title:
Evidence for anisotropic motion of the clouds in broad-line regions of
  BL Lacertae objects

abstract:
  The masses of central massive black holes in BL Lac objects are estimated
from their host galaxy absolute magnitude at R-band by using the empirical
relation between absolute magnitude of host galaxy and black hole mass. Only a
small fraction of BL Lac objects exhibit weak broad-line emission, and we
derive the sizes of the broad-line regions (BLRs) in these BL Lac objects from
the widths of their broad emission lines on the assumption of the clouds being
virilized in BLRs. It is found that the sizes of the BLRs in these sources are
usually 2-3 orders of magnitude larger than that expected by the empirical
correlation between BLR size and optical luminosity defined by a sample of
Seyfert galaxies and quasars. We discuss a variety of possibilities and suggest
it may probably be attributed to anisotropic motion of the BLR clouds in these
BL Lac objects. If the BLR geometry of these sources is disk-like, the viewing
angles between the axis and the line of sight are in the range of 2-12 degrees,
which is consistent with the unification schemes.


title:
Integrated Spectral Energy Distributions and Absorption Feature Indices
  of Single Stellar Populations

abstract:
  Using evolutionary population synthesis, we present integrated spectral
energy distributions and absorption-line indices defined by the Lick
Observatory image dissector scanner (referred to as Lick/IDS) system, for an
extensive set of instantaneous burst single stellar populations (SSPs). The
ages of the SSPs are in the range 1-19 Gyr and the metallicities [Fe/H] are in
the range -2.3 - 0.2. Our models use the rapid single stellar evolution
algorithm of Hurley, Pols and Tout for the stellar evolutionary tracks, the
empirical and semi-empirical calibrated BaSeL-2.0 model of Lejeune, Cuisinier
and Buser for the library of stellar spectra and the empirical fitting
functions of Worthey, Faber, Gonzalez and Burstein for the Lick/IDS spectral
absorption-feature indices.
  Applying our synthetic Lick/IDS absorption-line indices to the merit
function, we obtain the age and the metallicity of the central region of M32,
which can be well explained by an instantaneous SSP with an age of 6.5 Gyr and
a metallicity similar to solar. Applying the derived age and the metallicity
from the merit function to a number of index-index diagrams, we find that the
plots of Hbeta-Fe5015 and Hbeta-Fe5782 are the best index-index diagrams from
which we can directly obtain reasonable age and metallicity.


title: The Pionic Contribution to Diffuse Gamma Rays: Upper Limits

abstract:
  Diffuse gamma rays probe the highest-energy processes at the largest scales.
Here we derive model-independent constraints on the hadronic contribution to
the Galactic and extragalactic gamma-ray spectra in the energy range 50 MeV <
E_gamma < 10 GeV. The hadronic component is dominated by emission from neutral
pions, with a characteristic spectrum symmetric about m_{pi^0}/2. We exploit
the well-defined properties of the pion decay spectrum to quantify the maximum
pionic fraction of the observed gamma-ray intensity. We find that the Galactic
spectrum above 30 MeV can be at most about 50% pionic. The maximum pionic
contribution to the extragalactic spectrum is energy dependent; it also depends
on the redshift range over which the sources are distributed, ranging from as
low as about 20% for pions generated very recently, to as much as 90% if the
pions are generated around redshift 10. The implications of these constraints
for models of gamma-ray and neutrino emission are briefly discussed.


title: Optical and near-IR observations of SN 1998bw

abstract:
  SN 1998bw, especially after the discovery of GRB 030329/SN 2003dh, seems to
be the equivalent of the Rosetta stone for the SN/GRB connection. In this paper
I review optical and near IR observations that have been carried out for this
uncanny object, which has probably confirmed suspicions and ideas originally
formulated in the early seventies of last century.


title:
High resolution spectroscopy of Brown Dwarfs in Taurus: Detection of
  accretion in KPNO Tau 3

abstract:
  We present high resolution optical spectroscopy of three candidate members of
the Taurus-Auriga star forming region. Based on the spectral type, the
strength, profile and width of the H(alpha) line, the detected lithium at 6708
angstrom, the location of these objects in a H-R diagram and the comparison
with similar objects belonging to young stellar associations, we determine that
they are bona fide members of the SFR, with about ~3 Myr, have masses at or
below the substellar limit and, at least in one case, there is active accretion
from a circum(sub)stellar disk. This result suggests that high mass brown
dwarfs go through a Classical TTauri phase and form like stars, from colapse
and fragmentation of a molecular cloud.


title:
XMM-Newton observation of the young open cluster Blanco 1. I. X-ray
  spectroscopy and photometry

abstract:
  We present an X-ray study of the high metallicity young open cluster Blanco 1
based on XMM--Newton data. X-ray spectroscopy of cluster members is presented
for the first time as well as new X-ray distribution functions of late-type
stars. We detected all known dF and dG stars in the EPIC field and 80% and 90%
of dK and dM stars, respectively. The X-ray spectral analysis of the X-ray
brightest cluster stars and X-ray color analysis of a larger sample show that a
model with two temperatures (at about 0.3 and 1 keV) explains the quiescent
activity phase spectra. We discuss also the nature of unidentified X-ray
sources in the observed region and their X-ray spectral properties.


title: X-ray source populations in the Galactic Plane

abstract:
  We present the first results from the \xmm Galactic Plane Survey (XGPS). In
the first phase of the programme, 22 pointings were used to cover a region of
approximately three square degrees between 19\deg -- 22\deg in Galactic
longitude and $\pm$0.6\deg in latitude. In total we have resolved over 400
point X-ray sources, at $\geq 5 \sigma$ significance, down to a flux limit of
$\sim2 \times 10^{-14}$ \ergseccm (2--10 keV). The combination of the XGPS
measurements in the hard X-ray band with the results from earlier surveys
carried out by \asca and \chan reveals the form of the low-latitude X-ray
source counts over 4 decades of flux. It appears that extragalactic sources
dominate below $\sim10^{-13}$ \ergseccm (2--10 keV), with a predominantly
Galactic source population present above this flux threshold. The nature of the
faint Galactic population observed by \xmm remains uncertain, although
cataclysmic variables and RS CVn systems may contribute substantially. \xmm
observes an enhanced surface brightness in the Galactic plane in the 2--6 keV
band associated with Galactic Ridge X-ray Emission (GRXE). The integrated
contribution of Galactic sources plus the breakthrough of extragalactic signal
accounts for up to 20 per cent of the observed surface brightness. The XGPS
results are consistent with the picture suggested from a deep \chan observation
in the Galactic plane, namely that the bulk of the GRXE is truly diffuse.


title: Generalized Chaplygin Gas Models tested with SNIa

abstract:
  The so called Generalized Chaplygin Gas (GCG) with the equation of state $p =
- \frac{A}{{\rho}^{\alpha}}$ was recently proposed as a candidate for dark
energy in the Universe. In this paper we confront the GCG with SNIa data.
Specifically we have tested the GCG cosmology in three different classes of
models with (1) $\Omega_m= 0.3$, $\Omega_{Ch}= 0.7$; (2) $\Omega_m= 0.05$,
$\Omega_{Ch}= 0.95$ and (3) $\Omega_m = 0$, $\Omega_{Ch} = 1$, as well as the
model withouth any assumption on $\Omega_m$. The best fitted models are
obtained by minimalizing the $\chi^2$ function and $\chi^2$ levels in the
$(A_0, \alpha)$ plane. We supplemented our analysis with confidence intervals
in the $(A_0, \alpha)$ plane, as well as one-dimensional probability
distribution functions for models parameter. The general conclusion is that
SNIa data strongly support the Chaplygin gas (with $\alpha = 1$). Extending our
analysisby relaxing the flat prior lead to the result that even though the best
fitted values of $\Omega_k$ are formally non-zero, still they are close to flat
case. It should be viewed as an advantage of the GCG model since in similar
analysisof $\Lambda$CDM model high negative value of $\Omega_{k}$ were found to
be bestfitted to the data and independent inspiration from CMBR and
extragalactic astronomy has been invoked to fix the curvature problem. Our
results show clearly that in Generalized Chaplygin Gas cosmology distant $z >1$
supernovae should be brighter than in $\Lambda$CDM model.This prediction seems
to be confirmed with new Riess high redshift SNIa sample. Moreover, we argue
that with the future SNAP data it would be possible to differentiate between
models with various value of $\alpha$ parameter and/or discriminated between
GCG, Cardassian and $\Lambda$CDM models


title: Long-term evolution of compact binaries with irradiation feedback

abstract:
  We resume the discussion about irradiation-driven mass transfer cycles in
semi- detached compact binary systems. The analytical model that describes the
onset of these cycles, which occur on a thermal timescale of the donor star, is
reexamined. We take into account a contribution of the thermal relaxation which
is not related to the irradiation of the donor star and which was neglected in
previous studies. Cataclysmic variables (CVs) containing extended giant donors
are more stable than previously thought. CVs close to the upper edge of the
period gap can undergo cycles for low angular momentum loss rates, as they have
been suggested by recent magnetic braking prescriptions, while they are stable
for high braking rates. A model for the irradiation geometry that takes into
account surface elements near the terminator of the donor star indicates that
possibly also low-mass X-ray binaries (LMXBs) can undergo mass transfer cycles.
Regarding the braking rate, which is necessary to drive cycles, basically the
same restrictions apply for short period LMXBs as they do for short period CVs.
We confirm that LMXBs containing giants can undergo cyles. In terms of an
irradiation efficiency parameter \alpha CVs are susceptible to the irradiation
instability for \alpha >= 0.1 while LMXBs are susceptible for \alpha <= 0.1.
The predictions of the analytical model are checked by the first long-term
evolutionary computations of systems undergoing mass transfer cycles with full
1D stellar models. For unevolved main sequence (MS) and giant donors the
analytic model provides reasonable values for the boundaries of the stable and
unstable regions while CVs containing highly evolved MS donors are more stable
at high braking rates than expected.Taking into account irradiation the minimum
period of CVs is increased by up to 1-2 minutes, depending on \alpha.


title:
Unequal-mass galaxy merger remnants: spiral-like morphology but
  elliptical-like kinematics

abstract:
  It is generally believed that major galaxy mergers with mass ratios in the
range 1:1-3:1 result in remnants that have properties similar to elliptical
galaxies, and minor mergers below 10:1 result in disturbed spiral galaxies. The
intermediate range of mass ratios 4:1-10:1 has not been studied so far. Using
N-body simulations, we show that such mergers can result in very peculiar
systems, that have the morphology of a disk galaxy with an exponential profile,
but whose kinematics is closer to that of elliptical systems. These objects are
similar to those recently observed by Jog & Chitre (2002). We present two cases
with mass ratios 4.5:1 and 7:1, and show that the merging causes major heating
and results in the appearance of elliptical-type kinematics, while surprisingly
the initial spiral-like mass profile is conserved.


title: A polarized synchrotron template for CMBP experiments after WMAP data

abstract:
  We build template maps for the polarized Galactic--synchrotron emission on
large angular scales (FWHM =~7$^\circ$), in the 20-90 GHz microwave range, by
using WMAP data. The method, presented in a recent work, requires a synchrotron
total intensity survey and the {\it polarization horizon} to model the
polarized intensity and a starlight polarization map to model polarization
angles. The basic template is obtained directly at 23 GHz with about 94%
sky--coverage by using the synchrotron map released by the WMAP team.
Extrapolations to 32, 60 and 90 GHz are performed by computing a synchrotron
spectral index map, which strongly reduces previous uncertainties in passing
from low (1.4 GHz) to microwave frequencies. Differing from low frequency data,
none of our templates presents relevant structures out of the Galactic Plane.
Our map at 90 GHz suggests that the synchrotron emission at high Galactic
latitudes is low enough to allow a robust detection of the $E$--mode component
of the cosmological signal on large--scale, even in models with
low--reionization ($\tau = 0.05$). Detection of the weaker $B$--mode on the
largest scales ($\ell < 10$) might be jeopardized unless the value $\tau =
0.17$ found by WMAP is confirmed, and $T/S > 0.1$. For lower levels of the
gravitational--wave background the $B$--mode seems to be accessible only at the
$\ell \sim 100$ peak and in selected low--synchrotron emission areas.


title:
Discovery of [FeII]- and H2-emission from protostellar jets in the CB3
  and CB230 globules

abstract:
  Four Bok globules were studied in the Near-Infrared, through narrow-band
filters, centered at the 1.644 micron line of [FeII], the H2-line at 2.122
micron, and the adjacent continuum. We report the discovery of [FeII] and H2
protostellar jets and knots in the globules CB3 and CB230. The [FeII]-jet in
CB230 is defined by a continuous elongated emission feature, superimposed on
which two knots are seen; the brighter one lies at the tip of the jet. The jet
is oriented in the same direction as the large-scale CO outflow, and emerges
from the nebulosity in which a Young Stellar Object is embedded. The H2
emission associated with this jet is fainter and wider than the [FeII]
emission, and is likely coming from the walls of the jet-channel. In CB3 four
H2 emission knots are found, all towards the blue-shifted lobe of the
large-scale outflow. There is a good correspondence between the location of the
knots and the blue-shifted SiO(5-4) emission, confirming that SiO emission is
tracing the jet-like flow rather well. No line emission is found in the other
two targets, CB188 and CB205, although in CB205 faint line emission may have
been hidden in the diffuse nebulosity near the IRAS position. Around this
position a small group of (> 10) stars is found, embedded in the nebula. A
diffuse jet-like feature near this group, previously reported in the
literature, has been resolved into individual stars.


title: Challenges to the Generalized Chaplygin Gas Cosmology

abstract:
  The generalized Chaplygin gas (GCG) model allows for an unified description
of the cosmologically recent accelerated expansion of the Universe and of the
evolution of energy density perturbations. This dark energy - dark matter
unification is achieved through a rather exotic background fluid whose equation
of state is given by $p = - A/\rho^{\alpha}$, where $A$ is a positive constant.
Observational constraints arising from bounds on the locations of the first few
peaks and troughs of the Cosmic Microwave Background Radiation (CMBR) power
spectrum from recent WMAP and BOOMERanG experiments are consistent with the
model for $\alpha \lsim 0.6$ assuming that $0 < \alpha \le 1$. Most recent
Type-Ia Supernova data indicates however, that the range $\alpha > 1 $ must be
considered.


title: OH spectral evolution of oxygen-rich late-type stars

abstract:
  We investigated the main-line spectral evolution with shell thickness of
oxygen rich AGB stars. The study is based on a sample of 30 sources distributed
along the IRAS colour-colour diagram. The sources were chosen to trace the
Miras with thick shells and the whole range of OH/IR stars. The Miras exhibit a
1665 MHz emission strength comparable to that at 1667 MHz. Even though the
Miras of the study have quite thick shells, their spectral characteristics in
both main lines attest to a strong heterogeneity in their OH shell with, in
particular, the presence of significant turbulence and acceleration. The
expansion velocity has been found to be about the same at 1665 and 1667 MHz,
taking into account a possible velocity turbulence of 1-2km/s at the location
of the main-line maser emission. An increase in the intensity ratio 1667/1665
with shell thickness has been found. A plausible explanation for such a
phenomenon is that competitive gain in favour of the 1667 MHz line increases
when the shell is getting thicker. There is an evolution in the spectral
profile shape with the appearance of a substantial inter-peak signal when the
shell is getting thicker. Also, inter-peak components are found and can be as
strong as the external standard peaks when the shell is very thick. This trend
for an increase of the signal in between the two main peaks is thought to be
the result of an increase of the saturation with shell thickness. All sources
but two - a Mira and an OH/IR star from the lower part of the colour-colour
diagram - are weakly polarized. The strong polarization observed for those two
particular objects is thought to be the result of perturbations in their
shells.


title:
On the Dynamical Stability of Gamma Cephei, an S-Type Binary Planetary
  System

abstract:
  Precision radial velocity measurements of the Gamma Cephei (HR8974) binary
system suggest the existence of a planetary companion with a minimum mass of
1.7 Jupiter-mass on an elliptical orbit with a ~2.14 AU semimajor axis and 0.12
eccentricity (hatzes et al. 2003). I present in this paper a summary of the
results of an extensive numerical study of the orbital stability of this
three-body system for different values of the semimajor axis and orbital
eccentricity of the binary, and also the orbital inclination of the planet.
Numerical integrations indicate that the system is stable for the planet's
orbital inclination ranging from 0 to 60 degrees, and for the binary's orbital
eccentricity less than 0.5. The results also indicate that for large values of
the inclination, the system may be locked in a Kozai resonance.


title:
An X-ray Search for Compact Central Sources in Supernova Remnants I:
  SNRs G093.3+6.9, G315.4-2.3, G084.2+0.8, & G127.1+0.5

abstract:
  Less than half of the SNRs within 5 kpc have identified central sources, and
only three are identified as the remnants of Type Ia SNe. Here, we report a
systematic effort to search for compact central sources in the remaining 23
SNRs of this distance limited sample.
  In this first paper we report Chandra observations of four SNRs. We have
undertaken a systematic optical/IR identification program of the X-ray sources
detected in the field of each SNR. Foreground and background sources have
identifiable IR/optical counterparts, while the counterparts of neutron stars
(or black holes) are expected to be very faint. We are able to account for all
the well-detected X-ray sources and thus able to state with some confidence
that there are no associated central sources down to a level of one tenth of
that of the Cas A central source, L_X <~ 10e31 ergs/s. We compare our limits
with cooling curves for neutron stars and find that any putative neutron stars
in these SNRs must be cooling faster than expected for traditional 1.35 Mo
neutron stars and that any putative pulsar must have low spin-down
luminosities, Edot <~ 1e34 ergs/s. However, our limits are unable to constrain
the presence or absence of more unusual options, such as relatively more
massive neutron stars, neutron stars with exotic interiors, or quiescent black
holes. In subsequent papers, we will report on the X-ray and optical/IR
observations of the remaining members of the 5-kpc sample.


title:
The Distribution of Quasars and Galaxies in Radio Color-Color and
  Morphology Diagrams

abstract:
  We positionally match the 6 cm GB6, 20 cm FIRST and NVSS, and 92 cm WENSS
radio catalogs and find 16,500 matches in ~3,000 deg2 of sky. Using this
unified radio database, we construct radio "color-magnitude-morphology"
diagrams and find that they display a clear structure, rather than a random
scatter. We propose a simple, yet powerful, method for morphological
classification of radio sources based on FIRST and NVSS measurements. For a
subset of matched sources, we find optical identifications using the SDSS Data
Release 1 catalogs, and separate them into quasars and galaxies. Compact radio
sources with flat radio spectra are dominated by quasars, while compact sources
with steep spectra, and resolved radio sources, contain substantial numbers of
both quasars and galaxies.


title: Modulated fluctuations from hybrid inflation

abstract:
  Inflation universally produces classical almost scale free Gaussian
inhomogeneities of any light scalars. Assuming the coupling constants at the
time of inflation depend on some light moduli fields, we encounter the
generation of modulated cosmological fluctuations from (p)reheating. This is an
alternative mechanism to generate observable (almost) scale free adiabatic
metric perturbations. We extend this idea to the class of hybrid inflation,
where the bifurcation value of the inflaton is modulated by the spatial
inhomogeneities of the couplings. As a result, the symmetry breaking after
inflation occurs not simultaneously in space but with the time laps in
different Hubble patches inherited from the long-wavelength moduli
inhomogeneities. To calculate modulated fluctuations we introduce techniques of
general relativistic matching conditions for metric perturbations at the time
hypersurface where the equation of state after inflation undergoes a jump,
without evoking the detailed microscopic physics, as far as it justifies the
jump. We apply this theory to the modulated fluctuations from the hybrid and
chaotic inflations. We discuss what distinguish the modulated from the
inflation-driven fluctuations, in particular, their spectral index,
modification of the consistency relation and the issue of weak non-Gaussianity.


title: Magnetoelliptic Instabilities

abstract:
  We consider the stability of a configuration consisting of a vertical
magnetic field in a planar flow on elliptical streamlines in ideal
hydromagnetics. In the absence of a magnetic field the elliptical flow is
universally unstable (the ``elliptical instability''). We find this universal
instability persists in the presence of magnetic fields of arbitrary strength,
although the growthrate decreases somewhat. We also find further instabilities
due to the presence of the magnetic field. One of these, a destabilization of
Alfven waves, requires the magnetic parameter to exceed a certain critical
value. A second, involving a mixing of hydrodynamic and magnetic modes, occurs
for all magnetic-field strengths. These instabilities may be important in
tidally distorted or otherwise elliptical disks. A disk of finite thickness is
stable if the magnetic fieldstrength exceeds a critical value, similar to the
fieldstrength which suppresses the magnetorotational instability.


title: Observations of Non-radial Pulsations in Radio Pulsars

abstract:
  We introduce a model for pulsars in which non-radial oscillations of high
spherical degree (l) aligned to the magnetic axis of a spinning neutron star
reproduce the morphological features of pulsar beams. In our model, rotation of
the pulsar carries a pattern of pulsation nodes underneath our sightline,
reproducing the longitude stationary structure seen in average pulse profiles,
while the associated time-like oscillations reproduce "drifting
subpulses"--features that change their longitude between successive pulsar
spins. We will show that the presence of nodal lines can account for observed
180 degree phase jumps in drifting subpulses and their otherwise poor phase
stability, even if the time-like oscillations are strictly periodic. Our model
can also account for the "mode changes" and "nulls" observed in some pulsars as
quasiperiodic changes between pulsation modes of different l or radial overtone
n, analogous to pulsation mode changes observed in oscillating white dwarf
stars. We will discuss other definitive and testable requirements of our model
and show that they are qualitatively supported by existing data. While
reserving judgment until the completion of quantitative tests, we are inspired
enough by the existing observational support for our model to speculate about
the excitation mechanism of the non-radial pulsations, the physics we can learn
from them, and their relationship to the period evolution of pulsars.


title:
Abundances in Planetary Nebulae An Autopsy of Low and Intermediate Mass
  Stars

abstract:
  In this work I report on the results of synthetic thermally pulsing
asymptotic giant branch models (TP-AGB) and compare the results to the
abundance ratios in a sample of planetary nebulae. I use updated input
parameters for mass-loss, the stellar luminosity, and dredge-up. I calculated
models with masses between 0.8 solar masses and 8.0 solar masses. I also
calculated models with [Fe/H] between -2.5 and 0.3. The effects of the first,
second, third dredge-ups and hot-bottom burning are reported on. Models of the
planetary nebula in M15 are reported on. The analysis of samples of Galactic
bulge and disk nebulae are also reported.


title:
Variable Faint Optical Sources Discovered by Comparing POSS and SDSS
  Catalogs

abstract:
  We present a study of variable faint optical sources discovered by comparing
the Sloan Digital Sky Survey (SDSS) and the Palomar Observatory Sky Survey
(POSS) catalogs. We use SDSS measurements to photometrically recalibrate
several publicly available POSS catalogs; a piecewise recalibration in 100
arcmin2 patches generally results in an improvement of photometric accuracy
(rms) by nearly a factor of two, compared to the original data. The POSS I
magnitudes can be improved to ~0.15 mag accuracy, and POSS II magnitudes to
\~0.10 mag accuracy. We use the recalibrated catalogs for the ~2,000 deg2 of
sky in the SDSS Data Release 1 to construct a catalog of ~60,000 sources
variable on time scales 10-50 years. A series of statistical tests based on the
morphology of SDSS color-color diagrams, as well as visual comparison of images
and comparison with repeated SDSS observations, demonstrate the robustness of
the selection methods. We quantify the distribution of variable sources in the
SDSS color-color diagrams, and the variability characteristics of quasars. We
detect a turn-over in quasar structure function which suggests that the
characteristic time scale for quasar variability is of the order one year. The
long-term (>1 year) quasar variability decreases with luminosity and rest-frame
wavelength similarly to the short-term (<1 year) behavior. We also demonstrate
that candidate RR Lyrae stars trace the same halo structures, such as the Sgr
dwarf tidal stream, that were discovered using repeated SDSS observations. We
utilize the POSS-SDSS selected candidates to constrain the halo structure in
the parts of sky for which repeated SDSS observations do not exist. (abridged)


title:
Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei III.
  Kinematics of Parsec-Scale Radio Jets

abstract:
  We report the results of a 15 GHz (2 cm) multi-epoch VLBA program, begun in
1994 to study the outflow in radio jets ejected from quasars and active
galaxies. The observed flow of 208 distinct features measured in 110 quasars,
active galaxies, and BL Lac objects shows highly collimated relativistic motion
with apparent transverse velocities typically between zero and about 15c, with
a tail extending up to about 34c. Within individual jets, different features
appear to move with a similar characteristic velocity which may represent an
underlying continuous jet flow, but we also see some stationary and even
apparently inward moving features which co-exist with the main features.
Comparison of our observations with published data at other wavelengths
suggests that there is a systematic decrease in apparent velocity with
increasing wavelength, probably because the observations at different
wavelengths sample different parts of the jet structure. The observed
distribution of linear velocities is not consistent with any simple ballistic
model. Either there is a rather broad range of Lorentz factors, a significant
difference between the velocity of the bulk relativistic flow and the pattern
speed of underlying shocks, or a combination of these options. Assuming a
ballistic flow, comparison of observed apparent velocities and Doppler factors
computed from the time scale of flux density variations is consistent with a
steep power law distribution of intrinsic Lorentz factors, an isotropic
distribution of orientations of the parent population, and intrinsic brightness
temperatures about an order of magnitude below the canonical inverse Compton
limit. It appears that the parent population of radio jets is not dominated by
highly relativistic flows (abridged).


title:
Magnetic activity in late-type giant stars: Numerical MHD simulations of
  non-linear dynamo action in Betelgeuse

abstract:
  Evidence is presented from numerical magneto-hydrodynamical simulations for
the existence of magnetic activity in late-type giant stars. A red supergiant
with stellar parameters similar to that of Betelgeuse (alpha Orionis) is
modeled as a "star-in-a-box" with the high-order "Pencil Code". Both linear
kinematic and non-linear saturated dynamo action are found: the non-linear
magnetic field saturates at a super-equipartition value (a factor two above
equipartition yielding surface fields with strengths on the order of 500
Gauss), while in the linear regime two different modes of dynamo action are
found. It is speculated that magnetic activity of late-type giants may
influence dust and wind formation and possibly lead to the heating of the outer
atmospheres of these stars.


title: Neutrinos from Dark Matter annihilations at the Galactic Centre

abstract:
  We discuss the prospects for detection of high energy neutrinos from dark
matter annihilation at the Galactic centre. Despite the large uncertainties
associated with our poor knowledge of the distribution of dark matter in the
innermost regions of the Galaxy, we determine an upper limit on the neutrino
flux by requiring that the associated gamma-ray emission does not exceed the
observed flux. We conclude that if dark matter is made of neutralinos, a
neutrino flux from dark matter annihilations at the GC will not be observable
by Antares. Conversely, the positive detection of such a flux would either
require an alternative explanation, in terms of astrophysical processes, or the
adoption of other \DM candidates, disfavouring the case for neutralinos.


title: Low reheating temperature and the visible sterile neutrino

abstract:
  We present here a scenario, based on a low reheating temperature T_R << 100
MeV at the end of (the last episode of) inflation, in which the coupling of
sterile neutrinos to active neutrinos can be as large as experimental bounds
permit (thus making this neutrino ``visible'' in future experiments). In
previous models this coupling was forced to be very small to prevent a
cosmological overabundance of sterile neutrinos. Here the abundance depends on
how low the reheating temperature is. For example, the sterile neutrino
required by the LSND result does not have any cosmological problem within our
scenario.


title: Dark Matter and Dark Energy

abstract:
  I briefly review our current understanding of dark matter and dark energy.
The first part of this paper focusses on issues pertaining to dark matter
including observational evidence for its existence, current constraints and the
`abundance of substructure' and `cuspy core' issues which arise in CDM. I also
briefly describe MOND. The second part of this review focusses on dark energy.
In this part I discuss the significance of the cosmological constant problem
which leads to a predicted value of the cosmological constant which is almost
$10^{123}$ times larger than the observed value $\la/8\pi G \simeq
10^{-47}$GeV$^4$. Setting $\la$ to this small value ensures that the
acceleration of the universe is a fairly recent phenomenon giving rise to the
`cosmic coincidence' conundrum according to which we live during a special
epoch when the density in matter and $\la$ are almost equal. Anthropic
arguments are briefly discussed but more emphasis is placed upon dynamical dark
energy models in which the equation of state is time dependent. These include
Quintessence, Braneworld models, Chaplygin gas and Phantom energy. Model
independent methods to determine the cosmic equation of state and the
Statefinder diagnostic are also discussed. The Statefinder has the attractive
property $\atridot/a H^3 = 1 $ for LCDM, which is helpful for differentiating
between LCDM and rival dark energy models. The review ends with a brief
discussion of the fate of the universe in dark energy models.


title: The Second Data Release of the Sloan Digital Sky Survey

abstract:
  The Sloan Digital Sky Survey has validated and made publicly available its
Second Data Release. This data release consists of 3324 square degrees of
five-band (u g r i z) imaging data with photometry for over 88 million unique
objects, 367,360 spectra of galaxies, quasars, stars and calibrating blank sky
patches selected over 2627 degrees of this area, and tables of measured
parameters from these data. The imaging data reach a depth of r ~ 22.2 (95%
completeness limit for point sources) and are photometrically and
astrometrically calibrated to 2% rms and 100 milli-arcsec rms per coordinate,
respectively. The imaging data have all been processed through a new version of
the SDSS imaging pipeline, in which the most important improvement since the
last data release is fixing an error in the model fits to each object. The
result is that model magnitudes are now a good proxy for point spread function
(PSF) magnitudes for point sources, and Petrosian magnitudes for extended
sources. The spectroscopy extends from 3800 A to 9200 A at a resolution of
2000. The spectroscopic software now repairs a systematic error in the radial
velocities of certain types of stars, and has substantially improved
spectrophotometry. All data included in the SDSS Early Data Release and First
Data Release are reprocessed with the improved pipelines, and included in the
Second Data Release. The data are publically available as of 2004 March 15 via
the web sites http://www.sdss.org/dr2 and http://skyserver.sdss.org .


title: Black hole mass estimation from X-ray variability measurements in AGN

abstract:
  We propose a new method of estimation of the black hole masses in AGN based
on the normalized excess variance, sigma_{nxs}^2. We derive a relation between
sigma_{nxs}^2, the length of the observation, T, the light curve bin size,
Delta t, and the black hole mass, assuming that (i) the power spectrum above
the high frequency break, f_{bf}, has a slope of -2, (ii) the high frequency
break scales with black hole mass, (iii) the power spectrum amplitude (in
'frequency x power' space) is universal and (iv) sigma_{nxs}^2 is calculated
from observations of length T < 1/f_{bf}. Values of black hole masses in AGN
obtained with this method are consistent with estimates based on other
techniques such as reverberation mapping or the Mbh-stellar velocity dispersion
relation. The method is formally equivalent to methods based on power spectrum
scaling with mass but the use of the normalized excess variance has the big
advantage of being applicable to relatively low quality data.


title:
Have we detected one of the sources responsible for an early
  reionisation of the Universe?

abstract:
  In a recent paper Pell'o et al. have reported a candidate z=10 galaxy,
A1835#1916, which was found in a near-infrared survey of the central regions of
the gravitational lensing cluster A1835. If this detection is confirmed and the
detection rate turns out to be typical, then the volume averaged ultraviolet
emissivity must be rising rapidly with increasing redshift. For a magnification
due to gravitational lensing by a factor M>25 estimated by Pell'o et al., the
inferred star formation rate density at z=10 would be about one order of
magnitude higher than estimates of the star formation rate density at z=6.
Objects at z=10 would contribute substantially to the total source counts at
1.6 micronm and the estimated space density of sources may exceed the space
density of dark matter haloes in a LCDM model. We therefore argue that if
A1835#1916 is indeed at z=10 then either the magnification factor may have been
overestimated or the galaxy has a top-heavy initial mass function. Sources with
the ultraviolet flux and space density of A1835#1916 may be sufficient to
reionise most of the diffuse hydrogen in the Universe at z=10. We further use a
correlation between the equivalent width and the redshift of the Ly-alpha
emission line with respect to the systemic redshift observed in Lyman break
galaxies to obtain constraints on the ionisation state of the surrounding
intergalactic medium (IGM) from the Gunn-Peterson absorption. These constraints
also argue in favour of the surrounding IGM being partially or fully ionised.


title: The physics of rotational flattening and the point core model

abstract:
  A point mass at the center of an ellipsoidal homogeneous fluid is used as a
simple model to study the effect of rotation on the shape and external
gravitational field of planets and stars. Maclaurin's analytical result for a
homogenous body is generalized to this model. The absence of a third order term
in the Taylor expansion of the Maclaurin function leads to further simple but
very accurate analytical results connecting the three observables: oblateness
($\epsilon$), gravitational quadrupole ($J_{2}$), and angular velocity
parameter ($q$). These are compared to observational data for the planets. The
moments of inertia of the planets are calculated and compared to published
values. The oblateness of the Sun is estimated. Oscillations near equilibrium
are studied within the model.


title: Wind accretion in binary stars - I. Mass accretion ratio

abstract:
  Three-dimensional hydrodynamic calculations are performed in order to
investigate mass transfer in a close binary system, in which one component
undergoes mass loss through a wind. The mass ratio is assumed to be unity. The
radius of the mass-losing star is taken to be about a quarter of the separation
between the two stars. Calculations are performed for gases with a ratio of
specific heats gamma=1.01 and 5/3. Mass loss is assumed to be thermally driven
so that the other parameter is the sound speed of the gas on the mass-losing
star. Here, we focus our attention on two features: flow patterns and mass
accretion ratio, which we define as the ratio of the mass accretion rate onto
the companion to the mass loss rate from the mass-losing primary star. We
characterize the flow by the mean normal velocity of wind on the critical Roche
surface of the mass-losing star, Vr. When Vr<0.4 A Omega, where A and Omega are
the separation between the two stars and the angular orbital frequency of the
binary, respectively, we obtain Roche-lobe over-flow (RLOF), while for Vr>0.7 A
Omega we observe wind accretion. We find very complex flow patterns in between
these two extreme cases. We derive an empirical formula of the mass accretion
ratio in the low and in the high velocity regime.


title:
The detectability of extrasolar planet surroundings - I. Reflected-light
  photometry of unresolved rings

abstract:
  It is expected that the next generation of high-contrast imaging instruments
will deliver the first unresolved image of an extrasolar planet. The emitted
thermal infrared light from the planet should show no phase effect assuming the
planet is in thermal equilibrium. But the reflected visible light will vary
versus the phase angle. Here, we study the photometric variation of the
reflected light versus the orbital phase of a ringed extrasolar planet. We show
that a ring around an extrasolar planet, both obviously unresolved, can be
detected by its specific photometric signature. A simple quantitative model is
discussed, taking into account the basic optical and geometrical properties of
the ringed planet.


title: Core Formation by a Population of Massive Remnants

abstract:
  Core radii of globular clusters in the Large and Small Magellanic Clouds show
an increasing trend with age. We propose that this trend is a dynamical effect
resulting from the accumulation of massive stars and stellar-mass black holes
at the cluster centers. The black holes are remnants of stars with initial
masses exceeding 20-25 solar masses; as their orbits decay by dynamical
friction, they heat the stellar background and create a core. Using analytical
estimates and N-body experiments, we show that the sizes of the cores so
produced and their growth rates are consistent with what is observed. We
propose that this mechanism is responsible for the formation of cores in all
globular clusters and possibly in other systems as well.


title: The First 1-2 Gyrs of Galaxy Formation: Dropout Galaxies from z~3-6

abstract:
  The unique high-resolution wide-field imaging capabilities of HST with ACS
have allowed the characterization of galaxies at redshift 6, less than 1 Gyr
from recombination. The dropout technique, applied to deep ACS i, z images in
the RCDS 1252-2927, GOODS and UDF-Parallel fields has yielded large samples of
these objects, allowing a detailed determination of their properties (e.g.,
size, color) and meaningful comparisons against lower redshift dropout samples.
The use of cloning techniques has enabled us to control for many of the strong
selection biases that affect the study of high redshift populations. A clear
trend of size with redshift has been identified, and its impact on the
luminosity density and star formation rate can be estimated. There is a
significant, though modest, decrease in the star formation rate from redshifts
z~2.5 out through z~6. The latest data also allow for the first robust
determination of the luminosity function at z~6.


title: On the nature of the unidentified MeV gamma-ray source GRO 1411-64

abstract:
  A recent analysis of COMPTEL data has revealed the existence of an
unidentified and variable gamma-ray source, designated GRO J1411-64, at MeV
energies in the galactic plane (Zhang et al. 2002). We discuss the possibility
that such a source can be produced in the accreting neutron star system 2S
1417-624 through the bombardment of the accretion disk by relativistic protons
accelerated in the magnetosphere by the Cheng-Ruderman mechanism.


title: Optical Variability of Narrow-Line Seyfert 1 Galaxies

abstract:
  We present results of a broad-band photometric study of the optical
variability of six Narrow-Line Seyfert 1 (NLS1) galaxies observed at 172
epochs. We searched for microvariability on 33 nights. Strong evidence for
microvariability was found only for our lowest luminosity object, NGC 4051, on
one night. Weaker evidence suggests such variability on a few other nights for
two other objects, but the data are not as convincing. Intra-night variability
in NLS1s is thus concluded to be rare and of low amplitude. We give
illustrations of how variable image quality can produce spurious variability.
We find that for well-studied non-NLS1s there is a spread in the amplitude of
seasonal variability (i.e., in some years an AGN is more variable than in
others). We find that the means of the variability amplitudes of non-NLS1s over
several seasons vary from object to object (i.e., some AGNs are, on average,
more variable than others). NLS1s also show a spread in seasonal variabilities.
The best-studied NLS1, Ark 564, shows a range of amplitudes of variability from
season to season that is comparable to the range found in BLS1s, and in one
season Ark 564 was as variable as the most variable non-NLS1. The seasonal
amplitudes of variability for NLS1s are mostly in the lower half of the range
of non-BLS1 seasonal amplitudes, but the absence of a suitable control sample
makes a precise comparison difficult. However, on long timescales (weeks to
years), NLS1s as a class are not more variable than non-NLS1s. The extreme
variability seen in the X-rays was not seen in the optical. This has
consequences for the models of AGNs in general as well as NLS1s in particular.


title: Nearly Minimal Magnetogenesis

abstract:
  We propose a new mechanism for magnetic field generation from inflation, by
which strong magnetic fields can be generated on cosmological scales. These
fields may be observable by cosmic microwave background radition measurements,
and may have a dynamical impact on structure formation. The mechanism is based
on the observation that a light nearly minimally coupled charged scalar may be
responsible for the creation of a negative photon mass-squared (provided the
scalar field coupling to the curvature scalar is small but negative), which in
turn results in abundant photon production - and thus in growing magnetic
fields - during inflation.


title:
Power-laws from critical gravitational collapse: The mass distribution
  of subsolar objects

abstract:
  Critical gravitational collapse and self similarity are used to probe the
mass distribution of subsolar objects. We demonstrate that at very low mass the
distribution is given by a power law, with an exponent opposite in sign to that
observed at high-mass regime. We further show that the value of this low-mass
exponent is in principle calculable via dynamical systems theory applied to
gravitational collapse. Qualitative agreement between numerical experiments and
observational data is good.


title: Structure and evolution of low mass W UMa type systems

abstract:
  The structure and evolution of low mass W UMa type contact binaries are
discussed by employing Eggleton's stellar evolution code. Assuming that these
systems completely satisfy Roche geometry, we calculate the relative radii of
both components of contact binaries in different contact depth between inner
and outer Roche lobes. We obtain a radius grid of contact binaries, and can
ensure the surfaces of two components lying on an equipotential surface by
interpolation using this radius grid when we follow the evolution of the
contact binaries. We assume that the energy transfer takes place in the
different regions of the common envelope to investigate the effects of the
region of energy transfer on the structure and evolution of contact binaries.
We find that the region of energy transfer has significant influence on the
structure and evolution of contact binaries, and conclude that the energy
transfer may occur in the outermost layers of the common convective envelope
for W-type systems, and this transfer takes place in the deeper layers of the
common envelope for A-type systems. Meanwhile, if we assume that the energy
transfer takes place in the outermost layers for our model with low total mass,
and find that our model steadily evolves towards a system with a smaller mass
ratio and a deeper envelope, suggesting that some A-type W UMa systems with low
total mass could be considered as the later evolutionary stages of W-subtype
systems, and that the surface temperature of the secondary excesses that of the
primary during the time when the primary expands rapidly, or the secondary
contracts rapidly, suggesting that W-subtype systems may be caused by expansion
of the primary, or by the contraction of the secondary.


title: Discovery of a Solitaire Dwarf Galaxy in the APPLES Survey

abstract:
  During the APPLES parallel campaign, the HST Advanced Camera for Surveys has
resolved a distant stellar system, which appears to be an isolated dwarf
galaxy. It is characterized by a circularly symmetric distribution of stars
with an integrated magnitude m(F775W) = 20.13 +- 0.02, a central surface
brightness of ~ 21.33 +- 0.18 mag/arcsec^2 and a half-light radius of ~ 1.8
arcsec. The ACS and VLT spectra show no evidence of ionized gas and appear
dominated by a 3 Gyr old stellar population. The OB spectral type derived for
two resolved stars in the grism data and the systemic radial velocity of ~ 670
km/s measured from the VLT data give a fiducial distance of ~ 9 +- 2 Mpc. These
findings, with the support of the spatial morphology, would classify the system
among the dwarf spheroidal (dSph) galaxies. Following the IAU rules, we have
named this newly discovered galaxy APPLES 1. An intriguing peculiarity of
APPLES 1 is that the properties (age and metallicity) of the stellar content so
far detected are similar to those of dSph galaxies in the Local Group, where
star formation is thought to be driven by galaxy interactions and mergers. Yet,
APPLES 1 seems not to be associated with a major group or cluster of galaxies.
Therefore, APPLES 1 could be the first example of a field dSph galaxy with
self-sustained and regulated star formation and, therefore, would make an
interesting test case for studies of the formation and evolution of unperturbed
dSph galaxies.


title: Testing the homogeneity of bright radio sources at 15 GHz

abstract:
  A sample of radio-loud active galactic nuclei (AGN) at 2cm is studied to test
the isotropic distribution of radio sources in the sky and their uniform
distribution in space. The sample is complete flux-density limits of 1.5Jy for
positive declinations and 2Jy for declinations between 0 and -20 degrees. The
active galactic nuclei sample comprises of 133 members. Application of the
two-dimensional Kolmogorov-Smirnov test shows that there is no significant
deviation from the isotropic distribution in the sky, while the generalised
V/Vm test shows that the space distribution of AGN is not uniform at high
confidence level (99.9%). This is indicative of a strong positive evolution of
AGN with cosmic epoch implying that AGN (or jet activity phenomena) were more
populous at high redshifts. It is shown that the evolution depends strongly on
luminosity: low-luminosity QSOs show a strong positive evolution, while
high-luminosity counterparts do not seem to show any evolution with cosmic
epoch.


title:
Understanding the relationship between the environment of the black hole
  and the radio jet: optical spectroscopy of compact AGN

abstract:
  We aim to investigate the relationship between radio jet activity on
parsec-scales and the characteristics of both the bright active galactic nuclei
(AGN) and their broad line regions (BLR). For this purpose, we combine 2cm Very
Long Baseline Array observations of AGN with their optical spectral
observations. This would enable us to investigate the optical spectra of a set
of 172 relativistically beamed, flat-spectrum AGN with the nuclear disk
oriented near to the plane of sky. Here, we present first results from optical
spectroscopic observations of the brightest AGN from the 2 cm VLBA survey, and
show a diversity of their spectral morphologies.


title: Twin peaks kHz QPOs: mathematics of the 3:2 orbital resonance

abstract:
  Using the method of multiple scales, one can derive an analytic solution that
describes the behaviour of weakly coupled, non-linear oscillations in nearly
Keplerian discs around neutron stars or black holes close to the 3:2 orbital
epicyclic resonance. The solution obtained agrees with the previous numerical
simulation. Such result may be relevant to the kilohertz quasi-periodic
variability in X-ray fluxes observed in many Galactic black hole and neutron
star sources. With a particular choice of tunable parameters, the solution fits
accurately the observational data for Sco X-1.


title:
Cryogenic Capacitive Transimpedance Amplifier for Astronomical Infrared
  Detectors

abstract:
  We have developed a new capacitive transimpedance amplifier (CTIA) that can
be operated at 2 K, and have good performance as readout circuits of
astronomical far-infrared array detectors. The circuit design of the present
CTIA consists of silicon p-MOSFETs and other passive elements. The process is a
standard Bi-CMOS process with 0.5$mu$m design rule. The open-loop gain of the
CTIA is more than 300, resulting in good integration performance. The output
voltage swing of the CTIA was 270 mV. The power consumption for each CTIA is
less than 10$mu$W. The noise at the output showed a$1/rm f$noise spectrum of
4$mu$V/$surdhbox Hz$at 1 Hz. The performance of this CTIA nearly fulfills the
requirements for the far-infrared array detectors onboard ASTRO-F, Japanese
infrared astronomical satellite to be launched in 2005.


title:
Raising the Dead: Clues to Type Ia Supernova Physics from the Remnant
  0509-67.5

abstract:
  We present Chandra X-ray observations of the young supernova remnant (SNR)
0509-67.5 in the Large Magellanic Cloud (LMC), believed to be the product of a
Type Ia supernova (SN Ia). The remnant is very round in shape, with a distinct
clumpy shell-like structure. Our Chandra data reveal the remnant to be rich in
silicon, sulfur, and iron. The yields of our fits to the global spectrum
confirm that 0509-67.5 is the remnant of an SN Ia and show a clear preference
for delayed detonation explosion models for SNe Ia. We study the spectrum of
the single brightest isolated knot in the remnant and find that it is enhanced
in iron by a factor of roughly two relative to the global remnant abundances.
This feature, along with similar knots seen in Tycho's SNR, argues for the
presence of modest small-scale composition inhomogeneities in SNe Ia. The
presence of both Si and Fe, with abundance ratios that vary from knot to knot,
indicates that these came from the transition region between the Si- and
Fe-rich zones in the exploded star, possibly as a result of energy input to the
ejecta at late times due to the radioactive decay of 56Ni and 56Co. Two cases
for the continuum emission from the global spectrum were modeled: one where the
continuum is dominated by hydrogen thermal bremsstrahlung radiation; another
where the continuum arises from non-thermal synchrotron radiation. The former
case requires a relatively large value for the ambient density (~1 cm^-3).
Another estimate of the ambient density comes from using the shell structure of
the remnant in the context of dynamical models. This requires a much lower
value for the density (<0.05 cm^-3) which is more consistent with other
evidence known about 0509-67.5. We therefore conclude that the bulk of the
continuum emission from 0509-67.5 has a non-thermal origin.


title: Anisotropies in the Cosmic Microwave Background

abstract:
  The linear anisotropies in the temperature of the cosmic microwave background
(CMB) radiation and its polarization provide a clean picture of fluctuations in
the universe some 370 kyr after the big bang. Simple physics connects these
fluctuations with those present in the ultra-high-energy universe, and this
makes the CMB anisotropies a powerful tool for constraining the fundamental
physics that was responsible for the generation of structure. Late-time effects
also leave their mark, making the CMB temperature and polarization useful
probes of dark energy and the astrophysics of reionization. In this review we
discuss the simple physics that processes primordial perturbations into the
linear temperature and polarization anisotropies. We also describe the role of
the CMB in constraining cosmological parameters, and review some of the
highlights of the science extracted from recent observations and the
implications of this for fundamental physics.


title:
The Damping Wing of the Gunn-Peterson Absorption and Lyman-Alpha
  Emitters in the Pre-Reionization Era

abstract:
  We use a numerical simulation of cosmological reionization to estimate the
likelihood of detecting Lyman-alpha emitting galaxies during the
pre-reionization era. We show that it is possible to find galaxies even at z~9
that are barely affected by the dumping wing of the Gunn-Peterson absorption
from the neutral IGM outside of their HII regions. The damping wing becomes
rapidly more significant at z>9, but even at z>10 is it not inconceivable
(although quite hard) to see a Lyman-alpha emission line from a star-forming
galaxy.


title: Origin of coherent magnetic fields in high redshift objects

abstract:
  Large scale strong magnetic fields in galaxies are generally thought to have
been generated by a mean field dynamo. In order to have generated the fields
observed, the dynamo would have had to have operated for a sufficiently long
period of time. However, magnetic fields of similar intensities and scales to
the one in our galaxy, are observed in high redshift galaxies, where a mean
field dynamo would not have had enough time to produce the observed fields.
Instead of a mean field dynamo, we study the emergence of strong large scale
magnetic fields in the first objects formed in the universe due to the action
or a turbulent, helical stochastic dynamo, for redshifts $5 \leq z \leq 10$.
Ambipolar drift plays an important role in this process due to the low level of
ionization of the gas, allowing a large scale stochastic dynamo to operate. We
take into account the uncertainties in the physics of high redshift objects by
examining a range of values for the parameters that characterize the turbulent
plasma. By numerically integrating the nonlinear evolution equations for the
magnetic field correlations, we show that for reasonable values of the
parameters in the time interval considered, fields can grow to high intensities
($\sim 10^{-6}$ G), with large coherence lengths ($\sim 2-6$ kpc), essentially
independent of the initial values of the magnetic field.


title: Unconventional AGN from the SDSS

abstract:
  We discuss some of the most unusual active galactic nuclei (AGN) discovered
to date by the Sloan Digital Sky Survey (SDSS): the first broad absorption line
quasar seen to exhibit He II absorption, several quasars with extremely strong,
narrow UV Fe II emission, and an AGN with an unexplained and very strange
continuum shape.


title: A new Unidentified Far Infrared Band in NGC7027

abstract:
  We report on the detection of a molecular band centered at ~98 um (~102
cm^-1), observed with the Infrared Space Observatory in the young Planetary
Nebula NGC7027. The band structure and intensity can not be reproduced by
atomic fine structure lines, recombination lines or by the rotational emission
of abundant molecules. We discuss the possible contribution of the low-energy
bending modes of pure carbon chains to the unidentified far-IR bands (UfIBs)
observed in C-rich evolved objects. In particular, we speculate that the band
emission could arise from the nu_9 and nu_7 bending modes of C_6 and C_5, for
which wavenumbers of 90+/-50 and 107+/-5 cm^-1 have been estimated from
photoelectron spectroscopy.


title:
H2 Mid-IR Pure Rotational Emission from Young Stars: The TEXES/IRTF
  Survey

abstract:
  We describe the TEXES survey for mid-IR H2 pure rotational emission from
young stars and report early successes. H2 emission is a potential tracer of
warm gas in circumstellar disks. Three pure rotational lines are available from
the ground: the J=3=>1, J=4=>2, and J=6=>4, transitions at 17.035 microns,
12.279 microns, and 8.025 microns, respectively. Using TEXES at the NASA IRTF
3m, we are midway through a survey of roughly 30 pre-main-sequence stars. To
date, detected lines are all resolved, generally with FWHM<10 km/s. Preliminary
analysis suggests the gas temperatures are between 400 and 800 K. From the work
so far, we conclude that high spectral and spatial resolution are critical to
the investigation of H2 in disks.


title:
Compact Radio Sources in Orion: New Detections, Time Variability, and
  Objects in OMC-1S

abstract:
  We present the analysis of four 3.6 cm radio continuum archival observations
of Orion obtained using the Very Large Array in its A-configuration, with
$0\rlap.{''}3$ angular resolution. The observations were made during the period
1994-1997. In a region of $4' \times 4'$, we detect a total of 77 compact radio
sources. Of the total of detected sources, 54 are detected in one or more of
the individual observations and 36 of these show time variability (by more than
30%) between the observed epochs. A deep image made from averaging all data
shows an additional 23 faint sources, in the range of 0.1 to 0.3 mJy. Of the
total of 77 sources, 39 are new centimeter detections. However, only 9 of the
77 sources do not have a previously reported counterpart at near-infrared,
optical, or X-ray wavelengths. In particular, we detect three faint sources in
the OMC-1S region that may be related to the sources that power the multiple
outflows that emanate from this part of the Orion nebula. %We discuss the
nature of these sources and its relation with the %near-infrared, optical, and
X-ray objects in the region.


title: Scenarios of modulated perturbations

abstract:
  In an alternative mechanism recently proposed, adiabatic cosmological
perturbations are generated at the decay of the inflaton field due to small
fluctuations of its coupling to matter. This happens whenever the coupling is
governed by the vacuum expectation value of another field, which acquires
fluctuations during inflation. We discuss generalization and various possible
implementations of this mechansim, and present some specific particle physics
examples. In many cases the second field can start oscillating before
perturbations are imprinted, or survive long enough so to dominate over the
decay products of the inflaton. The primordial perturbations will then be
modified accordingly in each case.


title: Properties of Cold Dark Matter Halos at z>6

abstract:
  We compute the properties of dark matter halos with mass $10^{6.5}-10^9\msun$
at redshift $z=6-11$ in the standard cold dark matter cosmological model,
utilizing a very high resolution N-body simulation. We find that dark matter
halos in these mass and redshift ranges are significantly biased over matter
with a bias factor in the range 2-6. The dark matter halo mass function
displays a slope of $2.05\pm 0.15$ at the small mass end. We do not find a
universal dark matter density profile. Instead, we find a significant
dependence of the central density profile of dark matter halos on halo mass and
epoch with $\alpha_0=0.4-1.0$; the high-mass ($M\ge 10^8\msun$) low-redshift
($z\sim 6$) halos occupy the high end of the range and low-mass ($M\sim
10^{7}\msun$) high-redshift ($z\sim 11$) halos occupy the low end.
Additionally, for fixed mass and epoch there is a significant dispersion in
$\alpha_0$ due to the stochastic assembly of halos. Our results fit a
relationship of the form
$\alpha_0=0.75((1+z)/7.0)^{-1.25}(M/10^7\msun)^{0.11(1+z)/7.0}$ with a
dispersion about this fit of $\pm 0.5$ and no systematic dependence of variance
correlated with environment. The median spin parameter of dark matter halos is
$0.03-0.04$ but with a large lognormal dispersion of $\sim 0.4$. Various
quantities are tabulated or fitted with empirical formulae.


title: Is the low-l microwave background cosmic?

abstract:
  The large-angle (low-l) correlations of the Cosmic Microwave Background
exhibit several statistically significant anomalies compared to the standard
inflationary big-bang model, however no connection has hitherto been drawn
between them. Here we show that the quadrupole and octopole are far more
correlated (99.97% C.L.) than previously thought. The quadrupole plane and the
three octopole planes are remarkably aligned. Three of these planes are
orthogonal to the ecliptic at a level inconsistent with gaussian random
statistically isotropic skies at 99.8% C.L., and the normals to these planes
are aligned at 99.9% C.L. with the direction of the cosmological dipole and
with the equinoxes. The remaining octopole plane is orthogonal to the
supergalactic plane at >99.9% C.L. In a combined quadrupole-octopole map, the
ecliptic plane narrowly threads between a hot spot and a cold spot over
approximately 1/3 of the sky, and separates the three strongest extrema (in the
south ecliptic hemisphere) from the three weakest extrema (in the north
ecliptic hemisphere).


title:
ROSAT-SDSS Galaxy Clusters Survey. I. The Catalog and the correlation of
  X-ray and optical properties

abstract:
  For a detailed comparison of the appearance of cluster of galaxies in X-rays
and in the optical, we have compiled a comprehensive database of X-ray and
optical properties of a sample of clusters based on the largest available X-ray
and optical surveys: the ROSAT All Sky Survey (RASS) and the Sloan Digital Sky
Survey (SDSS). The X-ray galaxy clusters of this RASS-SDSS catalog cover a wide
range of masses, from groups of 10^{12.5} solar masses to massive clusters of
10^{15} solar masses in the redshift range from 0.002 to 0.45. The RASS-SDSS
sample comprises all the X-ray selected objects already observed by the Sloan
Digital Sky Survey (114 clusters). For each system we have uniformly determined
the X-ray and optical properties. The total optical luminosity can be
determined with a typical uncertainty of 20% with a result independent of the
choice of local or global background subtraction. We found that the z band
cluster luminosity determined within an aperture of 0.5 Mpc h_{70}^(-1)
provides the best correlation with the X-ray luminosity with a scatter of about
60-70%. The scatter decreases to less than 40% if the correlation is limited to
the bright X-ray clusters. The resulting correlation of L_X and L_{op} in the z
and i bands shows a logarithmic slope of 0.38, a value not consistent with the
assumption of a constant M/L. Consistency is found, however, for an increasing
M/L with luminosity as suggested by other observations. We also investigated
the correlation between L_{op} and the X-ray temperature obtaining the same
result.


title:
3-D Photoionization Structure and Distances of Planetary Nebulae I.
  NGC6369

abstract:
  We present the results of mapping the planetary nebula NGC6369 using multiple
long slit spectra taken with the CTIO 1.5m telescope. We create two dimensional
emission line images from our spectra, and use these to derive fluxes for 17
lines, the Halpha/Hbeta extinction map, the [SII] line ratio density map, and
the [NII] temperature map of the nebula. We use our photoionization code
constrained by these data to determine the distance, the ionizing star
characteristics, and show that a clumpy hour-glass shape is the most likely
three-dimensional structure for NGC6369. Note that our knowledge of the nebular
structure eliminates all uncertainties associated with classical distance
determinations, and our method can be applied to any spatially resolved
emission line nebula. We use the central star, nebular emission line, and
optical+IR luminosities to show that NGC6369 is matter bound, as about 70% of
the Lyman continuum flux escapes. Using evolutionary tracks from Bloecker(1995)
we derive a central star mass of about 0.65 Msolar.


title:
Hydrodynamic Simulations of Tilted Thick-Disk Accretion onto a Kerr
  Black Hole

abstract:
  We present results from fully general relativistic three-dimensional
numerical studies of thick-disk accretion onto a rapidly-rotating (Kerr) black
hole with a spin axis that is tilted (not aligned) with the angular momentum
vector of the disk. We initialize the problem with the solution for an aligned,
constant angular momentum, accreting thick disk, which is then allowed to
respond to the Lense-Thirring precession of the tilted black hole. The
precession causes the disk to warp, beginning at the inner edge and moving out
on roughly the Lense-Thirring precession timescale. The propagation of the warp
stops at a radius in the disk at which other dynamical timescales, primarily
the azimuthal sound-crossing time, become shorter than the precession time. At
this point, the warp effectively freezes into the disk and the evolution
becomes quasi-static, except in cases where the sound-crossing time in the bulk
of the disk is shorter than the local precession timescale. We see evidence
that such disks undergo near solid-body precession after the initial warping
has frozen in. Simultaneous to the warping of the disk, there is also a
tendency for the midplane to align with the symmetry plane of the black hole
due to the preferential accretion of the most tilted disk gas. This alignment
is not as pronounced, however, as it would be if more efficient angular
momentum transport (e.g. from viscosity or magneto-rotational instability) were
considered.


title:
ROSAT-SDSS Galaxy Clusters Survey. Correlating X-ray and optical
  properties

abstract:
  For a detailed comparison of the appearance of cluster of galaxies in X-rays
and in the optical, we have compiled a comprehensive database of X-ray and
optical properties of a sample of clusters based on the largest available X-ray
and optical surveys: the ROSAT All Sky Survey (RASS) and the Sloan Digital Sky
Survey (SDSS). The RASS-SDSS sample comprises 114 X-ray selected clusters. For
each system we have uniformly determined the X-ray and optical properties . For
a subsample of 53 clusters we have also compiled the temperature and the iron
abundance from the literature. The total optical luminosity can be determined
with a typical uncertainty of 20% with a result independent of the choice of
local or global background subtraction. We searched for parameters which
provide the best correlation between the X-ray luminosity and the optical
properties and found that the z band luminosity determined within a cluster
aperture of 0.5 Mpc h_{70}^{-1} provides the best correlation with a scatter of
about 60%. The resulting correlation of L_X and L_{op} in the z and i bands
shows a logarithmic slope of 0.38, a value not consistent with the assumption
of a constant M/L. Consistency is found, however, for an increasing M/L with
luminosity. This is confirmed by our analysis of the cluster mass to light
ratio for a subsample of 53 clusters. We found a significant dependence of M/L
on the cluster mass with a logarithmic slope ranging from 0.27 in the i and r
bands to 0.22 in the z band.


title:
Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects
  2000 CR105 and 2003 VB12

abstract:
  Explaining the origin of the orbit of 2000 CR105 (a ~ 230AU, q ~ 45AU) is a
major test for our understanding of the primordial evolution of the outer Solar
System. Gladman et al. (2001) showed that this objects could not have been a
normal member of the scattered disk that had its perihelion distance increased
by chaotic diffusion. In this paper we explore four seemingly promising
mechanisms for explaining the origin of the orbit of this peculiar object: (i)
the passage of Neptune through a high-eccentricity phase, (ii) the past
existence of massive planetary embryos in the Kuiper belt or the scattered
disk, (iii) the presence of a massive trans-Neptunian disk at early epochs
which exerted tides on scattered disk objects, and (iv) encounters with other
stars. Of all these mechanisms, the only one giving satisfactory results is the
passage of a star. Indeed, our simulations show that the passage of a solar
mass star at about 800 AU only perturbs objects with semi-major axes larger
than roughly 200 AU to large perihelion distances. This is in good agreement
with the fact that 2000 CR105 has a semi-major axis of 230AU and no other
bodies with similar perihelion distances but smaller semi-major axes have yet
been discovered. The discovery of 2003 VB12, (a=450AU, q=75AU) announced a few
days before the submission of this paper, strengthen our conclusions.


title: The RASS-SDSS galaxy cluster survey

abstract:
  Solid observational evidences indicate a strong dependence of the galaxy
formation and evolution on the environment. In order to study in particular the
interaction between the intracluster medium and the evolution of cluster
galaxies, we have created a large database of clusters of galaxies based on the
largest available X-ray and optical surveys: the ROSAT All Sky Survey (RASS),
and the Sloan Digital Sky Survey (SDSS). We analyzed the correlation between
the total optical and the X-ray cluster luminosity. The resulting correlation
of L_X and L_{op} shows a logarithmic slope of 0.6, a value close to the
self-similar correlation. We analysed also the cluster mass to light ratio, by
finding a significant dependence of M/L on the cluster mass with a logarithmic
slope ranging from 0.27 in the i and r bands to 0.22 in the z band.


title: Quiescent Burst Evidence for Two Distinct GRB Emission Components

abstract:
  We have identified two quiescent GRBs (bursts having two or more
widely-separated distinct emission episodes) in which the post-quiescent
emission exhibits distinctly different characteristics than the pre-quiescent
emission. In these two cases (BATSE GRBs 960530 and 980125), the second
emission episode has a longer lag, a smoother morphology, and softer spectral
evolution than the first episode. Although the pre-quiescent emission satisfies
the standard internal shock paradigm, we demonstrate that the post-quiescent
emission is more consistent with external shocks. We infer that some observed
soft, faint, long-lag GRBs are external shocks in which the internal shock
signature is not observed. We further note that the peak luminosity ratio
between quiescent episodes is not in agreement with the ratio predicated by the
lag vs. peak luminosity relationship. We briefly discuss these observations in
terms of current collapsar jet models.


title:
First Stellar Binary Black Holes: Strongest Gravitational Wave Burst
  Sources

abstract:
  Evolution of first population of massive metal-free binary stars is followed.
Due to the low metallicity, the stars are allowed to form with large initial
masses and to evolve without significant mass loss. Evolution at zero
metallicity, therefore, may lead to the formation of massive remnants. In
particular, black holes of intermediate-mass (100-500 Msun) are expected to
have formed in early Universe, in contrast to the much lower mass stellar black
holes (10 Msun) being formed at present. Following a natural assumption, that
some of these Population III stars have formed in binaries, the physical
properties of first stellar binary black holes are presented. We find that a
significant fraction of such binary black holes coalesces within the Hubble
time. We point out that burst of gravitational waves from the final
coalescences and the following ringdown of these binary black hole mergers can
be observed in the interferometric detectors. We estimate that advanced LIGO
detection rate of such mergers is at least several events per year with high
signal to noise ratio (>10).


title: Angular momentum transport in accretion disks

abstract:
  We reexamine arguments advanced by Hayashi & Matsuda (2001), who claim that
several simple, physically motivated derivations based on mean free path theory
for calculating the viscous torque in a quasi-Keplerian accretion disk yield
results that are inconsistent with the generally accepted model. If correct,
the ideas proposed by Hayashi & Matsuda would radically alter our understanding
of the nature of the angular momentum transport in the disk, which is a central
feature of accretion disk theory. However, in this paper we point out several
fallacies in their arguments and show that there indeed exists a simple
derivation based on mean free path theory that yields an expression for the
viscous torque that is proportional to the radial derivative of the angular
velocity in the accretion disk, as expected. The derivation is based on the
analysis of the epicyclic motion of gas parcels in adjacent eddies in the disk.


title: Source separation on astrophysical data sets from the WMAP satellite

abstract:
  This paper presents and discusses the application of blind source separation
to astrophysical data obtained with the WMAP satellite. Blind separation
permits to identify and isolate a component compatible with CMB emission, and
to measure both its spatial power spectrum and its emission law. Both are found
to be compatible with the present concordance cosmological model. This
application demonstrates the usefulness of blind ICA for cosmological
applications.


title: Submillimeter Array observations of ISM in starburst galaxies

abstract:
  The Submillimeter Array (SMA) has been under construction at the 4100 m
summit of Mauna Kea, Hawaii. The array is going to allow imaging of lines and
continuum at sub-arcsecond resolution in submillimeter wavelengths. The status
of the array and the results from recent commissioning observations of nearby
galaxies are reported.


title: On the origin of the C IV Baldwin effect in AGN

abstract:
  The origin of the luminosity dependence of the equivalent width (EW) of broad
emission lines in AGN (the Baldwin effect) is not firmly established yet. We
explore this question for the broad C IV \lambda 1549 line using the Boroson &
Green sample of the 87 z < 0.5 Bright Quasar Survey (BQS) quasars. Useful UV
spectra of the C IV region are available for 81 of the objects, which are used
to explore the dependence of the C IV EW on various emission properties. We
confirm earlier results on the strong correlations of the C IV EW with some of
the emission parameters which define the Boroson & Green Eigenvector 1, and
with the optical to X-ray slope \alpha_ox. In addition, we find a strong
correlation of the C IV EW with the relative accretion rate, L/L_Edd. Since
L/L_Edd drives some of the Eigenvector 1 correlations, it may be the primary
physical parameter which drives the Baldwin effect for C IV.


title: The 6C** Sample and the Highest Redshift Radio Galaxies

abstract:
  We present a new radio sample, 6C** designed to find radio galaxies at z > 4
and discuss some of its near-infrared imaging follow-up results.


title:
Estimating the angular resolution of tracks in neutrino telescopes based
  on a likelihood analysis

abstract:
  A semianalytic method to estimate the angular resolution of tracks, that have
been reconstructed by a likelihood approach, is presented. The optimal choice
of coordinate systems and resolution parameters, as well as tests of the method
are discussed based on an application for a neutrino telescope.


title: Submillimetre photometry of typical high-redshift radio quasars

abstract:
  We present submillimetre (SCUBA) photometry of a sample of eight
high-redshift (2.5 < z < 3.5) radio quasars from two redshift surveys: the
TEXOX-1000, or TOOT, survey; and the 7C Redshift Survey (7CRS). Unlike the
powerful high-redshift radio sources observed previously in the submillimetre,
these radio sources are typical of those dominating the radio luminosity
density of the population. We detect just two of the TOOT/7CRS targets at 850
microns, and one of these detections is probably due to synchrotron emission
rather than dust. The population represented by the other six objects is
detected in a statistical sense with their average 850-micron flux density
implying that they are similar to low-redshift, far-infrared-luminous quasars
undergoing at most moderate (< 200 solar masses per year) starbursts. By
considering all the SCUBA data available for radio sources, we conclude that
positive correlations between rest-frame far-infrared luminosity, 151-MHz
luminosity and redshift, although likely to be present, are hard to interpret
because of subtle selection and classification biases, small number statistics
and uncertainties concerning synchrotron contamination and K-correction. We
argue that there is not yet any compelling evidence for significant differences
in the submillimetre properties of radio-loud and radio-quiet quasars at high
redshift.


title: Atmospheric Escape from Hot Jupiters

abstract:
  The extra-solar planet HD209458b has been found to have an extended
atmosphere of escaping atomic hydrogen (Vidal-Madjar et al. 2003), suggesting
that ``hot Jupiters'' closer to their parent stars could evaporate. Here we
estimate the atmospheric escape (so called evaporation rate) from hot Jupiters
and their corresponding life time against evaporation. The calculated
evaporation rate of HD209458b is in excellent agreement with the HI Lyman-alpha
observations. We find that the tidal forces and high temperatures in the upper
atmosphere must be taken into account to obtain reliable estimate of the
atmospheric escape. Because of the tidal forces, we show that there is a new
escape mechanism at intermediate temperatures at which the exobase reaches the
Roche lobe. From an energy balance, we can estimate plausible values for the
planetary exospheric temperatures, and thus obtain typical life times of
planets as a function of their mass and orbital distance.


title: Accretion Disc Evolution in DW Ursae Majoris: A Photometric Study

abstract:
  We present an analysis of CCD photometric observations of the eclipsing
novalike cataclysmic variable DW UMa obtained in two different luminosity
states: high and intermediate. The star presents eclipses with very different
depth: ~1.2 mag in the high and ~3.4 mag in the intermediate state. Eclipse
mapping reveals that this difference is almost entirely due to the changes in
the accretion disc radius: from ~0.5RL1 in the intermediate state to ~0.75RL1
in the high state (RL1 is the distance from the white dwarf to the first
Lagrangian point). In the intermediate state, the entire disc is eclipsed while
in the high state, its outer part remains visible. We also find that the
central intensity of the disc is nearly the same in the two luminosity states
and that it is the increase of the disc radius that is responsible for the
final rise from the 1999/2000 low state. We find that the intensity profile of
the disc is rather flat and suggest a possible explanation. We also discuss the
effect of using a more realistic limb-darkening law on the disc temperatures
inferred from eclipse mapping experiments. Periodogram analysis of the high
state data reveals "positive superhumps" with a period of 0.1455 in 2002 and
0.1461 in 2003, in accord with the results of Patterson et al. However, we
cannot confirm the quasi-periodic oscillations reported by these authors. We
obtain an updated orbital ephemeris of DW UMa:
Tmin[HJD]=2446229.00687(9)+0.136606527(3)E.


title:
Electron temperatures and densities of planetary nebulae determined from
  the nebular hydrogen recombination spectrum and temperature and density
  variations

abstract:
  A method is presented to derive electron temperatures and densities of
planetary nebulae (PNe) simultaneously, using the observed hydrogen
recombination spectrum, which includes continuum and line emission. By matching
theoretical spectra to observed spectra around the Balmer jump at about 3646A,
we determine electron temperatures and densities for 48 Galactic PNe. The
electron temperatures based on this method are found to be systematically lower
than those derived from [O III] 4959/4363 and [O III] (88\mu+52\mu)/4959
ratios. And the electron densities based on this method are found to be
systematically higher than those derived from forbidden line ratios. These
results suggest that temperature and density fluctuations are generally present
within nebulae. In addition, He/H abundances of PNe are found to be positively
correlated with the difference between T_e([O III]) and T_e(Bal), suggesting
that He/H abundances might have been overestimated generally because of the
possible existence of H-deficient knots.


title:
Cold Molecular Gas as a Possible Component of Dark Matter in the Outer
  Parts of Disk Galaxies

abstract:
  In the last few years new evidence has been presented for the presence of
ongoing massive star formation in the outer HI disks of galaxies. These
discoveries strongly suggest that precursor molecular gas must also be present
in some physical state which is escaping detection by the usual means (CO(1-0),
IR, etc.). We present a model for such a gas in a framework which views the HI
as the result of an ongoing ``photodissociation <--> dust grain reformation''
equilibrium in a cold, clumpy molecular medium with a small area filling
factor.


title: Optical Astronomy in Post-Apartheid South Africa: 1994 to 2004

abstract:
  The progress of optical astronomy in post-apartheid South Africa is
discussed. Particular emphasis is given to the socio-political climate which
embraced the idea of a 10-m class telescope as a flagship project that would
lead to widespread development in science, technology and education - not only
in South Africa, but across the subcontinent.


title: Mergers of binary stars: The ultimate heavy-ion experience

abstract:
  The mergers of black hole-neutron star binaries are calcuated using a
pseudo-general relativistic potential that incorporates ${\mathcal
O}(v^2/c^2)^3$ post-Newtonian corrections. Both normal matter neutron stars and
self-bound strange quark matter stars are considered as black hole partners. As
long as the neutron stars are not too massive relative to the black hole mass,
orbital decay terminates in stable mass transfer rather than an actual merger.
For a normal neutron star, mass transfer results in a widening of the orbit but
the stable transfer ends before the minimum neutron star mass is reached. For a
strange star, mass transfer does not result in an appreciable enlargement of
the orbital separation, and the stable transfer continues until the strange
star essentially disappears. These differences might be observable through
their respective gravitational wave signatures.


title:
XMM-Newton spectra of hard spectrum Rosat AGN: X-ray absorption and
  optical reddening

abstract:
  We present the XMM-Newton spectra of three low-redshift intermediate Seyferts
(one Sy1.5, and two Sy1.8), from our survey of hard spectrum Rosat sources. The
three AGN are well fitted by absorbed powerlaws, with intrinsic nuclear
photoelectric absorption from column densities between 1.3 and 4.0e21 cm-2. In
the brightest object the X-ray spectrum is good enough to show that the
absorber is not significantly ionized. For all three objects the powerlaw
slopes appear to be somewhat flatter (Gamma~1.3-1.6) than those found in
typical unabsorbed Seyferts. The constraints from optical and X-ray emission
lines imply that all three objects are Compton-thin. For the two fainter
objects, the reddening deduced from the optical broad emission lines in one of
them, and the optical continuum in the other, are similar to those expected
from the X-ray absorption, if we assume a Galactic gas-to-dust ratio and
reddening curve. The broad line region Balmer decrement of our brightest object
is larger than expected from its X-ray absorption, which can be explained
either by an intrinsic Balmer decrement with standard gas-to-dust ratio, or by
a >Galactic gas-to-dust ratio. These >=Galactic ratios of extinction to
photoelectric absorption cannot extend to the high redshift, high luminosity,
broad line AGN in our sample, because they have column densities >1e22 cm-2,
and so their broad line regions would be totally obscured. This means that some
effect (e.g., luminosity dependence, or evolution) needs to be present in order
to explain the whole population of absorbed AGN.


title:
The formation of the solar system by gravitational instability:
  Prediction of a new planet or another Kuiper-type belt

abstract:
  The early gas-dust solar nebula is considered: the gasdynamic theory is used
to study the gravitational Jeans-type instability in its protoplanetary disk.
The implications for the origin of the solar system are discussed. It is shown
that a collective process, forming the basis of the gravitational instability
hypothesis, solves with surprising simplicity the two main problems of the
dynamical characteristics of the system, which are associated with its observed
spacing and orbital momentum distribution. The analysis is found to imply the
existence of a new planet (or another Kuiper-type belt) at a mean distance from
the Sun of 87 AU.


title: Can dust destabilize galactic disks?

abstract:
  We studied the dynamical influence of a dust component on the gaseous phase
in central regions of galactic disks. Therefore, we performed two-dimensional
hydrodynamical simulations for flat multi-component disks embedded in a stellar
and dark matter potential. The pressure-free dust component is coupled to the
gas by a drag force depending on their velocity difference.
  It turned out that the most unstable regions are those with either a low or
near to minimum Toomre parameter or with rigid rotation, i.e. the central area.
In that regions the dust-free disks become most unstable for a small range of
high azimuthal modes (m \sim 8), whereas in dusty disks all modes have similar
amplitudes resulting in a patchy appearance. The structures in the dust have a
larger contrast between arm and inter-arm regions than those of the gas. The
dust peaks are frequently correlated with peaks of the gas distribution, but
they do not necessarily coincide with them. This leads to a large scatter in
the dust-to-gas ratios. The appearance of the dust is more cellular (i.e.
sometimes connecting different spiral features), whereas the gas is organized
in a multi-armed spiral structure.
  We found that an admixture of 2% dust (relative to the mass of the gas)
destabilizes gaseous disks substantially, whereas dust-to-gas ratios below 1%
have no influence on the evolution of the gaseous disk. For a high dust-to-gas
ratio of 10% the instabilities reach the saturation level already after 30 Myr.


title: Skewness as a test for Quartessence

abstract:
  Quartessence is one of the alternatives to Lambda-CDM that has lately
attracted considerable interest. According to this unifying dark matter/energy
scenario, the Universe evolved from an early non-relativistic matter-dominated
phase to a more recent accelerated expansion phase, driven by a single fluid
component. Recently, it has been shown that some problems of the quartessence
model, such as the existence of instabilities and oscillations in the matter
power spectrum, can be avoided if a specific type of intrinsic entropy
perturbation is considered. In the present article we explore the role of
skewness in constraining this non-adiabatic scenario. We show that
non-adiabatic quartessence and quintessence have different signatures for the
skewness of the density distribution on large scales and suggest that this
quantity might prove helpful to break possible degeneracies between them.


title:
Exact versus approximate equitemporal surfaces in Gamma-Ray Burst
  afterglows

abstract:
  By integrating the relativistic hydrodynamic equations introduced by Taub we
have determined the exact EQuiTemporal Surfaces (EQTSs) for the Gamma-Ray Burst
(GRB) afterglows. These surfaces are compared and contrasted to the ones
obtained, using approximate methods, by Panaitescu & Meszaros (1998), Sari
(1998), Granot et al. (1999).


title: Timing Analysis of the Isolated Neutron Star RX J0720.4-3125 Revisited

abstract:
  We present a reanalysis of the X-ray data for RX J0720.4-3125 presented in
Zane et al. (2002), using more data recently available from XMM-Newton and
Chandra. This analysis also corrects the Rosat data used in that paper to the
TDB time system, incorporates the revised XMM-Newton barycentric correction
available since then, and corrects the definition of the instantaneous period
in the maximum likelihood periodogramme search. However, we are now unable to
find a single coherent period that is consistent with all Rosat, Chandra and
XMM-Newton datasets. From an analysis of the separate datasets, we have derived
limits on the period change of Pdot = 1.4+/-0.6x10^-13 s/s at 99% confidence
level. This is stronger than the value presented in Zane et al. (2002), but
sufficiently similar that their scientific conclusions remain unchanged. We
examine the implications in more detail, and find that RX J0720.4-3125 can have
been born as a magnetar provided that it has a young age of ~10^4 yr. A more
conservative interpretation is that the field strength has remained relatively
unchanged at just over 10^13 G, over the ~10^6 yr lifetime of the star.


title: Connecting the cosmic infrared background to the X-ray background

abstract:
  We estimate the contribution of AGNs and of their host galaxies to the
infrared background. We use the luminosity function and evolution of AGNs
recently determined by the hard X-ray surveys, and new Spectral Energy
Distributions connecting the X-ray and the infrared emission, divided in
intervals of absorption. These two ingredients allow us to determine the
contribution of AGNs to the infrared background by using mostly observed
quantities, with only minor assumptions. We obtain that AGN emission
contributes little to the infrared background ($<$5% over most of the infrared
bands), implying that the latter is dominated by star formation. However, AGN
host galaxies may contribute significantly to the infrared background, and more
specifically 10--20% in the 1--20$\mu$m range and $\sim$5% at $\lambda<60\mu
m$. We also give the contribution of AGNs and of their host galaxies to the
source number counts in various infrared bands, focusing on those which will be
observed with Spitzer. We also report a significant discrepancy between the
expected contribution of AGN hosts to the submm background and bright submm
number counts with the observational constraints. We discuss the causes and
implications of this discrepancy and the possible effects on the Spitzer far-IR
bands.


title: The Sun Asphericities: Astrophysical Relevance

abstract:
  Of all the fundamental parameters of the Sun (diameter, mass,
temperature...), the gravitational multipole moments (of degree l and order m)
that determine the solar moments of inertia, are still poorly known. However,
at the first order (l=2), the quadrupole moment is relevant to many
astrophysical applications. It indeed contributes to the relativistic
perihelion advance of planets, together with the post-Newtonian (PN)
parameters; or to the precession of the orbital plane about the Sun polar axis,
the latter being unaffected by the purely relativistic PN contribution. Hence,
a precise knowledge of the quadrupole moment is necessary for accurate orbit
determination, and alternatively, to obtain constraints on the PN parameters.
Moreover, the successive gravitational multipole moments have a physical
meaning: they describe deviations from a purely spherical mass distribution.
Thus, their precise determination gives indications on the solar internal
structure. Here, we explain why it is difficult to compute these parameters,
how to derive the best values, and how they will be determined in a near future
by means of space experiments.


title: The Triggering and Bias of Radio Galaxies

abstract:
  We present new results on the clustering and three-dimensional distribution
of radio galaxies from the Texas-Oxford NVSS Structure (TONS) survey. The TONS
survey was constructed to look at the distribution of radio galaxies in a
region of moderate (0 < z < 0.5) redshifts by matching NVSS sources with
objects in APM catalogues to obtain a sample of optically bright (R < 19.5),
radio faint (1.4-GHz flux density S_1.4 > 3 mJy) radio galaxies over large
areas on the sky. We find that redshift spikes, which represent large
concentrations of radio galaxies which trace (~ 100 Mpc^3) super-structures are
a common phenomena in these surveys. Under the assumption of quasi-linear
structure formation theory and a canonical radio galaxy bias, the structures
represent ~ 4-5 sigma peaks in the primordial density field and their expected
number is low. The most plausible explanation for these low probabilities is an
increase in the radio galaxy bias with redshift. To investigate potential
mechanisms which have triggered the radio activity in these galaxies - and
hence may account for an increase in the bias of this population, we performed
imaging studies of the cluster environment of the radio galaxies in
super-structure regions. Preliminary results show that these radio galaxies may
reside preferentially at the edges of rich clusters. If radio galaxies are
preferentially triggered as they fall towards rich clusters then they would
effectively adopt the cluster bias.


title: Evolution of the Dark Matter Distribution with 3-D Weak Lensing

abstract:
  We present a direct detection of the growth of large-scale structure, using
weak gravitational lensing and photometric redshift data from the COMBO-17
survey. We use deep R-band imaging of two 0.25 square degree fields, affording
shear estimates for over 52000 galaxies; we combine these with photometric
redshift estimates from our 17 band survey, in order to obtain a 3-D shear
field. We find theoretical models for evolving matter power spectra and
correlation functions, and fit the corresponding shear correlation functions to
the data as a function of redshift. We detect the evolution of the power at the
7.7 sigma level given minimal priors, and measure the rate of evolution for
0<z<1. We also fit correlation functions to our 3-D data as a function of
cosmological parameters sigma_8 and Omega_Lambda. We find joint constraints on
Omega_Lambda and sigma_8, demonstrating an improvement in accuracy by a factor
of 2 over that available from 2D weak lensing for the same area.


title: Palomar 13: a velocity dispersion inflated by binaries ?

abstract:
  Recently, combining radial velocities from Keck/HIRES echelle spectra with
published proper motion membership probabilities, Cote et al (2002) observed a
sample of 21 stars, probable members of Palomar 13, a globular cluster in the
Galactic halo. Their projected velocity dispersion sigma_p = 2.2 +/-0.4 km/s
gives a mass-to-light ratio M/L_V = 40 +24/-17, about one order of magnitude
larger than the usual estimate for globular clusters. We present here radial
velocities measured from three different CCD frames of commissioning
observations obtained with the new ESO/VLT instrument FLAMES (Fibre Large Array
Multi Element Spectrograph). From these data, now publicly available, we
measure the homogeneous radial velocities of eight probable members of this
globular cluster. A new projected velocity dispersion sigma_p = 0.6-0.9 +/-0.3
km/s implies Palomar 13 mass-to-light ratio M/L_V = 3-7, similar to the usual
value for globular clusters. We discuss briefly the two most obvious reasons
for the previous unusual mass-to-light ratio finding: binaries, now clearly
detected, and more homogeneous data from the multi-fibre FLAMES spectrograph.