title:
Chemical abundances in quasar host galaxies and environments from narrow
  absorption line systems

abstract:
  We determined C, N and alpha-element relative abundances in the gas
surrounding six QSOs at an average redshift of < z > ~ 2.4, by studying six
narrow associated absorption systems in UVES high-resolution spectra. We found
five systems with a metallicity (measured by C/H) consistent or above the solar
value. The ionization structure observed in the associated systems is clearly
different from that of the intervening ones, indicating that the associated
systems are influenced by the strong UV flux from the QSO. There is a possible
correlation (anticorrelation) between [N/C] ([Si/C]) and [C/H] of the studied
associated systems, and [N/C] >= 0 when [C/H] >= 0. We have compared these
observational results with the predictions of a model simulating the joint
evolution of QSOs and their spheroidal hosts. The agreement turns out to be
very good, in particular, the case envisaging massive haloes and high
star-formation rates recovers both the correlation between [N/C] and [C/H] and
the anticorrelation for [Si/C] vs. [C/H]. Narrow associated absorption systems
prove to be powerful tracers of the chemical abundances in gas belonging to
high redshift spheroidal galaxies. The outflow of this same gas, triggered by
the QSO feedback, is probably going to contribute to the early enrichment of
the surrounding intergalactic medium. A larger statistics, possibly increasing
the number of ionisation stages, chemical elements and the redshift range,
would allow us to put firm constraints on detailed chemical evolution models of
galaxies at high redshifts.


title:
Semi-analytic Simulations of Galactic Winds: Volume Filling Factor,
  Ejection of Metals and Parameter Study

abstract:
  We present a semi-analytic treatment of galactic winds within high
resolution, large scale cosmological N-body simulations of a LCDM Universe. The
evolution of winds is investigated by following the expansion of supernova
driven superbubbles around the several hundred thousand galaxies that form in
an approximately spherical region of space with diameter 52 Mpc/h and mean
density close to the mean density of the Universe. We focus our attention on
the impact of winds on the diffuse intergalactic medium. Initial conditions for
mass loss at the base of winds are taken from Shu, Mo and Mao (2003). Results
are presented for the volume filling factor and the mass fraction of the IGM
affected by winds and their dependence on the model parameters is carefully
investigated. The mass loading efficiency of bubbles is a key factor to
determine the evolution of winds and their global impact on the IGM: the higher
the mass loading, the later the IGM is enriched with metals. Galaxies with 10^9
< M_* < 10^10 M_sun are responsible for most of the metals ejected into the IGM
at z=3, while galaxies with M_* < 10^9 M_sun give a non negligible contribution
only at higher redshifts, when larger galaxies have not yet assembled. We find
a higher mean IGM metallicity than Lyalpha forest observations suggest and we
argue that the discrepancy may be explained by the high temperatures of a large
fraction of the metals in winds, which may not leave detectable imprints in
absorption in the Lyalpha forest.


title: Dark Matter: Introduction

abstract:
  This short review was prepared as an introduction to the Royal Society's
'Dark Matter' conference. It addresses the embarrassing fact that 95% of the
universe is unaccounted for. Favoured dark matter candidates are axions or
weakly-interacting particles that have survived from the very early universe,
but more exotic options cannot be excluded. Experimental searches are being
made for the 'dark' particles but we have indirect clues to their nature too.
Comparisons of data (from, eg, gravitational lensing) with numerical
simulations of galaxy formation can constrain (eg) the particle velocities and
collision cross sections.
  The mean cosmic density of dark matter (plus baryons) is now pinned down to
be only about 30% of the critical density However, other recent evidence --
microwave background anisotropies, complemented by data on distant supernovae
-- reveals that our universe actually is 'flat', and that its dominant
ingredient (about 70% of the total mass-energy) is something quite unexpected
-- 'dark energy' pervading all space, with negative pressure. We now confront
two mysteries:
  (i) Why does the universe have three quite distinct basic ingredients --
baryons, dark matter and dark energy -- in the proportions (roughly) 5%, 25%
and 70%?
  (ii) What are the (almost certainly profound) implications of the 'dark
energy' for fundamental physics?


title:
Testing White Dwarf Crystallization Theory with Asteroseismology of the
  Massive Pulsating DA Star BPM 37093

abstract:
  It was predicted more than 40 years ago that the cores of the coolest white
dwarf stars should eventually crystallize. This effect is one of the largest
sources of uncertainty in white dwarf cooling models, which are now routinely
used to estimate the ages of stellar populations in both the Galactic disk and
the halo. We are attempting to minimize this source of uncertainty by
calibrating the models, using observations of pulsating white dwarfs. In a
typical mass white dwarf model, crystallization does not begin until the
surface temperature reaches 6000-8000 K. In more massive white dwarf models the
effect begins at higher surface temperatures, where pulsations are observed in
the ZZ Ceti (DAV) stars. We use the observed pulsation periods of BPM 37093,
the most massive DAV white dwarf presently known, to probe the interior and
determine the size of the crystallized core empirically. Our initial
exploration of the models strongly suggests the presence of a solid core
containing about 90% of the stellar mass, which is consistent with our
theoretical expectations.


title: Gravitational Redshifts in Simulated Galaxy Clusters

abstract:
  We predict the amplitude of the gravitational redshift of galaxies in galaxy
clusters using an N-body simulation of a Lambda CDM universe. We examine if it
might be possible to detect the gravitational effect on the total redshift
observed for galaxies. For clusters of mass M ~10^15 m_sun, the difference in
gravitational redshift between the brightest galaxy and the rest of the cluster
members is ~10 km/s. The most efficient way to detect gravitational redshifts
using information from galaxies only involves using the full gravitational
redshift profile of clusters. Massive clusters, while having the largest
gravitational redshift suffer from large galaxy peculiar velocities and
substructure, which act as a source of noise. This and their low number density
make it more reasonable to try averaging over many clusters and groups of
relatively low mass. We examine publicly available data for 107 rich clusters
from the ESO Nearby Abell Clusters Survey (ENACS), finding no evidence for
gravitational redshifts. Tests on our simulated clusters show that we need at
least ~2500 clusters/groups with M > 5*10^13 m_sun for a detection of
gravitational redshifts at the 2 sigma level.


title:
The metallicity-luminosity relation at medium redshift based on faint
  CADIS emission line galaxies

abstract:
  The emission line survey within the Calar Alto Deep Imaging Survey (CADIS)
detects galaxies with very low continuum brightness by using an imaging
Fabry-Perot interferometer. With spectroscopic follow-up observations of
MB>~-19 CADIS galaxies using FORS2 at the VLT and DOLORES at TNG we obtained
oxygen abundances of 5 galaxies at z~0.4 and 10 galaxies at z~0.64. Combining
these measurements with published oxygen abundances of galaxies with MB<~-19 we
find evidence that a metallicity-luminosity relation exists at medium redshift,
but it is displaced to lower abundances and higher luminosities compared to the
metallicity-luminosity relation in the local universe. Comparing the observed
metallicities and luminosities of galaxies at z<3 with Pegase2 chemical
evolution models we have found a favoured scenario in which the metallicity of
galaxies increases by a factor of ~2 between z~0.7 and today, and their
luminosity decreases by ~0.5-0.9mag.


title: NGC 1535: UV Observations and Models

abstract:
  We reinvestigate the UV spectrum of NGC1535 by means of recently developed
fully line-blanketed non-LTE models. These new models account for the wind in
spherical geometry while handling the atomic data in a very similar way to the
TLUSTY code. This approach ensures at the same time realistic predictions of
the photospheric absorption lines and of the emission lines formed in the wind.
Our analysis confirms the results of previous studies. We derive T_* = 70kK,
log M_dot = -7.8M_sun/year and v_infty = 2000km/s.


title:
Searching evidences for spiral shocks in the quiescent accretion disk of
  U Gem

abstract:
  We find that the quiescent accretion disk of U Gem has a complicated
structure. Along to the bright spot originating in the region of interaction
between the stream and the disk particles, there are also explicit indications
of spiral shocks. The Doppler map and the variations of the peak separation of
the emission lines are indicative.


title: A Theoretical Model for Mars Crater-Size Frequency Distribution

abstract:
  We present a theoretical and analytical curve with reproduce essential
features of the frequency distributions vs. diameter, of the 42,000 crater
contained in the Barlow Mars Catalog. The model is derived using reasonable
simple assumptions that allow us to relate the present craters population with
the craters population at each particular epoch. The model takes into
consideration the reduction of the number of craters as a function of time
caused by their erosion and obliteration, and this provides a simple and
natural explanation for the presence of different slopes in the empirical
log-log plot of number of craters (N) vs. diameter (D).


title: Sgr A* at low radio frequencies: GMRT observations

abstract:
  The central region of the Galaxy has been observed at 580, 620 and 1010 MHz
with the Giant Metrewave Radio Telescope (GMRT). We detect emission from
Sgr-A*, the compact object at the dynamical centre of the Galaxy, and estimate
its flux density at 620 MHz to be 0.5 +/- 0.1 Jy. This is the first detection
of Sgr A* below 1 GHz (Roy & Rao 2002, 2003), which along with a possible
detection at 330 MHz (Nord et al. 2004) provides its spectrum below 1 GHz.
Comparison of the 620 MHz map with maps made at other frequencies indicates
that most parts of the Sgr A West HII region have optical depth 2. However, Sgr
A*, which is seen in the same region in projection, shows a slightly inverted
spectral index between 1010 MHz and 620 MHz. This is consistent with its high
frequency spectral index, and indicates that Sgr A* is located in front of the
Sgr A West complex, and rules out any low frequency turnover around 1 GHz, as
suggested by Davies et al. (1976).


title: Monitoring and Discovering X-ray Pulsars in the Small Magellanic Cloud

abstract:
  Regular monitoring of the SMC with RXTE has revealed a huge number of X-ray
pulsars. Together with discoveries from other satellites at least 45 SMC
pulsars are now known. One of these sources, a pulsar with a period of
approximately 7.8 seconds, was first detected in early 2002 and since discovery
it has been found to be in outburst nine times. The outburst pattern clearly
shows a period of 45.1 +/- 0.4 d which is thought to be the orbital period of
this system. Candidate outburst periods have also been obtained for nine other
pulsars and continued monitoring will enable us to confirm these. This large
number of pulsars, all located at approximately the same distance, enables a
wealth of comparative studies. In addition, the large number of pulsars found
(which vastly exceeds the number expected simply by scaling the relative mass
of the SMC and the Galaxy) reveals the recent star formation history of the SMC
which has been influenced by encounters with both the LMC and the Galaxy.


title: Results of a search for new microquasars in the Galaxy

abstract:
  We present here the results of a search for new microquasars at low galactic
latitudes, based on a cross-identification between the ROSAT all sky Bright
Source Catalog (RBSC) and the NRAO VLA Sky Survey (NVSS) and follow-up
observations. The results obtained up to now suggest that persistent/silent
microquasars such as LS 5039 are rare objects in our Galaxy, and indicate that
future deeper surveys, and harder than the RBSC in X-rays, will play a
fundamental role in order to discover them.


title: Formation times and masses of dark matter haloes

abstract:
  The most commonly used definition of halo formation is the time when a halo's
most massive progenitor first contains at least half the final mass of its
parent. Reasonably accurate formulae for the distribution of formation times of
haloes of fixed mass have been available for some time. We use numerical
simulations of hierarchical gravitational clustering to test the accuracy of
formulae for the mass at formation. We also derive and test a formula for the
joint distribution of formation masses and times. The structure of a halo is
expected to be related to its accretion history. Our tests show that our
formulae for formation masses and times are reasonably accurate, so we expect
that they will aid future analytic studies of halo structure.


title:
How black holes get their kicks: Gravitational radiation recoil
  revisited

abstract:
  Gravitational waves from the coalescence of binary black holes carry away
linear momentum, causing center of mass recoil. This "radiation rocket" effect
has important implications for systems with escape speeds of order the recoil
velocity. We revisit this problem using black hole perturbation theory,
treating the binary as a test mass spiraling into a spinning hole. For extreme
mass ratios (q = m1/m2 << 1) we compute the recoil for the slow inspiral epoch
of binary coalescence very accurately; these results can be extrapolated to q ~
0.4 with modest accuracy. Although the recoil from the final plunge contributes
significantly to the final recoil, we are only able to make crude estimates of
its magnitude. We find that the recoil can easily reach ~ 100-200 km/s, but
most likely does not exceed ~ 500 km/s. Though much lower than previous
estimates, this recoil is large enough to have important astrophysical
consequences. These include the ejection of black holes from globular clusters,
dwarf galaxies, and high-redshift dark matter halos.


title: Consequences of gravitational radiation recoil

abstract:
  Coalescing binary black holes experience an impulsive kick due to anisotropic
emission of gravitational waves. We discuss the dynamical consequences of the
recoil accompanying massive black hole mergers. Recoil velocities are
sufficient to eject most coalescing black holes from dwarf galaxies and
globular clusters, which may explain the apparent absence of massive black
holes in these systems. Ejection from giant elliptical galaxies would be rare,
but coalescing black holes are displaced from the center and fall back on a
time scale of order the half-mass crossing time. Displacement of the black
holes transfers energy to the stars in the nucleus and can convert a steep
density cusp into a core. Radiation recoil calls into question models that grow
supermassive black holes from hierarchical mergers of stellar-mass precursors.


title: Gamma-Ray Burst Progenitors Confront Observations

abstract:
  The discovery of a supernova emerging at late times in the afterglow of GRB
030329 has apparently settled the issue on the nature of the progenitor of
gamma-ray bursts. We now know that at least a fraction of cosmological GRBs are
associated with the death of massive stars, and that the two explosions are
most likely simultaneous. Even though the association was already suggested for
GRB 980425, the peculiarity of that burst did not allow to extend the
association to all GRBs. The issue is now to understand whether GRB 030329 is a
"standard burst" or not. I will discuss some peculiarities of GRB 030329 and
its afterglow lightcurve showing how, rather than a classical cosmological GRB,
it looks more like a transition object linking weak events like GRB 980425 to
the classical long duration GRBs. I will also discuss the problems faced by the
Hypernova scenario to account for the X-ray features detected in several GRBs
and their afterglows.


title: What can we learn from Accretion Disc Eclipse Mapping experiments?

abstract:
  The accretion disc eclipse mapping method is an astrotomographic inversion
technique that makes use of the information contained in eclipse light curves
to probe the structure, the spectrum and the time evolution of accretion discs
in cataclysmic variables. This paper presents examples of eclipse mapping
results that have been key to improve our understanding of accretion physics.


title: Covariant Linear Perturbation Formalism

abstract:
  Lecture notes on covariant linear perturbation theory and its applications to
inflation, dark energy or matter and the cosmic microwave background.


title:
New Nonthermal Filaments at the Galactic Center: Are They Tracing a
  Globally Ordered Magnetic Field?

abstract:
  New high-resolution, wide-field 90 cm VLA observations of the Galactic Center
region by Nord et al. have revealed twenty nonthermal filament (NTF)
candidates. We report 6 cm polarization observations of six of these. All of
the candidates have the expected NTF morphology, and two show extended
polarization confirming their identification as NTFs. One of the new NTFs
appears to be part of a system of NTFs located in the Sgr B region, 64 pc in
projection north of Sgr A. These filaments cross the Galactic plane with an
orientation similar to the filaments in the Galactic Center Radio Arc. They
extend the scale over which the NTF phenomena is known to occur to almost 300
pc along the Galactic plane. Another NTF was found in the Galactic plane south
of the Sgr C filament but with an orientation of 45 degrees to the Galactic
plane. This is only the second of 12 confirmed NTFs that is not oriented
perpendicular to the Galactic plane. An additional candidate in the Sgr C
region was resolved into multiple filamentary structures. Polarization was
detected only at the brightness peak of one of the filaments. Several of these
filaments run parallel to the Galactic plane and can be considered additional
evidence for non-poloidal magnetic fields at the GC. Together the 90 and 6 cm
observations indicate that the Galactic center magnetic field may be more
complex than a simple globally ordered dipole field.


title: E+A Galaxies and the Formation of Early Type Galaxies at z~0

abstract:
  We present HST/WFPC2 observations of the five bluest E+A galaxies (z~0.1) in
the Zabludoff et al. sample to study whether their detailed morphologies are
consistent with late-to-early type evolution and to determine what drives that
evolution. The morphologies of four galaxies are disturbed, indicating that a
galaxy-galaxy merger is at least one mechanism that leads to the E+A phase.
Two-dimensional image fitting shows that the E+As are generally bulge-dominated
systems, even though at least two E+As may have underlying disks. In the
Fundamental Plane, E+As stand apart from the E/S0s mainly due to their high
effective surface brightness. Fading of the young stellar population and the
corresponding increase in their effective radii will cause these galaxies to
migrate toward the locus of E/S0s. E+As have profiles qualitatively like those
of normal power-law early-type galaxies, but have higher surface brightnesses.
This result provides the first direct evidence supporting the hypothesis that
power-law ellipticals form via gas-rich mergers. In total, at least four E+As
are morphologically consistent with early-type galaxies. We detect compact
sources, possibly young star clusters, associated with the galaxies. These
sources are much brighter (M_R ~ -13) than Galactic globular clusters, have
luminosities consistent with the brightest clusters in nearby starburst
galaxies, and have blue colors consistent with the ages estimated from the E+A
galaxy spectra (several 10^8 yr). Further study of such young star cluster
candidates might provide the elusive chronometer needed to break the
age/burst-strength degeneracy for these post-merger galaxies.


title: Cosmological perturbations and noncommutative tachyon inflation

abstract:
  The motivation for studying the rolling tachyon and non-commutative inflation
comes from string theory. In the tachyon inflation scenario, metric
perturbations are created by tachyon field fluctuations during inflation. We
drive the exact mode equation for scalar perturbation of the metric and
investigate the cosmological perturbations in the commutative and
non-commutative inflationary spacetime driven by the tachyon field which have a
Born-Infeld Lagrangian.


title: The Mid-IR Emission Structure of IRAS 16594-4656

abstract:
  We report TIMMI2 diffraction-limited mid-IR images of the multipolar PPN IRAS
16594-4656. By using the Lucy-Richardson deconvolution algorithm we recover a
two-peaked morphology in the innermost region at 8.6 and 11.5 microns. We
interpret the observed mid-IR structure as the detection of the two
limb-brightened peaks indicating the presence of a dusty toroidal structure in
IRAS 16594-4656. We find that the supposed biconical openings of the dust torus
are in good agreement with one of the bipolar outflows identified in the HST
optical images.


title: Observational Cosmology

abstract:
  I discuss the classical cosmological tests-- angular size-redshift,
flux-redshift, and galaxy number counts-- in the light of the cosmology
prescribed by the intepretation of CMB anisotropies. The discussion is somewhat
of a primer for physicists, with emphasis upon the possible systematic
uncertainties in the observations and their interpretation. Given the curious
composition of the Universe inherent in the emerging cosmological model, I
stress the value of searching for inconsistencies rather than concordance, and
suggest that the prevailing mood of triumphalism in cosmology is premature.


title: Evidence of a mis-aligned secondary bar in the Large Magellanic Cloud

abstract:
  Evidence of a mis-aligned secondary bar, within the primary bar of the Large
Magellanic Cloud (LMC) is presented. The density distribution and the
de-reddened mean magnitudes ($I_0$) of the red clump stars in the bar obtained
from the OGLE II data are used for this study. The bar region which
predominantly showed wavy pattern in the line of sight in \citet{a03} was
located. These points in the X-Z plane delineate an S-shaped pattern, clearly
indicating a mis-aligned bar. This feature is statistically significant and
does not depend on the considered value of $I_0$ for the LMC center. The rest
of the bar region were not found to show the warp or the wavy pattern. The
secondary bar is found to be considerably elongated in the Z-direction, with an
inclination of 66$^o$.5 $\pm$ 0$^o$.9, whereas the undisturbed part of the
primary bar is found to have an inclination of 15$^o$.1 $\pm$ 2$^o$.7, such
that the eastern sides are closer to us with respect to the western sides of
both the bars. The PA$_{maj}$ of the secondary bar is found to be 108$^o$.4
$\pm$ 7$^o$.3. The streaming motions found in the H I velocity map close to the
LMC center could be caused by the secondary bar. The recent star formation and
the gas distribution in LMC could be driven by the mis-aligned secondary bar.


title: CMB constraints on interacting cosmological models

abstract:
  Non-canonical scaling of the form $\rho_{x} \propto \rho_{m} a^{\xi}$, where
$\rho_{x}$ and $\rho_{m}$ are the energy densities of dark energy and dark
matter, respectively, provides a natural way to address the coincidence problem
-why the two densities are comparable today. This non-canonical scaling is
achieved by a suitable interaction between the dark components. We study the
observational constraints imposed on such models from the cosmic microwave
background (CMB) anisotropy spectrum. Using the recent WMAP results for the
location of the CMB peaks, we determine the admissible parameter space and find
that interacting models are well consistent with current observational bounds.


title: W Hya : molecular inventory by ISO-SWS

abstract:
  Infrared spectroscopy is a powerful tool to probe the inventory of solid
state and molecular species in circumstellar ejecta. Here we analyse the
infrared spectrum of the Asymptotic Giant Branch star W Hya, obtained by the
Short and Long Wavelength Spectrometers on board of the Infrared Satellite
Observatory. These spectra show evidence for the presence of amorphous
silicates, aluminum oxide, and magnesium-iron oxide grains. We have modelled
the spectral energy distribution using laboratory measured optical properties
of these compounds and derive a total dust mass loss rate of 3E-10 Msol/yr. We
find no satisfactory fit to the 13 micron dust emission feature and the
identification of its carrier is still an open issue. We have also modelled the
molecular absorption bands due to H2O, OH, CO, CO2, SiO, and SO2 and estimated
the excitation temperatures for different bands which range from 300 to 3000K.
It is clear that different molecules giving rise to these absorption bands
originate from different gas layers. We present and analyse high resolution
Fabry-Perot spectra of the three CO2 bands in the 15 micron region. In these
data, the bands are resolved into individual Q-lines in emission, which allows
the direct determination of the excitation temperature and column density of
the emitting gas. This reveals the presence of a warm (about 450K) extended
layer of CO2, somewhere between the photosphere and the dust formation zone.
The gas in this layer is cooler than the 1000K CO2 gas responsible for the
low-resolution absorption bands at 4.25 and 15 micron. The rotational and
vibrational excitation temperatures derived from the individual Q-branch lines
of CO2 are different (450K and 150K, respectively) so that the CO2 level
population is not in LTE.


title: $C^\infty$ perturbations of FRW models with a cosmological constant

abstract:
  Spatially homogeneous and isotropic cosmological models, with a perfect fluid
matter source and non-vanishing cosmological constant, are studied. The
equations governing linear perturbations of the space-time and the variation of
energy density are given. The complete solution of the problem is obtained for
$C^{\infty}$ perturbations, using a comoving time. The Sachs-Wolfe fluctuations
of the temperature of the cosmic background radiation are obtained for the
relatively growing density perturbations. It is found that the observable
celestial microwave fluctuation pattern underwent a reversal approximately two
billion years ago. What is observed today is a negative image of the last
scattering surface with an attenuation of the fluctuations, due to the presence
of the cosmological constant.


title: SS433:the microquasar link with ULXs?

abstract:
  SS433 is the prototype microquasar in the Galaxy and may even be analogous to
the ULX sources if the jets' kinetic energy is taken into account. However, in
spite of 20 years of study, our constraints on the nature of the binary system
are extremely limited as a result of the difficulty of locating spectral
features that can reveal the nature and motion of the mass donor. Newly
acquired, high resolution blue spectra taken when the (precessing) disc is
edge-on suggest that the binary is close to a common-envelope phase, and hence
providing kinematic constraints is extremely difficult. Nevertheless, we do
find evidence for a massive donor, as expected for the inferred very high mass
transfer rate, and we compare SS433's properties with those of Cyg X-3.


title: UV(IUE) spectra of hot post-AGB candidates

abstract:
  Analysis of the low resolution UV(IUE) spectra of 15 hot post-AGB candidates
is presented. The UV(IUE) spectra of 10 stars suggest partial obscuration of
the hot stars due to circumstellar dust. The reddened continua of these 10
stars were used to model and estimate the circumstellar extinction. The
circumstellar extinction law was found to be linear in $\lambda^{-1}$ in the
case of IRAS13266-5551 (CPD-55 5588), IRAS14331-6435 (Hen3-1013),
IRAS16206-5956 (SAO 243756), IRAS17074-1845 (Hen3-1347), IRAS17311-4924
(Hen3-1428), IRAS18023-3409 (LSS 4634), IRAS18062+2410 (SAO 85766),
IRAS18371-3159 (LSE 63), IRAS22023+5249 (LSIII +5224) and IRAS22495+5134 (LSIII
+5142). There seems to be no significant circumstellar extinction in the case
of IRAS17203-1534, IRAS17460-3114 (SAO 209306) and IRAS18379-1707 (LSS 5112).
The UV(IUE) spectrum of IRAS12584-4837 (Hen3-847) shows several emission lines
including that of HeII. It may be a massive young OB-supergiant or a low mass
star in the post-AGB phase of evolution. IRAS16206-5956 (SAO 243756) and IRAS
18062+2410 (SAO 85766) show variability in the UV which in addition to stellar
pulsations may be attributed to a dusty torus in motion around the hot central
stars. The UV spectrum of the bipolar PPN, IRAS17423-1755 (Hen3-1475) indicates
that the central B-type star is obscured by a dusty disk. The stars were placed
on the log g$-$log T$_{\rm eff}$ diagram showing the post-AGB evolutionary
tracks of Sch\"onberner. Terminal wind velocities of the stars were estimated
from the CIV and NV stellar wind features. The presence of stellar wind in some
of these stars indicates ongoing mass-loss.


title:
A multiband study of Hercules A. I. ROSAT observations of the
  intracluster medium

abstract:
  We have made ROSAT PSPC and HRI X-ray observations to study the intracluster
gas surrounding the powerful radio source Hercules A. The cluster is luminous
in X-rays (L_bol = 4.8x10^37 W), and the host of the radio source is the
central dominating galaxy of the cluster. The X-ray surface brightness profile
is well fitted by a modified King beta model, but the cluster is elongated
parallel to the radio source, especially on the scale of the radio lobes. Fits
to individual quadrants give a core radius 50 per cent larger along the radio
axis. Part of this elongation appears to be associated with enhanced X-ray
emission superimposed on the outer radio lobes. There are no obvious
depressions in the X-ray emission coincident with the radio lobes, as expected
if the relativistic plasma displaces the ICM. However, we show that these
depressions may be quite weak. From the surface brightness profile for the PSPC
data the X-ray emission extends out to ~ 2.2 Mpc radius. In the absence of the
powerful jets, we would expect a cooling flow at the centre of the cluster, but
currently it must be substantially disturbed by the expansion of the radio
lobes. The PSPC spectrum reveals a cool component of the ICM with 0.5 < kT < 1
keV. The central cooling time could be as low as 2 Gyr if the cool component is
centrally concentrated, otherwise it is around 6 Gyr. The modelled central
electron density is typical for modest cooling flows. Finally, we have detected
faint X-ray emission from a compact central source.


title: Energy release due to antineutrino untrapping from hot quark stars

abstract:
  An equation of state for 2-flavor quark matter (QM) with diquark condensation
under the conditions for compact stars -$\beta$-equilibrium, charge and color
neutrality- is presented. Trapped antineutrinos prevent the formation of the
diquark condensate at moderate densities above a critical value of the
antineutrino chemical potential $\mu_{\bar \nu_e}^c$. The following
consequences are presented: 1) The star develops a 2-phase structure
($\mu_{\bar \nu_e}\geq \mu_{\bar \nu_e}^c$): a color superconducting QM core
and a normal QM shell. 2)During the cooling, when the temperature is small
enough ($T<1$ MeV) the antineutrino mean free path becomes larger than the
thickness of the normal QM shell and the antineutrinos get untrapped in a
sudden burst. The energy release is estimated as $\simeq 10^{52}$ erg and an
antineutrino pulse is expected to be observed.


title: HST/FOS Eclipse mapping of IP Pegasi in outburst

abstract:
  We report the results of a time-resolved eclipse mapping of the dwarf nova IP
Pegasi during the decline of its May 1993 outburst from HST/FOS fast
spectroscopy covering 3 eclipses in the ultraviolet spectral range.


title:
X-ray behaviour of Circinus X-1 - I: X-ray Dips as a diagnostic of
  periodic behaviour

abstract:
  We examine the periodic nature of detailed structure (particularly dips) in
the RXTE/ASM lightcurve of Circinus X-1. The significant phase wandering of the
X-ray maxima suggests their identification with the response on a viscous
timescale of the accretion disk to perturbation. We find that the X-ray dips
provide a more accurate system clock than the maxima, and thus use these as
indicators of the times of periastron passage. We fit a quadratic ephemeris to
these dips, and find its predictive power for the X-ray lightcurve to be
superior to ephemerides based on the radio flares and the full archival X-ray
lightcurve. Under the hypothesis that the dips are tracers of the mass transfer
rate from the donor, we use their occurrence rate as a function of orbital
phase to explore the (as yet unconstrained) nature of the donor. The high
$\dot{P}$ term in the ephemeris provides another piece of evidence that Cir X-1
is in a state of dynamical evolution, and thus is a very young post-supernova
system. We further suggest that the radio ``synchrotron nebula'' immediately
surrounding Cir X-1 is in fact the remnant of the event that created the
compact object, and discuss briefly the evidence for and against such an
interpretation.


title:
X-ray spectral and timing properties of the 2001 superburst of 4U
  1636-536

abstract:
  Preliminary results are reported on the spectral and timing properties of the
spectacular 2001 superburst of 4U 1636-536 as seen by the RXTE/PCA. The
(broad-band) power-spectral and hardness properties during the superburst are
compared to those just before and after the superburst. Not all of the
superburst emission can be fitted by pure black-body radiation. We also
gathered BeppoSAX/WFC and RXTE/ASM data, as well as other RXTE/PCA data,
obtained days to months before and after the superburst to investigate the
normal X-ray burst behavior around the time of the superburst. The first normal
X-ray burst after the 2001 superburst was detected 23 days later. During
inspection of all the RXTE/ASM data we found a third superburst. This
superburst took place on June 26, 1999, which is ~2.9 yrs after the 1996
superburst and ~1.75 yrs before the 2001 superburst. The above findings are the
strongest constraints observed so far on the duration of the cessation of
normal X-ray bursts after a superburst and the superburst recurrence times.


title: Spectra and Light Curves of GRB Afterglows

abstract:
  We performed accurate numerical calculations of angle-, time-, and
frequency-dependent radiative transfer for the relativistic motion of matter in
gamma-ray burst (GRB) models. Our technique for solving the transfer equation,
which is based on the method of characteristics, can be applied to the motion
of matter with a Lorentz factor up to 1000. The effect of synchrotron
self-absorption is taken into account. We computed the spectra and light curves
from electrons with a power-law energy distribution in an expanding
relativistic shock and compare them with available analytic estimates. The
behavior of the optical afterglows from GRB 990510 and GRB 000301c is discussed
qualitatively.


title:
Mid-infrared observations of young stellar objects in the vicinity of
  sigma Orionis

abstract:
  We present new mid-infrared observations of objects in the vicinity of the
O-star sigma Orionis, obtained with TIMMI-2 at ESO. By constraining their near-
and mid-infrared spectral energy distributions, we established the nature of
previously known IRAS sources and identified new mid-infrared sources as young
stellar objects with circumstellar disks, likely massive members of the sigma
Ori cluster. For two of these objects we have obtained spectroscopy in the 8-13
micron range in order to investigate the chemistry of the dust grains. TX Ori
exhibits a typical silicate emission feature at 10 micron, with a feature at
about 11.2 micron that we identify as due to crystalline olivine. The IRAS
05358-0238 spectrum is very unusual, with a weak silicate feature and structure
in the range 10-12 micron that may be explained as due to self-absorbed
forsterite. We also provide the first evidence for the presence of
circumstellar disks in the jet sources Haro 5-39/HH 447, V510 Ori/HH 444 and
V603 Ori/HH 445.


title: On the globular cluster formation history of NGC 5128

abstract:
  We deduce the globular cluster formation history of the nearby elliptical NGC
5128 by using a phenomenological chemical enrichment model to reproduce its
observed metallicity distribution function (MDF). We derive the observed MDF
using recently obtained U and B photometry of the NGC 5128 GC system, with
(U-B) used as the metallicity indicator. We test whether the observed MDF can
be reproduced using a single starburst at high redshift followed by passive
evolution (monolithic scenario). Our results strongly indicate that this
scenario is incapable of reproducing the observed MDF of the NGC 5128 GC
system. At least one more major starburst is required. A persistent feature of
our best-fit models is a strong GC formation episode in the first 1-2 Gyrs,
followed by a second formation episode typically after 10-12 Gyrs. Roughly
one-third of the stellar mass in the GC system is created in this late
starburst, producing clusters that are potentially less than 1 Gyr old.
Although we do not have adequate resolution in the model or in the observed MDF
to make a reliable claim about the possibility of additional GC formation
episodes, our results suggest that the GCs in this galaxy did not form solely
in a monolithic collapse and seem to support observational evidence which
indicates that NGC 5128 is a merger remnant.


title:
Probing the Evolution of the Dark Energy Density with Future Supernova
  Surveys

abstract:
  The time dependence of the dark energy density can be an important clue to
the nature of dark energy in the universe. We show that future supernova data
from dedicated telescopes (such as SNAP), when combined with data of nearby
supernovae, can be used to determine how the dark energy density $\rho_X(z)$
depends on redshift, if $\rho_X(z)$ is not too close to a constant. For
quantitative comparison, we have done an extensive study of a number of dark
energy models. Based on these models we have simulated data sets in order to
show that we can indeed reconstruct the correct sign of the time dependence of
the dark energy density, outside of a degeneracy region centered on $1+w_0 =
-w_1 z_{max}/3$ (where $z_{max}$ is the maximum redshift of the survey, e.g.,
$z_{max}=1.7$ for SNAP). We emphasize that, given the same data, one can obtain
much more information about the dark energy density directly (and its time
dependence) than about its equation of state.


title: Star Formation in Cluster Cooling Flows

abstract:
  New X-ray observations from the {\it Chandra} and XMM-{\it Newton}
observatories have shown that cooling of the intracluster medium is occurring
at rates that are now approaching the star formation rates measured in cD
galaxies at the bases of cooling flows. Star formation proceeds in repeated
episodes, possibly indicating an intermittent fuel supply. Coupled with new
evidence for heating by AGN, a new paradigm of self-regulated cooling and star
formation in cluster cores is emerging.


title:
The relation between AGN hard X-ray emission and mid-infrared continuum
  from ISO spectra: Scatter and unification aspects

abstract:
  We use mid-infrared spectral decomposition to separate the 6micron
mid-infrared AGN continuum from the host emission in the ISO low resolution
spectra of 71 active galaxies and compare the results to observed and intrinsic
2-10keV hard X-ray fluxes from the literature. We find a correlation between
mid-infrared luminosity and absorption corrected hard X-ray luminosity, but the
scatter is about an order of magnitude, significantly larger than previously
found with smaller statistics. Main contributors to this scatter are likely
variations in the geometry of absorbing dust, and AGN variability in
combination with non-simultaneous observations. There is no significant
difference between Type 1 and Type 2 objects in the average ratio of
mid-infrared and hard X-ray emission, a result which is not consistent with the
most simple version of a unified scheme in which an optically and geometrically
thick torus dominates the mid-infrared AGN continuum. Most probably,
significant non-torus contributions to the AGN mid-IR continuum are masking the
expected difference between the two types of AGN.


title: High-Energy Neutrino Astronomy

abstract:
  Kilometer-scale neutrino detectors such as IceCube are discovery instruments
covering nuclear and particle physics, cosmology and astronomy. Examples of
their multidisciplinary missions include the search for the particle nature of
dark matter and for additional small dimensions of space. In the end, their
conceptual design is very much anchored to the observational fact that Nature
accelerates protons and photons to energies in excess of $10^{20}$ and
$10^{13}$ eV, respectively. The cosmic ray connection sets the scale of cosmic
neutrino fluxes. In this context, we discuss the first results of the completed
AMANDA detector and the reach of its extension, IceCube. Similar experiments
are under construction in the Mediterranean. Neutrino astronomy is also
expanding in new directions with efforts to detect air showers, acoustic and
radio signals initiated by super-EeV neutrinos.


title:
Resonance in Forced Oscillations of an Accretion Disk and Kilohertz
  Quasi Periodic Oscillations

abstract:
  We have performed numerical simulations of a radially perturbed "accretion"
torus around a black hole or neutron star and find that the torus performs
radial and vertical motions at the appropriate epicyclic frequencies. We find
clear evidence that vertical motions are excited in a non-linear resonance when
the applied perturbation is periodic in time. The strongest resonant response
occurs when the frequency difference of the two oscillations is equal to
one-half the forcing frequency, precisely as recently observed in the accreting
pulsar, SAX J1808.4-3658, where the observed kHz QPO peak separation is half
the spin frequency of 401 Hz.


title:
The Host Galaxy of GRB 031203: Implications of its low metallicity, low
  redshift, and starburst nature

abstract:
  We present Keck/NIRSPEC near-IR images and Magellan/IMACS optical
spectroscopy of the host galaxy of GRB 031203. The host is an actively
star-forming galaxy at z=0.1055 +/- 0.0001. This is the lowest redshift GRB
to-date, aside from GRB 980425. From the hydrogen Balmer lines, we infer an
extinction of A_V = 3.62 +/- 0.25 or a total reddening E_T(B-V) = 1.17 +/- 0.1
toward the sightline to the nebular regions. After correcting for reddening, we
perform an emission-line analysis and derive an ISM temperature of
T=13400+/-2000K and electron density of n_e = 300 cm^(-3). These imply a
metallicity [O/H]=-0.72+/-0.15 dex and a roughly solar abundance pattern for N,
Ne, S, and Ar. Integrating Ha, we infer a dust-corrected star formation rate
(SFR) of > 11 Msol/yr. These observations have the following implications: (1)
the galaxy has a low K'-band luminosity L ~ L^*/5, typical of GRB host
galaxies; (2) the low redshift indicates GRB 031203 had an isotropic-equivalent
gamma-ray energy release smaller than all previous confirmed GRB events. The
burst discovery raises the likelihood of identifying many additional low z, low
flux events with Swift; (3) the large SFR, low metallicity, and the inferred
hard radiation field is suggestive of massive star formation, supporting the
collapsar model; (4) several lines of evidence argue against the identification
of GRB 031203 as an X-ray flash event.


title: A Plausible Galactic Spiral Pattern and its Rotation Speed

abstract:
  We report calculations of the stellar and gaseous response to a Milky Way
mass distribution model including a spiral pattern with a locus as traced by
K-band observations, over imposed on the axisymmetric components in the plane
of the disk. The stellar study extends calculations from previous work
concerning the self-consistency of the pattern. The stellar response to the
imposed spiral mass is studied via computations of the central family of
periodic and nearby orbits as a function of the pattern rotation speed,
$\Omega_p$, among other parameters. A fine grid of values of $\Omega_p$ was
explored ranging from 12 to 25 $km s^{-1} kpc^{-1}$. Dynamical self-consistency
is highly sensitive to $\Omega_p$, with the best fit appearing at 20 $km s^{-1}
kpc^{-1}$. We give an account of recent independent pieces of theoretical and
observational work that are dependent on the value of $\Omega_p$, all of which
are consistent with the value found here; the recent star formation history of
the Milky Way, local inferences of cosmic ray flux variations and Galactic
abundance patterns. The gaseous response, which is also a function of
$\Omega_p$, was calculated via 2D hydrodynamic simulations with the ZEUS code.
For $\Omega_p = 20 km s^{-1} kpc^{-1}$, the response to a two-armed pattern is
a structured pattern of 4 arms, with bifurcations along the arms and interarm
features. The pattern resembles qualitatively the optical arms observed in our
Galaxy and other galaxies. The complex gaseous pattern appears to be linked to
resonances in stellar orbits. Among these, the 4:1 resonance plays an important
role, as it also determines the extent over which the imposed spiral pattern is
dynamically self-consistent.


title: Diffuse X-ray Emission in a Deep Chandra Image of the Galactic Center

abstract:
  We examine the spectrum of diffuse emission detected in the 17' by 17' field
around Sgr A* during 625 ks of Chandra observations. The spectrum exhibits
He-like and H-like lines from Si, S, Ar, Ca, and Fe, that are consistent with
originating in a two-temperature plasma, as well as a prominent low-ionization
Fe line. The cooler, kT=0.8 keV plasma differs in surface brightness across the
image by a factor of 9. This soft plasma is probably heated by supernovae. The
radiative cooling rate of the plasma within the inner 20 pc of the Galaxy could
be balanced by 1% of the kinetic energy of one supernova every 300,000 y. The
hotter, kT=8 keV component is more spatially uniform, ranging over a factor of
2 in surface brightness. The intensity of the hard plasma is correlated with
that of the soft, but they are probably only indirectly related, because
supernova remnants are not observed to produce thermal plasma hotter than kT=3
keV. Moreover, a kT=8 keV plasma is too hot to be bound to the Galactic center,
and therefore would form a slow wind or fountain of plasma. The energy required
to sustain such a freely-expanding plasma within the inner 20 pc of the Galaxy
is ~10^40 erg/s, which corresponds to the entire kinetic energy of one
supernova every 3000 y. This rate is unreasonably high. However, alternative
explanations for the kT=8 keV diffuse emission are equally unsatisfying. We are
left to conclude that either the diffuse emission is heated by an unanticipated
source of energy, or that a population of faint (< 10^31 erg/s), hard X-ray
sources that are a factor of 10 more numerous than CVs remains to be
discovered. (Abridged)


title:
Spectral Features in the Thermal Emission from Isolated Neutron Stars:
  Dependence on Magnetic Field Strengths

abstract:
  We study several effects that influence the strength of the proton cyclotron
and atomic features in the thermal spectra of magnetic neutron stars. We show
that it is possible for vacuum polarization to strongly suppress the spectral
lines when the magnetic field B\ga 10^14 G. For weaker fields (B\la 7\times
10^13 G), the surface spectrum is unaffected by vacuum polarization; thus the
proton cyclotron absorption line can have a large equivalent width. Using an
approximate calculation of the synthetic spectra, we show that variation of
magnetic fields over the neutron star surface leads to broadening of the line.
The recently detected absorption features from the isolated neutron stars RX
J1308.6+2127, RX J1605.3+3249, and RX J0720.4-3125 can plausibly be explained
by the proton cyclotron resonance, with possible blending due to atomic
transitions, in the atmosphere of the star.


title: Gamma-ray Luminosity and Death Lines of Pulsars with Outer Gaps

abstract:
  We re-examine the outer gap size by taking the geometry of the dipole
magnetic field into account. Furthermore, we also consider that instead of
taking the gap size at half of the light cylinder radius to represent the
entire outer gap it is more appropriate to average the entire outer gap size
over the distance. When these two factors are considered, the derived outer gap
size f is not only the function of period P and magnetic field B of the neutron
star, but also the function of the average radial distance to the neutron star
<r>. We use this new outer gap model to study $\gamma$-ray luminosity of
pulsars, and to study the death lines of $\gamma$-ray emission of the pulsars.
Our model can predict the $\gamma$-ray luminosity of individual pulsar if its
$P, B$ and $\alpha$ are known. Since different pulsars have different $\alpha$,
this explains why some $\gamma$-ray pulsars have very similar $P$ and $B$ but
have very different $\gamma$-ray luminosities. In determining the death line of
$\gamma$-ray pulsars, we have used a new criterion based on concrete physical
reason. In estimate of the fractional size of the outer gap, two possible X-ray
fields are considered: (i) X-rays are produced by the neutron star cooling and
polar cap heating, and (ii)X-rays are produced by the bombardment of the
relativistic particles from the outer gap on the stellar surface. Since it is
very difficult to measure $\alpha$ in general, we use a Monte Carlo method to
simulate the properties of $\gamma$-ray pulsars in our galaxy. We find that
this new outer gap model predicts many more weak $\gamma$-ray pulsars. For all
simulated $\gamma$-ray pulsars with self-sustained outer gaps, $\gamma$-ray
luminosity $L_{\gamma}$ satisfies $L_{\gamma}\propto L^{\delta}_{sd}$; where
the value of $\delta$ depends on the ensitivity of the $\gamma$-ray detector.


title: Observational Evidence of Pitch Angle Isotropization by IMF Waves

abstract:
  A statistical analysis of interstellar He+ pickup ion measurements from
SOHO/CTOF combined with magnetic field data from WIND/MFI enable quantitative
study of wave-particle interactions in the inner heliosphere for the first
time. Magnetic field vector measurements with a time resolu-tion of 3 seconds
are used to determine power spectrum char-acteristics of interplanetary
magnetic turbulence. These spec-tral characteristics are then compared in
superposed epoch and correlation analyses with He+ fluxes and spectra. The
observed pickup ion velocity distributions can be explained consistently as a
consequence of pitch angle scattering of the interstellar pickup ions by
Alfvenic fluctuations.


title:
Gravitational Waves from Extragalactic Inspiraling Binaries: Selection
  Effects and Expected Detection Rates

abstract:
  We examine the selection effects that determine how the population of
inspiraling binary compact objects (BCOs) is reflected by those potentially
observed with ground-based interferometers like LIGO. We lay the ground-work
for the interpretation of future observations in terms of constraints on the
real population and, correspondingly, binary star evolution models.
  To determine the extra-galactic population of inspiraling binaries we combine
data on distance and blue luminosity from galaxy catalogs with current models
of the galactic BCO mass distribution to simulate the physical distribution of
binaries in the nearby universe. We use Monte Carlo methods to determine the
fraction of binaries observable by the LIGO detectors from each galaxy as a
function of the BCO chirp mass. We examine separately the role of source
distance, sky position, time of detection, and binary system chirp mass on
detection efficiency and selection effects relevant to the three LIGO
detectors. Finally, we discuss the implications of the nearby geography of
space on anticipated GW detection and compare our results to previous studies,
which have assumed uniform galaxy volume density and fixed chirp mass for
binary compact objects.
  From these considerations, actual BCO inspiral observations or significant
upper limits on the coalescence rate anticipated in the near future by
ground-based interferometers can be used to improve our knowledge of the
galactic binary inspiral rate and to constrain models of radio pulsar
characteristics and binary star evolution channels leading to neutron star or
black hole binaries.


title:
Influence of shower fluctuations and primary composition on studies of
  the shower longitudinal development

abstract:
  We study the influence of shower fluctuations, and the possible presence of
different nuclear species in the primary cosmic ray spectrum, on the
experimental determination of both shower energy and the proton air inelastic
cross section from studies of the longitudinal development of atmospheric
showers in fluorescence experiments. We investigate the potential of track
length integral and shower size at maximum as estimators of shower energy. We
find that at very high energy (~10^19-10^20 eV) the error of the total energy
assignment is dominated by the dependence on the hadronic interaction model,
and is of the order of 5%. At lower energy (~10^17-10^18 eV), the uncertainty
of the energy determination due to the limited knowledge of the primary cosmic
ray composition is more important. The distribution of depth of shower maximum
is discussed as a measure of the proton-air cross section. Uncertainties in a
possible experimental measurement of this cross section introduced by intrinsic
shower fluctuations, the model of hadronic interactions, and the unknown
mixture of primary nuclei in the cosmic radiation are numerically evaluated.


title: Bowen Fluorescence from Companion Stars in X-ray Binaries

abstract:
  This paper will review a new technique of detecting companion stars in LMXBs
and X-ray transients in outburst using the Bowen fluorescence lines at
4634-4640 Angs. These lines are very efficiently reprocessed in the atmospheres
of the companion stars, and thereby provide estimates of the K2 velocities and
mass functions. The method has been applied to Sco X-1, X1822-371 and GX339-4
which, in the latter case, provides the first dynamical evidence for the
presence of an accreting black hole. Preliminary results from a VLT campaign on
V801 Ara, V926 Sco and XTE J1814-338 are also presented.


title: The Top Ten solar analogs in the ELODIE library

abstract:
  Several solar analogs have been identified in the library of high resolution
stellar spectra taken with the echelle spectrograph ELODIE. A purely
differential method has been used, based on the chi2 comparison of a large
number of G dwarf spectra to 8 spectra of the Sun, taken on the Moon and Ceres.
HD 146233 keeps its status of closest ever solar twin (Porto de Mello & da
Silva 1997). Some other spectroscopic analogs have never been studied before,
while the two planet-host stars HD095128 and HD186427 are also part of the
selection. The fundamental parameters found in the literature for these stars
show a surprising dispersion, partly due to the uncertainties which affect
them.
  We discuss the advantages and drawbacks of photometric and spectroscopic
methods to search for solar analogs and conclude that they have to be used
jointly to find real solar twins.


title: Mapping the 3-D dark matter with weak lensing in COMBO-17

abstract:
  We present a 3-dimensional lensing analysis of the z=0.16 supercluster
A901/2, resulting in a 3-D map of the dark matter distribution within a 3 X
10^{5} [Mpc]^3 volume from the COMBO-17 survey. We perform a chi^2-fit of
isothermal spheres to the tangential shear pattern around each cluster as a
function of redshift to estimate the 3-D positions and masses of the main
clusters in the supercluster from lensing alone. We then present the first 3-D
map of the dark matter gravitational potential field, Phi, using the
Kaiser-Squires (1993) and Taylor (2001) inversion methods. These maps clearly
show the potential wells of the main supercluster components, including a new
cluster behind A902, and demonstrates the applicability of 3-D dark matter
mapping and projection free-mass-selected cluster finding to current data.
Finally, we develop the halo model of dark matter and galaxy clustering and
compare this with the auto-and cross-correlation functions of the 3-D
gravitational potential, galaxy number densities and galaxy luminosity
densities measured in the A901/2 field. We find significant anti-correlations
between the gravitational potential field and the galaxy number density and
luminosities, as expected due to baryonic infall into dark matter
concentrations. We find good agreement with the halo model for the number
densities and luminosity correlation functions.


abstract:
  We present here results obtained from three BeppoSAX observations of the
accretion-powered X-ray pulsar SMC X-1 carried out during the declining phases
of its 40--60 days long super-orbital period. Timing analysis of the data
clearly shows a continuing spin-up of the neutron star. Energy-resolved timing
analysis shows that the pulse-profile of SMC X-1 is single peaked at energies
less than 1.0 keV whereas an additional peak, the amplitude of which increases
with energy within the MECS range, is present at higher energies. Broad-band
pulse-phase-averaged spectroscopy of the BeppoSAX data, which is done for the
first time since its discovery, shows that the energy spectrum in the 0.1--80
keV energy band has three components, a soft excess that can be modeled as a
thermal black-body, a hard power-law component with a high-energy exponential
cutoff and a narrow and weak iron emission line at 6.4 keV. Pulse-phase
resolved spectroscopy indicates a pulsating nature of the soft spectral
component, as seen in a few other binary X-ray pulsars, with a certain phase
offset with respect to the hard power-law component. Dissimilar shape and phase
of the soft and hard X-ray pulse profiles suggest a different origin of the
soft and hard components.


title: Kinematic solar dynamo models with a deep meridional flow

abstract:
  We develop two different solar dynamo models to verify the hypothesis that a
deep meridional flow can restrict the apperance of sunspots below 45 degrees,
proposed by Nandy & Choudhuri (2002). In the first one, a single polytropic
approximation for the density profile was taken, for both radiative and
convective zones. In the second one, two polytropes were used to distinguish
between both zones Pinzon & Calvo-Mozo (2001). The magnetic buoyancy mechanism
proposed by Dikpati & Charbonneau (1999) was chosen in both models. We,
actually, have obtained that a deep meridional flow pushes the maxima of
toroidal magnetic field toward the solar equator, but in contrast to Nandy &
Choudhuri (2002) a second zone of maximal fields remains at the poles. The
second model, although closely resembling the solar standard model of Bahcall,
Pinsonneault & Wasserbug (1995); Bahcall, Pinsonneault & Basu (2001), gives
solar cyles three times longer than observed.


title:
A filamentary structure of massive star-forming galaxies associated with
  an X-ray absorbed QSO at z=1.8

abstract:
  The genesis of spheroids is central to our understanding of galaxy formation
-- they are relatively simple systems, containing about half the stellar mass
of the Universe. A major subset of spheroids, massive elliptical galaxies, are
preferentially found in clusters where they exhibit old, coeval stellar
populations suggesting that they formed synchronously at early epochs. Here we
report SCUBA submillimeter imaging of a region around a z=1.8 X-ray selected
QSO. The image reveals a remarkable 400 kiloparsec long chain of galaxies each
with an obscured star-formation rate sufficiently high to build a massive
spheroid in less than 1 Gyr. The large over-density of these galaxies relative
to expectations for a random field implies they probably reside in a structure
associated with the QSO. We suggest that this star formation is associated with
galaxy mergers or encounters within the filament, such as those predicted by
the popular hierarchical model of galaxy formation. Our observations suggest
that strong absorption in the X-ray spectra of QSOs at high-redshifts may
result from a veil of gas thrown up by a merger or merger-induced activity,
rather than an orientation-dependent obscuring torus. It is argued that these
systems are the precursors of elliptical galaxies found today in the core
regions of all rich galaxy clusters.


title:
Interferometric observations of the supergiant stars alpha Orionis and
  alpha Herculis with FLUOR at IOTA

abstract:
  We report the observations in the K band of the red supergiant star alpha
Orionis and of the bright giant star alpha Herculis with the FLUOR beamcombiner
at the IOTA interferometer. The high quality of the data allows us to estimate
limb-darkening and derive precise diameters in the K band which combined with
bolometric fluxes yield effective temperatures. In the case of Betelgeuse, data
collected at high spatial frequency although sparse are compatible with
circular symmetry and there is no clear evidence for departure from circular
symmetry. We have combined the K band data with interferometric measurements in
the L band and at 11.15 micron. The full set of data can be explained if a 2055
K layer with optical depths $\tau_{K}=0.060\pm0.003$, $\tau_{L}=0.026\pm0.002$
and $\tau_{11.15\mu m}=2.33\pm0.23$ is added 0.33 $R_{\star}$ above the
photosphere providing a first consistent view of the star in this range of
wavelengths. This layer provides a consistent explanation for at least three
otherwise puzzling observations: the wavelength variation of apparent diameter,
the dramatic difference in limb darkening between the two supergiant stars, and
the previously noted reduced effective temperature of supergiants with respect
to giants of the same spectral type. Each of these may be simply understood as
an artifact due to not accounting for the presence of the upper layer in the
data analysis. This consistent picture can be considered strong support for the
presence of a sphere of warm water vapor, proposed by Tsuji (2000) when
interpreting the spectra of strong molecular lines.


title: IR photometric properties of Red Giants in omega Cen

abstract:
  We present a near-infrared J and K photometric catalog containing more than
73,000 stars in the central region of the giant Globular Cluster omega
Centauri. This is the largest IR data-set ever published for this cluster and
has been used to completely characterize the morphology and the properties of
the Red Giant Branch (RGB). In particular, we concentrated our attention on (i)
the anomalous RGB (RGB-a), recently discovered in this cluster and (ii) the RGB
of the dominant metal poor population (RGB-MP) in both the infrared (K,J-K) and
optical-infrared (K,V-K) color magnitude diagrams. The full set of
morphological parameters and photometric indices has been measured and compared
with the empirical relations by Ferraro et al. (2000). We find that the
detailed photometric properties of the RGB-a are in full agreement with the
recent spectroscopic metallicity estimates, that place it at the metal-rich
extreme of the stellar population mix in omega Centauri.


title:
Relativistic Iron Lines in Galactic Black Holes: Recent Results and
  Lines in the ASCA Archive

abstract:
  Recent observations with Chandra and XMM-Newton, aided by broad-band spectral
coverage from RXTE, have revealed skewed relativistic iron emission lines in
stellar-mass Galactic black hole systems. Such systems are excellent
laboratories for testing General Relativity, and relativistic iron lines
provide an important tool for making such tests. In this contribution to the
Proceedings of the 10th Annual Marcel Grossmann Meeting on General Relativity,
we briefly review recent developments and present initial results from fits to
archival ASCA observations of Galactic black holes. It stands to reason that
relativistic effects, if real, should be revealed in many systems (rather than
just one or two); the results of our archival work have borne-out this
expectation. The ASCA spectra reveal skewed, relativistic lines in XTE
J1550-564, GRO J1655-40, GRS 1915+105, and Cygnus X-1.


title:
XMM-Newton spectral and timing analysis of the faint millisecond pulsars
  PSR J0751+1807 and PSR J1012+5307

abstract:
  We present XMM-Newton MOS imaging and PN timing data of the faint millisecond
pulsars PSR J0751+1807 and PSR J1012+5307. We find 46 sources in the MOS field
of view of PSR J0751+1807 searching down to an unabsorbed flux limit of 3 x
10^-15 ergs cm^-2 s^-1 (0.2-10.0 keV). We present, for the first time, the
X-ray spectra of these two faint millisecond pulsars. We find that a power law
model best fits the spectrum of PSR J0751+1807, Gamma=1.59+/-0.20, with an
unabsorbed flux of 4.4 x 10^-14 ergs cm^-2 s^-1 (0.2-10.0 keV). A power law is
also a good description of the spectrum of PSR J1012+5307, Gamma=1.78+/-0.36,
with an unabsorbed flux of 1.2 x 10^-13 ergs cm^-2 s^-1 (0.2-10.0 keV).
However, a blackbody model can not be excluded as the best fit to this data. We
present some evidence to suggest that both of these millisecond pulsars show
pulsations in this X-ray band. We find some evidence for a single broad X-ray
pulse for PSR J0751+1807 and we discuss the possibility that there are two
pulses per spin period for PSR J1012+5307.


title: Some updates on the role of Magnetic Fields in Cataclysmic Variables

abstract:
  In this review talk I cover some recent developments in understanding the
role that magnetic fields play in cataclysmic variables. I discuss the recent
DNO--QPO unification models; the disk--magnetosphere boundary; some issues
concerning the soft blackbody component and the nature of the X-ray spectra in
MCVs; whether the SW Sex stars are magnetic, and finally I mention the weird
behavior of FS Aur and HS2331+3905.


title:
HD 77407 and GJ 577: two new young stellar binaries detected with the
  Calar Alto Adaptive Optics system ALFA

abstract:
  We present the first results from our search for close stellar and
sub-stellar companions to young nearby stars on the northern sky. Our infrared
imaging observations are obtained with the 3.5 m Calar Alto telescope and the
AO system ALFA. With two epoch observations which were separated by about one
year, we found two co-moving companion candidates, one close to HD 77407 and
one close to GJ 577. For the companion candidate near GJ 577, we obtained an
optical spectrum showing spectral type M4.5; this candidate is a bound low-mass
stellar companion confirmed by both proper motion and spectroscopy. We estimate
the masses for HD 77407 B and GJ 577 B to be ~0.3 to 0.5 Msun and ~0.16 to 0.2
Msun, respectively. Compared to Siess al.(2000) models, each of the two pairs
appears co-eval with HD 77407 A,B being 10 to 40 Myrs old and GJ 577 A,B being
older than 100 Myrs. We also took multi-epoch high-resolution spectra of HD
77407 to search for sub-stellar companions, but did not find any with 3 Mjup as
upper mass (msin(i)) limit (for up to 4 year orbits); however, we detected a
long-term radial velocity trend in HD 77407 A, consistent with a ~ 0.3 Msun
companion at ~ 50 AU separation, i.e. the one detected by the imaging. Hence,
HD 77407 B is confirmed to be a bound companion to HD 77407 A. We also present
limits for undetected, but detectable companions using a deep image of HD 77407
A and B, also observed with the Keck NIRC2 AO system; any brown dwarfs were
detectable outside of 0.5 arcsec (17 AU at HD 77407), giant planets with masses
from ~ 6.5 to 12 Mjup were detectable at > 1.5 arcsec.


title:
XMM-Newton observations of the BL Lac MS0205.7+3509: a dense,
  low-metallicity absorber

abstract:
  The high-frequency-peaked BL Lac, MS0205.7+3509 was observed twice with
XMM-Newton. Both X-ray spectra are synchrotron-dominated, with mean 0.2--10keV
fluxes of 2.80+/-0.01 and 3.34+/-0.02 E-12 erg/cm^2/s. The X-ray spectra are
well fit by a power-law with absorption above the Galactic value, however no
absorption edges are detected, implying a low metallicity absorber (Z_\sun =
0.04(+0.03)(-0.01)) or an absorber with redshift above one (best-fit z=2.1 for
an absorber with solar abundances). In either case the absorbing column density
must be ~9E21 cm^-2. A new optical spectrum is presented, with a MgII
absorption doublet detected at z=0.351, but no other significant features. The
optical spectrum shows little reddening, implying a low dust to gas ratio in
the absorber. MS0205.7+3509 must therefore be viewed through a high column
density, low-metallicity gas cloud, probably at z=0.351 and associated with the
galaxy that has been shown to be within ~2" of the BL Lac.


title: Probing Sgr A* with theory of large masses without events horizon

abstract:
  In the present paper some consequences of the assumption that in the center
of the Galaxy there is a supermassive compact object without the events horizon
are considered. The possibility of existence of such object has been argued
earlier. It is shown, that accretion of a surrounding gas onto the object can
cause nuclear burning in a superficial layer which owing to comptonization in a
hotter layer, laying above, can manifest itself in observable IR and X spectra.
The contribution of an intrinsic magnetic moment of the object in the
observable synchrotron radiation is considered, using transfer equations,
taking into account influence of gravitation on the energy and movement of
photons.


title: Bimodal distribution of the autocorrelation function in gamma-ray bursts

abstract:
  Autocorrelation functions (ACFs) are studied for a sample of 16 long
gamma-ray bursts (GRBs) with known redshift z, that were observed by the BATSE
and Konus experiments. When corrected for cosmic time dilation, the ACF shows a
bimodal distribution. A narrow width class (11 bursts) has at half-maximum a
mean width of 1.6 s with a relative dispersion of 32%, while a broad width
class (5 bursts) has a width of 7.5 s with a 4% dispersion. The separation
between the two mean values is highly significant (> 7 standard deviations).
This temporal property could be used on the large existing database of GRBs
with unknown redshift. The broad width set shows a very good linear correlation
between width at half-maximum and (1+z), with a correlation coefficient R=0.995
and a probability of chance alignment <0.0004. The potential application of
this correlation to cosmology studies is discussed, using it in combination
with recently proposed luminosity indicators.


title:
X-ray emission from a metal depleted accretion shock onto the classical
  T Tauri star TW Hya

abstract:
  We present the X-ray spectrum of TW Hya observed at high and intermediate
spectral resolution with the Reflection Grating Spectrometer (RGS) and the
European Photon Imaging Camera (EPIC) onboard the XMM-Newton satellite. TW Hya
is the first classical T Tauri star for which simultaneous X-ray data with both
high spectral resolution and high sensitivity were obtained, thus allowing to
probe the X-ray emission properties of stars in the early pre-main sequence
phase. The high plasma density, the (comparatively) low temperature, and
peculiar chemical abundances in the X-ray emitting region on TW Hya are
untypical for stellar coronae. An alternative X-ray production mechanism is
therefore called for and a natural explanation is an accretion column depleted
of grain forming elements. The metal depletion could be either due to the
original molecular cloud that formed TW Hya or due to a settling of dust in the
circumstellar disk of TW Hya.


title: Alternative Dark Energy Models: An Overview

abstract:
  A large number of recent observational data strongly suggest that we live in
a flat, accelerating Universe composed of $\sim$ 1/3 of matter (baryonic +
dark) and $\sim$ 2/3 of an exotic component with large negative pressure,
usually named {\bf Dark Energy} or {\bf Quintessence}. The basic set of
experiments includes: observations from SNe Ia, CMB anisotropies, large scale
structure, X-ray data from galaxy clusters, age estimates of globular clusters
and old high redshift galaxies (OHRG's). Such results seem to provide the
remaining piece of information connecting the inflationary flatness prediction
($\Omega_{\rm{T}} = 1$) with astronomical observations. Theoretically, they
have also stimulated the current interest for more general models containing an
extra component describing this unknown dark energy, and simultaneously
accounting for the present accelerating stage of the Universe. An overlook in
the literature shows that at least five dark energy candidates have been
proposed in the context of general relativistic models. Since the cosmological
constant and rolling scalar field models have already been extensively
discussed, in this short review we focus our attention to the three remaining
candidates, namely: a decaying vacuum energy density (or ${\bf \Lambda(t)}$
{\bf models}), the {\bf X-matter}, and the so-called {\bf Chaplygin-type gas}.
A summary of their main results is given and some difficulties underlying the
emerging dark energy paradigm are also briefly examined.


title: POX 52: A Dwarf Seyfert 1 Galaxy With An Intermediate-Mass Black Hole

abstract:
  We describe new optical images and spectra of POX 52, a dwarf galaxy with an
active nucleus that was originally detected in the POX objective-prism survey.
While POX 52 was originally thought to be a Seyfert 2 galaxy, the new data
reveal an emission-line spectrum very similar to that of the dwarf Seyfert 1
galaxy NGC 4395, with broad components to the permitted line profiles, and we
classify POX 52 as a Seyfert 1 galaxy. The host galaxy appears to be a dwarf
elliptical, and its brightness profile is best fit by a Sersic model with an
index of 3.6+/-0.2 and a total magnitude of M_V = -17.6. Applying
mass-luminosity-linewidth scaling relations to estimate the black hole mass
from the broad H-beta linewidth and nonstellar continuum luminosity, we find
M_BH ~ 1.6x10^5 solar masses. The stellar velocity dispersion in the host
galaxy, measured from the Ca II 8498, 8542 Angstrom lines, is 36+/-5 km/s, also
suggestive of a black hole mass of order 10^5 solar masses. Further searches
for active nuclei in dwarf galaxies can provide unique constraints on the
demographics of black holes in the mass range below 10^6 solar masses.


title: Jet Deflection via Cross winds: Laboratory Astrophysical Studies

abstract:
  We present new data from High Energy Density (HED) laboratory experiments
designed to explore the interaction of a heavy hypersonic radiative jet with a
cross wind. The jets are generated with the MAGPIE pulsed power machine where
converging conical plasma flows are produced from a cylindrically symmetric
array of inclined wires. Radiative hypersonic jets emerge from the convergence
point. The cross wind is generated by ablation of a plastic foil via
soft-X-rays from the plasma convergence region. Our experiments show that the
jets are deflected by the action of the cross wind with the angle of deflection
dependent on the proximity of the foil. Shocks within the jet beam are apparent
in the data. Analysis of the data shows that the interaction of the jet and
cross wind is collisional and therefore in the hydro-dynamic regime. MHD plasma
code simulations of the experiments are able to recover the deflection
behaviour seen in the experiments. We consider the astrophysical relevance of
these experiments applying published models of jet deflection developed for AGN
and YSOs. Fitting the observed jet deflections to quadratic trajectories
predicted by these models allows us to recover a set of plasma parameters
consistent with the data. We also present results of 3-D numerical simulations
of jet deflection using a new astrophysical Adaptive Mesh Refinement code.
These simulations show highly structured shocks occurring within the beam
similar to what was observed in the experiments


title:
Deuterium and Li7 Concordance in Inhomogeneous Big Bang Nucleosynthesis
  Models

abstract:
  Recent observational constraints on primodial deuterium and Li7 correspond to
different values of the baryon-to-photon ratio when applied to the Standard Big
Bang Nucleosynthesis (SBBN) model. In this article these constraints are
applied to baryon Inhomogeneous (IBBN) models. A depletion factor of 3.4
applied to the Li7 constraints will bring Li7, deuterium and He4 constraints in
concordance for both the SBBN and IBBN models. A depletion factor of 6.1 will
bring concordance for the IBBN model alone.


title:
Probing Kolmogorov turbulence beyond the Magellanic Clouds: The Power of
  Southern Hemisphere's largest optical telescope (11m), SALT

abstract:
  The Hubble classification scheme of galaxies is based on blue-light
appearance. Atlases reveal the rich variety of responses of the Population I
component (`the mask') of gas and dust to the underlying, older, stellar
population. However, the Population I component may only constitute 5 percent
of the dynamical mass of the galaxy; furthermore, dusty masks are highly
effective in hiding bars. We firstly discuss the rich duality in spiral
structure, and highlight a near-infrared classification scheme for spiral
galaxies. We next show that images secured with SALTICAM will be ideally suited
to probe key questions such as whether the optical light in the gaseous
Population I component is the result of Kolmogorov turbulence, cascasding from
the largest of scales down to the Nyquist limit. If so, the optical emission in
galaxies will be organized in a global fractal pattern with an intrinsic 1D
power spectrum having a slope of -5/3, or -8/3 in 2D.


title: What do we (not) know theoretically about solar neutrino fluxes?

abstract:
  Solar model predictions of 8B and p-p neutrinos agree with the
experimentally-determined fluxes (including oscillations): phi(pp)_{measured} =
(1.02 +- 0.02 +- 0.01)phi(pp)_{theory}, and phi(8B)_{measured} =(0.88 +- .04 +-
0.23)phi(8B)_{theory}, 1 sigma experimental and theoretical uncertainties,
respectively. We use improved input data for nuclear fusion reactions, the
equation of state, and the chemical composition of the Sun. The solar
composition is the dominant uncertainty in calculating the 8B and CNO neutrino
fluxes; the cross section for the 3He(4He, gamma)7Be reaction is the largest
uncertainty for the calculated 7Be neutrino flux.


title: The intergalactic medium temperature and Compton y parameter

abstract:
  (Abridged) The precision modeling of the thermal Sunyaev Zeldovich (SZ)
effect and future high accuracy measurements will provide a powerful way to
constrain the thermal history of the universe. In this paper, we combine high
resolution adiabatic hydro simulations and analytical models to provide a
precision modeling of the gas density weighted temperature $\bar{T}_g$ and the
mean SZ Compton $y$ parameter. Simulation artifacts are quantified and
corrected and our analytical model passes tests of various simulations and is
able to predict $\bar{T}_g$ and $\bar{y}$ to several percent accuracy. For low
matter density $\Lambda$CDM cosmology, the present $\bar{T}_g$ is $0.32
(\sigma_8/0.84)^{3.05-0.15\Omega_m}(\Omega_m/0.268)^{1.28-0.2\sigma_8} {\rm
keV}$. The mean $y$ parameter is $2.6\times 10^{-6}
(\sigma_8/0.84)^{4.1-2\Omega_m}(\Omega_m/0.268)^{1.28-0.2\sigma_8}$. The
current upper limit of $y<1.5\times 10^{-5}$ measured by FIRAS has already
ruled out combinations of high $\sigma_8\ga 1.1$ and high $\Omega_m\ga 0.5$.


title: Keck spectroscopy of CLASS gravitational lenses

abstract:
  We present the optical spectra of four newly discovered gravitational lenses
from the Cosmic Lens All-Sky Survey (CLASS). These observations were carried
out using the Low Resolution Imaging Spectrograph on the W. M. Keck-I Telescope
as part of a program to study galaxy-scale gravitational lenses. From our
spectra we found the redshift of the background source in CLASS B0128+437
(z_s=3.1240+-0.0042) and the lensing galaxy redshifts in CLASS B0445+123
(z_l=0.5583+-0.0003) and CLASS B0850+054 (z_l=0.5883+-0.0006). Intriguingly, we
also discovered that CLASS B0631+519 may have two lensing galaxies
(z_l,1=0.0896+-0.0001, z_l,2=0.6196+-0.0004). We also found a single
unidentified emission line from the lensing galaxy in CLASS B0128+437 and the
lensed source in CLASS B0850+054. We find the lensing galaxies in CLASS
B0445+123 and CLASS B0631+519 (l,2) to be early-type galaxies with Einstein
Radii of 2.8-3.0 h^{-1} kpc. The deflector in CLASS B0850+054 is a late-type
galaxy with an Einstein Radius of 1.6 h^{-1} kpc.


title: Optical Properties of faint FIRST Variable Radio Sources

abstract:
  A sample of 123 radio sources that exhibit significant variations at 1.4 GHz
on a seven year base-line has been created using FIRST VLA B-array data from
1995 and 2002 on a strip at dec=0 near the south Galactic cap. This sample
spans the range of radio flux densities from ~2 to 1000 mJy. It presents both
in size and radio flux density range a unique starting point for variability
studies of galaxies and quasars harboring lower luminosity Active Galactic
Nuclei (AGN). We find, by comparing our variable and non-variable control
samples to the Sloan Digital Sky Survey the following: 1) The quasar fraction
of both the variable and non-variable samples declines as a function of
declining radio flux density levels; 2) our variable sample contains a
consistently higher fraction of quasars than the non-variable control sample,
irrespective of radio flux; 3) the variable sources are almost twice as likely
to be retrieved from the optical SDSS data than the non-variable ones; 4) based
on relative numbers, we estimate that quasars are about five times more likely
to harbor a variable radio source than are galaxies; and 5) there does not
appear to be any significant optical color offset between the two samples, even
though the suggestive trend for sources to be bluer when variable has been
detected before and may be real. This leads us to conclude that both radio
variability and radio flux density levels, in combination with accurate optical
information, are important discriminators in the study of (radio) variability
of galaxies. The latter start to dominate the source counts below about 20 mJy.
In any case, variability appears to be an intrinsic property of radio sources,
and is not limited to quasars. Radio variability at low flux density levels may
offer a unique tool in AGN unification studies.


title:
Faint High-Latitude Carbon Stars Discovered by the Sloan Digital Sky
  Survey: An Initial Catalog

abstract:
  A search of more than 3,000 square degrees of high latitude sky by the Sloan
Digital Sky Survey has yielded 251 faint high-latitude carbon stars (FHLCs),
the large majority previously uncataloged. We present homogeneous spectroscopy,
photometry, and astrometry for the sample. The objects lie in the 15.6 < r <
20.8 range, and exhibit a wide variety of apparent photospheric temperatures,
ranging from spectral types near M to as early as F. Proper motion measurements
for 222 of the objects show that at least 50%, and quite probably more than
60%, of these objects are actually low luminosity dwarf carbon (dC) stars, in
agreement with a variety of recent, more limited investigations which show that
such objects are the numerically dominant type of star with C_2 in the
spectrum. This SDSS homogeneous sample of ~110 dC stars now constitutes 90% of
all known carbon dwarfs, and will grow by another factor of 2-3 by the
completion of the Survey. As the spectra of the dC and the faint halo giant C
stars are very similar (at least at spectral resolution of 1,000) despite a
difference of 10 mag in luminosity, it is imperative that simple luminosity
discriminants other than proper motion be developed. We use our enlarged sample
of FHLCs to examine a variety of possible luminosity criteria, including many
previously suggested, and find that, with certain important caveats, JHK
photometry may segregate dwarfs and giants.


title: On the Shallow Decay of Some GRB Afterglows

abstract:
  Half of the radio afterglows for which there is a good temporal coverage
exhibit after 10 days from the burst a decay which is shallower than at optical
frequencies, contrary to what is expected within the simplest form of the
standard model of relativistic fireballs or jets. We investigate possible ways
to decouple the radio and optical decays. First, the radio and optical
emissions are assumed to arise from the same electron population and we allow
for either a time-varying slope of the power-law distribution of electron
energy or for time-varying microphysical parameters. Then we consider two
scenarios where the radio and optical emissions arise in distinct parts of the
  GRB outflow, either because the outflow has an angular structure or because
there is a long-lived reverse shock. We find that the only the last scenario is
compatible with the observations.


title: A mid-IR survey of the L 1641-N region with ISOCAM

abstract:
  We present an analysis of the L 1641 outflow region using broad-band and
narrow-band imaging data at mid-infrared wavelengths from ISOCAM. We detect a
total of 34 sources in the $7.65^{\prime}$ x $8.40^{\prime}$ region covered by
the broad-band filters. Four of these sources have no reported detection in
previous studies of the region. We find that the source previously identified
as the near-IR counter-part to the IRAS detected point-source (IRAS 05338-0624)
is not the brightest source in the wavelength region of the IRAS 12 \micron\
filter. We find instead that a nearby object (within the beam of IRAS and not
detected at near-IR wavelengths) outshines all others sources in the area by a
factor of $\sim$2. We submit that this source is likely to be the IRAS detected
point source. A comparison of the near-IR (J-H vs H-K) and mid-IR (J-K vs [6.7
um]-[14 um]) color-color plots shows only four sources with excess emission at
near-IR wavelengths, but atleast 85% of all sources show excess emission at
mid-IR wavelengths. The CVF spectra suggest a range of evolutionary status in
the program stars ranging from embedded YSOs to the young disks. When combined
with optical and near-IR age estimates, these results show active current
star-formation in the region that has been on-going for at least 2 Myr.


title:
JETGET - An analysis and visualization tool for (magneto-)hydrodynamic
  jet simulations

abstract:
  In simulations of (magnetized-)fluid dynamics in physics and astrophysics,
the visualization techniques are so frequently applied to analyse data that
they have become a fundamental part of the research. Data produced is often a
multi-dimensional set with several physical quantities, that are usually
complex to manage and analyse. JETGET is a visualization and analysis tool we
developed for accessing data stored in Hierarchical Data Format (HDF) and ASCII
files. Although JETGET has been optimized to handle data output from jet
simulations using the Zeus code from NCSA, it is also capable of analysing
other data output from simulations using other codes. JETGET can select
variables from the data files, render both two- and three-dimensional graphics
and analyse and plot important physical quantities. Graphics can be saved in
encapsulated Postscript, JPEG, VRML or saved into an MPEG for later
visualization and/or presentations. An example of use of JETGET in analysing a
3-dimensional simulation of jets emanating from accretion disks surrounding a
protostar is shown. The strength of JETGET in extracting the physics underlying
such phenomena is demonstrated as well as its capabilities in visualizing the
3-dimensional features of the simulated magneto-hydrodynamic jets. The JETGET
tool is written in Interactive Data Language (IDL) and uses a graphical user
interface to manipulate the data. The tool was developed on a LINUX platform
and can be run on any platform that supports IDL. JETGET can be downloaded
(including more information about its utilities) from
http://www.capca.ucalgary.ca/software.


title:
From the Skyrme model to hypothetical Skyrmion stars: Astrophysical
  implications

abstract:
  We discuss the Skyrme model for strong interactions and the concept of a
Skyrmion fluid. The corresponding compact objects, namely Skyrmion stars,
constructed from the equation of state describing such a fluid are presented
and compared to models of neutron stars based on modern equation of states. We
suggest plausible Skyrmion star candidates in the 4U 1636-53 and 4U 1820-30 low
mass X-ray binary systems where the suggested masses of the accreting compact
companion (\sim 2.0M_{\odot}) remain a challenge for neutron star models.


title:
Time-dependence in Relativistic Collisionless Shocks: Theory of the
  Variable "Wisps" in the Crab Nebula

abstract:
  We describe results from time-dependent numerical modeling of the
collisionless reverse shock terminating the pulsar wind in the Crab Nebula. We
treat the upstream relativistic wind as composed of ions and electron-positron
plasma embedded in a toroidal magnetic field, flowing radially outward from the
pulsar in a sector around the rotational equator. The relativistic cyclotron
instability of the ion gyrational orbit downstream of the leading shock in the
electron-positron pairs launches outward propagating magnetosonic waves.
Because of the fresh supply of ions crossing the shock, this time-dependent
process achieves a limit-cycle, in which the waves are launched with
periodicity on the order of the ion Larmor time. Compressions in the magnetic
field and pair density associated with these waves, as well as their
propagation speed, semi-quantitatively reproduce the behavior of the wisp and
ring features described in recent observations obtained using the Hubble Space
Telescope and the Chandra X-Ray Observatory. By selecting the parameters of the
ion orbits to fit the spatial separation of the wisps, we predict the period of
time variability of the wisps that is consistent with the data. When coupled
with a mechanism for non-thermal acceleration of the pairs, the compressions in
the magnetic field and plasma density associated with the optical wisp
structure naturally account for the location of X-ray features in the Crab. We
also discuss the origin of the high energy ions and their acceleration in the
equatorial current sheet of the pulsar wind.


title: Correction of UBV photometry for emission lines

abstract:
  We investigated the effect on the U, B, V magnitudes of the removal of the
emission lines from the spectra of some symbiotic stars and novae during their
nebular phases. We approached this problem by a precise reconstruction of the
composite UV/optical continuum and the line spectrum. Corrections DU, DB, DV
are determined from the ratio of fluxes with and without emission lines. Here
we demonstrate this effect on the case of the symbiotic nova V1016 Cyg during
its nebular phase. We find that about 68, 78 and 66 per-cent of the observed
flux in the U, B and V filters is radiated in the emission lines. The effect
should be taken into account before using the observed color indices of
emission-line objects for diagnosis of their radiation in the continumm.


title:
Observational studies of Cataclysmic Variable evolution: Of samples,
  biases and surprises

abstract:
  I present brief status reports on three large observational projects that are
designed to test our current understanding of the evolution of cataclysmic
variables (CVs): The spectroscopic selection of new CVs in the Hamburg Quasar
Survey, the search for pre-CVs based on Sloan colours and UK Schmidt/6dF
multiobject spectroscopy, and the identification of CVs that descended from
supersoft X-ray binaries using a HST/STIS far-ultraviolet spectroscopic survey.


title: Photometric structure of the peculiar galaxy ESO 235-G58

abstract:
  We present the near-infrared and optical properties of the peculiar galaxy
ESO 235-G58, which resembles a late-type ringed barred spiral seen close to
face-on. However, the apparent bar of ESO 235-G58 is in reality an edge-on disk
galaxy of relatively low luminosity. We have analyzed the light and color
distributions of ESO 235-G58 in the NIR and optical bands and compared them
with the typical properties observed for other morphological galaxy types,
including polar ring galaxies. Similar properties are observed for ESO 235-G58,
polar ring galaxies, and spiral galaxies, which leads us to conclude that this
peculiar system is a polar-ring-related galaxy, characterized by a low inclined
ring/disk structure, as pointed out by Buta & Crocker in an earlier study,
rather than a barred galaxy.


title:
Timing and spectral studies of the transient X-ray pulsar EXO
  053109-6609.2 with ASCA and Beppo-SAX

abstract:
  We report timing and spectral properties of the transient Be X-ray pulsar EXO
053109--6609.2 studied using observations made with the ASCA and BeppoSAX
observatories. Though there must have been at least one spin-down episode of
the pulsar since its discovery, the new pulse period measurements show a
monotonic spin-up trend since 1996. The pulse profile is found to have marginal
energy dependence. There is also evidence for strong luminosity dependence of
the pulse profile, a single peaked profile at low luminosity that changes to a
double peaked profile at high luminosity. This suggests a change in the
accretion pattern at certain luminosity level. The X-ray spectrum is found to
consist of a simple power-law with photon index in the range of 0.4--0.8. At
high intensity level the spectrum also shows presence of weak iron emission
line.


title: Radio, optical and infrared observations of CLASS B0128+437

abstract:
  We present new observations of the gravitational lens system CLASS B0128+437.
HST observations detect a very faint, extended object in I-band with no
emission from the lensed images visible; no detection at all is made in V-band.
The lens system is detected with much higher signal to noise with UKIRT in
K-band, but the resolution is not sufficient to allow the lensed images and the
lens galaxy to be separated. A careful astrometric calibration, however,
suggests that the peak of the infrared emission corresponds to the two merging
images A and B and therefore that the lensed images dominate at infrared
wavelengths. The new radio data consist of VLBI radio images at three
frequencies, 2.3, 5 and 8.4GHz, made with the VLBA and the 100-m Effelsberg
telescope. The lensed source consists of three well-defined sub-components
embedded in a more extended jet. Due to the fact that the sub-components have
different spectral indices it is possible to determine which part of each image
corresponds to the same source sub-component. Our main finding is that one of
the images, B, looks very different to the others, there being no obvious
division into separate sub-components and the image being apparently both
broader and smoother. This is a consequence we believe of scatter-broadening in
the ISM of the lensing galaxy. The large number of multiply-imaged source
sub-components also provide an abundance of modelling constraints and we have
attempted to fit an SIE+external shear model to the data, as well as utilising
the novel method of Evans & Witt. It proves difficult in both cases, however,
to obtain a satisfactory fit which strongly suggests the presence of
sub-structure in the mass distribution of the lensing galaxy, perhaps of the
kind that is predicted by CDM theories of structure formation.


title: Cosmological perturbation theory

abstract:
  This is a review on cosmological perturbation theory. After an introduction,
it presents the problem of gauge transformation. Gauge invariant variables are
introduced and the Einstein and conservation equations are written in terms of
these variables. Some examples, especially perfect fluids and scalar fields are
presented in detail. The generation of perturbations during inflation is
studied. Lightlike geodesics and their relevance for CMB anisotropies are
briefly discussed. Perturbation theory in braneworlds is also introduced.


title: Lane-Emden Equation: perturbation method

abstract:
  The perturbation method is applied to numerical solution of the Lane-Emden
Equation of arbitrary index n, and the global parameters of polytropes are
found as function of polytropic index n.


title:
Observations of Abell 4059 with Chandra, HST and VLA: unraveling a
  complex cluster/radio-galaxy interaction

abstract:
  (abridged) We present a detailed reanalysis of the Chandra data for the
galaxy cluster Abell 4059 and its central radio galaxy, PKS2354-35. We also
present new 1.4GHz and 4.7GHz CnB-array radio data from the Very Large Array
(VLA), as well as a short archival WFPC2 image from the Hubble Space Telescope.
The presence of a strong interaction between this radio galaxy and the
intracluster medium (ICM) was suggested by Huang & Sarazin (1998) on the basis
of a short observation by the High Resolution Imager on ROSAT, and confirmed in
our preliminary analysis of the Chandra/ACIS-S data. In particular, X-ray
imaging clearly shows two cavities within the ICM that are approximately
aligned with the radio-galaxy axis. However, using our new radio maps we fail
to find a detailed correspondence between the 1 arcmin scale radio-lobes and
the ICM cavities. This suggests that the cavities are ``ghosts'' of a previous
burst of powerful activity by PKS 2354-35. We also examine the nature of the
central asymmetric ridge (or bar) of X-ray emission extending for 30kpc
south-west of the cluster center that has been noted in these previous
analyzes. We find the ridge to be denser and cooler than, but probably in
pressure balance with, its surroundings. The thermal evolution of this
structure seems to be dominated by radiative cooling, possibly enhanced by the
radio-galaxy ICM interaction. We discuss several possible models for the
formation of this SW ridge and find none of them to be entirely satisfactory.