title:
The Nuclear Region of Low Luminosity Flat Radio Spectrum Sources. I.
  Stellar Content

abstract:
  We have examined the spectroscopic properties of a sample of 19 optically
bright, low luminosity Flat Radio Spectrum (LL FRS) sources. Our study focuses
on the properties of their host galaxies, namely the nuclear stellar
populations and dust content. In the optical, the objects in the sample are
mainly dominated by the host galaxy starlight, which strongly dilutes the
non-thermal continuum as well as possible emission-line features related to the
active nucleus. We have computed the nuclear stellar populations contributing
to the spectra of our objects. The stellar population synthesis has been
performed by using a very reliable mathematical method, which yields a Global
Principal Geometrical solution. Our results show that, for most of the objects
in the sample, the populations are composed of old stars of solar metallicity,
or lower; the populations are mainly composed of late-type stars, i.e. G, K and
M spectral types, the young component coming thus from supergiant stars; the
dust content is weak. Both the stellar populations and the dust content are in
agreement with what is usually observed in "normal" elliptical galaxies.
Similar stellar content has equally been found in the nuclear regions of
galaxies hosting a Low Ionization Nuclear Emission Line Region, or LINER. The
present work is important in illustrating the different applications of stellar
population synthesis in the study of low luminosity radio sources. In fact, the
synthesis allows us not only to obtain valuable information about the stellar
populations and dust content of the host galaxies, therefore providing material
for further studies on the connection between host galaxy and active nucleus,
but also to reveal the so-far unstudied optical emission-line features present
in the spectrum of our objects.


title:
The photospheric abundances of active binaries II. Atmospheric
  parameters and abundance patterns for 6 single-lined RS CVn systems

abstract:
  Photospheric parameters and abundances are presented for a sample of
single-lined chromospherically active binaries from a differential LTE analysis
of high-resolution spectra. Abundances have been derived for 13 chemical
species, including several key elements such as Li, Mg, and Ca. Two methods
have been used. The effective temperatures, surface gravities and
microturbulent velocities were first derived from a fully self-consistent
analysis of the spectra, whereby the temperature is determined from the
excitation equilibrium of the Fe I lines. The second approach relies on
temperatures derived from the (B-V) colour index. These two methods give
broadly consistent results for the stars in our sample, suggesting that the
neutral iron lines are formed under conditions close to LTE. We discuss the
reliability in the context of chromospherically active stars of various colour
indices used as temperature indicators, and conclude that the (V-R) and (V-I)
colours are likely to be significantly affected by activity processes.
Irrespective of the method used, our results indicate that the X-ray active
binaries studied are not as metal poor as previously claimed, but are at most
mildly iron-depleted relative to the Sun (-0.41<[Fe/H]<+0.11). A significant
overabundance of several chemical species is observed (e.g., the
alpha-synthezised elements). These abundance patterns are discussed in relation
to stellar activity.


title:
INTEGRAL discovery of a bright highly obscured galactic X-ray binary
  source IGR J16318-4848

abstract:
  INTEGRAL regularly scans the Galactic plane to search for new objects and in
particular for absorbed sources with the bulk of their emission above 10-20
keV. The first new INTEGRAL source was discovered on 2003 January 29, 0.5
degree from the Galactic plane and was further observed in the X-rays with
XMM-Newton. This source, IGR J16318-4848, is intrinsically strongly absorbed by
cold matter and displays exceptionally strong fluorescence emission lines. The
likely infrared/optical counterpart indicates that IGR J16318-4848 is probably
a High Mass X-Ray Binary neutron star or black hole enshrouded in a Compton
thick environment. Strongly absorbed sources, not detected in previous surveys,
could contribute significantly to the Galactic hard X-ray background between 10
and 200 keV.


title: LOFAR, a new low frequency radio telescope

abstract:
  LOFAR, the Low Frequency Array, is a large radio telescope consisting of
approximately 100 soccer-field sized antenna stations spread over a region of
400 km in diameter. It will operate at frequencies from ~10 to 240 MHz, with a
resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will
allow for studies of a broad range of astrophysical topics, including
reionisation, transient radio sources and cosmic rays, distant galaxies and
AGNs. In this contribution a status rapport of the LOFAR project and an
overview of the science case is presented.


title: Influence of Planets on Parent Stars: Angular Momentum

abstract:
  I review some possible processes by which planets and brown dwarfs can
influence the evolution of their parent evolved stars. As sun-like stars evolve
on the red giant branch (RGB) and then on the asymptotic giant branch (AGB),
they will interact with their close planets (if exist). The interaction starts
with tidal interaction: this will lead the planets to deposit most of their
angular momentum to the envelope of the giant, and then spiral-in to the
envelope. (Too many papers dealing with close planets [less than about 3-6 AU]
around evolved stars neglect tidal interaction, hence their results are
questionable.) They may spin-up their parent stars by up to several orders of
magnitude. The interaction of substellar objects with evolved star may enhance
the mass loss rate, mainly in the equatorial plane. Possible outcomes are: (i)
Planetary systems interacting with their parent AGB star may lead to the
formation of moderate elliptical planetary nebulae. (ii) RGB stars which lose
more mass turn to bluer horizontal branch (HB) stars. Therefore, planets may
explain the formation of blue HB stars. This may explain the presence of many
blue HB stars in many globular clusters (the planets be the second parameter),
and some hot HB stars in the galaxy (sdB stars). (The 8.3 days use of the
Hubble Space Telescope in search of planets in a globular clusters with no blue
HB stars was a wrong move.) (iii) Most known stars with planets will not form
planetary nebulae, because they will lose most of their envelope already on the
RGB.


title: 3-Dimensional Core-Collapse

abstract:
  In this paper, we present the results of 3-dimensional collapse simulations
of rotating stars for a range of stellar progenitors. We find that for the
fastest spinning stars, rotation does indeed modify the convection above the
proto-neutron star, but it is not fast enough to cause core fragmentation.
Similarly, although strong magnetic fields can be produced once the
proto-neutron star cools and contracts, the proto-neutron star is not spinning
fast enough to generate strong magnetic fields quickly after collapse and, for
our simulations, magnetic fields will not dominate the supernova explosion
mechanism. Even so, the resulting pulsars for our fastest rotating models may
emit enough energy to dominate the total explosion energy of the supernova.
However, more recent stellar models predict rotation rates that are much too
slow to affect the explosion, but these models are not sophisticated enough to
determine whether the most recent, or past, stellar rotation rates are most
likely. Thus, we must rely upon observational constraints to determine the true
rotation rates of stellar cores just before collapse. We conclude with a
discussion of the possible constraints on stellar rotation which we can derive
from core-collapse supernovae.


title: Collisional Cascades in Planetesimal Disks II. Embedded Planets

abstract:
  We use a multiannulus planetesimal accretion code to investigate the growth
of icy planets in the outer regions of a planetesimal disk. In a quiescent
minimum mass solar nebula, icy planets grow to sizes of 1000--3000 km on a
timescale t = 15-20 Myr (a/30 AU)^3 where a is the distance from the central
star. Planets form faster in more massive nebulae. Newly-formed planets stir up
leftover planetesimals along their orbits and produce a collisional cascade
where icy planetesimals are slowly ground to dust.
  The dusty debris of planet formation has physical characteristics similar to
those observed in beta Pic, HR 4796A, and other debris disks. We derive dust
masses for small particles, 1 mm and smaller, and large particles, 1 mm and
larger, as a function of the initial conditions in the planetesimal disk. The
dust luminosities derived from these masses are similar to those observed in
Vega, HR 4796A, and other debris disks. The calculations produce bright rings
and dark gaps. Bright rings occur where 1000 km and larger planets have
recently formed. Dark gaps are regions where planets have cleared out dust or
shadows where planets have yet to form.


title:
The chemical composition of the peculiar companion to the millisecond
  pulsar in NGC 6397

abstract:
  We present the chemical composition of the bright companion to the
millisecond pulsar J1740-5340 in NGC 6397, based on high resolution spectra.
Though the large rotation velocity of the star broadens the lines and
complicates the analysis, the derived abundances are found fully compatible
with those of normal unperturbed stars in NGC 6397, with the exception of a few
elements (Li, Ca, and C). The lack of C suggests that the star has been peeled
down to regions where incomplete CNO burning occurs, favouring a scenario where
the companion is a turn-off star which has lost most of its mass. In addition
we found an unexpected large Li abundance, which suggests that fresh 7Li has
been produced on the stellar surface.


title:
The Recent Evolution of the Dwarf Starburst Galaxy NGC 625 from Hubble
  Space Telescope Imaging

abstract:
  New HST/WFPC2 imaging of the dwarf starburst galaxy NGC 625 is presented.
These data, 80% complete to V and I magnitudes of 26.0 and 25.3, respectively,
allow us to study the recent star formation history of NGC 625. We derive a tip
of the red giant branch (TRGB) distance modulus of 27.95+/-0.07, corresponding
to a distance of 3.89+/-0.22 Mpc, and a location on the far side of the
Sculptor Group. NGC 625 has a well-defined radial stellar population gradient,
evidenced by a central concentration of young MS stars and an RGB/AGB ratio
that increases with galactocentric distance. The prominent AGB is very red, and
RGB stars are detected far from the central star forming regions. Using H Alpha
and H Beta narrow band imaging and previous optical spectroscopy we identify
substantial and varying internal extinction (A_V = 0.0 to 0.6 mag) associated
with the central active star formation regions. To better understand the
effects of internal extinction on the analysis of young stellar populations,
synthetic models are presented which, for the first time, examine and account
for this effect. Using the luminous blue helium burning stars, we construct a
simple model of the recent (< 100 Myr) star formation in which an elevated but
declining star formation rate has been present over this entire period. This is
at odds with the presence of spectroscopic W-R features in the major star
formation region which imply a short duration (<= 5 Myr) for the recent
starburst. This suggests that starbursts displaying W-R features are not
necessarily all of a short duration. Finally, we speculate on the possible
causes of the present burst of star formation in this apparently isolated
galaxy, and compare it to other nearby, well-studied dwarf starburst systems.


title: On the Intracluster Medium in Cooling Flow & Non-Cooling Flow Clusters

abstract:
  Recent X-ray observations have highlighted clusters that lack entropy cores.
At first glance, these results appear to invalidate the preheated ICM models.
We show that a self-consistent preheating model, which factors in the effects
of radiative cooling, is in excellent agreement with the observations.
Moreover, the model naturally explains the intrinsic scatter in the L-T
relation, with ``cooling flow'' and ``non-cooling flow'' systems corresponding
to mildly and strongly preheated systems, respectively. We discuss why
preheating ought to be favoured over merging as a mechanism for the origin of
``non-cooling flow'' clusters.


title: Evolution of the Cluster Correlation Function

abstract:
  We study the evolution of the cluster correlation function and its
richness-dependence from z = 0 to z = 3 using large-scale cosmological
simulations. A standard flat LCDM model with \Omega_m = 0.3 and, for
comparison, a tilted \Omega_m = 1 model, TSCDM, are used. The evolutionary
predictions are presented in a format suitable for direct comparisons with
observations. We find that the cluster correlation strength increases with
redshift: high redshift clusters are clustered more strongly (in comoving
scale) than low redshift clusters of the same mass. The increased correlations
with redshift, in spite of the decreasing mass correlation strength, is caused
by the strong increase in cluster bias with redshift: clusters represent higher
density peaks of the mass distribution as the redshift increases. The
richness-dependent cluster correlation function, presented as the
correlation-scale versus cluster mean separation relation, R_0 - d, is found to
be, remarkably, independent of redshift to z <~ 2 for LCDM and z <~ 1 for TCDM
(for a fixed correlation function slope and cluster mass within a fixed
comoving radius). The non-evolving R_0 - d relation implies that both the
comoving clustering scale and the cluster mean separation increase with
redshift for the same mass clusters so that the R_0 - d relation remains
essentially unchanged. The evolution of the R_0 - d relation from z ~ 0 to z ~
3 provides an important new tool in cosmology; it can be used to break
degeneracies that exist at z ~ 0 and provide precise determination of
cosmological parameters.


title:
A Model For the Formation of High Density Clumps in Proto-Planetary
  Nebulae

abstract:
  The detection of NaCl at large radii in the Egg Nebula, CRL 2688, requires
densities of 10^7 - 10^8 cm^-3 in a thick shell of r ~ a few X 10^17 cm. To
explain these results, a mechanism is needed for producing high densities at a
considerable distance from the central star. In two dimensional simulations of
the interaction of the fast wind with an ambient medium, the material becomes
thermally unstable. The resulting clumps can achieve the requisite conditions
for NaCl excitation. We present 2D models with simple physics as
proof-of-principle calculations to show that the clumping behavior is robust.
Clumping is a natural outcome of cooling in the colliding wind model and
comparable to that inferred from observations.


title:
Chandra and XMM-Newton Observations of RDCS1252.9-2927, A Massive
  Cluster at z=1.24

abstract:
  We present deep Chandra and XMM obervations of the galaxy cluster
RDCS1252.9-2927, which was selected from the ROSAT Deep Cluster Survey (RDCS)
and confirmed by extensive spectroscopy with the VLT at redshift z=1.237. With
the Chandra data, the X-ray emission from the intra-cluster medium is well
resolved and traced out to 500 kpc, thus allowing a measurement of the physical
properties of the gas with unprecedented accuracy at this redshift. We detect a
clear 6.7 keV Iron K line in the Chandra spectrum providing a redshift within
1% of the spectroscopic one. By augmenting our spectroscopic analysis with the
XMM data (MOS detectors only), we significantly narrow down the 1 sigma error
bar to 10% for the temperature and 30% for the metallicity, with best fit
values kT = 6.0(+0.7,-0.5) keV, Z = 0.36(+0.12,-0.10) Z_sun. In the likely
hypothesis of hydrostatic equilibrium, we measure a total mass of M_{500} =
(1.9+-0.3)10^14 h_70^{-1}M_sun within R_{Delta=500} = 536 kpc. Overall, these
observations imply that RDCS1252.9-2927 is the most X-ray luminous and likely
the most massive bona-fide cluster discovered to date at z>1. When combined
with current samples of distant clusters, these data lend further support to a
mild evolution of the cluster scaling relations, as well the metallicity of the
intra-cluster gas. Inspection of the cluster mass function in the current
cosmological concordance model (h,Omega_m,Omega_Lambda)=(0.7,0.3,0.7) and
sigma_8=0.7-0.8 shows that RDCS1252.9-2927 is an M* cluster at z=1.24, in
keeping with number density expectations in the RDCS survey volume.


title:
The Parsec-Scale Structure and Jet Motions of the TeV Blazars 1ES
  1959+650, PKS 2155-304, and 1ES 2344+514

abstract:
  As part of our study of the VLBI properties of TeV blazar jets, we present
here a series of high-resolution 15 GHz Very Long Baseline Array (VLBA) images
of the parsec-scale jets of the TeV blazars 1ES 1959+650, PKS 2155-304, and 1ES
2344+514, with linear resolutions of about 0.5 pc. Each of these sources was
observed with the VLBA at three or four epochs during 1999 and 2000. There is a
notable lack of any strong moving components on the VLBI images (in contrast to
the rapid superluminal motions seen in EGRET blazars), and the structure of the
VLBI jet can be modeled either as a series of stationary Gaussian components,
or as a smooth power law for two of the sources (PKS 2155-304 and 1ES
2344+514). The low apparent speeds, together with beaming indicators such as
the brightness temperature of the VLBI core, imply only modest Doppler boosting
of the VLBI radio emission, and only modest bulk Lorentz factors; in contrast
to the more extreme values of these parameters invoked to explain the
high-energy emission. The fact that no moving shocks or plasmoids are seen on
the parsec-scale suggests that the shocks or plasmoids that are assumed to be
responsible for the high-energy flares must dissipate before they separate from
the core on the VLBI images. This requires the loss of a substantial amount of
bulk kinetic energy on parsec scales, and implies a higher efficiency than is
typically assumed for internal shock scenarios.


title: Blazars (VLBA & Glast)

abstract:
  This review paper discusses the past and present observations of gamma-ray
blazars with both space and ground-based gamma-ray telescopes (such as EGRET
and current TeV telescopes), and with the VLBA. I also discuss the more
sensitive gamma-ray telescopes such as AGILE and GLAST that will become
available over the next several years, and how observations with these
telescopes, together with improved VLBA observations, can increase our
understanding of blazar physics.


title:
Hubble Space Telescope Observations of UV Oscillations in WZ Sagittae
  During the Decline from Outburst

abstract:
  We present a time series analysis of Hubble Space Telescope observations of
WZ Sge obtained in 2001 September, October, November and December as WZ Sge
declined from its 2001 July superoutburst. Previous analysis of these data
showed the temperature of the white dwarf decreased from ~29,000 K to ~18,000
K. In this study we binned the spectra over wavelength to yield ultraviolet
light curves at each epoch that were then analyzed for the presence of the
well-known 27.87 s and 28.96 s oscillations. We detect the 29 s periodicity at
all four epochs, but the 28 s periodicity is absent. The origin of these
oscillations has been debated since their discovery in the 1970s and competing
hypotheses are based on either white dwarf non-radial g-mode pulsations or
magnetically-channelled accretion onto a rotating white dwarf. By analogy with
the ZZ Ceti stars, we argue that the non-radial g-mode pulsation model demands
a strong dependence of pulse period on the white dwarf's temperature. However,
these observations show the 29 s oscillation is independent of the white
dwarf's temperature. Thus we reject the white dwarf non-radial g-mode pulsation
hypothesis as the sole origin of the oscillations. It remains unclear if
magnetically-funnelled accretion onto a rapidly rotating white dwarf (or belt
on the white dwarf) is responsible for producing the oscillations. We also
report the detection of a QPO with period ~18 s in the September light curve.
The amplitudes of the 29 s oscillation and the QPO vary erratically on short
timescales and are not correlated with the mean system brightness nor with each
other.


title:
Occurrence and Global Properties of Narrow CIV lambda 1549 Absorption
  Lines in Moderate-Redshift Quasars

abstract:
  A statistical study is presented of (a) the frequency of narrow CIV lambda
1549 absorption lines in 1.5 <~ z <~ 3.6 radio-quiet and radio-loud quasars,
and of (b) the UV and radio properties of the absorbed quasars. The quasar
sample is unbiased with respect to absorption properties and the radio-quiet
and radio-loud subsamples are well matched in redshift and luminosity. A
similarly high incidence (>~50%) of narrow CIV absorbers is detected for the
radio-quiet and radio-loud quasars, and a constant ~25% of all the quasars,
irrespective of radio type display associated CIV absorbers stronger than a
rest equivalent width of 0.5A. Both radio-quiet and radio-loud quasars with
narrow absorption lines have systematically redder continua, especially
strongly absorbed objects. There is evidence of inclination dependent dust
reddening and absorption for the radio quasars. An additional key result is
that the most strongly absorbed radio quasars have the largest radio source
extent. This result is in stark contrast to a recent study of the low-frequency
selected Molonglo survey in which a connection between the strength of the
narrow absorbers and the (young) age of the radio source has been proposed. The
possible origin of these discrepant results is discussed and may be related to
the higher source luminosity for the quasars studied here.


title:
Candidate Type II Quasars from the Sloan Digital Sky Survey: I.
  Selection and Optical Properties of a Sample at 0.3<Z<0.83

abstract:
  Type II quasars are the long-sought luminous analogs of type II (narrow
emission line) Seyfert galaxies, suggested by unification models of active
galactic nuclei (AGN) and postulated to account for an appreciable fraction of
the cosmic hard X-ray background. We present a sample of 291 type II AGN at
redshifts 0.3<Z<0.83 from the spectroscopic data of the Sloan Digital Sky
Survey. These objects have narrow (FWHM<2000 km/s), high equivalent width
emission lines with high-ionization line ratios. We describe the selection
procedure and discuss the optical properties of the sample. About 50% of the
objects have [OIII] \lambda_air 5007 line luminosities in the range 3\times
10^8-10^10 L_Sun, comparable to those of luminous (-27<M_B<-23) quasars; this,
along with other evidence, suggests that the objects in the luminous subsample
are type II quasars.


title:
Gemini-Phoenix infrared high-resolution abundance analysis of five
  giants in the bulge globular cluster NGC 6553

abstract:
  A detailed abundance analysis of 5 giants of the metal-rich bulge globular
cluster NGC 6553 was carried out using high resolution infrared spectra in the
H band, obtained at the Gemini-South 8m telescope. JK photometry collected at
ESO and VI photometry from the Hubble Space Telescope are used to derive
effective temperatures. The present analysis provides a metallicity [Fe/H] =
-0.20 +/- 0.10. An overabundance of oxygen of [O/Fe] = +0.20 is found from IR
OH lines.


title: Hot Gas In and Around Elliptical Galaxies

abstract:
  We review the origin, evolution and physical nature of hot gas in elliptical
galaxies and associated galaxy groups. Unanticipated recent X-ray observations
with Chandra and XMM indicate much less cooling than previously expected.
Consequently, many long-held assumptions need to be reexamined or discarded and
new approaches must be explored. Chief among these are the role of heating by
active galactic nuclei, the influence of radio lobes on the hot gas, details of
the cooling process, possible relation between the hot and colder gas in
elliptical galaxies, and the complexities of stellar enrichment of the hot gas.


title:
The nature of low T/|W| dynamical instabilities in differentially
  rotating stars

abstract:
  Recent numerical simulations indicate the presence of dynamical instabilities
of the f-mode in differentially rotating stars even at very low values of
$T/|W|$, the ratio of kinetic to potential energy. In this Letter we argue that
these may be shear instabilities which occur when the degree of differential
rotation exceeds a critical value and the f-mode develops a corotation point
associated with the presence of a continuous spectrum. Our explanation, which
is supported by detailed studies of a simple shell model, offers a
straightforward way of understanding all of the key features of these
instabilities.


title: The Type Ic Hypernova SN 2003dh/GRB 030329

abstract:
  The spectra of SN 2003dh, identified in the afterglow of GRB030329, are
modeled using radiation transport codes. It is shown that SN 2003dh had a high
explosion kinetic energy ($\sim 4 \times 10^{52}$ erg in spherical symmetry),
making it one of the most powerful hypernovae observed so far, and supporting
the case for association between hypernovae and Gamma Ray Bursts. However, the
light curve derived from fitting the spectra suggests that SN 2003dh was not as
bright as SN 1998bw, ejecting only $\sim 0.35\Msun$ of \Nifs. The spectra of SN
2003dh resemble those of SN 1998bw around maximum, but later they look more
like those of the less energetic hypernova SN 1997ef. The spectra and the
inferred light curve can be modeled adopting a density distribution similar to
that used for SN 1998bw at $ v > 25,000$\kms but more like that of SN 1997ef at
lower velocities. The mass of the ejecta is $\sim 8\Msun$, somewhat less than
in the other two hypernovae. The progenitor must have been a massive star ($M
\sim 35-40\Msun$), as for other hypernovae. The need to combine different
one-dimensional explosion models strongly indicates that SN 2003dh was an
asymmetric explosion.


title:
Reconstruction of solar activity for the last millennium using $^{10}$Be
  data

abstract:
  In a recent paper (Usoskin et al., 2002a), we have reconstructed the
concentration of the cosmogenic $^{10}$Be isotope in ice cores from the
measured sunspot numbers by using physical models for $^{10}$Be production in
the Earth's atmosphere, cosmic ray transport in the heliosphere, and evolution
of the Sun's open magnetic flux. Here we take the opposite route: starting from
the $^{10}$Be concentration measured in ice cores from Antarctica and
Greenland, we invert the models in order to reconstruct the 11-year averaged
sunspot numbers since 850 AD. The inversion method is validated by comparing
the reconstructed sunspot numbers with the directly observed sunspot record
since 1610. The reconstructed sunspot record exhibits a prominent period of
about 600 years, in agreement with earlier observations based on cosmogenic
isotopes. Also, there is evidence for the century scale Gleissberg cycle and a
number of shorter quasi-periodicities whose periods seem to fluctuate in the
millennium time scale. This invalidates the earlier extrapolation of
multi-harmonic representation of sunspot activity over extended time intervals.


title: The Radio Afterglows of Gamma-Ray Bursts

abstract:
  Radio afterglow studies have become an integral part of the study of
gamma-ray bursts, providing complementary and sometimes unique diagnostics on
GRB explosions, their progenitors, and their environments. This brief review
consists of two parts. The first section is a summary of current search
strategies and the main observational properties of radio afterglows. In the
second section we highlight the key scientific contributions made by radio
observations, either alone or as part of panchromatic studies.


title:
Massive black hole remnants of the first stars II: optical and X-ray
  signatures in present-day galactic haloes

abstract:
  The first stars forming in minihaloes at redshifts greater than 20 may have
been very massive and could have left behind massive black hole (MBH) remnants.
In a previous paper we investigated the hierarchical merging of these MBHs and
their associated haloes, using a semi-analytical approach consisting of a
hierarchical merger tree algorithm and explicit prescriptions for the dynamics
of merged substructure inside a larger host halo following a merger. One of the
results was the prediction of a number of MBHs orbiting throughout present-day
galactic haloes. In addition we determined the mass accretion rate of these
MBHs assuming that they could in principle remain embedded in a gaseous core
that is a remnant of the haloes with which the MBHs were associated before
merging with the host system. On this basis we determine in this paper the
bolometric, optical and X-ray luminosity functions for the accreting MBHs using
thin disk and advection dominated accretion flow models. Our predicted MBH
X-ray emissions are then compared with observations of ultra-luminous X-ray
sources in galaxies. We find that the slope and normalisation of the predicted
X-ray luminosity function are consistent with the observations.


title:
Massive black hole remnants of the first stars III: observational
  signatures from the past

abstract:
  The first stars forming in minihaloes at redshifts greater than 20 may have
been very massive and could have left behind massive black hole (MBH) remnants.
In previous papers we investigated the hierarchical merging of these `seed'
MBHs and their associated haloes, using a semi-analytical approach consisting
of a hierarchical merger tree algorithm and explicit prescriptions for the
dynamics of merged substructure inside a larger host halo following a merger.
We also estimated accretion luminosities for these MBHs and found them to be
consistent with observations of ultra-luminous X-ray point sources. Here we
compute the strength of gravitational wave events as MBHs merge to grow from
seed mass MBH at high redshifts to those that we predict to reside in galaxy
haloes today. If MBHs merge efficiently we predict that some 10^4 - 10^5 events
per year could be observed, that fall just within the sensitivity limits of the
proposed LISA gravitational wave observatory. The collapse of the first massive
stars to form MBHs may be accompanied by gamma ray bursts (GRBs). If this is
the case and GRBs are in principle observable out to the redshifts of first
star formation, we find that about 10^5 - 10^6 GRBs per year could be detected.
As merging MBH binaries reach their last stable orbits before final coalescence
a fraction of the gravitational wave energy may be released as a pulse of gamma
rays (for instance, through interaction with material enveloping a merging MBH
binary). This fraction has to be in the range between 10^{-14} - 10^{-10} for
MBH mergers to be less luminous than GBRs, yet detectable out to cosmological
distances with upcoming GRB detector missions.


title: New measurements of magnetic fields of roAp stars with FORS1 at the VLT

abstract:
  Magnetic fields play a key role in the pulsations of rapidly oscillating Ap
(roAp) stars since they are a necessary ingredient of all pulsation excitation
mechanisms proposed so far. This implies that the proper understanding of the
seismological behaviour of the roAp stars requires knowledge of their magnetic
fields. However, the magnetic fields of the roAp stars are not well studied.
Here we present new results of measurements of the mean longitudinal field of
14 roAp stars obtained from low resolution spectropolarimetry with FORS1 at the
VLT.


title:
Measurements of magnetic fields over the pulsation cycle in six roAp
  stars with FORS1 at the VLT

abstract:
  With FORS1 at the VLT we have tried for the first time to measure the
magnetic field variation over the pulsation cycle in six roAp stars to begin
the study of how the magnetic field and pulsation interact. For the star
HD101065, which has one of the highest photometric pulsation amplitudes of any
roAp star, we found a signal at the known photometric pulsation frequency at
the 3 sigma level in one data set; however this could not be confirmed by later
observations. A preliminary simple calculation of the expected magnetic
variations over the pulsation cycle suggests that they are of the same order as
our current noise levels, leading us to expect that further observations with
increased S/N have a good chance of achieving an unequivocal detection.


title: Vertical distribution of chromium in the atmospheres of HgMn stars

abstract:
  We use multiplet 30 Cr II lines in the wings of H_beta to test the hypothesis
of an anomalous concentration of Cr in the upper layers of the atmospheres of a
sample of 10 HgMn stars. These lines are at different distances from the H_beta
line center and are therefore formed at different depths in the stellar
atmosphere. Except for HD49606, all HgMn stars show an increase of Cr abundance
with height in the stellar atmosphere. A similar vertical distribution of Cr,
but less pronounced, has been previously found in Am stars. In contrast, no
variation of Cr abundance with the depth has been found for the normal late
B-type star HD196426 and the weak magnetic late B-type star HD168733. It is
possible that in HgMn stars the vertical stratification parameter, a, depends
on T_eff, with the strongest vertical gradient being found in the hotter stars.
No correlation was found between $a$ and the average stellar abundance log
epsilon(Cr/H).


title: The Earliest Optical Observations of GRB 030329

abstract:
  We present the earliest optical imaging observations of GRB 030329 related to
SN 2003dh. The burst was detected by the HETE-2 satellite at 2003 March 29,
11:37:14.67 UT. Our wide-field monitoring started 97 minutes before the trigger
and the burst position was continuously observed. We found no precursor or
contemporaneous flare brighter than $V=5.1$ ($V=5.5$) in 32 s (64 s) timescale
between 10:00 and 13:00 UT. Follow-up time series photometries started at
12:51:39 UT (75 s after position notice through the GCN) and continued for more
than 5 hours. The afterglow was $Rc= 12.35\pm0.07$ at $t=74$ min after burst.
Its fading between 1.2 and 6.3 hours is well characterized by a single
power-law of the form $f{\rm(mJy)} = (1.99\pm0.02{\rm (statistic)}\pm0.14{\rm
(systematic)}) \times (t/1 {\rm day})^{-0.890\pm 0.006 {\rm (statistic)}\pm
0.010 {\rm (systematic)}}$ in $Rc$-band. No significant flux variation was
detected and upper limits are derived as $(\Delta f/f)_{\rm RMS} = 3-5$% in
minutes to hours timescales and $(\Delta f/f)_{\rm RMS} = 35-5$% in seconds to
minutes timescales. Such a featureless lightcurve is explained by the smooth
distribution of circumburst medium. Another explanation is that the optical
band was above the synchrotron cooling frequency where emergent flux is
insensitive to the ambient density contrasts. Extrapolation of the afterglow
lightcurve to the burst epoch excludes the presence of an additional flare
component at $t<10$ minutes as seen in GRB 990123 and GRB 021211.


title: The photo-neutrino process in astrophysical systems

abstract:
  Explicit expressions for the differential and total rates and emissivities of
neutrino pairs from the photo-neutrino process $e^\pm + \gamma \to e^\pm + \nu
+ \bar\nu$ in hot and dense matter are derived. Full information about the
emitted neutrinos is retained by evaluating the squared matrix elements for
this process which was hitherto bypassed through the use of Lenard's identity
in obtaining the total neutrino emissivities. Accurate numerical results are
presented for widely varying conditions of temperature and density. Analytical
results helpful in understanding the qualitative behaviors of the rates and
emissivities in limiting situations are derived. The corresponding production
and absorption kernels in the source term of the Boltzmann equation for
neutrino transport are developed. The appropriate Legendre coefficients of
these kernels, in forms suitable for multigroup flux-limited diffusion schemes
are also provided.


title:
Cleaning sky survey databases using Hough Transform and Renewal String
  approaches

abstract:
  Large astronomical databases obtained from sky surveys such as the
SuperCOSMOS Sky Survey (SSS) invariably suffer from spurious records coming
from artefactual effects of the telescope, satellites and junk objects in orbit
around earth and physical defects on the photographic plate or CCD. Though
relatively small in number these spurious records present a significant problem
in many situations where they can become a large proportion of the records
potentially of interest to a given astronomer. Accurate and robust techniques
are needed for locating and flagging such spurious objects, and we are
undertaking a programme investigating the use of machine learning techniques in
this context. In this paper we focus on the four most common causes of unwanted
records in the SSS: satellite or aeroplane tracks, scratches, fibres and other
linear phenomena introduced to the plate, circular halos around bright stars
due to internal reflections within the telescope and diffraction spikes near to
bright stars. Appropriate techniques are developed for the detection of each of
these. The methods are applied to the SSS data to develop a dataset of spurious
object detections, along with confidence measures, which can allow these
unwanted data to be removed from consideration. These methods are general and
can be adapted to other astronomical survey data.


title: Restrictions on a geometrical language in gravity

abstract:
  It was shown by the author (gr-qc/0207006) that screening the background of
super-strong interacting gravitons creates Newtonian attraction if single
gravitons are pairing and graviton pairs are destructed by collisions with a
body. In such the model, Newton's constant is connected with Hubble's constant,
for which the estimate is obtained: $94.576 km \cdot s^{-1} \cdot Mpc^{-1}.$ It
is necessary to assume an atomic structure of any body to have the working
model. Because of it, an existence of black holes contradicts to the
equivalence principle in a frame of the model. For usual matter, the
equivalence principle should be broken at distances $\sim 10^{-11} m,$ if the
model is true.


title: Modeling the Tidal Tails of the Sagittarius Dwarf Galaxy

abstract:
  N-body simulations are used to model the tidal disruption of the Sagittarius
(Sgr) dwarf galaxy with constraints set by the positions and velocities of M
giants in the Sgr tidal arms recently revealed by the Two Micron All-Sky Survey
(2MASS). The simulated Sgr dwarf is placed on a variety of orbits within a
Milky Way potential parameterized by variable circular velocities, halo
flattenings and radial profiles. Two hundred separate test particle orbits have
been used to explore a wide range of model Milky Way potentials and dwarf
galaxy characteristics. The family of models is delimited by the data to a
relatively narrow allowed range of parameters, and then input into N-body
simulations. We present our best-fitting model, and discuss the orbital period,
apoGalacticon distance, current space velocity, mass-to-light ratio, and other
characteristics of the Sgr dwarf. In addition, we discuss the implications of
this model for the flattening of the Galactic halo.


title:
Wide band X-ray and optical observations of the BL Lac object 1ES
  1959+650 in high state

abstract:
  The blazar 1ES 1959+650 was observed twice by BeppoSAX in September 2001
simultaneously with optical observations. We report here the X-ray data
together with the optical, R_C magnitude, light curve since August 1995. The
BeppoSAX observations were triggered by an active X-ray status of the source.
The X-ray spectra are brighter than the previously published X-ray
observations, although the source was in an even higher state a few months
later, as monitored by the ASM onboard RossiXTE, when it was also detected to
flare in the TeV band. Our X-ray spectra are well represented by a continuosly
curved model up to 45 keV and are interpreted as synchrotron emission, with the
peak moving to higher energies. This is also confirmed by the slope of the
X-ray spectrum which is harder than in previous observations. Based on our
optical and X-ray data, the synchrotron peak turns out to be in the range
0.1-0.7 keV. We compare our data with non simultaneous radio to TeV data and
model the spectral energy distribution with a homogeneous, one-zone synchrotron
inverse Compton model. We derive physical parameters that are typical of low
power High Energy peaked Blazar, characterised by a relatively large beaming
factor, low luminosity and absence of external seed photons.


title: Constraints on a Cardassian model from SNIa data - revisited

abstract:
  We discuss some observational constraints resulting only from SNIa
observations, imposed on the behavior of the original flat Cardassian model,
and its extension with the curvature term included. We test the models using
the Perlmutter SN Ia data as well as the new Knop and Tonry samples. We
estimate the Cardassian model parameters using the best-fitting procedure and
the likelihood method. In the fitting procedure we use the density variables
for matter, Cardassian fluid and curvature, and include the errors in redshift
measurements. For the Perlmutter sample in the non-flat Cardassian model we
obtain the high or normal matter density universe ($\Omega_{m,0} \ge 0.3$),
while for the flat Cardassian model we have the high density universe. For
sample A in the high density universe we also find the negative values of
estimates of $n$ which can be interpreted as the phantom fluid effect. For the
likelihood method we get that a nearly flat universe is preferred. We show
that, if we assume that the matter density is 0.3, then $n \approx 0$ in the
flat Cardassian model, which corresponds to the Perlmutter model with the
cosmological constant. Testing with the Knop and Tonry SN Ia samples show no
significant differences.


title: Testing the locality of transport in self-gravitating accretion discs

abstract:
  In this paper we examine the issue of characterizing the transport associated
with gravitational instabilities in relatively cold discs, discussing in
particular under which condition it can be described within a local, viscous
framework. We present the results of global, three-dimensional, SPH simulations
of self-gravitating accretion discs, in which the disc is cooled using a simple
parameterization for the cooling function. Our simulations show that the disc
settles in a ``self-regulated'' state, where the axisymmetric stability
parameter $Q\approx 1$ and where transport and energy dissipation are dominated
by self-gravity. We have computed the gravitational stress tensor and compared
our results with expectations based on a local theory of transport. We find
that, for disc masses smaller than $0.25M_{\star}$ and aspect ratio
$H/r\lesssim 0.1$, transport is determined locally, thus allowing for a viscous
treatment of the disc evolution.


title: The Cartwheel ring under X-ray light

abstract:
  The Cartwheel, archetypical ring galaxy with strong star formation activity
concentrated in a peculiar annular structure, has been imaged with the CHANDRA
ACIS-S instrument. We present here preliminary results, that confirm the high
luminosity detected earlier with the ROSAT HRI. Many bright isolated sources
are visible in the star-forming ring. A diffuse component at luminosity of the
order of 10E.40 cgs is also detected.


title: First NACO observations of the Brown Dwarf LHS 2397aB

abstract:
  Observations of the standard late type M8 star LHS 2397aA were obtained at
the ESO-VLT 8m telescope ``Yepun'' using the NAOS/CONICA Adaptive Optics
facility. The observations were taken during the NACO commissioning, and the
infrared standard star LHS 2397aA was observed in the H, and Ks broad band
filters. In both bands the brown dwarf companion LHS2397aB was detected. Using
a program recently developed (Bouy et al., 2003) for the detection of stellar
binaries we calculated the principal astrometric parameters (angular binary
separation and position angle P.A.) and the photometry of LHS 2397aA and LHS
2397aB. Our study largely confirms previous results obtained with the
AO-Hokupa'a facility at Gemini-North (Freed et al., 2003); however a few
discrepancies are observed.


title: The "sigma" problem of the Crab pulsar wind

abstract:
  The conversion of the Crab pulsar wind from one dominated by Poynting flux
close to the star to one dominated by particle-born energy at the termination
shock is considered. The idea put forward by Coroniti (1990) and criticised by
Lyubarsky & Kirk (2001) that reconnection in a striped wind is responsible, is
generalised to include faster prescriptions for the a priori unknown
dissipation rate. Strong acceleration of the wind is confirmed, and the higher
dissipation rates imply complete conversion of Poynting flux into particle-born
flux within the unshocked wind.


title: HST Observations of Young Stellar Clusters in Nearby Galaxies

abstract:
  The HST data archive contains images of several nearby spirals, suitable for
detailed studies of the properties of individual star clusters and their
surroundings. By combining structural information derived from HST images with
ground-based photometry, it is possible to study cluster properties as a
function of age and mass. While both the core- and effective radii of young
clusters correlate with mass, the slopes of these relations are shallower than
for a constant-density relation, implying that the mean density increases with
cluster mass. This must be accounted for in theories for cluster formation.


title: Atmosphere-Corrected Phase-Referencing

abstract:
  One major problem of phase-referencing VLBI observations are phase errors due
to the unknown tropospheric zenith delay at each antenna. These errors degrade
the quality of the phase-referenced image and limit the achievable astrometric
accuracy. We will present and compare two independent methods to estimate the
zenith delay offset at each antenna. The zenith delay offsets can then be used
to correct the data. These corrections improve the quality of the
phase-referenced image and an astrometric accuracy of 10 $\mu$as can be
achieved. With this accuracy, measurements of proper motions in the Local Group
become feasible.


title:
Detection of reactive ions in the ultracompact HII regions Mon R2 and
  G29.96-0.02

abstract:
  We report the first detection of the reactive ions CO+ and HOC+ towards
ultracompact (UC) HII regions, particularly in Mon R2 and G29.96-0.02. We have
observed two positions in Mon R2, namely the peak of the UC HII region and a
position in the high density molecular cloud which bounds it. CO+ and HOC+ were
detected at the UC HII region but not at the molecular cloud, as expected if
the CO$^+$ and HOC$^+$ emissions arise in the PDR surrounding the \uch. The
measured CO$^+$ and HOC$^+$ column densities are of the order of 10$^{11}$
cm$^{-2}$ in both sources, which yields a strikingly low [HCO$^+$]/[HOC$^+$]
abundance ratio of 460 in Mon R2. These values are similar to those found in
some other well-known PDRs, like NGC 7023 and the Orion Bar. We briefly discuss
the chemical implications of these results.


title: A method for relaxing the CFL-condition in time explicit schemes

abstract:
  A method for relaxing the CFL-condition, which limits the time step size in
explicit methods in computational fluid dynamics, is presented. The method is
based on re-formulating explicit methods in matrix form, and considering them
as a special-Jacobi iteration scheme that converge efficiently if the CFL-
number is less than unity. By adopting this formulation, one can design various
solution methods in arbitrary dimensions that range from explicit to
unconditionally stable implicit methods in which CFL-number could reach
arbitrary large values. In addition, we find that adopting a specially varying
time stepping scheme accelerates convergence toward steady state solutions and
improves the efficiently of the solution procedure.


title:
Refraction in a pulsar magnetosphere - the effect of a variable emission
  height on pulse morphology

abstract:
  The Petrova (2000) model to calculate pulse profiles is extended to a
variable emission height model to make it physically self-consistent. In this
context variable means that the emission height is no longer considered to be
the same for different magnetic field lines. The pulse profiles calculated
using this new model seem to be less realistic due to a focusing effect and
cannot be used to fit (typical) multifrequency pulsar observations. Apart from
the focusing effect the general morphology of pulse profiles is not greatly
affected by introducing a variable emission height. Additional extensions of
the model will be needed to be able to fit observations, and several
suggestions are made.


title: Is the dark halo of our Galaxy spherical?

abstract:
  It has been recently claimed that the confined structure of the debris from
the Sagittarius dwarf implies that the dark-matter halo of our Galaxy should be
nearly spherical, in strong contrast with predictions from cold dark-matter
(CDM) simulations, where dark halos are found to have typical density axis
ratios of 0.6 - 0.8. In this letter, numerical simulations are used to show
that the Sagittarius streams discovered thus far are too young dynamically to
be sensitive to the shape of the dark halo of the Milky Way. The data presently
available are entirely consistent with a Galactic dark-matter halo that could
either be oblate or prolate, with minor-to-major density axis ratios c/a as low
as 0.6 within the region probed by the orbit of the Sagittarius dwarf.


title: The phase of the radio and X-ray pulses of PSR B1937+21

abstract:
  We present timing and spectral results of PSR B1937+21, the fastest known
millisecond pulsar (P about 1.56 ms), observed with RXTE. The pulse profile,
detected up to 20 keV, shows a double peak with the main component much
stronger than the other. The peak phase separation is 0.526 +/- 0.002 and the
pulsed spectrum over the energy range 2--25 keV is well described by a power
law with a photon index equal to 1.14 +/- 0.07. We find that the X-ray pulses
are closely aligned in phase with the giant pulses observed in the radio band.
This results suggest that giant radio pulses and X-ray pulses originate in the
same region of the magnetosphere due to a high and fluctuating electron density
that occasionally emits coherently in the radio band. The X-ray events,
however, do not show any clustering in time indicating that no X-ray flares are
produced.


title:
Theory and practice of microlensing lightcurves around fold
  singularities

abstract:
  Among all galactic microlensing events, those involving a passage of the
observed source star over the caustic created by a binary lens are particularly
useful in providing information about stellar atmospheres, the dynamics of
stellar populations in our own and neighbouring galaxies, and the statistical
properties of stellar and sub-stellar binaries. This paper presents a
comprehensive guide for modelling and interpreting the lightcurves obtained in
events involving fold-caustic crossings. A new general, consistent, and optimal
choice of parameters provides a deep understanding of the involved features,
avoids numerical difficulties and minimizes correlations between model
parameters. While the photometric data of a microlensing event around a caustic
crossing itself do not provide constraints on the characteristics of the
underlying binary lens and does not allow predictions of the behaviour of other
regions of the lightcurve, vital constraints can be obtained in an efficient
way if these are combined with a few simple characteristics of data outside the
caustic crossings. A corresponding algorithm containing some improvements over
an earlier approach which takes into account multi-site observations is
presented and discussed in detail together with the arising parameter
constraints paying special attention to the role of source and background
fluxes.


title:
Ni abundance in the core of the Perseus Cluster: an answer to the
  significance of resonant scattering

abstract:
  Using an XMM-Newton observation of the Perseus cluster we show that the
excess in the flux of the 7-8 keV line complex previously detected by ASCA and
BeppoSAX is due to an overabundance of Nickel rather than to an anomalously
high Fe He$\beta$/Fe He$\alpha$ ratio. This observational fact leads to the
main result that resonant scattering, which was assumed to be responsible for
the supposed anomalous Fe He$\beta$/Fe He$\alpha$ ratio, is no longer required.
The absence of resonant scattering points towards the presence of significant
gas motions (either turbulent or laminar) in the core of the Perseus cluster.


title: On the 3D dynamics and morphology of inner rings

abstract:
  We argue that inner rings in barred spiral galaxies are associated with
specific 2D and 3D families of periodic orbits located just beyond the end of
the bar. These are families located between the inner radial ultraharmonic 4:1
resonance and corotation. They are found in the upper part of a type-2 gap of
the x1 characteristic, and can account for the observed ring morphologies
without any help from families of the x1-tree. Due to the evolution of the
stability of all these families, the ring shapes that are favored are mainly
ovals, as well as polygons with `corners' on the minor axis, on the sides of
the bar. On the other hand pentagonal rings, or rings of the NGC 7020 type
hexagon, should be less probable. The orbits that make the rings belong in
their vast majority to 3D families of periodic orbits and orbits trapped around
them.


title: Study of galaxy cluster properties from high-resolution SPH simulations

abstract:
  We present some of the results of an ongoing collaboration to sudy the
dynamical properties of galaxy clusters by means of high resolution adiabatic
SPH cosmological simulations. Results from our numerical clusters have been
tested against analytical models often used in X-ray observations: $\beta$
model (isothermal and polytropic) and those based on universal dark matter
profiles. We find a universal temperature profile, in agreement with AMR
gasdynamical simulations of galaxy clusters. Temperature decreases by a factor
2-3 from the center to virial radius. Therefore, isothermal models (e.g.
$\beta$ model) give a very poor fit to simulated data. Moreover, gas entropy
profiles deviate from a power law near the center, which is also in very good
agreement with independent AMR simulations. Thus, if future X-ray observations
confirm that gas in clusters has an extended isothermal core, then
non-adiabatic physics would be required in order to explain it.


title: Search for extraterrestrial point sources of neutrinos with AMANDA-II

abstract:
  We present the results of a search for point sources of high energy neutrinos
in the northern hemisphere using AMANDA-II data collected in the year 2000.
Included are flux limits on several AGN blazars, microquasars, magnetars and
other candidate neutrino sources. A search for excesses above a random
background of cosmic-ray-induced atmospheric neutrinos and misreconstructed
downgoing cosmic-ray muons reveals no statistically significant neutrino point
sources. We show that AMANDA-II has achieved the sensitivity required to probe
known TeV gamma-ray sources such as the blazar Markarian 501 in its 1997
flaring state at a level where neutrino and gamma-ray fluxes are equal.


title:
Goodness-of-fit tests of Gaussianity: constraints on the cumulants of
  the MAXIMA data

abstract:
  In this work, goodness-of-fit tests are adapted and applied to CMB maps to
detect possible non-Gaussianity. We use Shapiro-Francia test and two Smooth
goodness-of-fit tests: one developed by Rayner and Best and another one
developed by Thomas and Pierce. The Smooth tests test small and smooth
deviations of a prefixed probability function (in our case this is the
univariate Gaussian). Also, the Rayner and Best test informs us of the kind of
non-Gaussianity we have: excess of skewness, of kurtosis, and so on. These
tests are optimal when the data are independent. We simulate and analyse
non-Gaussian signals in order to study the power of these tests. These
non-Gaussian simulations are constructed using the Edgeworth expansion, and
assuming pixel-to-pixel independence. As an application, we test the
Gaussianity of the MAXIMA data. Results indicate that the MAXIMA data are
compatible with Gaussianity. Finally, the values of the skewness and kurtosis
of MAXIMA data are constrained by |S| \le 0.035 and |K| \le 0.036 at the 99%
confidence level.


title: Kinematic Properties of the TDG Candidates of CG J1720-67.8

abstract:
  I use integral field and long-slit spectra from the AAT and the Magellan
telescope to investigate the kinematics of several clumps, recently identified
along the prominent tidal tail of CG J1720-67.8 and suggested as possile tidal
dwarf galaxy (TDG) candidates. A comparison of photometric and spectroscopic
data with evolutionary synthesis models suggests burst ages of ~ 6 Myr for
these clumps/TDG candidates.


title:
The Effects of Binary Evolution on the Dynamics of Core Collapse and
  Neutron-Star Kicks

abstract:
  We systematically examine how the presence in a binary affects the final core
structure of a massive star and its consequences for the subsequent supernova
explosion. Interactions with a companion star may change the final rate of
rotation, the size of the helium core, the strength of carbon burning and the
final iron core mass. Stars with initial masses larger than \sim 11\Ms that
experiece core collapse will generally have smaller iron cores at the time of
the explosion if they lost their envelopes due to a previous binary
interaction. Stars below \sim 11\Ms, on the other hand, can end up with larger
helium and metal cores if they have a close companion, since the second
dredge-up phase which reduces the helium core mass dramatically in single stars
does not occur once the hydrogen envelope is lost. We find that the initially
more massive stars in binary systems with masses in the range 8 - 11\Ms are
likely to undergo an electron-capture supernova, while single stars in the same
mass range would end as ONeMg white dwarfs. We suggest that the core collapse
in an electron-capture supernova (and possibly in the case of relatively small
iron cores) leads to a prompt explosion rather than a delayed neutrino-driven
explosion and that this naturally produces neutron stars with low-velocity
kicks. This leads to a dichotomous distribution of neutron star kicks, as
inferred previously, where neutron stars in relatively close binaries attain
low kick velocities. We illustrate the consequences of such a dichotomous kick
scenario using binary population synthesis simulations and discuss its
implications. This scenario has also important consequences for the minimum
initial mass of a massive star that becomes a neutron star. (Abbreviated.)


title:
The Relationship Between the Sersic Law Profiles Measured Along the
  Major and Minor Axes of Elliptical Galaxies

abstract:
  In this paper we discuss the reason why the parameters of the Sersic model
best-fitting the major axis light profile of elliptical galaxies can differ
significantly from those derived for the minor axis profile. We show that this
discrepancy is a natural consequence of the fact that the isophote eccentricity
varies with the radius of the isophote and present a mathematical
transformation that allows the minor axis Sersic model to be calculated from
the major axis model, provided that the elliptical isophotes are aligned and
concentric and that their eccentricity can be represented by a well behaved,
though quite general, function of the radius. When there is no variation in
eccentricity only the effective radius changes in the Sersic model, while for
radial-dependent eccentricity the transformation which allows the minor axis
Sersic model to be calculated from the major axis model is given by the Lerch
Phi transcendental function. The proposed transformation was tested using
photometric data for 28 early-type galaxies.


title: Models of Accretion Disks around Young Stars

abstract:
  We discuss the importance of accretion in calculating disk models for young
stellar objects. In particular, we show that a disk inner rim, irradiated by
both the star and the accretion shocks at the stellar surface, can naturally
explain recent observations of DG Tau with the Keck interferometer. We present
models for two objects, with mass accretion rates differing by almost two
orders of magnitude, to illustrate the effects of accretion on the overall disk
structure and emission.


title:
Simultaneous determination of $\Omega_{\rm M0}$ and $H_0$ from joint
  Sunyaev-Zeldovich effect and X-ray observations with median statistics

abstract:
  Clusters of galaxies contain a fair sample of the universal baryonic mass
fraction. A combined analysis of the intracluster medium (ICM) within their
hydrostatic regions, as derived from both Sunyaev-Zeldovich effect (SZE)
measurements and X-ray images, makes it possible to constrain the cosmological
parameters. We consider both gas fraction estimates and angular diameter
distance measurements. Adopting median statistics, we find, at the 2-$\sigma$
level, the pressureless matter density, $\Omega_{\rm M0}$, to be between 0.30
and 0.40 and the Hubble constant, $H_0$, between 44 and 66 Km s$^{-1}$
Mpc$^{-1}$.


title:
Local Interstellar Medium Kinematics towards the Southern Coalsack and
  Chamaeleon-Musca dark clouds

abstract:
  The results of a spectroscopic programme aiming to investigate the kinematics
of the local interstellar medium components towards the Southern Coalsack and
Chamaeleon-Musca dark clouds are presented. The analysis is based upon
high-resolution (R ~ 60,000) spectra of the insterstellar NaI D absorption
lines towards 63 B-type stars (d < 500 pc) selected to cover these clouds and
the connecting area defined by the Galactic coordinates: 308 > l > 294 and -22
< b < 5. The radial velocities, column densities, velocity dispersions, colour
excess and photometric distances to the stars are used to understand the
kinematics and distribution of the interstellar cloud components. The analysis
indicates that the interstellar gas is distributed in two extended sheet-like
structures permeating the whole area, one at d < 60 pc and another around
120-150 pc from the Sun. The dust and gas feature around 120-150 pc seem to be
part of an extended large scale feature of similar kinematic properties,
supposedly identified with the interaction zone of the Local and Loop I
bubbles.


title: Production of Massless Fermions during Inflation

abstract:
  We compute the one loop self energy, in a locally de Sitter background, for a
massless fermion which is Yukawa-coupled to a massless, minimally coupled
scalar. We then solve the modified Dirac equation resulting from inclusion of
the self energy. We find faster-than-exponential growth in the fermion wave
function, consistent with the production of fermions through a process in which
a scalar and a fermion-anti-fermion pair are ripped out of the vacuum by
inflation.


title: Singly-Peaked P-Cygni type Ly$\alpha$ from starburst galaxies

abstract:
  We present results of Monte Carlo calculations for the Lya line transfer in
an expanding dusty supershell, where Lya source is a well-localized star
cluster in a starburst galaxy.The escape of Lya photons from such system is
achieved by a number of back-scattering, and so a series of emission peaks are
formed redward of the systemic redshift by back-scattering. However, majority
of observed Lya emission from starbursts show singly-peaked asymmetric
profiles. We find in this paper that, in order to form a singly-peaked Lya
emission, dust should be distributed in the ionized bubble, as well as within
the supershell of neutral hydrogen. We also find that the overall escape
fraction of Lya photons is determined by the HI column density of the
supershell, the expansion velocity of the supershell, and the spatial
distribution of dust. However, the kinematic information of the expanding
supershell is preserved in the profile of Lya emission even when the supershell
is dusty. Our results are potentially useful to fit the P-Cygni type Lya line
profiles from starburst galaxies, either nearby galaxies or high-z Lyman break
galaxies (LBGs).


title:
The Nuclear Reddening Curve for Active Galactic Nuclei and the Shape of
  the Infra-Red to X-Ray Spectral Energy Distribution

abstract:
  We present extinction curves derived from the broad emission lines and
continua of large samples of both radio-loud and radio-quiet AGNs. The curves
are significantly flatter in the UV than are curves for the local ISM. The
reddening curves for the radio-quiet LBQS quasars are slightly steeper than
those of the radio-loud quasars in the UV, probably because of additional
reddening by dust further out in the host galaxies of the former. The UV
extinction curves for the radio-loud AGNs are very flat. This is explicable
with slight modifications to standard MRN dust models: there is a relative lack
of small grains in the nuclear dust. Our continuum and broad-emission line
reddening curves agree in both shape and amplitude, confirming that the
continuum shape is indeed profoundly affected by reddening for all but the
bluest AGNs. With correction by our generic extinction curve, all of the
radio-loud AGNs have continuous optical-UV spectra consistent with a single
shape. We show that radio-quiet AGNs have very similar intrinsic UV to optical
shape over orders of magnitude in luminosity. We also argue that radio-loud and
radio-quiet AGNs probably share the same underlying continuum shape and that
most of the systematic differences between their observed continuum shapes are
due to higher nuclear reddening in radio-selected AGNs, and additional
reddening from dust further out in the host galaxies in radio-quiet AGNs. Our
conclusions have important implications for the modelling of quasar continua
and the analysis of quasar demographics.


title: A 3D Optical Spectroscopy Study of Low Surface Brightness Galaxies

abstract:
  We present Halpha emission line velocity fields of two Low Surface Brightness
galaxies - UGC 628 and UGC 5005 - obtained using Fabry-Perot interferometry
observations at the Canada-France-Hawaii telescope. Our goal is to study the
dynamics of Low Surface Brightness galaxies.


title: Exploring spiral galaxy potentials with hydrodynamical simulations

abstract:
  We study how well the complex gas velocity fields induced by massive spiral
arms are modelled by the hydrodynamical simulations we used to constrain the
dark matter fraction in nearby spiral galaxies (Kranz et al. 2001, 2003). More
specifically, we explore the dependence of the positions and amplitudes of
features in the gas flow on the temperature of the interstellar medium (assumed
to behave as a one-component isothermal fluid), the non-axisymmetric disk
contribution to the galactic potential, the pattern speed, Omega_p, and finally
the numerical resolution of the simulation. We argue that, after constraining
the pattern speed reasonably well by matching the simulations to the observed
spiral arm morphology, the amplitude of the non-axisymmetric perturbation (the
disk fraction) is left as the primary parameter determining the gas dynamics.
However, due to the sensitivity of the positions of the shocks to modeling
parameters, one has to be cautious when quantitatively comparing the
simulations to observations. In particular, we show that a global least squares
analysis is not the optimal method for distinguishing different models as it
tends to slightly favor low disk fraction models. Nevertheless, we conclude
that, given observational data of reasonably high spatial resolution and an
accurate shock-resolving hydro-code this method tightly constrains the dark
matter content within spiral galaxies. We further argue that even if the
perturbations induced by spiral arms are weaker than those of strong bars, they
are better suited for this kind of analysis because the spiral arms extend to
larger radii where effects like inflows due to numerical viscosity and
morphological dependence on gas sound speed are less of a concern than they are
in the centers of disks.


title: Massive Stars: Their Birth Sites and Distribution

abstract:
  The stellar IMF has been found to be an invariant Salpeter power-law
(alpha=2.35) above about 1 Msun, but at the same time a massive star typically
has more than one companion. This constrains the possible formation scenarios
of massive stars, but also implies that the true, binary-star corrected stellar
IMF could be significantly steeper than Salpeter, alpha>2.7. A significant
fraction of all OB stars are found relatively far from potential birth sites
which is most probably a result of dynamical ejections from cores of
binary-rich star clusters. Such cores form rapidly due to dynamical mass
segregation, or they are primordial. Probably all OB stars thus form in stellar
clusters together with low-mass stars, and they have a rather devastating
effect on the embedded cluster by rapidly driving out the remaining gas leaving
expanding OB associations and bound star clusters. The distributed population
of OB stars has a measured IMF with alpha about 4, which however, does not
necessarily constitute a different physical mode for isolated star formation. A
steep field-star IMF is obtained naturally because stars form in clusters which
are distributed according to a power-law cluster mass function.


title: A Moving Frame Algorithm for High Mach Number Hydrodynamics

abstract:
  We present a new approach to Eulerian computational fluid dynamics that is
designed to work at high Mach numbers encountered in astrophysical hydrodynamic
simulations. The Eulerian fluid conservation equations are solved in an
adaptive frame moving with the fluid where Mach numbers are minimized. The
moving frame approach uses a velocity decomposition technique to define local
kinetic variables while storing the bulk kinetic components in a smoothed
background velocity field that is associated with the grid velocity.
Gravitationally induced accelerations are added to the grid, thereby minimizing
the spurious heating problem encountered in cold gas flows. Separately tracking
local and bulk flow components allows thermodynamic variables to be accurately
calculated in both subsonic and supersonic regions. A main feature of the
algorithm, that is not possible in previous Eulerian implementations, is the
ability to resolve shocks and prevent spurious heating where both the preshock
and postshock Mach numbers are high. The hybrid algorithm combines the high
resolution shock capturing ability of the second-order accurate Eulerian TVD
scheme with a low-diffusion Lagrangian advection scheme. We have implemented a
cosmological code where the hydrodynamic evolution of the baryons is captured
using the moving frame algorithm while the gravitational evolution of the
collisionless dark matter is tracked using a particle-mesh N-body algorithm.
The MACH code is highly suited for simulating the evolution of the IGM where
accurate thermodynamic evolution is needed for studies of the Lyman alpha
forest, the Sunyaev-Zeldovich effect, and the X-ray background. Hydrodynamic
and cosmological tests are described and results presented. The current code is
fast, memory-friendly, and parallelized for shared-memory machines.


title:
Hierarchical Structure Formation and Chemical Evolution of Damped Ly
  alpha Systems

abstract:
  We present a model for chemical evolution of damped Ly alpha systems
considering production of metals by SNe II and infall associated with
hierarchical structure formation. The growth of metallicity in these systems is
a reflection of the competition between astration and infall. The apparent late
turn-on of these systems is due to the late cut-off of infall. The wide range
in [Fe/H] at a given redshift is explained by the range of the times for onset
of star formation and the range of the times for infall cessation in different
systems. The observed lower bound of [Fe/H] = -3 follows from the very rapid
initial rise of [Fe/H] subsequent to onset of star formation. To reach [Fe/H] =
-3 from a metal-free initial state requires only about 30 Myr so that the
probability of observing lower [Fe/H] values is very small.


title: Star Formation in Satellite Galaxies

abstract:
  The study of satellite galaxies can provide information on the merging and
aggregation processes which, according to the hierarchical clustering models,
form the larger spiral galaxies we observe. With the aim of testing
hierarchical models of galaxy formation, we have conducted an observational
program which comprises H$\alpha$ imaging for both the parent and the satellite
galaxies, taken from the compilation by Zaritsky et al. (1997) that contains
115 galaxies orbiting 69 primary isolated spiral galaxies. We have observed a
subsample of 37 spiral and irregular galaxies taken from the compilation
mentioned above. The aim of this study is to determine star formation
properties of the sample galaxies. In this work we present the preliminary
results of this program that we have carried out with the 1.8-m Vatican
Telescope (VATT).


title: Intergalactic Globular Clusters

abstract:
  We confirm and extend our previous detection of a population of intergalactic
globular clusters in Abell 1185, and report the first discovery of an
intergalactic globular cluster in the nearby Virgo cluster of galaxies. The
numbers, colors and luminosities of these objects can place constraints on
their origin, which in turn may yield new insights to the evolution of galaxies
in dense environments.


title:
Systematic variation of the residual of PSR B1937+21, the trace of its
  companion star?

abstract:
  PSR B1937+21 was the first millisecond pulsar ever measured. Which has been
appeared as a singular pulsar. The high-precision observation of this pulsar
shows systemic long-term variation in the residual of time of arrivals. This
paper modelled the secular variation by the orbital precession induced time
delay of a binary pulsar system. The fitting requires that as a binary pulsar,
PSR B1937+21 should have small companion star, $m_2\sim 10^{-2}M_{\odot}$, and
projected semi-major axis, $x\sim 10^{-4}$s to $10^{-3}$s. Which corresponds to
ignorable radial velocity of the pulsar to the line of sight. This might
explain why it has been measured as a singular pulsar instead of a binary
pulsar.


title:
Does the Iron K$_{\alpha}$ Line of Active Galactic Nuclei Arise from the
  Cerenkov Line-like Radiation?

abstract:
  When thermal relativistic electrons with isotropic distribution of velocities
move in a gas region, or impinge upon the surface of a cloud that consists of a
dense gas or doped dusts, the Cerenkov effect produces peculiar atomic or ionic
emission lines -- the Cerenkov line-like radiation. This newly recognized
emission mechanism may find wide applications in high-energy astrophysics. In
this paper, we tentatively adopt this new line emission mechanism to discuss
the origin of iron K$_{\alpha}$ feature of AGNs. Motivation of this research is
to attempt a solution to a problem encountered by the ``disk-fluorescence
line'' model, i.e. the lack of temporal response of the observed iron
K$_{\alpha}$ line flux to the changes of the X-ray continuum flux. If the
Cerenkov line emission is indeed responsible significantly for the iron
K$_{\alpha}$ feature, the conventional scenario around the central supermassive
black holes of AGNs would need to be modified to accommodate more energetic,
more violent and much denser environments than previously thought.


title:
Distribution of Faraday Rotation Measure in Jets from Active Galactic
  Nuclei I. Prediction from our Sweeping Magnetic Twist Model

abstract:
  Using the numerical data of MHD simulation for AGN jets based on our
``sweeping magnetic twist model'', we calculated the Faraday rotation measure
(FRM) and the Stokes parameters to compare with observations. We propose that
the FRM distribution can be used to discuss the 3-dimensional structure of
magnetic field around jets, together with the projected magnetic field derived
from the Stokes parameters. In the present paper, we supposed the basic
straight part of AGN jet, and used the data of axisymmetric simulation. The FRM
distribution we derived has a general tendency to have gradient across the jet
axis, which is due to the toroidal component of the helical magnetic field
generated by the rotation of the accretion disk. This kind of gradient in the
FRM distribution is actually observed in some AGN jets (e.g. Asada et al.
2002), which suggests helical magnetic field around the jets and thus supports
our MHD model. Following this success, we are now extending our numerical
observation to the wiggled part of the jets using the data of 3-dimensional
simulation based on our model in the following paper.


title: An XMM-Newton Study of the Hard X-ray Sky

abstract:
  We report on the spectral properties of a sample of 90 hard X-ray selected
serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80
10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified
with 0.1<z<2 and most of them are classified as broad line AGNs. A simple model
consisting of power law modified by Galactic absorption offers an acceptable
fit to ~65% of the source spectra. This fit yields an average photon index of
<Gamma>~1.55 over the whole sample. We also find that the mean slope of the
QSOs in our sample turns out to remain nearly constant (<Gamma>~1.8-1.9)
between 0<z<2, with no hints of particular trends emerging along z. An
additional cold absorption component with 10^(21)<Nh<10^(23) cm^(-2) is
required in ~30% of the sources. Considering only subsamples that are complete
in flux, we find that the observed fraction of absorbed sources (i.e. with
Nh>~10^(22) cm^(-2)) is ~30%, with little evolution in the range 2<F(2-10)<80
10^(-14) erg/cm2/s. Interestingly, this value is a factor ~2 lower than
predicted by the synthesis models of the CXB. This finding, detected for the
first time in this survey, therefore suggests that most of the heavily obscured
objects which make up the bulk of the CXB will be found at lower fluxes
(F(2-10)< 10^(-14) erg/cm2/s). This mismatch together with other recent
observational evidences which contrast with CXB model predictions suggest that
one (or more) of the assumptions usually included in these models need to be
revised.


title: Determining the abundance of extragalactic planets

abstract:
  Gravitational microlensing provides a unique technique to reveal information
about extragalactic planets. A network of at least four 2m-class telescopes
distributed around the northern hemisphere could probe 15-35 jupiters and 4-10
saturns around M31 stars per year.


title:
Inflationary slow-roll formalism and perturbations in the
  Randall-Sundrum Type II braneworld

abstract:
  We formalize the Hubble slow-roll formalism for inflationary dynamics in
Randall-Sundrum Type II braneworld cosmologies, defining Hubble slow-roll
parameters which can be used along with the Hamilton-Jacobi formalism.
Focussing on the high-energy limit, we use these to calculate the exact power
spectrum for power-law inflation, and then perturb around this solution to
derive the higher-order expression for the density perturbations (sometimes
called the Stewart-Lyth correction) of slow-roll braneworld models. Finally we
apply our result to specific examples of potentials to calculate the correction
to the amplitude of the power spectrum, and compare it with the standard
cosmology. We find that the amplitude is not changed significantly by the
higher-order correction.


title:
The PLANET microlensing campaign: Implications for planets around
  galactic disk and bulge stars

abstract:
  With round-the-clock monitoring of galactic bulge microlensing events, the
PLANET experiment constrains the abundance and can yield the discovery of
planets down to the mass of earth around galactic disk and bulge stars. Data
taken until 1999 imply that less than 1/3 of bulge M-dwarfs are surrounded by
jupiter-mass companions at orbital radii between 1 and 4 AU. The current rate
of microlensing alerts allows 15-25 jupiters and 1-3 earths to be probed per
year.


title: Scientific optimization of a ground-based CMB polarization experiment

abstract:
  We investigate the science goals achievable with the upcoming generation of
ground-based Cosmic Microwave Background polarization experiments and calculate
the optimal sky coverage for such an experiment including the effects of
foregrounds. We find that with current technology an E-mode measurement will be
sample-limited, while a B-mode measurement will be detector-noise-limited. We
conclude that a 300 sq deg survey is an optimal compromise for a two-year
experiment to measure both E and B-modes, and that ground-based polarization
experiments can make an important contribution to B-mode surveys. Focusing on
one particular experiment, QUaD, a proposed bolometric polarimeter operating
from the South Pole, we find that a ground-based experiment can make a high
significance measurement of the acoustic peaks in the E-mode spectrum, and will
be able to detect the gravitational lensing signal in the B-mode spectrum. Such
an experiment could also directly detect the gravitational wave component of
the B-mode spectrum if the amplitude of the signal is close to current upper
limits. We also investigate how a ground-based experiment can improve
constraints on the cosmological parameters. We estimate that by combining two
years of QUaD data with the four-year WMAP data, an optimized ground-based
polarization experiment can improve constraints on cosmological parameters by a
factor of two. If the foreground contamination can be reduced, the measurement
of the tensor-to-scalar ratio can be improved by up to a factor of six over
that obtainable from WMAP alone.


title: Orbital Parameters of Merging Dark Matter Halos

abstract:
  In order to specify cosmologically motivated initial conditions for major
galaxy mergers (mass ratios $\leq$ 4:1) that are supposed to explain the
formation of elliptical galaxies we study the orbital parameters of major
mergers of cold dark matter halos using a high-resolution cosmological
simulation. Almost half of all encounters are nearly parabolic with
eccentricities $e \approx 1$ and no correlations between the halo spin planes
or the orbital planes. The pericentric argument $\omega$ shows no correlation
with the other orbital parameters and is distributed randomly. In addition we
find that 50 % of typical pericenter distances are larger than half the halo's
virial radii which is much larger than typically assumed in numerical
simulations of galaxy mergers. In contrast to the usual assumption made in
semi-analytic models of galaxy formation the circularities of major mergers are
found to be not randomly distributed but to peak around a value of $\epsilon
\approx 0.5$. Additionally all results are independent of the minimum
progenitor mass and major merger definitions (i.e. mass ratios $\leq$ 4:1; 3:1;
2:1).


title: The Luminosity Function of Cluster Radio Relics

abstract:
  In this paper we compute the luminosity function of radio relics. In our
calculation we include only those relics that are produced by the compression
of former radio cocoons. This compression is provided by shocks that are
generated in the process of structure formation. Starting from an analytical
model for the luminosity evolution of ageing radio cocoons, the luminosity
function of radio galaxies and the statistics of shocks as inferred from
cosmological simulations, we are able to make the first estimates of the
brightness distribution of radio relics. The computed luminosity function is
consistent with current observations and predicts that more than $10^3$ radio
relics should be discovered with the upcoming generation of low-frequency radio
telescopes. Moreover, we predict that radio relics are predominantly found in
low-pressure regions outside the cores of clusters.


title: The behaviour of quiescent accretion discs in dwarf novae

abstract:
  We propose a simple explanation for the constant mean brightness observed
between outbursts in dwarf novae. Secular changes in the total energy
dissipation rate of the accretion disc brought about by variations in surface
density, temperature and disc radius can be regulated by the gradual cooling of
a small, critically-stable hot inner region. The hypothesis is supported by
two-dimensional time-dependent numerical models of dwarf nova accretion discs.


title:
The Effects of Age on Red Giant Metallicities Derived from the
  Near-Infrared Ca II Triplet

abstract:
  We have obtained spectra with resolution 2.5 Angstroms in the region
7500-9500 Angstroms for 116 red giants in 5 Galactic globular clusters and 6
old open clusters (5 with published metallicities, and one previously
unmeasured). The signal-to-noise ranges from 20 to 85. We measure the
equivalent widths of the infrared Ca II triplet absorption lines in each stars
and compare to cluster metallicities taken from the literature. With globular
cluster abundances on the Carretta & Gratton scale, and open cluster abundances
taken from the compilation of Friel and collaborators, we find a linear
relation between [Fe/H] and Ca II line strength spanning the range -2 < [Fe/H]
< -0.2 and ages from 2.5 - 13 Gyr. No evidence for an age effect on the
metallicity calibration is observed. Using this calibration, we find the
metallicity of the old open cluster Trumpler 5 to be [Fe/H] = -0.56 +/-0.11.
Considering the 10 clusters of known metallicity shifted to a common distance
and reddening, we find that the additional metallicity error introduced by the
variation of horizontal branch/red clump magnitude with metallicity and age is
of order +/-0.05 dex, which can be neglected in comparison to the intrinsic
scatter in our method. The results are discussed in the context of abundance
determinations for red giants in Local Group galaxies.


title: BeppoSAX observations of rotation-powered pulsars

abstract:
  During its life, BeppoSAX observed several isolated pulsars, giving important
contributions to the knowledge of the phenomenology and properties of the X-ray
emission from this class of sources. In this paper I review the spectral and
timing results obtained from BeppoSAX observations. In particular, results on
three Crab-like (Crab, PSR B1509-58 and PSR B0540-69) and 3 millisecond pulsars
(PSR J0218+42, PSR B1821-24 and PSR B1937+21) are reported.


title: Differential rotation in rapidly rotating F-stars

abstract:
  We obtained high quality spectra of 135 stars of spectral types F and later
and derived ``overall'' broadening functions in selected wavelength regions
utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of
the projected rotational velocity $v \sin{i}$ were derived from the first zero
of the Fourier transformed profiles and the shapes of the profiles were
analyzed for effects of differential rotation. The broadening profiles of 70
stars rotating faster than $v \sin{i} =
  45$ km s$^{-1}$ show no indications of multiplicity nor of spottedness. In
those profiles we used the ratio of the first two zeros of the Fourier
transform $q_2/q_1$ to search for deviations from rigid rotation. In the vast
majority the profiles were found to be consistent with rigid rotation. Five
stars were found to have flat profiles probably due to cool polar caps, in
three stars cuspy profiles were found. Two out of those three cases may be due
to extremely rapid rotation seen pole on, only in one case ($v \sin{i} = 52$ km
s$^{-1}$) solar-like differential rotation is the most plausible explanation
for the observed profile. These results indicate that the strength of
differential rotation diminishes in stars rotating as rapidly as $v \sin{i} \ga
50$ km s$^{-1}$.


title: MOND and the "Dearth of Dark Matter in Ordinary Elliptical Galaxies"

abstract:
  The recent findings of Romanowsky et al., of an ``unexpectedly'' small mass
discrepancy within 5 effective radii in several elliptical galaxies, are not
surprising in the context of MOND. As we show here, they are, in fact, in full
concordance with its predictions. One is dealing with high-surface-density
galaxies with mean accelerations rather larger than the acceleration constant
of MOND. These findings continue, and are now the extreme examples of, the
trend predicted by MOND: the mass discrepancy sets in at larger and larger
scaled radii in galaxies with larger and larger mean surface densities; or,
equivalently, mean accelerations.


title: The single degenerate channel for the progenitors of type Ia supernovae

abstract:
  We have carried out a detailed study of one of the most popular evolutionary
channels for the production of Type Ia supernova (SN Ia) progenitors, the
semi-degenerate channel (CO+MS), where a carbon/oxygen (CO) white dwarf (WD)
accretes matter from an unevolved or slightly evolved non-degenerate star until
it reaches the Chandrasekhar mass limit. Employing Eggleton's stellar evolution
code and adopting the prescription of Hachisu et al. (1999) for the accretion
efficiency, we have carried out full binary evolution calculations for about
2300 close WD binary systems and mapped out the initial parameters in the
orbital period -- secondary mass ($P$--$M_2$) plane (for a range of WD masses)
which lead to a successful Type Ia supernova. We obtained accurate, analytical
fitting formulae to describe this parameter range which can be used for binary
population synthesis (BPS) studies. The contours in the $P$--$M_2$ plane differ
from those obtained by Hachisu et al. (1999) for low-mass CO WDs, which are
more common than massive CO WDs. We show that white dwarfs with a mass as low
as $0.67M_\odot$ can accrete efficiently and reach the Chandrasekhar limit. We
have implemented these results in a BPS study to obtain the birthrates for SNe
Ia and the evolution of birthrates with time of SNe Ia for both a constant star
formation rate and a single star burst. The birthrates are somewhat lower than
(but comparable to) those inferred observationally.


title:
Carbon star survey in the Local Group. VII. NGC 3109 a galaxy without a
  stellar halo

abstract:
  We present a CFH12K wide field survey of the carbon star population in and
around NGC 3109. Carbon stars, the brightest members of the intermediate-age
population, were found nearly exclusively in and near the disk of NGC 3109,
ruling out the existence of an extensive intermediate-age halo like the one
found in NGC 6822. Over 400 carbon stars identified have < M_I > = -4.71,
confirming the nearly universality of mean magnitude of C star populations in
Local Group galaxies. Star counts over the field reveal that NGC 3109 is a
truncated disk shaped galaxy without an extensive stellar halo. The minor axis
star counts reach the foreground density between 4' and 5', a distance that can
be explained by an inclined disk rather than a spheroidal halo. We calculate a
global C/M ratio of 1.75 +/- 0.20, a value expected for such a metal poor
galaxy.


title:
The Nuclear Region of Low Luminosity Flat Radio Spectrum Sources. II.
  Emission-Line Spectra

abstract:
  We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum
(LL FRS) sources selected from Marcha's et al. (1996) 200 mJy sample. In the
optical, these objects are mainly dominated by the host galaxy starlight. After
correcting the data for this effect, we obtain a new set of spectra clearly
displaying weak emission lines; such features carry valuable information
concerning the excitation mechanisms at work in the nuclear regions of LL FRS
sources. We have used a special routine to model the spectra and assess the
intensities and velocities of the emission lines; we have analyzed the results
in terms of diagnostic diagrams. Our analysis shows that 79% of the studied
objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose
contribution was swamped by the host galaxy starlight. The remaining objects
display a higher ionization spectrum, more typical of Seyferts; due to the poor
quality of the spectra, it was not possible to identify any possible large
Balmer components. The fact that we observe a LINER-type spectrum in LL FRS
sources supports the idea that some of these objects could be undergoing an
ADAF phase; in addition, such a low ionization emission-line spectrum is in
agreement with the black hole mass values and sub-Eddington accretion rates
published for some FRS sources.


title: The power spectrum of SUSY-CDM on sub-galactic scales

abstract:
  The formation of large scale structure is independent of the nature of the
cold dark matter (CDM), however the fate of very small scale inhomogeneities
depends on the micro-physics of the CDM particles. We investigate the matter
power spectrum for scales that enter the Hubble radius well before
matter-radiation equality, and follow its evolution until the time when the
first inhomogeneities become non-linear. Our focus lies on weakly interacting
massive particles (WIMPs), and as a concrete example we analyze the case when
the lightest supersymmetric particle is a bino. We show that collisional
damping and free-streaming of WIMPs lead to a matter power spectrum with a
sharp cut-off at about 10^(-6) M_odot and a maximum close to that cut-off. We
also calculate the transfer function for the growth of the inhomogeneities in
the linear regime. These three effects (collisional damping, free-streaming and
gravitational growth) are combined to provide a WMAP normalized primordial CDM
power spectrum, which could serve as an input for high resolution CDM
simulations. The smallest inhomogeneities typically enter the non-linear regime
at a redshift of about 60.


title:
Radio Emission from Cosmic Ray Air Showers: Coherent Geosynchrotron
  Radiation

abstract:
  Cosmic ray air showers have been known for over 30 years to emit pulsed radio
emission in the frequency range from a few to a few hundred MHz, an effect that
offers great opportunities for the study of extensive air showers with upcoming
fully digital "software radio telescopes" such as LOFAR and the enhancement of
particle detector arrays such as KASCADE Grande or the Pierre Auger
Observatory. However, there are still a lot of open questions regarding the
strength of the emission as well as the underlying emission mechanism.
Accompanying the development of a LOFAR prototype station dedicated to the
observation of radio emission from extensive air showers, LOPES, we therefore
take a new approach to modeling the emission process, interpreting it as
"coherent geosynchrotron emission" from electron-positron pairs gyrating in the
earth's magnetic field. We develop our model in a step-by-step procedure
incorporating increasingly realistic shower geometries in order to disentangle
the coherence effects arising from the different scales present in the air
shower structure and assess their influence on the spectrum and radial
dependence of the emitted radiation. We infer that the air shower "pancake"
thickness directly limits the frequency range of the emitted radiation, while
the radial dependence of the emission is mainly governed by the intrinsic
beaming cone of the synchrotron radiation and the superposition of the emission
over the air shower evolution as a whole. Our model succeeds in reproducing the
qualitative trends in the emission spectrum and radial dependence that were
observed in the past, and is consistent with the absolute level of the emission
within the relatively large systematic errors in the experimental data.


title: Halos around edge-on disk galaxies in the SDSS

abstract:
  We present a statistical analysis of halo emission for a sample of 1047
edge-on disk galaxies imaged in five bands by the Sloan Digital Sky Survey
(SDSS). Stacking the homogeneously rescaled images of the galaxies, we can
measure surface brightnesses as deep as mu_r~31 mag/arcsec^2. The results
strongly support the almost ubiquitous presence of stellar halos around disk
galaxies, whose spatial distribution is well described by a power-law
$\rho\propto r^{-3}$, in a moderately flattened spheroid (c/a~0.6). The colour
estimates in g-r and r-i, although uncertain, give a clear indication for
extremely red stellar populations, hinting at old ages and/or non-negligible
metal enrichment. These results support the idea of halos being assembled via
early merging of satellite galaxies.


title: Long Term Profile Variability of Double-Peaked Emission Lines in AGNs

abstract:
  An increasing number of AGNs exhibit broad, double-peaked Balmer emission
lines, which are thought to arise from the outer regions of the accretion disk
which fuels the AGN. The line profiles are observed to vary on a characteristic
timescales of 5-10 years. The variability is not a reverberation effect; it is
a manifestation of physical changes in the disk. Our group has monitored a set
of 20 double-peaked emitters for the past 8 years (longer for some objects).
Here, we characterize the variability of the double-peaked H alpha line
profiles in five objects from our sample. By experimenting with simple models,
we find that disks with a single precessing spiral arm are able to reproduce
many of the variability trends that are seen in the data.