title: TeV signatures of compact UHECR accelerators

abstract:
  We study numerically particle acceleration by the electric field induced near
the horizon of a rotating supermassive (M \sim 10^9-10^{10} M_{\odot}) black
hole embedded in the magnetic field B. We find that acceleration of protons to
energy E > 10^{20} eV is possible only at extreme values of M and B. We also
find that the acceleration is very inefficient and is accompanied by a broad
band MeV-TeV radiation whose total power exceeds at least by a factor of 1000
the total power emitted in ultra-high energy cosmic rays (UHECR). This implies
that if O(10) nearby quasar remnants were sources of proton events with energy
E > 10^{20} eV, then each quasar remnant would overshine e.g. the Crab nebula
by more than two orders of magnitude in the TeV energy band. Recent TeV
observations exclude this possibility. A model in which O(100) sources are
situated at 100-1000 Mpc is not ruled out and can be experimentally tested by
present TeV gamma-ray telescopes. Such a model can explain the observed UHECR
flux at moderate energies E \sim (4-5) 10^{19} eV.


title: EXITE2 Observation of the SIGMA Source GRS 1227+025

abstract:
  We report the EXITE2 hard X-ray imaging of the sky around 3C273. A 2h
observation on May 8, 1997, shows a $\sim$260 mCrab source detected at
$\sim4\sigma$ in each of two bands (50-70 and 70-93 keV) and located $\sim$30'
from 3C273 and consistent in position with the SIGMA source GRS1227+025. The
EXITE2 spectrum is consistent with a power law with photon index 3 and large
low energy absorption, as indicated by the GRANAT/SIGMA results. No source was
detected in more sensitive followup EXITE2 observations in 2000 and 2001 with
3$\sigma$ upper limits of 190 and 65 mCrab, respectively. Comparison with the
flux detected by SIGMA shows the source to be highly variable, suggesting it
may be non-thermal and beamed and thus the first example of a ``type 2''
(absorbed) Blazar. Alternatively it might be (an unprecedented) very highly
absorbed binary system undergoing accretion disk instability outbursts,
possibly either a magnetic CV, or a black hole X-ray nova.


title: Microquasars

abstract:
  I partially review our current knowledge on microquasars, making special
emphasis on radio interferometric observations, and I comment on emerging
trends in this field of astrophysics.


title: A portable modeler of lensed quasars

abstract:
  We introduce and implement two novel ideas for modeling lensed quasars. The
first idea is to require different lenses to agree about H_0. This means that
some models for one lens can be ruled out by data on a different lens. We
explain using two worked examples. One example models 1115+080, 1608+656
(time-delay quads) and 1933+503 (a prospective time-delay system) all together,
yielding time-delay predictions for the third lens and a 90%-confidence
estimate of 1/H_0=14.6_{-1.7}^{+9.4} Gyr (H_0=67_{-26}^{+9} km/s/Mpc) assuming
Omega_M=0.3, Omega_Lambda=0.7. The other example models the time-delay doubles
1520+530, 1600+434, 1830-211, and 2149-275, which gives
1/H_0=14.5_{-1.5}^{+3.3} Gyr (H_0=67_{-13}^{+8} km/s/Mpc). Our second idea is
to write the whole modeling software as a highly interactive Java applet, which
can be used both for coarse-grained results inside a browser and for
fine-grained results on a workstation. Several obstacles come up in trying to
implement a numerically-intensive method thus, but we overcome them.


title: Isolated Neutron Stars

abstract:
  This is a review of X-ray emission from all types of isolated neutron stars,
with an emphasis on rotation-powered pulsars. Topics include magnetospheric and
thermal emission, as well as pulsar wind nebulae.


title:
Tools for Identifying Spurious Luminosity Offsets in Tully-Fisher
  Studies: Application at Low Redshift and Implications for High Redshift

abstract:
  Studies of high-redshift galaxies usually interpret offsets from the Tully-
Fisher (TF) relation as luminosity evolution. However, apparent luminosity
offsets may actually reflect rotation curve anomalies such as strong
asymmetries or radial truncation, due to galaxy interactions or low S/N data.
Here we analyze emission-line rotation curves from two low-z samples: the Close
Pairs Survey, which contains many interacting galaxies, and the Nearby Field
Galaxy Survey (NFGS), which represents the general galaxy population. In the
spirit of high-z samples, these surveys reflect the natural diversity of
emission-line galaxies, including peculiar and early-type morphologies. We
adopt objective criteria to identify severe kinematic anomalies. In the Close
Pairs Survey, TF offsets associated with such anomalies collectively resemble
the ``differential luminosity evolution'' claimed in some high-z studies, with
larger offsets at lower luminosities. With anomalous galaxies rejected,
however, the TF relations for the two surveys are quite similar. Furthermore,
the two surveys follow similar relations between color and TF residuals, with
the Pairs Survey relation extending to bluer colors and brighter TF residuals.
Strong outliers from this relation are nearly always kinematically anomalous.
Thus the color-TF residual relation can serve as a powerful tool for separating
reliable luminosity offsets from offsets associated with kinematic anomalies.
We reanalyze high-z TF data from the FORS Deep Field and find: (1) overall
luminosity evolution of ~0.3 mag; (2) strong slope evolution driven by
kinematically anomalous galaxies, which show TF offsets of up to ~2 mag at low
luminosities; and (3) an additional zero-point offset of ~0.2 mag linked to
anomalous galaxies.


title:
Shaping the Kuiper belt size spectrum by shattering large but
  strengthless bodies

abstract:
  The observed size distribution of Kuiper belt objects (KBOs)--small icy and
rocky solar system bodies orbiting beyond Neptune--is well described by a power
law at large KBO sizes. However, recent work by Bernstein et al. (2003)
indicates that the size spectrum breaks and becomes shallower for KBOs smaller
than about 70 km in size. Here we show that we expect such a break at KBO
radius ~40 km since destructive collisions are frequent for smaller KBOs.
Specifically, we assume that KBOs are rubble piles with low material strength
rather than solid monoliths. This gives a power-law slope q~3 where the number
N(r) of KBOs larger than a size r is given by $N(r) \propto r^{1-q}$; the break
location follows from this slope through a self-consistent calculation. The
existence of this break, the break's location, and the power-law slope we
expect below the break are consistent with the findings of Bernstein et al.
(2003). The agreement with observations indicates that KBOs are effectively
strengthless rubble piles.


title: A Deep Chandra Observation of the Distant Galaxy Cluster MS1137.5+6625

abstract:
  We present results from a deep Chandra observation of MS1137.5+66, a distant
(z=0.783) and massive cluster of galaxies. Only a few similarly massive
clusters are currently known at such high redshifts; accordingly, this
observation provides much-needed information on the dynamical state of these
rare systems. The cluster appears both regular and symmetric in the X-ray
image. However, our analysis of the spectral and spatial X-ray data in
conjunction with interferometric Sunyaev-Zel'dovich effect data and published
deep optical imaging suggests the cluster has a fairly complex structure. The
angular diameter distance we calculate from the Chandra and Sunyaev-Zel'dovich
effect data assuming an isothermal, spherically symmetric cluster implies a low
value for the Hubble constant for which we explore possible explanations.


title:
The X-Ray Derived Cosmological Star Formation History and the Galaxy
  X-Ray Luminosity Functions in the Chandra Deep Fields North and South

abstract:
  The cosmological star formation rate in the combined Chandra Deep Fields
North and South is derived from our X-Ray Luminosity Function for Galaxies in
these Deep Fields. Mild evolution is seen up to redshift order unity with SFR ~
(1 + z)^{2.7}. This is the first directly observed normal star-forming galaxy
X-ray luminosity function (XLF) at cosmologically interesting redshifts (z>0).
This provides the most direct measure yet of the X-ray derived cosmic
star-formation history of the Universe. We make use of Bayesian statistical
methods to classify the galaxies and the two types of AGN, finding the most
useful discriminators to be the X-ray luminosity, X-ray hardness ratio, and
X-ray to optical flux ratio. There is some residual AGN contamination in the
sample at the bright end of the luminosity function. Incompleteness slightly
flattens the XLF at the faint end of the luminosity function. The XLF has a
lognormal distribution and agrees well with the radio and infrared luminosity
functions. However, the XLF does not agree with the Schechter luminosity
function for the H-alpha LF indicating that additional and different physical
processes may be involved in the establishment of the lognormal form of the
XLF. The agreement of our star formation history points with the other star
formation determinations in different wavebands (IR, Radio, H-alpha) gives an
interesting constraint on the IMF, and X-rays may be measuring directly the
binary star formation history of the Universe. X-ray studies will continue to
be useful for probing the star formation history of the universe by avoiding
problems of obscuration. Star formation may therefore be measured in more
detail by deep surveys with future x-ray missions.


title:
Photometry of symbiotic stars XI. EG And, Z And, BF Cyg, CH Cyg, CI Cyg,
  V1329 Cyg, TX CVn, AG Dra, RW Hya, QW Sge, IV Vir and the LMXB V934 Her

abstract:
  We present new photometric observations of EG And, Z And, BF Cyg, CH Cyg, CI
Cyg, V1329 Cyg, TX CVn, AG Dra, RW Hya, AR Pav, AG Peg, AX Per, QW Sge, IV Vir
and the peculiar M giant V934 Her. The current issue gathers observations of
these objects to December 2003.


title:
Motion and Properties of Nuclear Radio Components in Seyfert Galaxies
  Seen with VLBI

abstract:
  We report EVN, MERLIN and VLBA observations at 18 cm, 6 cm and 3.6 cm of the
Seyfert galaxies NGC 7674, NGC 5506, NGC 2110 and Mrk 1210 to study their
structure and proper motions on pc scales and to add some constraints on the
many possible causes of the radio-quietness of Seyferts. The component
configurations in NGC 7674 and NGC 2110 are simple, linear structures, whereas
the configurations in NGC 5506 and Mrk 1210 have multiple components with no
clear axis of symmetry. We suggest that NGC 7674 is a low-luminosity compact
symmetric object. Comparing the images at different epochs, we find a proper
motion in NGC 7674 of (0.92+-0.07) c between the two central components
separated by 282 pc and, in NGC 5506, we find a 3 sigma upper limit of 0.50 c
for the components separated by 3.8 pc. Our results confirm and extend earlier
work showing that the outward motion of radio components in Seyfert galaxies is
non-relativistic on pc scales. We briefly discuss whether this non-relativistic
motion is intrinsic to the jet-formation process or results from deceleration
of an initially relativistic jet by interaction with the pc or sub-pc scale
interstellar medium. We combined our sample with a list compiled from the
literature of VLBI observations made of Seyfert galaxies, and found that most
Seyfert nuclei have at least one flat-spectrum component on the VLBI scale,
which was not seen in the spectral indices measured at arcsec resolution. We
found also that the bimodal alignment of pc and kpc radio structures displayed
by radio galaxies and quasars is not displayed by this sample of Seyferts,
which shows a uniform distribution of misalignment between 0 deg and 90 deg.
The frequent misalignment could result from jet precession or from deflection
of the jet by interaction with gas in the interstellar medium.


title: Neutron Star Cooling

abstract:
  Observation of cooling neutron stars can potentially provide information
about the states of matter at supernuclear densities. We review physical
properties important for cooling such as neutrino emission processes and
superfluidity in the stellar interior, surface envelopes of light elements due
to accretion of matter and strong surface magnetic fields. The neutrino
processes include the modified Urca process, and the direct Urca process for
nucleons and exotic states of matter such as a pion condensate, kaon
condensate, or quark matter. The dependence of theoretical cooling curves on
physical input and observations of thermal radiation from isolated neutron
stars are described. The comparison of observation and theory leads to a
unified interpretation in terms of three characteristic types of neutron stars:
high-mass stars which cool primarily by some version of the direct Urca
process; low-mass stars, which cool via slower processes; and medium-mass
stars, which have an intermediate behavior. The related problem of thermal
states of transiently accreting neutron stars with deep crustal burning of
accreted matter is discussed in connection with observations of soft X-ray
transients.


title: On the Kinematics of Tidal Debris from Omega Cen's Progenitor Galaxy

abstract:
  The kinematic properties of tidal debris from an orbiting Galactic satellite
is presented, on the assumption that its central part once contained the most
massive Galactic globular cluster, omega Cen. We simulate dynamical evolution
of a satellite galaxy that follows the present-day and likely past orbits of
omega Cen and analyze the kinematic nature of their tidal debris and randomly
generated Galactic stars comprising spheroidal halo and flat disk components.
It is found that the debris stars show a retrograde rotation at about -100
km/s, which may accord with a recently discovered stellar stream at radial
velocity of about 300 km/s towards the Galactic longitude of about 270 degree.
These stars also contribute, only in part, to a reported retrograde motion of
the outer halo in the North Galactic Pole direction, without significantly
modifying local halo kinematics near the Sun. The prospects for future debris
searches and the implications for the early evolution of the Galaxy are briefly
presented.


title:
Period-color and amplitude-color relations in classical Cepheid
  variables

abstract:
  In this paper we analyze the behavior of Galactic, LMC and SMC Cepheids in
terms of period-color (PC) and amplitude-color (AC) diagrams at the phases of
maximum, mean and minimum light. We find very different behavior between
Galactic and Magellanic Cloud Cepheids. Motivated by the recent report of a
break in LMC PC relations at 10 days (Tammann et al. 2002), we use the
F-statistical test to examine the PC relations at mean light in these three
galaxies. The results of the F-test support the existence of the a break in the
LMC PC(mean) relation, but not in the Galactic or SMC PC(mean) relations.
Furthermore, the LMC Cepheids also show a break at minimum light, which is not
seen in the Galactic and SMC Cepheids. We further discuss the effect on the
period-luminosity relations in the LMC due to the break in the PC(mean)
relation.


title: Gas flow in close binary star systems

abstract:
  We first present a summary of our numerical work on accretion discs in close
binary systems. Our recent studies on numerical simulations of the surface flow
on the mass-losing star in a close binary star is then reviewed.


title: Constraints on a Putative Pulsar in SN 1987A

abstract:
  We assume that all the energy loss of the putative pulsar in SN 1987A would
contribute to the luminosity of the remnant, which acts like a bolometer. The
bolometric luminosity of SN 1987A provides an upper bound on the pulsar's rate
of energy loss. An isolated pulsar spinning down by magnetic dipole radiation
alone, with initial rotation periods of 10-30 ms, as extrapolated for galactic
young pulsars, can have a luminosity below the bolometric bound if either the
magnetic field is weak, B $\sim$ 10$^{9}-10^{10}$ G, or if it is so strong that
the pulsar luminosity decays rapidly, B $\sim$ 10$^{16}$ G.


title: Colliding molecular clouds in head-on galaxy collisions

abstract:
  We present further observations of molecular gas in head-on collisions of
spiral galaxies, this time of the CO(J=1-0) and CO(J=2-1) lines in the UGC 813
-- UGC 816 system. UGC 813/6 are only the second known example of head-on
spiral-spiral collisions, the first example being the UGC 12914/5 pair. Strong
CO emission is present in the bridge between UGC 813 and 816, unassociated with
stellar emission, just as in UGC 12914/5. The CO emission from the UGC 813/6
bridge, not counting the emission from the galaxies themselves, is at least
that of the entire Milky Way. Collisions of gas-rich spirals are really
collisions between the interstellar media (ISMs) of the galaxies. We show that
collisions between molecular clouds bring H2 into the bridge region. Although
the dense clouds are ionized by the collisions, they cool and recombine very
quickly and become molecular again even before the galactic disks separate.
Because the clouds acquire an intermediate velocity post-collision, they are
left in the bridge between the separating galaxies. The star formation
efficiency appears low in the molecular clouds in the bridges. We speculate
that the pre-stellar cores in the molecular clouds may expand during the cloud
collisions, thus retarding future star formation. Because the ISM-ISM
collisions discussed here require a very small impact parameter, they are rare
among field spirals. In clusters, however, these collisions should be an
important means of ejecting enriched gas from the inner parts of spirals.


title: Anomalous Flux Ratios in Gravitational Lenses: For or Against CDM?

abstract:
  We review the evidence for substructures from the anomalous flux ratios in
gravitational lenses. Using high-resolution numerical simulations, we show that
at typical image positions, the fraction of surface mass density in
substructures is <~ 0.5% with mass above 10^{-4} virial masses in the
``concordance'' LCDM cosmology. Substructures outside the virial radius (but
projected at typical lens image positions) only increase the fraction
moderately. Several effects, in particular baryonic settling and the
requirement of compactness, may further decrease the predictions by a factor of
few. The predicted fraction with appropriate properties thus appears to be
lower than that required by lensing, although both are still uncertain. More
speculative substructures such as massive black holes (M ~ 10^5-10^6 solar
masses) in the halo may offer viable alternatives.


title:
Local Axisymmetric Diffusive Stability of Weakly-Magnetized,
  Differentially-Rotating, Stratified Fluids

abstract:
  We study the local stability of stratified, differentially-rotating fluids to
axisymmetric perturbations in the presence of a weak magnetic field and of
finite resistivity, viscosity and heat conductivity. This is a generalization
of the Goldreich-Schubert-Fricke (GSF) double-diffusive analysis to the
magnetized and resistive, triple-diffusive case. Our fifth-order dispersion
relation admits a novel branch which describes a magnetized version of
multi-diffusive modes. We derive necessary conditions for axisymmetric
stability in the inviscid and perfect-conductor (double-diffusive) limits. In
each case, rotation must be constant on cylinders and angular velocity must not
decrease with distance from the rotation axis for stability, irrespective of
the relative strength of viscous, resistive and heat diffusion. Therefore, in
both double-diffusive limits, solid body rotation marginally satisfies our
stability criteria. The role of weak magnetic fields is essential to reach
these conclusions. The triple-diffusive situation is more complex, and its
stability criteria are not easily stated. Numerical analysis of our general
dispersion relation confirms our analytic double-diffusive criteria, but also
shows that an unstable double-diffusive situation can be significantly
stabilized by the addition of a third, ostensibly weaker, diffusion process. We
describe a numerical application to the Sun's upper radiative zone and
establish that it would be subject to unstable multi-diffusive modes if
moderate or strong radial gradients of angular velocity were present.


title:
A Two-Dimensional Hydrostatically Equilibrium Atmosphere of a Neutron
  Star with Given Differential Rotation

abstract:
  An analytic solution has been found in the Roche approximation for the
axially symmetric structure of a hydrostatically equilibrium atmosphere of a
neutron star produced by collapse. A hydrodynamic (quasione-dimensional) model
for the collapse of a rotating iron core in a massive star gives rise to a
heterogeneous rotating protoneutron star with an extended atmosphere composed
of matter from the outer part of the iron core with differential rotation
(Imshennik and Nadyozhin, 1992). The equation of state of a completely
degenerate iron gas with an arbitrary degree of relativity is taken for the
atmospheric matter. We construct a family of toroidal model atmospheres with
total masses $M \approx 0.1 \div 0.2 M_{\odot}$ and total angular momenta $J
\approx (1 \div 5.5) \cdot 10^{49} erg \cdot s$, which are acceptable for the
outer part of the collapsed iron core, in accordance with the hydrodynamic
model, as a function of constant parameters $\omega_{0} and r_{0}$ of the
specified differential rotation law $\Omega =
\omega_{0}\exp{\Big[-\frac{(r\sin{\Theta})^{2}}{r_{0}^{2}}\Big]}$ in spherical
coordinates. The assumed rotation law is also qualitatively consistent with the
hydrodynamic model for the collapse of an iron core.


title:
Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic
  Background Light with GLAST

abstract:
  Gamma rays with energy above 10 GeV interact with optical-UV photons
resulting in pair production. Therefore, a large sample of high redshift
sources of these gamma rays can be used to probe the extragalactic background
starlight (EBL) by examining the redshift dependence of the attenuation of the
flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope,
will have the unique capability to detect thousands of gamma-ray blazars to
redshifts of at least z=4, with sufficient angular resolution to allow
identification of a large fraction of their optical counterparts. By combining
established models of the gamma-ray blazar luminosity function, two different
calculations of the high energy gamma-ray opacity due to EBL absorption, and
the expected GLAST instrument performance to produce simulated fluxes and
redshifts for the blazars that GLAST would detect, we demonstrate that these
gamma-ray blazars have the potential to be a highly effective probe of the
optical-UV EBL.


title:
The Possibility of Emersion of the Outer Layers in a Massive Star
  Simultaneously with Iron-Core Collapse: A Hydrodynamic Model

abstract:
  We analyze the behavior of the outer envelope in a massive star during and
after the collapse of its iron core into a protoneutron star (PNS) in terms of
the equations of one-dimensional spherically symmetric ideal hydrodynamics. The
profiles obtained in the studies of the evolution of massive stars up to the
final stages of their existence, immediately before a supernova explosion
(Boyes et al. 1999), are used as the initial data for the distribution of
thermodynamic quantities in the envelope.We use a complex equation of state for
matter with allowances made for arbitrary electron degeneracy and relativity,
the appearance of electron-positron pairs, the presence of radiation, and the
possibility of iron nuclei dissociating into free nucleons and helium nuclei.
We performed calculations with the help of a numerical scheme based on
Godunov's method. These calculations allowed us to ascertain whether the
emersion of the outer envelope in a massive star is possible through the
following two mechanisms: first, the decrease in the gravitational mass of the
central PNS through neutrino-signal emission and, second, the effect of hot
nucleon bubbles, which are most likely formed in the PNS corona, on the
envelope emersion. We show that the second mechanism is highly efficient in the
range of acceptable masses of the nucleon bubbles ($\leq 0.01M_\odot$)
simulated in our hydrodynamic calculations in a rough, spherically symmetric
approximation.


title: An X-ray review of MS1054-0321: hot or not?

abstract:
  XMM-Newton observations are presented for the z=0.83 cluster of galaxies
MS1054-0321, the highest redshift cluster in the Einstein Extended Medium
Sensitivity Survey (EMSS). The temperature inferred by the XMM-Newton data,
T=7.2 (+0.7, -0.6) keV, is much lower than the temperature previously reported
from ASCA data, T=12.3 (+3.1, -2.2) keV (Donahue et al. 1998), and a little
lower than the Chandra temperature, T=10.4(+1.7, -1.5) keV, determined by
Jeltema et al. 2001. The discrepancy between the newly derived temperature and
the previously derived temperatures is discussed in detail. If one allows the
column density to be a free parameter, then the best fit temperature becomes
T=8.6 (+1.2, -1.1) keV, and the best fit column density becomes N_(H)=1.33
(+0.15 -0.14) x 10^20 atoms/cm^2. The iron line is well detected in the
XMM-Newton spectrum with a value for the abundance of Z=0.33 (+0.19 -0.18)
Zsol, in very good agreement with previous determinations. The derived XMM
X-ray luminosity for the overall cluster in the 2-10 keV energy band is
L_X=(3.81 +/- 0.19) x 10^44 h^-2 erg s^-1 while the bolometric luminosity is
L_BOL=(8.05+/-0.40) x 10^44 h^-2 erg s^-1. The XMM-Newton data confirm the
substructure in the cluster X-ray morphology already seen by ROSAT and in much
more detail by Chandra. The central weak lensing clump is coincident with the
main cluster component and has a temperature T=8.1 (+1.3, -1.2) keV. The
western weak lensing clump coincides with the western X-ray component which is
much cooler with a temperature T=5.6 (+0.8, -0.6)$ keV. Given the newly
determined temperature, MS1054-0321 is no longer amongst the hottest clusters
known.


title: Properties of groups of galaxies in the vicinity of massive clusters

abstract:
  This work analyses the properties of groups of galaxies in the surroundings
of clusters. On the basis of a very large public Virgo Consortium Simulation,
we identified systems of galaxies in a wide range of masses. Systems with
masses greater than $ M_{cut}= 4 \times 10^{14} M_{\odot} h^{-1} $ are
considered "host", whereas smaller systems are taken as groups. Our results
show that groups properties are affected by the proximity of massive hosts.
Physical properties such as velocity dispersion, internal energy ($E$) and
virial radius, show an increment, whereas the mean density decreases as the
host-group distance is smaller. By analysing groups with different properties,
we find that the low mass and the weakly bounded ($E > 0$) subsamples, are
strongly affected by the presence of the host; on the other hand, massive
groups and groups with $E < 0$ do not show dependence on the host-group
distance. Using a sample of groups identified in the final version of the 2dF
Galaxy Redshift Survey, we find a very similar velocity dispersion behaviour in
the observational data compared to results in the simulation. We also study the
dependence of the groups velocity dispersion on the host masses in both,
observations and simulation; finding that the larger is the host mass the
higher is the effect on its vicinity.


title: Far-IR spectroscopy towards Sagittarius B2

abstract:
  The far-IR is a unique wavelength range for Astrophysical studies, however,
it can only be fully sampled from space platforms. The fundamental rotational
transitions of light molecules, the high-J transitions of polyatomic species,
the bending modes of non-polar molecules, several atomic fine structure lines
and many frequencies blocked by the earth atmosphere can only be observed
between 50 and 200 um (6.0 and 1.5 THz). In this contribution we present the
far-IR spectrum of Sgr B2 at a resolution of ~35 km s^{-1}, the ``Rosetta
stone'' of ISO's far-IR spectra. We also discuss the perspectives of the far-IR
Astronomy in the context of the future telescopes under development.


title: The spacetime associated with galactic dark matter halos

abstract:
  We show how an adequate post--Newtonian generalization can be obtained for
Newtonian dark matter halos associated with an empiric density profile.
Applying this approach to halos that follow from the well known numerical
simulations of Navarro, Frenk and White (NFW), we derive all dynamical
variables and show that NFW halos approximatelly follow an ideal gas type of
equation of state which fits very well to a polytropic relation in the region
outside the core. This fact suggests that ``outer'' regions of NFW halos might
be related to equilibrium states in the non--extensive Statistical Mechanics
formalism proposed by Tsallis.


title: Relativistic Phenomena in Active Galactic Nuclei

abstract:
  The idea that the radio jets in AGN contain material in relativistic motion
is supported by many lines of observational evidence, including morphology,
brightness temperature estimated with interferometers and with intrinsic
variations, interstellar scintillations, X-rays, and superluminal motion. These
are largely independent, and taken together make an irrefutable case for
relativistic motion.


title:
Time Evolution of the Fine Structure Constant in a Two-Field
  Quintessence Model

abstract:
  We examine the variation of the fine structure constant in the context of a
two-field quintessence model. We find that, for solutions that lead to a
transient late period of accelerated expansion, it is possible to fit the data
arising from quasar spectra and comply with the bounds on the variation of
$\alpha$ from the Oklo reactor, meteorite analysis, atomic clock measurements,
Cosmic Microwave Background Radiation and Big Bang Nucleosynthesis. That is
more difficult if we consider solutions corresponding to a late period of
permanent accelerated expansion.


title: Velocity and spatial biases in CDM subhalo distributions

abstract:
  We present a statistical study of substructure within a sample of LCDM
clusters and galaxies simulated with up to 25 million particles. With thousands
of subhalos per object we can accurately measure their spatial clustering and
velocity distribution functions and compare these with observational data. The
substructure properties of galactic halos closely resembles those of galaxy
clusters with a small scatter in the mass and circular velocity functions. The
velocity distribution function is non-Maxwellian and flat topped with a
negative kurtosis of about -0.7. Within the virial radius the velocity bias
$b=\sigma_{\rm sub}/\sigma_{\rm DM}\sim 1.12 \pm 0.04$, increasing to b > 1.3
within the halo centers. Slow subhalos are much less common, due to physical
disruption by gravitational tides early in the merging history. This leads to a
spatially anti-biased subhalo distribution that is well fitted by a cored
isothermal. Observations of cluster galaxies do not show such biases which we
interpret as a limitation of pure dark matter simulations - we estimate that we
are missing half of the halo population which has been destroyed by physical
overmerging. High resolution hydrodynamical simulations are required to study
these issues further. If CDM is correct then the cluster galaxies must survive
the tidal field, perhaps due to baryonic inflow during elliptical galaxy
formation. Spirals can never exist near the cluster centers and the elliptical
galaxies there will have little remaining dark matter. This implies that the
morphology-density relation is set {\it before} the cluster forms, rather than
a subsequent transformation of disks to S0's by virtue of the cluster
environment.


title:
A Redshift Survey of Nearby Galaxy Groups: the Shape of the Mass Density
  Profile

abstract:
  We constrain the mass profile and orbital structure of nearby groups and
clusters of galaxies. Our method yields the joint probability distribution of
the density slope n, the velocity anisotropy beta, and the turnover radius r0
for these systems. The measurement technique does not use results from N-body
simulations as priors. We incorporate 2419 new redshifts in the fields of 41
systems of galaxies with z < 0.04. The new groups have median velocity
dispersion sigma=360 km/s. We also use 851 archived redshifts in the fields of
8 nearly relaxed clusters with z < 0.1. Within R < 2 r200, the data are
consistent with a single power law matter density distribution with slope n =
1.8-2.2 for systems with sigma < 470 km/s, and n = 1.6-2.0 for those with sigma
> 470 km/s (95% confidence). We show that a simple, scale-free phase space
distribution function f(E,L^2) ~ (-E)^(alpha-1/2) L^(-2 \beta) is consistent
with the data as long as the matter density has a cusp. Using this DF, matter
density profiles with constant density cores (n=0) are ruled out with better
than 99.7% confidence.


title:
The Probability Distribution of Binary Pulsar Coalescence Rate
  Estimates. II. Neutron Star-White Dwarf Binaries

abstract:
  We consider the statistics of pulsar binaries with white dwarf companions
(NS-WD). Using the statistical analysis method developed by Kim et al. (2003)
we calculate the Galactic coalescence rate of NS-WD binaries due to
gravitational-wave emission. We find that the most likely values for the total
Galactic coalescence rate (R_tot) of NS-WD binaries lie in the range 0.2--10
per Myr depending on different assumed pulsar population models. For our
reference model, we obtain R_tot=4.11_(-2.56)^(+5.25) per Myr at a 68%
statistical confidence level. These rate estimates are not corrected for pulsar
beaming and as such they are found to be about a factor of 20 smaller than the
Galactic coalescence rate estimates for double neutron star systems. Based on
our rate estimates, we calculate the gravitational-wave background due to
coalescing NS-WD binaries out to extragalactic distances within the frequency
band of the Laser Interferometer Space Antenna. We find the contribution from
NS-WD binaries to the gravitational-wave background to be negligible.


title:
Constraints on Off-Axis GRB Jets in Type Ibc Supernovae From Late-Time
  Radio Observations

abstract:
  It has been suggested that the peculiar properties of the luminous Type Ic
supernova SN 1998bw and its low-energy gamma-ray burst GRB 980425 may be
understood if they originated in a standard gamma-ray burst explosion viewed
far from the axis of the relativistic jet. In this scenario, strong radio
emission is predicted from the jet on a timescale 1 to 10 years after the
explosion as it decelerates and spreads into our line of sight. To test this
hypothesis we have carried out late-time radio observations of SN 1998bw at
$t=5.6$ years, yielding upper limits which are consistent with the continued
fading of the supernova. We find these limits to be consistent with an off-axis
jet only if the progenitor mass loss rate is $\dot{M}\lesssim 4 \times 10^{-7}$
M$_\odot$ yr$^{-1}$ (for a wind velocity $v_w=1000$ km s$^{-1}$) or the
fraction of the shock energy in magnetic fields is $\epsilon_B \lesssim
10^{-3}$. These values are low relative to those inferred for cosmological
GRBs. We combine the SN 1998bw measurements with existing observations for a
sample of 15 local Type Ibc supernovae to estimate that at most 6% produce
collimated, relativistic outflows.


title:
Internal shocks and the blazar sequence. Low and intermediate power BL
  Lac objects

abstract:
  We consider internal shocks as the main dissipation mechanism responsible for
the emission in blazars and show that it can satisfactorily account for the
properties of all blazars. In particular, we extend previous work (Spada et al.
2001) on powerful objects, to intermediate (BL Lac) and low power sources (Mkn
421), in order to reproduce the whole of the blazar sequence. The model
self-consistently treats the dynamics, spectral emission and its variability.
The key parameters driving the phenomenological sequence are the jet power and
the properties of the broad line region, which regulate the cooling efficiency
of the emitting particles and thus the shape of the spectral energy
distribution. By assuming that the remaining parameters are similar for all
objects it has been possible to reproduce the full range of the observed
spectral "states". A more detailed comparison of the variability properties
shows (for Mkn 421) a good agreement in the X-ray band, while in the optical
the simulated flux appears to be too variable. For BL Lac lags (~10 days) are
predicted between the gamma--rays and the infrared emission


title: Quasi-geometrical Optics Approximation in Gravitational Lensing

abstract:
  The gravitational lensing of gravitational waves should be treated in the
wave optics instead of the geometrical optics when the wave length $\lambda$ of
the gravitational waves is larger than the Schwarzschild radius of the lens
mass $M$. The wave optics is based on the diffraction integral which represents
the amplification of the wave amplitude by lensing. We study the asymptotic
expansion of the diffraction integral in the powers of the wave length
$\lambda$. The first term, arising from the short wavelength limit $\lambda \to
0$, corresponds to the geometrical optics limit. The second term, being of the
order of $\lambda/M$, is the leading correction term arising from the
diffraction effect. By analyzing this correction term, we find that (1) the
lensing magnification $\mu$ is modified to $\mu ~(1+\delta)$, where $\delta$ is
of the order of $(\lambda/M)^2$, and (2) if the lens has cuspy (or singular)
density profile at the center $\rho(r) \propto r^{-\alpha}$ ($0 < \alpha \leq
2$), the diffracted image is formed at the lens center with the magnification
$\mu \sim (\lambda/M)^{3-\alpha}$.


title:
A direct imaging search for wide (sub)stellar companions around rad-vel
  planet host stars

abstract:
  We present an overview of our ongoing systematic search for wide (sub)stellar
companions around the stars known to host rad-vel planets. By using a
relatively large field of view and going very deep our survey can find all
directly detectable stellar and brown dwarf companions (m>40 Mjup) within a
1000 AU orbit.


title:
Search for substellar companions using AO - first results obtained with
  NAOS-CONICA

abstract:
  We present first results of our NAOS-CONICA search for close substellar
companions around young nearby stars. This program was started only a few
months ago. We have obtained 1st epoch images of several targets which are
unpublished young stars (age<100 Myrs), hence ideal targets to look for
planetary companions. For one target star we could even take a 2nd epoch image.
By comparing both images we could look for co-moving companions of the target
star. Those data show clearly that the detection of planetary companions m <13
Mjup inward a saturn-like orbit (r<10 AU) is feasible with NAOS-CONICA and in
addition that the astrometric confirmation of those companions is doable with
only a few weeks of epoch difference.


title:
A search for wide (sub)stellar companions around extrasolar planet host
  stars

abstract:
  We present an overview of our ongoing systematic search for wide (sub)stellar
companions around the stars known to host rad-vel planets. By using a
relatively large field of view and going very deep, our survey can find all
directly detectable stellar and massive brown dwarf companions (m>40 Mjup)
within a 1000 AU orbit.


title:
The Existence of an Old Quasar at $z = 3.91$ and its Implications for
  $\Lambda(t)$ Deflationary Cosmologies

abstract:
  We investigate some observational constraints on decaying vacuum cosmologies
based on the recently discovered old high redshift quasar APM 08279+5255. This
object is located at $z = 3.91$ and has an estimated age of 2-3 Gyr. The class
of $\Lambda(t)$ cosmologies is characterized by a positive $\beta$ parameter
smaller than unity which quantifies the ratio between the vacuum and the total
energy density. Assuming the lower limit age (2 Gyr) and that the cold dark
matter contributes with $\Omega_{\rm M}=0.2$ we show that $\beta$ is
constrained to be $\ge 0.07$ while for an age of 3 Gyr and $\Omega_{\rm M}=0.4$
the $\beta$ parameter must be greater than 0.32. Our analysis includes closed,
flat and hyperbolic scenarios, and it strongly suggests that there is no age
crisis for this kind of $\Lambda(t)$ cosmologies. Lower limits to the redshift
quasar formation are also briefly discussed to the flat case. For $\Omega_{\rm
M}=0.4$ we found that the redshift formation is constrained by $z_{f}\ge 8.0$.


title:
The Large-Scale Magnetic Field Structure of Our Galaxy: Efficiently
  Deduced from Pulsar Rotation Measures

abstract:
  In this review, I will first introduce possible methods to probe the
large-scale magnetic fields in our Galaxy and discuss their limitations. The
magnetic fields in the Galactic halo, mainly revealed by the sky distribution
of rotation measures of extragalactic radio sources, probably have a global
structure of a twisted dipole field. The large-scale field structure in the
Galactic disk has been most efficiently deduced from pulsar rotation measures
(RMs). There has been a lot of progress since the 1980s when the magnetic field
in the local area of our Galaxy was first traced by a very small sample of
local pulsars. Now we have pulsars distributed in about one third of the whole
Galactic disk of the interstellar medium, which shows that the large-scale
magnetic fields go along the spiral arms and that the field directions reverse
from arm to arm. The RMs of newly discovered pulsars in the very inner Galaxy
have been used to show the coherent magnetic field in the Norma arm. The
magnetic fields in the Galactic disk most probably have a bisymmetric spiral
structure.


title: Discovery of very nearby ultracool dwarfs from DENIS

abstract:
  We report new spectroscopic results, obtained with UKIRT/CGS4, of a sample of
14 candidate ultracool dwarfs selected from the DENIS (Deep Near-Infrared
Survey of the Southern Sky) database. A further object, selected from the 2MASS
Second Incremental Release, was observed at a later epoch with the same
instrument. Six objects are already known in the literature; we re-derive their
properties. A further four prove to be very nearby (~10 pc) mid-to-late
L-dwarfs, three unknown hitherto, two of which are almost certainly substellar.
These findings increase the number of L-dwarfs known within ~10 pc by ~25%. The
remainder of the objects discussed here are early L or very late M-type dwarfs
lying between ~45 and 15 pc and are also new to the literature. Spectral types
have been derived by direct comparison with J-,H- and K- band spectra of known
template ultracool dwarfs given by Leggett et al.
(ftp://ftp.jach.hawaii.edu/pub/ukirt/skl/dL.spectra/) For the known objects, we
generally find agreement to within ~1 subclass with previously derived spectral
types. Distances are determined from the most recent M_J vs. spectral type
calibrations, and together with our derived proper motions yield kinematics for
most targets consistent with that expected for the disk population; for three
probable late M-dwarfs, membership of a dynamically older population is
postulated. The very nearby L-type objects discussed here are of great interest
for future studies of binarity and parallaxes.


title: 2MASS J05185995-2828372: Discovery of an Unresolved L/T Binary

abstract:
  We present the peculiar near-infrared spectrum of the newly discovered brown
dwarf 2MASS J05185995-2828372, identified in the Two Micron All-Sky Survey.
Features characteristic of both L and T dwarfs are present, namely strong
carbon monoxide absorption in K-band, strong methane absorption in J- and
H-bands, and red near-infrared colors. We consider several scenarios that could
produce these features and conclude that the object is most likely to be an
unresolved L/T binary system. We discuss how the estimated photometric
properties of this object are consistent with the observed J-band brightening
of brown dwarfs between late-L and early-T dwarfs, making detailed study of
this system an important probe of the L/T transition.


title:
Analysis of the Kamionkowski-Loeb method of reducing cosmic variance
  with CMB polarization

abstract:
  Part of the CMB polarization signal in the direction of galaxy clusters is
produced by Thomson scattering of the CMB temperature quadrupole. In principle
this allows measurement of the CMB power spectrum harmonic $C_2(z)$ with higher
accuracy (at $z>0$) than the cosmic variance limit imposed by sample variance
on one CMB sky. However the observed signals are statistically correlated if
the comoving separation between the clusters is small enough. Thus one cannot
reduce the sample variance by more than roughly the number of separate regions
available which produce uncorrelated signals, as first pointed out by
Kamionkowski and Loeb. In this paper we analyze in detail the procedure
outlined by Kamionkowski and Loeb, computing the correlation of the
polarization signals by considering the variation of the spherical harmonic
expansion coefficients of the temperature anisotropy on our past light cone. We
find that in fact the cosmic variance is not reducible below the single sky CMB
value using the cluster method. Thus this method is not likely to be of use for
reconstruction of the primordial power spectrum. However the method does yield
a measurement of $C_2$ as a function of redshift with increasing accuracy at
higher redshift, and thus potentially a probe of the mechanism which may have
suppressed the quadrupole. (abridged)


title:
NIR Luminosity Function of Galaxies in Close Major-Merger Pairs and Mass
  Dependence of Merger Rate

abstract:
  A sample of close major-merger pairs (projected separation ${\rm 5 \leq r
\leq 20 h^{-1}}$ kpc, ${\rm K_s}$ band magnitude difference $\delta {\rm K_s}
\leq 1$ mag) is selected from the matched 2MASS-2dFGRS catalog of Cole et al.
(2001). The pair primaries are brighter than ${\rm K_s} = 12.5$ mag. After
corrections for various biases, the comparison between counts in the paired
galaxy sample and counts in the parent sample shows that for the local `M*
galaxies' sampled by flux limited surveys, the fraction of galaxies in the
close major-merger pairs is 1.70$\pm 0.32%$. Using 38 paired galaxies in the
sample, a ${\rm K_s}$ band luminosity function (LF) is calculated. This is the
first unbiased LF for a sample of objectively defined interacting/merging
galaxies in the local universe, while all previously determined LFs of paired
galaxies are biased by mistreating paired galaxies as singles. A stellar mass
function (MF) is translated from the LF. Compared to the LF/MF of 2MASS
galaxies, a differential pair fraction function is derived. The results suggest
a trend in the sense that less massive galaxies may have lower chance to be
involved in close major-merger pairs than more massive galaxies. The algorithm
presented in this paper can be easily applied to much larger samples of 2MASS
galaxies with redshifts in near future.


title: Soft Gamma Repeaters and Anomalous X-ray Pulsars: Together Forever

abstract:
  I review of the observational properties of Soft Gamma Repeaters (SGRs) and
Anomalous X-ray Pulsars (AXPs), two unusual manifestations of neutron stars. I
summarize the reasoning for SGRs being "magnetars," neutron stars powered by
the decay of a very large magnetic field, and the now compelling evidence that
SGRs and AXPs are in fact members of the same source class, as predicted
uniquely by the magnetar model. I discuss some open issues in the magnetar
model, and the prospects for future work.


title: (Anomalous) X-ray Pulsars

abstract:
  We review the observational properties of the class of young neutron stars
known as "anomalous X-ray pulsars," emphasizing the tremendous progress that
has been made in recent years, and explain why these objects, like the "soft
gamma repeaters," are today thought to be young, isolated, ultrahigh magnetic
field neutron stars, or "magnetars."


title:
Limits on the time variation of the electromagnetic fine-structure
  constant in the low energy limit from absorption lines in the spectra of
  distant quasars

abstract:
  Most of the successful physical theories rely on the constancy of few
fundamental quantities (such as the speed of light, $c$, the fine-structure
constant, \alpha, the proton to electron mass ratio, \mu, etc), and
constraining the possible time variations of these fundamental quantities is an
important step toward a complete physical theory. Time variation of \alpha can
be accurately probed using absorption lines seen in the spectra of distant
quasars. Here, we present the results of a detailed many-multiplet analysis
performed on a new sample of Mg II systems observed in high quality quasar
spectra obtained using the Very Large Telescope. The weighted mean value of the
variation in \alpha derived from our analysis over the redshift range 0.4<z<2.3
is \Delta\alpha/\alpha = (-0.06+/-0.06) x 10^{-5}. The median redshift of our
sample (z=1.55) corresponds to a look-back time of 9.7 Gyr in the most favored
cosmological model today. This gives a 3\sigma limit, -2.5 x 10^{-16} yr^-1
<(\Delta\alpha/\alpha\Delta t) <+1.2x10^{-16} yr^-1, for the time variation of
\alpha, that forms the strongest constraint obtained based on high redshift
quasar absorption line systems.


title: Stability of accretion disk around rotating black holes

abstract:
  I discuss the stability of accretion disks when the black hole is considered
to be rotating. I show, how the fluid properties get changed for different
choices of angular momentum of black holes. I treat the problem in
pseudo-Newtonian approach with a suitable potential from Kerr geometry. When
the angular momentum of a black hole is considered to be significant, the valid
disk parameter region affects and a disk may become unstable. Also the
possibility of shock in an accretion disk around rotating black holes is
checked. When the black hole is chosen to be rotating, the sonic locations of
the accretion disk get shifted or disappear, making the disk unstable by means
of loosing entropy. To bring the disk in a stable situation, the angular
momentum of the accreting matter has to be reduced/enhanced (for
co/counter-rotating disk) by means of some physical process.


title: Theoretical Description of kHz QPOs in accreting LMXB systems

abstract:
  We describe kHz QPOs from the hydrodynamical model of accretion disks for
LMXB systems. Out of the pair, the higher frequency originates due to the
viscous effects of an accretion disk involving the formation of shock, while
the lower one is due to the Keplerian motion of accreting matter. Comparing our
results with observations for two fast rotating compact stellar candidates,
namely, 4U 1636-53 and KS 1731-260, we find that they match to a very good
approximation.


title: Structure Function Studies for Turbulent Interstellar Medium

abstract:
  We study structure functions of rotation measures in the Canadian Galactic
Plane Survey (CGPS) region and the North Galactic Pole (NGP) to extract the
interstellar medium (ISM) fluctuation information. The CGPS data are divided
into three longitude intervals: $82^\circ<l<96^\circ$ (CGPS1),
$115^\circ<l<130^\circ$ (CGPS2) and $130^\circ<l<146^\circ$ (CGPS3). The
structure functions of all three regions have large uncertainties when the
angular separation is smaller than $\delta\theta\approx 1^\circ$. A power law
can fit the structure function well for $\delta\theta>1^\circ$. The power law
indices get smaller from CGPS1 to CGPS3 and the amplitudes decrease. The
variations of the large-scale field and the electron density have only
negligible effects on the structure function and thus cannot account for the
changes, indicating that the turbulent properties of the Galactic ISM are
intrinsically longitude-dependent. The Kolmogorov-like fluctuation spectrum of
the electron density or the magnetic field should produce a power law structure
function with an index of 5/3 or 2/3, neither of which is consistent with our
results of small indices in the three sub-CGPS regions. For the NGP region, the
structure function is flat, showing that the rotation measures are mostly
intrinsic to the extragalactic sources, and the ISM is very random in that part
of our Galaxy. It is obvious that the ISM fluctuation is latitude-dependent
when comparing the results in the NGP region and the CGPS regions.


title: Long Term Timing Observations of PSR B1509-58

abstract:
  We present an updated phase-coherent timing solution for the young, energetic
pulsar PSR B1509-58 for twenty years of data. Using a partially phase-coherent
timing analysis, we show that the second frequency derivative is changing in
time implying a third frequency derivative of (-9+/-1)x10^-32 s^(-4). This
value is consistent with the simple power law model of pulsar rotation.


title: A 20 cm Search for Pulsars in Globular Clusters with Arecibo and the GBT

abstract:
  We are conducting deep searches for radio pulsations at L-band (~ 20cm)
towards more than 30 globular clusters using the 305m Arecibo telescope in
Puerto Rico and the 100m Green Bank Telescope in West Virginia. With roughly
three quarters of our search data analyzed, we have discovered 12 new
millisecond pulsars, 11 of which are in binary systems, and at least three of
which eclipse. We have timing solutions for several of these systems.


title: PSR J2021+3651: A New Gamma-Ray Pulsar Candidate

abstract:
  The COS B high energy gamma-ray source 2CG 075+00, also known as GeV
J2020+3658 or 3EG J2021+3716, has avoided identification with a low energy
counterpart for over twenty years. We present a likely identification with the
discovery and subsequent timing of a young and energetic pulsar, PSR
J2021+3651, with the Wideband Arecibo Pulsar Processor at the Arecibo
Observatory. PSR J2021+3651 has a rotation period P = 104ms and Pdot = 9.6 x
10^{-14}, implying a characteristic age T_c = 17kyr and a spin-down luminosity
Edot = 3.4 x 10^{36} erg s^{-1}. The pulsar is also coincident with the ASCA
source AX J2021.1+3651. The implied luminosity of the associated X-ray source
suggests the X-ray emission is dominated by a pulsar wind nebula unresolved by
ASCA. The pulsar's unexpectedly high dispersion measure DM = 371 pc cm^{-3} and
the d > 10kpc DM distance pose a new question: is PSR J2021+3651 an extremely
efficient gamma-ray pulsar at the edge of the Galaxy? This is a question for
AGILE and GLAST to answer.


title:
Gravitational waves from axisymmetrically oscillating neutron stars in
  general relativistic simulations

abstract:
  Gravitational waves from oscillating neutron stars in axial symmetry are
studied performing numerical simulations in full general relativity. Neutron
stars are modeled by a polytropic equation of state for simplicity. A
gauge-invariant wave extraction method as well as a quadrupole formula are
adopted for computation of gravitational waves. It is found that the
gauge-invariant variables systematically contain numerical errors generated
near the outer boundaries in the present axisymmetric computation. We clarify
their origin, and illustrate it possible to eliminate the dominant part of the
systematic errors. The best corrected waveforms for oscillating and rotating
stars currently contain errors of magnitude $\sim 10^{-3}$ in the local wave
zone. Comparing the waveforms obtained by the gauge-invariant technique with
those by the quadrupole formula, it is shown that the quadrupole formula yields
approximate gravitational waveforms besides a systematic underestimation of the
amplitude of $O(M/R)$ where $M$ and $R$ denote the mass and the radius of
neutron stars. However, the wave phase and modulation of the amplitude can be
computed accurately. This indicates that the quadrupole formula is a useful
tool for studying gravitational waves from rotating stellar core collapse to a
neutron star in fully general relativistic simulations. Properties of the
gravitational waveforms from the oscillating and rigidly rotating neutron stars
are also addressed paying attention to the oscillation associated with
fundamental modes.


title:
Density perturbations in generalized Einstein scenarios and constraints
  on nonminimal couplings from the Cosmic Microwave Background

abstract:
  We study cosmological perturbations in generalized Einstein scenarios and
show the equivalence of inflationary observables both in the Jordan frame and
the Einstein frame. In particular the consistency relation relating the
tensor-to-scalar ratio with the spectral index of tensor perturbations
coincides with the one in Einstein gravity, which leads to the same likelihood
results in terms of inflationary observables. We apply this formalism to
nonminimally coupled chaotic inflationary scenarios with potential $V=c\phi^p$
and place constraints on the strength of nonminimal couplings using a
compilation of latest observational data. In the case of the quadratic
potential ($p=2$), the nonminimal coupling is constrained to be $\xi>-7.0
\times 10^{-3}$ for negative $\xi$ from the $1\sigma$ observational contour
bound. Although the quartic potential ($p=4$) is under a strong observational
pressure for $\xi=0$, this property is relaxed by taking into account negative
nonminimal couplings. We find that inflationary observables are within the
$1\sigma$ contour bound as long as $\xi<-1.7 \times 10^{-3}$. We also show that
the $p \ge 6$ cases are disfavoured even in the presence of nonminimal
couplings.


title:
Spectral Classification and Effective Temperatures of L and T Dwarfs
  Based of Near-Infrared Spectra

abstract:
  We have obtained near-infrared spectra of L dwarfs, L/T transition objects
and T dwarfs using Subaru. Resulting spectra are examined in detail to see
their dependence on the spectral types. We have obtained bolometric
luminosities of the objects with known parallaxes in our sample, first by
integrating the spectra and second by K band bolometric correction. We derive
the relation between effective temperature and spectral type.


title:
High-resolution N-body Simulations of Galactic Cannibalism: The
  Magellanic Stream

abstract:
  Hierarchical clustering represents the favoured paradigm for galaxy formation
throughout the Universe; due to its proximity, the Magellanic system offers one
of the few opportunities for astrophysicists to decompose the full
six-dimensional phase-space history of a satellite in the midst of being
cannibalised by its host galaxy. The availability of improved observational
data for the Magellanic Stream and parallel advances in computational power has
led us to revisit the canonical tidal model describing the disruption of the
Small Magellanic Cloud and the consequent formation of the Stream. We suggest
improvements to the tidal model in light of these recent advances.


title:
A rotational and variability study of a large sample of PMS stars in NGC
  2264

abstract:
  We present the results of an extensive search for periodic and irregular
variable pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC
2664, based on photometric monitoring using the Wide Field Imager (WFI) on the
2.2m telescope on La Silla (Chile). In total, about 10600 stars with I_c
magnitudes between 9.8mag and 21mag have been monitored in our 34x33 arcmin
field. Time series data were obtained in the I_c band in 44 nights between Dec.
2000 and March 2001; altogether we obtained 88 data points per star. Using two
different time series analysis techniques (Scargle and CLEAN) we found 543
periodically variable stars with periods between 0.2 days and 15 days. Also,
484 irregular variable stars were identified using a chi-squared-test. In
addition we have carried out nearly simultaneous observations in V, R_c and a
narrow-band Halpha filter. The photometric data enable us to reject background
and foreground stars from our sample of variable stars according to their
location in the I_c vs. (R_c-I_c) colour-magnitude and (R_c-Halpha) vs.
(R_c-I_c) colour-colour diagram. We could in the end identify 405 periodically
variable and 184 irregular variable PMS stars as cluster members using these
two different tests. In addition 35 PMS stars for which no significant
variablilty were detected could be identified as members using an Halpha
emission index criterion. This yields to a total of 624 PMS stars in NGC 2264,
of which only 182 were known before. Most of the newly found PMS stars are
fainter than I_c = 16 and of late spectral type (>M2). (abridged)


title: HS2237+8154: On the onset of mass transfer or entering the period gap?

abstract:
  We report follow-up observations of a new white dwarf/red dwarf binary
HS2237+8154, identified as a blue variable star from the Hamburg Quasar Survey.
Ellipsoidal modulation observed in the R band as well as the Halpha radial
velocity variations measured from time-resolved spectroscopy determine the
orbital period to be Porb=178.10+-0.08min. The optical spectrum of HS2237+8154
is well described by a combination of a Teff=11500+-1500K white dwarf (assuming
log g=8) and a dM3.5+-0.5 secondary star. The distance implied from the flux
scaling factors of both stellar components is d=105+-25pc. Combining the
constraints obtained from the radial velocity of the secondary and from the
ellipsoidal modulation, we derive a binary inclination of i~50deg-70deg and
stellar masses of Mwd=0.47-0.67Msun and Msec=0.2-0.4Msun. All observations
imply that the secondary star must be nearly Roche-lobe filling. Consequently,
HS2237+8154 may be either a pre-cataclysmic variable close to the start of mass
transfer, or (considering its orbital period) a cataclysmic variable that
terminated mass transfer and entered the period gap, or a hibernating nova.


title:
The implications of disc instabilities on cataclysmic variable structure
  and evolution

abstract:
  Applications of the thermal-viscous disc instability model to various classes
of cataclysmic variable very often require the accretion disc to be truncated.
I argue that in most cases this inner truncation must be due to the white
dwarf's magnetic field.


title: The Toroidal Iron Atmosphere of a Protoneutron Star: Numerical Solution

abstract:
  A numerical method presented by Imshennik et al. (2002) is used to solve the
two dimensional axisymmetric hydrodynamic problem on the formation of a
toroidal atmosphere during the collapse of an iron stellar core and outer
stellar layers. An evolutionary model from Boyes et al. (1999) with a total
mass of $25M_{\odot}$ is used as the initial data for the distribution of
thermodynamic quantities in the outer shells of a high-mass star. We analyze in
detail the results of three calculations in which the difference mesh and the
location of the inner boundary of the computational region are varied. In the
initial data, we roughly specify an angular velocity distribution that is
actually justified by the final result - the formation of a hydrostatic
equilibrium toroidal atmosphere with reasonable total mass, $M^{tot} = (0.117
\div 0.122)M_{\odot}$, and total angular momentum, $J^{tot} = (0.445 \div
0.472) x 10^{50} erg \cdot s$, for the two main calculations. We compare the
numerical solution with our previous analytical solution in the form of
toroidal atmospheres (Imshennik and Manukovskii 2000). This comparison
indicates that they are identical if we take into account the more general and
complex equation of state with a nonzero temperature and self-gravitation
effects in the atmosphere. Our numerical calculations, first, prove the
stability of toroidal atmospheres on characteristic hydrodynamic time scales
and, second, show the possibility of sporadic fragmentation of these
atmospheres even after a hydrodynamic equilibrium is established. The
calculations were carried out under the assumption of equatorial symmetry of
the problem and up to relatively long time scales $(\approx 10s)$.


title:
Dust in the Photospheric Environment II. Effect on the Near Infrared
  Spectra of L and T Dwarfs

abstract:
  We report an attempt to interpret the spectra of L and T dwarfs with the use
of the Unified Cloudy Model (UCM). For this purpose, we extend the grid of the
UCMs to the cases of log g = 4.5 and 5.5. The dust column density relative to
the gas column density in the observable photosphere is larger at the higher
gravities, and molecular line intensity is generally smaller at the higher
gravities. The overall spectral energy distributions (SEDs) are f_{J} < f_{H} <
f_{K} in middle and late L dwarfs, f_{J} < f_{H} > f_{K} in early T dwarfs (L/T
transition objects), and finally f_{J} > f_{H} > f_{K} in middle and late T
dwarfs, where f_{J}, f_{H}, and f_{K} are the peak fluxes at J, H, and K bands,
respectively, in f_{nu} unit. This tendency is the opposite to what is expected
for the temperature effect, but can be accounted for as the effect of thin dust
clouds formed deep in the photosphere together with the effect of the gaseous
opacities including H_2 (CIA), H_2O, CH_4, and K I. Although the UCMs are
semi-empirical models based on a simple assumption that thin dust clouds form
in the region of T_{cr} < T < T_{cond} (T_{cr} = 1800K is an only empirical
parameter while T_{cond} about 2000K is fixed by the thermodynamical data), the
major observations including the overall SEDs as well as the strengths of the
major spectral features are consistently accounted for throughout L and T
dwarfs. In view of the formidable complexities of the cloud formation, we hope
that our UCM can be of some use as a guide for future modelings of the
ultracool dwarfs as well as for interpretation of observed data of L and T
dwarfs.


title:
High resolution infrared spectra of bulge globular clusters: The extreme
  chemical abundances of Terzan 4 and Terzan 5

abstract:
  Using the NIRSPEC spectrograph at Keck II, we have obtained infrared echelle
spectra covering the range $1.5-1.8 \mu \rm m$ for the highly reddened bulge
globular clusters Terzan 4 and Terzan 5. The clusters are of interest because a
blue horizontal branch in Terzan 4 is consistent with very low metallicity,
while Terzan 5 has been proposed as possibly the most metal rich known Galactic
globular cluster. We report the first detailed abundance analysis for stars in
these clusters, and we find [Fe/H]=--1.60 and --0.21 dex for Terzan 4 and
Terzan 5, respectively, confirming the presence of a large metallicity spread
in the bulge as well as in the halo of the Galaxy. We find $\rm
[\alpha/Fe]\approx+0.5$ dex in Terzan 4 and $\rm [\alpha/Fe]\approx +0.3$ dex
in Terzan 5, consistent with what has been found for field stars in the bulge.
The enhanced $\alpha-$element abundances are also consistent with rapid
chemical enrichment, most likely by type II SNe. Finally, we measure very low
$^{12}$C/$^{13}$C$\le10$ ratios in all the giant stars, confirming that
extra-mixing mechanisms due to {\it cool bottom processing} occur during
evolution along the RGB.


title: Effective Compton Cross Section in Non-Degenerate High Temperature Media

abstract:
  The effective compton cross section in a non-degenerate
plasma($n\ll\{\frac{(kT/c)^{2}+2mkT}{h^{2}}\}^{^{3/2}}$) is investigated in a
wide range of temperatures. The results show a decreasing behavior with
temperature especially for $kT\gg m_{e}c^{2}$. The $may be important in
phenomena like accretion discs or ultra-relativistic blast waves in GRB models,
where the emitted radiation has to pass through a medium containing high energy
electrons.


title:
HST/WFPC2 Study of the Trapezium Cluster: the Influence of Circumstellar
  Disks on the Initial Mass Function

abstract:
  We have performed the first measures of mass accretion rates in the core of
the Orion Nebula Cluster. Four adjacent fields centered on the Trapezium stars
have been imaged in the U- and B-bands using the Wide Field Planetary Camera 2
on board the Hubble Space Telescope. In this paper we focus our attention on a
group of 40 stars with known spectral types and complete UBVI WFPC2 photometry.
Approximately three quarters of the sources show excess luminosity in the
U-band, that we attribute to mass accretion. The known correlation between the
U-band excess and the total accretion luminosity allows us to estimate the
accretion rates. Overall, mass accretion rates appear lower than those measured
by other authors in the Orion flanking fields or in Taurus-Auriga. Mass
accretion rates remain low even in the vicinity of the birth line of Palla &
Stahler, suggesting that in the core of the Trapezium cluster disk accretion
has been recently depressed by an external mechanism. We suggest that the UV
radiation generated by the Trapezium OB stars, responsible for the disk
evaporation, may also cause the drop of the mass accretion rate. In this
scenario, low-mass stars may terminate their pre-main sequence evolution with
masses lower than those they would have reached if disk accretion could have
proceeded undisturbed until the final disk consumption. In OB associations the
low-mass end of the Initial Mass Function may therefore be affected by the
rapid evolution of the most massive cluster's stars, causing a surplus
"accretion aborted" very low-mass stars and brown dwarfs, and a deficit of
intermediate mass stars. This trend is in agreement with recent observations of
the IMF in the Trapezium cluster.


title: The Galactic center interstellar medium as seen by ISO

abstract:
  This paper deals with the heating and the ionization of the interstellar
medium (ISM) in the 500 central pc of the Milky Way (hereafter Galactic center,
GC). We review the results of the Infrared Space Observatory (ISO) observations
of a sample of GC molecular clouds located far from thermal radiocontinuum or
far-infrared sources. For the first time, we have been able to study in detail
the dust continuum spectra from 40 to 190 microns founding a warm (30-40 K)
dust component in addition to the well known 15-20 K component. Fine-structure
lines observations have revealed the presence of diffuse ionized gas associated
with the molecular clouds. The effective temperature of the ionizing radiation
is higher than 33000 K. ISO has also allow us to measure the fraction of warm
(~ 150 K) H2 in the GC clouds, which is on average of 30 %. The observations of
the warm (a few 100 K) neutral gas are compatible with a Photon Dominated
Region (PDR) scenario.


title: X-ray Sources and their Optical Counterparts in the Globular Cluster M4

abstract:
  We report on the Chandra X-ray Observatory ACIS-S3 imaging observation of the
Galactic globular cluster M4 (NGC 6121). We detect 12 X-ray sources inside the
core and 19 more within the cluster half-mass radius. The limiting luminosity
of this observation is Lx~10e29 erg/sec for sources associated with the
cluster, the deepest X-ray observation of a globular cluster to date. We
identify 6 X-ray sources with known objects and use ROSAT observations to show
that the brightest X-ray source is variable. Archival data from the Hubble
Space Telescope allow us to identify optical counterparts to 16 X-ray sources.
Based on the X-ray and optical properties of the identifications and the
information from the literature, we classify two (possibly three) sources as
cataclysmic variables, one X-ray source as a millisecond pulsar and 12 sources
as chromospherically active binaries. Comparison of M4 with 47 Tuc and NGC 6397
suggests a scaling of the number of active binaries in these clusters with the
cluster (core) mass.


title:
Radioactive Al26 and Fe60 in the Milky Way: implications of the RHESSI
  detection of Fe60

abstract:
  The recent detection of gamma-ray lines from radioactive Al26 and Fe60 in the
Milky Way by the RHESSI satellite calls for a reassessment of the production
sites of those nuclides. The observed gamma-ray line flux ratio is in agreement
with calculations of nucleosynthesis in massive stars, exploding as SNII
(Woosley and Weaver 1995); in the light of those results, this observation
would suggest then that SNII are the major sources of Al26 in the Milky Way,
since no other conceivable source produces substantial amounts of Fe60.
However, more recent theoretical studies find that SNII produce much higher
Fe60/Al26 ratios than previously thought and, therefore, they cannot be the
major Al26 sources in the Galaxy (otherwise Fe60 would be detected long ago,
with a line flux similar to the one of Al26). Wolf-Rayet stars, ejecting Al26
(but not Fe60) in their stellar winds, appear then as a most natural candidate.
We point out, however, that this scenario faces also an important difficulty.
Forthcoming results of ESA's INTEGRAL satellite, as well as consistent
calculations of nucleosynthesis in massive stars (including stars of initial
masses as high as 100 M_sun and metallicities up to 3 Z_sun), are required to
settle the issue.


title: Iron Line Profiles in Strong Gravity

abstract:
  We describe a new code which can accurately calculate the relativistic
effects which distort the emission from an accretion disc around a black hole.
We compare our results for a disk which extends from the innermost stable orbit
to $20r_{g}$ in both Schwarzschild and maximal ($a=0.998$) Kerr spacetimes with
the two line profile codes which are on general release in the XSPEC spectral
fitting package. These models generally give a very good description of the
relativistic smearing of the line for this range of radii. However, these
models have some limitations. In particular we show that the assumed form of
the {\em angular} emissivity law (limb darkening or brightening) can make
significant changes to the derived line profile where lightbending is
important. This is {\em always} the case for extreme Kerr spacetimes or high
inclination systems, where the observed line is produced from a very large
range of different emitted angles. In these situations the assumed angular
emissivity can affect the derived {\em radial} emissivity. The line profile is
not simply determined by the well defined (but numerically difficult) physical
effects of strong gravity, but is also dependent on the poorly known
astrophysics of the disc emission.


title: Neutron Star Formation and Birth Properties

abstract:
  Our current knowledge of neutron star formation, progenitors, and natal
masses, spins, magnetic fields, and space velocities is briefly reviewed from a
theorist's perspective. More observational information is badly needed to
constrain theoretical possibilities.


title:
The use of Petersen diagrams and period ratios in investigating the
  pulsational content of stars in the classical Instability Strip

abstract:
  The aspects of the analysis of photometric time-series obtained on
double-mode or multiperiodic pulsating stars are briefly reviewed. In
particular, the ratios between frequencies are used to pin cases revealing
peculiarities. In addition to the Petersen diagrams, we also demonstrated that
the period ratios can detect interesting objects. In particular, new results
are obtained on High--Amplitude Delta Scuti contained in the OGLE-II database.


title: Bias in the Estimation of Global Luminosity Functions

abstract:
  We discuss a bias present in the calculation of the global luminosity
function
  (LF) which occurs when analysing faint galaxy samples. This effect exists
because of the different spectral energy distributions of galaxies, which are
in turn quantified by the k-corrections. We demonstrate that this bias occurs
because not all galaxy types are visible in the same absolute magnitude range
at a given redshift and it mainly arises at high redshift since it is related
to large k-corrections. We use realistic simulations with observed LFs to
investigate the amplitude of the bias. We also compare our results to the
global LFs derived from Hubble Deep Field-North and -South (HDF) surveys. We
conclude that, as expected, there is no bias in the global LF measured in the
absolute magnitude range where all galaxy types are observable. Beyond this
range the faint-end slope of the global LF can be over/under-estimated
depending on the adopted LF estimator. The effect is larger when the reference
filter in which the global LF is measured, is far from the rest-frame filter in
which galaxies are selected. The fact that LF estimators are differently
affected by this bias implies that the bias is minimal when the different LF
estimators give measurements consistent with one another at the faint-end. For
instance, we show that the estimators are discrepant in the same way both in
the simulated and HDF LFs. This suggests that the HDF LFs are affected by the
presently studied bias. The best solution to avoid this bias is to derive the
global LF in the reference filter closest to the rest-frame selection filter.


title: VVDS: early results on LSS distribution to z~1.5

abstract:
  The VIMOS VLT Deep Survey (VVDS) is an on-going program to map the evolution
of galaxies, large scale structures and AGNs from the redshift measurement of
more than 100000 objects down to a magnitude I_{AB}=24, in combination with a
multi-wavelength dataset from radio to X-rays. We present here the first
results obtained from more than 20000 spectra. Dedicated effort has been
invested to successfuly enter the ``redshift desert'' 1.5<z<3, by producing
high S/N galaxy templates in the rest wavelength domain probed by VIMOS. We
have produced the luminosity function (LF) of galaxies for the first time out
to I_{AB}=24, and the evolution of the LF for each morphological type is
clearly established, indicating that most of the LF evolution is concentrated
in the later types. We present for the first time the 3D spatial distribution
of a well controlled sample of faint galaxies, and show that significant
clustering is detected out to z~1.5


title: X-ray and Optical Filaments in M87

abstract:
  We compare a very deep X-ray image of M87, at the center of the Virgo
Cluster, to high-quality optical images of the low excitation emission-line gas
in the same region. There are striking coincidences of detail between the two.
We explore the possiblity that this represents a thermal interaction between
hot gas at 10^7 K and warm gas at 10^4 K. We find two temperatures are present
in the X-ray gas, with the lower more prevelant in the vicinity of the optical
filaments. Electron conduction from the hot phase to the cooler one provides a
quantitatively acceptable energy source for the optical filaments, and we show
additionally that it can do so for the brightest X-ray cluster, Perseus. If
operative, conduction in the presence of gas-rich galaxy mergers, may explain
the presence of "cool cores" in clusters of galaxies.


title:
Nitrogen Enriched Quasars in the Sloan Digital Sky Survey First Data
  Release

abstract:
  The quasar Q0353-383 has long been known to have extremely strong nitrogen
intercombination lines at 1486 and 1750 Angstroms, implying an anomalously high
nitrogen abundance of ~15 times solar. A search for similar nitrogen-rich
quasars in the Sloan Digital Sky Survey First Data Release catalog has yielded
20 candidates, including four with nitrogen emission as strong or stronger than
that seen in Q0353-383. Our results indicate that only about 1 in 1700 of
quasars have nitrogen abundances similar to Q0353-383, while up to 1 in 130 may
be in the process of extreme nitrogen enrichment.


title: Conduction and Turbulent Mixing in Galaxy Clusters

abstract:
  We discuss hydrostatic models of galaxy clusters in which heat diffusion
balances radiative cooling. We consider two different sources of diffusion,
thermal conduction and turbulent mixing, parameterized by dimensionless
coefficients, f and alpha_mix, respectively. Models with thermal conduction
give reasonably good fits to the density and temperature profiles of several
cooling flow clusters, but some clusters require unphysically large values of
f>1. Models with turbulent mixing give good fits to all clusters, with
reasonable values of alpha_mix ~ 0.01-0.03. Both types of models are found to
be essentially stable to thermal perturbations. The mixing model reproduces the
observed scalings of various cluster properties with temperature, and also
explains the entropy floor seen in galaxy groups.


title: The Effective Temperatures of Hot Stars II. The Early-O Types

abstract:
  We derive the stellar parameters of a sample of Galactic early-O type stars
by analysing their UV and Far-UV spectra from FUSE (905-1187A), IUE, HST-STIS
and ORFEUS (1200-2000A). The data have been modeled with spherical,
hydrodynamic, line-blanketed, non-LTE synthetic spectra computed with the
WM-basic code. We obtain effective temperatures ranging from Teff = 41,000 K to
39,000 K for the O3-O4 dwarf stars, and Teff = 37,500 K for the only supergiant
of the sample (O4 If+). Our values are lower than those from previous empirical
calibrations for early-O types by up to 20%. The derived luminosities of the
dwarf stars are also lower by 6 to 12%; however, the luminosity of the
supergiant is in agreement with previous calibrations within the error bars.
Our results extend the trend found for later-O types in a previous work by
Bianchi & Garcia.


title: Probing Dark Energy Using Its Density Instead of Its Equation of State

abstract:
  The variation of dark energy density with redshift, $\rho_X(z)$, provides a
critical clue to the nature of dark energy. Since $\rho_X(z)$ depends on the
dark energy equation of state $w_X(z)$ through an integral, $\rho_X(z)$ can be
constrained more tightly than $w_X(z)$ given the same observational data. We
demonstrate this explicitly using current type Ia supernova (SN Ia) data [the
Tonry/Barris sample], together with the Cosmic Microwave Background (CMB) shift
parameter from CMB data (WMAP, CBI, and ACBAR), and the large scale structure
(LSS) growth factor from 2dF galaxy survey data. We assume a flat universe, and
use Markov Chain Monte Carlo (MCMC) technique in our analysis. We find that,
while $w_X(z)$ extracted from current data is consistent with a cosmological
constant at 68% C.L., $\rho_X(z)$ (which has far smaller uncertainties) is not.
Our results clearly show the advantage of using $\rho_X(z)$, instead of
$w_X(z)$, to probe dark energy.


title:
A Catalog of Spectroscopically Identified White Dwarf Stars in the First
  Data Release of the Sloan Digital Sky Survey

abstract:
  We present the full spectroscopic white dwarf and hot subdwarf sample from
the SDSS first data release, DR1. We find 2551 white dwarf stars of various
types, 240 hot subdwarf stars, and an additional 144 objects we have identified
as uncertain white dwarf stars. Of the white dwarf stars, 1888 are non-magnetic
DA types and 171, non-magnetic DBs. The remaining (492) objects consist of all
different types of white dwarf stars: DO, DQ, DC, DH, DZ, hybrid stars like
DAB, etc., and those with non-degenerate companions. We fit the DA and DB
spectra with a grid of models to determine the Teff and log(g) for each object.
For all objects, we provide coordinates, proper motions, SDSS photometric
magnitudes, and enough information to retrieve the spectrum/image from the SDSS
public database. This catalog nearly doubles the known sample of
spectroscopically-identified white dwarf stars. In the DR1 imaged area of the
sky, we increase the known sample of white dwarf stars by a factor of 8.5. We
also comment on several particularly interesting objects in this sample.


title: Dark Energy and Dark Matter Halos

abstract:
  We investigate the effect of dark energy on the density profiles of dark
matter haloes with a suite of cosmological N-body simulations and use our
results to test analytic models. We consider constant equation of state models,
and allow both w>-1 and w<-1. Using five simulations with w ranging from -1.5
to -0.5, and with more than ~1600 well-resolved haloes each, we show that the
halo concentration model of Bullock et al. (2001) accurately predicts the
median concentrations of haloes over the range of w, halo masses, and redshifts
that we are capable of probing. We find that the Bullock et al. (2001) model
works best when halo masses and concentrations are defined relative to an outer
radius set by a cosmology-dependent virial overdensity. For a fixed power
spectrum normalization and fixed-mass haloes, larger values of w lead to higher
concentrations and higher halo central densities, both because collapse occurs
earlier and because haloes have higher virial densities. While precise
predictions of halo densities are quite sensitive to various uncertainties, we
make broad comparisons to galaxy rotation curve data. At fixed power spectrum
normalization (fixed sigma_8), w>-1 quintessence models seem to exacerbate the
central density problem relative to the standard w=-1 model. Meanwhile w<-1
models help to reduce the apparent discrepancy. We confirm that the Jenkins et
al. (2001) halo mass function provides an excellent approximation to the
abundance of haloes in our simulations and extend its region of validity to
include models with w<-1.


title: Photometric Estimates of Stellar Masses in High-Redshift Galaxies

abstract:
  We present a new tool for the photometric estimate of stellar masses in
distant galaxies. The observed SEDs are fitted by combining single stellar
populations, with different SFRs and amounts of dust extinction. This approach
gives us the best flexibility when dealing with the widest variety of physical
situation for the target galaxies. In particular we tested the code on three
classes of sources: dusty ISO-selected starbursts, K-band selected
ellipticals/S0s and z=2-3 Lyman-break galaxies. We pay particular attention in
evaluating the uncertainties in the stellar mass estimate, due to degeneracies
in the physical parameters, different SFHs or metallicities. Based on
optical-NIR photometric data, the stellar masses are found to have overall
uncertainties of a factor of ~2 for E/S0s, ~2-5 for the starbursts population,
and up to 10 for Ly-break galaxies. In any case the latter appear to correspond
to a galaxy population significantly less massive than those observed at lower
redshifts, possibly indicating substantial stellar build-up at z~1-2 in the
field galaxy population. Using simulated deep SIRTF/IRAC observations of
starbursts and Lyman-break galaxies, we investigate how an extension of the
wavelength dynamic range will decrease the uncertainties in the stellar mass
estimate, and find that they will reduce for both classes to factors of 2-3,
good enough for statistically reliable determinations of the galaxy
evolutionary mass functions.


title:
A Wide-Field Corrector at the Prime Focus of a Ritchey-Chretien
  Telescope

abstract:
  We propose a form of a lens corrector at the prime focus of a hyperboloidal
mirror that provides a flat field of view up to 3 deg diameter at image quality
D_{80} < 0.8 arcsec in integrated (0.32-1.10 mcm) light. The corrector consists
of five lenses made of fused silica. Only spherical surfaces are used, so the
system is capable of achieving better images, if necessary, by aspherizing the
surfaces. The optical system of the corrector is stable in the sense that its
principal features are retained when optimized after significant perturbations
of its parameters. As an example, three versions of the corrector are designed
for the V.M.Blanco 4-m telescope at Cerro Tololo Inter-American Observatory
with 2.12 deg, 2.4 deg, and 3.0 deg fields of view.


title:
Measurements of Black Hole Spins and Tests of Strong-Field General
  Relativity

abstract:
  Fast variability studies of accreting black holes in the Galaxy offer us a
unique opportunity to measure the spins of black holes and test the
strong-field behavior of general relativity. In this review, I summarize the
arguments often used in attempts of measuring the spins of black holes,
concentrating on their theoretical foundations. I also argue that X-ray studies
of accreting black holes will be able to provide in the future strong
constraints on deviations from general relativity in the strong-field regime.


title:
A Search for TeV Gamma-ray Emission from the PSR B1259-63/SS2883 Binary
  System with the CANGAROO-II 10-m Telescope

abstract:
  Observations of the PSR B1259-63/SS2883 binary system using the CANGAROO-II
Cherenkov telescope are reported. This nearby binary consists of a 48msec radio
pulsar in a highly eccentric orbit around a Be star, and offers a unique
laboratory to investigate the interactions between the outflows of the pulsar
and Be star at various distances. It has been pointed out that the relativistic
pulsar wind and the dense mass outflow of the Be star may result in the
emission of gamma rays up to TeV energies. We have observed the binary in 2000
and 2001, 47 and 157 days after the October 2000 periastron. Upper limits at
the 0.13--0.54 Crab level are obtained. A new model calculation for high-energy
gamma-ray emission from the Be star outflow is introduced and the estimated
gamma-ray flux considering Bremsstrahlung, inverse Compton scattering, and the
decay of neutral pions produced in proton-proton interactions, is found to be
comparable to the upper limits of these observations. Comparing our results
with these model calculations, the mass-outflow parameters of the Be star are
constrained.


title:
Timing and spectral changes of the Be X-ray transient EXO 0531-6609.2
  through high and low state

abstract:
  We report on spectral and timing analysis of BeppoSAX data of the 13.6 s
period transient X-ray pulsar EXO 0531-6609.2. Observations were carried out in
March 1997 and October 1998, catching the source during a high and a low
emission state, respectively. Correspondingly, the X-ray luminosity is found at
a level of 4.2x10^37 erg/s and 1.5x10^36 erg/s in the two states. In the high
state the X-ray emission in the energy range 1-100 keV is well fitted by an
absorbed power-law with photon index Gamma ~1.7 plus a blackbody component with
a characteristic temperature of ~3.5 keV. Moreover, we find an evidence of an
iron emission at ~6.8 keV, typical feature in this class of sources but never
revealed before in the EXO 0531-6609.2 spectrum. In the low state an absorbed
power-law with Gamma ~0.4 is sufficient to fit the 1-10 keV data. During
BeppoSAX observations EXO 0531-6609.2 display variations of the pulse profile
with the X-ray flux: it showed single peaked and double peaked profiles in the
low and high state, respectively. Based on these two observations we infer a
spin-up period derivative of -(1.14+/-0.08)x10^-10 s/s. By comparing these with
other period measurements reported in literature we find an alternating spin-up
and spin-down behaviour that correlates well with the X-ray luminosity.


title:
Implications of the central metal abundance peak in cooling core
  clusters of galaxies

abstract:
  Recent XMM-Newton observations of clusters of galaxies have provided detailed
information on the distribution of heavy elements in the central regions of
clusters with cooling cores providing strong evidence that most of these metals
come from recent SN type Ia. In this paper we compile information on the
cumulative mass profiles of iron, the most important metallicity tracer. We
find that long enrichment times (larger than 5 Gyr) are necessary to produce
the central abundance peaks. Classical cooling flows, a strongly convective
intracluster medium, and a complete metal mixing by cluster mergers would
destroy the observed abundance peaks too rapidly. Thus the observations set
strong constraints on cluster evolution models requiring that the cooling cores
in clusters are preserved over very long times. We further conclude from the
observations that the innermost part of the intracluster medium is most
probably dominated by gas originating predominantly from stellar mass loss of
the cD galaxy.


title:
Numerical Simulation of the Surface Flow on the Companion Star in a
  Close Binary System II. Construction of Doppler maps and application to
  Galactic supersoft X-ray sources

abstract:
  We perform three-dimensional numerical simulations of surface flows on the
companion star in a semi-detached binary system and construct the corresponding
Doppler maps. The mass ratio of the binary system, $q=M_2/M_1$, considered here
is $q=0.05, 0.33, 0.5, 1, 2$, and 3. For all cases, we obtain the H-, L1-, and
L2-eddies, as found in our previous work, and confirm that the flow pattern
does not heavily depend on the mass ratio. We propose that this kind of problem
be dubbed ``{\it stellar meteorology}.'' The Doppler maps at the position of
the companion show a structure tilted towards clockwise direction and
presenting deviations from the critical Roche surface due to the L1-eddy and
the L2-eddy on the companion star. We apply our results to the Galactic
supersoft X-ray source RX J0019.8+2156 and try to attribute the low radial
velocity component of the emission lines of He II ${\lambda}4686$ observed
recently to the irradiated spot on the surface of the companion rather than
that of the white dwarf or the accretion disc. Based on the comparison between
the observations and our constructed Doppler map, we estimate the mass of the
companion star in RX J0019.8+2156 to be $\sim 2 M_{\odot}$ assuming the mass of
the white dwarf star to be around $0.6 M_{\odot}$.


title: Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation

abstract:
  We investigate the process of galaxy formation as can be observed in the only
currently forming galaxies -- the so-called Tidal Dwarf Galaxies, hereafter
TDGs -- through observations of the molecular gas detected via its CO (Carbon
Monoxide) emission. Molecular gas is a key element in the galaxy formation
process, providing the link between a cloud of gas and a {\it bona fide}
galaxy. We have now detected CO in 9 TDGs with an overall detection rate of
80%, showing that molecular gas is abundant in TDGs, up to a few $10^8
M_\odot$. The CO emission coincides both spatially and kinematically with the
HI emission, indicating that the molecular gas forms from the atomic hydrogen
where the HI column density is high. A possible trend of more evolved TDGs
having greater molecular gas masses is observed, in accord with the
transformation of HI into H$_2$. Although uncertainties are still large for
individual objects as the geometry is unknown, we find that the "dynamical"
masses of TDGs, estimated from the CO line widths, do not seem to be greater
than the "visible" masses (HI + H$_2$ + a stellar component), i.e., TDGs
require no dark matter. We provide evidence that TDGs are self-gravitating
entities, implying that we are witnessing the ensemble of processes in galaxy
formation: concentration of large amounts of gas in a bound object,
condensation of the gas, which is atomic at this point, to form molecular gas
and the subsequent star formation from the dense molecular component.


title: The peculiar galaxy IC 1182: An ongoing merger?

abstract:
  Broad and narrow band images and long slit spectroscopy of IC1182 are
presented. The broad band images reveal a distorted morphology with a large,
heavily obscured disk-like structure and several knots in the central region.
Galactic material, some of it in the form of two tails, is detected well beyond
the main body of the galaxy. The second, fainter tail and several knots are
reported here for the first time. The narrow band images show that the galaxy
is a powerful emitter. The emission in the main lines extends all over the
galaxy, with plumes and arc-like structures seen in H$\alpha$ at large
distances from the center. The uncorrected H$\alpha$ flux corresponds to
3.51$\times10^{41}$ erg s$^{-1}$, 3 times that of Arp 220. The internal
extinction deduced from the Balmer decrement is high all along the slit, with
E$_{B-V}\approx$ 1. There are no clear signs of nuclear activity and the
observed line ratios can be explained in terms of stellar photoionization. The
metallicity of the gas in the two brightest central knots is low, 0.1
Z$_{\odot}$ and 0.06 Z$_{\odot}$ respectively. In the main body of the galaxy,
besides the reported knots, the distribution of the ionized gas resembles that
of an inclined disk about 12 kpc in size. The rotation pattern is complex and
corresponds to two identifiable disk galaxies with observed rotation amplitudes
of 200 \kms and 100 \kms respectively. The data presented here indicate that IC
1182 is a high luminosity starburst system, involving two systems in the
process of merging, with two tidal tails emerging from the central region of
the galaxy.


title:
XMM-Newton Surveys of the Canada-France Redshift Survey Fields - II: The
  X-ray Catalogues, the Properties of the Host Galaxies, and the Redshift
  Distribution

abstract:
  We present the X-ray source catalogues for the XMM surveys of the 3-h and
14-h Canada-France Redshift Survey fields (0.5-10 keV flux range ~2E-15 - 1E-13
erg cm^-2 s^-1). We use a subset of the XMM sources, which have Chandra
positions, to determine the best method of obtaining optical identifications of
sources with only XMM positions. We find optical identifications for 79% of the
XMM sources for which there are deep optical images. The sources without
optical identifications are likely to be optically fainter and have higher
redshifts than the sources with identifications. We have estimated `photometric
redshifts' for the identified sources, calibrating our method using ~200
galaxies in the fields with spectroscopic redshifts. We find that the redshift
distribution has a strong peak at z~0.7.
  The host galaxies of AGN identified in this work cover a wide range of
optical properties with every galaxy type being represented, and no obvious
preference for one type over another. Redder types tend to be more luminous
than blue types, particularly at lower redshifts. The host galaxies also span a
wide range of optical luminosity, in contrast to the narrow range found for the
starburst galaxies detected in micro Jy radio surveys. We find a strong
correlation between optical and X-ray luminosity similar to the Magorrian
relation, although selection effects cannot be ruled out.