title:
Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion
  Emission Densities for IC 418

abstract:
  Recent analyses of nebular spectra have resulted in discrepant abundances
from CNO forbidden and recombination lines. We consider independent methods of
determining ion abundances for emission nebulae, comparing ion emission
measures with column densities derived from resonance absorption lines viewed
against the central star continuum. Separate analyses of the nebular emission
lines and the stellar UV absorption lines yield independent abundances for
ions, and their ratio can be expressed in terms of a parameter n_e_{em}, the
``emission density'' for each ion. Adequate data for this technique are still
scarce, but separate analyses of spectra of the planetary nebula and central
star of IC 418 do show discrepant abundances for several ions, especially Fe
II. The discrepancies are probably due to the presence of absorbing gas which
does not emit and/or to uncertain atomic data and excitation processes, and
they demonstrate the importance of applying the technique of combining
emission- and absorption-line data in deriving abundances for nebulae.


title:
The Chandra Deep Field-North Survey. XVI. The X-ray properties of
  moderate-luminosity Active Galaxies at z>4

abstract:
  We present X-ray spectral analyses of the three z>4 Active Galactic Nuclei
(AGNs) thus far spectroscopically identified in the Chandra Deep Field-North
Survey, at redshifts of 5.186, 4.424, and 4.137. These analyses are made
possible by the extremely deep exposure (2 Ms) and the low Chandra background.
The rest-frame 2.5-40 keV spectra are the first for optically faint (two of the
three sources have I>24) z>4 AGNs. The z=5.186 quasar is well fitted by a
power-law model with photon index Gamma=1.8+/-0.3, consistent with those of
lower-redshift, unobscured AGNs. The other two AGNs have flatter effective
X-ray photon indices (Gamma approx 1.1-1.5), suggesting the presence of
intrinsic absorption (provided their underlying X-ray continua are similar to
those of lower-redshift AGNs). It is possible that the flat X-ray continuum of
the z=4.424 AGN is partially related to its radio loudness. If the z=4.137 AGN
suffers from X-ray absorption, the implied column density is N_H=2x10^23 cm^-2.


title:
Discovery of giant `radio arcs' in cluster Abell 3376: evidence for
  shock acceleration in a violent cluster merger?

abstract:
  New multi-wavelength (radio, optical & X-rays) observational evidences are
presented which show that the nearby (z=0.046), rich cluster of galaxies Abell
3376 is experiencing a major event of binary subcluster merger. The key
evidence is the discovery of a pair of large, optically unidentified diffuse
radio sources (`arcs'), symmetrically located about 2.6 h_{50}^{-1} Mpc apart
at the opposite ends of the hot intra-cluster gas mapped by ROSAT in X-rays. It
is argued that the gas-dynamical shock-waves, which occur naturally during
cluster formation, are accelerating charged particles (cosmic rays) to
relativistic energies, leading to synchrotron emission from the megaparsec
scale radio arcs. If this is so, cluster Abell 3376 would also be a potential
source capable of accelerating cosmic ray particles upto ultra-high energies
(UHECR) of E_{max} ~ 10^{18-19} eV. Thus this cluster is an excellent test-bed
for understanding the physics of merger shocks and origin of enigmatic UHECR
particles in structure formation process. Hence, Abell 3376 provides unique
oppurtunities for further multi-wavelength observations with ground and
space-borne observatories.


title:
Near-Field Microlensing and Its Effects on Stellar Transit Observations
  by Kepler

abstract:
  In this paper, we explore the astrophysical implications of near-field
microlensing and its effects on stellar transit observations, with a special
emphasis on the Kepler mission. Kepler is a NASA-approved mission whose goal is
to detect a large number of extrasolar, earth-like planets by obtaining
near-continuous photometry of > 100,000 F, G, and K dwarfs for four years. The
expected photometric precision of Kepler is 90 micromag (achieved in 15 minute
samples), at which the effect of microlensing by a transiting companion can be
significant. For example, for a solar-type primary transited by a white-dwarf
secondary, the maximum depth of the transit is 0.01%, which is almost entirely
compensated by the microlensing amplification when the white dwarf is at ~0.05
AU. The combined effect of microlensing and transit increases to a net
amplification of 150 micromag at an orbital separation of 0.1 AU, and 2.4
millimag at an orbital separation of 1 AU. Thus, the effect of microlensing can
be used to break the degeneracy between a planetary-mass object for which the
microlensing effect is negligible, and a more massive object of the same size.
For brown dwarfs at orbital separations of a few AU, the effect of microlensing
is several percent of the transit depth, and hence the microlensing effect must
be taken into account in deriving the physical parameters of the brown dwarf.
The microlensing signal caused by a neutron star or a black hole in a binary
can be several millimag, far exceeding the transit depth, and potentially
detectable even from ground-based observations. Kepler will be sensitive to
white dwarfs, neutron stars, and black holes in binaries through their
microlensing signatures. These observations can be used to derive the frequency
of such compact objects in binaries, and to determine their masses.


title: Clustered Star Formation in W75 N

abstract:
  We present 2" to 7" resolution 3 mm continuum and CO(J=1-0) line emission and
near infrared Ks, H2, and [FeII] images toward the massive star forming region
W75 N. The CO emission uncovers a complex morphology of multiple, overlapping
outflows. A total flow mass of greater than 255 Msun extends 3 pc from
end-to-end and is being driven by at least four late to early-B protostars.
More than 10% of the molecular cloud has been accelerated to high velocities by
the molecular flows (> 5.2 km/s relative to v{LSR}) and the mechanical energy
in the outflowing gas is roughly half the gravitational binding energy of the
cloud. The W75 N cluster members represent a range of evolutionary stages, from
stars with no apparent circumstellar material to deeply embedded protostars
that are actively powering massive outflows. Nine cores of
millimeter-wavelength emission highlight the locations of embedded protostars
in W75 N. The total mass of gas & dust associated with the millimeter cores
ranges from 340 Msun to 11 Msun. The infrared reflection nebula and shocked H2
emission have multiple peaks and extensions which, again, suggests the presence
of several outflows. Diffuse H2 emission extends about 0.6 parsecs beyond the
outer boundaries of the CO emission while the [FeII] emission is only detected
close to the protostars. The infrared line emission morphology suggests that
only slow, non-dissociative J-type shocks exist throughout the pc-scale
outflows. Fast, dissociative shocks, common in jet-driven low-mass outflows,
are absent in W75 N. Thus, the energetics of the outflows from the late to
early B protostars in W75 N differ from their low-mass counterparts -- they do
not appear to be simply scaled-up versions of low-mass outflows.


title: Formation of Globular Clusters: In and Out of Dwarf Galaxies

abstract:
  Despite the rapid observational progress in the study of young massive star
clusters, the formation of globular clusters still remains poorly understood.
Yet, it is emerging that globular cluster formation is intimately linked to the
formation of the Galaxy. I discuss a generic scenario of the cluster formation
within progenitor galaxies, based on the available observational constraints.
The oldest clusters formed around redshift z = 7, but the process continued at
least until z = 3. Because of their high density, globular clusters survived
when their progenitor galaxies were disrupted by the Galactic tidal field.


title: 3D Anelastic Simulations of Convection in Massive Stars

abstract:
  After briefly describing the anelastic approximation and Glatzmaier's code,
we present results from our preliminary studies of core convection during the
hydrogen burning phase of a 15 solar mass star, as well as our most recent
results concerning convection in the oxygen shell of a 25 solar mass star.


title: A near-infrared survey for Galactic Wolf-Rayet stars

abstract:
  Initial results, techniques, and rationale for a near-infrared survey of
evolved emission-line stars toward the Galactic Center are presented. We use
images taken through narrow-band emission-line and continuum filters to select
candidates for spectroscopic follow-up. The filters are optimized for the
detection of Wolf-Rayet stars and other objects which exhibit emission-lines in
the 2 micron region. Approximately three square degrees along the Galactic
plane have been analyzed in seven narrow-filters (four emission-lines and three
continuum). Four new Wolf-Rayet stars have been found which are the subject of
a following paper.


title:
A spectro-astrometric study of southern pre-main sequence stars -
  binaries, outflows, and disc structure down to AU scales

abstract:
  We present spectro-astrometric observations for 28 southern pre-main sequence
(PMS) stars and investigate their circumstellar environment down to AU scales.
The structures detected in the ``position spectra'' include: (1) almost all the
known binary companions in our sample (Sz 68, Sz 41, HO Lup, VW Cha, S CrA, AS
205), (2) companion candidates which have not been detected by infrared speckle
techniques (T CrA, MWC 300), (3) monopolar and bipolar jets (AS 353A, CS Cha),
(4) a combination of jets and a bow shock (VV CrA), and (5) a combination of a
jet and stellar companion (R CrA). Results in known binaries show that this
technique is capable of detecting binaries with separations down to ~10
milliarcsec. Both components in each binary appear to have strikingly similar
profiles in H-alpha emission, indicating a similarity of circumstellar activity
(mass accretion and/or a wind), and supporting the scenario of core
fragmentation for the mechanism of binary formation. The bipolar H-alpha jet in
CS Cha has a spatial scale of ~1.5 AU, similar to that previously observed in
RU Lup, and likely be heated by a mechanism other than shocks. From the spatial
scale, velocity, and H-alpha luminosity, we estimate the mean hydrogen density
in the AU-scale bipolar flows to be > 10^7 cm^-3. The bipolar geometry in these
jets can be explained by the presence of a disc gap/hole at AU scales, which
could be induced by a gas-giant planet at the ice condensation radius.


title: The impact of galaxy formation on X-ray groups

abstract:
  Using hydrodynamical simulations of the LCDM cosmology, that include both
radiative cooling and a phenomenological model for star formation and
supernovae feedback, we investigate the impact of galaxy formation on the X-ray
properties of groups at redshift zero. Motivated by the observed ``break'' in
the L_x-T_x relation at kT~1-2keV, our feedback model is based on the
assumption that supernovae imprint a temperature scale on the hot gas, with the
star formation rate and corresponding reheated gas mass then depending only on
the available energy budget. We demonstrate that a strong feedback model with a
heating temperature comparable to this break (kT_=2keV), and an energy budget
twice that available from supernovae (epsilon=2), raises the core entropy of
groups sufficiently to produce an adequate match to their observed X-ray
properties. A lower value of epsilon increases the star formation rate without
significantly affecting the X-ray properties of groups, and a model with
epsilon~0.1 reproduces the observed fraction of baryons in stars. However, a
heating temperature which is lower than the virial temperatures of the groups
leads to an excess of cooling gas that boosts their X-ray luminosities, due to
the failure of the reheated material to escape from the gravitational
potential. A limited study of numerical resolution effects reveals that the
temperature of poorly-resolved objects is underestimated, therefore (in our
case) a fully-resolved group population would lead to a steeper L_x-T_x
relation, bringing our results into even better agreement with the
observations.


title: Evolution of zero-metallicity massive stars

abstract:
  We discuss the evolutionary properties of primordial massive and very massive
stars, supposed to have formed from metal-free gas. Stellar models are
presented over a large range of initial masses (8 Msun <= Mi <= 1000 Msun),
covering the hydrogen- and helium-burning phases up to the onset of carbon
burning. In most cases the evolution is followed at constant mass. To estimate
the possible effect of mass loss via stellar winds, recent analytic formalisms
for the mass-loss rates are applied to the very massive models (Mi >= 120
Msun).


title: Centimeter-band Variability in GPS Sources

abstract:
  Monitoring results are presented for the Stangellini 1 Jy GHz-peaked-spectrum
source sample, illustrating that several members exhibit variability in total
flux and/or linear polarization over timescales of order a decade. The
variability occurs while the spectrum, based on the integrated fluxes, remains
steep and characteristic of a transparent source. Total flux variability is
unexpected in view of recent VLBI observations indicating no or hidden cores in
several members. However, both the variability, and the detection of circular
polarization in one class member, argue for the presence of opacity in some
portion of the radio jet.


title:
Study of a Strategy for Parallax Microlensing Detection Towards the
  Magellanic Clouds

abstract:
  In this article, we have investigated the possibility to distinguish between
different galactic models through the microlensing parallax studies. We show
that a systematic search for parallax effects can be done using the currently
running alert systems and complementary photometric telescopes, to distinguish
between different lens distance distributions. We have considered two galactic
dark compact objects distributions, with total optical depths corresponding to
the EROS current upper limits. These models correspond to two extreme
hypothesis on a three component galactic structure made of a thin disc, a thick
disc, and a spherically symmetric halo. Our study shows that for sub-solar mass
lenses, an exposure of $8\times 10^7$ star$\times$yr toward LMC should allow to
distinguish between these two extreme models. In addition the self-lensing
hypothesis (lensing by LMC objects) can efficiently be tested through the
method proposed here.


title:
High frequency quasi-periodic oscillations in the black hole X-ray
  transient XTE J1650-500

abstract:
  We report the detection of high frequency variability in the black hole X-ray
transient XTE J1650-500. A quasi-periodic oscillation (QPO) was found at 250 Hz
during a transition from the hard to the soft state. We also detected less
coherent variability around 50 Hz, that disappeared when the 250 Hz QPO showed
up. There are indications that when the energy spectrum hardened the QPO
frequency increased from ~110 Hz to ~270 Hz, although the observed frequencies
are also consistent with being 1:2:3 harmonics of each other. Interpreting the
250 Hz as the orbital frequency at the innermost stable orbit around a
Schwarzschild black hole leads to a mass estimate of 8.2 Msun. The spectral
results by Miller et al.(2002, ApJ, 570, L69), which suggest considerable black
hole spin, would imply a higher mass.


title:
RX J1039.7-0507: A New Intermediate Polar and Probable Recent Nova,
  possessing a large Reflection Effect

abstract:
  The ROSAT source RX J1039.7-0507, known from its optical spectrum to be a
Cataclysmic Variable star, is shown from high speed photometry to have an
orbital period of 1.574 h. The system has a nearly sinusoidal photometric
modulation with a range of 1.1 mag which we interpret as the reflection effect
caused by a very hot white dwarf primary. This suggests that a nova explosion
occured on the primary in the relatively recent past. In addition, RX
J1039.7-0507 has periodic signals at 1932.5 s and 721.9 s which, with the aid
of other periods present at low amplitude, we interpret as an orbital sideband
and the first harmonic of the primary's spin period. RX J1039.7-0507 is
therefore an intermediate polar with a spin period of 1444 s (24.07 min).


title: The LARI Method for ISO-CAM/PHOT Data Reduction and Analysis

abstract:
  The techniques and software tools developed for the reduction and analysis of
ISO-CAM/PHOT data with the LARI method are presented. The method, designed for
the detection of faint sources in ISO raster observations, is based on the
assumption of the existence of two different time scales in the detectors'
transient behaviour, accounting either for fast or slow detectors' response.
  The specifically developed IDL software includes: a reduction pipeline
performing basic operations such as deglitching and background determination;
the fitting procedures proper, modelling the time history of individual pixels
and detecting any flux excess with respect to the local background ascribable
to potential sources; mapping, source extraction and flux estimation
procedures; simulation procedures allowing one to estimate the errors arising
from different instrumental and reduction effects. Moreover, an easy-to-use
graphical user interface allows one to quickly browse the data and carry out
the substantial amount of interactive analysis required when the automatic fit
fails and to check the reliability of detected sources.
  This method provides source lists of great reliability and completeness and
an outstanding photometric accuracy, particularly at low redundancy levels,
where the reliability of ISO-CAM/PHOT source lists, even at moderately bright
flux levels, has been a long-standing issue.
  In this work a description of the techniques and software tools that have
been developed is given, alongside with some highlights from the results
obtained thanks to their application to different fields.


title: On determining the cluster abundance normalization

abstract:
  Different determinations currently suggest scattered values for the power
spectrum normalization on the scale of galaxy clusters, sigma_8. Here we
concentrate on the constraints coming from the X-ray temperature and luminosity
functions (XTF and XLF), and investigate several possible sources of
discrepancies in the results. We conclude that the main source of error in both
methods is the scaling relation involved, in particular the way its intrinsic
scatter and systematic normalization are treated. For temperature derived
constraints, we use a sample adapted from HIFLUGCS, and test for several
sources of systematic error. We parameterize the mass-temperature relation with
an overall factor T_ast, with 1.5 \le T_ast \le 1.9. After marginalising over
the range of T_ast, we obtain a 68 per cent confidence range of
sigma_8=0.77^{+0.05}_{-0.04} for a standard LambdaCDM model. For luminosity
derived constraints we use the XLF from the REFLEX survey and explore how
sensitive the final results are on the details of the mass-luminosity, M-L,
conversion. Assuming a uniform systematic uncertainty of +/-20 per cent in the
amplitude of the mass-luminosity relation by Reiprich and Bohringer, we derive
sigma_8=0.79^{+0.06}_{-0.07} for the same standard LambdaCDM model. Although
the XTF and XLF derived constraints agree very well with each other, we
emphasize that such results can change by about 10--15 per cent, depending on
how uncertainties in the L-T-M conversions are interpreted and included in the
analysis. In order to achieve precision cosmology, with this probe, it is
important to separate the uncertainty in the scaling relation into its
intrinsic and overall normalization parts.


title:
A High-Resolution Rotation Curve of NGC 6822: A Test-case for Cold Dark
  Matter

abstract:
  We present high resolution rotation curves of the local group dwarf irregular
galaxy NGC 6822 obtained with the Australia Telescope Compact Array. Our best
curves have an angular resolution of 8'' or 20 pc and contain some 250
independent points. The stellar and gas components of NGC 6822 cannot explain
the shape of the curve, except for the very inner regions, and NGC 6822 is
consequently very dark matter dominated. There is no evidence for the presence
of a steep density cusp down to scales of ~20 pc, contrary to the predictions
of Cold Dark Matter.


title: AGN as cosmic thermostats

abstract:
  We present a simple analytical model and the results of numerical simulations
supporting the idea of periodical heating of cluster gas by AGN outflows. We
show why, under this assumption, we are extremely unlikely to observe clusters
containing gas with a temperature below about 1 keV. We review the results from
numerical hydro-simulations studying the mechanisms by which AGN outflows heat
the cluster gas.


title: Supernovae with "Super-Hipparcos"

abstract:
  GAIA is the ``super-Hipparcos'' satellite scheduled for launch in 2010 by the
European Space Agency. It is a scanning satellite that carries out
multi-colour, multi-epoch photometry on all objects brighter than 20th
magnitude. We conduct detailed simulations of supernovae (SNe) detection by
GAIA. Supernovae of each type are chosen according to the observed
distributions of absolute magnitudes, and located in nearby galaxies according
to the local large-scale structure. Using an extinction model of the Galaxy and
the scanning law of the GAIA satellite, we calculate how many SNe are
detectable as a function of the phase of the lightcurve. Our study shows that
GAIA will report data on 21400 SNe during the five-year mission lifetime, of
which 14300 are SNe Ia, 1400 are SNe Ib/c and 5700 are SNe II. Using the
simulations, we estimate that the numbers caught before maximum are 6300 SNe
Ia, 500 SNe Ib/c and 1700 SNe II. GAIA will issue about 5 SNe alerts a day. The
most distant SNe accessible to GAIA are at a redshift of 0.14 and so GAIA will
provide a huge sample of local SNe. There will be many examples of the rarer
subluminous events, over-luminous events, SNe Ib/c and SNe II-L. SNe rates will
be found as a function of galaxy type, as well as extinction and position in
the host galaxy. Amongst other applications, there may be about 26 SNe each
year for which detection of gravitational waves is possible and about 180 SNe
each year for which detection of gamma-rays is possible.


title: Poynting Jets from Accretion Disks

abstract:
  We give further considerations on the problem of the evolution of a coronal,
force-free magnetic field which threads a differentially rotating, conducting
Keplerian disk, extending the work of Li {\it et al.} (2001). This situation is
described by the force-free Grad-Shafranov (GS) equation for the flux function
$\Psi(r,z)$ which labels the poloidal field lines (in cylindrical coordinates).
The GS equation involves a function $H(\Psi)$ describing the distribution of
poloidal current which is determined by the differential rotation or {\it
twist} of the disk which increases linearly with time. We numerically solve the
GS equation in a sequence of volumes of increasing size corresponding to the
expansion of the outer perfectly conducting boundaries at ($R_{m}, Z_{m}$). The
outer boundaries model the influence of an external non-magnetized plasma. The
sequence of GS solutions provides a model for the dynamical evolution of the
magnetic field in response to (1) the increasing twist of the disk and (2) the
pressure of external plasma. We find solutions with {\it magnetically
collimated} Poynting jets where there is a {\it continuous} outflow of energy,
angular momentum, and toroidal magnetic flux from the disk into the external
space.


title: Far Ultraviolet Spectra of a Non-Radiative Shock Wave in the Cygnus Loop

abstract:
  Spatial and spectral profiles of O VI emission behind a shock wave on the
northern edge of the Cygnus Loop were obtained with the FUSE satellite. The
velocity width of the narrowest O VI profile places a tight constraint on the
electron-ion and ion-ion thermal equilibration in this 350 $\rm km s^{-1}$
collisionless shock. Unlike faster shocks in SN1006 and in the heliosphere,
this shock brings oxygen ions and protons to within a factor of 2.5 of the same
temperature. Comparison with other shocks suggests that shock speed, rather
than Alfv\'{e}n Mach number, may control the degree of thermal equilibration.
  We combine the O VI observations with a low resolution far UV spectrum from
HUT, an H$\alpha$ image and ROSAT PSPC X-ray data to constrain the pre-shock
density and the structure along the line-of-sight. As part of this effort, we
model the effects of resonance scattering of O VI photons within the shocked
gas and compute time-dependent ionization models of the X-ray emissivity.
Resonance scattering affects the O VI intensities at the factor of 2 level, and
the soft spectrum of the X-ray rim can be mostly attributed to departures from
ionization equilibrium. The pre-shock density is about twice the canonical
value for the Cygnus Loop X-ray emitting shocks.


title:
The Cosmic Density of Massive Black Holes from Galaxy Velocity
  Dispersions

abstract:
  Supermassive black holes are thought to be relics of quasars, and their
numbers and masses are therefore related to the quasar luminosity function and
its evolution with redshift. We have used the relationship between black hole
mass and bulge velocity dispersion (the M_bullet - sigma relation) to make an
improved estimate of the mass density and mass spectrum of supermassive black
holes. Uncertainties in the M_bullet - sigma relation have little effect on the
mass density. We find a mass density of (4.8 +/- 1.6) h^2 x 10^5 M_sun Mpc^-3.
Some of the variance in published density estimates comes from the use of
different values of the Hubble constant.


title: Globular Clusters in Compact Groups

abstract:
  We have studied globular cluster systems (GCSs) around elliptical galaxies in
Hickson compact groups using multi-band deep, high quality images from Keck,
VLT and CFHT. Analyzing the luminosity functions, specific frequencies, color
and spatial distributions, we could determine the properties of the GCSs of
those galaxies and trace their star formation histories. We have found poor
populations, concentrated toward the center of the galaxies, with bimodal color
distributions. The study of GCSs around galaxies in small groups are a blank on
the globular cluster literature.


title: X-ray Observations of the Warm-Hot Intergalactic Medium

abstract:
  We present Chandra observations that provide the most direct evidence to date
for the pervasive, moderate density, shock-heated intergalactic medium
predicted by leading cosmological scenarios. We also comment briefly on future
observations with Constellation-X.


title: Optical Diffuse Light in Nearby Compact Groups

abstract:
  Analyses of B and R band observations of four compact groups reveal the
presence of a considerable amount of diffuse, intergalactic light in two of
them (HCG 79 and HCG 95). The diffuse component is presumably due to stellar
material that has been tidally stripped from the galaxy group members. A new
approach is used to measure this diffuse background light, using wavelet
techniques for detecting low surface brightness signals. The diffuse light
component has a mean colour of $(B-R)$ = 1.4 - 1.5$\pm$0.1 and it comprises the
following fractions of the total group light in the B band: 18%, 12%, 3% and 0%
for groups HCG 95, HCG 79, HCG 92 and HCG 88, respectively. The diffuse light
content of a group may represent an efficient tool for the determination of how
long groups have been together in a compact configuration.


title:
Extrasolar Planets in Mean-Motion Resonance: Apses Alignment and
  Asymmetric Stationary Solutions

abstract:
  In recent years several pairs of extrasolar planets have been discovered in
the vicinity of mean-motion commensurabilities. In some cases, such as the
Gliese 876 system, the planets seem to be trapped in a stationary solution, the
system exhibiting a simultaneous libration of the resonant angle theta_1 = 2
lambda_2 - lambda_1 - varpi_1 and of the relative position of the pericenters.
  In this paper we analyze the existence and location of these stable
solutions, for the 2/1 and 3/1 resonances, as function of the masses and
orbital elements of both planets. This is undertaken via an analytical model
for the resonant Hamiltonian function. The results are compared with those of
numerical simulations of the exact equations.
  In the 2/1 commensurability, we show the existence of three principal
families of stationary solutions: (i) aligned orbits, in which theta_1 and
varpi_1 - varpi_2 both librate around zero, (ii) anti-aligned orbits, in which
theta_1=0 and the difference in pericenter is 180 degrees, and (iii) asymmetric
stationary solutions, where both the resonant angle and varpi_1 - varpi_2 are
constants with values different of 0 or 180 degrees. Each family exists in a
different domain of values of the mass ratio and eccentricities of both
planets. Similar results are also found in the 3/1 resonance.
  We discuss the application of these results to the extrasolar planetary
systems and develop a chart of possible planetary orbits with apsidal
corotation. We estimate, also, the maximum planetary masses in order that the
stationary solutions are dynamically stable.


title: Nearby candidate dust-disk pre-main-sequence solar-mass stars

abstract:
  I have isolated a population of numerous F stars that appear to be
pre-main-sequence (PMS). The candidate PMS stars have been identified using CM
diagram, reddening, flux excess in the UV and near-infrared, and luminosity
anomaly. Negative luminosity anomaly and excessive UV flux for many of these
stars is suggestive of accretion disks, while the NIR excess is indicative in
many cases of the presence of dust disk thermal emission.
  Observed overluminosity of many PMS candidates is consistent with their
pre-main-sequence status. The bulk of the PMS candidates is located within
  200 pc, exhibiting strong association with regions of star formation that are
numerous between ~130 to 180 pc. The number of PMS candidates plummets redward
of the spectral type ~ F5. This effect may provide important clues for
understanding the evolution of PMS stars in the solar-mass range.


title: Enhanced HCN(1-0) Emission in the Type-1 Seyfert Galaxy NGC 1097

abstract:
  The central kpc region of the low luminosity type-1 Seyfert galaxy NGC 1097
has been observed in the CO(1-0) and HCN(1-0) lines with the Nobeyama
Millimeter Array and the NRO 45 m telescope. We find a striking enhancement of
the HCN emission toward the active nucleus of NGC 1097; a large fraction of the
CO emission comes from the circumnuclear starburst ring (r = 10" or 700 pc at D
= 14.5 Mpc), whereas the HCN emission is dominated by a strong unresolved peak
at the nucleus. The HCN-to-CO integrated intensity ratio in brightness
temperature scale is about 0.11 in the aperture of the 45 m telescope beams (r
< 510 pc for CO and r < 640 pc for HCN), but it reaches 0.34 in the smaller
aperture (within the central r < 350 x 150 pc region). These CO and HCN
properties in NGC 1097 are similar to those in the type-2 Seyfert galaxies NGC
1068 and NGC 5194 (M 51).


title: High-Energy Astrophysics and Cosmology

abstract:
  Interfaces between high-energy physics, astrophysics and cosmology are
reviewed, with particular emphasis on the important roles played by high-energy
cosmic-ray physics. These include the understanding of atmospheric neutrinos,
the search for massive cold dark matter particles and possible tests of models
of quantum gravity. In return, experiments at the LHC may be useful for
refining models of ultra-high-energy cosmic rays, and thereby contributing
indirectly to understanding their origin. Only future experiments will be able
to tell whether these are due to some bottom-up astrophysical mechanism or some
top-down cosmological mechanism.


title: Gravitational waves from newly born, hot neutron stars

abstract:
  We study the gravitational radiation associated to the non--radial
oscillations of newly born, hot neutron stars. The frequencies and damping
times of the relevant quasi--normal modes are computed for two different models
of proto--neutron stars, at different times of evolution, from its birth until
it settles down as a cold neutron star. We find that the oscillation properties
of proto--neutron stars are remarkably different from those of their cold, old
descendants and that this affects the characteristic features of the
gravitational signal emitted during the post-collapse evolution. The
consequences on the observability of these signals by resonant--mass and
interferometric detectors are analyzed. We find that gravitational waves from
the pulsations of a newborn proto--neutron star in the galaxy could be detected
with a signal to noise ratio of 5 by the first generation interferometers, if
the energy stored in the modes is greater than $\sim 10^{-8} M_\odot c^2$, or
by a resonant antenna if it is greater than $\sim 10^{-4} M_\odot c^2$. In
addition since at early times the frequency of the spacetime modes is much
lower than that of a cold neutron star, they would be also detectable with the
same signal to noise ratio if a comparable amount of energy is radiated into
these modes.


title: The Formation of Globular Cluster Systems

abstract:
  I briefly review models for the formation of globular cluster systems, and
summarize the observational properties (i.e., formation efficiencies,
metallicity distributions, kinematics and ages) of the globular cluster systems
of M87 and M49: two thoroughly studied elliptical galaxies. Many of the
properties of the metal-poor clusters in these and other galaxies appear to be
consistent with their formation in low-mass, proto-galactic fragments, as
proposed by several different formation models. A number of outstanding
questions concerning the formation of the metal-rich clusters in these galaxies
are highlighted.


title:
Interpretation of the Tadpole VV29 Merging Galaxy System using
  Hydro-Gravitational Theory

abstract:
  Hubble Space Telescope (HST/ACS) images of the galaxy merger Tadpole are
interpreted using the hydro-gravitational theory of Gibson 1996-2000 (HGT) that
predicts galaxy masses within about 100 kpc are dominated by dark halos of
planetary mass primordial-fog-particles (PFPs) in dark
proto-globular-star-clusters (PGCs). According to our interpretation, stars and
young-globular-clusters (YGCs) appear out of the dark as merging galaxy
components VV29cdef move through the baryonic-dark-matter halo of the larger
galaxy VV29a creating luminous star-wakes. Frozen PFP planets are evaporated by
radiation and tidal forces of the intruders. Friction from the gas accelerates
an accretional cascade of PFPs to form larger planets, stars and YGCs of the
filamentary galaxy VV29b. Star-wakes show that galaxy VV29c, identified as a
blue dwarf by radio telescope observations of gas density and velocity (Briggs
et al. 2001), with companions VV29def entered the dark halo of the larger VV29a
galaxy at a radius 130 kpc and then spiraled in on different tracks toward
frictional capture by the VV29a core. A previously dark dwarf galaxy is
identified from a Keck spectrographic study showing a VV29c star-wake dense
cluster of YGCs aligned to 1 degree in a close straight row (Tran et al. 2003).


title: GRB 021004: Reverse Shock Emission

abstract:
  We show that the re-brightening in the GRB 021004 optical afterglow light
curve around ~ 0.1 day can be explained within the framework of the standard
fireball model. The superposition of a forward and reverse shock emissions
result in the peculiar behavior. With the standard values of parameters
obtained in other afterglow observations, we can construct an example case in
which theoretical estimates reasonably fit the broadband observations.
Therefore, the peculiarity of the light curve might be a common feature in
early gamma-ray burst afterglows.


title: Observations of possible symbiotic star V335 Vul

abstract:
  We present visual and CCD VRI observations of a suspected symbiotic binary
V335 Vul. Long term photometry suggests usual Mira or SRa pulsations. High
speed V band CCD photometry didn't reveal anything unusual above 0.02 mag.


title:
Stellar structure and mass loss during the early post asymptotic giant
  branch

abstract:
  Late asymptotic giant branch (AGB) and early post-AGB stars which are
progenitors of planetary nebulae lose mass at extremely high rate, in what is
termed a superwind. We show that the existence of this superwind during the
post-AGB phase cannot be explained with models where the stellar effective
temperature is the sole main physical parameter which determine the mass loss
rate. Instead, we argue that the envelope structure, in particular the entropy
and density gradients, should be among the main parameters which determine the
mass loss rate on the tip of the AGB and the early post-AGB evolutionary
phases. The entropy profile becomes steeper and the density profile becomes
shallower as the star becomes hotter on the early post-AGB phase, until the
star heats-up to about 8000 K. We do not propose a new mass loss mechanism, but
rather mention several mechanisms by which these profiles may influence the
mass loss rate within the popular mechanism for mass loss on the AGB, where
pulsations coupled with radiation pressure on dust cause the high mass loss
rate.


title: Globular Cluster Formation

abstract:
  The discovery of young globular clusters in merging galaxies and other
environments provides an opportunity to study directly the process of globular
cluster formation. Empirically it appears that globular cluster formation
occurs preferentially in regions in which star formation occurs at a high rate
and efficiency. Further, the interstellar medium in such regions is likely to
be at a higher pressure than less active star-forming environments. An
additional observational clue to the globular cluster formation process is that
young globular clusters have little or no mass-radius relationship. In this
paper I argue that high pressure and high star-formation efficiency are
responsible for current globular cluster formation. I suggest that the
precursors to globular clusters are molecular clouds and that the mass-radius
relationship exhibited by such clouds is wiped out by a variable star formation
efficiency.


title:
Addendum: "The Dynamics of M15: Observations of the Velocity Dispersion
  Profile and Fokker-Planck Models" (ApJ, 481, 267 [1997])

abstract:
  It has recently come to our attention that there are axis scale errors in
three of the figures of Dull et al. (1997, hereafter D97). D97 presented
Fokker-Planck models for the collapsed-core globular cluster M15 that include a
dense, centrally concentrated population of neutron stars and massive white
dwarfs, but do not include a central black hole. In this Addendum, we present
corrected versions of Figures 9, 10, and 12, and an expanded version of Figure
6. This latter figure, which shows the full run of the velocity dispersion
profile, indicates that the D97 model predictions are in good agreement with
the moderately rising HST-STIS velocity dispersion profile for M15 reported by
Gerssen et al. (2002, astro-ph/0209315). Thus, a central black hole is not
required to fit the new STIS velocity measurements, provided that there is a
sufficient population of neutron stars and massive white dwarfs. This
conclusion is consistent with the findings of Gerssen et al. (2002,
astro-ph/0210158), based on a reapplication of their Jeans equation analysis
using the corrected mass-to-light profile (Figure 12) for the D97 models.


title:
A Primordial Origin of the Laplace Relation Among the Galilean
  Satellites

abstract:
  Understanding the origin of the orbital resonances of the Galilean satellites
of Jupiter will constrain the longevity of the extensive volcanism on Io, may
explain a liquid ocean on Europa, and may guide studies of the dissipative
properties of stars and Jupiter-like planets. The differential migration of the
newly formed Galilean satellites due to interactions with a circumjovian disk
can lead to the primordial formation of the Laplace relation n_1 - 3 n_2 + 2
n_3 = 0, where the n_i are the mean orbital angular velocities of Io, Europa,
and Ganymede, respectively. This contrasts with the formation of the resonances
by differential expansion of the orbits from tidal torques from Jupiter.


title: A Globular Cluster Metallicity Scale Based on the Abundance of Fe II

abstract:
  Assuming that in the atmospheres of low-mass, metal-poor red giant stars, 1-D
models based on LTE accurately predict the abundance of iron from Fe II, we
derive a globular cluster metallicity scale based on the equivalent widths of
Fe II lines measured from high resolution spectra of giants in 16 key clusters
lying in the abundance range -2.4 < [Fe/H]II < -0.7. We base the scale largely
on the analysis of spectra of 149 giant stars in 11 clusters by the Lick-Texas
group supplemented by high-resolution studies of giants in five other clusters.
We also derive ab initio the true distance moduli for M5, M3, M13, M92, and M15
as a means of setting stellar surface gravities. We find that [Fe/H]II is
correlated linearly with <W'>, the reduced strength of the near infra-red Ca II
triplet defined by Rutledge et al, although the actual correlation coefficients
depend on the atmospheric model employed. We also discuss how to estimate
[X/Fe]-ratios. We suggest that C, N, and O, as well as elements appearing in
the spectrum in the singly ionized state, e.g., Ti, Sc, Ba, La and Eu, should
be normalized to the abundance of Fe II. Other elements, which appear mostly in
the neutral state, but for which the dominant species is nevertheless the
ionized state, are probably best normalized to Fe I, but uncertainties remain.


title:
Nonradial Oscillations of Neutron Stars with a Solid Crust -- Analysis
  in the Relativistic Cowling Approximation--

abstract:
  Nonradial oscillations of relativistic neutron stars with a solid crust are
computed in the relativistic Cowling approximation, in which all metric
perturbations are ignored. For the modal analysis, we employ three-component
relativistic neutron star models with a solid crust, a fluid core, and a fluid
ocean. As a measure for the relativistic effects on the oscillation modes, we
calculate the relative frequency difference defined as
$\delta\sigma/\sigma\equiv(\sigma_{GR}-\sigma_N)/\sigma_{GR}$, where
$\sigma_{GR}$ and $\sigma_R$ are, respectively, the relativistic and the
Newtonian oscillation frequencies. The relative difference
$\delta\sigma/\sigma$ takes various values for different oscillation modes of
the neutron star model, and the value of $\delta\sigma/\sigma$ for a given mode
depends on the physical properties of the models. We find that
$|\delta\sigma/\sigma|$ is less than $\sim0.1$ for most of the oscillation
modes we calculate, although there are a few exceptions such as the fundamental
(nodeless) toroidal torsional modes in the crust, the surface gravity modes
confined in the surface ocean, and the core gravity modes trapped in the fluid
core. We also find that the modal properties, represented by the
eigenfunctions, are not strongly affected by introducing general relativity. It
is however shown that the mode characters of the two interfacial modes,
associated with the core/crust and crust/ocean interfaces, have been
interchanged between the two through an avoided crossing when we move from
Newtonian dynamics to general relativistic dynamics.


title:
Revised analysis of the supersoft X-ray phase, helium enrichment, and
  turn-off time in the 2000 outburst of recurrent nova CI Aquilae

abstract:
  Recurrent nova CI Aquilae has entered the final decline phase a bit before
May of 2001, about 300 days after the optical maximum, showing the slowest
evolution among recurrent novae. Based on the optically thick wind mass-loss
theory of the thermonuclear runaway model, we have estimated the turn-off time
of the CI Aql 2000 outburst. It is in late March of 2001 after a luminous
supersoft X-ray source phase lasts 150 days (from November of 2000 until March
of 2001). We have also obtained, by fitting our theoretical light curves with
the 1917 and 2000 outbursts, the white dwarf (WD) mass to be M_{WD}= 1.2 \pm
0.05 M_\sun, the helium enrichment of the envelope is He/H = 0.5 by number, the
mass of the hydrogen-rich envelope on the WD at the optical maximum is \Delta
M_{max} = 8.0 x 10^{-6} M_\sun, and the average mass accretion rate is \dot
M_{acc}= 1.0 x 10^{-7} M_\sun/yr during the quiescent phase between the 1917
and 2000 outbursts. Using these obtained values, we have consistently
reproduced the light curve in quiescence as well as of the two outbursts. We
have also discussed the possibility whether or not CI Aql will explode as a
Type Ia supernova in a future.


title:
Detection of Two Binary Trans-Neptunian Objects, 1997 CQ29 and 2000
  CF105, with the Hubble Space Telescope

abstract:
  Images of the trans-Neptunian objects 1997 CQ29 and 2000 CF105 obtained with
the Hubble Space Telescope's WFPC2 camera show them to be binary. The two
components of 1997 CQ29 were separated in our images by 0.20 arcsec in November
2001 and by 0.33 arcsec in June/July 2002. The corresponding minimum physical
distances are 6100 km and 10,200 km. The companion to 2000 CF105 was 0.78
arcsec from the primary, at least 23,400 km. Six other objects in the
trans-Neptunian region, including Pluto and its moon Charon, are known to be
binaries; 1997 CQ29 and 2000 CF105 are the seventh and eighth known pair.
Binarity appears to be a not-uncommon characteristic in this region of the
solar system, with detectable companions present in 4% of the objects we have
examined.


title:
Clusters in the inner spiral arms of M51: the cluster IMF and the
  formation history

abstract:
  We study the cluster population in a region of 3.2x3.2 kpc^2 in the inner
spiral arms of the intergacting galaxy M51, at a distance of about 1 to 3 kpc
from the nucleus, based on HST--WFPC2 images taken through five broadband and
two narrowband filters. We found 877 cluster candidates and we derived their
ages, initial masses and extinctions by comparing their energy distribution
with the Starburst99 cluster models. We describe the 3 and 2-dimensional
least-square energy fitting method that was used (3DEF, 2DEF). The lack of
[OIII] emission in even the youngest clusters with strong H-alpha emission,
indicates the absence of the most massive stars and suggests a mass upper limit
of about 25 to 30 solar masses. The mass versus age distribution of the
clusters shows a drastic decrease in the number of clusters with age, which
indicates that cluster disruption is occurring on a timescale of about 10 Myr
for low mass clusters. The cluster initial mass function for clusters younger
than 10 Myr has an exponent of alpha = 2.0 (+- 0.05) We derived the cluster
formation history from clusters with an initial mass larger than 10^4 solar
masses. There is no evidence for a peak in the cluster formation rate within a
factor two at about 200 to 400 Myr ago, i.e. at the time of the interaction
with the companion galaxy NGC 5194.


title:
Star Cluster Formation and Disruption Time-Scales -- I. An empirical
  determination of the disruption time of star clusters in four galaxies

abstract:
  We present a new method to derive the cluster disruption time in selected
regions of galaxies from the mass or age distribution of magnitude-limited
cluster samples. If the disruption time of clusters in a region of a galaxy
depends on their initial mass as t_4 x (M_cluster/10^4 M_sun)^gamma and if the
cluster formation rate is constant, then the mass and age distributions of the
observed clusters will each show two powerlaw relations. The values of t_4 and
gamma can be derived from these relations. We used this method to derive the
cluster disruption time in specific regions in four galaxies: the inner region
of M51, a region of M33, the SMC and the solar neighbourhood. The values of
gamma are the same in the four galaxies within the uncertainty and the mean
value is gamma= 0.62 +- 0.06. However the disruption time t_4 of a cluster of
10^4 M_sun is very different in the different galaxies. The clusters in the SMC
have the longest disruption time, t_4 = 8 Gyr, and the clusters at 1 to 3 kpc
from the nucleus of M51 have the shortest disruption time of t_4 = 0.04 Gyr.
The disruption time of clusters 1 to 5 kpc from the nucleus of M33 is t_4 =
0.13 Gyr and for clusters within 1 kpc from the Sun we find t_4 = 1.0 Gyr.


title:
Building up the globular cluster system of the Milky Way. The
  contribution of the Sagittarius galaxy

abstract:
  We demonstrate that there is a clear statistical correlation between the
(X,Y,Z,V_r) phase-space distribution of the outer halo Galactic globular
clusters (having 10 kpc <= R_GC <= 40 kpc) and the orbital path of the
Sagittarius dwarf spheroidal galaxy (Sgr dSph), as derived by Ibata & Lewis. At
least 4 of the sample of 35 globular clusters in this distance range were
formerly members of the Sgr galaxy (at the 95 % confidence level), and are now
distributed along the Sgr Stream, a giant tidal structure that surrounds the
Milky Way. This is the first instance that a statistically significant
structure associated with the Sgr dSph has been detected in the globular
cluster population of the Galactic halo. Together with the four well-known
globular clusters that are located near the center of this tidally-disrupting
dwarf galaxy, these clusters constitute ~ 20 % of the population of outer halo
(R_GC >= 10 kpc) clusters. The Sgr dSph was therefore not only an important
contributor to the halo field star population, but it also had a significant
role in the building-up of the globular cluster system of the Milky Way.


title: Inflationary Dynamics with Runaway Potentials

abstract:
  The evolution of two slow--rolling scalar fields with potentials of the form
$V=V_0 \phi^{-\alpha}\exp(-\beta \phi^m)$ is studied. Considering different
values of the parameters $\alpha$, $\beta$ and $m$, we derive several new
inflationary solutions in which one fields just evolves in the background and
is not important for the inflationary dynamics. In addition, we find new
solutions where both fields are dynamically important during inflation.
Moreover, we discuss the evolution of perturbations in both scalar fields and
the spacetime metric, concentrating on the production of entropy perturbations.
We find that for a large region in parameter space and initial conditions
tensor modes are negligible and that adiabatic and isocurvature perturbations
are essentially uncorrelated.


title:
Stellar Populations and Star Cluster Formation in Interacting Galaxies
  with the Advanced Camera for Surveys

abstract:
  Pixel-by-pixel colour-magnitude and colour-colour diagrams - based on a
subset of the Hubble Space Telescope Advanced Camera for Surveys Early Release
Observations - provide a powerful technique to explore and deduce the star and
star cluster formation histories of the Mice and the Tadpole interacting
galaxies. In each interacting system we find some 40 bright young star clusters
(20 <= F606W (mag) <= 25, with a characteristic mass of ~3 x 10^6 Msun), which
are spatially coincident with blue regions of active star formation in their
tidal tails and spiral arms. We estimate that the main events triggering the
formation of these clusters occurred ~(1.5-2.0) x 10^8 yr ago. We show that
star cluster formation is a major mode of star formation in galaxy
interactions, with >= 35% of the active star formation in encounters occurring
in star clusters. This is the first time that young star clusters have been
detected along the tidal tails in interacting galaxies. The tidal tail of the
Tadpole system is dominated by blue star forming regions, which occupy some 60%
of the total area covered by the tail and contribute ~70% of the total flux in
the F475W filter (decreasing to ~40% in F814W). The remaining pixels in the
tail have colours consistent with those of the main disk. The tidally triggered
burst of star formation in the Mice is of similar strength in both interacting
galaxies, but it has affected only relatively small, spatially coherent areas.


title:
Galaxy Formation: Warm Dark Matter, Missing Satellites, and the Angular
  Momentum Problem

abstract:
  We present warm dark matter (WDM) as a possible solution to the missing
satellites and angular momentum problem in galaxy formation and introduce
improved initial conditions for numerical simulations of WDM models, which
avoid the formation of unphysical haloes found in earlier simulations. There is
a hint, that the mass function of satellite haloes has been overestimated so
far, pointing to higher values for the WDM particle mass.


title: Remarks on the Cosmic Density of Degenerate Neutrinos

abstract:
  We re-investigate the evolution of the strongly degenerate neutrinos in the
early universe. With the larger degeneracy, the neutrino number freezes at
higher temperatures because the neutrino annihilation rate decreases. We
consider very large degeneracy so large that the neutrino number freezes before
events in which the particle degrees of freedom in the universe decrease (e.g.
the muon annihilation and the quark-hadron phase transition). In such a case,
the degeneracy by the time of nucleosynthesis becomes smaller than the initial
degeneracy. We calculate how much it decreases from the initial value on the
basis of the conservation of the neutrino number and the total entropy. We
found a large drop in the degeneracy but it is not large enough to affect the
current constraints on the neutrino degeneracy from BBN and CMBR.


title: Variability-selected quasars behind the Small Magellanic Cloud

abstract:
  We present followup spectroscopic observations of quasar candidates in the
Small Magellanic Cloud selected by Eyer from the OGLE database. Of twelve
observed objects identified as "QSO Candidate", five are confirmed quasars,
with the emission redshifts ranging from 0.28 to 2.16. Two of those quasars
were also recently identified independently in the MACHO database by Geha et
al. We discuss the prospects of using variability-based selection technique for
quasar searches behind other dense stellar fields. An additional criterion
utilizing the color-color diagram should reduce the number of stars in the
candidate lists.


title: Molecular Gas in M82: Resolving the Outflow and Streamers

abstract:
  We present a high-resolution (3.6'', 70pc) CO(1-0) mosaic of the molecular
gas in M 82 covering an area of 2.5' x 3.5' (2.8kpc x 3.9kpc) obtained with the
OVRO millimeter interferometer. The observations reveal the presence of huge
amounts of molecular gas (> 70% of the total molecular mass, M_tot=1.3 x 10^9
M_sun) outside the central 1 kpc disk. Molecular streamers are detected in and
below M82's disk out to distances from the center of 1.7 kpc. Some of these
streamers are well correlated with optical absorption features; they form the
basis of some of the prominent tidal HI features around M 82. This provides
evidence that the molecular gas within M 82's optical disk is disrupted by the
interaction with M 81. Molecular gas is found in M 82's outflow/halo, reaching
distances up to 1.2 kpc below the plane; CO line-splitting has been detected
for the first time in the outflow. The maximum outflow velocity is 230 km/s; we
derive an opening angle of 55 deg for the molecular outflow cone. The total
amount of gas in the outflow is >3 x 10^8 M_sun and its kinetic energy is of
order 10^55 erg, about one percent of the estimated total mechanical energy
input of M 82's starburst. Our study implies that extreme starburst
environments can move significant amounts of molecular gas in to a galaxy's
halo (and even to the intergalactic medium).


title:
Non-Gaussian features of primordial fluctuations in single field
  inflationary models

abstract:
  We compute the three point correlation functions for primordial scalar and
tensor fluctuations in single field inflationary models. We obtain explicit
expressions in the slow roll limit where the answer is given terms of the two
usual slow roll parameters. In a particular limit the three point functions are
determined completely by the tilt of the spectrum of the two point functions.
We also make some remarks on the relation of this computation to dS/CFT and
AdS/CFT. We emphasize that (A)dS/CFT can be viewed as a statement about the
wavefunction of the universe.


title: Weak Lensing Results from the 75 Square Degree CTIO Survey

abstract:
  We measure seeing-corrected ellipticities for 2 x 10^6 galaxies with
magnitude R<23 in 12 widely separated fields totalling 75 deg^2 of sky. At
angular scales >30\arcmin, ellipticity correlations are detected at high
significance and exhibit nearly the pure "E-mode" behavior expected of weak
gravitational lensing. Even when smoothed to the full field size of 2.5
degrees, which is ~25h^-1 Mpc at the lens distances, an rms shear variance of
<\gamma^2>^1/2 = 0.0012 +- 0.0003 is detected. At smaller angular scales there
is significant "B-mode" power, an indication of residual uncorrected PSF
distortions. The >30\arcmin data constrain the power spectrum of matter
fluctuations on comoving scales of ~10h^-1 Mpc to have \sigma_8
(\Omega_m/0.3)^{0.57} = 0.71^{+0.12}_{-0.16} (95% CL, \LambdaCDM, \Gamma=0.21),
where the systematic error includes statistical and calibration uncertainties,
cosmic variance, and a conservative estimate of systematic contamination based
upon the detected B-mode signal. This normalization of the power spectrum is
lower than previous weak-lensing results but generally consistent them, is at
the lower end of the \sigma_8 range from various analyses of galaxy cluster
abundances, and agrees with recent determinations from CMB and galaxy
clustering.
  The large and dispersed sky coverage of our survey reduces random errors and
cosmic variance, while the relatively shallow depth allows us to use existing
redshift-survey data to reduce systematic uncertainties in the N(z)
distribution to insignificance. Reanalysis of the data with more sophisticated
algorithms will hopefully reduce the systematic (B-mode) contamination, and
allow more precise, multidimensional constraint of cosmological parameters.


title: A Detailed Thermal Analysis of the Binospec Spectrograph

abstract:
  Refractive optics in astronomical instruments are potentially sensitive to
temperature gradients and temperature transients. This sensitivity arises from
thermally dependent refractive indices, lens spacings, and lens dimensions. We
have therefore undertaken a detailed thermal analysis of Binospec, a wide-field
optical spectrograph under development for the converted MMT. Our goals are to
predict the temperature gradients that will be present in the Binospec optics
and structure under realistic operating conditions and to determine how design
choices affect these gradients. We begin our analysis by deriving thermal time
constants for instrument subassemblies. We then generate a low-resolution
finite difference model of the entire instrument and high-resolution models of
sensitive subassemblies. This approach to thermal analysis is applicable to a
variety of other instruments. We use measurements of the ambient temperature in
the converted MMT's dome to model Binospec's thermal environment. During
moderate conditions we find that the Binospec lens groups develop 0.14 C axial
and radial temperature gradients and that lens groups of different mass develop
0.5 C temperature differences; these numbers are doubled for the extreme
conditions. Internal heat sources do not significantly affect these results;
heat flow from the environment dominates. The instrument must be periodically
opened to insert new aperture masks, but we find that the resulting temperature
gradients and thermal stresses in the optics are small. Image shifts at the
detector caused by thermal deflections of the Binospec optical bench structure
are approx 0.1 pixel/hr. We conclude that the proposed Binospec design has
acceptable thermal properties, and briefly discuss design changes to further
reduce temperature gradients.


title:
The Inflationary Gravity Waves in light of recent Cosmic Microwave
  Background Anisotropies data

abstract:
  One of the major predictions of inflation is the existence of a stochastic
background of cosmological gravitational waves (GW). These gravitational waves
can induce significant temperature anisotropies in the Cosmic Microwave
Background (CMB) on the angular scales recently probed by the Archeops
experiment. Here, we perform a combined analysis of Archeops together with
information from other CMB experiments and/or cosmological datasets, in order
to constrain the amplitude of the GW background. We find that, for a
scale-invariant GW background, the ratio of tensor/scalar perturbations at the
CMB quadrupole is now constrained to be $r \leq 0.43$ at 95% c.l., while the
bound on the spectral index of primordial density fluctuations is
$n_S=0.97_{-0.12}^{+0.10}$. We discuss the implications for future GW
detections through CMB polarization measurements.


title:
The Masses Of The B-Stars In The High Galactic Latitude Eclipsing Binary
  IT Lib

abstract:
  A number of blue stars which appear to be similar to Population I B-stars in
the star forming regions of the galactic disk are found more than 1 kpc from
the galactic plane. Uncertainties about the true distances and masses of these
high latitude B-stars has fueled a debate as to their origin and evolutionary
status. The eclipsing binary IT Lib is composed of two B-stars, is
approximately one kiloparsec above the galactic plane, and is moving back
toward the plane. Observations of the light and velocity curves presented here
lead to the conclusion that the B-stars in this system are massive young
main-sequence stars. While there are several possible explanations, it appears
most plausible that the IT Lib system formed in the disk about 30 million years
ago and was ejected on a trajectory taking it to its present position.


title:
A Chandra and XMM View of the Mass & Metals in Galaxy Groups and
  Clusters

abstract:
  X-ray observations with Chandra and XMM are providing valuable new
measurements of the baryonic and dark matter content of groups and clusters.
Masses of cD clusters obtained from X-ray and gravitational lensing studies
generally show good agreement, therefore providing important validation of both
methods. Gas fractions have been obtained for several clusters that verify
previous results for a low matter density (Omega_m ~0.3). Chandra has also
provided measurements of the mass profiles deep down into several cluster cores
and has generally found no significant deviations from CDM predictions in
contrast to the flat core density profiles inferred from the rotation curves of
low-surface brightness galaxies and dwarf galaxies; i.e., there is no evidence
for self-interacting dark matter in cluster cores. Finally, initial studies of
the iron and silicon abundances in centrally E-dominated groups show that they
have pronounced gradients from 1-2 solar values within the central 30-50 kpc
that fall to values of 0.3-0.5 solar at larger radii. The Si/Fe ratios are
consistent with approximately 80% of the metals originating from Type Ia
supernovae. Several cD clusters also display central Fe enhancements suggestive
of Type Ia supernova enrichment, though some have central dips that may provide
a vital clue for solving the cooling flow mystery.


title:
Chandra X-Ray Spectroscopy and Imaging of the Galaxy Cluster PKS
  0745-191

abstract:
  We present a detailed spectral and spatial analysis of the galaxy cluster PKS
0745-191, using recent observations from the Chandra X-ray Observatory. The
data provide information on the temperature and metallicity of the intracluster
medium, the distribution of emission throughout the cluster, morphology of the
cluster core, and an independent mass estimate which can be compared to that
from gravitational lensing. X-ray spectra extracted from the central 300 kpc
(~2 arcmin) are well described by a two-temperature plasma and the mean cluster
temperature is consistent with previously determined values. The distribution
of both temperature and metallicity within the inner 360 kpc (2.3 arcmin) of
PKS 0745-191 is probed on scales of 8 arcsec (~20 kpc), yielding a relatively
constant abundance throughout the region and a strong temperature gradient
(down to ~4-5 keV) within the central 215 kpc. Beta-model fits to the surface
brightness profile of PKS 0745-191 indicate that a second beta-model component
is required to fit the inner ~10 kpc. Imaging analysis of the cluster core
reveals an irregular morphology within the inner 50 kpc, and confirms that the
X-ray emission peak lies within 0.5 arcsec (the spatial resolution of Chandra)
of both the optical and radio central cD positions. The cluster mass, based on
both two temperature and multiphase fits to the X-ray spectrum, is in close
agreement with lensing mass estimates of PKS-0745-191.


title:
Soft X-ray excess emission in clusters of galaxies observed with
  XMM-Newton

abstract:
  We present results on the spectroscopic analysis of XMM-Newton EPIC data of
the central 0.5/h_50 Mpc regions of the clusters of galaxies Coma, A1795 and
A3112. The temperature of the hot intracluster gas as determined by modeling
the 2 - 7 keV PN and MOS data is consistent with that inferred from the
FeXXV-FeXXVI line ratio. A significant warm emission component at a level above
the systematic uncertainties is evident in the data and confirmed by ROSAT PSPC
data for Coma and A1795. The non-thermal origin of the phenomenon cannot be
ruled out at the current level of calibration accuracy, but the thermal model
fits the data significantly better, with temperatures in the range of 0.6 --
1.3 keV and electron densities of the order of 10^{-4} -- 10^{-3} cm^{-3}. In
the outer parts of the clusters the properties of the warm component are
marginally consistent with the results of recent cosmological simulations,
which predict a large fraction of the current epoch's bayons located in a
warm-hot intergalactic medium (WHIM). However, the derived densities are too
high in the cluster cores, compared to WHIM simulations, and thus more
theoretical work is needed to fully understand the origin of the observed soft
X-ray excess.


title: A Primer on Eulerian Computational Fluid Dynamics for Astrophysics

abstract:
  We present a pedagogical review of some of the methods employed in Eulerian
computational fluid dynamics (CFD). Fluid mechanics is governed by the Euler
equations, which are conservation laws for mass, momentum, and energy. The
standard approach to Eulerian CFD is to divide space into finite volumes or
cells and store the cell-averaged values of conserved hydro quantities. The
integral Euler equations are then solved by computing the flux of the mass,
momentum, and energy across cell boundaries. We review both first-order and
second-order flux assignment schemes. All linear schemes are either dispersive
or diffusive. The nonlinear, second-order accurate total variation diminishing
(TVD) approach provides high resolution capturing of shocks and prevents
unphysical oscillations. We review the relaxing TVD scheme, a simple and robust
method to solve systems of conservation laws like the Euler equations.
  A 3-D relaxing TVD code is applied to the Sedov-Taylor blast wave test. The
propagation of the blast wave is accurately captured and the shock front is
sharply resolved. We apply a 3-D self-gravitating hydro code to simulating the
formation of blue straggler stars through stellar mergers and present some
numerical results. A sample 3-D relaxing TVD code is provided in the appendix.


title:
Infrared Observations During the Secondary Eclipse of HD 209458b: I.
  3.6-Micron Occultation Spectroscopy Using the VLT

abstract:
  We search for an infrared signature of the transiting extrasolar planet HD
209458b during secondary eclipse. Our method, which we call `occultation
spectroscopy,' searches for the disappearance and reappearance of weak spectral
features due to the exoplanet as it passes behind the star and later reappears.
We argue that at the longest infrared wavelengths, this technique becomes
preferable to conventional `transit spectroscopy'. We observed the system in
the wing of the strong nu-3 band of methane near 3.6 microns during two
secondary eclipses, using the VLT/ISAAC spectrometer at a spectral resolution
of 3300. Our analysis, which utilizes a model template spectrum, achieves
sufficient precision to expect detection of the spectral structure predicted by
an irradiated, low-opacity (cloudless), low-albedo, thermochemical equilibrium
model for the exoplanet atmosphere. However, our observations show no evidence
for the presence of this spectrum from the exoplanet, with the statistical
significance of the non-detection depending on the timing of the secondary
eclipse, which depends on the assumed value for the orbital eccentricity. Our
results reject certain specific models of the atmosphere of HD 209458b as
inconsistent with our observations at the 3-sigma level, given assumptions
about the stellar and planetary parameters.


title:
NMA CO (J=1-0) Observations of the Halpha/Radio Lobe Galaxy NGC 3079:
  Gas Dynamics in a Weak Bar Potential and Central Massive Core

abstract:
  within 24 lines with 80 characters) We present ^12CO (1-0) observations in
the central 4.5 kpc (1 arcmin) of the Halpha/Radio lobe galaxy NGC 3079 with
the Nobeyama Millimeter Array. The molecular gas shows four components: a main
disk, spiral arms, a nuclear disk, and a nuclear core. The main disk extends
beyond our spatial coverage. The spiral arms are superimposed on the main disk.
The nuclear disk with about 600 pc radius has an intense concentration of
molecular gas. Its appearance on PV diagrams is indicative of oval motions of
the gas, rather than circular. The nuclear core is more compact than our
resolution. Though it is unresolved, the nuclear core shows a very high
velocity about 200 km/s even at the radius of about 100 pc on the PV diagram.
We propose a model that NGC 3079 contains a weak bar. This model explains the
observed features: the main disk and spiral arms result from gaseous x1-orbits
and associated crowding respectively. The nuclear disk arises from gaseous
x2-orbits. From the appearance of the spiral arms on the PV diagram, the
pattern speed of the bar is estimated to be 55+-10 km/s/kpc. The high velocity
of the nuclear core cannot be explained by our model for a bar. Thus we
attribute it to a central massive core with a dynamical mass of 10^9 Msun
within the central 100 pc. This mass is three orders of magnitude more massive
than that of a central black hole in this galaxy.


title:
Intrinsic errors of the central galactic mass derived from rotation
  curves under the influence of a weak non-axisymmetric potential

abstract:
  Rotation curves are often used to estimate the mass distribution of spiral
galaxies, assuming circular rotation of disks. However, non-circular motions
caused by a non-axisymmetric gravitational potential, such as a stellar bar,
may disturb the velocity field, resulting in errors in mass estimation,
especially in the central regions of galaxies, because the line-of-sight
velocity depends on the viewing angles in a non-axisymmetric flow. Observing
rotation curves of edge-on galaxies in time-dependent numerical simulations
from different viewing angles, we obtain errors in the estimation of galactic
mass from the rotation curves. In the most extreme case, the ellipticity of gas
orbits is as high as 0.8 in the central regions, even if the bar potential is
weak. When rotation curves are defined as the highest velocity envelope of
position-velocity diagrams, the mass estimated from the rotation curves is
larger than the true mass by a factor of five for 15% of the viewing angles,
and the ratio between the apparent mass and true mass is less than six for any
viewing angle. The overestimation in mass occurs more frequently than the
underestimation.


title: High Resolution \hi observations of the Western Magellanic Bridge

abstract:
  The 21cm line emission from a 7x6 degree region, east of and adjoining the
Small Magellanic Cloud (SMC) has been observed with the Australia Telescope
Compact Array and the Parkes telescopes. This region represents the westernmost
part of the Magellanic Bridge, a gas-rich tail extending ~14 degrees to the
Large Magellanic Cloud (LMC). A rich and complex neutral hydrogen (HI)
structure containing shells, bubbles and filaments is revealed. On the larger
scale, the HI of the Bridge is organised into two velocity components. This
bimodality, which appears to originate in the SMC, converges to a single
velocity component within the observed region. A census of shell-like
structures suggests a shell population with characteristics similar to that of
the SMC. The mean kinematic age of the shells is ~6 Myr, in agreement with the
SMC shell population, but not with ages of OB clusters populating the
Magellanic Bridge, which are approximately an factor of three older. In
general, the projected spatial correlation of Bridge HI shells with OB
associations is poor and as such, there does not appear to be a convincing
relationship between the positions of OB associations and that of expanding
spherical HI structures. This survey has found only one HI shell that has an
identifiable association with a known Ha shell. The origin of the expanding
structures is therefore generally still uncertain, although current theories
regarding their formation include gravitational and pressure instabilities, HVC
collisions and ram pressure effects.


title: The r'-band luminosity function of Abell1367: a comparison with Coma

abstract:
  We made a large (approximately 1degr x 1degr) r'-band imaging survey of the
central regions of the two nearby clusters of galaxies, Abell1367 and Coma. The
data, presented as a catalog, are used to construct the r'-band luminosity
function (LF) of galaxies in these two clusters, by subtracting the Yasuda et
al. (2001) galaxy counts from our cluster counts. Our Coma luminosity function
is consistent with previous determinations, i.e. providing a faint end slope
alpha = -1.47_-0.09^+0.08, significantly steeper than the one we find for
Abell1367 (alpha = -1.07_-0.16^+0.20). The counts in Abell1367 show a relative
minimum at r' ~ 19, followed by a steep increase faintward. The difference
between the two clusters appears significant, given the consistency of the
experimental conditions in the two clusters. Whereas for Coma we find a
significant increase of the slope of the LF outwards, no such effect is found
for Abell1367.


title:
Limits on Supersymmetric Dark Matter From EGRET Observations of the
  Galactic Center Region

abstract:
  In most supersymmetic models, neutralino dark matter particles are predicted
to accumulate in the Galactic center and annihilate generating, among other
products, gamma rays. The EGRET experiment has made observations in this
region, and is sensitive to gamma rays from 30 MeV to $\sim$30 GeV. We have
used an improved point source analysis including an energy dependent point
spread function and an unbinned maximum likelihood technique, which has allowed
us to significantly lower the limits on gamma ray flux from the Galactic
center. We find that the present EGRET data can limit many supersymmetric
models if the density of the Galactic dark matter halo is cuspy or spiked
toward the Galactic center. We also discuss the ability of GLAST to test these
models.


title:
An efficient shock-capturing central-type scheme for multidimensional
  relativistic flows. II. Magnetohydrodynamics

abstract:
  A third order shock-capturing numerical scheme for three-dimensional special
relativistic magnetohydrodynamics (3-D RMHD) is presented and validated against
several numerical tests. The simple and efficient central scheme described in
Paper I (Del Zanna and Bucciantini, Astron. Astrophys., 390, 1177--1186, 2002)
for relativistic hydrodynamics is here extended to the magnetic case by
following the strategies prescribed for classical MHD by Londrillo and Del
Zanna (Astrophys. J., 530, 508--524, 2000). The scheme avoids completely
spectral decomposition into characteristic waves, computationally expensive and
subject to many degenerate cases in the magnetic case, while it makes use of a
two-speed Riemann solver that just require the knowledge of the two local fast
magnetosonic velocities. Moreover, the onset of spurious magnetic monopoles,
which is a typical problem for multi-dimensional MHD upwind codes, is prevented
by properly taking into account the solenoidal constraint and the specific
antisymmetric nature of the induction equation. Finally, the extension to
generalized orthogonal curvilinear coordinate systems is included, thus the
scheme is ready to incorporate general relativistic (GRMHD) effects.


title:
Extremely metal-poor Lyman limit system at z = 2.917 toward the quasar
  HE 0940-1050

abstract:
  We report on detailed Monte Carlo inversion analysis of the Lyman limit
system observed at z = 2.917 in the VLT/UVES spectrum of the quasar HE
0940-1050. Metal absorption lines of carbon and silicon in three ionization
stages and numerous atomic hydrogen lines have been analyzed simultaneously. It
is found that in order to match the observations, the shape of the ultraviolet
background ionizing spectrum of Haardt & Madau (1996) should be modified: a
spectrum with a higher intensity of the emission feature at 3 Ryd is required.
It is also found that synthetic galactic spectra (or different mixtures of them
with power law spectra) cannot reproduce the observations, indicating that the
stellar contribution to the ionizing background is negligible at z ~= 3. For
the first time a very low carbon abundance of [C/H] = -2.93+/-0.13 and the
abundance ratio [Si/C] = 0.35+/-0.15 are directly measured in the Lyman limit
system with N(H I) = 3.2 10^{17} cm^{-2}. If the absorber at z = 2.917 provides
an example of a pristine gas enriched by the nucleosynthetic products of early
generations of stars, then the measured value of [Si/C] seems to indicate that
the initial mass functions for these stellar populations are constrained to
intermediate masses, M_up <= 25M_solar.


title: Deep Searches for Young Pulsars

abstract:
  By 2000 there were only 10 established Galactic pulsar-supernova remnant
associations. Two years later there are 16 such associations known. I discuss
the work leading to this substantial increase. In particular I summarize an
ongoing search project that has resulted in the detection of several young
pulsars with a very low radio luminosity of about 1 mJy kpc^2 at 1.4 GHz, and
comment on future prospects.


title: Search for double degenerate progenitors of supernovae type Ia with SPY

abstract:
  We report on a large survey for double degenerate (DD) binaries as potential
progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (SN
Ia Progenitor surveY - SPY). About 560 white dwarfs were checked for radial
velocity variations until now. Ninety new DDs have been discovered, including
short period systems with masses close to the Chandrasekhar mass.


title:
Characterising Extrasolar Planets in Reflected Light and Thermal
  Emission

abstract:
  The physical bases of the detection and characterisation of extrasolar
planets in the reflected light and thermal emission regimes are reviewed. They
both have their advantages and disadvantages, including artefacts, in the
determination of planet physical parameters (mass, size, albedo, surface and
atmospheric conditions etc. A special attention is paid for Earth-like planets
and new perspectives for these different aspects are also presented.


title:
X-ray and radio bright type Ic SN 2002ap -- a hypernova without an
  associated GRB

abstract:
  Combined X-ray (0.3 -10 keV) and Radio (0.61 and 1.42 GHz) observations of
the type Ic SN 2002ap are used here, to determine the origins of the prompt
X-ray and Radio emission from this source.Our analysis of the XMM-Newton
observations suggests that the prompt X-ray emission originates from inverse
Compton scattering of photospheric thermal emission by energetic electrons. We
also compare the early radiospheric properties of SN 2002ap with those of SN
1998bw (type Ic) and SN 1993J (type IIb), to contrast the prompt emission from
a GRB associated SN with other supernovae without GRB counterparts.


title:
Carbon-Oxygen White Dwarfs Accreting CO-Rich Matter I: A Comparison
  Between Rotating and Non-Rotating Models

abstract:
  We investigate the lifting effect of rotation on the thermal evolution of CO
WDs accreting CO-rich matter. We find that rotation induces the cooling of the
accreting star so that the delivered gravitational energy causes a greater
expansion with respect to the standard non-rotating case. The increase in the
surface radius produces a decrease in the surface value of the critical angular
velocity and, therefore, the accreting WD becomes gravitationally unbound
(Roche instability). This occurrence is due to an increase in the total angular
momentum of the accreting WD and depends critically on the amount of specific
angular momentum deposited by the accreted matter. If the specific angular
momentum of the accreted matter is equal to that of the outer layers of the
accreting structure, the Roche instability occurs well before the accreting WD
can attain the physical conditions for C-burning. If the values of both initial
angular velocity and accretion rate are small, we find that the accreting WD
undergoes a secular instability when its total mass approaches 1.4 Msun. At
this stage, the ratio between the rotational and the gravitational binding
energy of the WD becomes of the order of 0.1, so that the star must deform by
adopting an elliptical shape. In this case, since the angular velocity of the
WD is as large as 1 rad/s, the anisotropic mass distribution induces the loss
of rotational energy and angular momentum via GWR. We find that, independent of
the braking efficiency, the WD contracts and achieves the physical conditions
suitable for explosive C-burning at the center so that a type Ia supernova
event is produced.


title:
A Strongly Nonlinear Alfvenic Pulse in a Transversely Inhomogeneous
  Medium

abstract:
  We investigate the interaction of a plane, linearly polarized, Alfvenic pulse
with a one-dimensional, perpendicular to the magnetic field, plasma density
inhomogeneity in the strongly nonlinear regime. Our numerical study of the full
MHD equations shows that: (i) Plasma density inhomogeneity substantially
enhances (by about a factor of 2) the generation of longitudinal compressive
waves. (ii) Attained maximal values of the generated transverse compressive
perturbations are insensitive to the strength of the plasma density
inhomogeneity, plasma beta and the initial amplitude of the Alfven wave.
Typically, they reach about 40% of the initial Alfven wave amplitude. (iii)
Attained maximal values of the generated relative density perturbations are
within 20-40% for 0.5 <= beta <= 2.0. They depend upon plasma beta strongly;
and scale almost linearly with the initial Alfven wave amplitude.


title:
Time Series Photometry of Variable Stars in the Globular Cluster NGC
  6397

abstract:
  Time series BVI photometry is presented for 16 short-period variables located
in the central region of the globular cluster NGC 6397. The sample includes 9
newly detected variables. The light curve of cataclysmic variable CV6 shows
variability with a period of 0.2356 days. We confirm an earlier reported period
of 0.472 days for cataclysmic variable CV1. Phased light curves of both CVs
exhibit sine-like light curves, with two minima occurring during each orbital
cycle. The secondary component of CV1 has a low average density of 0.83
g/cm^{3} indicating that it cannot be a normal main sequence star. Variables
among the cluster blue stragglers include a likely detached eclipsing binary
with orbital period of 0.787 days, three new SX Phe stars (one of which has the
extremely short period of 0.0215 days), and three low amplitude variables which
are possible gamma Doradus variables.


title: The radiant of the Leonids meteor storm in 2001

abstract:
  We have measured the radiant of the Leonids meteor storm in November 2001 by
using new observational and analysis techniques. The radiant was measured as
the intersections of lines which were detected and extrapolated from images
obtained at a single observing site (Akeno Observatory, Japan). The images were
obtained by two sets of telephoto lenses equipped with cooled CCD cameras. The
measured radiant, (R.A., Dec.)=(154$^\circ$.35, 21$^\circ$.55) (J2000), is
found to be in reasonable agreement with the theoretical prediction by McNaught
and Asher (2001), which verifies their dust trail theory.


title:
Vertical distribution of Galactic disk stars I - Kinematics and
  metallicity

abstract:
  Nearly 400 Tycho-2 stars have been observed in a 720 square degree field in
the direction of the North Galactic Pole with the high resolution echelle
spectrograph ELODIE. Absolute magnitudes, effective temperatures, gravities and
metallicities have been estimated, as well as distances and 3D velocities. Most
of these stars are clump giants and span typical distances from 200pc to 800pc
to the galactic mid-plane. This new sample, free of any kinematical and
metallicity bias, is used to investigate the vertical distribution of disk
stars. The old thin disk and thick disk populations are deconvolved from the
velocity-metallicity distribution of the sample and their parameters are
determined. The thick disk is found to have a moderate rotational lag of -51+-5
km/s with respect to the Sun with velocity ellipsoid (sigma_U, sigma_V,
sigma_W)=(63+-6, 39+-4, 39+-4) km/s, mean metallicity of [Fe/H]=-0.48+-0.05 and
a high local normalization of 15+-7%. Combining this NGP sample with a local
sample of giant stars from the Hipparcos catalogue, the orientation of the
velocity ellipsoid is investigated as a function of distance to the plane and
metallicity. We find no vertex deviation for old stars, consistent with an
axisymmetric Galaxy. Paper II is devoted to the dynamical analysis of the
sample, puting new constraints on the vertical force perpendicular to the
galactic plane and on the total mass density in the galactic plane.


title: Globular Cluster Systems of Spirals

abstract:
  Recent observational results on the globular cluster systems of spiral
galaxies are summarized. Although the number of spirals with well-studied GCSs
is still small, new studies promise to increase it rapidly in the next few
years. New telescopes and technology have contributed to increasingly detailed
studies of GCs in Local Group galaxies like M31 and M33, and more distant
spirals like M81 and M104 are finally getting the attention they deserve. The
Milky Way GCS looks to be reasonably typical of spirals, and still has a lot to
tell us about the history of the galaxy.


title: Angular Distribution of Gamma-ray Bursts and Weak Lensing

abstract:
  We investigate whether Gamma-Ray Bursts (GRBs) from the Current BATSE Catalog
have been affected by weak lensing by the nearby large scale structure. The
redshift distribution of GRBs is believed to be broad, extending to z~5, so
most events can be assumed to be at large redshifts, and hence subject to weak
lensing, which would betray itself as projected (anti-)correlations between GRB
events and galaxies or clusters that trace the intervening mass. Given the
observed distribution of GRBs in fluence, and statistical positional error, e,
we predict that most subsets drawn from BATSE Catalog will be anti-correlated
with the foreground structure due to weak lensing, i.e. will show negative
magnification bias. We find that GRBs are indeed anti-correlated with the APM
galaxies (z~0.2-0.3) in the sense that galaxy density in circles of radii 1-1.5
deg (15-20 Mpc at z~0.3) centered on e<1 GRBs is about 10% lower than expected
from a random distribution; the significance of GRB-APM anti-correlations
reaches 99.7%. Cross-correlation between GRBs and distant rich
Abell-Corwin-Olowin clusters is also negative. Standard cosmological models
with Omega_matter ~ 0.3, Omega_Lambda ~ 0.7, and matter distribution on large
scales following observed APM galaxy distribution with the biasing parameter of
around 1 are not able to reproduce our GRB-APM anti-correlations. We propose a
speculative model that does account for these anti-correlations as well as
positive correlations found previously, between QSOs and APM galaxies. We
briefly discuss if the proposed scheme is in conflict with observations of
cosmic microwave background, galaxy surveys, cosmic velocity flows, and weak
shear lensing.


title: Variability in GRB Afterglows and GRB 021004

abstract:
  We present general analytic expressions for GRB afterglow light curves
arising from a variable external density profile and/or a variable energy in
the blast wave. The former could arise from a clumpy ISM or a variable stellar
wind; The latter could arise from refreshed shocks or from an angular dependent
jet structure (patchy shell). Both scenarios would lead to a variable light
curve. Our formalism enables us to invert the observed light curve and obtain
possible density or energy profiles. The optical afterglow of GRB 021004 was
detected 537 seconds AB (after the burst) (Fox et al. 2002). Extensive follow
up observations revealed a significant temporal variability. We apply our
formalism to the R-band light curve of GRB 021004 and we find that several
models provide a good fit to the data. We consider the patchy shell model with
$p=2.2$ as the most likely explanation. According to this model our line of
sight was towards a "cold spot" that has lead to a relativity low $\gamma$-ray
flux and an initially weak afterglow (while the X-ray afterglow flux after a
day was above average). Observations above the cooling frequency, $\nu_c$,
could provide the best way to distinguish between our different models.


title: Dust Formation Events in Colliding Winds: an application to eta Car

abstract:
  Recent IR observations indicate that many massive binary systems present dust
formation episodes, in regions close to the stars, during the periastron
passage. These systems are known to be high-energy sources, and it is believed
that wind collisions are the origin of the emission. In this work we show that
wind collisions not only increase the X-ray emission but also allow dust
formation. As an application we study eta Car, which presents, near periastron,
an increase in the X-ray emission followed by a sudden decrease that lasts for
about a month. We reproduce this feature calculating the optical depth due to
dust formation along the orbital period.


title: Reverberation Mapping of High-Redshift, High-Luminosity Quasars

abstract:
  We present preliminary results from a reverberation mapping program to
measure the Broad Line Region size in high-redshift, high-luminosity quasars.
The observations are carried out at the Hobby-Eberly Telescope and at the Wise
Observatory. The data cover 8 yr of photometric monitoring of 11 quasars, and
2.5 yr of spectrophotometric monitoring of 7 of these sources. Thus far we
detected continuum variations but no line variations. We find that the continua
of the high-luminosity quasars have smaller variability amplitudes and longer
variability timescales compared with low-luminosity AGNs.


title:
Stability of Standing Accretion Shocks, With an Eye Toward Core Collapse
  Supernovae

abstract:
  We examine the stability of standing, spherical accretion shocks. Accretion
shocks arise in core collapse supernovae (the focus of this paper), star
formation, and accreting white dwarfs and neutron stars. We present a simple
analytic model and use time-dependent hydrodynamics simulations to show that
this solution is stable to radial perturbations. In two dimensions we show that
small perturbations to a spherical shock front can lead to rapid growth of
turbulence behind the shock, driven by the injection of vorticity from the now
non-spherical shock. We discuss the ramifications this instability may have for
the supernova mechanism.


title: Stellar population gradients in Seyfert 2 galaxies. Northern sample

abstract:
  We use high signal-to-noise ratio long-slit spectra in the 3600-4700A range
of the twenty brightest northern Seyfert 2 galaxies to study the variation of
the stellar population properties as a function of distance from the nucleus.
In order to characterize the stellar population and other continuum sources
(e.g. featureless continuum FC) we have measured equivalent widths Ws of six
absorption features, four continuum colours and their radial variations, and
performed spectral population synthesis as a function of distance from the
nucleus. About half the sample has CaIIK and G-band W values smaller at the
nucleus than at 1 kpc from it, due to a younger population and/or FC. The
stellar population synthesis shows that, while at the nucleus, 75% of the
galaxies present contribution > 20% of ages younger or equal than 100Myr and/or
of a FC, this proportion decreases to 45% at 3 kpc. In particular, 55% of the
galaxies have contribution > 10% of the 3 Myr/FC component (a degenerate
component in which one cannot separate what is due to a FC or to a 3 Myr
stellar population) at the nucleus, but only 25% of them have this contribution
at 3 kpc. As reference, the stellar population of 10 non-Seyfert galaxies,
spanning the Hubble types of the Seyfert (from S0 to Sc) was also studied. A
comparison between the stellar population of the Seyferts and that of the
non-Seyferts shows systematic differences: the contribution of ages younger
than 1 Gyr is in most cases larger in the Seyfert galaxies than in
non-Seyferts, not only at the nucleus but up to 1 kpc from it.


title: Oblique Polarization Structures in AGN and QSO Radio Jets

abstract:
  We interpret the linear polarization structures observed in extragalactic
radio sources, even those oriented at oblique angles to the jet flows, to be
due to oblique, relativistic shock fronts in the emitting regions. Many sources
exhibit indications of such oblique structures, and the goal of this
investigation is to test this hypothesis quantitatively. A selected group of
ten highly-variable extragalactic sources were observed with the VLBA at 15 and
43 GHz, on nine epochs spanning a 30-month period; five of these objects were
also observed at 8.0 and 22 GHz. The integrated total flux densities and linear
polarizations of the selected objects were also observed several times a month
at 4.8, 8.0 and 14.5 GHz with the University of Michigan 26-meter telescope.
All objects exhibited variability with several exhibiting more than one
independent outburst during the period. We show the evolution of the polarized
components with time and discuss the relativistic shock parameters required to
match the observed polarization structures. Even cases where the magnetic field
is apparently oriented along the jet flow can be fit by oblique shock models
when relativistic aberration effects are included.


title:
Neutron Star Masses from Arecibo Timing Observations of Five
  Pulsar-White Dwarf Binary Systems

abstract:
  We have detected relativistic and/or kinematic post-Keplerian parameters of
no fewer than five pulsar-white dwarf binary systems in long-term timing
observations at Arecibo. We discuss the resulting constraints on pulsar and
companion masses. The general trend is that the pulsar mass measurements are
compatible with the canonical value of 1.35 solar masses, but in most cases
somewhat higher masses are preferred.


title: High energy cosmic-rays from gamma-ray burst sources: A stronger case

abstract:
  The suggested association between the sources of gamma-ray bursts (GRB's) and
the sources of ultra-high energy cosmic rays (UHECR's) is based on two
arguments: (i) The average energy generation rate of UHECR's is similar to the
gamma-ray generation rate of GRB's, and (ii) The constraints that UHECR sources
must satisfy to allow proton acceleration to >10^{20} eV are similar to those
inferred for GRB sources from gamma-ray observations. We show that recent GRB
and UHECR observations strengthen both arguments, and hence strengthen the
suggested association.


title: Masses of Black Holes in Active Galactic Nuclei

abstract:
  We present a progress report on a project whose goal is to improve both the
precision and accuracy of everberation-based black-hole masses. Reverberation
masses appear to be accurate to a factor of about three, and the black-hole
mass/bulge velocity dispersion relationship appears to be the same in active
and quiescent galaxies.


title: Did the dark energy always have a large Compton wavelength?

abstract:
  Until now all well-studied dark energy models proposed have very large
Compton wavelengths, $\lambda_c > 100 Mpc$ at all time and hence show no
clustering on small scales. Evidence against this would disfavour both
$\Lambda$CDM and quintessence. We show however, that large $\lambda_c$ is
actually favoured by current CMB, LSS and SN1a data by comparing quintessence
with a condensate scenario with the same background dynamics. The condensate
scenario has a very small $\lambda_c$ before making a transition to negative
pressure and large $\lambda_c$ and therefore exhibits a rich CMB phenomenology
which roughly interpolates between $\Lambda$CDM and flat CDM models.


title:
A Limit on the Cosmological Mass Density and Power Spectrum from the
  Rotation Curves of Low Surface Brightness Galaxies

abstract:
  The concentrations of the cuspy dark matter halos predicted by simulations of
cold dark matter are related to the cosmology in which the halos form.
Observational constraints on halo concentration therefore map into constraints
on cosmological parameters. In order to explain the observed concentrations of
dark matter dominated low surface brightness galaxies, we require a cosmology
with rather little power on galaxy scales. Formally, we require s_8 G_0.6 <
0.23, where G_0.6 is a modified shape parameter appropriate to this problem.
Practically, this means either Omega_m < 0.2 or s_8 < 0.8. These limits apply
as long as we insist that the cuspy halos found in simulations must describe
the halos of low surface brightness galaxies. A low density cosmology helps
with the low observed concentrations, but it offers no explanation of the many
cases where the shape of the density profile deviates from the predicted cuspy
form. These cases must have suffered very extensive mass redistribution if the
current halo formation picture is not to fail outright. It is far from clear
whether any of the mass redistribution mechanisms which have been suggested
(e.g., feedback) are viable.