title:
Radiative Transfer with Finite Elements II. Ly-alpha Line Transfer in
  Moving Media

abstract:
  A finite element method for solving the resonance line transfer problem in
moving media is presented. The algorithm works in three spatial dimensions on
unstructured grids which are adaptively refined by means of an a posteriori
error indicator. Frequency discretization is implemented via a first-order
Euler scheme. We discuss the resulting matrix structure for coherent isotropic
scattering and complete redistribution. The solution is performed using an
iterative procedure, where monochromatic radiative transfer problems are
successively solved. The present implementation is applicable for arbitrary
model configurations with an optical depth up to 10^(3-4). Results of Ly-alpha
line transfer calculations for a spherically symmetric model, a disk-like
configuration, and a halo containing three source regions are discussed. We
find the characteristic double-peaked Ly-alpha line profile for all models with
an optical depth > 1. In general, the blue peak of the profile is enhanced for
models with infall motion and the red peak for models with outflow motion. Both
velocity fields produce a triangular shape in the two-dimensional Ly-alpha
spectra, whereas rotation creates a shear pattern. Frequency-resolved Ly-alpha
images may help to find the number and position of multiple Ly-alpha sources
located in a single halo. A qualitative comparison with observations of
extended Ly-alpha halos associated with high redshift galaxies shows that even
models with lower hydrogen column densities than required from profile fitting
yield results which reproduce many features in the observed line profiles and
two-dimensional spectra.


title: Three-dimensional simulations of type Ia supernovae

abstract:
  We present the results of three-dimensional hydrodynamical simulations of the
subsonic thermonuclear burning phase in type Ia supernovae. The burning front
model contains no adjustable parameters so that variations of the explosion
outcome can be linked directly to changes in the initial conditions. In
particular, we investigate the influence of the initial flame geometry on the
explosion energy and find that it appears to be weaker than in 2D. Most
importantly, our models predict global properties such as the produced nickel
masses and ejecta velocities within their observed ranges without any fine
tuning.


title: The orbital modulation in the radio emission of Cygnus X-1

abstract:
  We present model lightcurves which have been created in order to explain the
orbital modulation observed in the radio emission of Cyg X-1. We invoke
variable absorption by the stellar wind as the black hole jet orbits around the
OB companion star and find that a very simple model is able to reproduce the
amplitudes and frequency dependence of the observed lightcurves.


title: Relic Backgrounds of Gravitational Waves from Cosmic Turbulence

abstract:
  Turbulence may have been produced in the early universe during several kind
of non-equilibrium processes. Periods of cosmic turbulence may have left a
detectable relic in the form of stochastic backgrounds of gravitational waves.
In this paper we derive general expressions for the power spectrum of the
expected signal. Extending previous works on the subject, we take into account
the effects of a continuous energy injection power and of magnetic fields. Both
effects lead to considerable deviations from the Kolmogorov turbulence
spectrum. We applied our results to determine the spectrum of gravity waves
which may have been produced by neutrino inhomogeneous diffusion and by a first
order phase transition. We show that in both cases the expected signal may be
in the sensitivity range of LISA.


title: CDM, Feedback and the Hubble Sequence

abstract:
  We have performed TreeSPH simulations of galaxy formation in a standard LCDM
cosmology, including effects of star formation, energetic stellar feedback
processes and a meta-galactic UV field, and obtain a mix of disk, lenticular
and elliptical galaxies. The disk galaxies are deficient in angular momentum by
only about a factor of two compared to observed disk galaxies. The stellar
disks have approximately exponential surface density profiles, and those of the
bulges range from exponential to r^{1/4}, as observed. The bulge-to-disk ratios
of the disk galaxies are consistent with observations and likewise are their
integrated B-V colours, which have been calculated using stellar population
synthesis techniques. Furthermore, we can match the observed I-band
Tully-Fisher (TF) relation, provided that the mass-to-light ratio of disk
galaxies, (M/L_I), is about 0.8. The ellipticals and lenticulars have
approximately r^{1/4} stellar surface density profiles, are dominated by
non-disklike kinematics and flattened due to non-isotropic stellar velocity
distributions, again consistent with observations.


title:
Detection of molecular hydrogen in a near Solar-metallicity damped
  Lyman-alpha system at z_abs~2 toward Q 0551-366

abstract:
  We report the detection of H_2, CI, CI*, CI** and Cl I lines in a near
Solar-metallicity ([Zn/H]=-0.13) damped Lyman-alpha (DLA) system at z_abs=1.962
observed on the line of sight to the quasar Q 0551-366. The iron-peak elements,
X=Fe, Cr and Mn are depleted compared to zinc, [X/Zn] -0.8, probably because
they are tied up onto dust grains. Among the three detected H_2-bearing clouds,
spanning 55 km s^-1 in velocity space, we derive a total molecular hydrogen
column density N(H_2)=2.6x10^17 cm^-2 and a mean molecular fraction
f=2N(H_2)/(2N(H_2)+N(HI))=1.7x10^-3. The depletion of heavy elements (S, Si,
Mg, Mn, Cr, Fe, Ni and Ti) in the central component is similar to that observed
in the diffuse neutral gas of the Galactic halo. This depletion is
approximately the same in the six CI-detected components independently of the
presence or absence of H_2. The gas clouds in which H_2 is detected always have
large densities, n_H>30 cm^-3, and low temperatures, T_01<~100 K. This shows
that presence of dust, high particle density and/or low temperature are
required for molecules to be present. The photo-dissociation rate derived in
the components where H_2 is detected suggests the existence of a local UV
radiation field similar in strength to the one in the Galaxy. Star formation
therefore probably occurs near these H_2-bearing clouds.


title: Creation of X-ray Holes with Cool Rims in Cooling Flows

abstract:
  The density irregularities and holes visible in many Chandra X-ray images of
cluster and galactic cooling flows can be produced by symmetrically heated gas
near the central galactic black hole. As the heated gas rises away from the
galactic center, a relatively small number of large plumes and bubbles are
formed in qualitative agreement with the observed features. The expanding
centrally heated gas drives a shock into the surrounding gas, displacing it
radially. Both computational and analytic results show that the ambient gas
near the bubble is cooled by expansion, accounting for the cool rims commonly
observed around X-ray holes in cooling flows.


title: The Strongly Polarized Afterglow of GRB 020405

abstract:
  We report polarization measurements and photometry for the optical afterglow
of the gamma-ray burst GRB 020405. We measured a highly significant 9.9%
polarization (in V band) 1.3 days after the burst and argue that it is
intrinsic to the GRB. The light curve decay is well fitted by a $t^{-1.72}$
power-law; we do not see any evidence for a break between 1.24 and 4.3 days
after the burst. We discuss these measurements in the light of several models
of GRB afterglows.


title: X-ray Detection of the Inner Jet in the Radio Galaxy 3C 129

abstract:
  During the course of an investigation on the interaction of the radio galaxy
3C129 and its ambient cluster gas, we found excess X-ray emission aligned with
the northern radio jet. The emission extends from the weak X-ray core of the
host galaxy approximately 2.5" to the first resolved radio knot. On a smaller
scale, we have also detected a weak radio extension in the same position angle
with the VLBA. Although all the evidence suggests that Doppler favoritism
augments the emission of the northern jet, it is unlikely that the excess X-ray
emission is produced by inverse Compton emission. We find many similarities
between the 3C129 X-ray jet and recent jet detections from Chandra data of low
luminosity radio galaxies. For most of these current detections synchrotron
emission is the favored explanation for the observed X-rays.


title:
A Relativistic Fe K-alpha Emission Line in the Intermediate Luminosity
  BeppoSAX Spectrum of the Galactic Microquasar V4641 Sgr

abstract:
  Broad Fe K-alpha emission lines have recently been reported in a number of
Galactic black holes. Such lines are useful accretion flow diagnostics because
they may be produced at the inner accretion disk and shaped by relativistic
effects, but in general they have only been observed at luminosities of L_X ~
10^(37-38) erg/s in soft X-rays. The Galactic microquasar V4641 Sgr -- widely
known for its 12.2 Crab (1.5-12 keV) outburst in 1999 September -- displayed
low-level activity in 1999 March. BeppoSAX observed the source in this state
and Fe K-alpha line emission was found (in 't Zand et al. 2000). In
re-analyzing these data, we find strong evidence that the Fe K-alpha line
profile is broadened. For the most likely values of the source distance and
black hole mass measured by Orosz et al. (2001), our fits to the total spectrum
indicate that the source was observed at a luminosity of L_X = 1.9 (+1.0, -0.8)
* 10^(36) erg/s (2-10 keV), or L_X/L_Edd. = 1.8 (+0.9, -0.8) * 10^(-3).
Advection-dominated accretion flow (ADAF) models predict a radially-recessed
disk in this regime. In contrast, fits to the observed Fe K-alpha emission line
profile with a relativistic line model constrain the inner disk to be
consistent with the marginally stable circular orbit of a Schwarzschild black
hole.


title: The Color Distribution in the Edgeworth-Kuiper Belt

abstract:
  We have started since 1997 the Meudon Multicolor Survey of Outer Solar System
Objects with the aim of collecting a large and homogeneous set of color data
for Trans-Neptunian and Centaurs objects [...] We have a combined sample of 52
B-R color measurements for 8 Centaurs, 22 Classicals, 13 Plutinos, 8 Scattered
objects and 1 object with unidentified dynamical class. This dataset is the
largest single and homogeneous published dataset to date [...]. A strong
(color) correlation with mean excitation velocity points toward a space
weathering/impact origin for the color diversity. However, thorough modeling of
the collisional/dynamical environment in the Edgeworth-Kuiper belt needs to be
done in order to confirm this scenario. We found also that the Classical TNOs
consist in the superposition of two distinct populations: the dynamically Cold
Classical TNOs (red colors, low i, small sizes) and the dynamically Hot
Classical TNOs (diverse colors, moderate and high i, larger sizes). [...] Our
specific observation strategy [...] permitted us to highlight a few objects
suspected to have true compositional and/or texture variation on their
surfaces. These are 1998 HK151, 1999 DF9, 1999 OY3, 2000 GP183, 2000 OK67, and
2001 KA77 and should be prime targets for further observations [...]. Our
survey has also highlighted 1998 SN165 whose colors and dynamical properties
puts it in a new dynamical class distinct from the Classicals, its previously
assigned dynamical class.


title: Cold Fronts in CDM clusters

abstract:
  Recently, high-resolution Chandra observations revealed the existence of very
sharp features in the X-ray surface brightness and temperature maps of several
clusters (Vikhlinin et. al., 2001). These features, called ``cold fronts'', are
characterized by an increase in surface brightness by a factor >2 over 10-50
kpc, accompanied by a drop in temperature of a similar magnitude. The existence
of such sharp gradients can be used to put interesting constraints on the
physics of the intracluster medium (ICM), if their mechanism and longevity are
well understood. Here, we present results of a search for cold fronts in
high-resolution simulations of galaxy clusters in cold dark matter (CDM)
models. We show that sharp gradients with properties similar to those of
observed cold fronts naturally arise in cluster mergers when the shocks heat
gas surrounding the merging sub-cluster, while its dense core remains
relatively cold. The compression induced by supersonic motions and shock
heating during the merger enhance the amplitude of gas density and temperature
gradients across the front. Our results indicate that cold fronts are
non-equilibrium transient phenomena and can be observed for a period of less
than a billion years. We show that the velocity and density fields of gas
surrounding the cold front can be very irregular which would complicate
analyses aiming to put constraints on the physical conditions of the
intracluster medium in the vicinity of the front.


title: An unusually low mass of some "neutron" stars?

abstract:
  The X-ray emission of RXJ1856.5-3754 has been found to coincide to
unprecedented accuracy with that of a blackbody, of radius 5.8+-0.9 km for the
measured parallax distance of 140 pc (Burwitz et al. 2001, Drake et al. 2002).
If the emission is uniform over the whole surface of a non-rotating star, the
mass of the star cannot exceed 0.75+-0.12 solar mass regardless of its
composition. If the compact object is a quark star described by the MIT-bag
equation of state (a ``strange star''), the mass is no more than 0.3 solar
mass. Comparably small masses are also obtained for the X-ray bursters Aql X-1
and KS1731-260 for some fits to their spectra.


title: Neutrino oscillation mechanism for pulsar kicks reexamined

abstract:
  Anisotropic neutrino emission during the neutron star formation can be the
origin of the observed proper motions of pulsars. We derive a general
expression for the momentum asymmetry in terms of the neutrino energy flux
gradient, and show that a nonvanishing effect is induced at the lowest order by
a deformed neutrinosphere. In particular, this result is valid for a neutrino
flux transported through a spherical atmosphere with constant luminosity.


title: Chandra observation of the central galaxies in A1060 cluster of galaxies

abstract:
  Chandra observation of the central region of the A1060 cluster of galaxies
resolved X-ray emission from two giant elliptical galaxies, NGC 3311 and NGC
3309. The emission from these galaxies consists of two components, namely the
hot interstellar medium (ISM) and the low-mass X-ray binaries (LMXBs). We found
the spatial extent of the ISM component was much smaller than that of stars for
both galaxies, while the ratios of X-ray to optical blue-band luminosities were
rather low but within the general scatter for elliptical galaxies. After
subtracting the LMXB component, the ISM is shown to be in pressure balance with
the intracluster medium of A1060 at the outer boundary of the ISM. These
results imply that the hot gas supplied from stellar mass loss is confined by
the external pressure of the intracluster medium, with the thermal conduction
likely to be suppressed. The cD galaxy NGC 3311 does not exhibit the extended
potential structure which is commonly seen in bright elliptical galaxies, and
we discuss the possible evolution history of the very isothermal cluster A1060.


title: Lithium Abundances in Wide Binaries with Solar-Type Twin Components

abstract:
  We present high-resolution spectroscopic observations of the \ion{Li}{1}
resonance line in a sample of 62 stars that belong to 31 common-proper motion
pairs with twin F or G-type components. Photospheric abundances of lithium were
derived by spectral synthesis analysis. For seven of the pairs, we have
measured large lithium abundance differences. Eleven other pairs have
components with similar lithium abundances. We cannot determine if the
remaining 13 pairs have lithium differences because we did not detect the
\ion{Li}{1} lines, and hence we can only provide upper limits to the abundances
of both stars. Our results demonstrate that twin stars do not always share the
same lithium abundances. Lithium depletion in solar-type stars does not only
depend on age, mass, and metallicity. This result is consistent with the spread
in lithium abundances among solar-type stars in the solar-age open cluster M67.
Our stars are brighter than the M67 members of similar spectral type, making
them good targets for detailed follow-up studies that could shed light on the
elusive mechanism responsible for the depletion of lithium during the
main-sequence evolution of the Sun and solar-type stars.


title:
A Time Evolution Study of the Superhumps of the Dwarf Nova 1RXS
  J232953.9+062814 by Wavelet Transform

abstract:
  The time evolution behaviour of the superhumps of the dwarf nova 1RXS
J232953.9+062814 is investigated with the wavelet analysis method. On the basis
of two nights CCD photometry performed during its first superoutburst as well
as other published brightness data, we reveal the superhump's time-dependence
as a function of periods and time. Our light curves, which phased in the rapid
decay ending portion of the superoutburst and in the dawn of a following normal
outburst, are important to help trace the superhump evolution for the star.
Evident amplitude variations of the superhumps, reflecting the fading of
outbursts, are detected. The general profile of brightness fading over the
outbursts roughly followed an exponential decay law or a form of a five-order
polynomial. Both the superhump period and the orbital period of the binary
system are detected in the present data. We obtain P_sh=0.04575(5) d and
P_orb=0.04496(5) d. They agree with the existing values based on additional
data. The two periods exchanged their roles during the superhump evolution.


title:
The absence of the 10 um silicate feature in the isolated Herbig Ae star
  HD 100453

abstract:
  We analyse the optical and IR spectra, as well as the spectral energy
distribution (UV to mm) of the candidate Herbig Ae star HD100453. This star is
particular, as it shows an energy distribution similar to that of other
isolated Herbig Ae/Be stars (HAEBEs), but unlike most of them, it does not have
a silicate emission feature at 10 um, as is shown in Meeus (2001). We confirm
the HAEBE nature of HD100453 through an analysis of its optical spectrum and
derived location in the H-R diagram. The IR spectrum of HD100453 is modelled by
an optically thin radiative transfer code, from which we derive constraints on
the composition, grain-size and temperature distribution of the circumstellar
dust. We show that it is both possible to explain the lack of the silicate
feature as (1) a grain-size effect - lack of small silicate grains, and (2) a
temperature effect - lack of small, hot silicates, as proposed by Dullemond
(2001), and discuss both possibilities.


title:
A turn-over scenario for rotating magnetic white dwarfs: models with
  several values of mass, angular momentum, and magnetic field

abstract:
  We study a white dwarf with differential rotation and magnetic field, for
which the symmetry axis of the toroidal field, the magnetic axis of the
poloidal field, and the principal axis I_3 coincide permanently. This common
axis, so-called "magnetic symmetry axis", inclines at a small angle relative to
the spin axis of the model, the so-called "turn-over angle". Such an almost
axisymmetric model undergoes an early evolutionary phase of secular timescale,
with moment of inertia along the spin axis, I_{zz}=I_{33}, greater than the
moments of inertia along the equatorial axes, I_{11}=I_{22}, since rotation and
poloidal field (both deriving oblate configurations) dominate over the toroidal
field (deriving prolate configurations). During this phase, the model suffers
from secular angular momentum loss due to weak magnetic dipole radiation
activated by the poloidal field, leading gradually to "dynamical asymmetry"
with I_{11}>I_{33}. However, a dynamically asymmetric configuration tends to
turn over spontaneously, i.e., to rotate about axis with moment of inertia
greater than I_{33}, with angular momentum remaining invariant. So, the fate of
a dynamically asymmetric configuration is to become an oblique rotator and,
eventually, a perpendicular rotator. During the so-called "turn-over phase",
the turn-over angle increases spontaneously up to 90 degrees on a "turn-over
timescale" t_{TOV}. In the present paper, we study numerically the turn-over
phase for models of several masses, angular momenta, and magnetic fields.


title: Unveiling Dark Matter with HI and Halpha Data - Observational Problems

abstract:
  We present combined Halpha+HI rotation curves for a sample of spiral
galaxies. Most of the velocity profiles (spectra at single points) in these
galaxies are asymmetric, preventing the use of standard methods like the first
moment analysis and the single Gaussian fitting. We thus propose a method
similar to the Envelope-Tracing method (Sofue & Rubin 2001) to analyse those
profiles from which we obtain HI rotation curves in good agreement with the
Halpha rotation curves. These final rotation curves provide the required high
resolution in the inner parts of the galaxies, but also extend out to typically
2-3 optical radii. They will hence allow us to investigate the distribution of
dark matter.


title:
On the resolved radio emission from AG Draconis: evidence for jet
  ejection?

abstract:
  The recent detection of resolved radio emission from AG Dra by MERLIN
reported by Ogley et al. is discussed in the context of the wind environment
and the physical parameters and geometry of this symbiotic binary system. In
particular, it is shown that the two radio components are closely aligned with
the binary axis, and their separation suggests their origin in jets ejected
from AG Dra during the recent 1995--98 series of oubtbursts.


title: Angular momentum extraction by gravity waves in the Sun

abstract:
  We review the behavior of the oscillating shear layer produced by gravity
waves below the surface convection zone of the Sun. We show that, under
asymmetric filtering produced by this layer, gravity waves of low spherical
order, which are stochastically excited at the base of the convection zone of
late type stars, can extract angular momentum from their radiative interior.
The time-scale for this momentum extraction in a Sun-like star is of the order
of 10^7 years. The process is particularly efficient in the central region, and
it could produce there a slowly rotating core.


title:
Soft X-ray emission lines in the afterglow spectrum of GRB 011211:- a
  detailed XMM-Newton analysis

abstract:
  We report on an XMM-Newton observation of the X-ray afterglow of the Gamma
Ray Burst GRB 011211, originally detected by Beppo-SAX on 11th December 2001.
The early afterglow spectrum obtained by XMM-Newton, observed 11 hours after
the initial burst, appeared to reveal decaying H-like K emission lines of Mg,
Si, S, Ar and Ca, arising in enriched material with an outflow velocity of
order 0.1c (Reeves et al. 2002). This was attributed to matter ejected from a
massive stellar progenitor occurring shortly before the burst itself. Here, we
present a detailed re-analysis of the XMM-Newton EPIC observations of GRB
011211. In particular, we show that the detection of the soft X-ray line
emission appears robust, regardless of detector background, calibration,
spectral binning, or the spectral model that is assumed. We demonstrate that
thermal emission, from an optically thin plasma, is the most plausible model
that can account for the soft X-ray emission, which appears to be the case for
at least two burst afterglow spectra observed by XMM-Newton. The X-ray spectrum
of GRB 011211 evolves with time over the first 12 ksec of the XMM-Newton
observation, the observations suggest that thermal emission dominates the early
afterglow spectrum, whilst a power-law component dominates the latter stages.
Finally we estimate the mass of the ejected material in GRB 011211 to be of the
order 4-20 solar masses.


title: Warps and Rotation Curves in Edge-On Galaxies

abstract:
  We present our investigation on the effect of warps on the extraction of
rotation curves in edge-on galaxies. The method to derive the rotation curve
from the position-velocity diagram in warped edge-on systems yields
underestimated velocities, and the tilted-ring model is not reliable in highly
inclined, poorly resolved galaxies. In a warped system the kinematical major
axis is different from the optical major axis. While this is generally a limit
in optical slit spectroscopy, in the HI emission which extends far from the
optical body where self-gravity is weaker and the effect of warping is more
pronounced, this represents a severe effect to be considered in the procedure
to extract the rotation curve. We propose a new approach to extract the
rotation curve in highly inclined, warped galaxies. Based on this method we are
able to trace accurately the frequency of peculiarities in our sample of Thick
Boxy Bulge (TBB) galaxies. We report an increasing trend of kinematical
lopsidedness from spheroidal bulge galaxies towards TBB galaxies. Concerning
the question whether interactions contribute significantly to the bar formation
and to the subsequent evolution in a box/peanut (b/p) structure, we confirm
these theoretical predictions. Based on our sample, galaxy interaction is the
likely formation mechanism to trigger bars in TBB galaxies.


title: The BeppoSAX view of extreme BL Lacs

abstract:
  With its very wide energy band (0.1-100 keV), BeppoSAX has played a
fundamental role in the blazar field, allowing in particular a better study of
the highest synchrotron peaked objects. Here we summarize the results of an
observational program performed with the aim to find and study more extreme BL
Lac sources. We discuss the SEDs of the observed objects and their impact on
the "blazar sequence" scenario, and consider their relevance as possible TeV
emitting sources.


title: How Sensitive Are Weak Lensing Statistics to Dark Energy Content?

abstract:
  Future weak lensing surveys will directly probe the clustering of dark
matter, in addition to providing a test for various cosmological models. Recent
studies have provided us with the tools which can be used to construct the
complete probability distribution function for convergence fields. It is also
possible to construct the bias associated with the hot-spots in convergence
maps. These techniques can be used in both the quasi-linear and the highly
nonlinear regimes using various well developed numerical methods. We use these
results here to study the weak lensing statistics of cosmological models with
dark energy. We study how well various classes of dark energy models can be
distinguished from models with a cosmological constant. We find that the ratio
of the square root of the variance of convergence is complementary to the
convergence skewness $S_3$ in probing dark energy equation of state; it can be
used to predict the expected difference in weak lensing statistics between
various dark energy models, and for choosing optimized smoothing angles to
constrain a given class of dark energy models. Our results should be useful for
probing dark energy using future weak lensing data with high statistics from
galaxy weak lensing surveys and supernova pencil beam surveys.


title:
Model for Synchrotron Emission from Shell Supernova Remnants in
  Nonuniform Interstellar Medium and Nonuniform Magnetic Field

abstract:
  Possibility to model the high energy synchrotron emission (in X- and
gamma-rays) from supernova remnants is an important task for modern astronomy
and astrophysics, because it may be responsible for the nonthermal X-rays and
TeV gamma-rays observed recently from a number of SNRs. This emission allows as
to look in the processes of particle acceleration on SNR shocks and generation
of cosmic rays. In this paper, a model for the synchrotron emission from shell
SNR in nonuniform interstellar medium and nonuniform magnetic field is
presented. This model is a generalization of the model of Reynolds and
Chevalier developed for a spherical SNR in the uniform medium and uniform
magnetic field. The model will be used for studies on the thermal and
nonthermal X-ray images and spectra from nonspherical SNRs in different
interstellar magnetic field configurations.


title: Noise and the strong signal limit in radio astronomical measurement

abstract:
  The random error of radioastronomical measurements is usually computed in the
weak-signal limit, which assumes that the system temperature is sensibly the
same on and off source, or with and without a spectral line. This assumption is
often very poor. We give examples of common situations in which it is important
to distinguish the system noise in signal-bearing and signal-free regions.


title:
Coordinated thermal and optical observations of Trans-Neptunian object
  (20000) Varuna from Sierra Nevada

abstract:
  We report on coordinated thermal and optical measurements of trans-Neptunian
object (20000) Varuna obtained in January-February 2002, respectively from the
IRAM 30-m and IAA 1.5 m telescopes. The optical data show a lightcurve with a
period of 3.176+/-0.010 hr, a mean V magnitude of 20.37+/-0.08 and a
0.42+/-0.01 magnitude amplitude. They also tentatively indicate that the
lightcurve is asymmetric and double-peaked. The thermal observations indicate a
1.12+/-0.41 mJy flux, averaged over the object's rotation. Combining the two
datasets, we infer that Varuna has a mean 1060(+180/-220) km diameter and a
mean 0.038(+0.022/-0.010) V geometric albedo, in general agreement with an
earlier determination using the same technique.


title: Search for Neutrino-Induced Cascades with the AMANDA Detector

abstract:
  We report on a search for electromagnetic and/or hadronic showers (cascades)
induced by a diffuse flux of neutrinos with energies between 5 TeV and 300 TeV
from extraterrestrial sources. Cascades may be produced by matter interactions
of all flavors of neutrinos, and contained cascades have better energy
resolution and afford better background rejection than through-going
\nu_\mu-induced muons. Data taken in 1997 with the AMANDA detector were
searched for events with a high-energy cascade-like signature. The observed
events are consistent with expected backgrounds from atmospheric neutrinos and
catastrophic energy losses from atmospheric muons. Effective volumes for all
flavors of neutrinos, which allow the calculation of limits for any neutrino
flux model, are presented. The limit on cascades from a diffuse flux of
\nu_e+\nu_\mu+\nu_\tau+\bar{\nu}_e+\bar{\nu}_\mu+\bar{\nu}_\tau is E^2 d\Phi/dE
< 9.8 x 10^{-6} GeV/(cm^2 s sr), assuming a neutrino flavor flux ratio of 1:1:1
at the detector. The limit on cascades from a diffuse flux of \nu_e+\bar{\nu}_e
is E^ d\Phi/dE < 6.5 x 10{-6} GeV/(cm^2 s sr), independent of the assumed
neutrino flavor flux ratio.


title:
Cosmological Acceleration Through Transition to Constant Scalar
  Curvature

abstract:
  As shown by Parker and Raval, quantum field theory in curved spacetime gives
a possible mechanism for explaining the observed recent acceleration of the
universe. This mechanism, which differs in its dynamics from quintessence
models, causes the universe to make a transition to an accelerating expansion
in which the scalar curvature, R, of spacetime remains constant. This
transition occurs despite the fact that we set the renormalized cosmological
constant to zero. We show that this model agrees very well with the current
observed type-Ia supernova (SNe-Ia) data. There are no free parameters in this
fit, as the relevant observables are determined independently by means of the
current cosmic microwave background radiation (CMBR) data. We also give the
predicted curves for number count tests and for the ratio, w(z), of the dark
energy pressure to its density, as well as for dw(z)/dz versus w(z). These
curves differ significantly from those obtained from a cosmological constant,
and will be tested by planned future observations.


title:
Observations of the Magnetic Cataclysmic Variable VV Puppis with the Far
  Ultraviolet Spectroscopic Explorer

abstract:
  We present the first far-ultraviolet (FUV) observations of the magnetic
cataclysmic variable VV Puppis, obtained with the Far Ultraviolet Spectroscopic
Explorer satellite. In addition, we have obtained simultaneous ground-based
optical photometric observations of VV Pup during part of the FUV observation.
The shapes of the FUV and optical light curves are consistent with each other
and with those of past observations at optical, extreme-ultraviolet, and X-ray
wavelengths. Time-resolved FUV spectra during the portion of VV Pup's orbit
when the accreting magnetic pole of the white dwarf can be seen show an
increasing continuum level as the accretion spot becomes more directly visible.
The most prominent features in the spectrum are the O VI 1031.9A, 1037.6A
emission lines. We interpret the shape and velocity shift of these lines in the
context of an origin in the accretion funnel near the white dwarf surface. A
blackbody function with T > 90,000 K provides an adequate fit to the FUV
spectral energy distribution of VV Pup.


title: Evidence for a 2:3 resonance in Sco X-1 kHz QPOs

abstract:
  We find evidence that the two high frequency QPOs in Sco X-1 are, more often
than not, approximately in the 2:3 frequency ratio familiar from studies of
black hole candidates (e.g., XTE J1550-564, Remillard et al. 2002). This
implies that the double kHz QPO phenomenon in neutron stars has its origin in
properties of strong-field gravity and has little to do with the rotation of a
stellar surface or any magnetic field structure anchored in the star.


title: Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305

abstract:
  We report the discovery by the RXTE PCA of a second transient accreting
millisecond pulsar, XTE J1751-305, during regular monitoring observations of
the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it
one of the fastest pulsars. The pulsations contain the signature of orbital
Doppler modulation, which implies an orbital period of 42 minutes, the shortest
orbital period of any known radio or X-ray millisecond pulsar. The mass
function, f_x = (1.278 +/- 0.003) x 10^{-6} M_sun, yields a minimum mass for
the companion of between 0.013 and 0.017 M_sun, depending on the mass of the
neutron star. No eclipses were detected. A previous X-ray outburst in June,
1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer
in this binary system is driven by gravitational radiation, we constrain the
orbital inclination to be in the range 30-85 deg, and the companion mass to be
0.013-0.035 M_sun. The companion is most likely a heated helium dwarf. We also
present results from the Chandra HRC-S observations which provide the best
known position of XTE J1751-305.


title: An Isolated, Recently Shocked ISM Cloud in the Cygnus Loop SNR

abstract:
  Spatially resolved ROSAT X-ray and ground-based optical data for the
southwestern region of the Cygnus Loop SNR reveal in unprecedented detail the
very early stages of a blast wave interaction with an isolated interstellar
cloud. Numerous internal cloud shock fronts near the upstream flow and along
the cloud edges are visible optically as sharp filaments of enhanced H-alpha
emission. Faint X-ray emission is seen along a line of Balmer-dominated shock
filaments north and south of the cloud with an estimated X-ray gas temperature
of 1.2 x 10^6 K (0.11 keV) corresponding to a shock velocity of 290 km s^-1.
The main cloud body itself exhibits little or no X-ray flux. Instead, X-ray
emission is confined along the northern and southernmost cloud edges, with the
emission brightest in the downstream regions farthest from the shock front's
current position. We estimate an interaction age of around 1200 yr based on the
observed shock/cloud morphology. Overall, the optical and X-ray properties of
this shocked ISM cloud show many of the principal features predicted for a
young SNR shock -- ISM cloud interaction. In particular, one sees shocklet
formation and diffraction inside the inhomogenous cloud along with partial main
blast wave engulfment. However, several significant differences from model
predictions are also present including no evidence for turbulence along cloud
edges, diffuse rather than filamentary [O III] emission within the main body of
the cloud, unusually strong downstream [S II] emission in the postshock cloud
regions, and confinement of X-ray emission to the cloud's outer boundaries.


title:
Discovery of a High-Latitude Accreting Millisecond Pulsar in an
  Ultracompact Binary

abstract:
  We have identified the third known accretion-powered millisecond pulsar, XTE
J0929-314, with the Rossi X-Ray Timing Explorer. The source is a faint,
high-Galactic-latitude X-ray transient (d >~ 5 kpc) that was in outburst during
2002 April-June. The 185 Hz (5.4 ms) pulsation had a fractional rms amplitude
of 3-7% and was generally broad and sinusoidal, although occasionally
double-peaked. The hard X-ray pulses arrived up to 770 microseconds earlier
than the soft X-ray pulses. The pulsar was spinning down at an average rate of
-(9.2 +/- 0.4) * 10^-14 Hz/s; the spin-down torque may arise from magnetic
coupling to the accretion disk, a magnetohydrodynamic wind, or gravitational
radiation from the rapidly spinning pulsar. The pulsations were modulated by a
43.6 min ultracompact binary orbit, yielding the smallest measured mass
function (2.7 * 10^-7 M_sun) of any stellar binary. The binary parameters imply
an approximately 0.01 M_sun white dwarf donor and a moderately high
inclination. We note that all three known accreting millisecond pulsars are
X-ray transients in very close binaries with extremely low mass transfer rates.
This is an important clue to the physics governing whether or not persistent
millisecond pulsations are detected in low-mass X-ray binaries.


title: Microlensing Constraints on Low-Mass Companions

abstract:
  Microlensing is sensitive to binary, brown dwarf, and planetary companions to
normal stars in the Galactic bulge with separations between about 1-10 AU. The
accurate, densely-sampled photometry of microlensing events needed to detect
planetary companions has been achieved by several follow-up collaborations.
Detailed analysis of microlensing events toward the bulge demonstrates that
less than 45% of M-dwarfs in the bulge have Jupiter-mass companions between 1
and 5 AU. Detection of binary and brown-dwarf companions using microlensing is
considerably easier; however, the interpretation is hampered by their
non-perturbative influence on the parent lightcurve. I demonstrate that ~25% of
brown-dwarf companions with separations 1-10 AU should be detectable with
survey-quality data (~1 day sampling and ~5% photometry). Survey data is more
amenable to generic, brute-force analysis methods and less prone to selection
biases. An analysis of the ~1500 microlensing events detected by OGLE-III in
the next three years should test whether the BD desert exists at separations
1-10 AU from M-dwarfs in the Galactic bulge.


title:
Using Strong Lines to Estimate Abundances in Extragalactic HII Regions
  and Starburst Galaxies

abstract:
  We have used a combination of stellar population synthesis and
photoionization models to develop a set of ionization parameter and abundance
diagnostics based only on the use of the strong optical emission lines. These
models are applicable to both extragalactic HII regions and star-forming
galaxies. We show that, because our techniques solve explicitly for both the
ionization parameter and the chemical abundance, the diagnostics presented here
are an improvement on earlier techniques based on strong emission-line ratios.
Our techniques are applicable at all metallicities. In particular, for
metallicities above half solar, the ratio [NII]/[OII] provides a very reliable
diagnostic since it is ionization parameter independant and does not have a
local maximum. This ratio has not been used historically because of worries
about reddening corrections. However, we show that the use of classical
reddening curves is quite sufficient to allow this [NII]/[OII] diagnostic to be
used with confidence as a reliable abundance indicator. The cause of systematic
and random errors inherent in previous techniques are discussed, and we present
a new `optimal' abundance diagnostic method based on the use of line ratios
involving [NII], [OII], [OIII], [SII] and the Balmer lines. This combined
diagnostic appears to suffer no apparent systematic errors, can be used over
the entire abundance range and significantly reduces the random error inherent
in previous techniques. Finally, we give a recommended procedure for the
derivation of abundances in the case that only spectra of limited wavelength
coverage are available so that the optimal method can no longer be used.


title: Rethinking Lensing and Lambda

abstract:
  Strong gravitational lensing has traditionally been one of the few phenomena
said to oppose a large cosmological constant; many analyses of lens statistics
have given upper limits on $\Omega_\Lambda$ that are marginally inconsistent
with the concordance cosmology. Those conclusions were based on models where
the predicted number counts of galaxies at moderate redshifts (z~0.5-1)
increased significantly with $\Omega_\Lambda$. I argue that the models should
now be calibrated by counts of distant galaxies. When this is done lens
statistics lose most of their sensitivity to the cosmological constant.


title:
Characterizing the Warm-Hot IGM at High Redshift: A High Resolution
  Survey for O VI at z = 2.5

abstract:
  We describe a survey for OVI absorption in the spectra of 5 high redshift
quasars (2.2 < z < 2.8). We identify 12 cosmological systems, and 6 systems
that are either ejected from the background QSO or affected by its local
radiation field. Almost all of the intergalactic OVI is associated with strong
Ly-a absorption (N_HI > 10^15.2 cm^-2), as well as absorption from CIV and
often lower ionization species. The absorbing regions are conservatively
constrained to have L<=200 kpc and rho/rho_bar >= 2.5, with actual values
probably closer to L ~ 60 kpc and rho/rho_bar ~ 10-30. They also have two
distinct gas phases: one which produces photoionized CIV and SiIV at T ~ 30,000
K, and a second which is seen only in OVI. The OVI temperature is difficult to
constrain due to uncertainty in the amount of nonthermal line broadening, but
it does appear that this gas is hotter than the CIV/SiIV phase and could
support collisional OVI production. The OVI is strongly clustered on velocity
scales of dv=100-300 km/s, with weaker signal extending to dv = 750 km/s. The
power-law slope of the correlation function resembles that of local galaxy and
cluster surveys, with a comoving correlation length of 11h_{65}^-1 Mpc. The
average Oxygen abundance of the OVI systems is [O/H]>-1.5, about 10 times
higher than the level observed in the general IGM. Two OVI production
mechanisms are considered: shock heating of gas falling onto existing
structure, and expulsion of material by galactic winds. Simulations of infall
models tend to overproduce OVI lines by a factor of ~10, though this may result
from numerical limitations. Known galaxy populations such as the Lyman break
objects could produce the observed amount of OVI if they drive winds to
distances of R ~ 50 kpc.


title: Kinematics of Gamma-Ray Bursts and their Relationship to Afterglows

abstract:
  A strong correlation is reported between gamma-ray burst (GRB) pulse lags and
afterglow jet-break times for the set of bursts (seven) with known redshifts,
luminosities, pulse lags, and jet-break times. This may be a valuable clue
toward understanding the connection between the burst and afterglow phases of
these events. The relation is roughly linear (i.e. doubling the pulse lag in
turn doubles the jet break time) and thus implies a simple relationship between
these quantities. We suggest that this correlation is due to variation among
bursts of emitter Doppler factor. Specifically, an increased speed or decreased
angle of velocity, with respect to the observed line-of-site, of burst ejecta
will result in shorter perceived pulse lags in GRBs as well as quicker
evolution of the external shock of the afterglow to the time when the jet
becomes obvious, i.e. the jet-break time. Thus this observed variation among
GRBs may result from a perspective effect due to different observer angles of a
morphologically homogeneous populations of GRBs.
  Also, a conjecture is made that peak luminosities not only vary inversely
with burst timescale, but also are directly proportional to the spectral break
energy. If true, this could provide important information for explaining the
source of this break.


title: Early GeV afterglows from gamma-ray bursts in pulsar wind bubbles

abstract:
  Gamma-ray bursts may occur within pulsar wind bubbles (PWBs) under a number
of scenarios, such as the supranova-like models in which the progenitor pulsar
drives a powerful wind shocking against the ambient medium before it comes to
death and produces a fireball. We here study the early afterglow emission from
GRBs expanding into such a PWB environment. Different from the usual cold GRB
external medium, the PWBs consist of a hot electron-positron medium with
typical 'thermal' Lorentz factor of the order of gamma_w, the Lorentz factor of
the pulsar particle wind. After GRB blast waves shock these hot
electron-positron pairs, they will emit synchrotron radiation peaking at GeV
bands. It is shown that GeV photons suffer negligible absorption by the soft
photons radiation field in PWBs. Thus, strong GeV emissions in the early
afterglow phases are expected, providing a plausible explanation for the
long-duration GeV emission from GRB940217 detected by EGRET. Future GLAST may
have the potential to test this GRB-PWB interaction model.


title:
On the metallicity of the Milky Way thin disc and photometric abundance
  scales

abstract:
  The mean metallicity of the Milky Way thin disc in the solar neighbourhood is
still a matter of debate, and has recently been subject to upward revision
(Haywood, 2001). Our star sample was drawn from a set of solar neighbourhood
dwarfs with photometric metallicities. In a recent study, Reid (2002) suggests
that our metallicity calibration, based on Geneva photometry, is biased. We
show here that the effect detected by Reid is not a consequence of our adopted
metallicity scale, and we confirm that our findings are robust. On the
contrary, the application to Stromgren photometry of the Schuster & Nissen
metallicity scale is problematic. Systematic discrepancies of about 0.1 to 0.3
dex affect the photometric metallicity determination of metal rich stars, on
the colour interval 0.22< b-y <0.59, i.e including F and G stars. For F stars,
it is shown that this is a consequence of a mismatch between the standard
sequence m_1(b-y) of the Hyades used by Schuster & Nissen to calibrate their
metallicity scale, and the system of Olsen (1993, 1994ab). It means that
although Schuster & Nissen calibration and Olsen photometry are intrinsically
correct, there are mutually incompatible for metal rich, F-type stars. For G
stars, the discrepancy is most probably the continuation of the same problem,
albeit worthen by the lack of spectroscopic calibrating stars. A corrected
calibration is proposed which renders the calibration of Schuster & Nissen
applicable to the catalogues of Olsen. We also give a simpler calibration
referenced to the Hyades sequence, valid over the same color and metallicity
ranges.


title:
Testing for non-Gaussianity of the cosmic microwave background in
  harmonic space: an empirical process approach

abstract:
  We present a new, model-independent approach for measuring non-Gaussianity of
the Cosmic Microwave Background (CMB) anisotropy pattern. Our approach is based
on the empirical distribution function of the normalized spherical harmonic
expansion coefficients a_lm of a nearly full-sky CMB map, like the ones
expected from forthcoming satellite experiments. Using a set of
Kolmogorov-Smirnov type tests, we check for Gaussianity and independency of the
a_lm. We test the method on two non-Gaussian toy-models of the CMB, one
generated in spherical harmonic space and one in pixel (real) space. We also
provide some rigorous results, possibly of independent interest, on the exact
distribution of the spherical harmonic coefficients normalized by an estimated
angular power spectrum.


title:
General Relativistic Electromagnetism and Particle Acceleration in
  Pulsar Polar Cap

abstract:
  We reconstruct a 3+1 formalism of general relativistic electromagnetism, and
derive the equations of motion of charged particles in the pulsar
magnetosphere, taking account of the inclination between the rotation axis and
the magnetic axis. Apart from the previous works where space charge is
evaluated by assuming the flow velocity being the light speed, we analyze
particle motion in the polar cap, finding that gravity changes significantly
its dynamics and the condition for acceleration.


title:
Optical Gravitational Lensing Experiment. OGLE-1999-BUL-19: The First
  Multi-Peak Parallax Event

abstract:
  We describe a highly unusual microlensing event, OGLE-1999-BUL-19, which
exhibits multiple peaks in its light curve. The Einstein radius crossing time
for this event is approximately one year, which is unusually long. We show that
the motion of the Earth induces these multiple peaks in the light curve, since
the relative transverse velocity of the lens projected into the observer plane
is very small (v = 12.5 km/s). This is the lowest velocity so far published and
we believe that this is the first multiple-peak parallax event ever observed.
We also believe that this event may be exhibiting slight binary-source
signatures in addition to these parallax-induced multiple peaks. With
spectroscopic observations it is possible to test this `parallax plus
binary-source' hypothesis and (if this hypothesis turns out to be correct) to
simultaneously fit both models and obtain a measurement of the lens mass.
Furthermore, spectroscopic observations could also supply information regarding
the lens properties, possibly providing another avenue for determining the lens
mass. We found that most of the I-band blending is probably caused by light
from the lens or a binary companion to the source. However, in the V-band,
there appears to be a second blended source 0.35" away from the lensed source.
HST observations will be very useful for understanding the nature of the
blends. We also suggest that a radial velocity survey of all parallax events
will be very useful for further constraining the lensing kinematics and
understanding the origins of these events and the excess of long events toward
the bulge.


title: On the heating of source of the Orion KL hot core

abstract:
  We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and $>230$ K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.


title: Ultra-high Energy Cosmic Rays: a probe into New Physics

abstract:
  The most energetic particles ever detected exceed $10^{20}$ eV in energy.
Their existence represents at the same time a great challenge for particle
physics and astrophysics, and a great promise of providing us for a probe of
the validity of the laws of Nature in extreme conditions. We review here the
most recent data and the future perspectives for detection of cosmic rays at
ultra-high energies, and discuss possible ways of using these data to test the
possibility that new Physics and/or new Astrophsyics may be awaiting around the
corner.


title: The INTEGRAL Science Data Centre

abstract:
  The INTEGRAL Science Data Centre (ISDC) processes, archives and distributes
data from the INTEGRAL mission. At the ISDC incoming data from the satellite
are processed and searched for transient sources and Gamma-Ray bursts. The data
are archived and distributed to the guest observers. As soon as the data are
public, any astronomer can access the data via the internet. ISDC also provides
the tools which are necessary for the data analysis and offers user support
concerning questions related to the INTEGRAL data. ISDC acts as a contacting
point between the scientific community and the various instrument teams. In
this article an example for SPI data processing is shown.


title:
Halo Concentrations and Weak-Lensing Number Counts in Dark Energy
  Cosmologies

abstract:
  We study the effects of a dark energy component with equation of state p=w
rho with constant w >= -1 on the formation of Cold Dark Matter (CDM) haloes. We
find two main effects: first, haloes form earlier as w increases, and second,
the amplitude of the dark-matter power spectrum gets reduced in order to remain
compatible with the large scale Cosmic Microwave Background (CMB) anisotropies.
These effects counteract. Using recipes derived from numerical simulations, we
show that haloes are expected to be up to ~ 50% more concentrated in CDM models
with quintessence compared to Lambda-CDM models, the maximum increase being
reached for w ~ -0.6. For larger w, the amplitude of the power spectrum
decreases rapidly and makes expected halo concentrations drop. Halo detections
through weak gravitational lensing are highly sensitive to halo concentrations.
We show that weak-lensing halo counts with the aperture-mass technique can
increase by a factor of ~ 2 as w is increased from -1 to -0.6, offering a new
method for constraining the nature of dark energy.


title: Halo Models of Large Scale Structure

abstract:
  We review the formalism and applications of the halo-based description of
nonlinear gravitational clustering. In this approach, all mass is associated
with virialized dark matter halos; models of the number and spatial
distribution of the halos, and the distribution of dark matter within each
halo, are used to provide estimates of how the statistical properties of large
scale density and velocity fields evolve as a result of nonlinear gravitational
clustering. We first describe the model, and demonstrate its accuracy by
comparing its predictions with exact results from numerical simulations of
nonlinear gravitational clustering. We then present several astrophysical
applications of the halo model: these include models of the spatial
distribution of galaxies, the nonlinear velocity, momentum and pressure fields,
descriptions of weak gravitational lensing, and estimates of secondary
contributions to temperature fluctuations in the cosmic microwave background.


title: The Fate of Intracluster Radio Plasma

abstract:
  Radio plasma injected by active radio galaxies into clusters of galaxies
quickly becomes invisible due to radiative losses of the relativistic
electrons. In this talk, the fate of radio plasma and its role for the galaxy
cluster is discussed: buoyancy removes it from the central regions and allows
to transfer its energy into the ambient gas. The remaining low energy electron
populations are still able to emit a low luminosity glow of observable
radiation via synchrotron-self Comptonized emission. Shock waves in the ambient
gas can re-ignite the radio emission.


title:
The Fornax Cluster Spectroscopic Survey: A Sample of Confirmed Cluster
  Dwarfs

abstract:
  The Fornax Cluster Spectroscopic Survey (FCSS) project utilises the 2dF
multi-object spectrograph on the AAT. Its aim is to obtain spectra for a
complete sample of all 14000 objects with 16.5<bj<19.7 irrespective of their
morphology in a 12 sq deg area centred on the Fornax Cluster. A sample of 24
Fornax Cluster members has been identified from the first 2dF field (3.1 sq deg
in area) to be completed. This is the first complete smaple of cluster objects
of known distance with well defined selection limits. 19 of the galaxies (with
-15.8<M_B<-12.7) appear to be conventional dwarf elliptical or dwarf S0
galaxies. The other 5 objects (with -13.6<M_B<-11.3) are those galaxies which
we described in Drinkwater et al (2002b) and labelled `Ultra-Compact Dwarfs'
(UCDs). A major result is that the conventional dwarfs all have scale-sizes>3
arcsec (abut 300 pc). This apparent minimum scale size implies an equivalent
minimum luminosity for a dwarf of a given surface brightness. This produces a
limit on their distribution in the magnitude-surface brightness plane, such
that we do not observe dEs with high surface brightnesses but faint absolute
magnitudes. Above this observed minimum scale-size of 3 arcsec, the dEs and
dS0s fill the whole area of the magnitude-surface brightness plane sampled by
our selection limits. The observed correlation between magnitude and surface
brightness noted by several recent studies of brighter galaxies is not seen
with our fainter cluster sample. A comparison of our results with the Fornax
Cluster Catalog (FCC) of Ferguson illustrates that attempts to determine
cluster membership solely on the basis of observed morphology can produce
significant errors.


title: The swallowing of a quark star by a black hole

abstract:
  In 3-d SPH simulations of the coalescence of a quark star with a
pseudo-Newtonian black hole all of the quark matter is quickly accreted by the
black hole. The Madsen-Caldwell-Friedman argument against the existence of
quark stars may need to be re-examined.


title: Selection of the SIM Astrometric Grid

abstract:
  We investigate the choice of stellar population for use as the Astrometric
Grid for the Space Interferometry Mission (SIM). SIM depends on the astrometric
stability of about 2000 stars, the so called Grid, against which the science
measures are referenced. Low metallicity, and thus relatively high luminosity K
giants are shown to be the population of choice, when available. The
alternative, nearby G dwarfs, are shown to be suseptable to unmodeled motions
induced by gas-giant planetary companions, should there be a significant
population of such companions.
  Radial velocity filtering is quite efficient in selecting Grid members from
the K giants with yields exceeding 50% if filtering at 30m/s (1-sigma) is
available. However if the binary fraction of the G dwarfs approaches 100% as
some studies suggest, the yield of stable systems would be in the range of 15%
at best (with 10m/s filtering). Use of the initial SIM measurement as a final
filter is shown not to be critical in either case, although it could improve
the yield of stable grid members.
  For a Grid composed of weak-lined K giants, the residual contamination by
large unmodeled motions will amount to about 3% (and rises to about 6% if a
60m/s radial velocity criterion is used). The selective introduction of
quadratic terms in the proper motion solutions during the post-mission phase of
data reduction can reduce contamination to a remarkable 1% or better in either
case.
  Analytic estimates based on circular orbits are developed which show how
these results come about.


title: A High-Energy Study of the Geminga Pulsar

abstract:
  We present the results of deep X-ray and gamma-ray observations of the
Geminga pulsar obtained in the final years of the ASCA and CGRO missions, and
an upper limit from RXTE. A phase-connected ephemeris from the gamma-rays is
derived that spans the years 1973-2000, after allowing for a minor glitch in
frequency of Delta f/f = 6.2 x 10^-10 in late 1996. ASCA observations of the
hard X-ray pulse profile in 1994 and 1999 confirm this glitch. An improved
characterization of the hard X-ray pulse profile and spectrum from the long
ASCA observation of 1999 confirms that there is a non-thermal X-ray component
that is distinct from the gamma-ray spectrum as measured by EGRET. It can be
parameterized as a power-law of photon index Gamma = 1.72 +/- 0.10 with a flux
of 2.62 x 10^-13 ergs/cm^2/s in the 0.7-5 keV band and pulsed fraction 0.54 +/-
0.05, similar to, but more precise than values measured previously. An
extrapolation of this spectrum into the energy band observed by the RXTE PCA is
consistent with the non-detection of pulsed emission from Geminga with that
instrument. These results are interpreted in the context of outer-gap models,
and motivations for future X-ray observations of Geminga are given.


title:
Constraining the Heliosphere: The Need for High-Resolution Observations
  of Nearby Interstellar Matter

abstract:
  High-resolution ultraviolet observations of nearby bright and faint stars are
required to evaluate changes in the past and future galactic environments of
the Sun, and the possibly impact of these changes on the interplanetary
environment at 1 AU (around the Earth). The boundary conditions of the
heliosphere and interplanetary environments are constrained by the
characteristics of the surrounding interstellar material (ISM), which changes
on timescales of 10^3-10^5 years. An increase in the density of the
interstellar cloud surrounding the solar system to 10 cm^-3 decreases the
heliosphere radius by about an order of magnitude. UV observations of nearby
stars at high spectral resolution (>300,000) and high signal-to-noise are
required to evaluate future modifications to heliosphere properties by the ISM.


title:
RXTE Observations of 3C273 between 1996 and 2000:Variability Timescale
  and Jet Power

abstract:
  We present the results of a long-look monitoring of 3C273 with RXTE between
1996 and 2000. A total of 230 observations amounts to a net exposure of
845ksec, with this spectral and variability analysis of 3C273 covering the
longest observation period available at hard X-ray energies. Flux variations by
a factor of 4 have been detected over 4years, whereas less than 30% flux
variations have been observed for individual flares on time-scales of 3 days.
Two temporal methods, the power spectrum density (PSD) and the structure
function (SF), have been used to study the variability characteristics of
3C273. The hard X-ray photon spectra generally show a power-law shape with a
differential photon index of G = 1.6+-0.1. In 10 of 261 data segments,
exceptions to power-law behaviour have been found: (i) an additional soft
excess below 4keV, and (ii) a broad Fe fluorescent line feature with EW =
100-200 eV. Our new observations of these previously reported X-ray features
may imply that 3C273 is a unique object whose hard X-ray emission occasionally
contains a component which is not related to a beamed emission (Seyfert like),
but most hard X-rays are likely to originate in inverse Compton radiation from
the relativistic jet (blazar like). Multi-frequency spectra from radio to
gamma-ray are presented in addition to our RXTE results. The X-ray time
variability and spectral evolution are discussed in the framework of beamed,
synchrotron self-Compton picture. We consider the ``power balance'' (both
radiative and kinetic) between the accretion disk, sub-pc-scale jet, and the
10kpc-scale jet.


title: XMM-Newton observations of MR Vel/RX J0925.7-4758

abstract:
  We report on XMM-Newton observations of the galactic supersoft X-ray source
RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from
iron and oxygen. XMM-Newton data confirm the finding of previous Chandra
HETGS/MEG observations that NLTE models of hot white dwarf atmospheres fail to
represent the complex spectrum. There are clear evidences for P Cygni profiles
with wind velocities of up to 2000 km/s. Small flux variations with time scales
larger than 1000s are present. The strongest power is at ~ 0.21d, a period
close to that seen in V band optical light curves. A detailed analysis of the
associated changes in the RGS and EPIC pn spectra hint at a mostly grey
mechanism suggesting a variation of the visibility of the white dwarf due to
occulting material in the accretion disk. Finally, we detect radial velocity
changes of 173 +/- 47 km/s between two RGS observations obtained half an
orbital cycle apart. The amplitude of the RGS velocity shift is consistent with
that of the optical He II 4686 and thus supports the idea that most of the He
II optical line emission arises from the accretion disk.


title:
Discovery of an ionized Fe-K edge in the z=3.91 Broad Absorption Line
  Quasar APM 08279+5255 with XMM-Newton

abstract:
  Recent XMM-Newton observations of the high-redshift, lensed, broad absorption
line (BAL) quasi-stellar object APM 08279+5255, one of the most luminous
objects in the universe, allowed the detection of a high column density
absorber ($N_H \approx 10^{23}$ cm$^{-2}$) in the form of a K-shell absorption
edge of significantly ionized iron (Fe XV - XVIII) and corresponding ionized
lower-energy absorption. Our findings confirm a basic prediction of
phenomenological geometry models for the BAL outflow and can constrain the size
of the absorbing region. The Fe/O abundance of the absorbing material is
significantly higher than solar (Fe/O = 2-5), giving interesting constraints on
the gas enrichment history in the early Universe.


title:
The Microlensing Event MACHO-99-BLG-22/OGLE-1999-BUL-32: An Intermediate
  Mass Black Hole, or a Lens in the Bulge

abstract:
  We present an re-analysis of the longest timescale gravitational microlensing
event discovered to date: MACHO-99-BLG-22/OGLE-1999-BUL-32, which was
discovered by both the MACHO and OGLE microlensing alert systems. Our analysis
of this microlensing parallax event includes a likelihood analysis of the lens
position based upon a standard model of the Galactic velocity distribution, and
this implies that the lens could be a black hole of ~100 M_solar at a distance
of a few hundred parsecs in the Galactic disk or a massive stellar remnant
(black hole or neutron star) in the Galactic bulge. Our new analysis includes
data from the MACHO, GMAN, and MPS collaborations in addition to the OGLE data
used in a previous analysis by Mao et al (2002). The crucial feature that
distinguishes our analysis from that of Mao et al is an accurate constraint on
the direction of lens motion and an analysis of the implications of this
direction.


title:
Identification of a 12-17 day timescale in X-ray observations of GRS
  1915+105

abstract:
  Measurement of the energy emitted from accreting astrophysical systems
provides an observational constraint on the plasma processes that may be
operating within the disk. Here we examine the continual time variation over
the past six years of the total X-ray flux from the microquasar GRS 1915+105.
The application of differencing and rescaling techniques to RXTE/ASM data shows
that the small amplitude fluctuations scale up to 12-17 days. A 17-day
timescale in the X-ray fluctuations corresponds to half the measured binary
orbital period of this system (33.5 +/- 1.5 days). While this may be
coincidental, it is possible that these two timescales may be linked by, for
example, a turbulent cascade in the accretion disk driven by a tidally-induced
two-armed spiral shock corotating with the binary system. Temporal scaling is
found only in the ever-present small fluctuations, and not in the intermittent
larger-amplitude fluctuations. This is consistent with the basic model for this
source which consists of a steady, cold outer disk and an unstable inner disk.


title:
On the intensity contrast of solar photospheric faculae and network
  elements

abstract:
  Sunspots, faculae and the magnetic network contribute to solar irradiance
variations. The contribution due to faculae and the network is of basic
importance, but suffers from considerable uncertainty. We determine the
contrasts of active region faculae and the network, both as a function of
heliocentric angle and magnetogram signal. To achieve this, we analyze
near-simultaneous full disk images of photospheric continuum intensity and
line-of-sight magnetic field provided by the Michelson Doppler Interferometer
(MDI) on board the SOHO spacecraft. Starting from the surface distribution of
the solar magnetic field we first construct a mask, which is then used to
determine the brightness of magnetic features, and the relatively field-free
part of the photosphere separately. By sorting the magnetogram signal into
different bins we are able to distinguish between the contrasts of different
concentrations of magnetic field. We find that the contrasts of active region
faculae (large magnetogram signal) and the network (small signal) exhibit a
very different CLV, showing that the populations of magnetic flux tubes are
different. This implies that these elements need to be treated separately when
reconstructing variations of the total solar irradiance with high precision. We
have obtained an analytical expression for the contrast of photospheric
magnetic features as a function of both position on the disk and magnetic field
strength, by performing a 2-dimensional fit to the observations.


title:
Time-Dependent Optical Spectroscopy of GRB 010222: Clues to the GRB
  Environment

abstract:
  We present sequential optical spectra of the afterglow of GRB 010222 obtained
one day apart using the Low Resolution Imaging Spectrometer (LRIS) and the
Echellette Spectrograph and Imager (ESI) on the Keck telescopes. Three
low-ionization absorption systems are spectroscopically identified at
z1=1.47688, z2=1.15628, and z3=0.92747. The higher resolution ESI spectrum
reveals two distinct components in the highest redshift system at z1a=1.47590
and z1b=1.47688. We interpret the z1b=1.47688 system as an absorption feature
of the disk of the host galaxy of GRB 010222. The best fitted power-law optical
continuum and [Zn/Cr] ratio imply low dust content or a local gray dust
component near the burst site. In addition, we do not detect strong signatures
of vibrationally excited states of H_2. If the GRB took place in a superbubble
or young stellar cluster, there are no outstanding signatures of an ionized
absorber, either. Analysis of the spectral time dependence at low resolution
shows no significant evidence for absorption-line variability. This lack of
variability is confronted with time-dependent photoionization simulations
designed to apply the observed flux from GRB 010222 to a variety of assumed
atomic gas densities and cloud radii. The absence of time dependence in the
absorption lines implies that high-density environments are disfavored. In
particular, if the GRB environment was dust free, its density was unlikely to
exceed nH=10^2 cm^-3. If depletion of metals onto dust is similar to Galactic
values or less than solar abundances are present, then nH > 2 x 10^4 cm^-3 is
probably ruled out in the immediate vicinity of the burst.


title:
Near-IR 2D-Spectroscopy of the 4''x 4'' region around the Active
  Galactic Nucleus of NGC1068 with ISAAC/VLT

abstract:
  We present new near-IR long slit spectroscopic data obtained with ISAAC on
VLT/ANTU (ESO/Paranal) of the central 4''x 4'' region surrounding the central
engine of NGC1068 . Bracket Gamma (Bg) and H2 emission line maps and line
profile grids are produced, at a spatial resolution~0.5" and spectral
resolution 35km/s. Two conspicuous knots of H2 emission are detected at about
1'' on each side of the central engine along PA=90deg, with a projected
velocity difference of 140km/s: this velocity jump has been interpreted in
Alloin et al (2001) as the signature of a rotating disk of molecular material.
Another knot with both H2 and Bg emission is detected to the North of the
central engine, close to the radio source C where the small scale radio jet is
redirected and close to the brightest [OIII] cloud NLR-B. At the achieved
spectral resolution, the H2 emission line profiles appear highly asymmetric
with their low velocity wing being systematically more extended than their high
velocity wing. A simple way to account for the changes of the H2 line profiles
(peak-shift with respect to the systemic velocity, width, asymmetry) over the
entire 4''x 4'' region, is to consider that a radial outflow is superimposed
over the emission of the rotating molecular disk. We present a model of such a
kinematical configuration and compare our predicted H2 emission profiles to the
observed ones.


title:
Extended Thermal X-ray Emission from the Spiral-Dominant Group of
  Galaxies HCG 57

abstract:
  We observed a group of galaxies, HCG 57, with ASCA. Regardless that their
member galaxies are dominated by spiral galaxies, we detected extended thermal
X-ray emission that is attributed to hot gas with a temperature of
$1.04\pm0.10$ keV. This is the second clear detection of thermal X-ray emission
from a spiral-dominant group of galaxies after HCG 92. The luminosity of the
thermal emission is about $5\times10^{41}$ erg s$^{-1}$ in the 0.5--10 keV
band, which is higher than that of HCG 92, but relatively less luminous among
groups of galaxies. The X-ray emission is extended over several member
galaxies, and is thus associated with the group rather than an individual
galaxy. The metal abundance cannot be well constrained with a lower limit of
0.08 solar. The gas-to-stellar mass ratio is $\sim0.3$. Although this is
relatively low among groups, the hot gas is also a significant component even
in the spiral-dominant group. We suggest that the X-ray faintness of
spiral-dominant groups is due to the low surface brightness and somewhat low
gas mass, at least in the case of HCG 57.


title:
Using VLBI Data to Investigate the Galaxy Structure in the
  Gravitationally Lensed System B1422+231

abstract:
  Gravitationally lensed systems with multiply imaged quasars are an excellent
tool for studying the properties of distant galaxies. In particular, they
provide the most accurate mass measures for the lensing galaxy. The system
B1422+231 is a well studied example of a quadruply imaged quasar, with
high-quality VLBI data available. Very accurate data on image positions, fluxes
and deconvolved image sizes provide good constraints for lensing models. We
discuss here the failure of smooth models in fitting the data. Since it is
intuitively clear that the mass of a lens galaxy is not a smooth entity, we
have investigated how deviation from a smooth model can influence lensing
phenomena, especially the image flux ratios. To explore expectations about the
level of substructure in galaxies and its influence on strong lensing, N-body
simulations of a model galaxy are employed. By using the mass distribution of
this model galaxy as a lens, synthetic data sets of different four image system
configurations are generated. Their analysis can possibly provide evidence for
the presence and strong influence of substructure in the primary lens galaxy.


title: Fine tuning of parameters of the universe

abstract:
  The mechanism of production of a large number of universes is considered. It
is shown that universes with parameters suitable for creation of life are
necessarily produced as a result of quantum fluctuations. Fractal structures
are formed provided fluctuations take place near a maximum of the potential.
Several ways of formation of similar fractal structures within our universe are
discussed. Theoretical predictions are compared with observational data.


title:
Self-Gravitating Magnetically-Supported Protostellar Disks and the
  Formation of Substellar Companions

abstract:
  Isolated low-mass stars are formed, in the standard picture, from the
collapse of dense cores condensed out of strongly magnetized molecular clouds.
The dynamically collapsing inflow traps nearly half of the critical magnetic
flux needed for the core support and deposits it in a small region surrounding
the protostar. It has been argued previously that the deposited flux can slow
down the inflow, allowing matter to pile up and settle along field lines into a
magnetically supported, circumstellar disk. Here we show that the disk
typically contains $\sim 10%$ of the stellar mass, and that it could become
self-gravitating under plausible conditions during the rapidly accreting,
``Class 0'' phase of star formation. Subsequent fragmentation of the
self-gravitating, magnetically subcritical disk, driven by magnetic diffusion,
could produce fragments of substellar masses, which collapse to form brown
dwarfs and possibly massive planets. This scenario predicts substellar object
formation at distances of order 100 AU from the central star, although orbital
evolution is possible after formation. It may provide an explanation for the
small, but growing, number of brown dwarf companions found around nearby stars
by direct imaging. The relatively large formation distances make the substellar
companions vulnerable to dynamic ejection, particularly in binary (multiple)
systems and dense clusters. Those ejected may account for, at least in part,
the isolated brown dwarfs and perhaps free-floating planetary mass objects.


title: On the X-ray lines in the afterglows of GRBs

abstract:
  The observation of X-ray lines in the afterglow of GRB 011211 has been
reported, and challenged. The lines were interpreted as blue-shifted X-rays
characteristic of a set of photoionized ``metals'', located in a section of a
supernova shell illuminated by a GRB emitted a couple of days after the
supernova explosion. We show that the most prominent reported lines coincide
with the ones predicted in the ``cannonball'' model of GRBs. In this model, the
putative signatures are Hydrogen lines, boosted by the (highly relativistic)
motion of the cannonballs (CBs). The corresponding Doppler boost can be
extracted from the fit to the observed I-, R- and V-band light-curves of the
optical afterglow of GRB 011211, so that, since the redshift is also known, the
line energies are --in the CB model-- predicted. We also discuss other GRBs of
known redshift which show spectral features generally interpreted as Fe lines,
or Fe recombination edges. The ensemble of results is very encouraging from the
CB-model's point of view, but the data on each individual GRB are not good
enough to draw (any) objectively decisive conclusions. We outline a strategy
for X-ray observers to search for lines which, in the CB model, move
predictably from higher to lower energies.


title:
Pulsar bow-shock nebulae. III. Inclusion of a neutral component, and
  H_{a lpha} luminosity

abstract:
  The interaction of the wind from a pulsar (or more generally from a star)
with t he amb ient medium gives rise to the formation of a bow-shock nebula. We
present a mode l of adiabatic bow-shock nebulae, including the presence of a
neutral component in the interstellar medium. As demonstrated in a previous
paper (Bucciantini & Bandiera 2001}, hereafter Paper I), the velocity and the
luminosity of the pulsar, as well a s the characteristics of the interstellar
medium (ISM), play an essential role in determinin g the properties of bow
shock nebulae. In particular, the Balmer emission is strongly affect ed by the
rates of hydrogen charge-exchange and collisional excitation. So far, only
one-com ponent models have been proposed, treating the neutrals as a small
perturbation. The distrib ution of neutral hydrogen in the nebula, derived by
our model, is then used to determine how the h_{alpha} luminosity varies along
the bow shock. We find that the luminosity trend is d ifferent for
charge-exchange and collisional excitation, and that processes like diffusion o
r ionization may reduce the emission in the head of the nebula.


title: BeppoSAX ToO Observations on BLAZARS

abstract:
  We summarize the results of BeppoSAX ToO observation of blazars that were
known to be in a high state from observations carried out in the optical or
X-ray or TeV bands.In some of the observed sources, two spectral components
were detected, which are interpreted as synchrotron and inverse Compton
emission, respectively. Fast variability was detected in three sources (ON 231,
BL Lac and S5 0716+714), but always only for the synchrotron component. Most of
the triggers are from optical observations, consequently most of the observed
sources are LBL or intermediate objects. They were in a high state in the X-ray
band, but not in an exceptionally high state. No strong shifts in the
synchrotron peak frequency are reported. This is in line with the findings that
the synchrotron peak frequency is more variable for HBL objects, i.e. sources
that have this peak at higher energies.


title: Radio Continuum Observations towards Optical and Molecular Outflows

abstract:
  We present multi-frequency VLA continuum observations towards 8 star forming
regions with molecular and optical outflows: L1489, HH 68-69, HH 94-95, NGC
2264D, L1681B, L778, MWC 1080 and V645 Cyg. We detect three thermal radio jets,
L1489, YLW 16A in L1681B and NGC 2264D VLA 7, associated with molecular and/or
HH outflows. The L1489 and NGC 2264D VLA 7 thermal radio jets appear elongated
in the direction of the larger scale outflow. We report the first tentative
detection of a non-thermal radio jet, L778 VLA 5, associated with a low mass
Class I protostar and powering a molecular outflow. For HH68-69, HH 94-95 and
the molecular outflow in NGC 2264D we could not identify a candidate of the
exciting source of these outflows. The radio emission associated with V645 Cyg
is quite extended, ~0.1 pc, and time variable. We detect three radio sources in
the MWC 1080 that could be associated with YSOs.


title:
Constraining Galaxy Formation and Cosmology with the Conditional
  Luminosity Function of Galaxies

abstract:
  We use the conditional luminosity function (CLF), which gives the number of
galaxies with luminosities in the range [L, L+dL] that reside in a halo of mass
M, to link the distribution of galaxies to that of dark matter haloes. We seek
the CLF that reproduces the galaxy luminosity function and the luminosity
dependence of the galaxy clustering strength and test the models by comparing
the resulting mass-to-light ratios (M/L) with constraints from the Tully-Fisher
(TF) relation. We obtain a number of stringent constraints on both galaxy
formation and cosmology. In particular, this method can break the degeneracy
between Omega_0 and the power-spectrum normalization sigma_8, inherent in
current weak-lensing and cluster-abundance studies. For flat LCDM cosmogonies
with sigma_8 normalized by recent weak lensing observations, the best results
are obtained for Omega_0~0.3; Omega_0 < 0.2 leads to too large galaxy
correlation lengths, while Omega_0 > 0.4 gives too high M/L. The best-fit model
for the LCDM concordance cosmology (Omega_0=0.3) predicts M/L that are slightly
too high. We discuss a number of possible effects that might remedy this
problem, including small modification of cosmological parameters, warm in stead
of cold dark matter, systematic errors in current observational data, and the
existence of dark galaxies. Finally we use the CLF to predict several
statistics about the distribution of galaxy light in the local Universe.


title:
Rotation curves and metallicity gradients from HII regions in spiral
  galaxies

abstract:
  In this paper we study long slit spectra in the region of H$\alpha$ emission
line of a sample of 111 spiral galaxies with recognizable and well defined
spiral morphology and with a well determined environmental status, ranging from
isolation to non-disruptive interaction with satellites or companions. The form
and properties of the rotation curves are considered as a function of the
isolation degree, morphological type and luminosity. The line ratios are used
to estimate the metallicity of all the detected HII regions, thus producing a
composite metallicity profile for different types of spirals. We have found
that isolated galaxies tend to be of later types and lower luminosity than the
interacting galaxies. The outer parts of the rotation curves of isolated
galaxies tend to be flatter than in interacting galaxies, but they show similar
relations between global parameters. The scatter of the Tully-Fisher relation
defined by isolated galaxies is significantly lower than that of interacting
galaxies. The [NII]/H$\alpha$ ratios, used as metallicity indicator, show a
clear trend between Z and morphological type, t, with earlier spirals showing
larger ratios; this trend is tighter when instead of t the gradient of the
inner rotation curve, G, is used; no trend is found with the interaction
status. The Z-gradient of the disks depends on the type, being almost flat for
early spirals, and increasing for later types. The [NII]/H$\alpha$ ratios
measured for disk HII regions of interacting galaxies are higher than for
normal/isolated objects, even if all the galaxy families present similar
distributions of H$\alpha$ Equivalent Width.


title: Kinematics of parsec-scale structures in AGN: the 2cm VLBA Survey

abstract:
  We are investigating the kinematics of jets in active galactic nuclei on
parsec scales by studying a representative population of sources. This study is
being carried out using the Very Long Baseline Array at 15 GHz, with more than
800 images taken since 1994. In this contribution we present an overview of the
diversity of kinematics for a complete sample of sources.


title:
VLBI observations at 147 GHz: first detection of transatlantic fringes
  in bright AGN

abstract:
  At 147 GHz (2mm wavelength), we detected three prominent AGN (NRAO150, 3C279,
1633+382) with Very Long Baseline Interferometry (VLBI) with an angular
resolution of only 18 micro-arcseconds on the baseline between two antennas in
Arizona (10m HHT and 12m KittPeak) and the IRAM 30m antenna on Pico Veleta in
Spain. This is a new world record in radio interferometry and astronomical
imaging and opens fascinating future possibilities to directly image and study
the innermost regions in Quasars and other Active Galactic Nuclei.


title:
New detections of Mn, Ti and Mg in damped Ly-alpha systems: Toward
  reconciling the dust/nucleosynthesis degeneracy

abstract:
  We have combined new high resolution UVES-VLT observations of a sample of
four damped Ly-alpha systems (DLAs) at redshifts between z_abs = 1.7-2.5 with
the existing HIRES-Keck spectra to undertake a comprehensive study of their
physical conditions and their abundances of up to 15 elements. In this paper,
we present abundance measurements for Mn, Ti and Mg which are among the first
presented in the literature at these redshifts. We confirm the underabundance
of Mn with respect to Fe as observed in lower redshift DLAs and a trend with
decreasing metallicity very similar to the one observed in Galactic metal-poor
stars. This agreement between the Mn/Fe ratios in DLAs and in Galactic stars
suggests that the DLAs and the Milky Way share some similarities in their star
formation histories. However, these similarities must be cautiously interpreted
and investigated in light of all of the elements observed in the DLAs. We have
obtained a first measurement and a significant upper limit of the Ti abundance
at z_abs ~ 2 from the TiII lines at lambda_rest > 3000 A, and we discuss how
the relative abundance of this highly depleted element can be used to prove
unambiguously any enhancement of the abundance of the alpha-elements relative
to Fe-peak elements. We present the abundances of Mg for two DLAs in addition
to the single Mg measurement existing in the literature. Contrary to the trend
expected from differential depletion, the [Mg/Si,S] ratios tend to be
over-solar. The effect is at the level of the measurement errors, but worth
investigating in a larger sample because it could be suggestive of a peculiar
nucleosynthesis effect.


title: Viscous dissipative effects in white dwarfs and neutron stars

abstract:
  When a differentially rotating magnetic star undergoes ``turn-over'', i.e.,
its magnetic symmetry axis is inclining at a gradually increasing angle with
respect to its invariant angular momentum axis up to the perpendicular position
(situation known as ``perpendicular rotator''), the poloidal magnetic field
causes interchange of angular momentum via hydromagnetic Alfven waves
propagating along the poloidal magnetic field lines and, accordingly, the
resulting perpendicular rotator obtains uniform rotation. This dissipative
mechanism is represented by the so-called ``turn-over viscosity''. For several
white dwarf and neutron star models, we compute the energy dissipation due to
the turn-over viscosity; we also compare this effect with the corresponding
dissipative effects induced by the electron, ion, and turbulent viscosity.


title:
The Point-Agape survey: 4 high signal-to-noise ratio microlensing
  candidates detected towards M31

abstract:
  We have carried out a survey of the Andromeda galaxy for unresolved
microlensing (pixel lensing). We present a subset of four short timescale, high
signal-to-noise microlensing candidates found by imposing severe selection
criteria: the source flux variation exceeds the flux of an R=21 magnitude star
and the full width at half maximum timescale is less than 25 days. Remarkably,
in three out of four cases, we have been able to measure or strongly constrain
the Einstein crossing time of the event. One event, which lies projected on the
M31 bulge, is almost certainly due to a stellar lens in the bulge of M31. The
other three candidates can be explained either by stars in M31 and M32 or by
MACHOs.


title: Spectroscopic observations of the candidate sgB[e]/X-ray binary CI Cam

abstract:
  We present a compilation of spectroscopic observations of the sgB[e] star CI
Cam. This includes data from before, during, and after its 1998 outburst. The
object shows a rich emission line spectrum originating from circumstellar
material, rendering it difficult to determine the nature of either star
involved or the cause of the outburst. We collate pre-outburst data to
determine the state of the system before this occurred and provide a baseline
for comparison with later data. During the outburst all lines become stronger,
and hydrogen and helium lines become significantly broader and asymmetric.
After the outburst, spectral changes persist for at least three years, with
FeII and [NII] lines still a factor of ~2 above the pre-outburst level and HeI,
HeII, and NII lines suppressed by a factor of 2-10. We find that the spectral
properties of CI Cam are similar to other sgB[e] stars and therefore suggest
that the geometry of the circumstellar material is similar to that proposed for
the other objects: a two component outflow, with a fast, hot, rarefied polar
wind indistinguishable from that of a normal supergiant and a dense, cooler
equatorial outflow with a much lower velocity. We suggest that CI Cam is among
the hotter members of the class and is viewed nearly pole-on. The nature of the
compact object and the mechanism for the outburst remain uncertain, although it
is likely that the compact object is a black hole or neutron star, and that the
outburst was precipitated by its passage through the equatorial material. We
suggest that this prompted a burst of supercritical accretion resulting in
ejection of much of the material, which was later seen as an expanding radio
remnant. [Abbreviated]


title: How is really decelerating the expansion of SN1993J?

abstract:
  SN1993J is to date the radio supernova whose evolution has been monitored in
greatest detail and the one which holds best promise for a comprehensive
theoretical-observational analysis. The shell-like radio structure of SN1993J
has expanded in general accord with models of shock excited emission, showing
almost circular symmetry for over 8 years, except for a bright feature at the
south-eastern region of the shell that has been observed at every epoch. The
spectrum of SN1993J has flattened from alpha =-1 to alpha =-0.67 (S_(\nu)
propto nu**(alpha)). The decelerated expansion can be modeled well with a
single slope but apparently better with two slopes. There are also intriguing
hints of structure in the expansion curve. The results by the two VLBI groups
carrying out this research show general agreement, but also some differences. A
comparison of the optical and VLBI results about the details of the
deceleration show some discrepancies.


title: Investigation of magnetic loop structures in the corona of UX Arietis

abstract:
  Most of the emission coming from the solar corona is confined into closed
magnetic structures in the form of arcs (loops). Very little is known about the
structure of stellar coronae. The magnetic topology, however, can be inferred
by studying the radio emission coming from electrons trapped in the magnetic
loops. Evident morphological changes are produced in fact by stellar rotation.
We have performed 4 VLBA+Effelsberg runs distributed in time so as to cover
well the rotational period of 6.44 days of the active star UX Arietis. We
present here some preliminary results, from those observations.


title: Universality of power law correlations in gravitational clustering

abstract:
  We present an analysis of different sets of gravitational N-body simulations,
all describing the dynamics of discrete particles with a small initial velocity
dispersion. They encompass very different initial particle configurations,
different numerical algorithms for the computation of the force, with or
without the space expansion of cosmological models. Despite these differences
we find in all cases that the non-linear clustering which results is
essentially the same, with a well-defined simple power-law behaviour in the
two-point correlations in the range from a few times the lower cut-off in the
gravitational force to the scale at which fluctuations are of order one. We
argue, presenting quantitative evidence, that this apparently universal
behaviour can be understood by the domination of the small scale contribution
to the gravitational force, coming initially from nearest neighbor particles.


title:
Time-resolved ultraviolet spectroscopy of the compact interacting binary
  QU Car

abstract:
  We present HST/STIS (1160--1700A) echelle spectra of the cataclysmic variable
(CV) star, QU Car, observed in time-tag mode at three epochs. In catalogues
this binary is classified as a nova-like variable. We find evidence of a
high-state non-magnetic CV at low inclination, with unusually high ionisation.
We observed narrow absorption lines (few hundred km/s wide) in N V1240, O V1371
and Si IV1398, as well as broader (HWZI ~1000km/s) emission in C III1176, C
IV1549 and He II1640, all with a superposed absorption component. High
ionisation is indicated by the unusually string He II emission and the relative
strength of the O V absorption line. The dereddened UV SED of, on average, -2.3
suggests that disc accretion dominates the spectral energy distribution. In two
observations velocity shifting is noted in the absorption lines on a timescale
long enough not to repeat within the ~2600-sec exposures. The absorption
superposed on the C IV emission line moves coherently with the N V and Si IV
absorption, suggesting the same origin for all absorption lines -- most likely
to be in the accretion disc atmosphere. Weak blueshifted absorption in NV and
C\IV provides evidence of an outflow component and we estimate a maximum
outflow velocity of ~2000km/s. This may be linked to a wind launched from
further out in the disc than is typically seen in those high-state non-magnetic
CV whose wind speeds are observed to reach to >4000km/s. Unusually, three
ionisation stages of carbon -- C II, C III and C IV -- are present in emission,
with line width increasing with higher ionisation. The presence of C II in
emission and the positive line-width/ionisation correlation is most easily
reconciled with an origin in a disc chromosphere, beyond the influence of the
EUV-emitting inner disc.


title: More nitrogen rich B-type stars in the SMC cluster, NGC 330

abstract:
  High resolution spectra of seven early B-type giant/supergiant stars in the
SMC cluster NGC330 are analysed to obtain their chemical compositions relative
to SMC field and Galactic B-type stars. It is found that all seven stars are
nitrogen rich with an abundance approximately 1.3 dex higher than an SMC
main-sequence field B-type star, AV304. They also display evidence for
deficiencies in carbon, but other metals have abundances typical of the SMC.
Given the number of B-type stars with low rotational projected velocities in
NGC330 (all our targets have vsini < 50 km/s), we suggest that it is unlikely
that the stars in our sample are seen almost pole-on, but rather that they are
intrinsically slow rotators. Furthermore, none of our objects displays any
evidence of significant Balmer emission excluding the possibility that these
are Be stars observed pole-on. Comparing these results with the predictions of
stellar evolution models including the effects of rotationally induced mixing,
we conclude that while the abundance patterns may indeed be reproduced by these
models, serious discrepancies exist. Most importantly, models including the
effects of initially large rotational velocities do not reproduce the observed
range of effective temperatures of our sample, nor the currently observed
rotational velocities. Binary models may be able to produce stars in the
observed temperature range but again may be incapable of producing suitable
analogues with low rotational velocities. We also discuss the clear need for
stellar evolution calculations employing the correct chemical mix of carbon,
nitrogen and oxygen for the SMC.


title: Strong and weak lensing by galaxy clusters

abstract:
  I present an overview of strong and weak gravitational lensing by galaxy
clusters. After briefly introducing the principles of gravitational lensing, I
discuss the main lessons learned from lensing on the mass distribution in
clusters and their relation to cosmology.