title:
A Warped Accretion Disk and Wide Angle Outflow in the Inner Parsec of
  the Circinus Galaxy

abstract:
  We present the first VLBI maps of H2O maser emission (lambda 1.3cm) in the
nucleus of the Circinus Galaxy, constructed from data obtained with the
Australia Telescope Long Baseline Array. The maser emission traces a warped,
edge-on accretion disk between radii of 0.11+/-0.02 and ~0.40 pc, as well as a
wide-angle outflow that extends up to ~1 pc from the estimated disk center. The
disk rotation is close to Keplerian (v varies as 1/sqrt(r)), the maximum
detected rotation speed is 260 km/s, and the inferred central mass is 1.7+/-0.3
x 10^6 solar masses. The outflowing masers are irregularly distributed above
and below the disk, with relative outflow velocities up to ~+/-160 km/s,
projected along the line of sight. The flow probably originates closer than 0.1
pc to the central engine, possibly in an inward extension of the accretion
disk, though there is only weak evidence of rotation in the outward moving
material. We observe that the warp of the disk appears to collimate the outflow
and to fix the extent of the ionization cone observed on larger angular scales.
This study provides the first direct evidence (i.e., through imaging) of dusty,
high-density, molecular material in a nuclear outflow <1 pc from the central
engine of a Seyfert galaxy, as well as the first graphic evidence that warped
accretion disks can channel outflows and illumination patterns in AGN. We
speculate that the same arrangement, which in some ways obviates the need for a
geometrically thick, dusty torus, may apply to other type-2 AGN.


title:
Complex C: A Low-Metallicity High-Velocity Cloud Plunging into the Milky
  Way

abstract:
  (Abridged) We present a new high-resolution (7 km/s FWHM) echelle spectrum of
3C 351 obtained with STIS. 3C 351 lies behind the low-latitude edge of
high-velocity cloud Complex C, and the new spectrum provides accurate
measurements of O I, Si II, Al II, Fe II, and Si III absorption lines at the
velocity of the HVC. We use collisional and photoionization models to derive
ionization corrections; in both models we find that the overall metallicity Z =
0.1 - 0.3 Z_{solar} in Complex C, but nitrogen must be underabundant. The iron
abundance indicates that Complex C contains very little dust. The absorbing gas
probably is not gravitationally confined. The gas could be pressure-confined by
an external medium, but alternatively we may be viewing the leading edge of the
HVC, which is ablating and dissipating as it plunges into the Milky Way. O VI
column densities observed with FUSE toward nine QSOs/AGNs behind Complex C
support this conclusion: N(O VI) is highest near 3C 351, and the O VI/H I ratio
increases substantially with decreasing latitude, suggesting that the
lower-latitude portion of the cloud is interacting more vigorously with the
Galaxy. The other sight lines through Complex C show some dispersion in
metallicity, but with the current uncertainties, the measurements are
consistent with a constant metallicity throughout the HVC. However, all of the
Complex C sight lines require significant nitrogen underabundances. Finally, we
compare the 3C 351 sight line to the sight line to the nearby QSO H1821+643 to
search for evidence of outflowing Galactic fountain gas that could be mixing
with Complex C. We find that the intermediate-velocity gas detected toward 3C
351 and H1821+643 has a higher metallicity and may well be a fountain/chimney
outflow from the Perseus spiral arm.


title:
XMM-Newton Spectroscopy of Bright ULX Sources in the Antennae Galaxies
  (NGC 4038/4039)

abstract:
  We report the results of spectral fits to four bright ultra-luminous X-ray
sources (ULXs) in the Antennae galaxies (NGC 4038/4039) observed for 41 ksec
with XMM-Newton. Although emission regions are not resolved as well as in prior
Chandra observations, at least four ULXs (X-11, X-16, X-37, and X-44 in the
Zezas and Fabbiano scheme) are sufficiently bright and well-separated with
XMM-Newton that reliable extractions and spectral analyses are possible. We
find that the single component multi-color disk blackbody models cannot
describe any of the spectra. Sources X-11 and X-16 are acceptably fit with
simple power-law models. A thermal bremsstrahlung model provides a better fit
to the spectrum of X-44. Including a disk blackbody component to the spectrum
of X-37 improves the fit and reveals an apparently cool disk (kT = 0.13 +/-
0.02 keV). This would suggest a parallel to cool disks recently found in other
very luminous ULXs, which may contain intermediate mass black holes; however,
the complex diffuse emission of the Antennae demands this finding be regarded
cautiously.


title: Lensing Reconstruction with CMB Temperature and Polarization

abstract:
  Weak gravitational lensing by intervening large-scale structure induces a
distinct signature in the cosmic microwave background (CMB) that can be used to
reconstruct the weak-lensing displacement map. Estimators for individual
  Fourier modes of this map can be combined to produce an estimator for the
lensing-potenial power spectrum. The naive estimator for this quantity will be
biased upwards by the uncertainty associated with reconstructing individual
modes; we present an iterative scheme for removing this bias. The variance and
covariance of the lensing-potenial power spectrum estimator are calculated and
evaluated numerically in a
  $\Lambda$CDM universe for Planck and future polarization-sensitive CMB
experiments.


title:
Determination of Reddening and Extinction Due to Dust in APM Galaxy
  Clusters

abstract:
  Existing observations are consistent with rich clusters of galaxies having no
dust on $\simgt$ Mpc scales, while galaxy groups most probably do have dust
distributed over $\lesssim$ Mpc scales. Dust in groups accounts for the
observed redshift asymmetries of their galaxy distributions, and about
$E(B-V)\sim 0.1-0.2$ mag of reddening. Motivated by these results, we develop a
new technique for determining the degree of reddening and extinction due to
widely-distributed dust in nearby moderately rich and poor galaxy clusters. The
method compares the color-magnitude plane distributions of galaxies from
cluster and control regions on the sky, where control regions are assumed to be
unaffected by dust. The method is statistical in nature; it can distinguish
between uniformly, non-uniformly, and clumpily distributed dust, and can
determine the amount of reddening and obscuration without a priori assuming an
$A_R/E(B_{J}-R)$ ratio. We apply the method to nearby, $z \le 0.08$, medium
rich and poor APM galaxy clusters. We detect no dust in these on 1.3 Mpc scales
(we assume $h = 0.75$), and derive 99% confidence upper limits on extinction of
$A_{R} = 0.025 $ and reddening of $E(B_{J} - R) = 0.025 ($which corresponds to
$E(B - V) \approx 0.02)$. We test the method using clusters whose galaxies have
been artificially reddened and obscured by various amounts, and conclude that
it robustly recovers the input values for reddening, its distribution, and the
ratio of total-to-selective extinction. The method can be applied to any set of
galaxy clusters or groups constructed out of homogeneous and uniform two-color
galaxy catalogs.


title:
In-the-Gap SU UMa-Type Dwarf Nova, Var73 Dra with a Supercycle of about
  60 Days

abstract:
  An intensive photometric-observation campaign of the recently discovered SU
UMa-type dwarf nova, Var73 Dra was conducted from 2002 August to 2003 February.
We caught three superoutbursts in 2002 October, December and 2003 February. The
recurrence cycle of the superoutburst (supercycle) is indicated to be $\sim$60
d, the shortest among the values known so far in SU UMa stars and close to
those of ER UMa stars. The superhump periods measured during the first two
superoutbursts were 0.104885(93) d, and 0.10623(16) d, respectively. A
0.10424(3)-d periodicity was detected in quiescence. The change rate of the
superhump period during the second superoutburst was $1.7\times10^{-3}$, which
is an order of magnitude larger than the largest value ever known. Outburst
activity has changed from a phase of frequent normal outbursts and infrequent
superoutbursts in 2001 to a phase of infrequent normal outbursts and frequent
superoutbursts in 2002. Our observations are negative to an idea that this star
is an related object to ER UMa stars in terms of the duty cycle of the
superoutburst and the recurrence cycle of the normal outburst. However, to
trace the superhump evolution throughout a superoutburst, and from quiescence
more effectively, may give a fruitful result on this matter.


title: Kinematic response of the outer stellar disk to a central bar

abstract:
  We study, using direct orbit integrations, the kinematic response of the
outer stellar disk to the presence of a central bar, as in the Milky-Way. We
find that the bar's outer Lindblad resonance (OLR) causes significant
perturbations of the velocity moments. With increasing velocity dispersion, the
radius of these perturbations is shifted outwards, beyond the nominal position
of the OLR, but also the disk becomes less responsive. If we follow Dehnen
(2000) in assuming that the OLR occurs just inside the Solar circle and that
the Sun lags the bar major axis by ~20 degrees, we find (1) no significant
radial motion of the local standard of rest (LSR), (2) a vertex deviation of
\~10 degrees and (3) a lower ratio sigma_2/sigma_1 of the principal components
of the velocity- dispersion tensor than for an unperturbed disk. All of these
are actually consistent with the observations of the Solar-neighbourhood
kinematics. Thus it seems that at least the lowest-order deviations of the
local-disk kinematics from simple expectations based on axisymmetric
equilibrium can be attributed entirely to the influence of the Galactic bar.


title: AXPs and X-ray dim neutron stars: Recent XMM-Newton and Chandra results

abstract:
  To date more than half a dozen X-ray dim isolated neutron stars are known.
Their X-ray spectra are characterized by soft blackbody-like emission (kT about
50-120 eV) without indication for harder, non-thermal components. These stars
apparently show no radio emission and no association with supernova remnants.
Four of them exhibit pulsations in their X-ray flux with periods in the range
of 8.39 s to 22.7 s. Similar pulse periods were found from AXPs, maybe
suggesting evolutionary connections. In this talk I will review the recent
observational results from X-ray dim isolated neutron obtained by the major
X-ray observatories XMM-Newton and Chandra. Spectral and temporal
characteristics, inferred luminosities and magnetic field strengths will be
compared with those of AXPs.


title: On The Nature of Low Luminosity Narrow Line AGN

abstract:
  There is clear observational evidence that some narrow line (type 2) AGN have
a hidden broad line region (BLR), and are thus intrinsically broad line (type
1) AGN. Does this AGN unification applies for all type 2 AGN? Indirect
arguments suggest that some "true" type 2 AGN, i.e. AGN having no obscured BLR
do exist, but it is not clear why the BLR is missing in these AGN. Here we
point out a possible natural explanation. The observed radius-luminosity
relation for the BLR implies an increasing line width with decreasing
luminosity for a given black hole mass (Mbh). In addition, there appears to be
an upper limit to the observed width of broad emission lines in AGN of Delta
v_max~25,000 km/s, which may reflect a physical limit above which the BLR may
not be able to survive. Thus, at a low enough luminosity the BLR radius shrinks
below the Delta v_max radius, leaving no region where the BLR can exist,
although the AGN may remain otherwise `normal'. The implied minimum bolometric
luminosity required to sustain a BLR with Delta v<25,000 km/s is
L_min~10^{41.8}(Mbh}/10^8M_sun)^2. All AGN with L<L_min are expected to be
`true' type 2 AGN, i.e. narrow line AGN without a hidden BLR. Predictions for
the true nature of low luminosity AGN in two samples of nearby galaxies are
provided. These can be used to test the above L_min conjecture, and the
predictions of other models for the size and origin of the BLR.


title:
The SED in the hot continuum of the symbiotic binary AR Pavonis. I.
  Tests with the current models

abstract:
  We present the spectral energy distribution (SED) in the continuum of the
eclipsing symbiotic binary AR Pav between 0.12 and 3.4 microns. This revealed a
high luminosity of the hot object in the binary, L(hot) = 2200(d/4.9 kpc)**2
L(Sun). We introduce a method of disentangling the total continuum spectrum
into its individual components of radiation for current models of symbiotic
binaries. Applying a standard ionization model we show that the configuration
of AR Pav differs significantly from that typical for symbiotic binaries during
their quiescent phases. The best fit of the observed SED is provided by
radiation of a simple blackbody accretion disk with L(AD)=1700(d/4.9 kpc)**2
L(Sun), which is embedded in an extended hot corona with Te=40000+/-5000K and
L(neb)=500 (d/4.9 kpc)**2 L(Sun). This basic configuration of the hot object
explains also the observed wavelength-dependent depth and width of the eclipse
profile. The standard thin disk model requires a high accretion rate dot M(acc)
> 2x1E-4M(Sun)/yr onto the central star with a radius R(acc) > 2R(Sun) to
balance the observed luminosity. Irrespectively to the disk model, the
accretion process limits R(acc) > 0.1R(Sun) for dot M(acc) > 1.7x1E-5 M(Sun)/yr
and M(acc)=0.75 - 1.0M(Sun), which precludes a white dwarf to be the accreting
star. Application of models with the disk and the boundary layer shows that the
far-UV spectrum is not consistent with a large amount of a hot radiation from
the boundary layer.


title:
The Optical and Near-Infrared Properties of Galaxies: I. Luminosity and
  Stellar Mass Functions

abstract:
  We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS)
and the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and
stellar mass functions in the local Universe. We estimate k-corrections,
evolution corrections, and stellar mass-to-light ratios (M/Ls) by fitting the
galaxy colors with simple models. Our optical and near-infrared luminosity
functions agree with most recent literature optical and near-infrared
determinations within the uncertainties. We argue that 2MASS is biased against
low surface brightness galaxies, and use SDSS plus our knowledge of stellar
populations to estimate that the true K-band luminosity function has a steeper
faint end slope than the direct estimate. Assuming a universally-applicable
stellar initial mass function (IMF), we derive the stellar mass function of
galaxies. The faint end slope slope for the stellar mass function is steeper
than -1.1, reflecting the low stellar M/Ls characteristic of low-mass galaxies.
We estimate an upper limit to the stellar mass density in the local Universe
Omega* h = 0.0020+/-0.0006 by assuming an IMF as rich in low-mass stars as
allowed by observations of galaxy dynamics. Finally, we find that the
characteristic luminosity or mass of early-type galaxies is larger than for
later types, and the faint end slope is steeper for later types than for
earlier types. Accounting for typing uncertainties, we estimate that at least
half, and perhaps as much as 3/4, of the stellar mass in the Universe is in
early-type galaxies. We present also SDSS/2MASS color-M/L correlations, an
updated discussion of near-infrared stellar M/L estimates, and the
volume-corrected distribution of g and K-band stellar M/Ls as a function of
stellar mass. [Abridged]


title: Application of the Separate Universe Approach to Preheating

abstract:
  The dynamics of preheating after inflation has not been clearly understood
yet.In particular, the issue of the generation of metric perturbations during
preheating on super-horizon scale is still unsettled. Large scale perturbations
may leave an imprint on the cosmic microwave background, or may become seeds
for generation of primordial black holes. Hence, in order to make a connection
between the particle physics models and cosmological observations,
understanding the evolution of super-Hubble scale perturbations during
preheating is important. Here, we propose an alternative treatment to handle
this issue based on the so-called separate universe approach, which suggests
less efficient amplification of super-Hubble modes during preheating than was
expected before. We also point out an important issue which may have been
overlooked in previous treatments.


title: Is NGC 6752 Hosting a Single or a Binary Black Hole?

abstract:
  The five millisecond pulsars that inhabit NGC 6752 display locations or
accelerations remarkably different with respect to all other pulsars known in
globular clusters. This may reflect the occurrence of an uncommon dynamics in
the cluster core that could be attributed to the presence of a massive
perturber. We here investigate whether a single intermediate-mass black hole,
lying on the extrapolation of the mass versus sigma relation observed in galaxy
spheroids, or, a less massive black hole binary could play the requested role.


title:
RX J004717.4-251811: The first eclipsing X-ray binary outside the Local
  Group

abstract:
  The X-ray source RX J004717.4-251811 in the nearby starburst galaxy NGC 253
was found to undergo changes from a low to a high state twice, during an
XMM-Newton EPIC observation in December 2000 and also during a Chandra
observation one year earlier. These transitions are interpreted as egresses
from eclipses of a compact object in a high mass X-ray binary system (HMXB).
The phase of eclipse egress during the Chandra observation is given by
barycenter corrected MJD 51539.276+-0.006 and the binary period determined to p
= (352.870+-0.012) d / n by the time difference between the two egresses and
number n of periods in-between. Allowed periods may be further constrained by
additional XMM-Newton, Chandra, ROSAT, and Einstein observations resulting in
only seven acceptable periods with 1.47024 d and 3.20793 d most promising. No
significant regular pulsations of the source in the range 0.3-1000 s were
found. Fluctuations on time scales of 1000 s were observed together with
extended intervals of low intensity. The energy spectrum during the bright
state can best be described by an absorbed flat power law (NH=1.9x10^21 cm^-2,
Gamma=1.7). In the bright state the source luminosity is 4x10^38 erg/s (0.5--5
keV), just compatible with the Eddington luminosity of a 1.4 M_sun neutron
star. A possible optical identification is suggested. RX J004717.4-251811
parameters are compared to other eclipsing X-ray binaries (XRBs).


title:
CSL-1: a chance projection effect or serendipitous discovery of a
  gravitational lens induced by a cosmic string?

abstract:
  CSL-1 (Capodimonte--Sternberg--Lens Candidate, No.1) is an extragalactic
double source detected in the OAC-DF (Osservatorio Astronomico di Capodimonte -
Deep Field). It can be interpreted either as the chance alignment of two
identical galaxies at z=0.46 or as the first case of gravitational lensing by a
cosmic string. Extensive modeling shows in fact that cosmic strings are the
only type of lens which (at least at low angular resolution) can produce
undistorted double images of a background source. We propose an experimentum
crucis to disentangle between these two possible explanations. If the lensing
by a cosmic string should be confirmed, it would provide the first measurements
of energy scale of symmetry breaking and of the energy scale of Grand Unified
Theory (GUT).


title: Super-massive stars: Radiative transfer

abstract:
  The concept of central super-massive stars (${\cal M} \ge 5 \times 10^4
M_{\odot}$, where ${\cal M}$ is the mass of the super-massive star) embedded in
dense stellar systems was suggested as a possible explanation for high- energy
emissions phenomena occurring in active galactic nuclei and quasars (Vilkoviski
1976, Hara 1978), such as X-ray emissions (Bahcall and Ostriker, 1975). SMSs
and super-massive black holes are two possibilities to explain the nature of
super-massive central objects, and super-massive stars may be an intermediate
step towards the formation of super-massive black holes (Rees 1984). Therefore
it is important to study such a dense gas-star system in detail. We address
here the implementation of radiative transfer in a model which was presented in
former work (Amaro-Seoane and Spurzem 2001, Amaro-Seoane et al. 2002). In this
sense, we extend here and improve the work done by Langbein et al. (1990) by
describing the radiative transfer in super-massive stars using previous work on
this subject (Castor 1972).


title: On Plasma Oscillations in Strong Electric Fields

abstract:
  We describe the creation and evolution of electron-positron pairs in a strong
electric field as well as the pairs annihilation into photons. The formalism is
based on generalized Vlasov equations, which are numerically integrated. We
recover previous results about the oscillations of the charges, discuss the
electric field screening and the relaxation of the system to a thermal
equilibrium configuration. The timescale of the thermalization is estimated to
be $\sim 10^{3}-10^{4} \hbar /m_{e}c^{2}$.


title:
Chandra ACIS-S Observations of Three Quasars with Low-Redshift Damped
  Ly-alpha Absorption: Constraints on the Cosmic Neutral-Gas-Phase Metallicity
  at Redshift z \approx 0.4

abstract:
  Chandra X-Ray Observatory (CXO) ACIS-S spectra of three quasars which lie
behind three foreground damped Lyman alpha (DLA) absorbers are analyzed in
order to attempt to determine the amount of photoelectric absorption due to
metals present in their x-ray spectra. These absorbers are the three largest
neutral hydrogen column density absorption-line systems known at low redshift
(0.313 \le z_abs \le 0.524). They have HI column densities which lie between
3E21 and 5E21 atoms/cm^2. At these redshifts the amount of photoelectric
absorption at x-ray energies is primarily an indicator of the oxygen abundance.
Since the column densities of these systems are so high, one would expect
accurate metallicity measurements of them to yield a robust estimate of the
column-density-weighted cosmic neutral-gas-phase metallicity at z \approx 0.4.
We consider cases where the DLA gas has solar element abundance ratios and ones
with the alpha-group element abundance ratios enhanced. For the adopted
assumptions, the column-density-weighted cosmic neutral-gas-phase metallicity
of the non-enhanced elements (e.g. Zn) at z \approx 0.4 likely lies in the
range \approx 0.04-0.38 Z_solar.


title:
Multiwavelength studies of the Seyfert 1 galaxy NGC7469. II - X-ray and
  UV observations with XMM-Newton

abstract:
  We present an XMM-Newton observation of NGC 7469, including studies of the
X-ray and UV variability, 0.2-10 keV spectral continuum, Fe K-alpha emission
line and the first-ever high-resolution X-ray spectrum of the soft X-ray warm
absorber. We compare the properties of this X-ray warm absorber with the UV
warm absorber as seen in a FUSE observation one year previously. The 0.2-10 keV
spectral continuum is best fitted by a power-law plus two blackbody model. An
Fe K-alpha emission line is visible which consists of a single narrow component
and is well-modelled by a simple gaussian. Narrow absorption and emission lines
in the soft X-ray RGS spectrum demonstrate the existence of a multi-phase warm
absorber with a range in log xi of ~ 2 to ~ -2 where xi is in erg cm s^-1. The
warm absorber is blueshifted by several hundred km s^-1. The highest-ionisation
phase of the absorber is the best constrained and has an overall equivalent
Hydrogen column of order 10^20 cm^-2; we find that its ionisation parameter is
consistent with that of the warm emitter which generates the narrow emission
lines. We identify this high ionisation absorber with the low-velocity phase of
the UV absorber observed by FUSE.


title:
Multiwavelength studies of the Seyfert 1 galaxy NGC7469. I - Far UV
  observations with FUSE

abstract:
  We obtained far-ultraviolet spectra of the Seyfert 1 galaxy NGC 7469 using
the FUSE on 1999 December 6. Our spectra cover the wavelength range 990-1187 A
with a resolution of 0.05 A. We see broad emission lines of CIII, NIII, OVI,
and HeII as well as intrinsic absorption lines in the OVI 1032,1038 resonance
doublet. The absorption arises in two distinct kinematic components at systemic
velocities of -569 km/s and -1898 km/s. Both components are very highly
ionized- no significant Ly beta absorption is present. The higher blueshift
component is not quite saturated, and it has a total OVI column density of
8e14/cm2. It covers more than 90% of the continuum and broad-line emission. The
lower blue shift component is heavily saturated and covers only 50% of the
continuum and broad-line emission. It too has a column density of 8e14/cm2, but
this is less certain due to the high saturation. We set an upper limit of
<1.5e18/cm2 on the OVI column density of this component. Its line depth is
consistent with coverage of only the continuum, and thus this component may lie
interior to the broad emission-line gas. The component at -569 km/s has a
velocity comparable to the high-ionization X-ray absorption lines seen in the
XMM-Newton grating spectrum of NGC 7469, and photoionization models show that
the observed column densities of OVI and HI are compatible with their formation
in the same gas as that causing the X-ray absorption. The gas at -1898 km/s has
lower ionization and column density, and no significant X-ray absorption is
associated with it.


title:
A medium deep Chandra and Subaru survey of the 13hr XMM/ROSAT deep
  survey area

abstract:
  We present the results of a Chandra ACIS-I survey of a high latitude region
at 13h +38 which was earlier observed with ROSAT (McHardy et al. 1998) and
which has recently been observed by XMM-Newton for 200ksec. XMM-Newton will
provide good quality X-ray spectra for over 200 sources with fluxes around the
knee of the logN/logS, which are responsible for the bulk of the X-ray
background (XRB). The main aim of the Chandra observations is to provide
arcsecond, or better, positions, and hence reliable identifications, for the
XMM-Newton sources. The ACIS-I observations were arranged in a mosaic of four
30ksec pointings, covering almost all of the 15' radius XMM-Newton/ROSAT field.
We detect 214 Chandra sources above 5 sigma significance, to a limiting flux of
\~1.3e-15 erg/cm2/s (0.5-7 keV). Optical counterparts are derived from a Subaru
SuprimeCam image reaching to R~27. The very large majority of the Chandra
sources have an optical counterpart, with the distribution peaking at 23<R<24,
although 14 have no counterpart to R=27. The fraction of X-ray sources with no
identification brighter than R=27 is similar to that found in deeper Chandra
surveys. The majority of the identifications are with galaxies. As found in
other Chandra surveys, there is a very wide range of optical magnitude for
given X-ray flux, implying a range of emission mechanisms, and many sources
have high L_X/L_opt ratios, implying absorption at moderate redshift.
Comparison with the earlier ROSAT survey shows that the accuracy of the ROSAT
positions agrees very well with the predictions from simulations in McHardy et
al. (1998) and that the large majority of the identifications were correct
(abridged).


title:
Primordial Nucleosynthesis as a Test of the Friedmann Equation in the
  Early Universe

abstract:
  In the standard hot big bang model, the expansion of the early universe is
given by the Friedmann equation with an energy density dominated by
relativistic particles. Since in a variety of models this equation is altered,
we introduce modifications in the Friedmann equation and show that we can
constrain them using big bang nucleosynthesis data. When there is no
neutrino/antineutrino asymmetry these modifications are tightly bounded but in
presence of an asymmetry the bounds become much looser. As an illustration, we
apply our results to a model where the second and third families couple to
gravity differently than the first family (non-universal gravity).


title: The Nature of the UV/X-Ray Absorber in PG 2302+029

abstract:
  We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029.
This quasar has a rare system of ultra-high velocity (-56,000 km/s) UV
absorption lines that form in an outflow from the active nucleus (Jannuzi et
al. 2003). The Chandra data indicate that soft X-ray absorption is also
present. We perform a joint UV and X-ray analysis, using photoionization
calculations, to detemine the nature of the absorbing gas. The UV and X-ray
datasets were not obtained simultaneously. Nonetheless, our analysis suggests
that the X-ray absorption occurs at high velocities in the same general region
as the UV absorber. There are not enough constraints to rule out multi-zone
models. In fact, the distinct broad and narrow UV line profiles clearly
indicate that multiple zones are present. Our preferred estimates of the
ionization and total column density in the X-ray absorber (log U=1.6,
N_H=10^22.4 cm^-2) over predict the O VI 1032, 1038 absorption unless the X-ray
absorber is also outflowing at ~56,000 km/s, but they over predict the Ne VIII
770, 780 absorption at all velocities. If we assume that the X-ray absorbing
gas is outflowing at the same velocity of the UV-absorbing wind and that the
wind is radiatively accelerated, then the outflow must be launched at a radius
of < 10^15 cm from the central continuum source. The smallness of this radius
casts doubts on the assumption of radiative acceleration.


title:
The BeppoSAX High Energy Large Area Survey (HELLAS) - VI. The radio
  properties

abstract:
  We present results of a complete radio follow-up obtained with the VLA and
ATCA radio telescopes down to a 6 cm flux limit of about 0.3 mJy of all the 147
X-ray sources detected in the BeppoSAX HELLAS survey. We found 53 X-ray/radio
likely associations, corresponding to about one third of the X-ray sample.
Using the two point spectral index alpha_ro=0.35 we divided all the HELLAS
X-ray sources in radio quiet and radio loud. We have 26 sources classified as
radio-loud objects, corresponding to about 18% of the HELLAS sample. In
agreement with previous results, the identified radio-loud sources are
associated mainly with Type 1 AGNs with L(5-10 keV) > 10^44 erg/s, while all
the identified Type 2 AGNs and Emission Line Galaxies are radio quiet objects
with L(5-10 keV) < 10^44 erg/s. The analysis of the radio spectral index
suggests that Type 1 AGNs have a mean radio spectral index flatter than Type 2
AGNs and Emission Line Galaxies.


title:
New perspectives in physics and astrophysics from the theoretical
  understanding of Gamma-Ray Bursts

abstract:
  If due attention is given in formulating the basic equations for the
Gamma-Ray Burst (GRB) phenomenon and in performing the corresponding
quantitative analysis, GRBs open a main avenue of inquiring on totally new
physical and astrophysical regimes. This program is one of the greatest
computational efforts in physics and astrophysics and cannot be actuated using
shortcuts. A systematic approach has been highlighted in three paradigms: the
relative space-time transformation (RSTT) paradigm, the interpretation of the
burst structure (IBS) paradigm, the GRB-supernova time sequence (GSTS)
paradigm. In fundamental physics new regimes are explored: (1) the process of
energy extraction from black holes; (2) the quantum and general relativistic
effects of matter-antimatter creation near the black hole horizon; (3) the
physics of ultrarelativisitc shock waves with Lorentz gamma factor $\gamma >
100$. In astronomy and astrophysics also new regimes are explored: (i) the
occurrence of gravitational collapse to a black hole from a critical mass core
of mass $M\agt 10M_\odot$, which clearly differs from the values of the
critical mass encountered in the study of stars ``catalyzed at the endpoint of
thermonuclear evolution" (white dwarfs and neutron stars); (ii) the extremely
high efficiency of the spherical collapse to a black hole, where almost 99.99%
of the core mass collapses leaving negligible remnant; (iii) the necessity of
developing a fine tuning in the final phases of thermonuclear evolution of the
stars, both for the star collapsing to the black hole and the surrounding ones,
in order to explain the possible occurrence of the "induced gravitational
collapse". A new class of space missions to acquire information on such extreme
new regimes are urgently needed.


title:
Chandra and XMM-Newton observations of the first quasars: X-rays from
  the age of cosmic enlightenment

abstract:
  We report on Chandra and XMM-Newton observations of a sample of 13 quasars at
z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present
sample complements previous X-ray studies of z>4 quasars, in which the majority
of the objects are optically more luminous and at lower redshifts. All but two
of our quasars have been detected in the X-ray band, thus doubling the number
of z>4.8 X-ray detected quasars. The two non-detections are likely to be due to
a short exposure time and to the presence of intrinsic absorption. We confirm
and extend to the highest redshifts the presence of a correlation between
AB1450(1+z) magnitude and soft X-ray flux for z>4 quasars, and the presence of
a steeper optical-to-X-ray spectral energy distribution (parameterized by aox)
for high-luminosity, high-redshift quasars than for lower-luminosity,
lower-redshift quasars. The second effect is likely due to the known
anti-correlation between aox and rest-frame 2500 Angstrom luminosity, whose
significance is confirmed via partial correlation analysis. The joint ~2.5-36
keV rest-frame spectrum of the z>4.8 SDSS quasars observed thus far by Chandra
is well parameterized by a power-law with photon index Gamma=1.84+/-0.30; this
photon index is consistent with those of z~0-3 quasars and that obtained from
joint spectral fitting of z~4.1-4.5 optically luminous Palomar Digital Sky
Survey quasars. No evidence for widespread intrinsic X-ray absorption has been
found (Nh<4.0x10^{22} cm^{-2} on average at 90% confidence). We also obtained
Hobby-Eberly Telescope (HET) photometric observations for eight of our target
quasars. None of these shows significant (>30%) optical variability over the
time interval of a few years (in the observed frame) between the SDSS and HET
observations.


title:
Early-type Stars: Most Favorable Targets for Astrometrically Detectable
  Planets in the Habitable Zone

abstract:
  Early-type stars appear to be a difficult place to look for planets
astrometrically. First, they are relatively heavy, and for fixed planetary mass
the astrometric signal falls inversely as the stellar mass. Second, they are
relatively rare (and so tend to be more distant), and for fixed orbital
separation the astrometric signal falls inversely as the distance.
Nevertheless, because early-type stars are relatively more luminous, their
habitable zones are at larger semi-major axis. Since astrometric signal scales
directly as orbital size, this gives early-type stars a strong advantage, which
more than compensates for the other two factors. Using the Hipparcos catalog,
we show that early-type stars constitute the majority of viable targets for
astrometric searches for planets in the habitable zone. We contrast this
characteristic to transit searches, which are primarily sensitive to habitable
planets around late-type stars.


title:
Constraints on the equation of state of dark energy and the Hubble
  constant from stellar ages and the CMB

abstract:
  We place tight constraints on the redshift-averaged, effective value of the
equation of state of dark energy, w, using only the absolute ages of Galactic
stars and the observed position of the first peak in the angular power spectrum
of the CMB. We find w<-0.8 at the 68% confidence level. If we further consider
that w > -1, this finding suggests that within our uncertainties, dark energy
is indistinguishable from a classical vacuum energy term.
  We detect a correlation between the ages of the oldest galaxies and their
redshift. This opens up the possibility of measuring w(z) by computing the
relative ages of the oldest galaxies in the universe as a function of redshift,
dz/dt. We show that this is a realistic possibility by computing dz/dt at z~0
from SDSS galaxies and obtain an independent estimate for the Hubble constant,
H_0 = 69 \pm 12 km s-1 Mpc-1. The small number of galaxies considered at z>0.2
does not yield, currently, a precise determination of w(z), but shows that the
age--redshift relation is consistent with a Standard LCDM universe with $w=-1$.


title:
Atomic data from the Iron Project. LIII. Relativistic allowed and
  forbidden transition probabilities for Fe XVII

abstract:
  An extensive set of fine structure levels and corresponding transition
probabilities for allowed and forbidden transitions in Fe XVII is presented. A
total of 490 bound energy levels of Fe XVII of total angular momenta 0 <= J <=
7 of even and odd parities with 2 <= n <= 10, 0 <= l <= 8, 0 <= L <= 8, and
singlet and triplet multiplicities, are obtained. They translate to over 2.6 x
10^4 allowed (E1) transitions that are of dipole and intercombination type, and
about 3000 forbidden transitions that include electric quadrupole (E2),
magnetic dipole (M1), electric octopole (E3), and magnetic quadrupole (M2) type
representing the most detailed calculations to date for the ion. Oscillator
strengths f, line strengths S, and coefficients A of spontaneous emission for
the E1 type transitions are obtained in the relativistic Breit-Pauli R-matrix
approximation. A valus for the forbidden transitions are obtained from atomic
structure calculations using codes SUPERSTRUCTURE and GRASP. The energy levels
are identified in spectroscopic notation with the help of a newly developed
level identification algorithm. Nearly all 52 spectroscopically observed levels
have been identified, their binding energies agreeing within 1% with our
calculation. Computed transition probabilities are compared with other
calculations and measurement. The effect of 2-body magnetic terms and other
interactions is discussed. Present data set enhances by more than an order of
magnitude the heretofore available data for the transition probabilities of Fe
XVII.


title:
FS Aur - a new class of Cataclysmic Variables or the missing link
  between Intermediate Polars and SW Sex objects?

abstract:
  FS Aur is a known dwarf nova with an orbital period of about 85.7 minutes. It
has been assumed to be a member of the SU UMa subclass of cataclysmic variables
(CVs), but previous searches for superhumps and superoutburst have been
unsuccessful. We conducted a series of photometric and spectroscopic
observations of FS Aur during quiescence. We confirmed its short orbital period
from radial velocity measurements. However, the long-term photometry revealed
an unexpected result: the system also shows a distinct 0.24 mag modulation in
the BVR photometric bands with a period of 205.5 min, which is 2.4 times longer
than the orbital period. We discuss various possible causes for such a peculiar
behavior.


title: On the loss of telemetry data in full-sky surveys from space

abstract:
  In this paper we discuss the issue of loosing telemetry (TM) data due to
different reasons (e.g. spacecraft-ground transmissions) while performing a
full-sky survey with space-borne instrumentation. This is a particularly
important issue considering the current and future space missions (like Planck
from ESA and WMAP from NASA) operating from an orbit far from Earth with short
periods of visibility from ground stations. We consider, as a working case, the
Low Frequency Instrument (LFI) on-board the Planck satellite albeit the
approach developed here can be easily applied to any kind of experiment that
makes use of an observing (scanning) strategy which assumes repeated pointings
of the same region of the sky on different time scales. The issue is addressed
by means of a Monte Carlo approach. Our analysis clearly shows that, under
quite general conditions, it is better to cover the sky more times with a lower
fraction of TM retained than less times with a higher guaranteed TM fraction.
In the case of Planck, an extension of mission time to allow a third sky
coverage with 95% of the total TM guaranteed provides a significant reduction
of the probability to loose scientific information with respect to an increase
of the total guaranteed TM to 98% with the two nominal sky coverages.


title: High NH2D/NH3 ratios in protostellar cores

abstract:
  Observations of low mass protostars which probe small enough size scales to
be within likely CO depletion regions show the highest [NH2D]/[NH3] ratios yet
measured, of 4--33%. These molecular D/H ratios are higher than those measured
on larger scales, showing that deuterium fractionation increases towards
protostellar cores. As in cold clouds, such high ratios can be produced by
gas-phase ion-molecule chemistry in the presence of depletion. Grain surface
chemistry is less likely to explain the deuterium enhancement, as it would
require higher fractionation in ices than current models predict. The link
between accretion, depletion and high molecular deuterium fractionation is
strongly supported.


title: Stellar coronal astronomy - a review

abstract:
  Coronal astronomy is by now a fairly mature discipline, with a quarter
century having gone by since the detection of the first stellar X-ray coronal
source (Capella), and having benefitted from a series of major orbiting
observing facilities. Several observational characteristics of coronal X-ray
and EUV emission have been solidly established through extensive observations,
and are by now common, almost text-book, knowledge. At the same time the
implications of coronal astronomy for broader astrophysical questions (e.g.
Galactic structure, stellar formation, stellar structure, etc.) have become
appreciated. The interpretation of stellar coronal properties is however still
often open to debate, and will need qualitatively new observational data to
book further progress. In the present review we try to recapitulate our view on
the status of the field at the beginning of a new era, in which the high
sensitivity and the high spectral resolution provided by Chandra and XMM-Newton
will address new questions which were not accessible before.


title: Dust Formation In Early Galaxies

abstract:
  We investigate the sources and amount of dust in early galaxies. We discuss
dust nucleation in stellar atmospheres using published extended atmosphere
models, stellar evolution tracks and nucleation conditions and conclude that
the (TPAGB) phase of intermediate mass stars is likely to be the most promising
site for dust formation in stellar winds. The implications of chemical
evolution models for high redshift galaxies are investigated and we show there
is no difficulty in producing dusty galaxies at redshifts above 5 if supernovae
are a dominant source of interstellar dust. If dust does not condense
efficiently in SNe then significant dust masses can only be generated at by
galaxies with a high star formation efficiency. We find the visual optical
depth for individual star forming clouds can reach values greater than 1 at
very low metallicity (1/100 solar) provided that the mass-radius exponent of
molecular clouds is less than two. Most of the radiation from star formation
will emerge at IR wavelengths in the early universe provided that dust is
present. The (patchy) visual optical depth through a typical early galaxy will
however, remain less than 1 on average until a metallicity of 1/10 solar is
reached.


title:
On the Angular Correlation Function of SZ Clusters : Extracting
  cosmological information from a 2D catalog

abstract:
  We discuss the angular correlation function of Sunyaev-Zel'dovich
(SZ)-detected galaxy clusters as a cosmological probe. As a projection of the
real-space cluster correlation function, the angular function samples the
underlying SZ catalog redshift distribution. It offers a way to study cosmology
and cluster evolution directly with the two-dimensional catalog, even before
extensive follow-up observations, thereby facilitating the immediate scientific
return from SZ surveys. As a simple illustration of the information content of
the angular function, we examine its dependence on the parameter pair Om_m,
sigma_8 in flat cosmologies. We discuss sources of modeling uncertainty and
consider application to the future Planck SZ catalog, showing how these two
parameters and the normalization of the SZ flux-mass relation can be
simultaneously found when the local X-ray cluster abundance constraint is
included.


title: Detection of strongly processed ice in the central starburst of NGC4945

abstract:
  The composition of ice grains provides an important tool for the study of the
molecular environment of star forming regions. Using ISAAC at the VLT to obtain
spectra around 4.65 microns we have detected for the first time `XCN' and CO
ice in an extragalactic environment: the nuclear region of the nearby dusty
starburst/AGN galaxy NGC4945. The profile of the solid CO band reveals the
importance of thermal processing of the ice while the prominence of the XCN
band attests to the importance of energetic processing of the ice by FUV
radiation and/or energetic particles. In analogy to the processing of ices by
embedded protostars in our Galaxy, we attribute the processing of the ices in
the center of NGC4945 to ongoing massive star formation. Our M-band spectrum
also shows strong HI Pfund-beta and H2 0-0 S(9) line emission and gas phase CO
absorption lines. The HI, H2, PAH, gas phase CO and the ices seem to be
embedded in a rotating molecular disk which is undergoing vigorous star
formation. Recently, strong OCN- absorption has been detected in the spectrum
of the Galactic center star GC:IRS19. The most likely environment for the OCN-
absorption is the strongly UV-exposed GC molecular ring. The presence of
processed ice in the center of NGC4945 and our Galactic center leads us to
believe that processed ice may be a common characteristic of dense molecular
material in star forming galactic nuclei.


title: Baryon Loading of Gamma Ray Bursts by Pick-up Neutrons

abstract:
  It is proposed that the baryons in gamma ray burst (GRB) fireballs originate
as "pick-up" neutrons that leak in sideways from surrounding baryonic matter
and convert to protons in a collision avalanche. The asymptotic Lorentz factor
is estimated, and, in the absence of collimation, is shown to be angle
dependent. Reasonable agreement is obtained with existing limits on the GRB
baryonic component. The charged decay and collision products of the neutrons
become ultrarelativistic immediately, and a UHE neutrino burst is produced with
an efficiency that can exceed 0.5. Other signatures may include lithium,
beryllium and/or boron lines in the supernova remnants associated with GRB's
and high polarization of the gamma rays.


title:
Castor A and Castor B resolved in a simultaneous Chandra and XMM-Newton
  observation

abstract:
  We present a simultaneous Chandra and XMM-Newton observation of the Castor
sextett, focusing on Castor A and Castor B, two spectroscopic binaries with
early-type primaries. Of the present day X-ray instruments only Chandra can
isolate the X-ray lightcurves and spectra of A and B. We compare the Chandra
observation with XMM-Newton data obtained simultaneously. Albeit not able to
resolve Castor A and Castor B from each other, the higher sensitivity of
XMM-Newton allows for a quantitative analysis of their combined high-resolution
spectrum. He-like line triplets are used to examine the temperature and the
density in the corona of Castor AB. The temporal variability of Castor AB is
studied using data collected with the European Photon Imaging Camera onboard
XMM-Newton. Strong flare activity is observed, and combining the data acquired
simultaneously with Chandra and XMM-Newton each flare can be assigned to its
host. Our comparison with the conditions of the coronal plasma of other stars
shows that Castor AB behave like typical late-type coronal X-ray emitters
supporting the common notion that the late-type secondaries within each
spectroscopic binary are the sites of the X-ray production.


title: Cosmological constraints from the CMB and Ly-alpha forest revisited

abstract:
  The WMAP team has recently highlighted the usefulness of combining the
Ly-alpha forest constraints with those from the cosmic microwave background
(CMB). This combination is particularly powerful as a probe of the primordial
shape of the power spectrum. Converting between the Ly-alpha forest
observations and the linear mass power spectrum requires a careful treatment of
nuisance parameters and modeling with cosmological simulations. We point out
several issues which lead to an expansion of the errors, the two most important
being the range of cosmological parameters explored in simulations and the
treatment of the mean transmitted flux constraints. We employ a likelihood
calculator for the current Ly-alpha data set based on an extensive
6-dimensional grid of simulations. We show that the current uncertainties in
the mean transmission and the flux power spectrum define a degeneracy line in
the amplitude-slope plane. The CMB degeneracy due to the primordial power
spectrum shape follows a similar relation in this plane. This weakens the
statistical significance of the primordial power spectrum shape constraints
based on combined CMB+Ly-alpha forest analysis. Using the current data the
simplest n=1 scale invariant model with dn/dln k=0 and no tensors has a Delta
chi^2=4 compared to the best fitting model in which these 3 parameters are
free. Current data therefore do not require relaxing these parameters to
improve the fit.


title:
The Far-Infrared Spectral Energy Distributions of X-ray-selected Active
  Galaxies

abstract:
  [Abridged] We present ISO far-infrared (IR) observations of 21 hard X-ray
selected AGN from the HEAO-1 A2 sample. We compare the far-IR to X-ray spectral
energy distributions (SEDs) of this sample with various radio and optically
selected AGN samples. The hard-X-ray selected sample shows a wider range of
optical/UV shapes extending to redder near-IR colors. The bluer objects are
Seyfert 1s, while the redder AGN are mostly intermediate or type 2 Seyferts.
This is consistent with a modified unification model in which the amount of
obscuring material increases with viewing angle and may be clumpy. Such a
scenario, already suggested by differing optical/near-IR spectroscopic and
X-ray AGN classifications, allows for different amounts of obscuration of the
continuum emission in different wavebands and of the broad emission line region
which results in a mixture of behaviors for AGN with similar optical emission
line classifications. The resulting limits on the column density of obscuring
material through which we are viewing the redder AGN are 100 times lower than
for the standard optically thick torus models. The resulting decrease in
optical depth of the obscuring material allows the AGN to heat more dust at
larger radial distances. We show that an AGN-heated, flared, dusty disk with
mass 10^9 solar and size of few hundred pc is able to generate optical-far-IR
SEDs which reproduce the wide range of SEDs present in our sample with no need
for an additional starburst component to generate the long-wavelength, cooler
part of the IR continuum.


title:
Effects of Wandering on the Coalescence of Black Hole Binaries in
  Galactic Centers

abstract:
  We examine whether massive binary black holes in spherically symmetric bulges
of galaxies can achieve coalescence through the emission of gravitational
radiation under the action of stellar dynamical processes alone. In particular,
we address the importance of the Brownian motion of a binary's center-of-mass
to its continued interaction with stellar orbits that allows it to keep
hardening: the restoring force holding the binary at the center decreases as it
depletes the central stellar density, causing the amplitude of wandering to
increase. We use an analytical model and N-body simulations to calculate the
time required to reach the gravitational-radiation dominated stage. We find
that a substantial fraction of all massive binaries in galaxies can coalesce
within a Hubble time.


title:
Formation and Evolution of Supermassive Black Holes in Galactic Centers:
  Observational Constraints

abstract:
  Deep X-ray surveys have shown that the cosmic X-ray background (XRB) is
largely due to the accretion onto supermassive black holes, integrated over the
cosmic time. These surveys have resolved more than 80% of the 0.1-10 keV X-ray
background into discrete sources. Optical spectroscopic identifications show
that the sources producing the bulk of the X-ray background are a mixture of
obscured (type-1) and unobscured (type-2) AGNs, as predicted by the XRB
population synthesis models. A class of highly luminous type-2 AGN, so called
QSO-2s, has been detected in the deepest Chandra and XMM-Newton surveys. The
new Chandra AGN redshift distribution peaks at much lower redshifts (z~0.7)
than that based on ROSAT data, indicating that Seyfert galaxies peak at
significantly lower redshifts than QSOs.


title: Cooling and heating the ICM in hydrodynamical simulations

abstract:
  We discuss Tree+SPH simulations of galaxy clusters and groups, aimed at
studying the effect of cooling and non-gravitational heating on observable
properties of the ICM. We simulate at high resolution four halos,with masses in
the range (0.2-4)10^{14}M_sol. We discuss the effects of using different SPH
implementations and show that high resolution is mandatory to correctly follow
the cooling pattern of the ICM. All of our heating schemes which correctly
reproduce the X-ray scaling properties of clusters and groups do not succeed in
reducing the fraction of collapsed gas below a level of 20 (30) per cent at the
cluster (group) scale. Finally, gas compression in cooling cluster regions
causes an increase of the temperature and a steepening of the temperature
profiles, independent of the presence of non-gravitational heating processes.
This is inconsistent with recent observational evidence for a decrease of gas
temperature towards the center of relaxed clusters. Provided these
discrepancies persist even for a more refined modeling of energy feedback, they
may indicate that some basic physical process is still missing in
hydrodynamical simulations.


title: Location of H2O maser in the double-nuclei system of NGC6240

abstract:
  We performed VLA observations of the 22 GHz H2O maser emission in the merging
galaxy NGC6240, which hosts the well-known double active nuclei. In a previous
paper, we reported on the first solid detection of the H2O maser emission in
2001. After two abortive attempts due to the weakness and probable variability
of the emission, the maser was detected with the VLA in June 2002. The emission
is unresolved at ~ 0.3 arcsecond and coincides with the southern 22 GHz
continuum peak to ~ 0.007 arcsecond (~ 3 pc: D = 97 Mpc). The detection of the
maser in the southern nucleus indicates that nuclear activity of the
galaxy,which is significant in X-ray and far-infrared (FIR) bands, lies mainly
in the southern nucleus, and the nucleus without a high brightness peak could
be explained by thick dust emitting FIR radiation. We favour the idea that the
maser in NGC6240 is associated with the AGN-activity.


title: Statistical Synthesis Models

abstract:
  In this contribution we evaluate the minimal cluster mass for which the
effects of an incomplete sampling of the Initial Mass Function (IMF) cannot be
neglected. This minimal cluster mass corresponds to the situation in which the
integrated luminosity of the cluster modeled equals the luminosity of the most
luminous individual star included in the model, and it takes values between
3x10^2 and 6x10^5 Mo depending on the age and the observed band. We show
different examples for young (t < 10 Myr) and old (t up to 10 Gyr) stellar
populations. We also make here a first release of the spectral energy
distribution (SED) from 160 mic. (1.8x10^12 Hz) to 25 keV (6.0x10^18 Hz) for
star-forming regions with ages between 0.1 and 10 Myr, and metallicities
between Z=0.001 and Z=0.040. The SEDs are available at our WWW server and
include the corresponding quantities for the evaluation of sampling effects.
These SEDs can be directly used to obtain colors (including the X-rays ones),
as input of photoionization codes, or for chi^2 fitting with observed data
taking into account the intrinsic uncertainty of the models due to the IMF
sampling.


title: Interacting Geodesics: Binary Systems around a Black Hole

abstract:
  We present a novel method to study interacting orbits in a fixed mean
gravitational field associated with a solution of the Einstein field equations.
The idea is to consider the Newton gravity among the orbiting particles in a
geometry given by the main source. We apply the technique in the of study two
and three self-gravitating particles moving around a black hole, i.e., in a
Schwarzschild geometry. We also compare with the equivalent Newtonian problem
and noted differences in the structural stability, e.g., binary systems were
found only in the general relativistic approach.


title:
Diffuse X-Ray Emission from the Quiescent Superbubble M17, the Omega
  Nebula

abstract:
  The emission nebula M17 contains a young ~1 Myr-old open cluster; the winds
from the OB stars of this cluster have blown a superbubble around the cluster.
ROSAT observations of M17 detected diffuse X-ray emission peaking at the
cluster and filling the superbubble interior. The young age of the cluster
suggests that no supernovae have yet occurred in M17; therefore, it provides a
rare opportunity to study hot gas energized solely by shocked stellar winds in
a quiescent superbubble. We have analyzed the diffuse X-ray emission from M17,
and compared the observed X-ray luminosity of ~2.5*10^33 ergs/s and the hot gas
temperature of ~8.5*10^6 K and mass of ~1 M_Sun to model predictions. We find
that bubble models with heat conduction overpredict the X-ray luminosity by two
orders of magnitude; the strong magnetic fields in M17, as measured from HI
Zeeman observations, have most likely inhibited heat conduction and associated
mass evaporation. Bubble models without heat conduction can explain the X-ray
properties of M17, but only if cold nebular gas can be dynamically mixed into
the hot bubble interior and the stellar winds are clumpy with mass-loss rates
reduced by a factor of >=3. Future models of the M17 superbubble must take into
account the large-scale density gradient, small-scale clumpiness, and strong
magnetic field in the ambient interstellar medium.


title: Infant Galaxy Clusters at Low Redshifts?

abstract:
  The population and population composition of galaxies in galaxy clusters at
present reflect the mass of the clusters and the mass growth of the galaxies in
the past. We investigate them for six clusters. We show that galaxies in
massive clusters stopped growing at redshifts of ~4. Moreover, we find that
some small galaxy clusters (groups) have too many massive galaxies for their
apparent masses. One possibility is that these groups are much more massive and
in a phase just before virialization. If this is the case, they should be
called `infant galaxy clusters' that will be matured clusters in the dynamical
time-scale (~10^9 yrs).


title: X-ray spectral evolution of low-mass X-ray binary GX 349+2

abstract:
  We present the results of a systematic investigation of spectral evolution in
the Z source GX 349+2, using data obtained during 1998 with
Proportional-Counter-Array (PCA) on-board the RXTE satellite. The source traced
a extended normal branch (NB) and flaring branch (FB) in the color-color
diagram (CD) and hardness-intensity diagram (HID) during these observations.
The spectra at different positions of Z-track were best fitted by a model
consisting of a disk blackbody and a comptonized spectrum. A broad (gaussian)
iron line at $\sim 6.7$ keV is also required to improve the fit. The spectral
parameters showed a systematic and significant variation with the position
along the Z-track. The evolution in spectral parameters is discussed in the
view of increasing mass accretion rate scenario, proposed to explain the motion
of Z sources in the CD and HID.


title:
The VLT-UVES survey for molecular hydrogen in high-redshift damped
  Lyman-alpha systems

abstract:
  We have searched for molecular hydrogen in damped Lyman-alpha (DLA) and
sub-DLA systems at z>1.8 using UVES at the VLT. Out of the 33 systems in our
sample, 8 have firm and 2 have tentative detections of associated H2 absorption
lines. Considering that 3 detections were already known from past searches, H2
is detected in 13 to 20 percent of the newly-surveyed systems. We report new
detections of molecular hydrogen at z=2.087 and 2.595 toward, respectively, Q
1444+014 and Q 0405-443, and also reanalyse the system at z=3.025 toward Q
0347-383. We find that there is a correlation between metallicity and depletion
factor in both our sample and also the global population of DLA systems (60
systems in total). The DLA and sub-DLA systems where H2 is detected are usually
amongst those having the highest metallicities and the largest depletion
factors. Moreover, the individual components where H2 is detected have
depletion factors systematically larger than other components in the profiles.
In two different systems, one of the H2-detected components even has
[Zn/Fe]>=1.4. These are the largest depletion factors ever seen in DLA systems.
All this clearly demonstrates the presence of dust in a large fraction of the
DLA systems. The mean H2 molecular fraction is generally small in DLA systems
and similar to what is observed in the Magellanic Clouds. From 58 to 75 percent
of the DLA systems have log f<-6. This can be explained if the formation rate
of H2 onto dust grains is reduced in those systems, probably because the gas is
warm (T>1000 K) and/or the ionizing flux is enhanced relative to what is
observed in our Galaxy.


title:
Electron-cyclotron maser emission from white-dwarf pairs and white-dwarf
  planetary systems

abstract:
  By analogy to Jovian radio emissions powered by the electromagnetic
interaction between Jupiter and its moons, we propose that close
magnetic-nonmagnetic white-dwarf pairs and white-dwarf planetary systems are
strong radio sources. A simple model is developed to predict the flux densities
of radio emission generated by a loss-cone-driven electron-cyclotron maser. The
radio emission from these systems has high brightness temperatures, is highly
polarized, and varies on a periodic cycle following the orbital rotation.
Masers from magnetic-nonmagnetic white-dwarf pairs, with orbital periods <10
min, are expected to be detectable over a wide range of radio frequencies.
Terrestrial planets in close orbits about magnetic white dwarfs, with orbital
periods $\la 30$ hr, can also produce detectable radio emission, thus providing
a means to identify Earth-sized extrasolar planets.


title:
Gravitational Waves from Phase-Transition Induced Collapses of Neutron
  Stars

abstract:
  We study the gravitational wave signals emitted from phase-transition induced
collapses of rapidly rotating neutron stars to strange stars by performing 3D
numerical simulations. Our preliminary results suggest that the complete
conversion of neutron stars to strange stars would occur within a fraction of
millisecond. We also find that the gravitational waves generated from the
collapse process may be detectable by the advanced LIGO for reasonable source
distance. In addition, the study such gravitational wave signals would put
useful constraint on the parameters of QCD.


title: Observations of fourteen pulsar glitches

abstract:
  About 76 glitches in 25 pulsars have been reported to date. Most glitches are
`giant', with fractional increases of frequency dnu_0/nu_0 ~ 10^{-6}. 25
glitches were analysed and presented by Shemar & Lyne (1996) who detected them
mainly at Jodrell Bank during the monitoring of a sample of 279 pulsars in a
regular timing programme up to MJD 49500. This paper is a continuation of their
work up to MJD 50500. We present the detection and analysis of a further 14
glitches in 9 pulsars, 6 of which have glitched for the first time since
monitoring had started. Eleven of these glitches are small (dnu_0/nu_0 ~
10^{-9}) and below the completeness threshold of Shemar and Lyne(1996). We
report a giant glitch in PSR B1930+22, the second largest reported hitherto,
with a dnu_0/nu_0 = 4.5 x 10^{-6}. We also report four recent glitches in PSR
B1737$-$30 which continues to exhibit frequent glitches. Few of these pulsars
show any recovery after the glitch.


title: Moon and Sun shadowing effect in the MACRO detector

abstract:
  Using data collected by the MACRO experiment from 1989 to the end of its
operations in 2000, we have studied in the underground muon flux the shadowing
effects due to both the Moon and the Sun. We have observed the Moon shadowing
effect with a significance of 6.5 sigma and the Sun shadowing effect with a
significance of 4.3 sigma. The observed displacement of the Sun shadow, due to
the configurations of the solar and interplanetary magnetic fields, has been
used to quote the antiproton/proton flux limits for primaries of about 20 TeV
energy.


title: Semi-linear gravitational lens inversion

abstract:
  We describe a new method for analyzing gravitational lens images, for the
case where the source light distribution is pixelized. The method is suitable
for high resolution, high S/N data of a multiply-imaged extended source. For a
given mass distribution, we show that the step of inverting the image to obtain
the deconvolved pixelized source light distribution, and the uncertainties, is
a linear one. This means that the only parameters of the non-linear problem are
those required to model the mass distribution. This greatly simplifies the
search for a min.-chi^2 fit to the data and speeds up the inversion. The method
is extended in a straightforward way to include linear regularization. We apply
the method to simulated Einstein ring images and demonstrate the effectiveness
of the inversion for both the unregularized and regularized cases.


title: An X-ray Nebula Associated with the Millisecond Pulsar B1957+20

abstract:
  We have detected an x-ray nebula around the binary millisecond pulsar
B1957+20. A narrow tail, corresponding to the shocked pulsar wind, is seen
interior to the known H-alpha bow shock and proves the long-held assumption
that the rotational energy of millisecond pulsars is dissipated through
relativistic winds. Unresolved x-ray emission likely represents the shock where
the winds of the pulsar and its companion collide. This emission indicates that
the efficiency with which relativistic particles are accelerated in the post
shock flow is similar to that for young pulsars, despite the shock proximity
and much weaker surface magnetic field of this millisecond pulsar.


title: Neutrinos in Physics and Astrophysics

abstract:
  The observed flavor oscillations of solar and atmospheric neutrinos determine
several elements of the leptonic mixing matrix, but leave open the small mixing
angle Theta_13, a possible CP-violating phase, the mass ordering, the absolute
mass scale m_nu, and the Dirac vs. Majorana property. Progress will be made by
long-baseline, tritium endpoint, and 2-beta decay experiments. The best
constraint on m_nu obtains from cosmological precision observables, implying
that neutrinos contribute very little to the dark matter. However, massive
Majorana neutrinos may well be responsible for ordinary matter by virtue of the
leptogenesis mechanism for creating the baryon asymmetry of the universe. In
future, neutrinos could play an important role as astrophysical messengers if
point sources are discovered in high-energy neutrino telescopes. In the
low-energy range, a high-statistics observation of a galactic supernova would
allow one to observe directly the dynamics of stellar collapse and perhaps to
discriminate between certain mixing scenarios. An observation of the relic
neutrinos from all past supernovae has come within reach.


title: Stephan's Quintet: The X-ray Anatomy of a Multiple Galaxy Collision

abstract:
  Chandra observations of the compact galaxy group known as Stephan's Quintet
(SQ) are presented. The major morphological features that were discovered with
the ROSAT HRI are now imaged with higher resolution and S/N. The large scale
shock (1.5', ~40kpc if at 85 Mpc) is resolved into a narrow NS feature embedded
in more extended diffuse emission (D>=3'). The NS structure is somewhat clumpy,
more sharply bounded on the W side and prominent only in the soft band
(energies below ~2 keV). Its observational properties are best explained as a
shock produced by a high velocity encounter between NGC7318b, a ``new
intruder'', and the intergalactic medium in SQ. The shock conditions near the
high speed intruder suggest that a bow shock is propagating into a pre-existing
HI cloud and heating the gas to a temperature of ~0.5 keV. The low temperature
in the shock is a problem unless we postulate an oblique shock. One member,
NGC7319, hosts a Seyfert 2 nucleus, with an intrinsic luminosity Lx=10^43
erg/s, embedded in a region of more diffuse emission with 10'' radius extent.
The nuclear spectrum can be modeled with a strongly absorbed power-law typical
of this class of sources. Several additional compact sources are detected
including three in foreground NGC7320. Some of these sources are very luminous
and could be related to the ultraluminous X-ray sources found in nearby
galaxies.


title: Absolute Lineshifts - A new diagnostic for stellar hydrodynamics

abstract:
  For hydrodynamic model atmospheres, absolute lineshifts are becoming an
observable diagnostic tool beyond the classical ones of line-strength, -width,
-shape, and -asymmetry. This is the wavelength displacement of different types
of spectral lines away from the positions naively expected from the Doppler
shift caused by stellar radial motion. Caused mainly by correlated velocity and
brightness patterns in granular convection, such absolute lineshifts could in
the past be studied only for the Sun (since the relative Sun-Earth motion, and
the ensuing Doppler shift is known). For other stars, this is now becoming
possible thanks to three separate developments: (a) Astrometric determination
of stellar radial motion; (b) High-resolution spectrometers with accurate
wavelength calibration, and (c) Accurate laboratory wavelengths for several
atomic species. Absolute lineshifts offer a tool to segregate various 2- and
3-dimensional models, and to identify non-LTE effects in line formation.


title: Absolute Wavelength Shifts - A new diagnostic for rapidly rotating stars

abstract:
  Accuracies reached in space astrometry now permit the accurate determination
of astrometric radial velocities, without any use of spectroscopy. Knowing this
true stellar motion, spectral shifts intrinsic to stellar atmospheres can be
identified, for instance gravitational redshifts and those caused by velocity
fields on stellar surfaces. The astrometric accuracy is independent of any
spectral complexity, such as the smeared-out line profiles of rapidly rotating
stars. Besides a better determination of stellar velocities, this permits more
precise studies of atmospheric dynamics, such as possible modifications of
stellar surface convection (granulation) by rotation-induced forces, as well as
a potential for observing meridional flows across stellar surfaces.


title:
Solar Turbulence and Magnetism Studied Within a Rotating Convective
  Spherical Shell

abstract:
  We discuss recent advances made in modelling the complex magnetohydrodynamics
of the Sun using our anelastic spherical harmonics (ASH) code. We have
conducted extensive 3--D simulations of compressible convection in rotating
spherical shells with and without magnetic fields, to study the coupling
between global-scale convection and rotation in seeking to understand how the
solar differential rotation is established and maintained. Such simulations
capable of studying fairly turbulent convection have been enabled by massively
parallel supercomputers. The resulting convection within domains that capture a
good fraction of the bulk of the convection zone is highly time dependent and
intricate, and is dominated by intermittent upflows and networks of strong
downflows. A high degree of coherent structures involving downflowing plumes
can be embedded in otherwise chaotic flow fields. These vortical structures
play a significant role in yielding Reynolds stresses that serve to
redistribute angular momentum, leading to differential rotation profiles with
pole to equator contrasts of about 30% in angular velocity $\Omega$ and some
constancy along radial line at mid latitudes, thereby making good contact with
deductions from helioseismology. When a magnetic field is introduced, a dynamo
regime can be found that does not destroy the strong differential rotation
achieved in pure hydrodynamics cases. The magnetic fields are found to
concentrate around the downflowing networks and to have significant north-south
asymmetry and helicity.


title:
Statistical mechanics and phase diagrams of rotating self-gravitating
  fermions

abstract:
  We compute statistical equilibrium states of rotating self-gravitating
systems enclosed within a box by maximizing the Fermi-Dirac entropy at fixed
mass, energy and angular momentum. We increase the rotation up to the Keplerian
limit and describe the flattening of the configuration until mass shedding
occurs. At the maximum rotation, the system develops a cusp at the equator. We
draw the equilibrium phase diagram of the rotating self-gravitating Fermi gas
and discuss the structure of the caloric curve as a function of degeneracy
parameter and angular velocity. We argue that systems described by the
Fermi-Dirac distribution in phase space do not bifurcate to non-axisymmetric
structures, in continuity with the case of polytropes with index n>0.808 (the
Fermi gas at T=0 corresponds to n=3/2). This contrasts with the study of
Votyakov et al. (2002) who consider a Fermi-Dirac distribution in configuration
space and find ``double star'' structures (their model at T=0 corresponds to
n=0). We also discuss the influence of rotation on the onset of the
gravothermal catastrophe for globular clusters. On general grounds, we complete
previous investigations concerning the nature of phase transitions in
self-gravitating systems. We emphasize the inequivalence of statistical
ensembles regarding the formation of binaries (or low-mass condensates) in the
microcanonical ensemble and Dirac peaks (or massive condensates) in the
canonical ensemble. We also describe an hysteretic cycle between the gaseous
phase and the condensed phase that are connected by a ``collapse'' or an
``explosion''. This notion of hysteresis in self-gravitating systems is new.


title:
Eclipsing binaries in the Magellanic Clouds. uvby CCD light curves and
  photometric analyses for HV982 (LMC), HV12578 (LMC), HV1433 (SMC), and
  HV11284 (SMC)

abstract:
  We present new accurate CCD uvby light curves for the LMC eclipsing binaries
HV982 and HV12578, and for the SMC systems HV1433 and HV11284 obtained at the
Danish 1.5m telescope at ESO, La Silla. The light curves were derived from
DoPHOT photometry, and typical accuracies are between 0.007 and 0.012 mag per
point. Standard uvby indices have also been established for each binary,
primarily for determination of interstellar reddening and absorption. For HV982
and HV12578, accurate photometric elements have been established. Both systems
consist of two detached components of comparable sizes in an eccentric orbit.
Adopting the spectroscopic elements given by Fitzpatrick et al. 2002 for HV982,
we derive absolute dimensions of its components which agree well with their
results. A distance modulus of V_0-M_V = 18.63 +/- 0.08 is obtained,
corresponding to a distance of 52.6 +/- 2.0 kpc, which is in formal agreement
with (although slightly larger than) their determination. HV1433 and HV11284
both consist of two rather close, deformed and quite different stars. As the
mass ratios between the components (and their rotation rates) are not known,
definitive photometric elements can not yet be obtained, but we present a
sample of possible photometric solutions. In a series of forthcoming papers we
will combine our uvby observations with high-dispersion spectra from the UVES
spectrograph on the ESO Very Large Telescope (VLT) and present absolute
dimensions, chemical abundances and distances for selected LMC and SMC systems,
including HV12578 and refined results for HV982.


title: Shape Statistics of Sloan Digital Survey superclusters

abstract:
  We study the supercluster shape properties of the recently compiled SDSS
cluster catalog using an approach based on differential geometry. We detect
superclusters by applying the percolation algorithm to observed cluster
populations, extended out to $z_{\rm max}\leq 0.23$ in order to avoid selection
biases. We utilize a set of shapefinders in order to study the morphological
features of superclusters with $\geq 8$ cluster members and find that
filamentary morphology is the dominant supercluster shape feature, in agreement
with previous studies.


title: WMAP data and the curvature of space

abstract:
  Inter alia, the high precision WMAP data on Cosmic Microwave Background
Radiation marginally indicate that the universe has positively curved (and
hence spherical) spatial sections. In this paper, we take this data seriously
and consider some of the consequences for the background dynamics. In
particular, we show that this implies a limit to the number of e-foldings that
could have taken place in the inflationary epoch; however this limit is
consistent with some inflationary models that solve all the usual cosmological
problems and are consistent with standard structure formation theory.


title:
Looking Deep Within an A-type Star: Core Convection Under the Influence
  of Rotation

abstract:
  The advent of massively parallel supercomputing has begun to permit explicit
3--D simulations of turbulent convection occurring within the cores of
early-type main sequence stars. Such studies should complement the stellar
structure and evolution efforts that have so far largely employed 1--D nonlocal
mixing length descriptions for the transport, mixing and overshooting achieved
by core convection. We have turned to A-type stars as representative of many of
the dynamical challenges raised by core convection within rotating stars. The
differential rotation and meridional circulations achieved deep within the star
by the convection, the likelihood of sustained magnetic dynamo action there,
and the bringing of fresh fuel into the core by overshooting motions, thereby
influencing main sequence lifetimes, all constitute interesting dynamical
questions that require detailed modelling of global-scale convection. Using our
anelastic spherical harmonic (ASH) code tested on the solar differential
rotation problem, we have conducted a series of 3--D spherical domain
simulations that deal with a simplified description of the central regions of
rotating A-type stars, i.e a convectively unstable core is surrounded by a
stable radiative envelope. A sequence of 3--D simulations are used to assess
the properties of the convection (its global patterns, differential rotation,
meridional circulations, extent and latitudinal variation of the overshooting)
as transitions are made between laminar and turbulent states by changing the
effective diffusivities, rotation rates, and subadiabaticity of the radiative
exterior. We report on the properties deduced from these models for both the
extent of penetration and the profile of rotation sustained by the convection.


title: The K20 survey. V The evolution of the near-IR Luminosity Function

abstract:
  We present the galaxy rest-frame near-IR Luminosity Function (LF) and its
cosmic evolution to z=1.5 based on a spectroscopic survey of a magnitude
limited sample of galaxies with Ks<20 (the K20 survey, Cimatti et al. 2002b).
The LFs have been derived in the rest-frame J and Ks bands using 3 z bins
(z_mean= 0.5, 1, 1.5) and compared to the local near-IR LF. The faint-end of
the LFs is consistent with the local estimates, with no evidence for a change
either in the slope or normalization up to z<1.3. Viceversa, the density of
luminous galaxies (M_Ks-5logh_70<-25.5) is higher than locally at all z and
relatively constant or mildly increasing with z within our sample. The data are
consistent with a mild luminosity evolution both in the J and Ks-band up to
z=1.5 (DeltaM_J=-0.69+-0.12 and DeltaM_K=-0.54+-0.12 at z=1). Moreover, we find
that red and early-type galaxies dominate the bright-end of the LF, and that
their number density shows at most a small decrease (<30%) up to z=1, thus
suggesting that massive elliptical galaxies were already in place at z=1 and
they should have formed their stars and assembled their mass at higher z. There
appears to be a correlation of the optical/near-IR colors with near-IR
luminosities, the most luminous/massive galaxies being red/old. We find a slow
evolution with z of the near-IR comoving luminosity density to z=1.5. Finally,
we show that hierarchical models overpredict significantly the density of low
luminosity galaxies at z<=1 and underpredict the density of luminous galaxies
at z>=1, whereas PLE models are more consistent with the data up to z=1.5. The
GIF model (Kaufmann et al. 1999) shows a clear deficiency of red luminous
galaxies at z=1 compared to our observations and predicts a decrease of
luminous galaxies with z not observed in our sample.


title: On Stellar Dynamo Processes and Differential Rotation

abstract:
  Many stars exhibit strong magnetic fields, some of which are thought to be of
primordial origin and others a sign of magnetic dynamo processes. We briefly
review the results of observational studies of solar-type stars seeking to
evaluate the linkage between rotation rate and possible magnetic cycles of
activity. Clearly turbulent convection and rotation within spherical shell
geometries provide ingredients essential for dynamo action. However, intensive
efforts over several decades in solar research have demonstrated that it is no
easy matter to achieve cyclic magnetic activity that is in accord with
observations. Helioseismology has revealed that an essential element for the
global solar dynamo is the presence of a tachocline of shear at the base of the
solar convection zone, leading to the likely operation of an interface dynamo.
We review the crucial elements for achieving a cyclic magnetic activity. We
then discuss some of our current 3--D MHD simulations of solar turbulent
convection in spherical shells that yield differential rotation profiles which
make good contact with some of the helioseismic findings. We show that such
turbulent motions can amplify and sustain magnetic field in the bulk of the
convective zone whose strength are sufficient to feed back both upon the
convection and its global circulations.


title:
The red tail of carbon stars in the LMC: Models meet 2MASS and DENIS
  observations

abstract:
  Carbon stars are known to exhibit systematically redder near-infrared colours
with respect to M-type stars. In the near-infrared colour-magnitude diagrams
provided by the 2MASS and DENIS surveys, the LMC C-type stars draw a striking
red tail, well separated from the sequences of O-rich giants. So far, this
conspicuous feature has been absent from any set of available isochrones, even
the few existing ones that include the TP-AGB evolution of low- and
intermediate-mass stars. To investigate such issue we simulate the complete
2MASS Ks vs.(J-Ks) data towards the LMC by means of a population synthesis
approach, that relies on extended libraries of published stellar evolutionary
tracks, including the TP-AGB phase. The simulations provide quite a detailed
description of the several vertical fingers and inclined sequences seen in
2MASS data, due to both Galactic foreground and LMC O-rich stars. Instead, as
mentioned, the red tail of C-stars sets a major difficulty: we find that TP-AGB
models with solar-scaled molecular opacities, the usual assumption of existing
AGB calculations, do not succeed in reproducing this feature. Our tests
indicate that the main reason for this failure should not be ascribed to
empirical Teff - (J-K) transformations for C-type stars. Instead, the
discrepancy is simply removed by adopting new evolutionary models that account
for the changes in molecular opacities as AGB stars get enriched in carbon via
the third dredge-up (Marigo 2002). In fact, simulations that adopt these models
are able to reproduce, for the first time, the red tail of C-stars in
near-infrared CMDs. Finally, we point out that these simulations also provide
useful indications about the efficiency of the third dredge-up process, and the
pulsation modes of long-period variables.


title:
Corsika+Herwig Monte Carlo Simulation of Neutrino Induced Atmospheric
  Air Showers

abstract:
  High-energy neutrino astronomy represents an open window both on
astrophysical mechanisms of particle acceleration and on fundamental
interactions. The possibility of detecting them in large earth-based apparatus,
like AUGER, AMANDA, ANTARES, is quite challenging. In view of this, the
capability of generating reliable simulations of air showers induced by
neutrinos is mandatory in the analysis of experimental data. In this paper we
describe preliminary results towards the development of a new version of the
Monte Carlo CORSIKA, capable of handling neutrinos too as primary particles. In
our approach the first interaction of the primary neutrino is simulated in
CORSIKA with a call to the HERWIG event generator.


title:
cD galaxy contribution to the strong lensing cross sections of galaxy
  clusters

abstract:
  We perform ray-tracing simulations evaluating the effect of a cD galaxy on
the strong lensing properties of five galaxy cluster halos obtained from N-body
simulations. The cD galaxy is modelled using both axially symmetric and
elliptical models and assuming several masses for its dark matter halo. The
effect of the cD orientation with respect to the mass distribution of the host
galaxy cluster is also investigated. The simulations are carried out in an open
and a flat model universe with cosmological constant. We find that the
enhancement of the cluster lensing cross sections for long and thin arcs due to
the presence of a massive cD at the cluster centre is typically less than 100%,
depending on the model used for the cD galaxy and its orientation. The impact
of the cD on the cluster efficiency for producing radially magnified images is
larger only for those clusters whose lensing cross section for radial arcs is
very small in absence of the central galaxy. We conclude that the presence of a
cD galaxy at the cluster centre can only moderately influence the cluster
efficiency for strong lensing and in particular fails to explain the
discrepancy between the observed number of giant arcs in galaxy clusters and
their abundance predicted from lensing simulations in the currently most
favoured $\Lambda$CDM model.


title: Are we observing black hole spins in jetted Gamma-Ray Bursts?

abstract:
  We note that if the GRB phenomenon follows from the collapse of a massive
object forming a black hole and a torus accreting into it, the resulting ejecta
can be only related to the mass and angular momentum that characterize the
black hole. The opening angle of the fireball then corresponds to a black hole
spin. If indeed the fireballs opening angles are as small as recent estimates
reported in the literature suggest, then GRB would be produced by almost
maximally rotating BH.


title:
Spline histogram method for reconstruction of probability density
  function of clusters of galaxies

abstract:
  We describe the spline histogram algorithm which is useful for visualization
of the probability density function setting up a statistical hypothesis for a
test. The spline histogram is constructed from discrete data measurements using
tensioned cubic spline interpolation of the cumulative distribution function
which is then differentiated and smoothed using the Savitzky-Golay filter. The
optimal width of the filter is determined by minimization of the Integrated
Square Error function.
  The current distribution of the TCSplin algorithm written in f77 with IDL and
Gnuplot visualization scripts is available from
http://www.virac.lv/en/soft.html


title: Effects of the Equation of State on the Formation of Star Clusters

abstract:
  We study the effect of varying the equation of state on the formation of
stellar clusters in turbulent molecular clouds, using three-dimensional,
smoothed particle hydrodynamics simulations. Our results show that the equation
of state helps determine how strongly self-gravitating gas fragments. The
degree of fragmentation decreases with increasing \new{polytropic exponent}
$\gamma$ in the range $0.2 < \gamma < 1.4$, although the total amount of
\new{mass accreted onto collapsed fragments} appears to remain roughly constant
through that range. Low values of $\gamma$ are expected to lead to the
formation of dense clusters of low-mass stars, while $\gamma>1$ probably
results in the formation of isolated and massive stars. Fragmentation and
collapse ceases entirely for $\gamma > 1.4$ as expected from analytic
arguments. The mass spectrum of overdense gas clumps is roughly log-normal for
{\em non}-self-gravitating turbulent gas, but changes to a power-law under the
action of gravity. The spectrum of collapsed cores, on the other hand, remains
log-normal for $\gamma\le 1$, but flattens markedly for $\gamma >1$. The
density PDFs approach log-normal, with widths that decrease with increasing
$\gamma$. Primordial gas may have effective $\gamma > 1$, in which case these
results could help explain why models of the formation of the first stars tend
to produce isolated, massive objects.


title: A Kinship between the EGRET SNR's and Sgr A East

abstract:
  Sgr A East appears to be a single, mixed morphology 10,000 year-old supernova
remnant (SNR) at the Galactic Center. It also appears to belong to a class of
remnants that have been observed and detected at 1720 MHz, the transition
frequency of OH maser emission. However, if the EGRET source 3EG J1746-2852
conincident with the Galactic center is itself associated with this object, it
would endow it with a gamma-ray luminosity almost two orders of magnitude
greater than that of the other EGRET-detected SNR's. We here reconsider the
viability of a pion-production mechanism as the source of the broadband
emission observed from Sgr A East, and show that what connects these objects --
and ultimately also accounts for their different gamma-ray emissivity -- is the
very important interaction between the expanding SNR shell and the surrounding
molecular cloud environment. The singularly high gamma-ray luminosity of Sgr A
East, as well as its unusually steep radio spectral index, can thereby be
attributed to the high-density, strong magnetized environment in which it is
located.


title: Relative Flux Calibration of Keck HIRES Echelle Spectra

abstract:
  We describe a new method to calibrate the relative flux levels in spectra
from the HIRES echelle spectrograph on the Keck-I telescope. Standard data
reduction techniques that transfer the instrument response between HIRES
integrations leave errors in the flux of 5 - 10%, because the effective
response varies. The flux errors are most severe near the ends of each spectral
order, where there can be discontinuous jumps. The source of these errors is
uncertain, but may include changes in the vignetting connected to the optical
alignment. Our new flux calibration method uses a calibrated reference spectrum
of each target to calibrate individual HIRES integrations. We determine the
instrument response independently for each integration, and hence we avoid the
need to transfer the instrument response between HIRES integrations. The
procedure can be applied to any HIRES spectrum, or any other spectrum. While
the accuracy of the method depends upon many factors, we have been able to flux
calibrate a HIRES spectrum to 1% over scales of 200 A that include order joins.
We illustrate the method with spectra of Q1243+3047 towards which we have
measured the deuterium to hydrogen abundance ratio.


title: A Submillimetre Imaging Polarimeter at the James Clerk Maxwell Telescope

abstract:
  A polarimeter has been built for use with the Submillimetre Common-User
Bolometer Array (SCUBA), on the James Clerk Maxwell Telescope (JCMT) in Hawaii.
SCUBA is the first of a new generation of highly sensitive submillimetre
cameras, and the UK/Japan Polarimeter adds a polarimetric imaging/photometry
capability in the wavelength range 350 to 2000 microns. Early science results
range from measuring the synchrotron polarization of the black hole candidate
Sgr A* to mapping magnetic fields inferred from polarized dust emission in
Galactic star-forming clouds. We describe the instrument design, performance,
observing techniques and data reduction processes, along with an assessment of
the current and future scientific capability.


title: The Veritas Project

abstract:
  VERITAS is a new, major ground-based gamma-ray observatory designed to
significantly advance our understanding of extreme astrophysical processes in
the universe. The observatory comprises seven large-aperture (12m diameter)
Cherenkov telescopes, each equipped with an imaging camera. The first phase of
VERITAS (consisting of four telescopes) is currently under construction. Here
we outline the key features of VERITAS and provide an update on its status.


title:
The Energy Dependence of Millisecond Oscillations in Thermonuclear X-ray
  Bursts

abstract:
  We examine the energy-resolved pulse profiles of 51 flux oscillations
observed during the decline of thermonuclear X-ray bursts from accreting
weakly- magnetized neutron stars with the Rossi X-ray Timing Explorer. We find
that the fractional rms amplitudes of the oscillations increase as a function
of energy by 0.25%/keV to 0.9%/keV between 3-20 keV, and are as large as 20% in
the 13-20 keV band. We also show that the pulses observed in the higher energy
bands generally lag behind those in lower energy bands by 0.002 cycles/keV to
0.007 cycles/keV between 3-20 keV. This amounts to total delays of 0.03-0.12
cycles between the lowest and highest energy bands, or time delays that range
from 100-200 mus. We then model the oscillations as flux variations arising
from temperature patterns on the surfaces of rapidly rotating neutron stars. In
this framework, we find that the increase in the pulse amplitude with photon
energy can be explained if the cooler regions on the neutron star emit in the
lower energy bands, reducing the flux variations there. On the other hand, the
Doppler shifts caused by the rapid rotation of the neutron star should cause
the hard pulses to precede the soft pulses by about 0.05 cycles (100 mus), in
contrast to the observations. This suggests that the photons originating from
the stellar surface are reprocessed by a hot corona of electrons before they
reach the observer.


title:
Photoionization Models of Metal-poor Extragalactic HII Regions and the
  Primordial Helium Abundance

abstract:
  We discuss the effects of collisional enhancement of Balmer lines on the
determination of the primordial helium abundance. To this aim, we present a
photoionization model of the metal-poor extragalactic HII region SBS 0335--052.
We show that the derived helium abundance (Y) of this HII region depends on the
amount of collisional excitation affecting the Balmer lines, both directly
(through an underestimation of the actual He/H ratio) and indirectly (through
an overestimation of the interstellar reddening). We detail how each of these
effects affects the derived value of Y.


title:
Physical conditions in NGC 6543 from ISO and HST data and the pitfalls
  of temperature maps

abstract:
  We determine the physical conditions in NGC 6543, obtaining two different
estimates of the electron temperature (T_e) and one estimate of the electron
density (N_e). The electron temperature is computed by means of the [O III]
ratio lambda 5007/lambda 4363, and of the diagnostic diagram combining lambda
5007 to the [O III] infrared lines 52m and 88m. The continuum intensity
measured on slit spectra is much higher than theoretically predicted under the
simplest assumptions. After considering several possibilities, we suggest
enhanced 2-photon emission as the most probable source of the additional
continuum. While T_e and N_e derived from the diagnostic diagram agree with the
most recent determination, T_e derived from lambda 5007/lambda 4363 is smaller
than previously published values, probably due to the bias in lambda 4363
introduced by the uncertainty in the continuum. Our main conclusion is that it
is not possible, with present-day data, to derive accurate temperature maps of
photoionized nebulae.


title: Long-term variability survey of the old open cluster NGC 6791

abstract:
  We present the results of a long-term variability survey of the old open
cluster NGC 6791. The BVI observations, collected over a time span of 6 years,
were analyzed using the ISIS image subtraction package. The main target of our
observations were two cataclysmic variables B7 and B8. We have identified
possible cycle lenghts of about 25 and 18 days for B7 and B8, respectively. We
tentatively classify B7 as a VY Scl type nova-like variable or a Z Cam type
dwarf nova. B8 is most likely an SS Cygni type dwarf nova. We have also
extracted the light curves of 42 other previously reported variable stars and
discovered seven new ones. The new variables show long-period or non-periodic
variability. The long baseline of our observations has also allowed us to
derive more precise periods for the variables, especially for the short period
eclipsing binaries.


title: Accretion limits the compactness of static stars

abstract:
  General relativity limits the compactness of static stars. If the pressure of
the fluid is positive and the density decreases with distance from the center,
the value of the circumferential radius of the star must be greater than (9/4)
G M/c^2, or equivalently the redshift of the surface must be less than two. If
constraints on the equation of state of the material are relaxed, general
relativity alone does not restrict the redshift of a static stellar surface.
However, because black hole candidates in the universe generally accrete
material from their environs, the process of accretion provides upper limits on
the redshift of a astrophysical black-hole candidates.