximation is
adopted for the analysis, so that the efficiency of angular momentum transport
is studied in a small local patch of the disk: this is usually referred as to a
one-zone model. To take account of the low ionization fraction of the disk, the
induction equation includes both ohmic dissipation and the Hall effect. We
induce a transition from outburst to quiescence by an instantaneous decrease of
the temperature. The evolution of the MRI during the transition is found to be
very sensitive to the temperature of the quiescent disk. As long as the
temperature is higher than a critical value of about 2000 K, MHD turbulence and
angular momentum transport is sustained by the MRI. However, MHD turbulence
dies away within an orbital time if the temperature falls below this critical
value. In this case, the stress drops off by more than 2 orders of magnitude,
and is dominated by the Reynolds stress associated with the remnant motions
from the outburst. The critical temperature depends slightly on the distance
from the central star and the local density of the disk.


title:
Atmospheres of Magnetized Neutron Stars: Vacuum Polarization and
  Partially Ionized Models

abstract:
  We construct hydrogen atmosphere models for magnetized neutron stars in
radiative equilibrium with surface fields B=10^12-5x10^14 G and effective
temperatures T_eff a few x 10^5-10^6 K by solving the full radiative transfer
equations for both polarization modes in the magnetized hydrogen plasma. The
atmospheres directly determine the characteristics of thermal emission from
isolated neutron stars. We study the effects of vacuum polarization and bound
atoms on the atmosphere structure and spectra. For the lower magnetic field
models (B 10^12 G), the spectral features due to neutral atoms lie at extreme
UV and very soft X-ray energies and therefore are not likely to be observed.
However, the continuum flux is also different from the fully ionized case,
especially at lower energies. For the higher magnetic field models, we find
that vacuum polarization softens the high energy tail of the thermal spectrum.
We show that this depression of continuum flux strongly suppresses not only the
proton cyclotron line but also spectral features due to bound species;
therefore spectral lines or features in thermal radiation are more difficult to
observe when the neutron star magnetic field is > 10^14 G.


title: Searching for Bulges at the End of the Hubble Sequence

abstract:
  We investigate the stellar disk properties of a sample of 19 nearby spiral
galaxies with low inclination and late Hubble type (Scd or later). We combine
our high-resolution HST I-band observations with existing ground-based optical
images to obtain surface brightness profiles that cover a high dynamic range of
galactic radius. Most of these galaxies contain a nuclear star cluster, as
discussed in a separate paper. The main goal of the present work is to
constrain the properties of stellar bulges at these extremely late Hubble
types. We find that the surface brightness profiles of the latest-type spirals
are complex, with a wide range in shapes. We have sorted our sample in a
sequence, starting with ``pure'' disk galaxies (approximately 30% of the
sample). These galaxies have exponential stellar disks that extend inwards to
within a few tens of pc from the nucleus, where the light from the nuclear
cluster starts to dominate. They appear to be truly bulge-less systems.
Progressing along the sequence, the galaxies show increasingly prominent
deviations from a simple exponential disk model on kpc scales. Traditionally,
such deviations have prompted ``bulge-disk'' decompositions. Indeed, the
surface brightness profiles of these galaxies are generally well fit by adding
a second (exponential) bulge component. However, we find that most surface
brightness profiles can be fit equally well (or better) with a single
Sersic-type R^{1/n} profile over the entire radial range of the galaxy, without
requiring a separate ``bulge'' component. We warn in a general sense against
identification of bulges solely on the basis of single-band surface brightness
profiles. (abridged)


title:
H2O- and OH-bearing minerals in the Martian regolith: Analysis of 1997
  observations from HST/NICMOS

abstract:
  We have analyzed observations of the Acidalia hemisphere of Mars taken by the
Hubble Space Telescope's Near-Infrared Camera Multi-Object Spectrograph
(HST/NICMOS) during July of 1997 (Ls = 152 degrees, northern Martian summer).
The data consist of images at ~60 km/pixel resolution, using both narrow- and
medium-band filters specifically selected to allow us to study the hydration
state of the Martian surface. Calibration was performed by comparison to
Phobos-2 ISM observations of overlapping regions, and atmospheric gas
correction was performed by modeling the atmosphere for each pixel using a
line-by-line radiative transfer code coupled with the MOLA altimetry data. Our
results indicate the presence of at least three spectrally different
large-scale (>1000 km diameter) terrains corresponding to the dark regions of
northern Acidalia, the southern hemisphere classical dark terrain, and the
classical intermediate terrain adjacent to southern Acidalia. We also
identified two other spectrally unique terrains, corresponding to the northern
polar ice cap, and to the southern winter polar hood. Comparisons with mineral
spectra indicate the possibility of different H2O- or OH-bearing (i.e.,
hydroxides and/or hydrates) minerals existing both in northern Acidalia and in
the nearby intermediate albedo terrain. Hydrated minerals do not appear to be
spectrally important components of the southern hemisphere dark terrains imaged
by HST in 1997.


title: Pulsar Searches of EGRET Sources

abstract:
  The majority of Galactic high-energy gamma-ray sources continue to elude
identification. Currently, we have a handful of firm pulsar identifications,
one of which is radio quiet, and a few marginal detections, including one
millisecond pulsar. Recently, both blind searches of EGRET error boxes and
targeted searches of X-ray counterpart candidates have had some success in
finding new pulsars. I review these results, and discuss our current program of
searching mid-Galactic latitude EGRET error boxes using the Parkes multi-beam
system.


title: The Inner Rings of Beta Pictoris

abstract:
  We present Keck images of the dust disk around Beta Pictoris at 17.9 microns
that reveal new structure in its morphology. Within 1" (19 AU) of the star, the
long axis of the dust emission is rotated by more than 10 degrees with respect
to that of the overall disk. This angular offset is more pronounced than the
warp detected at 3.5" by HST, and in the opposite direction. By contrast, the
long axis of the emission contours at ~ 1.5" from the star is aligned with the
HST warp. Emission peaks between 1.5" and 4" from the star hint at the presence
of rings similar to those observed in the outer disk at ~ 25" with HST/STIS. A
deconvolved image strongly suggests that the newly detected features arise from
a system of four non-coplanar rings. Bayesian estimates based on the primary
image lead to ring radii of 14+/-1 AU, 28+/-3 AU, 52+/-2 AU and 82+/-2 AU, with
orbital inclinations that alternate in orientation relative to the overall disk
and decrease in magnitude with increasing radius. We believe these new results
make a strong case for the existence of a nascent planetary system around Beta
Pic.


title: X-rays from the First Massive Black Holes

abstract:
  X-ray studies of high-redshift (z > 4) active galaxies have advanced
substantially over the past few years, largely due to results from the new
generation of X-ray observatories. As of this writing X-ray emission has been
detected from nearly 60 high-redshift active galaxies. This paper reviews the
observational results and their implications for models of the first massive
black holes, and it discusses future prospects for the field.


title:
Gravitational Leakage into Extra Dimensions: Probing Dark Energy Using
  Local Gravity

abstract:
  The braneworld model of Dvali-Gabadadze-Porrati (DGP) is a theory where
gravity is modified at large distances by the arrested leakage of gravitons off
our four-dimensional universe. Cosmology in this model has been shown to
support both "conventional" and exotic explanations of the dark energy
responsible for today's cosmic acceleration. We present new results for the
gravitational field of a clustered matter source on the background of an
accelerating universe in DGP braneworld gravity, and articulate how these
results differ from those of general relativity. In particular, we show that
orbits nearby a mass source suffer a universal anomalous precession as large as
5 microarcseconds/year, dependent only on the graviton's effective linewidth
and the global geometry of the full, five-dimensional universe. Thus, this
theory offers a local gravity correction sensitive to factors that dictate
cosmological history.


title: Deprojecting Densities from Angular Cross-Correlations

abstract:
  I present a model-independent spherically symmetric density estimator to be
used in the cross-correlation of imaging catalogs with objects of known
redshift. The estimator is a simple modification of the usual projected density
estimator, with weightings that produce a spherical aperture rather than a
cylindrical one.


title:
The overdensities of galaxy environments as a function of luminosity and
  color

abstract:
  We study the mean environments of galaxies in the Sloan Digital Sky Survey as
a function of rest-frame luminosity and color. Overdensities in galaxy number
are estimated in $8 h^{-1} \mathrm{Mpc}$ and $1 h^{-1} \mathrm{Mpc}$ spheres
centered on $125,000$ galaxies taken from the SDSS spectroscopic sample. We
find that, at constant color, overdensity is independent of luminosity for
galaxies with the blue colors of spirals. This suggests that, at fixed
star-formation history, spiral-galaxy mass is a very weak function of
environment. Overdensity does depend on luminosity for galaxies with the red
colors of early types; both low-luminosity and high-luminosity red galaxies are
found to be in highly overdense regions.


title:
Anomalous X-ray pulsars and soft gamma-ray repeaters - the connection
  with supernova remnants

abstract:
  Many of the properties of anomalous X-ray pulsars (AXPs) and soft gamma-ray
repeaters (SGRs) are still a matter of much debate, as is the connection (if
any) between these two groups of sources. In cases where we can identify the
supernova remnant (SNR) associated with an AXP or SGR, the extra information
thus obtained can provide important constraints as to the nature of these
exotic objects. In this paper, I explain the criteria by which an association
between a SNR and an AXP/SGR should be judged, review the set of associations
which result, and discuss the implications provided by these associations for
the ages, environments and evolutionary pathways of the AXPs and SGRs. There
are several convincing associations between AXPs and SNRs, demonstrating that
AXPs are young neutron stars with moderate space velocities. The lack of
associations between SGRs and SNRs implies that the SGRs either represent an
older population of neutron stars than do the AXPs, or originate from more
massive progenitors.


title: Average spectra of massive galaxies in the SDSS

abstract:
  We combine Sloan Digital Sky Survey spectra of 22,000 luminous, red,
bulge-dominated galaxies to get high S/N average spectra in the rest-frame
optical and ultraviolet (2600A to 7000A). The average spectra of these massive,
quiescent galaxies are early-type with weak emission lines and with absorption
lines indicating an apparent excess of alpha elements over solar abundance
ratios. We make average spectra of subsamples selected by luminosity,
environment and redshift. The average spectra are remarkable in their
similarity. What variations do exist in the average spectra as a function of
luminosity and environment are found to form a nearly one-parameter family in
spectrum space. We present a high signal-to-noise ratio spectrum of the
variation. We measure the properties of the variation with a modified version
of the Lick index system and compare to model spectra from stellar population
syntheses. The variation may be a combination of age and chemical abundance
differences, but the conservative conclusion is that the quality of the data
considerably exceeds the current state of the models.


title:
The Opacity of Nearby Galaxies from Counts of Background Galaxies: II.
  Limits of the Synthetic Field Method

abstract:
  Recently, we have developed and calibrated the Synthetic Field Method (SFM)
to derive the total extinction through disk galaxies. The method is based on
the number counts and colors of distant background field galaxies that can be
seen through the foreground object, and has been successfully applied to NGC
4536 and NGC 3664, two late-type galaxies located, respectively, at 16 and 11
Mpc. Here, we study the applicability of the SFM to HST images of galaxies in
the Local Group, and show that background galaxies cannot be easily identified
through these nearby objects, even with the best resolution available today. In
the case of M 31, each pixel in the HST images contains 50 to 100 stars, and
the background galaxies cannot be seen because of the intrinsic granularity due
to strong surface brightness fluctuations. In the LMC, on the other hand, there
is only about one star every six linear pixels, and the lack of detectable
background galaxies results from a ``secondary'' granularity, introduced by
structure in the wings of the point spread function. The success of the SFM in
NGC 4536 and NGC 3664 is a natural consequence of the reduction of the
intensity of surface brightness fluctuations with distance. When the dominant
confusion factor is structure in the PSF wings, as is the case of HST images of
the LMC, and would happen in M 31 images obtained with a 10-m diffraction-
limited optical telescope, it becomes in principle possible to improve the
detectability of background galaxies by subtracting the stars in the foreground
object. However, a much better characterization of optical PSFs than is
currently available would be required for an adequate subtraction of the wings.
Given the importance of determining the dust content of Local Group galaxies,
efforts should be made in that direction.


title: Accretion powered spherical wind in general relativity

abstract:
  Using full general relativistic calculations, we investigate the possibility
of generation of mass outflow from spherical accretion onto non-rotating black
holes. Introducing a relativistic hadronic-pressure-supported steady, standing,
spherically-symmetric shock surface around a Schwarzschild black hole as the
effective physical barrier that may be responsible for the generation of
spherical wind, we calculate the mass outflow rate $R_{\dot m}$ in terms of
three accretion parameters and one outflow parameter by simultaneously solving
the set of general relativistic hydrodynamic equations describing spherically
symmetric, transonic, polytropic accretion and wind around a Schwarzschild
black hole. Not only do we provide a sufficiently plausible estimation of
$R_{\dot m}$, we also successfully study the dependence and variation of this
rate on various physical parameters governing the flow. Our calculation
indicates that independent of initial boundary conditions, the baryonic matter
content of this shock-generated wind always correlates with post-shock flow
temperature.


title: Distance Determination of Variable Galactic Sources

abstract:
  We have developed a timing analysis method to determine the distances of
variable galactic X-ray sources based on the method advanced by Tr\"{u}mper and
Sch\"{o}nfelder in 1973. The light-curve of the halo produced by the scattering
of X-rays off the interstellar dust is delayed and smeared by the dust grains.
This method utilizes the differences between the power density spectra of the
point source and the halo. We present the details of this method and our first
applications of this method to the Chandra data of X-ray binary Cyg X-3.


title:
VLBA Continuum and H I Absorption Observations of the Ultra-Luminous
  Infrared Galaxy IRAS 17208-0014

abstract:
  We present phase-referenced VLBI observations of the radio continuum emission
from, and the neutral hydrogen 21 cm absorption toward, the Ultra-Luminous
Infrared Galaxy IRAS 17208-0014. The observations were carried out at 1362 MHz
using the Very Long Baseline Array, including the phased Very Large Array as an
element. The high-resolution radio continuum images reveal a nuclear starburst
region in this galaxy, which is composed of diffuse emission approximately 670
x 340 pc on the plane of the sky, and a number of compact sources. These
sources are most likely to be clustered supernova remnants and/or luminous
radio supernovae. Their brightness temperatures range over (2.2-6.6) x 10^{5}
K, with radio spectral luminosities between (1-10) x 10^{21} W Hz^{-1}. The
total VLBI flux density of the starburst region is ~52 mJy, which is about 50%
of the total flux density detected with the VLA at arcsecond resolution. For
this galaxy, we derive a massive star formation rate of ~84pm13 M{_\odot}
yr^{-1}, and a supernova rate of ~4pm1 yr^{-1}. H I absorption is detected in
multiple components with optical depths ranging between 0.3 and 2.5, and
velocity widths between 58 and 232 km s^{-1}. The derived column densities,
assuming T_{s}=100 K, range over (10-26) x 10^{21} cm^{-2}. The H I absorption
shows a strong velocity gradient of 453 km s^{-1} across 0.36 arcsec (274 pc).
Assuming Keplerian motion, the enclosed dynamical mass is about 2.3 x 10^9
sin^{-2}i M{_\odot}, comparable to the enclosed dynamical mass estimated from
CO observations.


title: An Imaging Survey of Early-Type Barred Galaxies

abstract:
  This paper presents the results of a high-resolution imaging survey, using
both ground-based and Hubble Space Telescope images, of a complete sample of
nearby barred S0--Sa galaxies in the field, with a particular emphasis on
identifying and measuring central structures within the bars: secondary bars,
inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the
frequency and statistical properties of the various types of inner structures
has already been published. Here, we present the data for the individual
galaxies and measurements of their bars and inner structures. We set out the
methods we use to find and measure these structures, and how we discriminate
between them. In particular, we discuss some of the deficiencies of ellipse
fitting of the isophotes, which by itself cannot always distinguish between
bars, rings, spirals, and dust, and which can produce erroneous measurements of
bar sizes and orientations.


title:
Kurucz model energy distributions: a comparison with real stars. II.
  Metal-deficient stars

abstract:
  Energy distributions of synthetic spectra for Kurucz model atmospheres are
compared with observed energy distributions of metal-deficient stars of the
blue horizontal-branch (BHB), F-G-K subdwarf (SD) and G-K giant (MDG) types.
The best coincidence of the synthetic and observed energy curves is found for
BHB stars. The largest differences are found in the ultraviolet wavelengths for
subdwarfs and cool MDGs. The influence of errors of effective temperatures,
gravities and metallicities is estimated.


title: Small-scale structure of the galactic cirrus emission

abstract:
  We examined the Fourier power spectrum characteristics of cirrus structures
in 13 sky fields with faint to bright cirrus emission observed with ISOPHOT in
the 90--200µm wavelength range in order to study variations of the
spectral index $\alpha$. We found that $\alpha$ varies from field to field with
--5.3 $\le$ $\alpha$ $\le$ --2.1. It depends on the absolute surface brightness
and on the hydrogen column density. We also found different spectral indices
for the same sky region at different wavelengths. Longer wavelength
measurements show steeper power spectra. This can be explained by the presence
of dust at various temperatures, in particular of a cold extended component.
For the faintest areas of the far-infrared sky we derive a wavelength
independent spectral index of $\alpha$ = --2.3$\pm$0.6 for the cirrus power
spectrum. The application of the correct spectral index is a precondition for
the proper disentanglement of the cirrus foreground component of the Cosmic
Far-Infrared Background and its fluctuations.


title: On Variation of the Latitudinal Structure of the Solar Convection Zone

abstract:
  The latitudinal sound-speed structure of the Sun's convection zone gives
insight into the physical processes occurring there, specifically the cellular
convection and possibly the presence of magnetic fields. Using helioseismic
data from the GONG network and MDI instrument on SOHO, we map the latitudinal
acoustic structure of the convection zone from 1995 to 2002. The temporally
averaged structure confirms previous findings of an excess in sound speed at
the $10^{-4}$ level at 60 degrees latitude. There also appear to be some
variations with time, with the peak in sound-speed asphericity at 60 degrees
growing towards the maximum of solar activity according to the MDI data.
However, we present some evidence that such variation may be associated with
instrumental variation between the epochs before and after SOHO was temporarily
lost in 1998. Nonetheless, some genuine temporal variation may be present, and
we discuss the possible physical causes of that.


title: Reduction of chemical networks. I. The case of molecular clouds

abstract:
  We present a new method to analyse and reduce chemical networks and apply
this technique to the chemistry in molecular clouds. Using the technique, we
investigated the possibility of reducing the number of chemical reactions and
species in the UMIST 95 database simultaneously. In addition, we did the same
reduction but with the ``objective technique'' in order to compare both
methods. We found that it is possible to compute the abundance of carbon
monoxide and fractional ionisation accurately with significantly reduced
chemical networks in the case of pure gas-phase chemistry. For gas-grain
chemistry involving surface reactions reduction is not worthwhile. Compared to
the ``objective technique'' our reduction method is more effective but more
time-consuming as well.


title: Cosmological parameters estimation in the Quintessence Paradigm

abstract:
  We present cosmological parameter constraints on flat cosmologies dominated
by dark energy using various cosmological data including the recent Archeops
angular power spectrum measurements. A likelihood analysis of the existing
Cosmic Microwave Background data shows that the presence of dark energy is not
requested, in the absence of further prior. This comes from the fact that there
exist degeneracies among the various cosmological parameters constrained by the
Cosmic Microwave Background. We found that there is a degeneracy in a
combination of the Hubble parameter H_0 and of the dark energy equation of
state parameter w_Q, but that w_Q is not correlated with the primordial index n
of scalar fluctuations and the baryon content Omega_b h^2. Preferred primordial
index is n = 0.95 \pm 0.05 (68%) and baryon content Omega_b h^2 = 0.021 \pm
0.003. Adding constraint on the amplitude of matter fluctuations on small
scales, sigma_8, obtained from clusters abundance or weak lensing data may
allow to break the degenaracies, although present-day systematics uncertainties
do not allow firm conclusions yet. The further addition of the Hubble Space
Telescope measurements of the local distance scale and of the high redshift
supernovae data allows to obtain tight constraints. When these constraints are
combined together we find that the amount of dark energy is 0.7^{+0.10}_{-0.07}
(95% C.L.) and that its equation of state is very close to those of the vacuum:
w_Q < -0.75 (> 95% C.L.). In no case do we find that quintessence is prefered
over the classical cosmological constant, although robust data on sigma_8 might
rapidly bring light on this important issue.


title:
Evolution of lithium beyond the solar age: a Li survey of the old open
  cluster NGC 188

abstract:
  We have determined Li abundances for 11 G-type stars in the 6-8 Gyr old open
cluster NGC 188. These data significantly enlarge the number of cluster stars
with Li measurements, allowing us to extend the investigation of Li depletion
in open clusters to ages well beyond the age of the Sun. We have also inferred
the cluster metallicity which turns out to be solar. We find that solar-type
stars in NGC 188 are only slightly more Li depleted than the much younger
Hyades and no more Li depleted than stars of similar temperature in the 2-4 Gyr
younger cluster M 67. At variance with M 67, NGC 188 members show virtually no
scatter in their Li abundances. Surprisingly, no solar- type star in NGC 188
appears as Li depleted as the Sun or as the most Li depleted stars in M 67. We
discuss the implications of these results for mechanisms of internal mixing and
Li depletion in main sequence stars.


title:
Discovery of a binary AGN in the ultraluminous infrared galaxy NGC 6240
  using Chandra

abstract:
  Ultraluminous infrared galaxies (ULIRGs) are outstanding due to their huge
luminosity output in the infrared, which is predominantly powered by super
starbursts and/or hidden active galactic nuclei (AGN). NGC 6240 is one of the
nearest ULIRGs and is considered a key representative of its class.
  Here, we report the first high-resolution imaging spectroscopy of NGC 6240 in
X-rays. The observation, performed with the ACIS-S detector aboard the Chandra
X-ray observatory, led to the discovery of two hard nuclei, coincident with the
optical-IR nuclei of NGC 6240. The AGN character of both nuclei is revealed by
the detection of absorbed hard, luminous X-ray emission and two strong neutral
Fe_K_alpha lines. In addition, extended X-ray emission components are present,
changing their rich structure in dependence of energy. The close correlation of
the extended emission with the optical Halpha emission of NGC 6240, in
combination with the softness of its spectrum, clearly indicates its relation
to starburst-driven superwind activity.


title: Brane universes tested against astronomical data

abstract:
  We discuss observational constrains coming from supernovae imposed on the
behaviour of the Randall-Sundrum models. The data indicates that, under the
assumption that we admit zero pressure dust matter on the brane, the
cosmological constant is still needed to explain current observations. The
observations from supernovae give a large value of the density parameter for
brane matter $\Omega_{\lambda,0} \simeq 0.01$ as the best fit. For high
redshifts $z > 1.2$, the difference between the brane model and the
$\Lambda$CDM (Perlmutter) model becomes detectable observationally. From the
maximum likelihood method we obtained the favored value of $\Omega_{\lambda,0}
= 0.004 \pm 0.016$ for $\Omega_{k,0}=0$ and $\Omega_{\mathrm{m},0}=0.3$. This
gives the limit $\Omega_{\lambda,0} < 0.02$ at $1 \sigma$ level. While the
model with brane effects is preferred by the supernovae type Ia data, the model
without brane fluid is still statistically admissible. For comparison the limit
on brane effects which comes from CMB anisotropies and BBN is also obtained.
The uncertainty in the location of the first peak gives a stronger limit
$\Omega_{\lambda,0} < 1.0 \cdot 10^{-12}$, whereas from BBN we obtain that
$\Omega_{\lambda,0} < 1.0 \cdot 10^{-27}$. However, both very strict limits are
obtained with the assumption that brane effects do not change the physics in
the pre-recombination era, while the SN Ia limit is model independent.We
demonstrate that the fit to supernovae data can also be obtained if we admit
the phantom matter $p = - (4/3) \varrho$ on the brane, where this matter mimics
the influence of the cosmological constant. Finally, we propose to check for
dark radiation and brane tension by the application of the angular diameter of
galaxies minimum value test.


title:
A Mass for the Extrasolar Planet Gl 876b Determined from Hubble Space
  Telescope Fine Guidance Sensor 3 Astrometry and High-Precision Radial
  Velocities

abstract:
  We report the first astrometrically determined mass of an extrasolar planet,
a companion previously detected by Doppler spectroscopy. Radial velocities
first provided an ephemeris with which to schedule a significant fraction of
the {\it HST} observations near companion peri- and apastron. The astrometry
residuals at these orbital phases exhibit a systematic deviation consistent
with a perturbation due to a planetary mass companion. Combining {\it HST}
astrometry with radial velocities, we solve for the proper motion, parallax,
perturbation size, inclination, and position angle of the line of nodes, while
constraining period, velocity amplitude, longitude of periastron, and
eccentricity to values determined from radial velocities. We find a
perturbation semi-major axis and inclination, $\alpha$ = 0.25 $\pm$ 0.06 mas,
$i$ = 84\arcdeg $\pm$6\arcdeg, and Gl 876 absolute parallax, $\pi_{abs}= 214.6
\pm$ 0.2 mas. Assuming that the mass of the primary star is $M_* =
0.32M_{\sun}$, we find the mass of the planet, Gl 876b, $M_b =
1.89\pm0.34M_{Jup}$.


title:
Simulating Observations of Dark Matter Dominated Galaxies: Towards the
  Optimal Halo Profile

abstract:
  Low Surface Brightness (LSB) galaxies are dominated by dark matter, and their
rotation curves thus reflect their dark matter distribution. Recent
high-resolution rotation curves suggest that their dark matter mass-density
distributions are dominated by a constant-density core. This seems inconsistent
with the predictions of Cold Dark Matter (CDM) models which produce halos with
compact density cusps and steep mass-density profiles. However, the
observationally determined mass profiles may be affected by non-circular
motions, asymmetries and offsets between optical and dynamical centres, all of
which tend to lower the observed slopes. Here we determine the impact of each
of these effects on a variety of halo models, and compare the results with
observed mass-density profiles. Our simulations suggest that no single
systematic effect can reconcile the data with the cuspy CDM halos. The data are
best described by a model with a soft core with an inner power-law mass-density
slope alpha = -0.2 +/- 0.2. However, no single universal halo profile provides
a completely adequate description of the data.


title:
Ultra High Energy Cosmic Rays: Strangelets? -- Extra dimensions,
  TeV-scale black holes and strange matter

abstract:
  The conjecture that ultra high energy cosmic rays (UHECRs) are actually
strangelets is discussed. Besides the reason that strangelets can do as cosmic
rays beyond the GZK-cutoff, another argument to support the conjecture is
addressed in this letter via the study of formation of TeV-scale microscopic
black holes when UHECRs bombarding bare strange stars. It is proposed that the
exotic quark surface of a bare strange star could be an effective
astro-laboratory in the investigations of the extra dimensions and of the
detection of ultra-high energy neutrino fluxes. The flux of neutrinos (and
other point-like particles) with energy >2.3 x 10^{20} eV could be expected to
be smaller than 10^{-26} cm^{-2}$ s^{-1} if there are two extra spatial
dimensions.


title: Gas in Groups and Clusters of Galaxies

abstract:
  Groups and clusters contain a large fraction of hot gas which emits X-ray
radiation. This gas yields information on the dynamical state and on the total
mass of these systems. X-ray spectra show that heavy elements are present in
the gas. As these metals must have been produced in the cluster/group galaxies
and later transported into the gas, the metallicity is a good tracer for the
transport processes. Several possible processes, that transport gas from the
small potential wells of the galaxies into the clusters and groups, are
discussed.


title:
Time-Dependent Photoionization in a Dusty Medium. III: The effect of
  dust on the photoionization of metals

abstract:
  We use the time-dependent photoionization and dust destruction code developed
by Perna & Lazzati (2002) to study the time evolution of the medium in a dusty
gaseous cloud illuminated by a bright central source that sets on at time zero.
We study the case of a bright source, which lasts for a time scale much smaller
than the recombination and dust creation time scales. For this reason an
equilibrium is never reached. We show that the presence of dust and its
properties, such as its composition, can have a big effect on the time scale
for the evaporation of the soft X-ray absorption, in particular for ionizing
sources with hard spectra. We discuss the profile of evaporation of the soft
X-ray absorbing column, as well as how the apparent ionization state of the
cloud evolves in time. We finally consider the apparent metallicity of the
cloud that is left behind as a function of the cloud and ionizing source
properties.