title: H2, D/H and the CMBR Temperature at z = 3.025 Toward QSO 0347-3819

abstract:
  A new molecular hydrogen cloud has been identified at z = 3.025 in the
absorption-line spectrum of the quasar 0347-3819 observed with the UVES
spectrograph at the VLT/Kueyen telescope. At the same redshift numerous metal
lines and the DI Ly-5, Ly-8, Ly-10, and Ly-12 lines were detected. The
simultaneous analysis of metal and hydrogen lines yielded D/H = (3.75 +/- 0.25)
10^{-5}. This value is consistent with SBBN if the baryon-to-photon ratio, eta,
lies within the range 4.4 10^{-10} <= eta <= 5.3 10^{-10}, implying Omega_b
h^2_{100} = 0.018 +/- 0.002 (1 sigma c.l.). The population of the ground state
rotational levels of H2 from J = 0 to 5 revealed a Galactic-type UV radiation
field in the H2-bearing cloud ruling out UV pumping as an important mechanism
for CII. Accounting for two other important excitation mechanisms such as
collisions and FIR photon absorption, we were able to measure for the first
time the temperature of the cosmic background radiation at z > 3, T_{CMBR} =
12.1^{+1.7}_{-3.2} K, from the analysis of the CII fine-structure lines. This
result supports the value of T_{CMBR} = 10.968 +/- 0.004 K predicted at z =
3.025 by the hot Big Bang cosmology.


title:
The Chemical Evolution of the Solar Neighbourhood: the Effect of
  Binaries

abstract:
  In this paper we compute the time evolution of the elements (4He, 12C, 14N,
16O, 20Ne, 24Mg, 28Si, 32S, 40Ca and 56Fe) and of the supernova rates in the
solar neighbourhood by means of a galactic chemical evolutionary code that
includes in detail the evolution of both single and binary stars. Special
attention is payed to the formation of black holes.
  Our main conclusions: in order to predict the galactic time evolution of the
different types of supernovae, it is essential to compute in detail the
evolution of the binary population, the observed time evolution of carbon is
better reproduced by a galactic model where the effect is included of a
significant fraction of intermediate mass binaries, massive binary mass
exchange provides a possible solution for the production of primary nitrogen
during the very early phases of galactic evolution, chemical evolutionary
models with binaries or without binaries but with a detailed treatment of the
SN Ia progenitors predict very similar age-metallicity relations and very
similar G-dwarf distributions whereas the evolution of the yields as function
of time of the elements 4He, 16O, 20Ne, 24Mg, 28Si, 32S and 40Ca differ by no
more than a factor of two or three, the observed time evolution of oxygen is
best reproduced when most of the oxygen produced during core helium burning in
ALL massive stars serves to enrich the interstellar medium. This can be used as
indirect evidence that (massive) black hole formation in single stars and
binary components is always preceded by a supernova explosion.


title:
Astrometric Microlensing of Distant Sources due to the Stars in the
  Galaxy

abstract:
  We investigate properties of astrometric microlensing of distant sources
(such as QSOs and radio galaxies) caused by stars in the Galaxy, mainly
focusing on application to the VERA (VLBI Exploration of Radio Astrometry)
project. Assuming typical parameters for the Galaxy disk and bulge, we show
that the maximum optical depth for astrometric shift of 10 micro-arcsec level
is 8.9x10^{-2} for QSO-disk lensing case and 3.8x10^{-2} for QSO-bulge lensing
case. We also find that the maximum optical depth for QSO-disk lensing is
larger by an order of magnitude than that for disk-disk or bulge-disk lensing
case (assuming a typical source distance of 8 to 10 kpc). In addition to
optical depth, we also calculate the event rate and find that the maximum event
rate for QSO-disk lensing case is 1.2x10^{-2} event per year, which is about 30
times greater than that for disk-disk lensing case. This high event rate
implies that if one monitors 10 QSOs behind the Galactic center region for 10
years, at least one astrometric microlensing event should be detected.
Therefore, monitoring distant radio sources with VERA can be a new tool to
study astrometric microlensing caused by stars in the Galaxy. We discuss the
implications of astrometric microlensing for VERA by focusing on estimating the
lens mass, and also present some possible candidates of radio sources toward
which astrometric microlensing events should be searched for with VERA.
(abridged)


title: Self-similar cosmological expansion of collisional gas

abstract:
  We derive similarity solutions for the expansion of negative initial density
perturbations \delta M/M \propto r^-s (s>0) in an Einstein-de Sitter universe
filled with collisional baryonic gas and collisionless matter. The solutions
are obtained for planar, cylindrical, and spherical perturbations. For steep
perturbations, central cavities surrounded by over-dense shells expanding as
t^{2(s+1)/3s} develop in both matter components. We also consider the case when
baryonic shells are driven by internal pressure. Before redshift \sim 8-10
baryonic shells cool by inverse Compton scattering with the cosmic background
radiation and can form bound objects of mass \sim 10^11\Omega_b^{-1/2}
M_{\odot} (1+z)^{-3/2}. Hot shocks of radius R cause a Compton y-distortion of
order y=10^{-5}\Omega_b (R/10 Mpc)^2 f_F, where f_F is the volume filling
factor of these shells.


title: Quantum-gravity phenomenology with gamma rays and UHE cosmic rays

abstract:
  In recent years several ideas for experimental searches of effects induced by
quantum properties of space-time have been discussed. Some of these ideas
concern the role in quantum spacetime of the ordinary Lorentz symmetry of
classical flat spacetime. Deviations from ordinary (classical) Lorentz symmetry
are now believed to be rather natural in non-commutative space-times, models
based on String Theory and models based on Loop Quantum Gravity. Observations
of gamma rays and ultra-high-energy cosmic rays could play a key role in the
development of this research programme.


title: X-ray transient AGN and galaxies, and why we need new soft X-ray surveys

abstract:
  X-ray transience is the most extreme form of variability observed in AGN or
normal non-active galaxies. While factors of 2-3 on timescales of days to years
are quite common among AGN, X-ray transients appear only once and vanish from
the X-ray sky years later. The ROSAT All-Sky Survey with its sensitivity to
energies down to 0.1 keV was the an ideal tool to discover these sources. X-ray
transience in AGN or galaxies can be caused by dramatic changes in the
accretion rate of the central black hole or by changes of the properties of the
accretion disk. So far only a handful of sources are known. In order to
estimate how often such an event occurs in a galaxy, a new soft X-ray survey is
needed. In these proceedings I describe the currently known X-ray transient AGN
and galaxies and will argue for a new soft X-ray survey in order to discover
more of these extreme X-ray sources.


title:
Diffraction-limited speckle interferometry and modeling of the
  circumstellar envelope of R CrB at maximum and minimum light

abstract:
  We present the first speckle interferometric observations of R CrB, the
prototype of a class of peculiar stars which undergo irregular declines in
their visible light curves. The observations were carried out with the 6m
telescope at the Special Astrophysical Observatory near maximum light (V=7,
1996 Oct. 1) and at minimum light (V=10.61, 1999 Sep. 28). A spatial resolution
of 75mas was achieved in the K-band. The dust shell around R CrB is partially
resolved, and the visibility is approximately 0.8 at a spatial frequency of 10
cycles/arcsec. The two-dimensional power spectra obtained at both epochs do not
show any significant deviation from circular symmetry. The visibility function
and spectral energy distribution obtained near maximum light can be
simultaneously fitted with a model consisting of the central star and an
optically thin dust shell with density proportional to r^-2. The inner boundary
of the shell is found to be 82Rstar (19mas) with a temperature of 920K.
However, this simple model fails to simultaneously reproduce the visibility and
spectral energy distribution obtained at minimum light. We show that this
discrepancy can be attributed to thermal emission from a newly formed dust
cloud.


title: Probing the evolution of massive galaxies with the K20 survey

abstract:
  The motivations and the status of the K20 survey are presented. The first
results on the evolution of massive galaxies and the comparison with the
predictions of the currently competing scenarios of galaxy formation are also
discussed.


title:
Experimental study of a proximity focusing Cherenkov counter prototype
  for the AMS experiment

abstract:
  A study prototype of Proximity Focussing Ring Imaging Cherenkov counter has
been built and tested with several radiators using separately cosmic-ray
particles and 12C beam fragmentation products at several energies. Counter
prototype and experimental setup are described, and the results of measurements
reported and compared with simulation results.The performances are discussed in
the perspective of the final counter design.


title: Tidally induced radial-velocity variations in close binaries

abstract:
  A theoretical framework for the determination of tidally induced
radial-velocity variations in a component of a close binary is presented. Both
the free and the forced oscillations of the component are treated as linear,
isentropic perturbations of a spherically symmetric star. Resonances between
dynamic tides and free oscillation modes are taken into account by means of the
formalism developed by Smeyers et al. (1998). The amplitude of the tidally
induced radial-velocity variations seen by the observer depends on the orbital
eccentricity and on the orbital inclination. The amplitude increases with
increasing orbital eccentricity and is most sensitive to the value of the
orbital inclination when 20 < i < 70. In the case of a 5 solar mass ZAMS star
with a 1.4 solar mass compact companion, it is shown that resonant dynamic
tides can lead to radial-velocity variations with amplitudes large enough to be
detected in observations. The shape of the tidally induced radial-velocity
curves varies from very irregular for orbital periods away from any resonances
with free oscillation modes to sinusoidal for orbital periods close to a
resonance with a free oscillation mode. Our investigation is concluded with an
application to the slowly pulsating B star HD 177863 showing the possibility of
resonant excitation of a high-order second-degree g-mode in this star.


title: Search for star clusters close to the Galactic plane with DENIS

abstract:
  An automated search for star clusters close to the Galactic plane (|b| < 5
deg) was carried out on the Point Source Catalogue of the DENIS survey. 44% of
the Galactic plane have been observed and calibrated. The method allowed to
retrieve 22 known star clusters and to identify two new ones, not published yet
although previously presented in the 2MASS web site as embedded clusters in HII
regions. Extinction in the field and in front of the clusters are estimated
using a model of population synthesis. We present the method and give the
properties of these clusters.


title:
Event rates and timescale distributions from realistic microlensing
  models of M31

abstract:
  We provide a set of microlensing event rate maps for M31, the Andromeda
Galaxy. Rates for M31 microlensing were calculated on the basis of a four
component model of the lens and source populations: disk and bulge sources
lensed by bulge, disk, M31 halo and Galactic halo lenses. We confirm the high
rate gradient along the minor axis of M31 due to a dark halo of lenses.
Furthermore, we compute the timescale distributions of events, for both
Einstein times and full-width at half-maximum times. We explore how the rate
contours and the timescale distributions can be used to measure the shape and
extent of the microlensing halo. With one year of twice--weekly sampling, or
three observing seasons, a halo MACHO fraction as small as 5% can be detected
with modest ground based telescopes.


title:
The runaway growth of intermediate-mass black holes in dense star
  clusters

abstract:
  We study the growth rate of stars via stellar collisions in dense star
clusters, calibrating our analytic calculations with direct N-body simulations
of up to 65536 stars, performed on the GRAPE family of special-purpose
computers. We find that star clusters with initial half-mass relaxation times
of about 25 Myr are dominated by stellar collisions, the first collisions
occurring at or near the point of core collapse, which is driven by the
segregation of the most massive stars to the cluster center, where they end up
in hard binaries. The majority of collisions occur with the same star,
resulting in the runaway growth of a supermassive object. This object can grow
up to about 0.1% of the mass of the entire star cluster and could manifest
itself as an intermediate-mass black hole (IMBH). The phase of runaway growth
lasts until mass loss by stellar evolution arrests core collapse. Star clusters
older than about 5 Myr and with present-day half-mass relaxation times less
than 100 Myr are expected to contain an IMBH.


title: Cosmological implications of old galaxies at high redshifts

abstract:
  Old high-$z$ galaxies are important tools for understanding the structure
formation problem and may become the key to determine the ultimate fate of the
Universe. In this {\it letter}, the inferred ages of the three oldest galaxies
at high redshifts reported in the literature are used to constrain the first
epoch of galaxy formation and to reanalyse the high-z time scale crisis. The
lower limits on the formation redshift $z_f$ depends on the quantity of cold
dark matter in the Universe. In particular, if $\Omega_m\geq 0.37$ these
galaxies are not formed in FRW cosmologies with no dark energy. This result is
in line with the Supernovae type Ia measurements which suggest that the bulk of
energy in the Universe is repulsive and appears like an unknown form of dark
energy component. In a complementar analysis, unlike recent claims favoring the
end of the age problem, it is shown that the Einstein-de Sitter model is
excluded at high-z by $\sim 3\sigma$.


title: The lensing system towards the doubly imaged quasar SBS 1520+530

abstract:
  The gravitational potential responsible for the lensing effect in SBS
1520+530 is studied over length scales from a few arc-seconds to a few
arc-minutes. For this purpose, we use sharply deconvolved Hubble Space
Telescope images in the optical and near-IR, in combination with ground based
optical data obtained over a wider field-of-view. In particular, we have
carried out a multi-color analysis in order to identify groups or clusters of
galaxies along the line of sight. Photometric redshifts are measured for 139
galaxies unveiling significant excesses of galaxies 1.0 arcmin, NW and 1.7
arcmin, SW of the main lensing galaxy. The photometric redshift inferred both
for the main lensing galaxy and for the galaxy concentrations is
z=0.9^{+0.10}_{-0.25}. This is in rough agreement with the measured
spectroscopic redshift of the main lensing galaxy, z=0.71 (Burud et al. 2002),
suggesting that it is part of a larger group or cluster. We investigate the
impact of including the galaxy cluster, first on the modelling of the lensing
system, and second on the expected time--delay between the two quasar images.


title:
Chandra Discovery of a Tree in the X-ray Forest towards PKS 2155-304:
  the Local Filament?

abstract:
  We present the first X-ray detection of resonant absorption from warm/hot
local gas either in our Galaxy, or in the Intergalactic space surrounding our
Galaxy, along the line of sight toward the blazar PKS 2155-304. The Chandra
HRCS-LETG spectrum of this z=0.116 source clearly shows unresolved OVII(Ka) and
NeIX(Ka) resonant absorption lines at 21.603 A and 13.448 A (i.e. cz =
[-340--200] km/s in the rest frame, from the OVII line). OVIII(Ka) and OVII(Kb)
from the same system are also detected at a lower significance level, while
upper limits are set on OVIII(Kb), NeX(Ka) and NeIX(Kb). The FUSE spectrum of
this source shows complex OVI(2s-->2p) absorption at the same redshift as the
X-ray system, made by at least two components: one relatively narrow and
slightly redshifted, and one broader and blueshifted (cz = -135 km/s). We
demonstrate that the physical states of the UV and X-ray absorbers are hard to
reconcile with a single, purely collisionally ionized, equilibrium plasma. We
propose, instead, that the X-ray and, at least the broader and blueshifted UV
absorber are produced in a low density intergalactic plasma (partly
photoionized by the diffuse extragalactic X-ray background), collapsing towards
our Galaxy, consistent with the predictions of a Warm-Hot Intergalactic Medium
(WHIM) from numerical simulations. We find that any reasonable solution
requires overabundance of Ne compared to O by a factor of ~2, with respect to
the solar value and propose several scenarios to account for this observation.


title:
X-ray sources in the starburst spiral galaxy M83: nuclear region and
  discrete source population

abstract:
  Chandra has resolved the starburst nuclear region of the face-on grand-design
spiral M83. Eighty-one point sources are detected above 3.5 sigma in the ACIS
S3 image, and 15 of them are within the inner 16-arcsec region of the galaxy. A
point source with L_x ~ 3 x 10^(38) erg/s in the 0.3--8.0 keV band is found to
coincide with the infra-red nuclear photometric peak, one of the two dynamical
nuclei of the galaxy. No point-like sources are resolved (at a 2.5-sigma level)
at the centre of symmetry of the outer optical isophote ellipses, suspected to
be another dynamical nucleus. About 50% of the total emission in the nuclear
region is unresolved; of this, about 70% can be attributed to hot thermal
plasma, and the rest is probably due to unresolved point sources (eg, faint
X-ray binaries). The azimuthally-averaged radial distribution of the unresolved
emission has a King-like profile, with no central cusp. Strong emission lines
are seen in the spectrum of the optically thin plasma component. The high
abundances of C, Ne, Mg, Si and S with respect to Fe suggest that the
interstellar medium in the nucleus is enriched and heated by type-II supernova
explosions and winds from massive stars. The cumulative luminosity distribution
of the discrete X-ray sources is neither a single nor a broken power law.
Separating the sources in the nuclear region (within a distance of 60 arcsec
from the X-ray centre) from the rest reveals that the two groups have different
luminosity distributions. The log[N(>S)]--log S curve of the sources in the
inner region (nucleus and stellar bar) is a single power law, which we
interpret as due to continuous, ongoing star formation. Outside the central
region, there is a smaller fraction of sources brighter than the Eddington
limit for an accreting neutron star.


title:
Do the Infrared Emission Features Need Ultraviolet Excitation? The PAH
  Model in UV-Poor Reflection Nebulae

abstract:
  One of the major challenges to identification of the 3.3, 6.2, 7.7, 8.6, and
11.3um interstellar IR emission bands with polycyclic aromatic hydrocarbon
(PAH) molecules has been the recent detection of these bands in regions with
little UV illumination, since small, neutral PAH molecules have little or no
absorption at visible wavelengths and therefore require UV photons for
excitation.
  We show here that our "astronomical" PAH model, incorporating the
experimental result that the visual absorption edge shifts to longer wavelength
upon ionization and/or as the PAH size increases, can closely reproduce the
observed infrared emission bands of vdB 133, a UV-poor reflection nebula.
  It is also shown that single-photon heating of ``astronomical'' PAHs in
reflection nebulae near stars as cool as T_eff=3000K can result in observable
emission at 6.2, 7.7, 8.6, and 11.3um. Illustrative mid-IR emission spectra are
also calculated for reflection nebulae illuminated by cool stars with
T_eff=3500, 4500, 5000K. These will allow comparison with future Space Infrared
Telescope Facility (SIRTF) observations of vdB 135 (T_eff=3600K), vdB 47
(T_eff=4500K), and vdB 101 (T_eff=5000K).
  It is also shown that the dependence of the 12um IRAS emission relative to
the total far-IR emission on the effective temperature of the exciting star is
consistent with the PAH model expectation for 3000K < T_eff < 30000K.


title:
Interstellar scintillation as the origin of rapid radio variability in
  the quasar J1819+3845

abstract:
  Quasars shine brightly due to the liberation of gravitational energy as
matter falls onto a supermassive black hole in the centre of a galaxy.
Variations in the radiation received from active galactic nuclei (AGN) are
studied at all wavelengths, revealing the tiny dimensions of the region and the
processes of fuelling the black hole. Some AGN are variable at optical and
shorter wavelengths, and display radio outbursts over years and decades. These
AGN often also show faster variations at radio wavelengths (intraday
variability, IDV) which have been the subject of much debate. The simplest
explanation, supported by a correlation in some sources between the optical
(intrinsic) and faster radio variations, is that the rapid radio variations are
intrinsic. However, this explanation implies physically difficult brightness
temperatures, suggesting that the variations may be due to scattering of the
incident radiation in the interstellar medium of our Galaxy. Here we present
results which show unambiguously that the variations in one extreme case are
due to interstellar scintillation. We also measure the transverse velocity of
the scattering material, revealing a surprising high velocity plasma close to
the Solar System.


title:
Bow Shocks from Neutron Stars: Scaling Laws and HST Observations of the
  Guitar Nebula

abstract:
  The interaction of high-velocity neutron stars with the interstellar medium
produces bow shock nebulae, where the relativistic neutron star wind is
confined by ram pressure. We present multi-wavelength observations of the
Guitar Nebula, including narrow-band H-alpha imaging with HST/WFPC2, which
resolves the head of the bow shock. The HST observations are used to fit for
the inclination of the pulsar velocity vector to the line of sight, and to
determine the combination of spindown energy loss, velocity, and ambient
density that sets the scale of the bow shock. We find that the velocity vector
is most likely in the plane of the sky. We use the Guitar Nebula and other
observed neutron star bow shocks to test scaling laws for their size and
H-alpha emission, discuss their prevalence, and present criteria for their
detectability in targeted searches. The set of H-alpha bow shocks shows
remarkable consistency, in spite of the expected variation in ambient densities
and orientations. Together, they support the assumption that a pulsar's
spindown energy losses are carried away by a relativistic wind that is
indistinguishable from being isotropic. Comparison of H-alpha bow shocks with
X-ray and nonthermal, radio-synchrotron bow shocks produced by neutron stars
indicates that the overall shape and scaling is consistent with the same
physics. It also appears that nonthermal radio emission and H-alpha emission
are mutually exclusive in the known objects and perhaps in all objects.


title: The X-ray Spectra of VY Scl Stars Are Not Blackbodies

abstract:
  Using ASCA data, we find, contrary to other researchers using ROSAT data,
that the X-ray spectra of the VY Scl stars TT Ari and KR Aur are poorly fit by
an absorbed blackbody model but are well fit by an absorbed thermal plasma
model. The different conclusions about the nature of the X-ray spectrum of KR
Aur may be due to differences in the accretion rate, since this star was in a
high optical state during the ROSAT observation, but in an intermediate optical
state during the ASCA observation. TT Ari, on the other hand, was in a high
optical state during both observations, so directly contradicts the hypothesis
that the X-ray spectra of VY Scl stars in their high optical states are
blackbodies. Instead, based on theoretical expectations and the ASCA, Chandra,
and XMM spectra of other nonmagnetic cataclysmic variables, we believe that the
X-ray spectra of VY Scl stars in their low and high optical states are due to
hot thermal plasma in the boundary layer between the accretion disk and the
surface of the white dwarf, and appeal to the acquisition of Chandra and XMM
grating spectra to test this prediction.


title:
Stellar Velocity Dispersion and Black Hole Mass in the Blazar Markarian
  501

abstract:
  The recently discovered correlation between black hole mass and stellar
velocity dispersion provides a new method to determine the masses of black
holes in active galaxies. We have obtained optical spectra of Markarian 501, a
nearby gamma-ray blazar with emission extending to TeV energies. The stellar
velocity dispersion of the host galaxy, measured from the calcium triplet lines
in a 2"x3.7" aperture, is 372 +/- 18 km/s. If Mrk 501 follows the M-sigma
correlation defined for local galaxies, then its central black hole has a mass
of (0.9-3.4)x10^9 solar masses. This is significantly larger than some previous
estimates for the central mass in Mrk 501 that have been based on models for
its nonthermal emission. The host galaxy luminosity implies a black hole of
6x10^8 solar masses, but this is not in severe conflict with the mass derived
from the M-sigma relation because the M_BH-L_bulge correlation has a large
intrinsic scatter. Using the emission-line luminosity to estimate the
bolometric luminosity of the central engine, we find that Mrk 501 radiates at
an extremely sub-Eddington level of L/L_Edd ~ 10^-4. Further applications of
the M-sigma relation to radio-loud active galactic nuclei may be useful for
interpreting unified models and understanding the relationship between radio
galaxies and BL Lac objects.


title: Low-Luminosity AGNs and Unification

abstract:
  More than one third of all nearby galaxies show indications of low-luminosity
nuclear activity. These low-luminosity AGNs (LLAGNs) are traditionally
classified into a variety of categories depending on their forbidden-line
ratios and on the presence or absence of broad-line emission. By analogy with
Seyfert unification models, it is natural to ask whether the various LLAGN
types are different manifestations of the same underlying phenomenon, with
observed differences being solely due to orientation and obscuration, or
whether there are fundamentally distinct physical processes at work in
different categories of LLAGNs. This contribution reviews some recent
observations of LLAGNs in the context of AGN unification scenarios.


title:
The Formation of the First Globular Clusters in Dwarf Galaxies Before
  the Epoch of Reionization

abstract:
  We explore a mechanism for the formation of the first globular clusters,
operating during the assembly of dwarf galaxies at high redshifts, z > 10. The
substructure in the dark matter and the corresponding potential wells are
responsible for setting the cluster scale of ~10^5 M_sun. The second mass scale
in the formation problem, the stellar scale of ~1 M_sun, is determined in turn
by the processes that cool the gas. We address the origin of the first, cluster
scale by means of three-dimensional numerical simulations of the collapsing
dark matter and gaseous components. We find that the gas falls into the deepest
dark subhalos, resulting in a system of ~ 5 proto-globular clouds. The
incipient globular clusters lose their individual dark halos in the process of
violent relaxation, leading to the build-up of the general dark halo around the
dwarf galaxy.


title: Spectrophotometry and structural analysis of 5 comets

abstract:
  We discuss the morphology and spectrophotometry of 5 comets visible in
August, 2001. We decompose comae into coma profiles and azimuthally
renormalized images, in which general and local features are quantitatively
comparable. Comet 19P/Borrelly showed a strong gas fan toward the solar
direction, but no detectable gas in the tail. Dust in its inner coma was
collimated toward the antisolar direction and the tail, with no dust in the
outer coma. The contribution of spatial variations structure was moderate,
about 35%. Comet 29P Schwassmann-Wachmann 1 was observed in outburst: we
detected ``spinning'' jet structures. A high level of dust production resulted
in an unusually high Af\rho=16600 cm. The spatial variations reached -77%, at
the minimum, due in part to a jet and a ring-like structure in 1 arcminute
distance from the nucleus. In comet C/2001 A2, we detected a strong
post-perihelion increase of dust and gas activity, in which the C_2 profile
became one magnitude brighter over a 3-day period. For comets C/2000 SV74 and
C/2000 WM1, we present detailed pre-perihelion spectrophotometry and
morphological information. Comet C/2000 SV74 showed high dust production
(Af\rho=1479 cm). Its coma suggests a steady-state outflow of material, while
the low contribution of spatial variations support high level activity. The
coma of C/2000 WM1 is dominated by solar effects, and CO+ forms the bulk of its
gas activity. Despite its large heliocentric distance, we observed a nice tail.


title:
Do Young Neutron Stars Which Show Themselves As AXPs, SGRs and Radio
  Pulsars Accrete?

abstract:
  We examined the fall-back disk models, and in general accretion, proposed to
explain the properties of anomalous X-ray pulsars (AXPs), soft gamma repeaters
(SGRs), and radio pulsars (PSRs). We checked the possibility of some gas
remaining around the neutron star after the supernova explosion. We also
compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude
the existing models of accretion from a fall-back disk are insufficient to
explain the nature of AXPs/SGRs, particularly the SGR bursts. We also discussed
the proposed model of combination of magnetic dipole radiation and propeller
torques in order to explain the evolution of radio pulsars on the P-\.{P}
diagram. The predictions of this model contradict the observational data.


title:
The ROSAT All-Sky Survey: a Catalog of Clusters of Galaxies in a Region
  of 1 Ster around the South Galactic Pole

abstract:
  A field of 1.013 ster in the ROSAT all-sky survey (RASS), centered on the
south galactic pole (SGP), has been searched in a systematic, objective manner
for clusters of galaxies. The procedure relied on a correlation of the X-ray
positions and properties of ROSAT sources with the distribution of galaxies in
the COSMOS digitised data base, which was obtained by scanning the plates of
the UK Schmidt IIIa-J optical southern sky survey. The study used the second
ROSAT survey data base (RASS-2) and included several optical observing
campaigns to measure redshifts. The search, a precursor to the larger REFLEX
survey of the whole southern sky, reached the detection limits of the RASS and
the COSMOS data, and yielded a catalog of 186 clusters in which the lowest flux
is 1.5e-12 erg/cm2/s in the 0.1-2.4 keV band. Of these 157 have measured
redshifts. Using a limit of 3.0e-12 erg/cm2/s a complete subset of 112 clusters
was obtained, of which 110 have measured redshifts. The spatial distribution of
the X-ray clusters out to z = 0.15 shows an extension of the Local Supercluster
to the Pisces-Cetus supercluster (z<~0.07), and a more distant orthogonal
structure at 0.07<z<0.15.


title: On the Nature of the X-ray Emission from the Galactic Center Region

abstract:
  The origin of the X-ray emission from the central region of the Galaxy has
remained a mystery, despite extensive study over the past two decades. A
fundamental question is the relative contribution of the point-source and
diffuse components of this emission, which is critical to understanding the
high-energy phenomena and processes unique to this Galactic nuclear
environment. Here, we report on results from a large-scale imaging survey of
the Galactic center with sufficient spatial resolution to allow a clean
separation of the two components. The highly-ionized Fe emission, previously
attributed to the diffuse emission, is found largely due to the discrete X-ray
source population. The number and spectrum of such sources indicate the
presence of numerous accreting white dwarfs, neutron stars, and/or black holes
in the region. The diffuse X-ray emission dominates over the contribution from
the faint discrete sources and is shown to be associated with distinct
interstellar structures observed at radio and mid-infrared wavelengths,
suggesting that it arises from the recent formation of massive stars. We have
also mapped out the 6.4-keV fluorescence line emission from neutral to
moderately ionized irons. The ubiquitous association of the emission with
molecular gas indicates that either the X-ray radiation from the Galactic
center was substantially more intense in the past than at present or
non-relativistic cosmic-rays are important in producing Fe K shell vacancies.


title: Chandra Imaging of the Gamma-Ray Source GeV J1809-2327

abstract:
  We report on Chandra imaging observations of the Galactic Unidentified
$\gamma$-ray source GEV J1809-2327, comparing the X-ray images with new VLA
1.46 GHz and 4.86 GHz maps. The X-ray images reveal a point source connected to
a non-thermal X-ray/radio nebula, supporting a pulsar/wind model for the
$\gamma$-ray emitter. We also detect numerous X-ray sources from the young
stellar association in the adjacent HII region S32.


title: Numerical Models of the ISM

abstract:
  I review recent results from numerical simulations on the structure and
dynamics of the ISM, and attempt to put together a coherent dynamical scenario.
In particular, I discuss results on 1) the spatial distribution of the gas
components, showing that reasonable agreement between simulations and
observations exists, but noting that in most models the components are simply
defined as temperature intervals, because distinct thermodynamic ``phases'' do
not arise; 2) some statistical issues of the physical fields, like the
dependence of the one-point statistics of the density field on the effective
equation of state of the gas, the poor correlation of magnetic strength with
density, the energy spectrum in weakly and highly compressible cases, and the
one point statistics of the velocity field; 3) the effects of spectroscopic
observation on distorting the physical structures and results from synthetic
observations of the simulations, and 4) several dynamical and thermodynamical
issues, such as the role of the thermal instability in forming and confining
clouds, the continuous, rather than abrupt, transition between ``phases'',
which in turn may be consequences of the dynamics rather than the agents
controlling it, the possibility of short time scales ($\sim $ a few Myr) for
molecular cloud formation, and the star-gas connection, mentioning that the
models generally exhibit self-propagating star and cluster formation, while the
stars may drive the medium- and small-scale gas motions, and that a ``star
formation instability'' may induce chaotic behavior of the star formation rate
locally. I conclude with a round-up view, and a discussion of the work needed
ahead.


title:
Relation of SiO maser emission to IR radiation in evolved stars based on
  the MSX observation

abstract:
  Based on the space MSX observation in bands A(8$\mu$m), C(12$\mu$m),
D(15$\mu$m) and E(21$\mu$m), and the ground SiO maser observation of evolved
stars by the Nobeyama 45-m telescope in the v=1 and v=2 J=1-0 transitions, the
relation between SiO maser emission and mid-IR continuum radiation is analyzed.
The relation between SiO maser emission and the IR radiation in the MSX bands
A, C, D and E is all clearly correlated. The SiO maser emission can be
explained by a radiative pumping mechanism according to its correlation with
infrared radiation in the MSX band A.


title:
A formula for the number of days between the winter solstice and the
  latest sunrise

abstract:
  A simple closed-form expression for the number of days between the winter
solstice and the latest sunrise is derived. Formulas for the summer solstice
and the sunset are derived as well. These approximate formulas make it easy to
see the functional dependence on the latitude of the observer. An approximate
expression for the difference in time of day between the latest sunrise and the
sunrise on the solstice is also derived. The formulas are not valid in the
Arctic, Antarctic or tropics.


title: How much will we learn from the CMB ?

abstract:
  The purpose of this article is to give a brief account of what we hope to
learn from the future CMB experiments, essentially from the point of view of
primordial cosmology. After recalling what we have already learnt, the
principles of parameter extraction from the data are summarized. The discussion
is then devoted to the information we could gain about the early universe, in
the framework of the inflationary scenario, or in more exotic scenarios like
brane cosmology.


title:
Scaling Relation to Understand Non-Detection of Cold Gas at the Cluster
  Center

abstract:
  Recent XMM-Newton observations of clusters of galaxies have indicated the
soft X-ray spectra to be inconsistent with the simple isobaric cooling flow
model. There is almost no feature of the cold gas expected from the model. This
shows that we have not yet understood the physics of the hot gas in clusters of
galaxies well. A quantitative evaluation of the behavior of gas cooling is
important not only for understanding the clusters, themselves, but also for
studying cosmology and galaxy formation. To clarify the problem of this
reported discrepancy, we have studied scaling relations for clusters of
galaxies based on the self-similarity assumption. We also propose an
observational strategy to solve this problem.


title:
Observations of SiO Maser Sources within a Few Parsec from the Galactic
  Center

abstract:
  Mapping and monitoring observations of SiO maser sources near the Galactic
center were made with the Nobeyama 45-m telescope at 43 GHz. Rectangular
mapping an area of approximately 200'' x 100''$ in a 30'' grid, and triangular
mapping in a 20'' grid toward the Galactic center, resulted in 15 detections of
SiO sources; the positions of the sources were obtained with errors of 5--10'',
except for a few weak sources. Three-year monitoring observations found that
the component at V_lsr=-27 km/s of IRS 10 EE flared to about 1.5 Jy during 2000
March--May, which was a factor of more than 5 brighter than its normal
intensity. Using the radial velocities and positions of the SiO sources, we
identified 5 which are counterparts of previously observed OH 1612 MHz sources.
The other 10 SiO sources have no OH counterparts, but two were previously
detected with VLA, and four are located close to the positions of
large-amplitude variables observed at near-infrared wavelengths. A
least-squares fit to a plot of velocities versus Galactic longitudes gives a
rather high speed for the rotation of the star cluster around the Galactic
center. The observed radial-velocity dispersion is roughly consistent with a
value obtained before. It was found that all of the SiO sources with OH 1612
MHz counterparts have periods of light variation longer than 450 days, while
SiO sources without OH masers often have periods shorter than 450 days. This
fact suggests that lower-mass AGB stars are more often detected in SiO masers
than in the OH 1612 MHz line.


title: Confidence Limits of Evolutionary Synthesis Models

abstract:
  The probabilistic nature of the IMF in stellar systems implies that clusters
of the same mass and age do not present the same unique values of their
observed parameters. Instead they follow a distribution. We address the study
of such distributions in terms of their confidence limits that can be obtained
by evolutionary synthesis models. These confidence limits can be understood as
the inherent uncertainties of synthesis models. We will compare such confidence
limits arising from the discreteness of the number of stars obtained with Monte
Carlo simulations with the dispersion resulting from an analytical formalism.
We give some examples of the effects on the kinetic energy, V--K, EW(H$\beta$)
and multiwavelength continuum.


title: Radio observations of the circumnuclear ring in NGC6951

abstract:
  We present sensitive, high-resolution radio observations of the circumnuclear
region of the barred spiral galaxy NGC6951. These observations reveal a ring of
radio emission with many discrete components and a marginally resolved nuclear
component. We compare the radio ring with observations at other wavelengths,
and discuss the nature of the compact radio components.


title: X-ray Spectra and Pulse Frequency Changes in SAX J2103.5+4545

abstract:
  The November 1999 outburst of the transient pulsar SAX J2103.5+4545 was
monitored with the large area detectors of the Rossi X-Ray Timing Explorer
until the pulsar faded after a year. The 358 s pulsar was spun up for 150 days,
at which point the flux dropped quickly by a factor of 7, the frequency
saturated and, as the flux continued to decline, a weak spin-down began. The
pulses remained strong during the decay and the spin-up/flux correlation can be
fit to the Ghosh and Lamb derivations for the spin-up caused by accretion from
a thin, pressure-dominated disk, for a distance 3.2 kpc and a surface magnetic
field 1.2 10^{13} Gauss. During the bright spin-up part of the outburst, the
flux was subject to strong orbital modulation, peaking 3 days after periastron
of the eccentric 12.68 day orbit, while during the faint part, there was little
orbital modulation. The X-ray spectra were typical of accreting pulsars,
describable by a cut-off power-law, with an emission line near the 6.4 keV of K
alpha fluorescence from cool iron. The equivalent width of this emission did
not share the orbital modulation, but nearly doubled during the faint phase,
despite little change in the column density. The outburst could have been
caused by an episode of increased wind from a Be star, such that a small
accretion disk is formed during each periastron passage. A change in the wind
and disk structure apparently occurred after 5 months such that the accretion
rate was no longer modulated or the diffusion time was longer. The distance
estimate implies the X-ray luminosity observed was between 1 10^{36} ergs
s^{-1} and 6 \times 10^{34} ergs s^{-1}, with a small but definite correlation
of the intrinsic power-law spectral index.


title: The black hole - bulge mass relation in active and inactive galaxies

abstract:
  New virial black-hole mass estimates are presented for a sample of 72 AGN
covering three decades in optical luminosity. Using a model in which the AGN
broad-line region (BLR) has a flattened geometry, we investigate the
M_{bh)-L_{bulge} relation for a combined 90-object sample, consisting of the
AGN plus a sample of 18 nearby inactive elliptical galaxies with dynamical
black-hole mass measurements. It is found that, for all reasonable
mass-to-light ratios, the M_{bh}-L_{bulge} relation is equivalent to a linear
scaling between bulge and black-hole mass. The best-fitting normalization of
the M_{bh}-M_{bulge} relation is found to be M_{bh}=0.0012M_{bulge}, in
agreement with recent black-hole mass studies based on stellar velocity
dispersions. Furthermore, the scatter around the M_{bh}-L_{bulge} relation for
the full sample is found to be significantly smaller than has been previously
reported (\Delta \log M_{bh}=0.39 dex). Finally, using the nearby inactive
elliptical galaxy sample alone, it is shown that the scatter in the
M_{bh}-L_{bulge} relation is only 0.33 dex, comparable to that of the
M_{bh}-sigma relation. These results indicate that reliable black-hole mass
estimates can be obtained for high redshift galaxies.


title: Physical Properties of Trans-Neptunian Object (20000) Varuna

abstract:
  We present new time-resolved photometric observations of the bright
trans-Neptunian object (20000) Varuna and use them to study the rotation
period, shape, and color. In observations from 2001 February and April, we find
a best-fit two-peaked lightcurve with period 6.3442 +-0.0002 hr. The
peak-to-peak photometric range in the R-band is 0.42 +-0.02 mag. We find no
rotational variation in colors over the 0.45 < lambda < 0.85 micron wavelength
range. From the short double-peaked period and large amplitude we suggest that
Varuna is an elongated, prolate body perhaps close in shape to one of the
Jacobi ellipsoids. If so, the ratio of the axes projected into the plane of the
sky is 1.5:1 and the density is near 1000 kg m^(-3). (20000) Varuna may be a
rotationally distorted rubble pile, with a weak internal constitution due to
fracturing by past impacts. The high specific angular momentum implied by our
observations and recent detections of binary Trans-Neptunian Objects both point
to an early, intense collisional epoch in which large Trans-Neptunian Objects
were about 100 times more abundant than now. In order to maintain a
cosmochemically plausible rock:ice mass ratio of about 0.5, Varuna must be
internally porous.


title:
Magnetic fields and radio polarization of barred galaxies - 3D dynamo
  simulations

abstract:
  A three-dimensional (3D) MHD model is applied to simulate the evolution of a
large-scale magnetic field in a barred galaxy possessing a gaseous halo
extending to about 2.8 kpc above the galactic plane. As the model input we use
a time-dependent velocity field of molecular gas resulting from self-consistent
3D N-body simulations of a galactic disk. We assume that the gaseous halo
rotates differentially co-rotating with the disk or decreasing its velocity in
the Z direction. The dynamo process included in the model yields the
amplification of the magnetic field as well as the formation of field
structures high above the galactic disk. The simulated magnetic fields are used
to construct the models of a high-frequency (Faraday rotation-free) polarized
radio emission that accounts for effects of projection and limited resolution,
and is thus suitable for direct comparison with observations. We found that the
resultant magnetic field correctly reproduces the observed structures of
polarization B-vectors, forming coherent patterns well aligned with spiral arms
and with the bar. The process initializing a wave-like behavior of the magnetic
field, which efficiently forms magnetic maxima between the spiral arms, is
demonstrated. The inclusion of the galactic halo constitutes a step towards a
realistic model of galactic magnetic fields that includes as many dynamical
components as needed for a realistic description.


title: The time variation in infrared water-vapour bands in Mira variables

abstract:
  The time variation in the water-vapour bands in oxygen-rich Mira variables
has been investigated using multi-epoch ISO/SWS spectra of four Mira variables
in the 2.5-4.0 micron region. All four stars show H2O bands in absorption
around minimum in the visual light curve. At maximum, H2O emission features
appear in the ~3.5-4.0 micronm region, while the features at shorter
wavelengths remain in absorption. These H2O bands in the 2.5-4.0 micron region
originate from the extended atmosphere.
  The analysis has been carried out with a disk shape, slab geometry model. The
observed H2O bands are reproduced by two layers; a `hot' layer with an
excitation temperature of 2000 K and a `cool' layer with an excitation
temperature of 1000-1400 K. The radii of the `hot' layer (R_hot) are ~1 R_* at
visual minimum and 2 R_* at maximum, where R_* is a radius of background source
of the model. The time variation of R_hot/R_* from 1 to 2 is attributed to the
actual variation in the radius of the H2O layer. A high H2O density shell
occurs near the surface of the star around minimum, and moves out with the
stellar pulsation. This shell gradually fades away after maximum, and a new
high H2O density shell is formed in the inner region again at the next minimum.
Due to large optical depth of H2O, the near-infrared variability is dominated
by the H2O layer, and the L'-band flux correlates with the area of the H2O
shell. The infrared molecular bands trace the structure of the extended
atmosphere and impose appreciable effects on near-infrared light curve of Mira
variables.


title: On Core Collapse Supernovae in Normal and in Seyfert Galaxies

abstract:
  This paper estimates the relative frequency of different types of
core-collapse supernovae, in terms of the ratio f between the number of type
Ib--Ic and of type II supernovae. We estimate f independently for all normal
and Seyfert galaxies whose radial velocity is <=14000 km/s, and which had at
least one supernova event recorded in the Asiago catalogue from January 1986 to
August 2000. We find that the ratio f is approx. 0.23+/-0.05 in normal
galaxies. This value is consistent with constant star formation rate and with a
Salpeter Initial Mass Function and average binary rate approx. 50 %. On the
contrary, Seyfert galaxies exceed the ratio f in normal galaxies by a factor
approx. 4 at a confidence level >= 2 sigma. A caveat is that the numbers for
Seyferts are still small (6 type Ib-Ic and 6 type II supernovae discovered as
yet). Assumed real, this excess of type Ib and Ic with respect to type II
supernovae, may indicate a burst of star formation of young age (<= 20 Myr), a
high incidence of binary systems in the inner regions (r <= 0.4 R25) of Seyfert
galaxies, or a top-loaded mass function.


title:
A SAURON study of M32: measuring the intrinsic flattening and the
  central black hole mass

abstract:
  We present dynamical models of the nearby compact elliptical galaxy M32,
using high quality kinematical measurements, obtained with the integral-field
spectrograph SAURON mounted on the William Herschel Telescope on La Palma. We
also include STIS data obtained by Joseph et al. We find a best-fit black hole
mass of (2.5 +/- 0.5) million solar masses and a stellar I-band mass-to-light
ratio of (1.85 +/- 0.15) in solar units. For the first time, we are also able
to constrain the inclination along which M32 is observed to (70 +/- 5) degrees.
Combined with an averaged observed flattening of 0.73, this corresponds to an
intrinsic flattening of approximately 0.68 +/- 0.03.
  These tight constraints are mainly caused by the use of integral-field data.
We show this quantitatively by comparing with models that are constrained by
multiple slits only. We show the phase-space distribution and intrinsic
velocity structure of the best-fit model and investigate the effect of
regularisation on the orbit distribution.


title:
MERLIN radio detection of an interaction zone within a binary Orion
  proplyd system

abstract:
  Presented here are high angular resolution MERLIN 5 GHz (6 cm) continuum
observations of the binary proplyd system, LV 1 in the Orion nebula, which
consists of proplyd 168--326SE and its binary proplyd companion 168--326NW
(separation 0.4 arcsec). Accurate astrometric alignment allows a detailed
comparison between these data and published HST PC Halpha and [Oiii] images.
  Thermal radio sources coincide with the two proplyds and originate in the
ionized photoevaporating flows seen in the optical emission lines. Flow
velocities of approx 50 km/s from the ionized proplyd surfaces and \geq 100
km/s from a possible micro-jet have been detected using the Manchester Echelle
spectrometer.
  A third radio source is found to coincide with a region of extended, high
excitation, optical line emission that lies between the binary proplyds
168--326SE/326NW . This is modelled as a bowshock due to the collision of the
photoevaporating flows from the two proplyds. Both a thermal and a non-thermal
origin for the radio emission in this collision zone are considered.


title:
Pulsations and orbital modulation of the intermediate polar 1WGA
  J1958.2+3232

abstract:
  We present optical photometry, spectroscopy and photopolarimetry, as well as
ASCA X-ray observations, of the recently discovered intermediate polar 1WGA
J1958.2+3232. Through the first detection of an optical beat frequency, we
confirm the previously tentative suggestion that the spin period of the white
dwarf is twice the X-ray and optical pulsation period, which we also confirm in
each case. We detect an orbital modulation in each of the U, B, V, R and I
bands for the first time, and suggest that the true orbital period is the -1d
alias of that previously suggested. We also confirm the presence of circular
polarization in this system, detecting a variable polarization which has
opposite signs in each of the B and R bands. The double peaked pulse profile
and oppositely signed polarization pulses suggest that 1WGA J1958.2+3232
accretes onto both magnetic poles via a disc which is truncated relatively
close to the white dwarf.


title: An AGN Hertzsprung-Russell Diagram

abstract:
  Detailed examination of the balance between star-formation and nuclear
activity in AGN and starburst galaxies leads to the composition of an
Hertzsprung-Russell diagram in which possible evolutionary tracks can be drawn.
It is likely that these tracks also relate to the level of obscuration.


title: Chemical Evolution Models of Local dSph Galaxies

abstract:
  We calculate chemical evolution models for 4 dwarf spheroidal satellites of
the Milky Way (Carina, Ursa Minor, Leo I and Leo II) for which reliable
non-parametric star formation histories have been derived. In this way, the
independently obtained star formation histories are used to constrain the
evolution of the systems we are treating. This allows us to obtain robust
inferences on the history of such crucial parameters of galactic evolution as
gas infall, gas outflows and global metallicities for these systems. We can
then trace the metallicity and abundance ratios of the stars formed, the gas
present at any time within the systems and the details of gas ejection, of
relevance to enrichment of the galaxies environment. We find that galaxies
showing one single burst of star formation (Ursa Minor and Leo II) require a
dark halo slightly larger that the current estimates for their tidal radii, or
the presence of a metal rich selective wind, which might carry away much of the
energy output of their supernovae before this might have interacted and heated
the gas content, for the gas to be retained until the observed stellar
population have formed. Systems showing extended star formation histories
(Carina and Leo I) however, are consistent with the idea that their tidally
limited dark haloes provide the necessary gravitational potential wells to
retain their gas. The complex time structure of the star formation in these
systems, remains difficult to understand. Observations of detailed abundance
ratios for Ursa Minor, strongly suggest that the star formation history of this
galaxy might in fact resemble the complex picture presented by Carina or Leo I,
but localized at a very early epoch.


title:
ATCA radio imaging of the ProPlyD-like objects in the giant HII region
  NGC 3603

abstract:
  Three cometary-shaped objects in the giant HII region NGC 3603, originally
found and identified as proto-planetary disks (ProPlyDs) by Brandner et al.
2000 using HST+VLT in the optical and near-infrared, have been detected with
the Australia Telescope Compact Array (ATCA) in the radio continuum at 3 and
6cm. All three ProPlyD-like objects are clearly resolved with an extent of a
few arcseconds. The integrated 6cm fluxes are up to 1.3 times higher than the
3cm fluxes with spectral indices averaged over the whole clump between
$\alpha=-0.1$ and -0.5 ($S_\nu \propto \nu^{\alpha}$), indicating the likely
presence of non-thermal emission in at least some of the sources. All measured
fluxes are at least one order of magnitude higher than those predicted by
Brandner et al. 2000. Due to the unexpectedly large radio luminosities of the
ProPlyD-like features and because the radio emission is extended a
(proto-)stellar origin of the non-thermal emission from a dust enshrouded star
appears unlikely. Instead we propose that magnetized regions within the
envelope of the ProPlyD-like nebulae exist. (abridged)


title:
Observational Constraints on the Topology (Global Geometry) of the
  Universe

abstract:
  The Universe is a physical object. Physical objects have shapes and sizes.
General relativity is insufficient to describe the global shape and size of the
Universe: the Hilbert-Einstein equations only treat limiting quantities towards
an arbitrary point. Empirical work on measuring the shape and size of the
Universe (formally: the ``3-manifold of the spatial hypersurface at constant
cosmological time'', and, e.g. the ``injectivity diameter'' respectively) has
progressed significantly in the late 1980's and the 1990's, using observational
catalogues of galaxy clusters, of quasars and of the microwave background,
though the analyses are still hindered by simplifying (and often
observationally unsupported) assumptions. A review of the different
observational strategies and claimed constraints was presented at the meeting.


title: Mid-infrared observations of the SGR 1900+14 error box

abstract:
  We report on mid-infrared observations of the compact stellar cluster located
in the proximity of SGR 1900+14, and the radio/X-ray position of this
soft-gamma repeater. Observations were performed in May and June of 2001 when
the bursting source was in an active state. At the known radio and X-ray
position of the SGR we did not detect transient mid-IR activity, although the
observations were performed only hours before and after an outburst in the
high-energy band.


title: How is the Reionization Epoch Defined?

abstract:
  We study the effect of a prolonged epoch of reionization on the angular power
spectrum of the Cosmic Microwave Background. Typically reionization studies
assume a sudden phase transition, with the intergalactic gas moving from a
fully neutral to a fully ionized state at a fixed redshift. Such models are at
odds, however, with detailed investigations of reionization, which favor a more
extended transition. We have modified the code CMBFAST to allow the treatment
of more realistic reionization histories and applied it to data obtained from
numerical simulations of reionization. We show that the prompt reionization
assumed by CMBFAST in its original form heavily contaminates any constraint
derived on the reionization redshift. We find, however, that prompt
reionization models give a reasonable estimate of the epoch at which the mean
cosmic ionization fraction was ~50%, and provide a very good measure of the
overall Thomson optical depth. The overall differences in the temperature
(polarization) angular power spectra between prompt and extended models with
equal optical depths are less than 1% (10%).


title:
The Angular Momentum of Gas in Proto-Galaxies I. Implications for the
  Formation of Disk Galaxies

abstract:
  We use non-radiative N-body/SPH simulations of structure formation in a LCDM
cosmology to compare the angular momentum distributions of dark matter and gas
in a large sample of halos. We show that the two components have identical spin
parameter distributions and that their angular momentum distributions within
individual halos are very similar, all in excellent agreement with standard
assumptions. Despite these similarities, however, we find that the angular
momentum vectors of the gas and dark matter are poorly aligned, with a median
misalignment angle of about 30 degrees, which might have important implications
for spin correlation statistics used in weak lensing studies. We present
distributions for the component of the angular momentum that is aligned with
the total angular momentum of each halo, and find that for between 5 and 50
percent of the mass this component is negative. This disagrees with the
`Universal' angular momentum distribution suggested by Bullock et al. (2001),
for which the mass fraction with negative specific angular momentum is zero. We
discuss the implications of our results for the formation of disk galaxies.
Since galactic disks generally do not contain counter-rotating stars or gas,
disk formation cannot occur under detailed conservation of specific angular
momentum. We suggest that the material with negative specific angular momentum
combines with positive angular momentum material to build a bulge component,
and show that in such a scenario the remaining material can form a disk with a
density distribution that is very close to exponential.


title: Resolving subdwarf B stars in binaries by HST imaging

abstract:
  The origin of subluminous B stars is still an unsolved problem in stellar
evolution. Single star as well as close binary evolution scenarios have been
invoked but until now have met with little success. We have carried out a small
survey of spectroscopic binary candidates (19 systems consisting of an sdB star
and late type companion) with the Planetary Camera of the WFPC2 onboard Hubble
Space Telescope to test these scenarios. Monte Carlo simulations indicate that
by imaging the programme stars in the R-band about one third of the sample (6-7
stars) should be resolved at a limiting angular resolution of 0.1" if they have
linear separations like main sequence stars ("single star evolution"). None
should be resolvable if all systems were produced by close binary evolution. In
addition we expect three triple systems to be present in our sample. Most of
these, if not all, should be resolvable. Components were resolved in 6 systems
with separations between 0.2" and 4.5". However, only in two systems do the
magnitudes of the resolved components match the expectations from the
deconvolution of the spectral energy distribution. These two stars could be
physical binaries whereas in the other cases the nearby star may be a chance
projection or a third component. Radial velocity measurements indicate that the
resolved system TON 139 is a triple system, with the sdB having a close
companion that does not contribute detectably to the integrated light of the
system. Accordingly the success rate would be only 5% which is clearly below
the prediction for single star evolution. We conclude that the distribution of
separations of sdB binaries deviates strongly from that of normal stars. Our
results add further evidence that close binary evolution is fundamental for the
evolution of sdB stars. (abbreviated)


title: Search for Supersymmetric Dark Matter with Superfluid He3 (MACHe3)

abstract:
  MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter search, using superfluid He3 as a sensitive medium. This
paper presents a phenomenological study done with the DarkSUSY code, in order
to investigate the discovery potential of this project of detector, as well as
its complementarity with existing and planned devices.


title:
The Initial Mass Function of Stars: Evidence for Uniformity in Variable
  Systems

abstract:
  The distribution of stellar masses that form in one star-formation event in a
given volume of space is called the initial mass function (IMF). The IMF has
been estimated from low-mass brown dwarfs to very massive stars. Combining IMF
estimates for different populations in which the stars can be observed
individually unveils an extraordinary uniformity of the IMF. This general
insight appears to hold for populations including present-day star formation in
small molecular clouds, rich and dense massive star-clusters forming in giant
clouds, through to ancient and metal-poor exotic stellar populations that may
be dominated by dark matter. This apparent universality of the IMF is a
challenge for star formation theory because elementary considerations suggest
that the IMF ought to systematically vary with star-forming conditions.


title: High Density Neutron Star Equation of State from 4U 1636-53 Observations

abstract:
  A bound on the compactness of the neutron star in the low mass x-ray binary
4U 1636-53 is used to estimate the equation of state of neutron star matter at
high density. Observations of 580 Hz oscillations during the rising phase of
x-ray bursts from this system appear to be due to two antipodal hot spots on
the surface of an accreting neutron star rotating at 290 Hz, implying the
compactness of the neutron star is less than 0.163 at the 90% confidence level.
The equation of state of high density neutron star matter estimated from this
compactness limit is significantly stiffer than extrapolations to high density
of equations of state determined by fits of experimental nucleon-nucleon
scattering data and properties of light nuclei to two- and three-body
interaction potentials.


title:
Effects of Relativistic Expansion on the Late-time Supernova Light
  Curves

abstract:
  The effects of relativistic expansion on the late-time supernova light curves
are investigated analytically, and a correction term to the (quasi-)exponential
decay is obtained by expanding the observed flux in terms of (\beta), where
(\beta) is the maximum velocity of the ejecta divided by the speed of light
(c). It is shown that the Doppler effect brightens the light curve owing to the
delayed decay of radioactive nuclei as well as to the Lorentz boosting of the
photon energies. The leading correction term is quadratic in (\beta), thus
being proportional to (E_{\rm k}/(M_{\rm ej} c^2)), where (E_{\rm k}) and
(M_{\rm ej}) are the kinetic energy of explosion and the ejecta mass. It is
also shown that the correction term evolves as a quadratic function of time
since the explosion. The relativistic effect is negligibly small at early
phases, but becomes of considerable size at late phases. In particular, for
supernove having a very large energy(hypernova) or exploding in a jet-like or
whatever non-spherical geometry, (^{56})Ni is likely to be boosted to higher
velocities and then we might see an appreciable change in flux. However, the
actual size of deviation from the (quasi-)exponential decay will be uncertain,
depending on other possible effects such as ionization freeze-out and
contributions from other energy sources that power the light curve.


title:
Metal abundances and kinematics of quasar absorbers.- I. Absorption
  systems toward J2233-606

abstract:
  The metal line profiles of different ions observed in high HI column density
systems [N(HI) > 10^{16} cm^{-2}] in quasar spectra can be used to constrain
the ionization structure and kinematic characteristics of the absorbers. For
these purposes, a modified Monte Carlo Inversion (MCI) procedure was applied to
the study of three absorption systems in the spectrum of the HDF-South quasar
J2233-606 obtained with the UVES spectrograph at the VLT/Kueyen telescope. The
MCI does not confirm variations of metal abundances within separate systems
which were discussed in the literature. Instead, we found that an assumption of
a homogeneous metal content and a unique photoionizing background is sufficient
to describe the observed complex metal profiles. It was also found that the
linear size L and the line-of-sight velocity dispersion sigma_v measured within
the absorbers obey a scaling relation, namely, sigma_v increases with
increasing L, and that metal abundance is inversely proportional to the linear
size of the system: the highest metallicity was measured in the system with the
smallest L.


title: Runaway Merging of Black Holes: Analytical Constraint on the Timescale

abstract:
  Following the discovery of a black hole (BH) with a mass of 10^3-10^6 M(sun)
in a starburst galaxy M82, we study formation of such a BH via successive
merging of stellar-mass BHs within a star cluster. The merging has a runaway
characteristic. This is because massive BHs sink into the cluster core and have
a high number density, and because the merging probability is higher for more
massive BHs. We use the Smoluchowski equation to study analytically the
evolution of the BH mass distribution. Under favorable conditions, which are
expected for some star clusters in starburst galaxies, the timescale of the
runaway merging is at most of order 10^7 yr. This is short enough to account
for the presence of a BH heavier than 10^3 M(sun) in an ongoing starburst
region.


title:
Ram-Ppressure Effects on Dense Molecular Arms in the Central Regions of
  Spiral Galaxies by Intracluster Medium

abstract:
  We investigated ram-pressure effects by an intracluster wind on an inner disk
of spiral galaxies by a hydrodynamical simulation. Even if the wind is mild and
not strong enough to strip the gas disk, the ram pressure disturbs orbits of
the inter-arm gas significantly. This results in asymmetric dense molecular
arms in the inner few kpc region of a galaxy. This mechanism would explain the
asymmetric CO gas distributions in the central regions often observed in Virgo
spirals.


title: Properties of mm galaxies: Constraints from K-band blank fields

abstract:
  We have used the IRAM Plateau de Bure mm interferometer to locate with
subarcsecond accuracy the dust emission of three of the brightest 1.2mm sources
in the NTT Deep Field (NDF) selected from our 1.2mm MAMBO survey at the IRAM
30m telescope. We combine these results with deep B to K imaging and VLA
interferometry. Strikingly, none of the three accurately located mm galaxies
MMJ120546-0741.5, MMJ120539-0745.4, and MMJ120517-0743.1 has a K-band
counterpart down to the faint limit of K>21.9. This implies that these three
galaxies are either extremely obscured and/or are at very high redshifts
(z>~4). We combine our results with literature data for 11 more (sub)mm
galaxies that are identified with similar reliability. In terms of their K-band
properties, the sample divides into three roughly equal groups: (i) undetected
to K~22, (ii) detected in the near-infrared but not the optical and (iii)
detected in the optical with the possibility of optical follow-up spectroscopy.
We find a trend in this sample between near-infrared to submm and submm to
radio spectral indices, which in comparison to spectral energy distributions
(SEDs) of low redshift infrared luminous galaxies suggests that the most
plausible primary factor causing the extreme near-infrared faintness of our
objects is their high redshift. We show that the near-infrared to radio SEDs of
the sample are inconsistent with SEDs that resemble local far-infrared cool
galaxies with moderate luminosities, which were proposed in some models of the
submm sky. We briefly discuss the implications of the results for our
understanding of galaxy formation.


title:
In Hot Pursuit of the Hidden Companion of Eta Carinae: An X-ray
  Determination of the Wind Parameters

abstract:
  We present X-ray spectral fits to a recently obtained Chandra grating
spectrum of Eta Carinae, one of the most massive and powerful stars in the
Galaxy and which is strongly suspected to be a colliding wind binary system.
Hydrodynamic models of colliding winds are used to generate synthetic X-ray
spectra for a range of mass-loss rates and wind velocities. They are then
fitted against newly acquired Chandra grating data. We find that due to the low
velocity of the primary wind (~500 km/s), most of the observed X-ray emission
appears to arise from the shocked wind of the companion star. We use the
duration of the lightcurve minimum to fix the wind momentum ratio at 0.2. We
are then able to obtain a good fit to the data by varying the mass-loss rate of
the companion and the terminal velocity of its wind. We find that Mdot ~ 1e-5
Msol/yr and v ~ 3000 km/s. With observationally determined values of ~500-700
km/s for the velocity of the primary wind, our fit implies a primary mass-loss
rate of Mdot ~ 2.5e-4 Msol/yr. This value is smaller than commonly inferred,
although we note that a lower mass-loss rate can reduce some of the problems
noted by Hillier et al. (2001) when a value as high as 1e-3 Msol/yr is used.
The wind parameters of the companion are indicative of a massive star which may
or may not be evolved. The line strengths appear to show slightly sub-solar
abundances, although this needs further confirmation. Based on the
over-estimation of the X-ray line strengths in our model, and re-interpretation
of the HST/FOS results, it appears that the homunculus nebula was produced by
the primary star.


title: Theoretical models for Bump Cepheids

abstract:
  We present the results of a theoretical investigation aimed at testing
whether full amplitude, nonlinear, convective models account for the I-band
light curves of Bump Cepheids in the Large Magellanic Cloud (LMC). We selected
two objects from the OGLE sample that show a well-defined bump along the
decreasing (short-period) and the rising (long-period) branch respectively. We
find that current models do reproduce the luminosity variation over the entire
pulsation cycle if the adopted stellar mass is roughly 15 % smaller than
predicted by evolutionary models that neglect both mass loss and convective
core overshooting. Moreover, we find that the fit to the light curve of the
long-period Cepheid located close to the cool edge of the instability strip
requires an increase in the mixing length from 1.5 to 1.8 Hp. This suggests an
increase in the efficiency of the convective transport when moving toward
cooler effective temperatures. Current pulsation calculations supply a LMC
distance modulus ranging from 18.48 to 18.58 mag.


title:
Chandra ACIS-S Observations of Abell 4059: Signs of Dramatic Interaction
  Between a Radio Galaxy and a Galaxy Cluster

abstract:
  We present Chandra observations of the galaxy cluster A4059. We find strong
evidence that the FR-I radio galaxy PKS 2354-35 at the center of A4059 is
inflating cavities with radii ~20 kpc in the intracluster medium, similar to
the situation seen in Perseus A and Hydra A. We also find evidence for
interaction between the intracluster medium and PKS 2354-35 on small scales in
the very center of the cluster. Arguments are presented suggesting that this
radio galaxy has faded significantly in radio power (possibly from an FR-II
state) over the past 10^8 yrs.


title: Statistical Constraints On Non-Cosmological Subclasses Of GRBs

abstract:
  There still exists the possibility that the phenomenon of gamma-ray bursts
(GRBs) is a mixture of events of different nature, even within the class of
long (>2 s) bursts. We try to put statistical constraints on a possible
non-cosmological component using the uniform GRB catalog of Stern & Tikhomirova
obtained from an overall scan of the full 9.1 year BATSE 1024 ms data. The
sample consists of 3906 GRBs and includes non-triggered bursts with peak fluxes
down to 0.1 photons cm$^{-2}$ s$^{-1}$. We find no significant deviations from
isotropy. The constraints on a non-cosmological population are still weak. The
allowed contribution of a GRB subpopulation originating from an extended
galactic halo is about 60% and the upper limit on an Eucledian component (e.g.,
nearby galactic or non-cosmological extragalactic GRBs) is 23%. The results
concern mainly the class of long GRBs.


title: On the scent of the knee - air shower measurements with KASCADE

abstract:
  Detailed investigations of extensive air showers have been performed with the
data measured by the KASCADE experiment. The results allow to evaluate hadronic
interaction models, used in simulations to interpret air shower data. The
all-particle spectrum of cosmic rays and their mass composition, as well as
individual spectra for groups of elements have been reconstructed. The results
suggest, the knee in the all-particle cosmic--ray energy spectrum is caused by
a rigidity-dependent cut-off of individual element groups.


title: Massive Close Binaries

abstract:
  The evolution of massive stars in general, massive close binaries in
particular depend on processes where, despite many efforts, the physics are
still uncertain. Here we discuss the effects of stellar wind as function of
metallicity during different evolutionary phases and the effects of rotation
and we highlight the importance for population (number) synthesis. Models are
proposed for the X-ray binaries with a black hole component. We then present an
overall scheme for a massive star PNS code. This code, in combination with an
appropriate set of single star and close binary evolutionary computations
predicts the O-type star and Wolf-Rayet star population, the population of
double compact star binaries and the supernova rates, in regions where star
formation is continuous in time.


title: CHANDRA Detection of 16 New X-Ray Sources

abstract:
  We have detected 18 sources over 6 sigma threshold within two regions
8.3X16.9 arcmin^2 and 8.3X33.6 arcmin^2 in the vicinity of the point with
alpha=03h31m02.45s (J2000) and delta=+43degree47arcmin58.5arcsec (J2000) using
a CHANDRA ACIS (S+I) observation. Two of the sources were detected before with
$ROSAT$ HRI and one source could be closely identified with a star in the
optical catalog, USNO A-2. We have also studied source spectra applying four
spectral models to the data. Most of the sources can be classified as
Cataclysmic Variable, Low Mass X-ray Binary or single star candidates due to
their spectral characteristics and luminosities. We also searched for the
extragalactic origin for these 18 sources. The source count rates vary between
5.8X10^{-4}- 4.7X10^{-3} counts/s. Due to low count rates temporal
characteristics of the sources can not be studied effectively.


title:
Dust and hydrogen molecules in the extremely metal-poor dwarf galaxy SBS
  0335-052

abstract:
  During the early stages of galaxy evolution, the metallicity is generally low
and nearby metal-poor star-forming galaxies may provide templates for
primordial star formation. In particular, the dust content of such objects is
of great importance since early molecular formation can take place on grains.
To gain insight into primeval galaxies at high redshift, we examine the dust
content of the nearby extremely low-metallicity galaxy SBS 0335-052 which hosts
a very young starburst (< 10 Myr). In young galaxies, the dust formation rate
in Type II supernovae governs the amount of dust, and by incorporating recent
results on dust production in Type II supernovae we model the evolution of dust
content. If the star-forming region is compact (< 100 pc), as suggested by
observations of SBS 0335-052, our models consistently explain the quantity of
dust, far-infrared luminosity, and dust temperature in this low-metallicity
object. We also discuss the H_2 abundance. The compactness of the region is
important to H_2 formation, because the optical depth of dust for UV photons
becomes large and H_2 dissociation is suppressed. We finally focus on
implications for damped Ly alpha systems.


title:
Parity Violating Measurements of Neutron Densities: Implications for
  Neutron Stars

abstract:
  Parity violating electron scattering can measure the neutron density of a
heavy nucleus accurately and model independently. This is because the weak
charge of the neutron is much larger then that of the proton. The Parity Radius
Experiment (PREX) at Jefferson Laboratory aims to measure the root mean square
neutron radius of $^{208}$Pb with an absolute accuracy of 1% ($\pm 0.05$ Fm).
This is more accurate then past measurements with hadronic probes, which all
suffer from controversial strong interaction uncertainties. PREX should clearly
resolve the neutron-rich skin. Furthermore, this benchmark value for $^{208}$Pb
will provide a calibration for hadronic probes, such as proton scattering,
which can then be used to measure neutron densities of many exotic nuclei. The
PREX result will also have many implications for neutron stars. The neutron
radius of Pb depends on the pressure of neutron-rich matter: the greater the
pressure, the larger the radius as neutrons are pushed out against surface
tension. The same pressure supports a neutron star against gravity. The Pb
radius is sensitive to the equation of state at normal densities while the
radius of a 1.4 solar mass neutron star also depends on the equation of state
at higher densities. Measurements of the radii of a number of isolated neutron
stars such as Geminga and RX J185635-3754 should soon improve significantly. By
comparing the equation of state information from the radii of both Pb and
neutron stars one can search for a softening of the high density equation of
state from a phase transition to an exotic state. Possibilities include kaon
condensates, strange quark matter or color superconductors.


title:
Binary coalescence of a strange star with a black hole: Newtonian
  results

abstract:
  We present Newtonian three-dimensional hydrodynamical simulations of the
merger of quark stars with black holes. The initial conditions correspond to
non-spinning stars in Keplerian orbits, the code includes gravitational
radiation reaction in the quadrupole approximation for point masses. We find
that the quark star is disrupted, forming transient accretion structures around
the black hole, but 0.03 of the original stellar mass survives the initial
encounter and remains in an elongated orbit as a rapidly rotating quark
starlet, in all cases. No resolvable amount of mass is dynamically ejected
during the encounters--the black hole eventually accretes 99.99% +/- 0.01% of
the quark matter initially present.


title: On the Origin of the Internal Structure of Haloes

abstract:
  High-resolution N-body simulations of hierarchical cosmologies have shown
that the density and velocity dispersion profiles of dark-matter haloes display
well-definite universal forms whose origin remains unknown. In the present
paper, we calculate the internal structure of haloes expected to arise in any
such cosmologies by simply taking into account that halo growth proceeds
through an alternate sequence of discrete major mergers and long periods of
gentle accretion. Major mergers cause the violent relaxation of the system
subject to the boundary conditions imposed by accreting layers beginning to
fall in at that moment. Accretion makes the system develop inside-out from the
previous seed according to the spherical infall model. The predicted structure
is in very good agreement with the results of numerical simulations,
particularly for moderate and low mass haloes. We find strong indications that
the slight departure observed in more massive systems is not due to a poorer
theoretical prediction, but to the more marked effects of the limited
resolution used in the simulations on the empirical profiles. This may have
important consequences on the reported universality of halo structure.


title: Chandra Discovery of a 300 kpc X-ray Jet in the GPS Quasar PKS1127-145

abstract:
  We have discovered an X-ray jet with Chandra imaging of the z=1.187
radio-loud quasar PKS1127-145. In this paper we present the Chandra X-ray data,
follow-up VLA observations, and optical imaging using the HST WFPC2. The X-ray
jet contains 273+/-5 net counts in 27ksec and extends ~30 arcsec, from the
quasar core, corresponding to a minimum projected linear size of ~330/h_50 kpc.
The evaluation of the X-ray emission processes is complicated by the observed
offsets between X-ray and radio brightness peaks. We discuss the problems posed
by these observations to jet models. In addition, PKS1127-145 is a Giga-Hertz
Peaked Spectrum radio source, a member of the class of radio sources suspected
to be young or ``frustrated'' versions of FRI radio galaxies. However the
discovery of an X-ray and radio jet extending well outside the host galaxy of
PKS1127-145 suggests that activity in this and other GPS sources may be
long-lived and complex.


title: Gravitational Bending of Light Near Compact Objects

abstract:
  A photon emitted near a compact object at an angle $\alpha$ with respect to
the radial direction escapes to infinity at a different angle $\psi>\alpha$.
This bending of light is caused by a strong gravitational field. We show that,
in a Schwarzschild metric, the effect is described by
$1-\cos\alpha=(1-\cos\psi)(1-r_g/R)$ where $R/r_g$ is the emission radius in
Schwarzschild units. The formula is approximate and it applies at $R\geq 2r_g$
only, however at these radii it has amazing accuracy, fully sufficient in many
applications. As one application we develop a new formulation for the light
bending effects in pulsars. It reveals the simple character of these effects
and gives their quantitative description with practically no losses of accuracy
(for the typical radius of a neutron star $R=3r_g$ the error is 1%). The
visible fraction of a star surface is shown to be $S_v/4\pi
R^2=[2(1-r_g/R)]^{-1}$ which is 3/4 for $R=3r_g$. The instantaneous flux of a
pulsar comes from one or two antipodal polar caps that rotate in the visible
zone. The pulse produced by one blackbody cap is found to be sinusoidal (light
bending impacts the pulse amplitude but not its shape). When both caps are
visible, the pulse shows a plateau: the variable parts of the antipodal
emissions precisely cancel each other. The pulsed fraction of blackbody
emission with antipodal symmetry has an upper limit
$A_{max}=(R-2r_g)/(R+2r_g)$. Pulsars with $A>A_{max}$ must be asymmetric.


title: Spectroscopic Diagnostics for AGNs

abstract:
  A review of the spectroscopic tools needed to characterize AGNs is presented.
This review focusses on ultraviolet, optical and infrared emission-line
diagnostics specifically designed to help differentiate AGNs from
starburst-dominated galaxies. The strengths and weaknesses of these methods are
discussed in the context of on-going and future AGN surveys.


title: Probing Galaxy Formation with High Energy Gamma-Rays

abstract:
  I discuss how measurements of the absorption of $\gamma$-rays from GeV to TeV
energies via pair production on the extragalactic background light (EBL) can
probe important issues in galaxy formation. We use semi-analytic models (SAMs)
of galaxy formation, based on the flat LCDM hierarchical structure formation
scenario with $\Omega_m=0.3$ and Hubble parameter $h=0.65$, to obtain
predictions of the EBL from 0.1 to 1000$\mu$m. SAMs incorporate simplified
physical treatments of the key processes of galaxy formation - including
gravitational collapse and merging of dark matter halos, gas cooling and
dissipation, star formation, supernova feedback and metal production -- and
have been shown to reproduce key observations at low and high redshift. We
investigate the consequences of variations in input assumptions such as the
stellar initial mass function (IMF) and the efficiency of converting cold gas
into stars. We also discuss recent attempts to determine the emitted spectrum
of high energy gamma rays from blazars such as Mrk 501 from the observed X-rays
using the synchrotron self-Compton model, and note that our favorite SAM EBL
plus the observed spectrum of Mrk 501 do not imply unphysical upturns in the
high energy emitted spectrum - thus undermining recent claims of a crisis with
drastic possible consequences such as breaking of Lorentz invariance. We
conclude that observational studies of the absorption of $\gamma$-rays will
help to determine the EBL, and also help to explain its origin by constraining
some of the most uncertain features of galaxy formation theory, including the
IMF, the history of star formation, and the reprocessing of light by dust.


title:
Eigenoscillations of the Differentially Rotating Sun: I. 22-year,
  4000-year, and quasi-biennial modes

abstract:
  Retrograde waves with frequencies much lower than the rotation frequency
become trapped in the solar radiative interior. The eigenfunctions of the
compressible, nonadiabatic, Rossby-like modes ($\epsilon$-mechanism and
radiative losses taken into account) are obtained by an asymptotic method
assuming a very small latitudinal gradient of rotation, without an arbitrary
choice of other free parameters. An integral dispersion relation for the
complex eigenfrequencies is derived as a solution of the boundary value
problem. The discovered resonant cavity modes (called R-modes) are
fundamentally different from the known r-modes: their frequencies are functions
of the solar interior structure, and the reason for their existence is not
related to geometrical effects. The most unstable R-modes are those with
periods of 1--3 yr, 18--30 yr, and 1500--20000 yrs; these three separate period
ranges are known from solar and geophysical data. The growing times of those
modes which are unstable with respect to the $\epsilon$-mechanism are $\approx
10^2, 10^3,$ and $10^5$ years, respectively. The amplitudes of the R-modes are
growing towards the center of the Sun. We discuss some prospects to develop the
theory of R-modes as a driver of the dynamics in the convective zone which
could explain, e.g., observed short-term fluctuations of rotation, a control of
the solar magnetic cycle, and abrupt changes of terrestrial climate in the
past.


title:
Variation of Spot-induced Anomalies in Caustic-crossing Binary
  Microlensing Event Light Curves

abstract:
  We investigate the pattern of anomalies in the light curves of
caustic-crossing binary microlensing events induced by spot(s) on the lensed
source star. For this purpose, we perform simulations of events with various
models of spots. From these simulations, we find that the spot-induced
anomalies take various forms depending on the physical state of spots, which is
characterized by the surface brightness contrast, the size, the number, the
umbra/penumbra structure, the shape, and the orientation with respect to the
sweeping caustic. We also examine the feasibility of distinguishing the two
possibly degenerate types of anomalies caused by a spot and a transiting planet
and find that the degeneracy in many cases can be broken from the
characteristic multiple deviation feature in the spot-induced anomaly pattern
caused by the multiplicity of spots.


title:
Search for variations in circular-polarization spectra of the magnetic
  white dwarf LP790-29

abstract:
  We present highly time resolved circular-polarization and flux spectra of the
magnetic white dwarf LP790-29 taken with the VLT UT1 in order to test the
hypothesis that LP790-29 is a fast rotator with a period of the order of
seconds to minutes. Due to low time resolution of former observations this
might have been overlooked -- leading to the conclusion that LP790-29 has a
rotational period of over 100 years. The optical spectrum exhibits one
prominent absorption feature with minima at about 4500, 4950, and 5350 A, which
are most likely C2 Swan-bands shifted by about 180 A in a magnetic field
between 50MG and 200MG. At the position of the absorption structures the degree
of circular polarization varies between -1% and +1%, whereas it amounts to +8
to +10% in the blue and red continuum. With this very high degree of
polarization lp790-29 is very well suited to a search for short time
variations, since a variation of several percent in the polarization can be
expected for a magnetic field oblique to the rotational axis. From our analysis
we conclude that variations on time scales from 50 to 2500 seconds must have
amplitudes <0.7% in the continuum and <2% in the strongest absorption feature
at 4950A. While no short-term variations could be found a careful comparison of
our polarization data of LP790-29 with those in the literatures indicates
significant variations on time scales of decades with a possible period of
about 24-28 years.


title:
On the observational properties of He-burning stars: some clues on the
  tilt of the HB in metal rich clusters

abstract:
  We investigate the predicted Color-Magnitude distribution of metal-rich
Horizontal Branch (HB) stars, discussing selected theoretical models computed
under various assumptions about the star metallicity and the efficiency of
super-adiabatic convection. We find that canonical Zero Age Horizontal Branches
with metallicity larger or of the order of Z=0.002 should be all affected by a
tilt, by an amount which increases when the metallicity is increased and/or the
mixing length is decreased, reaching a tilt of $\Delta V \sim$0.2 mag in the
case of solar metallicity when a mixing length value $\alpha$=1.6 is assumed
($\Delta V$ is the magnitude difference between the top of the blue HB and the
fainter magnitude reached by the red HB). Uncertainties in the luminosity of
the red HB due to uncertainty in the mixing length value are discussed. We
finally discuss the much larger tilt observed in the clusters NGC 6441 and NGC
6388, reporting additional evidence against suggested non-canonical
evolutionary scenarios. Numerical experiments show that differential reddening
could produce such sloped HBs. Further, HST-PC imaging of NGC 6441 gives clear
indications about the occurrence of differential reddening across the cluster.
However, the same imaging shows that the observed slope of the red HB {\em is
not} an artifact of differential reddening. We finally show that sloping red
HBs in metal rich clusters are a common occurrence not necessarily correlated
with the appearance of extended blue HB.


title: An analytical model for the non-linear redshift-space power spectrum

abstract:
  We use N-body simulations to test the predictions of the redshift distortion
in the power spectrum given by the halo model in which the clustering of dark
matter particles is considered as a result both of the clustering of dark halos
in space and of the distribution of dark matter particles in individual dark
halo. The predicted redshift distortion depends sensitively on several model
parameters in a way different from the real-space power spectrum. An accurate
model of the redshift distortion can be constructed if the following properties
of the halo population are modelled accurately: the mass function of dark
halos, the velocity dispersion among dark halos, and the non-linear nature of
halo bias on small scales. The model can be readily applied to interpreting the
clustering properties and velocity dispersion of different populations of
galaxies once a cluster-weighted bias (or equivalently an halo occupation
number model) is specified for the galaxies. Some non-trivial bias features
observed from redshift surveys of optical galaxies and of IRAS galaxies
relative to the standard low-density cold dark matter model can be easily
explained in the cluster weighted bias model. The halo model further indicates
that a linear bias can be a good approximation only on for k <= 0.1 hMpc^{-1}.


title: Cooling Flows as a Calorimeter of AGN Mechanical Power

abstract:
  The assumption that radiative cooling of gas in the centers of galaxy
clusters is approximately balanced by energy input from a central supermassive
black hole implies that the observed X-ray luminosity of the cooling flow
region sets a lower limit on AGN mechanical power. The conversion efficiency of
AGN mechanical power into gas heating is uncertain, but we argue that it can be
high even in the absence of strong shocks. These arguments inevitably lead to
the conclusion that the time averaged mechanical power of AGNs in cooling flows
is much higher than the presently observed bolometric luminosity of these
objects.
  The energy balance between cooling losses and AGN mechanical power requires
some feedback mechanism. We consider a toy model in which the accretion rate
onto a black hole is set by the classic Bondi formula. Application of this
model to the best studied case of M87 suggests that accretion proceeds at
approximately the Bondi rate down to a few gravitational radii with most of the
power (at the level of a few percent of the rest mass) carried away by an
outflow.


title: Strangeness Nucleation in Neutron Star Matter

abstract:
  We study the transition from npe-type nuclear matter (consisting of neutrons,
protons, and electrons) to matter containing strangeness, using a Walecka-type
model predicting a first-order kaon-condensate phase transition. We examine the
free energy of droplets of K-matter as the density, temperature, and neutrino
fraction are varied. Langer nucleation rate theory is then used to approximate
the rate at which critical droplets of the new phase are produced by thermal
fluctuations, thus giving an estimate of the time required for the new (mixed)
phase to appear at various densities and various times in the cooling history
of the proto-neutron star. We also discuss the famous difficulty of
"simultaneous weak interactions" which we connect to the literature on
non-topological solitons. Finally, we discuss the implications of our results
to several phenomenological issues involving neutron star phase transitions.


title: Constraining the Dark Universe

abstract:
  We combine complementary datasets to constrain dark energy. Using standard
Big Bang Nucleosynthesis and the observed abundances of primordial nuclides to
put constraints on $\Omega_Q$ at temperatures near $T \sim 1MeV$, we find the
strong constraint $\Omega_Q({MeV}) < 0.045$ at $2\sigma$ c.l.. Under the
assumption of flatness, using results from Cosmic Microwave Background (CMB)
anisotropy measurements, high redshift supernovae (SN-Ia) observations and data
from local cluster abundances we put a new constraint on the equation of state
parameter $w_Q < -0.85$ at 68% c.l..


title:
Dust and the spectral energy distribution of the OH/IR star OH
  127.8+0.0: Evidence for circumstellar metallic iron

abstract:
  We present a fit to the spectral energy distribution of OH 127.8+0.0, a
typical asymptotic giant branch star with an optically thick circumstellar dust
shell. The fit to the dust spectrum is achieved using non-spherical grains
consisting of metallic iron, amorphous and crystalline silicates and water ice.
Previous similar attempts have not resulted in a satisfactory fit to the
observed spectral energy distributions, mainly because of an apparent lack of
opacity in the 3--8 micron region of the spectrum. Non-spherical metallic iron
grains provide an identification for the missing source of opacity in the
near-infrared. Using the derived dust composition, we have calculated spectra
for a range of mass-loss rates in order to perform a consistency check by
comparison with other evolved stars. The L-[12 micron] colours of these models
correctly predict the mass-loss rate of a sample of AGB stars, strengthening
our conclusion that the metallic iron grains dominate the near-infrared flux.
We discuss a formation mechanism for non-spherical metallic iron grains.