title: VLBI observations in Cluster-Cluster mode at 1.6 GHz

abstract:
  We describe, and present preliminary results from the analysis of 1.6 GHz
VLBI observations, made in Cluster-Cluster mode between subgroups of antennas
from the WSRT, VLA and MERLIN arrays. We observed for two 6-hour periods on
consecutive days, simultaneously monitoring 4 compact radio sources with
angular separations ranging from ~1 to 9 degrees. The data were recorded in a
non-standard MkIII mode using special set-ups, and correlated at the MPIfR
MkIIIa correlator. The preliminary results from standard and phase reference
analyses are very encouraging. The experiment has provided a useful database
for investigating the potential of this new observing technique at low
frequencies.


title: Using M32 to Study Rapid Phases of Stellar Evolution

abstract:
  The compact elliptical galaxy M32 offers a unique testing ground for theories
of stellar evolution. Because of its proximity, solar-blind UV observations can
resolve the hot evolved stars in its center. Some of these late evolutionary
phases are too rapid to study adequately in globular clusters, and their study
in the Galactic field is often complicated by uncertainties in distance and
reddening. Using the UV cameras on the Space Telescope Imaging Spectrograph, we
have obtained a deep color-magnitude diagram (CMD) of the M32 center. Although
the hot horizontal branch is well-detected, our CMD shows a striking scarcity
of the brighter post-asymptotic giant branch (PAGB) and post-early AGB stars
expected for a population of this size. This dearth suggests that the evolution
to the white dwarf phase may be much more rapid than that predicted by
canonical evolutionary tracks for low-mass stars.


title:
100 Times Faster and 3 Times Sharper: Background-Dominated Observations
  of Stellar Populations with an 8-meter Optical-UV Space Telescope

abstract:
  An 8 m successor to the Hubble Space Telescope (HST) would make incredible
gains in the study of stellar populations, especially in the Local Group. If
diffraction-limited at 0.5 microns, the "Next HST" could produce
high-resolution imaging of faint sources over a wide field in 1 percent of the
time needed with the HST. With these capabilities, photometry of the ancient
main sequence could be obtained for many sight-lines through Local Group
galaxies, thus determining directly the ages of their structures and providing
a formation history for the Local Group populations.


title: Microwave background constraints on inflationary parameters

abstract:
  We use a compilation of cosmic microwave anisotropy data (including the
recent VSA, CBI and Archeops results), supplemented with an additional
constraint on the expansion rate, to directly constrain the parameters of
slow-roll inflation models. We find good agreement with other papers concerning
the cosmological parameters, and display constraints on the power spectrum
amplitude from inflation and the first two slow-roll parameters, finding in
particular that $\epsilon_1 < 0.057$. The technique we use for parametrizing
inflationary spectra may become essential once the data quality improves
significantly.


title: On the Outbursts of Soft X-ray Transients

abstract:
  We suggest a new scenario to explain the outburst light curves of black hole
soft X-ray transients together with the secondary maximum and the bump seen on
their decay phases. Our explanations are based on the disk instability models
considering the effect of X-ray irradiation. The scenario is consistent with
the observed X-ray delays by a few days with respect to the optical rise for
both the main outburst and the later maxima. We test our scenario by
numerically solving the disk diffusion equation. The obtained model curve fits
well to the observed X-ray outburst photon flux curve of the black hole soft
X-ray transient GS/GRS 1124-68, a typical representative of the four BH SXTs
with very similar light curves.


title: Structure Shocks as a Source of Cosmic Rays in Clusters

abstract:
  Shocks are a ubiquitous consequence of cosmic structure formation, and they
play an essential role in heating galaxy cluster media. Virtually all of the
gas in clusters has been processed by one or more shocks of at least moderate
strength. These are collisionless shocks, so likely sites for diffusive shock
acceleration of high energy particles. We have carried out numerical
simulations of cosmic structure formation that directly include acceleration
and transport of nonthermal protons, as well as primary and secondary
electrons. Nonthermal emissions have also been computed from the resulting
particle spatial and energy distributions. Here we outline some of our current
findings, showing that nonthermal protons may contribute a significant pressure
in cluster media, and that expected radio, X-ray and $\gamma$-ray emissions
from these populations should be important cluster diagnostics.


title: Flows, Fragmentation, and Star Formation. I. Low-mass Stars in Taurus

abstract:
  The remarkably filamentary spatial distribution of young stars in the Taurus
molecular cloud has significant implications for understanding low-mass star
formation in relatively quiescent conditions. The large scale and regular
spacing of the filaments suggests that small-scale turbulence is of limited
importance, which could be consistent with driving on large scales by flows
which produced the cloud. The small spatial dispersion of stars from gaseous
filaments indicates that the low-mass stars are generally born with small
velocity dispersions relative to their natal gas, of order the sound speed or
less. The spatial distribution of the stars exhibits a mean separation of about
0.25 pc, comparable to the estimated Jeans length in the densest gaseous
filaments, and is consistent with roughly uniform density along the filaments.
The efficiency of star formation in filaments is much higher than elsewhere,
with an associated higher frequency of protostars and accreting T Tauri stars.
The protostellar cores generally are aligned with the filaments, suggesting
that they are produced by gravitational fragmentation, resulting in initially
quasi-prolate cores. Given the absence of massive stars which could strongly
dominate cloud dynamics, Taurus provides important tests of theories of
dispersed low-mass star formation and numerical simulations of molecular cloud
structure and evolution.


title:
Investigation of the Neupert effect in solar flares. I. Statistical
  properties and the evaporation model

abstract:
  Based on a sample of 1114 flares observed simultaneously in hard X-rays (HXR)
by the BATSE instrument and in soft X-rays (SXR) by GOES, we studied several
aspects of the Neupert effect and its interpretation in the frame of the
electron-beam-driven evaporation model. In particular, we investigated the time
differences ($\Delta t$) between the maximum of the SXR emission and the end of
the HXR emission, which are expected to occur at almost the same time.
Furthermore, we performed a detailed analysis of the SXR peak flux -- HXR
fluence relationship for the complete set of events, as well as separately for
subsets of events which are likely compatible/incompatibe with the timing
expectations of the Neupert effect. The distribution of the time differences
reveals a pronounced peak at $\Delta t = 0$. About half of the events show a
timing behavior which can be considered to be consistent with the expectations
from the Neupert effect. For these events, a high correlation between the SXR
peak flux and the HXR fluence is obtained, indicative of electron-beam-driven
evaporation. However, there is also a significant fraction of flares (about one
fourth), which show strong deviations from $\Delta t = 0$, with a prolonged
increase of the SXR emission distinctly beyond the end of the HXR emission.
These results suggest that electron-beam-driven evaporation plays an important
role in solar flares. Yet, in a significant fraction of events, there is also
clear evidence for the presence of an additional energy transport mechanism
other than the nonthermal electron beams, where the relative contribution is
found to vary with the flare importance.


title: The Sunyaev-Zel'dovich effect revisited

abstract:
  The well known Sunyaev-Zel'dovich (SZ) effect is reexamined using a Doppler
shift type mechanism arising from the scattering of photons by electrons in an
optically thin gas. The results are in excellent agreement with the
observational data as well as with the results obtained using the diffusive
pictures. A comparison of the results here obtained with other approaches is
thoroughly discussed, as well as some important extensions of this method to
other aspects of the SZ effect


title: High Energy Radiation from Neutron Star Binaries

abstract:
  This paper surveys our current knowledge of the hard X-ray emission
properties of old accreting neutron stars in low mass X-ray binaries. Hard
X-ray components extending up to energies of a few hundred keV have been
clearly detected in sources of both the Atoll and Z classes. The presence and
characteristics of these hard components are discussed in relation to source
properties and state. An overall anticorrelation between the fraction
luminosity in hard X-rays and mass accretion rate is apparent over different
sources spanning a large range of luminosities as well as individual source
undergoing state changes. Evidence for a second, yet unknown, parameter
controlling the hard X-ray emission is emerging. We draw a parallel with the
spectral properties of X-ray binaries hosting a stellar mass accreting black
hole, and conclude that, at a merely phenomenological level, there appears to
be a close analogy between the spectral properties of black hole candidates in
their high and intermediate states and Z-sources. We briefly mention models
that have been proposed for the hard X-ray emission of neutron star low mass
X-ray binaries and comment on perspectives in the INTEGRAL era.


title: Neutrino Masses in Astroparticle Physics

abstract:
  The case for small neutrino mass differences from atmospheric and solar
neutrino oscillation experiments has become compelling, but leaves the overall
neutrino mass scale m_nu undetermined. The most restrictive limit of m_nu < 0.8
eV arises from the 2dF galaxy redshift survey in conjunction with the standard
theory of cosmological structure formation. A relation between the hot dark
matter fraction and m_nu depends on the cosmic number density n_nu of
neutrinos. If solar neutrino oscillations indeed correspond to the favored
large mixing angle MSW solution, then big-bang nucleosynthesis gives us a
restrictive limit on all neutrino chemical potentials, removing the previous
uncertainty of n_nu. Therefore, a possible future measurement of m_nu will
directly establish the cosmic neutrino mass fraction Omega_nu. Cosmological
neutrinos with sub-eV masses can play an interesting role for producing the
highest-energy cosmic rays (Z-burst scenario). Sub-eV masses also relate
naturally to leptogenesis scenarios of the cosmic baryon asymmetry.
Unfortunately, the time-of-flight dispersion of a galactic or local-group
supernova neutrino burst is not sensitive in the sub-eV range.


title:
A Structural and Dynamical Study of Late-Type, Edge-On Galaxies: II.
  Vertical Color Gradients and the Detection of Ubiquitous Thick Disks

abstract:
  (abridged) We present an analysis of B-R and R-K_s color maps for 47
late-type, edge-on, unwarped, bulgeless disk galaxies spanning a wide range of
mass. The color maps show that the thin disks of these galaxies are embedded
within a low surface brightness red envelope that is substantially thicker than
the thin disk (a/b~4:1 vs a/b>8:1), extends to at least 5 vertical disk scale
heights above the galaxy midplane, and has a radial scale length that appears
to be uncorrelated with that of the embedded thin disk. The color of the red
envelope is similar from galaxy to galaxy and is consistent with a relatively
old (>6Gyr) stellar population that is not particularly metal-poor. The color
difference between the thin disk and the envelope varies systematically with
rotation speed, indicating a younger thin disk relative to the red envelope in
lower mass galaxies. The red stellar envelopes are similar to the MW thick
disk, having common surface brightnesses, spatial distributions, mean ages, and
metallicities. The ubiquity of the red stellar envelopes implies that the
formation of the thick disk is a nearly universal feature of disk formation and
need not be associated with bulge formation. Furthermore, our data suggest that
the thick disk forms early, even in cases where the majority of star formation
was recent. Finally, we find that our data and the observed properties of the
MW thick disk argue in favor of a merger origin for the thick disk population.
If so, then the age of the thick disk marks the end of the epoch of major
merging, and the age difference between the thin and thick disks can become a
strong constraint on cosmological constants and models of galaxy and/or
structure formation.


title:
Narrow-Angle Astrometry with the Space Interferometry Mission: The
  Search for Extra-solar Planets. I. Detection and Characterization of Single
  Planets

abstract:
  (abridged) We present results from a detailed set of end-to-end numerical
simulations of SIM narrow-angle astrometric measurements and data analysis to
illustrate the enormous potential that SIM has for the discovery and
characterization of planets outside the Solar System. Utilizing a template
observing scenario, we quantify SIM sensitivity to single planets orbiting
single normal nearby stars as function of measurement errors and properties of
the planet: SIM will detect over 95% of the planets with periods between a few
days and the 5-year nominal mission lifetime that produce astrometric
signatures $\sim 2.2$ times larger than the single-measurement accuracy. We
provide accuracy estimates of full-orbit reconstruction and planet mass
determination: at twice the discovery limit, orbital elements will be
determined with a typical accuracy of 20-30%; the astrometric signature must be
$\sim 10$ and $\sim 15$ times the minimum signal required for detection to
derive mass and inclination angle estimates accurate to 10%. We quantify the
impact of different observing strategies on the boundaries for secure detection
and accurate orbit estimation: the results scale with the square root of both
the number of observations and the number of reference stars. We investigate
SIM discovery space, to gauge the instrument ability in detecting very low-mass
planets: around the nearest stars, SIM will find planets as small as Earth, if
they are present. Some of these might be orbiting inside the parent star's
Habitable Zone. (abridged)


title: The Iron Project and Non-LTE stellar modeling

abstract:
  Latest developments in theoretical computations since the international
Opacity Project (OP), under the new the Iron Project (IP) and extensions, are
described for applications to a variety of objects such as stellar atmospheres,
nebulae, and active galactic nuclei. The primary atomic processes are: electron
impact excitation (EIE), photoionization, electron-ion recombination, and
bound-bound transitions, all considered using the accurate and powerful
R-matrix method including relativistic effects. As an extension of the OP and
the IP, a self-consistent and unified theoretical treatment of photoionization
and recombination has been developed. Both the radiative and the dielectronic
recombination (RR and DR) processes are considered in a unified manner.
Photoionization and recombination cross sections are computed with identical
wavefunction expansions, thus ensuring self-consistency in an ab initio manner.
The new unified results differ from the sum of previous results for RR and DR
by up to a factor of 4 for the important but complex atomic systems such as Fe
I - V. The fundamental differences are due to quantum mechanical intereference
and coupling effects neglected in simpler approximations that unphysically
treat RR and DR separately, which can not be independently measured or
observed. I will also describe the electronic, web-interactive, database,
TIPTOPBASE, to archive the OP/IP data in a readily accessible manner.
TIPTOPBASE would also include electron-ion recombination data and new fine
structure transition probabilities. Efficient codes developed by M.J. Seaton to
calculate `customized' mixture opacities and radiative accelerations
('levitation') in stars will also be available.


title:
Self-consistent ab initio calculations for photoionization and
  electron-ion recombination using the R-matrix method

abstract:
  Most astrophysical plasmas entail a balance between ionization and
recombination. We present new results from the powerful R-matrix method which
yields in an ab initio manner: (I) self-consistent photoionization and
recombination cross sections using identical wavefunction expansions, (II)
unified e-ion recombination rates at all temperatures of interest,
incorporating non-resonant and resonant processes, radiative and dielectronic
recombination (RR and DR), and (III) level-specific recombination rates for
many excited atomic levels. RR and DR processes can not be measured or observed
independently. In contrast to the shortcomings of simple (but computationally
easy) approximations that unphysically treat RR and DR separately with
different methods, emphasizing marginal effects for selected ions over small
energy ranges, the R-matrix method naturally and compeletely accounts for e-ion
recombination for all atomic systems.
  Photoionization and recombination cross sections are compared with
state-of-the-art experiments on synchrotron radiation sources and ion storage
rings. Overall agreement between theory and experiments is within 10-20 %. For
photoionization the comparison includes not only the ground state but also the
metastable states, with highly resolved resonance structures. The recent
experiments therefore support the estimated accuracy of the vast amount of
photoionization data computed under the Opacity Project (OP), the Iron Project
(IP), and related works using the R-matrix method.


title:
Relativistic fine structure oscillator strengths for Li-like ions: C IV
  - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

abstract:
  Ab initio calculations including relativistic effects employing the
Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy
levels and oscillator strengths upto n = 10 and 0.leq. l .leq.9 for 15 Li-like
ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar
XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine
structure energy levels of total angular momenta, 1/2 .leq. J .leq. 17/2 of
even and odd parities, total orbital angular momentum, 0 .leq L .leq. 9 and
spin multiplicity (2S+1) = 2, 4 are considered for each ion. The levels provide
almost 900 dipole allowed and intercombination bound-bound transitions. The
BPRM method enables consideration of large set of transitions with uniform
accuracy compared to the best available theoretical methods. The CC
eigenfunction expansion for each ion includes the lowest 17 fine structure
energy levels of the core configurations 1s^2, 1s2s, 1s2p, 1s3s, 1s3p, and
1s3d. The calculated energies of the ions agree with the measured values to
within 1% for most levels. The transition probabilities show good agreement
with the best available calculated values. The results provide the largest sets
of energy levels and transition rates for the ions and are expected to be
useful in the analysis of X-ray and EUV spectra from astrophysical sources.


title:
Detecting Radio Emission from Cosmic Ray Air Showers and Neutrinos with
  a Digital Radio Telescope

abstract:
  We discuss the possibilities of measuring ultra-high energy cosmic rays and
neutrinos with radio techniques. We review a few of the properties of radio
emission from cosmic ray air showers and show how these properties can be
explained by coherent ``geosynchrotron'' emission from electron-positron pairs
in the shower as they move through the geomagnetic field. This should allow one
to use the radio emission as a useful diagnostic tool for cosmic ray research.
A new generation of digital telescopes will make it possible to study this
radio emission in greater detail. For example, the planned Low-Frequency Array
(LOFAR), operating at 10-200 MHz, will be an instrument uniquely suited to
study extensive air showers and even detect neutrino-induced showers on the
moon. We discuss sensitivities, count rates and possible detection algorithms
for LOFAR and a currently funded prototype station LOPES. This should also be
applicable to other future digital radio telescopes such as the
Square-Kilometer-Array (SKA). LOFAR will be capable of detecting air-shower
radio emission from >2*10^14 eV to ~10^20 eV. The technique could be easily
extended to include air shower arrays consisting of particle detectors
(KASCADE, Auger), thus providing crucial additional information for obtaining
energy and chemical composition of cosmic rays. It also has the potential to
extend the cosmic ray search well beyond an energy of 10^21 eV if isotropic
radio signatures can be found. Other issues that LOFAR can address are to
determine the neutral component of the cosmic ray spectrum, possibly look for
neutron bursts, and do actual cosmic ray astronomy.


title: The r-Process without Excess Neutrons

abstract:
  The r-process of nucleosynthesis requires a large neutron-to-seed nucleus
ratio. This does not, however, that there be an excess of neutrons over
protons. If the expansion of the material is sufficiently rapid and the entropy
per nucleon is sufficiently high, the nucleosynthesis enters a heavy-element
synthesis regime heretofore unexplored. In this extreme regime, characterized
by a persistent disequilibrium between free nucleons and the abundant alpha
particles, heavy r-process nuclei can form even in matter with more protons
than neutrons. This observation bears on the issue of the site of the
r-process, on the variability of abundance yields from r-process events, and on
cnstraints on neutrino physics derived from nucleosynthesis. It also clarifies
the difference between nucleosynthesis in the early universe and that in less
extreme stellar explosive environments.


title: Occultation and Microlensing

abstract:
  Occultation and microlensing are different limits of the same phenomena of
one body passing in front of another body. We derive a general exact analytic
expression which describes both microlensing and occultation in the case of
spherical bodies with a source of uniform brightness and a non-relativistic
foreground body. We also compute numerically the case of a source with
quadratic limb-darkening. In the limit that the gravitational deflection angle
is comparable to the angular size of the foreground body, both microlensing and
occultation occur as the objects align. Such events may be used to constrain
the size ratio of the lens and source stars, the limb-darkening coefficients of
the source star, and the surface gravity of the lens star (if the lens and
source distances are known). Application of these results to microlensing
during transits in binaries and giant-star microlensing are discussed. These
results unify the microlensing and occultation limits and should be useful for
rapid model fitting of microlensing, eclipse, and "microccultation" events.


title:
Comment on "Does the rapid appearence of life on Earth suggest that life
  is common in the Universe"

abstract:
  In a recent paper [1] Lineweaver and Davis performed a statistical analysis
to claim that the rapidity of biogenesis on Earth indicates high probability of
biogenesis on terrestrial- type planets. We argue that the rapid appearance of
life on Earth hardly tells us anything about the probability of life to appear
on other planet. The conclusion should be different. The rapid initial
biogenesis is consistent with a large number ($N \sim 10$) of crucial steps in
evolution from simplest life forms to humans.


title:
Reliability of merger tree realizations of dark halos in the Monte-Carlo
  modeling of galaxy formation

abstract:
  We examine the reliability of the merger trees generated for the Monte-Carlo
modeling of galaxy formation. In particular we focus on the cold gas fraction
predicted from the merger trees with different assumptions on the progenitor
distribution function, the timestep, and the mass resolution. We show that the
cold gas fraction is sensitive to the accuracy of the merger trees at
small-mass scales of progenitors at high redshifts. One can reproduce the
Press-Schechter prediction to a reasonable degree by adopting a fairly large
number of redshift bins, N_{step} ~ 1000 in generating merger trees, which is a
factor of ten larger than the canonical value used in previous literature.


title: MOND--theoretical aspects

abstract:
  I discuss open theoretical questions pertaining to the modified dynamics
(MOND)--a proposed alternative to dark matter, which posits a breakdown of
Newtonian dynamics in the limit of small accelerations. In particular, I point
the reasons for thinking that MOND is an effective theory--perhaps, despite
appearance, not even in conflict with GR. I then contrast the two
interpretations of MOND as modified gravity and as modified inertia. I describe
two mechanical models that are described by potential theories similar to
(non-relativistic) MOND: a potential-flow model, and a membrane model. These
might shed some light on a possible origin of MOND. The possible involvement of
vacuum effects is also speculated on.


title: XMM-Newton AO-1 observations three SHARC galaxy clusters

abstract:
  We present the follow-up of three medium redshift galaxy clusters from the
SHARC survey observed with XMM-Newton. We studied RX J0256.5+0006 which shows
two components which are very likely in interaction. The smallest component
exhibits a comet-like structure indicating ram pressure stripping as it falls
onto the main cluster. The second cluster, RX J2237.0-1516 is an elliptical
cluster with a gas temperature of 3.0$\pm$0.5 keV. The third cluster, RX
J1200.8-0328 seems to be in a relaxed state because its shape is regular and we
do not see obvious temperature gradient. Its mean temperature is
5.1$^{+0.7}_{-0.5}$ keV.


title:
The Hernquist model revisited: completely analytical anisotropic
  dynamical models

abstract:
  Simple analytical models, such as the Hernquist model, are very useful tools
to investigate the dynamical structure of galaxies. Unfortunately, most of the
analytical distribution functions are either isotropic or of the
Osipkov-Merritt type, and hence basically one-dimensional. We present three
different families of anisotropic distribution functions that self-consistently
generate the Hernquist potential-density pair. These families have constant,
increasing and decreasing anisotropy profiles respectively, and can hence
represent a wide variety of orbital structures. For all of the models
presented, the distribution function and the velocity dispersions can be
written in terms of elementary functions. These models are ideal tools for a
wide range of applications, in particular to generate the initial conditions
for N-body or Monte Carlo simulations.


title: Temporal aspects and frequency distributions of solar soft X-ray flares

abstract:
  A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by
GOES during the period 1976-2000 is presented. On the basis of this extensive
data set, statistics on temporal properties of soft X-ray flares, such as
duration, rise and decay times with regard to the SXR flare classes is
presented. Correlations among distinct flare parameters, i.e. SXR peak flux,
fluence and characteristic times, and frequency distributions of flare
occurrence as function of the peak flux, the fluence and the duration are
derived. We discuss the results of the analysis with respect to statistical
flare models, the idea of coronal heating by nanoflares, and elaborate on
implications of the obtained results on the Neupert effect in solar flares.


title: High Resolution Mid-infrared Imaging of W3(OH)

abstract:
  We present results of our diffraction-limited mid-infrared imaging of the
massive star-forming region W3(OH) with SpectroCam-10 on the 5-m Hale telescope
at wavelengths of 8.8, 11.7, and 17.9 micron. The thermal emission from heated
dust grains associated with the ultracompact HII region W3(OH) is resolved and
has a spatial extent of ~2 arcsec in the N band. We did not detect the hot core
source W3(H_2O) which implies the presence of at least 12 mag of extinction at
11.7 micron towards this source. These results together with other data were
used to constrain the properties of W3(OH) and W3(H_2O) and their envelopes by
modelling the thermal dust emission.


title: The nature and size of the optical continuum source in QSO 2237+0305

abstract:
  From the peak of a gravitational microlensing high-magnification event in the
A component of QSO 2237+0305, which was accurately monitored by the GLITP
collaboration, we derived new information on the nature and size of the optical
V-band and R-band sources in the far quasar. If the microlensing peak is caused
by a microcaustic crossing, we firstly obtained that the standard accretion
disk is a scenario more reliable/feasible than other usual axially symmetric
models. Moreover, the standard scenario fits both the V-band and R-band
observations with reduced chi-square values very close to one. Taking into
account all these results, a standard accretion disk around a supermassive
black hole is a good candidate to be the optical continuum main source in QSO
2237+0305. Secondly, using the standard source model and a robust upper limit
on the transverse galactic velocity, we inferred that 90 per cent of the V-band
and R-band luminosities are emitted from a region with radial size less than
1.2 10^{-2} pc (= 3.7 10^{16} cm, at 2*sigma confidence level).


title:
Polarization angular spectra of Galactic synchrotron emission on
  arcminute scales

abstract:
  We study the angular power spectra of the polarized component of the Galactic
synchrotron emission in the 28-deg^2 Test Region of the Southern Galactic Plane
Survey at 1.4 GHz. These data were obtained by the Australia Telescope Compact
Array and allow us to investigate angular power spectra down to arcminute
scales. We find that, at this frequency, the polarization spectra for E- and
B-modes seem to be affected by Faraday rotation produced in compact foreground
screens. A different behavior is shown by the angular spectrum of the polarized
intensity PI=\sqrt{Q^2+U^2}. This is well fitted by a power law with slope
\~1.7, which agrees with higher frequency results and can probably be more
confidently extrapolated to the cosmological window.


title:
Modelling SCUBA sources in a Lambda-CDM cosmology: hot starbursts or
  cold extended galactic dust?

abstract:
  Previous modelling has demonstrated that it is difficult to reproduce the
SCUBA source counts within the framework of standard hierarchical structure
formation models if the sources are assumed to be the high-redshift
counterparts of local ultra-luminous infrared galaxies with dust temperatures
in the range 40-60 K. Here, we show that the counts are more easily reproduced
in a model in which the bulk of the sub-millimetre emission comes from
extended, cool (20-25 K) dust in objects with star formation rates of 50-100
solar masses per year. The low temperatures imply typical sizes of about 1
(S_{850}/1mJy})^{1/2} arcsec, a factor two to three larger than those predicted
using starburst-like spectral energy distributions. Low dust temperatures also
imply a ratio of optical/UV to 850-micron flux which is 30-100 times smaller,
for the same optical depth, than expected for objects with a hot,
starburst-like SED. This may help explain the small overlap between SCUBA
sources and Lyman-break galaxies.


title: Statistical analysis of solar H-alpha flares

abstract:
  A statistical analysis of a large data set of H-alpha flares comprising
almost 100000 single events that occurred during the period January 1975 to
December 1999 is presented. We analyzed the flares evolution steps, i.e.
duration, rise times, decay times and event asymmetries. Moreover, these
parameters characterizing the temporal behavior of flares, as well as the
spatial distribution on the solar disk, i.e. N-S and E-W asymmetries, are
analyzed in terms of their dependency on the solar cycle. The main results are:
1) The duration, rise and decay times increase with increasing importance
class. The increase is more pronounced for the decay times than for the rise
times. The same relation is valid with regard to the brightness classes but in
a weaker manner. 2) The event asymmetry indices, which characterize the
proportion of the decay to the rise time of an event, are predominantly
positive (90%). For about 50% of the events the decay time is even more than 4
times as long as the rise time. 3) The event asymmetries increase with the
importance class. 4) The flare duration and decay times vary in phase with the
solar cycle; the rise times do not. 5) The event asymmetries do not reveal a
distinct correlation with the solar cycle. However, they drop during times of
solar minima, which can be explained by the shorter decay times found during
minimum activity. 6) There exists a significant N-S asymmetry over longer
periods, and the dominance of one hemisphere over the other can persist for
more than one cycle. 7) For certain cycles there may be evidence that the N-S
asymmetry evolves with the solar cycle, but in general this is not the case. 8)
There exists a slight but significant E-W asymmetry with a prolonged eastern
excess.


title: Origin of Galactic and Extragalactic Magnetic Fields

abstract:
  A variety of observations suggest that magnetic fields are present in all
galaxies and galaxy clusters. These fields are characterized by a modest
strength (10^{-7}-10^{-5} G) and huge spatial scale (~Mpc). It is generally
assumed that magnetic fields in spiral galaxies arise from the combined action
of differential rotation and helical turbulence, a process known as the
alpha-omega dynamo. However fundamental questions concerning the nature of the
dynamo as well as the origin of the seed fields necessary to prime it remain
unclear. Moreover, the standard alpha-omega dynamo does not explain the
existence of magnetic fields in elliptical galaxies and clusters. The author
summarizes what is known observationally about magnetic fields in galaxies,
clusters, superclusters, and beyond. He then reviews the standard dynamo
paradigm, the challenges that have been leveled against it, and several
alternative scenarios. He concludes with a discussion of astrophysical and
early Universe candidates for seed fields.


title: High Energy Results from BeppoSAX

abstract:
  We review all the BeppoSAX results relative to the search for additional
nonthermal components in the spectra of clusters of galaxies. In particular,
our MECS data analysis of A2199 does not confirm the presence of the nonthermal
excess reported by Kaastra et al. (1999). A new observation of A2256 seems to
indicate quite definitely that the nonthermal fluxes detected in Coma and A2256
are due to a diffuse nonthermal mechanism involving the intracluster medium. We
report marginal evidence (~3\sigma) for a nonthermal excess in A754 and A119,
but the presence of point sources in the field of view of the PDS makes
unlikely a diffuse interpretation.


title: LIGO/VIRGO searches for gravitational radiation in hypernovae

abstract:
  A torus around a stellar mass Kerr black hole can emit about 10% of the
spin-energy of the black hole in gravitational radiation, potentially
associated with a gamma-ray burst. Wide tori may develop buckling modes by the
Papaloizou-Pringle instability and gravitational radiation-reaction forces in
the Burke-Thorne approximation. Gravitational wave experiments may discover
these emissions in a fraction of nearby supernovae. This provides a test for
Kerr black holes, and for GRB inner engines by comparison with the
de-redshifted durations of long GRBs.


title:
Tests of the Las Campanas Distant Cluster Survey from Confirmation
  Observations for the ESO Distant Cluster Survey

abstract:
  The ESO Distant Cluster Survey (EDisCS) is a photometric and spectroscopic
study of the galaxy cluster population at two epochs, z~0.5 and z~0.8, drawn
from the Las Campanas Distant Cluster Survey (LCDCS). We report results from
the initial candidate confirmation stage of the program and use these results
to probe the properties of the LCDCS. Of the 30 candidates targeted, we find
statistically significant overdensities of red galaxies near 28. Of the ten
additional candidates serendipitously observed within the fields of the
targeted 30, we detect red galaxy overdensities near six. We test the
robustness of the published LCDCS estimated redshifts to misidentification of
the brighest cluster galaxy (BCG) in the survey data, and measure the spatial
alignment of the published cluster coordinates, the peak red galaxy
overdensity, and the brightest cluster galaxy. We conclude that for LCDCS
clusters out to z~0.8, 1) the LCDCS coordinates agree with the centroid of the
red galaxy overdensity to within 25'' (~150 h^{-1} kpc) for 34 out of 37
candidates with 3\sigma galaxy overdensities, 2) BCGs are typically coincident
with the centroid of the red galaxy population to within a projected separation
of 200 h^{-1} kpc (32 out of 34 confirmed candidates), 3) the red galaxy
population is strongly concentrated, and 4) the misidentification of the BCG in
the LCDCS causes a redshift error >0.1 in 15-20% of the LCDCS candidates. These
findings together help explain the success of the surface brightness
fluctuations detection method.


title:
Topological changes of the photospheric magnetic field inside active
  regions: a prelude to flares

abstract:
  The observations of magnetic field variations as a signature of flaring
activity is one of the main goal in solar physics. Some efforts in the past
give apparently no unambiguous observations of changes. We observed that the
scaling laws of the current helicity inside a given flaring active region
change clearly and abruptly in correspondence with the eruption of big flares
at the top of that active region. Comparison with numerical simulations of MHD
equations, indicates that the change of scaling behavior in the current
helicity, seems to be associated to a topological reorganization of the
footpoint of the magnetic field loop, namely to dissipation of small scales
structures in turbulence. It is evident that the possibility of forecasting in
real time high energy flares, even if partially, has a wide practical interest
to prevent the effects of big flares on Earth and its environment.


title: s-Process Nucleosynthesis in Carbon Stars

abstract:
  We present the first detailed and homogeneous analysis of the s-element
content in Galactic carbon stars of N-type. Abundances of Sr,Y, Zr (low-mass
s-elements, or ls) and of Ba, La, Nd, Sm and Ce (high-mass s-elements, hs) are
derived using the spectral synthesis technique from high-resolution spectra.
The N-stars analyzed are of nearly solar metallicity and show moderate
s-element enhancements, similar to those found in S stars, but smaller than
those found in the only previous similar study (Utsumi 1985), and also smaller
than those found in supergiant post-AGB stars. This is in agreement with the
present understanding of the envelope s-element enrichment in giant stars,
which is increasing along the spectral sequence M-->MS-->S-->SC-->C during the
AGB phase. We compare the observational data with recent $s$-process
nucleosynthesis models for different metallicities and stellar masses. Good
agreement is obtained between low mass AGB star models (M < 3 M_o) and
s-elements observations. In low mass AGB stars, the 13C(alpha, n)16O reaction
is the main source of neutrons for the s-process; a moderate spread, however,
must exist in the abundance of 13C that is burnt in different stars. By
combining information deriving from the detection of Tc, the infrared colours
and the theoretical relations between stellar mass, metallicity and the final
C/O ratio, we conclude that most (or maybe all) of the N-stars studied in this
work are intrinsic, thermally-pulsing AGB stars; their abundances are the
consequence of the operation of third dredge-up and are not to be ascribed to
mass transfer in binary systems.


title:
The Virtual Observatory as a Tool to Study Star Cluster Populations in
  Starburst Galaxies

abstract:
  The cluster luminosity function (CLF) is one of the most important
diagnostics in the study of old globular and young compact star cluster
populations. We are currently using ASTROVIRTEL to obtain CLFs in several
optical and/or near-infrared passbands, and colour distributions. This will
provide us with a powerful analytical tool for the determination of the violent
star and cluster formation history of galaxies: we will address questions
related to the universality of the globular CLF, the time-scale of low-mass,
low-luminosity star cluster depletion and its observability, and environmental
effects affecting the shape of the CLFs and the efficiency of the depletion
process. This has required the development of complex data mining tools, which
are currently being incorporated in ASTROVIRTEL's "querator".


title: Primordial or Dynamical Mass Segregation in Young LMC Clusters?

abstract:
  We present the detailed analysis of Hubble Space Telescope observations of
the spatial distributions of different stellar species in two young compact
star clusters in the Large Magellanic Cloud, NGC 1805 and NGC 1818. Based on a
comparison of the characteristic relaxation times in their cores and at their
half-mass radii with the observed degree of mass segregation, it is most likely
that significant primordial mass segregation was present in both clusters,
particularly in NGC 1805. Both clusters were likely formed with very similar
initial mass functions.


title: Mixing by Non-linear Gravity Wave Breaking on a White Dwarf Surface

abstract:
  We present the results of a simulation of a wind-driven non-linear gravity
wave breaking on the surface of a white dwarf. The ``wind'' consists of H/He
from an accreted envelope, and the simulation demonstrates that this breaking
wave mechanism can produce a well-mixed layer of H/He with C/O from the white
dwarf above the surface. Material from this mixed layer may then be transported
throughout the accreted envelope by convection, which would enrich the C/O
abundance of the envelope as is expected from observations of novae.


title: AGN Black Hole Masses and Bolometric Luminosities

abstract:
  Black hole mass, along with mass accretion rate, is a fundamental property of
active galactic nuclei. Black hole mass sets an approximate upper limit to AGN
energetics via the Eddington limit. We collect and compare all AGN black hole
mass estimates from the literature; these 177 masses are mostly based on the
virial assumption for the broad emission lines, with the broad-line region size
determined from either reverberation mapping or optical luminosity. We
introduce 200 additional black hole mass estimates based on properties of the
host galaxy bulges, using either the observed stellar velocity dispersion or
using the fundamental plane relation to infer $\sigma$; these methods assume
that AGN hosts are normal galaxies. We compare 36 cases for which black hole
mass has been generated by different methods and find, for individual objects,
a scatter as high as a couple of orders of magnitude. The less direct the
method, the larger the discrepancy with other estimates, probably due to the
large scatter in the underlying correlations assumed. Using published fluxes,
we calculate bolometric luminosities for 234 AGNs and investigate the relation
between black hole mass and luminosity. In contrast to other studies, we find
no significant correlation of black hole mass with luminosity, other than those
induced by circular reasoning in the estimation of black hole mass. The
Eddington limit defines an approximate upper envelope to the distribution of
luminosities, but the lower envelope depends entirely on the sample of AGN
included. For any given black hole mass, there is a range in Eddington ratio of
up to three orders of magnitude.


title: Active Optics on the Baade 6.5-m (Magellan I) Telescope

abstract:
  The Magellan active optics system has been operating continuously on the
Baade 6.5-m since the start of science operations in February 2001. The active
optical elements include the primary mirror, with 104 actuators, and the
secondary mirror, with 5 positional degrees of freedom. Shack-Hartmann (SH)
wavefront sensors are an integral part of the dual probe guiders. The probes
function interchangeably, with either probe capable of guiding or wavefront
sensing. In the course of most routine observing stars brighter than 17th
magnitude are used to apply corrections once or twice per minute. The rms
radius determined from roughly 250 SH spots typically ranges between 0.05" and
0.10". The spot pattern is analyzed in terms of a mixture of 3 Zernike
polynomials (used to correct the secondary focus and decollimation) and 12
bending modes of the primary mirror (used to compensate for residual thermal
and gravitational distortions). Zernike focus and the lowest order circularly
symmetric bending mode, known affectionately as the "conemode," are
sufficiently non-degenerate that they can be solved for and corrected
separately.


title: Chandra Observations of Abell 85: Merger of the South Subcluster

abstract:
  We present an analysis of a highly asymmetric cluster merger from a Chandra
observation of Abell 85. The merger shows significant disruption of the less
massive subcluster from ram pressure effects. Nevertheless, a cold core,
coincident with the cD galaxy, is observed to persist in the subcluster. We
derive dynamical information from the motion of the cold core through the main
cluster's ICM. Multiple derivations of the velocity of the core suggest a Mach
number of M ~ 1.4 or v ~ 2150 km/s, though with substantial uncertainty. We
construct a consistent kinematic model for the merger based on this dynamical
analysis. As has been found for other such "cold fronts," conduction appears to
be suppressed across the front. Thermal conduction may be suppressed by a
magnetic field with a significant component perpendicular to the subcluster's
direction of motion. The effect of the merger interaction in creating and
shaping the observed radio sources is also discussed. It appears most likely
that the radio source is due to distorted and detached lobes from the
subcluster cD galaxy, rather than being a radio halo.


title: Microlensing towards the Large Magellanic Cloud

abstract:
  The nature and the location of the lenses discovered in the microlensing
surveys done so far towards the LMC remain unclear. Motivated by these
questions we compute the optical depth and particularly the number of expected
events for self-lensing for both the MACHO and EROS2 observations. We calculate
these quantities also for other possible lens populations such as thin and
thick disk and galactic spheroid. Moreover, we estimate for each of these
components the corresponding average event duration and mean mass using the
mass moment method. By comparing the theoretical quantities with the values of
the observed events it is possible to put some constraints on the location and
the nature of the MACHOs. Clearly, given the large uncertainties and the few
events at disposal it is not possible to draw sharp conclusions, nevertheless
we find that certainly at least 3-4 MACHO events are due to lenses in LMC,
which are most probably low mass stars, but that hardly all events can be due
to self-lensing. This conclusions is even stronger when considering the EROS2
events, due to their spatial distribution. The most plausible solution is that
the events observed so far are due to lenses belonging to different intervening
populations: low mass stars in the LMC, in the thick disk, in the spheroid and
possibly some true MACHOs in the halo.


title: The Guaranteed Gamma-Ray Background

abstract:
  The diffuse extragalactic gamma-ray background (EGRB) above 100 MeV encodes
unique information about high-energy processes in the universe. Numerous
sources for the EGRB have been proposed, but the two systems which are certain
to make some contribution are active galaxies (blazars) as well as normal
galaxies. In this paper, we evaluate the contribution to the background from
both sources. The active galaxy contribution arises from unresolved blazars. We
compute this contribution using the Stecker-Salamon model. For normal galaxies,
the emission is due to cosmic-ray interactions with diffuse gas. Our key
assumption here is that the cosmic-ray flux in a galaxy is proportional to the
supernova rate and thus the massive star formation rate, quantified
observationally by the cosmic star formation rate (CSFR). In addition, the
existence of stars today requires a considerably higher ISM mass in the past.
Using the CSFR to compute both these effects, we find that normal galaxies are
responsible for a significant portion (\sim 1/3) of the EGRB near 1 GeV, but
make a smaller contribution at other energies. Finally, we present a "minimal"
two-component model which includes contributions from both normal galaxies and
blazars. We show that the spectrum of the diffuse radiation is a key constraint
on this model: while neither the blazar spectra, nor the galactic spectra, are
separately optimal fits to the observed spectrum, the combined emission
provides an excellent fit. We close by noting key observational tests of this
two-component model, which can be probed by future gamma-ray observatories such
as GLAST.


title: The central region in SS433 supercritical disk and origin of flares

abstract:
  Mean orbital light curves of SS433 in different precessional phases are
analysed for active and passive states separately. In passive states the mean
brightness depends strongly on the disk orientation, the star is fainter by a
factor about 2.2 in the disk edge-on positions. In active states the brightness
does not depend significantly on the precessional phase. We suggest that in
active states hot gas cocoons surrounding the inner jets grow and can not be
shielded by the disk rim in the edge-on phases. Brightest optical flares are
clear separated in two groups in orbital phases, it is considered as indication
of orbital eccentricity. Bright flares prefer specific precession and nodding
phases, it favours the slaved disk model and the flares as disk perturbations
by a torque applied to outer parts of the accretion disk.


title: Hot Flashes On Miras?

abstract:
  Short time scale variations have been reported for a few Miras, including
sudden 0.2 magnitude or more brightening in the visual lasting from a few hours
to a few days. Are these flashes real? Are they hot? What are they? Almost all
the natural time scales for variation in the atmosphere and wind of a Mira
variable are months to years long. What could cause such short-term variations?
One intriguing possibility is that the variations are associated with the
interaction of a Jovian planet with the time-dependent outflow of a Mira wind.
Here we discuss observable features of such an interaction in terms of
order-of-magnitude estimates and phenomenology, and make one clear prediction
requiring observational followup. Future work needs to include both theoretical
calculations and the development of systematic methods for searching for such
events.


title: Models of Planets and Brown Dwarfs in Mira Winds

abstract:
  We present numerical hydrodynamical models of the effects of planets or brown
dwarfs orbiting within the extended atmosphere and wind formation zone of Mira
variables. We find time-dependent wake dynamics and episodic accretion
phenomena which may give rise to observable optical events and affect SiO maser
emission.


title:
The October 1985 Long Outburst of U Geminorum: Revealing the Viscous
  Time Scale in Long Orbital Period Dwarf Novae

abstract:
  We examine the AAVSO light curve of U Geminorum from 1908 to 2002, with
particular focus on the October 1985 outburst. This outburst was longer than
any other seen in U Gem by about a factor of 2, and appears to be unique among
all dwarf nova outbursts seen in systems with orbital periods longer than 3 hr
in that one can measure the decay time scale during the initial slow decay.
This rate is ~26+-6 d/mag. Using estimates of the rate of accretion during
outburst taken from Froning et al., one can show that ~1e24 g of gas was
accreted onto the white dwarf during the outburst. When coupled with the
viscous time inferred from the (short orbital period) SU UMa stars, the U Gem
viscous time scale lends support to the standard model in which the decays in
dwarf novae can either be viscous or thermal, with the ratio between them being
roughly h/r where h is the vertical pressure scale height in the disk.


title:
Circumnuclear regions in barred spiral galaxies II. Relations to host
  galaxies

abstract:
  We present optical broad- and narrow-band imaging of a sample of a dozen
barred galaxies. These images are analyzed in conjunction with our previously
published near-infrared imaging of their central regions and with literature
values for, e.g., bar strengths and the total star formation activity of the
galaxies. We present B, I and H alpha images, and radial profiles derived from
these, to infer geometric and dynamical parameters of the structural components
of the galaxies, such as bar lengths, bar ellipticities, and location of star
formation and dust. We find that the more centrally concentrated the H alpha
emission in a galaxy is, i.e., the higher the fraction of star formation
originating in the circumnuclear region, the higher the overall star formation
rate, as measured from far-infrared flux ratios. Stronger bars host smaller
nuclear rings, but the strength of the bar does not correlate with either the
intrinsic ellipticity of the ring or the offset between the position angles of
the bar and the ring. We interpret these results in comparison with modelling
of gas inflow in the circumnuclear region, and show that they were
theoretically expected. We confirm observationally, and for the first time, the
anti-correlation predicted from theory and modelling between the degree of
curvature of the bar dust lanes and the strength of the bar, where stronger
bars have straighter dust lanes.


title: On stationary oscillations of galaxies

abstract:
  This paper describes a general investigation of stationary oscillations of
galaxies. It begins with a linear analysis of modes of oscillation with
continuous spectra of real frequencies. Such modes are gravitational analogues
of the van Kampen modes of oscillation in plasmas. The characteristic value
problem governing modes of the van Kampen type in a galaxy is solved with the
aid of a modified version of the matrix method of Kalnajs in which the
perturbation of the distribution function is expressed in terms of generalized
functions. In general, there is no characteristic equation governing the
frequencies in the continuous spectrum. However, isolated frequencies in the
continuous spectrum do satisfy a characteristic equation which, for stellar
systems, is a counterpart of the dispersion relation proposed by Vlasov for
plasma oscillations. The linear analysis also provides a characteristic
equation for modes with a discrete spectrum of real and/or complex frequencies.
The second part of the paper describes a perturbation theory for a stationary
oscillation of a galaxy with a small but finite amplitude. Integrals of the
stellar motion are constructed with the aid of canonical perturbation theory
and used in conjunction with the theorem of Jeans in order to specify the
density of stars in the six-dimensional phase space. These oscillations are
slightly nonlinear counterparts of the modes of the van Kampen type, and they
are stellar-dynamical counterparts of the nonlinear plasma waves described by
Bernstein, Greene, and Kruskal. Fully nonlinear models of stationary
oscillations of galaxies can be constructed with the aid of Schwarzschild's
numerical method for the solution of the fundamental integral equation
describing the self-consistency of a stellar system.


title:
Beyond Flux-Limited Diffusion: Parallel Algorithms for Multidimensional
  Radiation Hydrodynamics

abstract:
  This paper presents a new code for performing multidimensional radiation
hydrodynamic (RHD) simulations on parallel computers involving anisotropic
radiation fields and nonequilibrium effects. The radiation evolution modules
described here encapsulate the physics provided by the serial algorithm of
Stone et. al (ApJSupp, vol 80, pp. 819-845), but add new functionality with
regard to physics and numerics. Physics enhancments include the addition of
time dependence to the computation of the variable tensor Eddington factor
(VTEF) closure term, and a matter-radiation coupling scheme which is
particularly robust for nonequilibrium problems. Numerical highlights include a
discussion of how our code is implemented for parallel execution and a
description of our scalable linear solver module. We present a suite of
numerical tests from which the virtues and vices of our method may be gleaned;
these include nonequilibrium Marshak waves, 2-D "shadow" tests showing the
one-sided illumination of an opaque cloud, and full RHD+VTEF simulations of
radiating shocks. We conclude that radiation moment solutions closed with
variable tensor Eddington factors show a dramatic qualitative improvement over
results obtained with flux-limited diffusion, and further that this approach
has a bright future in the context of parallel RHD simulations in astrophysics.


title:
Characterizing the Adaptive Optics Off-Axis Point-Spread Function - I: A
  Semi-Empirical Method for Use in Natural-Guide-Star Observations

abstract:
  Even though the technology of adaptive optics (AO) is rapidly maturing,
calibration of the resulting images remains a major challenge. The AO
point-spread function (PSF) changes quickly both in time and position on the
sky. In a typical observation the star used for guiding will be separated from
the scientific target by 10" to 30". This is sufficient separation to render
images of the guide star by themselves nearly useless in characterizing the PSF
at the off-axis target position. A semi-empirical technique is described that
improves the determination of the AO off-axis PSF. The method uses calibration
images of dense star fields to determine the change in PSF with field position.
It then uses this information to correct contemporaneous images of the guide
star to produce a PSF that is more accurate for both the target position and
the time of a scientific observation. We report on tests of the method using
natural-guide-star AO systems on the Canada-France-Hawaii Telescope and Lick
Observatory Shane Telescope, augmented by simple atmospheric computer
simulations. At 25" off-axis, predicting the PSF full width at half maximum
using only information about the guide star results in an error of 60%. Using
an image of a dense star field lowers this error to 33%, and our method, which
also folds in information about the on-axis PSF, further decreases the error to
19%.


title:
Asymmetric core combustion in neutron stars and a potential mechanism
  for gamma ray bursts

abstract:
  We study the transition of nuclear matter to strange quark matter (SQM)
inside neutron stars (NSs). It is shown that the influence of the magnetic
field expected to be present in NS interiors has a dramatic effect on the
propagation of a laminar deflagration (widely studied so far), generating a
strong acceleration of the flame in the polar direction. This results in a
strong asymmetry in the geometry of the just formed core of hot SQM which
resembles a cylinder orientated in the direction of the magnetic poles of the
NS. This geometrical asymmetry gives rise to a bipolar emission of the thermal
neutrino-antineutrino pairs produced in the process of SQM formation. The
neutrino-antineutrino pairs annihilate into electron-positron pairs just above
the polar caps of the NS giving rise to a relativistic fireball, thus providing
a suitable form of energy transport and conversion to gamma emission that may
be associated to short gamma ray bursts (GRBs).


title: XMM-Newton observes flaring in the polar UZ For during a low state

abstract:
  During an XMM-Newton observation, the eclipsing polar UZ For was found in a
peculiar state with an extremely low X-ray luminosity and occasional X-ray and
UV flaring. For most of the observation, UZ For was only barely detected in
X-rays and about 800 times fainter than during a high state previously observed
with ROSAT. A transient event, which lasted about 900 s, was detected
simultaneously by the X-ray instruments and, in the UV, by the Optical Monitor.
The transient was likely caused by the impact of 10^17-10^18 g of gas on the
main accretion region of the white dwarf. The X-ray spectrum of the transient
is consistent with 7 keV thermal bremsstrahlung from the shock-heated gas in
the accretion column. A soft blackbody component due to reprocessing of X-rays
in the white dwarf atmosphere is not seen. The likely origin of the UV emission
during the transient is cyclotron radiation from the accretion column. We
conclude from our analysis that the unusual flaring during the low state of UZ
For was caused by intermittent increases of the mass transfer rate due to
stellar activity on the secondary.


title:
Photoelectric Heating and [CII] Cooling of High Galactic Latitude
  Translucent Clouds

abstract:
  The (2P3/2 -> 2P1/2) transition of singly--ionized carbon, [CII], is the
primary coolant of diffuse interstellar gas. We describe observations of [CII]
emission towards nine high Galactic latitude translucent molecular clouds, made
with the long wavelength spectrometer on board the Infrared Space Observatory.
To understand the role of dust grains in processing the interstellar radiation
field (ISRF) and heating the gas, we compare the [CII] integrated intensity
with the far-infrared (FIR) integrated surface brightness for the 101 sampled
lines of sight. We find that [CII] is linearly correlated with FIR, and the
average ratio is equal to that measured with the COBE satellite for all
high-latitude Milky Way gas. There is a significant decrease that was not
detected with COBE in [CII] emissivity at high values of FIR. Our sample splits
naturally into two populations depending on the 60um/100um surface brightness
ratio, or color: ``warm'' positions and ``cold'' positions. A transition from
sources with warm to those with cold 60/100 colors coincides approximately with
the transition from constant to decreasing [CII] emissivity. We model the [CII]
and far-infrared emission under conditions of thermal equilibrium, using the
simplifying assumptions that, in all regions heated by the ISRF, the most
important source of gas heating is the photoelectric effect on grains and the
most important source of gas cooling is [CII] emission. The model matches the
data well. There are no statistically significant differences in the derived
values of the ISRF intensity and the photoelectric heating efficiency for warm
and cold sources. The observed variations in the [CII] emissivity and the
60/100 colors can be understood entirely in terms of the attenuation and
softening of the ISRF by translucent clouds, not changes in dust properties.


title: GD248B, The Coolest Known Helium Atmosphere White Dwarf

abstract:
  This is to notify colleagues that our ApJ paper and corresponding astro-ph
version are being withdrawn. Optical spectroscopy obtained with a 3m class
telescope gave no indication of any features in the spectrum of 'GD248B'
whatsoever. In addition to our proper motion data and optical photometry, all
was consistent with our original interpretation for this object. However, very
high SNR optical spectroscopy obtained at the Keck 10m revealed absorption
features and points to a background subdwarf K7/M0 star moving at very high
velocity with nearly identical proper motion to GD248, but alas, not a true
companion and hence not a cool white dwarf.


title:
The Wind Momentum-Luminosity relationship: blue supergiants in the
  spiral galaxy NGC 300

abstract:
  We have carried out the wind analysis of six A-type supergiants in NGC 300.
The derived Wind Momentum-Luminosity Relationship is compared with that of
Galactic and M31 blue supergiants and with theoretical models.


title: The Spatially-Resolved Mass Function of the Globular Cluster M22

abstract:
  HST imaging of M22 has allowed, for the first time, a detailed and uniform
mapping of mass segregation in a globular cluster. Luminosity and mass
functions from the turnoff down to the mid to lower main sequence are presented
for M22 in annular bins from the centre of the cluster out to five core radii.
Within the core, a significant enhancement is seen in the proportion of 0.5-0.8
M(sun) stars compared with their numbers outside the core. Numerical modelling
of the spatial mass spectrum of M22 shows that the observed degree of mass
segregation can be accounted for by relaxation processes within the cluster.
The global cluster mass function for M22 is flatter than the Salpeter IMF and
cannot be represented by a single power law.


title: Strong gravitational lensing: why no central black holes?

abstract:
  We investigate how central black holes (BHs) inhabited in galactic dark halos
could affect strong gravitational lensing. The distribution of integral lensing
probability with image separations are calculated for quasars of redshift 1.5
by foreground dark matter halos. The mass density of dark halos is taken to be
the Navarro-Frenk-White (NFW) profile such that, when the mass of a halo is
less than $10^{14} M_{\sun}$, its central black holes or a bulge is included as
a point mass. The relationship between the masses $M_{\bullet}$ of supermassive
black holes and the total gravitational mass $M_{\mathrm{DM}}$ of their host
galaxy is adopted from the most recent literature. Only a flat $\Lambda$CDM
model is considered here. It is shown that, while a single black hole for each
galaxy contributes considerable but not sufficient lensing probabilities at
small image separations compared with those without black holes, the bulges
(which are about 100--1000 times larger in mass than a typical black hole)
would definitely contribute enough probabilities at small image separations,
although it gives too high probabilities at large separation angles compared
with lensing observations.


title: Reflection at large distance from the central engine in Seyfert 1s

abstract:
  We consider the possibility that most of the reflection component, observed
in the hard X-ray spectra of Seyfert galaxies, could be formed on an extended
medium, at large distance from the central source of primary radiation (e.g. on
a torus). Then, the reflector cannot respond to the rapid fluctuations of the
primary source. The observed reflected flux is controlled by the time-averaged
primary spectrum rather than the instantaneous (observed) one. We show that
this effect strongly influences the spectral fit parameters derived under the
assumption of a reflection component consistent with the primary radiation. We
find that a pivoting primary power-law spectrum with a nearly constant
Comptonised luminosity may account for the reported correlation between the
reflection amplitude R and the spectral index Gamma, and simultaneously
produces an iron line EW that is nearly independent of Gamma. We emphasize the
effects of the modelling of the primary component on the determination of the
reflection amplitude, and show that in NGC 5548, when these effects are taken
into account, the RXTE data are consistent with the reflection features being
produced mainly at large distance from the central source.


title: No observational proof of the black-hole event-horizon

abstract:
  Recently, several ways of obtaining observational proof of the existence of
black-hole horizons have been proposed. We argue here that such proof is
fundamentally impossible: observations can provide arguments, sometimes very
strong ones, in favour of the existence of the event horizon, but they cannot
prove it. This applies also to future observations, which will trace very
accurately the details of the spacetime metric of a body suspected of being a
black hole.


title: Modelling Oscillations in the Jet Emission from Microquasar GRS 1915+105

abstract:
  The variability in the infrared to millimetre emission from microquasar GRS
1915+105 is believed to be dominated by the system's relativistic jet. In this
paper we develop a time-dependent version of the Blandford & Koenigl (1979) jet
emission model and apply it to the oscillations in the infrared and millimetre
emission from GRS 1915+105 observed by Fender & Pooley (2000). The resulting
model provides a reasonable description of the observed flux oscillations from
GRS 1915+105. From a fit of the observed time lag between the flux peaks in the
infrared and millimetre emission together with the flux normalisation we were
able to determine the model parameters for the GRS 1915+105 jet. We find that
to achieve the observed flux levels with the model requires an unphysically
large electron density within the jet. We therefore conclude that the Blandford
& Koenigl (1979) model cannot explain these observations, either because it
does not provide the correct description of the emission from microquasar jets,
or because the observed emission variations do not originate in the jet.


title: Aspherical Supernovae Explosions

abstract:
  Core collapse supernovae(SN) are the final stages of evolution in massive
stars during which the central region collapses. Recent explosion scenarios
assumed that the ejection is due to energy deposition by neutrinos into the
envelope but detailed models do not produce powerful explosions. There is new
and mounting evidence for an asphericity and, in particular, for axial symmetry
in several SNe which may be hard to reconcile within the spherical picture.
This evidence includes the observed high polarization and its variation with
time, pulsar kicks, high velocity iron-group and intermediate-mass elements
material observed in remnants, direct observations of the debris of SN1987A
etc. Some of the new evidence is discussed in more detail. To be in agreement
with the observations, any successful mechanism must invoke some sort of axial
symmetry for the explosion. We consider jet-induced/dominated explosions of
core collapse SNe. Our study is based on detailed 3-D hydrodynamical and
radiation transport models We find that the observations can be explained by
low velocity, massive jets which stall well within the SN envelope. Such
outflows may be produced by MHD- mechanisms, convective dominated accretion
disks on the central object or asymmetric neutrino emissions. Asymmetric
density/chemical distributions and, for SN2002ap, off-center energy depositions
have been identified as crucial for the interpretation of the polarization.


title: The mass and energy budget of Cassiopeia A

abstract:
  Further analysis of X-ray spectroscopy results recently obtained from the MOS
CCD cameras on-board XMM-Newton provides a detailed description of the hot and
cool X-ray emitting plasma in Cas A. Measurement of the Doppler broadening of
the X-ray lines is consistent with the expected ion velocities, ~1500 km/s
along the line of sight, in the post shock plasma. Assuming a constant total
pressure throughout the remnant we estimate the total remnant mass as 10 Msun
and the total thermal energy as 7E43 J. We derive the differential mass
distribution as a function of ionisation age for both X-ray emitting
components. This distribution is consistent with a hot component dominated by
swept up mass heated by the primary shock and a cool component which are
ablated clumpy ejecta material which were and are still being heated by
interaction with the preheated swept up material. We calculate a balanced mass
and energy budget for the supernova explosion giving 1E44 J in ejected mass;
approximately 0.4 Msun of the ejecta were diffuse with an initial rms velocity
of 15000 km/s while the remaining ~1.8 Msun were clumpy with an initial rms
velocity of ~2400 km/s. Using the Doppler velocity measurements of the X-ray
spectral lines we can project the mass into spherical coordinates about the
remnant. This provides quantitative evidence for mass and energy beaming in the
supernova explosion. The mass and energy occupy less than 4.5 sr (<40 % of the
available solid angle) around the remnant and 64 % of the mass occurs in two
jets within 45 degrees of a jet axis. We calculate a swept up mass of 7.9 Msun
in the emitting plasma and estimate that the total mass lost from the
progenitor prior to the explosion could be as high as ~20 Msun.


title: Microflaring of a solar Bright point

abstract:
  A solar X-ray Bright point (BP) was observed with the SUMER-spectrograph of
the SOHO-observatory. The data consist of four far-UV spectral lines formed
between 2 10^4 - 6 10^5 K, with 2 arcsec spatial, 2.8 min temporal and 4 km/s
spectral resolution. A striking feature is the strong microflaring and
appearance of several short lived transients. Using simultaneous magnetic field
measurements the region observed seemed to lie above a cancelling flux region.
With respect to the filling factor and emission measure this particular BP was
similar to the average surface of a moderately active solar type star.


title:
Is a minor-merger driving the nuclear activity in the Seyfert 2 galaxy
  NGC 2110?

abstract:
  We report on a detailed morphological and kinematic study of the isolated
non-barred nearby Seyfert 2 galaxy NGC 2110. We combine Integral Field optical
spectroscopy, with long-slit and WFPC2 imaging available in the HST archive to
investigate the fueling mechanism in this galaxy. Previous work (Wilson &
Baldwin 1985) concluded that the kinematic center of the galaxy is displaced
\~220 pc from the apparent mass center of the galaxy, and the ionized gas
follows a remarkably normal rotation curve. Our analysis based on the stellar
kinematics, 2D ionized gas velocity field and dispersion velocity, and high
spatial resolution morphology at V, I and Halpha reveals that: 1) The kinematic
center of NGC 2110 is at the nucleus of the galaxy. 2) The ionized gas is not
in pure rotational motion. 3) The morphology of the 2D distribution of the
emission line widths suggests the presence of a minor axis galactic outflow. 4)
The nucleus is blue-shifted with respect to the stellar systemic velocity,
suggesting the NLR gas is out-flowing due to the interaction with the radio
jet. 5) The ionized gas is red-shifted ~100 km/s over the corresponding
rotational motion south of the nucleus, and 240 km/s with respect to the
nuclear stellar systemic velocity. This velocity is coincident with the HI
red-shifted absorption velocity detected by Gallimore et al (1999). We discuss
the possibility that the kinematics of the south ionized gas could be perturbed
by the collision with a small satellite that impacted on NGC 2110 close to the
center with a highly inclined orbit. Additional support for this interpretation
are the radial dust lanes and tidal debris detected in the V un-sharp masked
image. We suggest that a minor-merger may have driven the nuclear activity in
NGC 2110.


title:
The Assembly and Merging History of Supermassive Black Holes in
  Hierarchical Models of Galaxy Formation

abstract:
  We assess models for the assembly of supermassive black holes (SMBHs) at the
center of galaxies that trace their hierarchical build-up far up in the dark
halo `merger tree'. We assume that the first `seed' black holes (BHs) formed in
(mini)halos collapsing at z=20 from high-sigma density fluctuations. As these
pregalactic holes become incorporated through a series of mergers into larger
and larger halos, they sink to the center owing to dynamical friction, accrete
a fraction of the gas in the merger remnant to become supermassive, form a
binary system, and eventually coalesce. The merger history of dark matter halos
and associated BHs is followed by cosmological Monte Carlo realizations of the
merger hierarchy. A simple model, where quasar activity is driven by major
mergers and SMBHs accrete at the Eddington rate a mass that scales with the
fifth power of the velocity dispersion, is shown to reproduce the optical LF of
quasars in the redshift range 1<z<4. Binary and triple BH interactions are
followed in our merger tree. The assumptions underlying our scenario lead to
the prediction of a population of massive BHs wandering in galaxy halos and the
intergalactic medium at the present epoch, and contributing <10% to the total
BH mass density. At all epochs the fraction of binary SMBHs in galaxy nuclei is
of order 10%, while the fraction of binary quasars is less than 0.3%


title:
Spectral and Timing Properties of the Low-mass X-ray Binary 4U 0614+09
  with XMM-Newton

abstract:
  4U 0614+09 is a low-mass X-ray binary with a weakly magnetized neutron star
primary. It shows variability on time scales that range from years down to ~0.8
milliseconds. Before the Chandra and XMM-Newton era, emission features around
0.7 keV have been reported from this source, but recent Chandra observations
failed to detect them. Instead, these observations suggest an overabundance of
Ne in the absorbing material, which may be common to ultracompact (P_{orb}
\simless 1 hour) systems with a neon-rich degenerate dwarf secondary. We
observed 4U 0614+09 with XMM-Newton in March 2001. Here we present the energy
spectra, both from the RGS and EPIC cameras, and the Fourier power spectra from
EPIC high-time resolution light curves, which we use to characterize the
spectral state of the source.


title:
Fast X-ray Oscillations and General Relativity effects in Neutron star
  systems

abstract:
  Kilohertz quasi-periodic oscillations (kHz QPOs) are probably caused by
matter in Keplerian orbit at some preferred radius in the accretion disc around
a compact star. In a given source, QPO frequencies can drift by a few hundred
Hz following changes of the inner disc radius; but the disc cannot move closer
to the star than the radius of the innermost stable circular orbit (ISCO)
predicted by general realtivity, hence the kHz QPO frequencies must be limited
by some maximum frequency.


title:
First observation of a transition between "parallel tracks" in the kHz
  QPO frequency vs. intensity diagram

abstract:
  Contrary to theoretical expectations, observations with the Rossi X-ray
Timing Explorer (RXTE) show that in X-ray binaries timing properties are not
uniquely correlated with X-ray luminosity. For instance, although the
frequencies of the kilohertz quasi-periodic oscillations (kHz QPOs) correlate
with X-ray flux on short (~few hours) time scales, on time scales longer than a
day the QPO appears at more or less the same frequency, whereas the luminosity
may be a factor of a few different. The result is a set of almost parallel
tracks in a QPO frequency vs. X-ray flux plot. Despite the "parallel tracks"
are a common phenomenon among kHz QPO sources, until now, after five years of
observations with RXTE, not a single transition between two of these tracks had
been seen. Here I present the first detection of such a transition, in 4U
1636-53.


title:
Kilohertz quasi-periodic oscillations and strong field gravity in X-ray
  binaries

abstract:
  In the past five years observations with the Rossi X-ray Timing Explorer have
revealed fast quasi-periodic oscillations in the X-ray flux of about 20 X-ray
binaries. Thought to originate close to the surface of a neutron star, these
oscillations provide unique information about the strong gravitational field in
which they are produced.


title:
Flavor oscillations in the supernova hot bubble region: Nonlinear
  effects of neutrino background

abstract:
  The neutrino flux close to a supernova core contributes substantially to
neutrino refraction so that flavor oscillations become a nonlinear phenomenon.
One unexpected consequence is efficient flavor transformation for
anti-neutrinos in a region where only neutrinos encounter an MSW resonance or
vice versa. Contrary to previous studies we find that in the neutrino-driven
wind the electron fraction Y_e always stays below 0.5, corresponding to a
neutron-rich environment as required by r-process nucleosynthesis. The relevant
range of masses and mixing angles includes the region indicated by LSND, but
not the atmospheric or solar oscillation parameters.


title:
Long-term photometric behaviour of XZ Dra Binarity or magnetic cycle of
  a Blazhko type RRab star

abstract:
  The extended photometry available for XZ Dra, a Blazhko type RR Lyrae star,
makes it possible to study its long-term behavior. It is shown that its
pulsation period exhibit cyclic, but not strictly regular variations with
approx. 7200 d period. The Blazhko period (approx. 76 d) seems to follow the
observed period changes of the fundamental mode pulsation with dP_B/dP_0=7.7 x
10^4 gradient. Binary model cannot explain this order of period change of the
Blazhko modulation, nevertheless it can be brought into agreement with the O-C
data of the pulsation. The possibility of occurrence of magnetic cycle is
raised.


title: The XEUS Mission

abstract:
  XEUS, the X-ray Evolving Universe Spectroscopy mission, is at present an
ESA-ISAS initiative for the study of the evolution of the hot Universe in the
post-Chandra/XMM-Newton era. The key science objectives of XEUS are: Search for
the origin, and subsequent study of growth, of the first massive black holes in
the early Universe; assessment of the formation of the first gravitationally
bound dark matter dominated systems and their evolution; study of the evolution
of metal synthesis up till the present epoch; characterization of the true
intergalactic medium.
  To reach these ambitious science goals the two salient characteristics of the
XEUS observatory entail: (1) Its effective spectroscopic grasp, combining a
sensitive area > 20 m^2 below 2 keV with a spectral resolution better than 2
eV. This allows significant detection of the most prominent X-ray emission
lines (e.g. O-VII, Si-XIII and Fe-XXV) in cosmologically distant sources
against the sky background; (2) Its angular resolving power, between 2 and 5
arc seconds, to minimize source confusion as well as noise due to the galactic
X-ray foreground emission.
  To accommodate these instrument requirements a mission concept has been
developed featuring an X-ray telescope of 50-m focal length, comprising two
laser-locked (separate) mirror and detector spacecraft's. The telescope is
injected in a low earth orbit with an inclination commensurate with the ISS. At
present an on-orbit growth of the mirror spacecraft is foreseen with the aid of
the ISS, raising the mirror diameter from 4.5 to 10 m. The detector spacecraft
will be replaced at 5 year intervals after run-out of consumables with an
associated upgrade of the focal plane package.


title:
86 GHz SiO maser survey of late-type stars in the Inner Galaxy. I.
  Observational data

abstract:
  We present 86 GHz (v = 1, J = 2 -1) SiO maser line observations with the IRAM
30-m telescope of a sample of 441 late-type stars in the Inner Galaxy (-4 degr
< l < +30 degr). These stars were selected on basis of their infrared
magnitudes and colours from the ISOGAL and MSX catalogues. SiO maser emission
was detected in 271 sources, and their line-of-sight velocities indicate that
the stars are located in the Inner Galaxy. These new detections double the
number of line-of-sight velocities available from previous SiO and OH maser
observations in the area covered by our survey and are, together with other
samples of e.g. OH/IR stars, useful for kinematic studies of the central parts
of the Galaxy.


title: Large-Scale Structure from Galaxy and Cluster Surveys

abstract:
  I review the status of large-scale structure studies based on redshift
surveys of galaxies and clusters of galaxies. In particular, I compare recent
results on the power spectrum and two-point correlation correlation function
from the 2dF and REFLEX surveys, highlighting the advantage of X-ray clusters
in the comparison to cosmological models, given their easy-to-understand mass
selection function. Unlike for galaxies, this allows the overall normalization
of the power spectrum to be measured directly from the data, providing an extra
constraint on the models. In the context of CDM models, both the shape and
amplitude of the REFLEX P(k) require, consistently, a low value for the mean
matter density $\Omega_M$. This shape is virtually indistinguishable from that
of the galaxy power spectrum measured by the 2dF survey, simply multiplied by a
constant cluster-galaxy bias factor. This consistency is remarkable for data
sets which use different tracers and are very different in terms of selection
function and observational biases. Similarly, the knowledge of the power
spectrum normalization yields naturally a value $b\simeq 1$ for the bias
parameter of $b_J$-selected (as in 2dF) galaxies, also in agreement with
independent estimates using higher-order clustering and CMB data. In the final
part, I briefly describe the measurements of the matter density parameter from
redshift space distortions in galaxy surveys, and show evidence for similar
streaming motions of clusters in the REFLEX redshift-space correlation function
$\xi(r_p,\pi)$. With no exception, this wealth of independent clustering
measurements point in a remarkably consistent way towards a low-density CDM
Universe with $\Omega_M\simeq 0.3$.


title: Constraining the shape of the CMB: a Peak-by-Peak analysis

abstract:
  The recent measurements of the power spectrum of Cosmic Microwave Background
anisotropies are consistent with the simplest inflationary scenario and big
bang nucleosynthesis constraints. However, these results rely on the assumption
of a class of models based on primordial adiabatic perturbations, cold dark
matter and a cosmological constant. In this paper we investigate the need for
deviations from the $\Lambda$-CDM scenario by first characterizing the spectrum
using a phenomenological function in a 15 dimensional parameter space. Using a
Monte Carlo Markov chain approach to Bayesian inference and a low curvature
model template we then check for the presence of new physics and/or systematics
in the CMB data. We find an almost perfect consistency between the
phenomenological fits and the standard $\Lambda$-CDM models. The improved
spectral resolution expected from future satellite experiments is warranted for
a definitive test of the scenario.


title:
Molecular line study of the very young protostar IRAM 04191 in Taurus:
  Infall, rotation, and outflow

abstract:
  We present a detailed millimeter line study of the circumstellar environment
of the low-luminosity Class 0 protostar IRAM 04191+1522 in the Taurus molecular
cloud. New line observations demonstrate that the ~14000 AU radius protostellar
envelope is undergoing both extended infall and fast, differential rotation.
Radiative transfer modeling of multitransition CS and C34S maps indicate an
infall velocity v_inf ~ 0.15 km/s at r ~ 1500 AU and v_inf ~ 0.1 km/s up to r ~
11000 AU, as well as a rotational angular velocity Omega ~ 3.9 x 10^{-13}
rad/s, strongly decreasing with radius beyond 3500 AU down to a value Omega ~
1.5-3 x 10^{-14} rad/s at ~ 11000 AU. Two distinct regions, which differ in
both their infall and their rotation properties, therefore seem to stand out:
the inner part of the envelope (r ~< 2000-4000 AU) is rapidly collapsing and
rotating, while the outer part undergoes only moderate infall/contraction and
slower rotation. These contrasted features suggest that angular momentum is
conserved in the collapsing inner region but efficiently dissipated due to
magnetic braking in the slowly contracting outer region. We propose that the
inner envelope is in the process of decoupling from the ambient cloud and
corresponds to the effective mass reservoir (~0.5 M_sun) from which the central
star is being built. Comparison with the rotational properties of other objects
in Taurus suggests that IRAM 04191 is at a pivotal stage between a prestellar
regime of constant angular velocity enforced by magnetic braking and a
dynamical, protostellar regime of nearly conserved angular momentum. The
rotation velocity profile we derive for the inner IRAM 04191 envelope should
thus set some constraints on the distribution of angular momentum on the scale
of the outer Solar system at the onset of protostar/disk formation.


title: The Rotation of Binary Systems with evolved Components

abstract:
  In the present study we analyze the behavior of the rotational velocity,
vsini, for a large sample of 134 spectroscopic binary systems with a giant star
component of luminosity class III, along the spectral region from middle F to
middle K. The distribution of vsini as a function of color index (B-V) seems to
follow the same behavior as their single counterparts, with a sudden decline
around G0III. Blueward of this spectral type, namely for binary systems with a
giant F-type component, one sees a trend for a large spread in the rotational
velocities, from a few km/s to at least 40km/s. Along the G and K spectral
regions there is a considerable number of binary systems with moderate to
moderately high rotation rates. This reflects the effects of synchronization
between rotation and orbital motions. These rotators have orbital periods
shorter than about 250 days and circular or nearly circular orbits. Except for
these synchronized systems, the large majority of binary systems with a giant
component of spectral type later than G0III are composed of slow rotators.


title:
A high-resolution study of the evolution of the Lyman alpha forest in
  the redshift interval 0.9 < z < 1.7

abstract:
  Spectroscopy with HST/STIS Echelle and VLT/UVES of the bright QSO HE
0515-4414 (z_em =1.73, B = 15.0) offers for the first time the opportunity to
study the Lyman alpha forest in the redshift range 0.9 < z < 1.7 at a
resolution ~ 10 km/s. The number density evolution of the Lyman alpha lines is
well described by the power law approach dn/dz = (dn/dz)_0 (1+z)^gamma. We
derive gamma = 2.23 +/- 1.21 for the strong lines (13.64 < log N_HI < 16.00),
in agreement with the Lyman alpha forest evolution for z > 1.7. The expected
slow-down in their evolution does not appear earlier than z ~ 1. For the weak
lines (13.10 < log N_HI < 14.00) we find that the HE 0515-4414 data for z > 1
follow the trend with gamma = 1.40 known from z > 1.7 observations, i.e. we
confirm the difference in evolution between weak and strong lines. We use the
two-point velocity correlation function (TPCF) to search for clustering of the
Lyman alpha lines, yet we detect no excess in the TPCF on scales up to 10,000
km/s.


title: Chandra temperature and metallicity maps of the Perseus cluster core

abstract:
  We present temperature and metallicity maps of the Perseus cluster core
obtained with the Chandra X-ray Observatory. We find an overall temperature
rise from ~3.0 keV in the core to ~5.5 keV at 120 kpc and a metallicity profile
that rises slowly from ~0.5 solar to ~0.6 solar inside 60 kpc, but drops to
\~0.4 solar at 120 kpc. Spatially resolved spectroscopy in small cells shows
that the temperature distribution in the Perseus cluster is not symmetrical.
There is a wealth of structure in the temperature map on scales of ~10 arcsec
(5.2 kpc) showing swirliness and a temperature rise that coincides with a
sudden surface brightness drop in the X-ray image. We obtain a metallicity map
of the Perseus cluster core and find that the spectra extracted from the two
central X-ray holes as well as the western X-ray hole are best-fit by gas with
higher temperature and higher metallicity than is found in the surroundings of
the holes. A spectral deprojection analysis suggests, however, that this is due
to a projection effect; for the northern X-ray hole we find tight limits on the
presence of an isothermal component in the X-ray hole, ruling out
volume-filling X-ray gas with temperatures below 11 keV at 3 sigma.


title:
Inverse square law for the starter intensity of the discrete ordinates
  method in spherical geometry

abstract:
  The angular derivative of the standard form of the transfer equation is shown
to have a non-zero value for the radiation normal incidence. This is
demonstrated by a rigorous proof. The transfer equation for the starter
intensity turned out to be Euler first order equation its solution obeys the
inverse square law.


title: On the Interferometric Sizes of Young Stellar Objects

abstract:
  Long-baseline optical interferometers can now detect and resolve hot dust
emission thought to arise at the inner edge of circumstellar disks around young
stellar objects (YSOs). We argue that the near-infrared sizes being measured
are closely related to the radius at which dust is sublimated by the stellar
radiation field. We consider how realistic dust optical properties and gas
opacity dramatically affect the predicted location of this dust destruction
radius, an exercise routinely done in other contexts but so far neglected in
the analysis of near-infrared sizes of YSOs. We also present the accumulated
literature of near-infrared YSO sizes in the form of a ``size-luminosity
diagram'' and compare with theoretical expectations. We find evidence that
large (>~ 1 micron) dust grains predominate in the inner disks of T Tauri and
Herbig Ae/Be stars, under the assumption that the inner-most gaseous disks are
optically-thin at visible wavelengths.


title: Cosmological Parameters, Dark Energy and Large Scale Structure

abstract:
  We review the current status of cosmological parameters, dark energy and
large-scale structure, from a theoretical and observational perspective. We
first present the basic cosmological parameters and discuss how they are
measured with different observational techniques. We then describe the recent
evidence for dark energy from Type Ia supernovae. Dynamical models of the dark
energy, quintessence, are then described, as well as how they relate to
theories of gravity and particle physics. The basic theory of structure
formation via gravitational instability is then reviewed. Finally, we describe
new observational probes of the large-structure of the universe, and how they
constrain cosmological parameters.


title: A Planet at 5 AU Around 55 Cancri

abstract:
  We report precise Doppler shift measurements of 55 Cancri (G8V) obtained from
1989 to 2002 at Lick Observatory. The velocities reveal evidence for an outer
planetary companion to 55 Cancri orbiting at 5.5 AU. The velocities also
confirm a second, inner planet at 0.11 AU. The outer planet is the first
extrasolar planet found that orbits near or beyond the orbit of Jupiter. It was
drawn from a sample of ~50 stars observed with sufficient duration and quality
to detect a giant planet at 5 AU, implying that such planets are not rare. The
properties of this jupiter analog may be compared directly to those of the
Jovian planets in our Solar System. Its eccentricity is modest, e=0.16,
compared with e=0.05 for both Jupiter and Saturn. Its mass is at least 4.0
jupiter masses (M sin i). The two planets do not perturb each other
significantly. Moreover, a third planet of sub-Jupiter mass could easily
survive in between these two known planets. Indeed a third periodicity remains
in the velocity measurements with P = 44.3 d and a semi-amplitude of 13 m/s.
This periodicity is caused either by a third planet at a=0.24 AU or by
inhomogeneities on the stellar surface that rotates with period 42 d. The
planet interpretation is more likely, as the stellar surface is quiet,
exhibiting log(R'_{HK}) = -5.0 and brightness variations less than 1 millimag,
and any hypothetical surface inhomogeneity would have to persist in longitude
for 14 yr. Even with all three planets, an additional planet of
terrestrial--mass could orbit stably at ~1 AU. The star 55 Cancri is apparently
a normal, middle-aged main sequence star with a mass of 0.95 solar masses, rich
in heavy elements ([Fe/H] = +0.27). This high metallicity raises the issue of
the relationship between its age, rotation, and chromosphere.


title: Comment on "Measuring the black hole masses of high redshift quasars"

abstract:
  In a recent paper, McLure & Jarvis (2002, astro-ph/0204473, v.1) reanalyze
AGN broad-line reverberation measurements presented in Kaspi et al. (2000).
They find the broad-line region size and the AGN luminosity at 5100 Ang can be
related by R_{BLR} ~ L_{5100}^{0.5}. This differs from the result of Kaspi et
al., who found R_{BLR} ~ L_{5100}^{0.7}, a departure from expectations for a
constant ionization parameter. In this note I investigate the source of the
discrepancy. McLure & Jarvis use quasar luminosities based on the single-epoch,
multichannel-spectrophotometer measurements of Neugebauer et al. (1987),
obtained in 1980. I show that the Neugebauer et al. fluxes are systematically
higher, by a constant flux offset, compared with the multi-epoch CCD
measurements of Kaspi et al., obtained concurrently with the echo-mapping
radii. In addition, McLure & Jarvis erred when converting these fluxes to
luminosities. The two effects compound to a typical factor 2 (0.3 dex)
overestimate of the luminosities of the PG quasars in the sample. Since McLure
& Jarvis did adopt the Seyfert luminosities in Kaspi et al. (2000), they
obtained a slope that is flatter by 0.2.


title:
Pulse phase variations of the X-ray spectral features in the radio-quiet
  neutron star 1E 1207-5209

abstract:
  We present the results of an XMM-Newton observation of the radio-quiet X-ray
pulsar 1E 1207-5209 located at the center of the shell-like supernova remnant
G296.5+10.0. The X-ray spectrum is characterized by the presence of two
phase-dependent absorption lines at energies ~0.7 keV and ~1.4 keV. Moreover,
these broad spectral features have significant substructure, suggesting that
they are due to the blending of several narrower lines. We interpret such
features as evidence for an atmosphere containing metals and a magnetic field
value of a few 10^12 G, consistent with the observed spin-down rate
P_dot=(1.98+/-0.83)*10^(-14) s/s. Since 1E 1207-5209 is the only X-ray emitting
pulsar showing evidence of such features, we tentatively link them to the
unique combination of age and energetics that characterize this object. We
suggest that a young age and a low level of magnetospheric activity are
favorable conditions for the detection of atomic spectral features from metals
in neutron star atmospheres, which would be either blanketed by a thin layer of
accreted hydrogen in older objects or masked by non-thermal processes in young
energetic pulsars.