title: Are GRB 980425 and GRB 031203 real outliers or twins of GRB 060218?

abstract:
  GRB 980425 and GRB 031203 are apparently two outliers with respect to the
correlation between the isotropic equivalent energy E_iso emitted in the prompt
radiation phase and the peak frequency E_peak of the spectrum in a vF(v)
representation (the so-called Amati relation). We discuss if these two bursts
are really different from the others or if their location in the E_iso-E_peak
plane is the result of other effects, such as viewing them off-axis, or through
a scattering screen, or a misinterpretation of their spectral properties. The
latter case seems particularly interesting after GRB 060218, that, unlike GRB
031203 and GRB 980425, had a prompt emission detected both in hard and soft
X-rays which lasted ~2800 seconds. This allowed to determine its E_peak and
total emitted energy. Although it shares with GRB 031203 the total energetics,
it is not an outlier with respect to the Amati correlation. We then investigate
if a hard-to-soft spectral evolution in GRB 031203 and GRB 980425, consistent
with all the observed properties, can give rise to a time integrated spectrum
with an E_peak consistent with the Amati relation.


title: No Astrophysical Dyadospheres

abstract:
  It is shown how pair production itself would prevent the astrophysical
formation of dyadospheres, hypothetical regions where the electric field
exceeds the critical value for rapid Schwinger pair production. Pair production
is a self-regulating process that would discharge a growing electric field, in
the example of a hypothetical collapsing charged stellar core, before it
reached 6% of the minimum dyadosphere value, keeping the pair production rate
more than 26 orders of magnitude below the dyadosphere value, and keeping the
efficiency below 0.0002(M/M_sun)^{1/2}.


title:
Differential Radial Velocities and Stellar Parameters of Nearby Young
  Stars

abstract:
  Radial velocity searches for substellar mass companions have focused
primarily on stars older than 1 Gyr. Increased levels of stellar activity in
young stars hinders the detection of solar system analogs and therefore there
has been a prejudice against inclusion of young stars in radial velocity
surveys until recently. Adaptive optics surveys of young stars have given us
insight into the multiplicity of young stars but only for massive, distant
companions. Understanding the limit of the radial velocity technique,
restricted to high-mass, close-orbiting planets and brown dwarfs, we began a
survey of young stars of various ages. While the number of stars needed to
carry out full analysis of the problems of planetary and brown dwarf population
and evolution is large, the beginning of such a sample is included here. We
report on 61 young stars ranging in age from beta Pic association (~12 Myr) to
the Ursa Majoris association (~300 Myr). This initial search resulted in no
stars showing evidence for companions greater than ~1-2 M_Jup in short period
orbits at the 3 sigma-level. Additionally, we present derived stellar
parameters, as most have unpublished values. The chemical homogeneity of a
cluster, and presumably of an association, may help to constrain true
membership. As such, we present [Fe/H] abundances for the stars in our sample.


title: Dyadospheres Don't Develop

abstract:
  Pair production itself prevents the development of dyadospheres, hypothetical
macroscopic regions where the electric field exceeds the critical Schwinger
value. Pair production is a self-regulating process that would discharge a
growing electric field, in the example of a hypothetical collapsing charged
stellar core, before it reached 6% of the minimum dyadosphere value, keeping
the pair production rate more than 26 orders of magnitude below the dyadosphere
value.


title:
The Birth of Molecular Clouds: Formation of Atomic Precursors in
  Colliding Flows

abstract:
  Molecular Cloud Complexes (MCCs) are highly structured and ``turbulent''.
Observational evidence suggests that MCCs are dynamically dominated systems,
rather than quasi-equilibrium entities. The observed structure is more likely a
consequence of the formation process rather than something that is imprinted
after the formation of the MCC. Converging flows provide a natural mechanism to
generate MCC structure. We present a detailed numerical analysis of this
scenario. Our study addresses the evolution of a MCC from its birth in
colliding atomic hydrogen flows up until the point when H$_2$ may begin to
form. A combination of dynamical and thermal instabilities breaks up coherent
flows efficiently, seeding the small-scale non-linear density perturbations
necessary for local gravitational collapse and thus allowing (close to)
instantaneous star formation. Many observed properties of MCCs come as a
natural consequence of this formation scenario. Since converging flows are
omnipresent in the ISM, we discuss the general applicability of this mechanism,
from local star formation regions to galaxy mergers.


title: A simple model for the size-evolution of elliptical galaxies

abstract:
  We use semi-analytical modelling of galaxy formation to predict the
redshift-size-evolution of elliptical galaxies. Using a simple model in which
relative sizes of elliptical galaxies of a given mass correlate with the
fraction of stars formed in a star burst during a major merger event, we are
able to reproduce the observed size redshif t evolution. The size evolution is
a result of the amount of cold gas available during the major merger. Mergers
at high redshifts are gas-rich and produce ellipticals with smaller sizes. In
particular we find a power-law relation between the sizes at different
redshifts, with the power-law index giving a measure of the relative amount of
dissipation during the mergers that lead to the formation of an elliptical. The
size evolution is found to be stronger for more massive galaxies as they
involve more gas at high redshifts when they form compared to less massive
ellipticals. Local ellipticals more massive than $5 \times 10^{11}$ M$_{\odot}$
will be approximately 4 times larger than their counterparts at $z=2$. Our
results indicate that the scatter in the size of similar massive present day
elliptical galaxies is a result of their formation epoch, with smaller
ellipticals being formed earlier.


title: First Detection of HCO+ Emission at High Redshift

abstract:
  We report the detection of HCO+(1-0) emission towards the Cloverleaf quasar
(z=2.56) through observations with the Very Large Array. This is the first
detection of ionized molecular gas emission at high redshift (z>2). HCO+
emission is a star formation indicator similar to HCN, tracing dense molecular
hydrogen gas (n(H_2) ~= 10^5 cm^{-3}) within star-forming molecular clouds. We
derive a lensing-corrected HCO+ line luminosity of L'(HCO+) = 3.5 x 10^9 K km/s
pc^2. Combining our new results with CO and HCN measurements from the
literature, we find a HCO+/CO luminosity ratio of 0.08 and a HCO+/HCN
luminosity ratio of 0.8. These ratios fall within the scatter of the same
relationships found for low-z star-forming galaxies. However, a HCO+/HCN
luminosity ratio close to unity would not be expected for the Cloverleaf if the
recently suggested relation between this ratio and the far-infrared luminosity
were to hold. We conclude that a ratio between HCO+ and HCN luminosity close to
1 is likely due to the fact that the emission from both lines is optically
thick and thermalized and emerges from dense regions of similar volumes. The
CO, HCN and HCO+ luminosities suggest that the Cloverleaf is a composite
AGN--starburst system, in agreement with the previous finding that about 20% of
the total infrared luminosity in this system results from dust heated by star
formation rather than heating by the AGN. We conclude that HCO+ is potentially
a good tracer for dense molecular gas at high redshift.


title: Penetrating the Deep Cover of Compton Thick Active Galactic Nuclei

abstract:
  We analyze observations obtained with the Chandra X-ray Observatory of bright
Compton thick active galactic nuclei (AGNs), those with column densities in
excess of 1.5 x 10^{24} cm^{-2} along the lines of sight. We therefore view the
powerful central engines only indirectly, even at X-ray energies. Using high
spatial resolution and considering only galaxies that do not contain
circumnuclear starbursts, we reveal the variety of emission AGNs alone may
produce. Approximately 1% of the continuum's intrinsic flux is detected in
reflection in each case. The only hard X-ray feature is the prominent Fe K
alpha fluorescence line, with equivalent width greater than 1 keV in all
sources. The Fe line luminosity provides the best X-ray indicator of the unseen
intrinsic AGN luminosity. In detail, the morphologies of the extended soft
X-ray emission and optical line emission are similar, and line emission
dominates the soft X-ray spectra. Thus, we attribute the soft X-ray emission to
material that the central engines photoionize. Because the resulting spectra
are complex and do not reveal the AGNs directly, crude analysis techniques such
as hardness ratios would mis-classify these galaxies as hosts of intrinsically
weak, unabsorbed AGNs and would fail to identify the luminous, absorbed nuclei
that are present. We demonstrate that a three-band X-ray diagnostic can
correctly classify Compton thick AGNs, even when significant soft X-ray line
emission is present. The active nuclei produce most of the galaxies' total
observed emission over a broad spectral range, and much of their light emerges
at far-infrared wavelengths. Stellar contamination of the infrared emission can
be severe, however, making long-wavelength data alone unreliable indicators of
the buried AGN luminosity.


title: The 21cm Signature of the First Stars

abstract:
  We predict the 21-cm signature of the first metal-free stars. The soft X-rays
emitted by these stars penetrate the atomic medium around their host halos,
generating Lyman alpha photons that couple the spin and kinetic temperatures.
These creates a region we call the Lyman alpha sphere, visible in 21-cm against
the CMB, which is much larger than the HII region produced by the same star.
The spin and kinetic temperatures are strongly coupled before the X-rays can
substantially heat the medium, implying that a strong 21-cm absorption signal
from the adiabatically cooled gas in Hubble expansion around the star is
expected when the medium has not been heated previously. A central region of
emission from the gas heated by the soft X-rays is also present although with a
weaker signal than the absorption. The Lyman alpha sphere is a universal
signature that should be observed around any first star illuminating its
vicinity for the first time. The 21-cm radial profile of the Lyman alpha sphere
can be calculated as a function of the luminosity, spectrum and age of the
star. For a star of a few hundred solar masses and zero metallicity (as
expected for the first stars), the physical radius of the Lyman alpha sphere
can reach tens of kiloparsecs. The first metal-free stars should be strongly
clustered because of high cosmic biasing; this implies that the regions
producing a 21-cm absorption signal may contain more than one star and will
generally be irregular and not spherical, because of the complex distribution
of the gas. We discuss the feasiblity of detecting these Lyman alpha spheres,
which would be present at redshifts $z\sim 30$ in the Cold Dark Matter model.
Their observation would represent a direct proof of the detection of a first
star.


title: Effects of primordial helicity on CMB

abstract:
  I present here a brief overview of the effects caused by parity violating
cosmological sources (such as magnetic or kinetic helicity) on the CMB
fluctuations. I discuss also primordial helicity induced relic gravitational
waves. All these effects can serve as cosmological tests for primordial
helicity detection.


title:
The peculiar sdB NGC6121-V46: A low-mass double degenerate ellipsoidal
  variable in a globular cluster

abstract:
  The variable sdB known as V46 in the globular cluster M4 has remained
enigmatic since its discovery almost 10 years ago. We present here radial
velocity measurements obtained from medium-resolution VLT/FORS2 spectra that
show variations at twice the period of the luminosity changes. This implies
that the system is an ellipsoidal variable. Unlike the other sdB binaries of
this nature, the fundamental parameters of this star we derive suggest that it
lies below the Zero Age Extreme Horizontal Branch. From the cluster distance
and the gravity we determine the mass of V46 to be ~0.19Msun. This is too low
to sustain core helium burning. From the mass function we derive a lower limit
for the companion of only 0.26Msun. We discuss the star's origin in the context
of close binary evolution in the field and globular clusters.


title: Noncommutative KKLMMT Model

abstract:
  In the noncommutative space-time the fine tuning in KKLMMT model can be
significantly released and a nice running of spectral index fitting the WMAP
three year data can be achieved. The fitting results show that the
noncommutative mass scale is roughly $5\times 10^{14}$ Gev. The string mass
scale is higher than the noncommutative scale unless the string coupling is
smaller than $10^{-10}$.


title:
The Nainital-Cape Survey -- II:Report for pulsation in five chemically
  peculiar A-type stars and presentation of 140 null results

abstract:
  To search photometric variability in chemically peculiar A type stars in the
northern hemisphere. High-speed photometric observations of Ap and Am star
candidates have been carried out from ARIES (Manora Peak, Nainital) using a
three-channel fast photometer attached to the ARIES 104-cm Sampurnanand
telescope. This paper presents three new variables: HD 113878, HD 118660 and HD
207561. During the time span of the survey (1999 December to 2004 January)
pulsations of the $\delta$ Sct type were also found for the two evolved Am
stars HD 102480 and HD 98851, as reported in Joshi et al. (2002, 2003).
Additionally, we present 140 null results of the survey for this time span. The
star HD 113878 pulsates with a period of 2.31 hr, which is typical of $\delta$
Sct stars. HD 118660 exhibits multi-periodic variability with a prominent
period of nearly 1 hr. These periods need to be investigated and make HD 118660
a particularly interesting target for further observations. For HD 207561, a
star classified as Am, a probable pulsation with a period of 6 min was found in
the light curves obtained on two consecutive nights. Both HD 102480 and HD
98851 exhibit unusual alternating high and low amplitude maxima, with a period
ratio of 2:1. The analysis of the null results confirms the photometric quality
of the Nainital


title:
Small-scale magnetic buoyancy and magnetic pumping effects in a
  turbulent convection

abstract:
  We determine the nonlinear drift velocities of the mean magnetic field and
nonlinear turbulent magnetic diffusion in a turbulent convection. We show that
the nonlinear drift velocities are caused by the three kinds of the
inhomogeneities, i.e., inhomogeneous turbulence; the nonuniform fluid density
and the nonuniform turbulent heat flux. The inhomogeneous turbulence results in
the well-known turbulent diamagnetic and paramagnetic velocities. The nonlinear
drift velocities of the mean magnetic field cause the small-scale magnetic
buoyancy and magnetic pumping effects in the turbulent convection. These
phenomena are different from the large-scale magnetic buoyancy and magnetic
pumping effects which are due to the effect of the mean magnetic field on the
large-scale density stratified fluid flow. The small-scale magnetic buoyancy
and magnetic pumping can be stronger than these large-scale effects when the
mean magnetic field is smaller than the equipartition field. We discuss the
small-scale magnetic buoyancy and magnetic pumping effects in the context of
the solar and stellar turbulent convection. We demonstrate also that the
nonlinear turbulent magnetic diffusion in the turbulent convection is
anisotropic even for a weak mean magnetic field. In particular, it is enhanced
in the radial direction. The magnetic fluctuations due to the small-scale
dynamo increase the turbulent magnetic diffusion of the toroidal component of
the mean magnetic field, while they do not affect the turbulent magnetic
diffusion of the poloidal field.


title:
The X-ray afterglow flat segment in short GRB 051221A: Energy injection
  from a millisecond magnetar?

abstract:
  The flat segment lasting $\sim 10^4$ seconds in the X-ray afterglow of
GRB051221A represents the first clear case of strong energy injection in the
external shock of a short GRB afterglow. In this work, we show that a
millisecond pulsar with dipole magnetic field $\sim 10^{14}$ Gauss could well
account for that energy injection. The good quality X-ray flat segment thus
suggests that the central engine of this short burst may be a millisecond
magnetar.


title:
On the validity of the 630 nm Fe I nm lines for the magnetometry of the
  internetwork quiet Sun

abstract:
  The purpose of this work is to analyze the reliability of the magnetic field
strengths inferred from the 630 nm pair of Fe I lines at internetwork quiet Sun
regions. Some numerical experiments have been performed that demonstrate the
inability of these lines to recover the magnetic field strength in such low
flux solar regions. It is shown how different model atmospheres, with magnetic
field strengths ranging from few hundred Gauss to kiloGauss, give rise to
Stokes profiles that can not be distinguished. The reasons for this degeneracy
are discussed.


title: UCDs - a mixed bag of objects

abstract:
  The name "Ultra-Compact Dwarf Galaxy" (UCD) was invented for a new type of
astronomical object that has been discovered in cores of nearby galaxy clusters
a decade ago. UCDs resemble globular clusters, but are up to 100 times more
massive and slightly more extended. Their luminosities are comparable to those
of nuclei of the most massive dwarf ellipticals or late-type spirals. Various
formation scenarios have been brought forward to explain the origin and
evolution of UCDs. Two of them seem to be most promising: first, UCDs might be
the remnant nuclei of galaxies that have been disrupted in the cluster
environment. Second, UCDs might have formed from the agglomeration of many
young, massive star clusters that were created during ancient merger events. In
this contribution, I review the discovery history of UCDs, summarize their
observational properties in the fundamental plane of stellar systems and
discuss the implications for the different formation scenarios based on our
current knowledge about these enigmatic objects.


title:
Optical spectroscopy of BL Lacertae objects. Broad lines, companion
  galaxies and redshift lower limits

abstract:
  Aims: We present optical spectroscopy of a sample of BL Lac objects, to
determine their redshift, to study their broad emission line properties and to
characterize their close environment. Methods: Twelve objects were observed
using the ESO 3.6m and the NOT 2.5m telescopes, obtaining spectra for the BL
Lacs and for nearby sources. Results: For seven objects, nuclear emission lines
and/or absorption lines from the host galaxy were detected. In all the four
cases where absorption lines were revealed, the host galaxy has been resolved
with HST or ground-based imaging. The broad H_alpha luminosities (or their
upper limits) of the BL Lacs are similar to those of radio-loud quasars. For
two BL Lacs, spectroscopy of close companions indicates that they are at the
redshift of the BL Lacs, and therefore physically associated and likely
interacting. Five BL Lacs have a featureless spectrum. In these cases, we apply
a new technique to derive lower limits for their redshift. which are consistent
with lower limits deduced from imaging.


title: Magnetars as cooling neutron stars with internal heating

abstract:
  We study thermal structure and evolution of magnetars as cooling neutron
stars with a phenomenological heat source in a spherical internal layer. We
explore the location of this layer as well as the heating rate that could
explain high observable thermal luminosities of magnetars and would be
consistent with the energy budget of neutron stars. We conclude that the heat
source should be located in an outer magnetar's crust, at densities rho < 5e11
g/cm^3, and should have the heat intensity of the order of 1e20 erg/s/cm^3.
Otherwise the heat energy is mainly emitted by neutrinos and cannot warm up the
surface.


title: Crossing the phantom divide without phantom matter

abstract:
  A class of braneworld models can lead to phantom-like acceleration of the
late universe, but without the need for any phantom matter. In the simplest
models, the universe contains only cold dark matter and a cosmological
constant. We generalize these models by introducing a quintessence field. The
new feature in our models is that quintessence leads to a crossing of the
phantom divide, $w=-1$. This is a purely gravitational effect, and there is no
phantom instability. Furthermore, the Hubble parameter is always decreasing,
and there is no big rip singularity in the future.


title: The messy environment of Mrk 6

abstract:
  In recent years it has become clear that understanding the absorption present
in AGN is essential given its bearing on unification models. We present the
most recent XMM-Newton observation of Mrk 6, with the goal of understanding the
nature and origin of the complex absorption intrinsic to this source. X-ray
spectral fitting shows that a simple warm absorption model provides an equally
good statistical representation of the CCD data as a partial covering model.
Furthermore, once the RGS data are included in the spectral fitting, the simple
warm absorber model provides a very good fit to the data, without increasing
the complexity of the model, in contrast with the partial covering model which
requires the addition of either a low metalicity (<0.03 solar) thermal plasma
or low temperature blackbody emission in order to provide a similar quality
fit. The warm absorber is also a considerably more natural way to explain the
variability observed in the X-ray absorbing column density between the previous
XMM-Newton observation and this one, requiring only a second, higher column
density, higher ionisation, absorber to be present during the previous
XMM-Newton observation. In comparison, the partial covering models which
requires moving, clumpy, material relatively close to the source that result in
two distinct lines of sight, with separate absorbing columns that each vary
considerably without any associated change in their covering fractions, in
order to explain the observed variability. We associate the warm absorber
either with an accretion disk wind with densities of ~10^9 /cm^3, or with an
ionised `skin' or atmosphere of the molecular torus with densities of ~10^3 -
10^5 /cm^3.


title: Hubble Space Telescope Observations of Star Clusters in M101

abstract:
  Hubble Space Telescope Advanced Camera for Surveys (ACS) images are used to
identify and study star cluster candidates in the nearby spiral galaxy M101.
About 3000 round, slightly-resolved cluster candidates are identified in 10 ACS
pointings covering an area of 106 arcmin^2. The cluster candidates' color and
size distributions are consistent with those of star clusters in other nearby
spirals. The majority of the M101 candidates are blue and more likely to be
associated with the galaxy's spiral arms, implying that they are young. The
galaxy-luminosity-normalized number of `young massive clusters' in M101 is
similar to that found in other spirals, as is the cluster density at a fiducial
absolute magnitude. We confirm a previous finding that M101 has a large number
of faint, red star clusters: if these are old globular clusters then this
galaxy has a very large globular cluster population. More plausible is that the
faint red clusters are reddened young clusters; their colors and luminosities
are also consistent with this explanation.


title: Quasars and Galaxy Clusters Paired Across NGC 4410

abstract:
  The aim is to investigate the region of the sky around NGC4410/Mrk1325 for
objects which are physically associated with this active, double nucleus
galaxy. We use archived data to study the placement, brightness, X-ray
properties and redshifts of objects within 60' of the bright, central galaxy.
It is found that pairs of quasars are aligned across NGC 4410 which, if ejected
from it, have equal and opposite ejection velocities and fall very close to the
quantized Karlsson redshift peaks for quasars. X-ray sources and Abell galaxy
clusters at higher redshifts appear elongated along directions away from
NGC4410.


title: The evolutionary state of the southern dense core Cha-MMS1

abstract:
  Aims: Our goal is to set constraints on the evolutionary state of the dense
core Cha-MMS1 in the Chamaeleon I molecular cloud. Methods: We analyze
molecular line observations carried out with the new submillimeter telescope
APEX. We look for outflow signatures around the dense core and probe its
chemical structure, which we compare to predictions of models of gas-phase
chemistry. We also use the public database of the Spitzer Space Telescope (SST)
to compare Cha-MMS1 with the two Class 0 protostars IRAM 04191 and L1521F,
which are at the same distance. Results: We measure a large deuterium
fractionation for N2H+ (11 +/- 3 %), intermediate between the prestellar core
L1544 and the very young Class 0 protostar L1521F. It is larger than for HCO+
(2.5 +/- 0.9 %), which is probably the result of depletion removing HCO+ from
the high-density inner region. Our CO(3-2) map reveals the presence of a
bipolar outflow driven by the Class I protostar Ced 110 IRS 4 but we do not
find evidence for an outflow powered by Cha-MMS1. We also report the detection
of Cha-MMS1 at 24, 70 and 160 microns by the instrument MIPS of the SST, at a
level nearly an order of magnitude lower than IRAM 04191 and L1521F.
Conclusions: Cha-MMS1 appears to have already formed a compact object, either
the first hydrostatic core at the very end of the prestellar phase, or an
extremely young protostar that has not yet powered any outflow, at the very
beginning of the Class 0 accretion phase.


title:
Rates and properties of type Ia supernovae as a function of mass and
  star-formation in their host galaxies

abstract:
  (ABRIDGED) We show that Type Ia supernovae (SNe Ia) are formed within both
very young and old stellar populations, with observed rates that depend on the
stellar mass and mean star-formation rates (SFRs) of their host galaxies.
Models where the SN Ia rate depends solely on host galaxy stellar mass are
ruled out with 99% confidence. Our analysis is based on 100
spectroscopically-confirmed SNe Ia, plus 24 photometrically-classified events,
all from the Supernova Legacy Survey (SNLS) and distributed over 0.2<z<0.75.
Using multi-band photometry, we estimate stellar masses and SFRs for the SN Ia
host galaxies by fitting their broad-band spectral energy distributions with
the galaxy spectral synthesis code, PEGASE.2. We show that the SN Ia rate per
unit mass is proportional to the specific SFR of the parent galaxies -- more
vigorously star-forming galaxies host more SNe Ia per unit stellar mass,
broadly equivalent to the trend of increasing SN Ia rate in later-type galaxies
seen in the local universe. Following earlier suggestions for a simple
"two-component" model approximating the SN Ia rate, we find bivariate linear
dependencies of the SN Ia rate on both the stellar masses and the mean SFRs of
the host systems. We also demonstrate a dependence of distant SN Ia light-curve
shapes on star-formation in the host galaxy, similar to trends observed
locally. Passive galaxies, with no star-formation, preferentially host
faster-declining/dimmer SNe Ia, while slower-declining/brighter events are only
found in systems with ongoing star-formation. We model the light-curve width
distribution in star-forming galaxies as the sum of a young component, and an
old component taken from the distribution in non-star-forming galaxies.


title: Off-axis emission from relativistic plasma flows

abstract:
  We show that there is no universal law describing how the spectra and
luminosity of synchrotron and inverse Compton radiation from relativistic jets
change with increasing observation angle. Instead, the physics of particle
acceleration leaves pronounced imprints in the observed spectra and allows for
a freedom in numerous modifications of them. The impact of these effects is the
largest for high-energy radiation and depends on the details of particle
acceleration mechanism(s), what can be used to discriminate between different
models. Generally, the beam patterns of relativistic jets in GeV-TeV spectral
domain are much wider than the inverse Lorentz factor. The off-axis emission in
this energy range appear to be brighter, have much harder spectra and a much
higher cut-off frequency compared to the values derived from Doppler boosting
considerations alone.
  The implications include the possibility to explain high-latitude
unidentified EGRET sources as off-axis but otherwise typical relativistic-jet
sources, such as blazars, and the prediction of GeV-TeV afterglow from
transient jet sources, such as Gamma-Ray Bursts. We also discuss the phenomenon
of beam-pattern broadening in application to neutrino emission.


title: Resonant Relaxation near the Massive Black Hole in the Galactic Center

abstract:
  The coherent torques between stars on orbits near massive black holes (MBHs)
lead to resonant angular momentum relaxation. Due to the fact that orbits are
Keplerian to good approximation, the torques efficiently change the magnitude
of the angular momenta and rotate the orbital inclinations. As a result the
stars are rapidly randomized. The galactic MBH is a good system for the
observational study of resonant relaxation. The age of the young B-stars at a
distance of $\sim0.01 pc$ from the MBH is comparable to the resonant relaxation
time, implying that resonant relaxation may have played an important role in
their dynamical structure. In contrast, the O-stars in the stellar disks at
$\sim0.1 pc$ are younger than the resonant relaxation time, as required by
their dynamical coherence. Resonant relaxation dynamics dominates the event
rate of gravitational wave (GW) emission from inspiraling stars into MBHs of
masses comparable to the Galactic MBH. Resonant relaxation leads to rates
$\lesssim 10$ times higher than those predicted by 2-body relaxation, which
would improve the prospects of detecting these events by future GW detectors,
such as LISA.


title: Properties of Post-AGB stars

abstract:
  A review is presented of the most relevant results obtained in the last few
years on this rare class of astronomical sources. Multi-wavelength analysis of
an increasing number of post-AGB stars reveal that they constitute a more
inhomogeneous population of stars than previously thought. The new data
available allow us to study these sources with unprecedent spatial resolution
and to extend our spectroscopic knowledge in a systematic way to the infrared
for the first time, where crucial information is contained on the chemical
composition of the gas and dust in their circumstellar shells. The overall
infrared properties derived from ISO and Spitzer data can be used to trace the
mass loss history and the chemical evolution of the ejected material. The new
results impose severe observational constraints to the current nucleosynthesis
models and suggest that the evolution is mainly determined not only by the
initial mass but also by the metallicity of the progenitor star. Post-AGB
samples are likely to grow in the near future with the advent of new data from
space facilities like Spitzer or Akari. Studies of post-AGB stars in the
galactic halo, the Magellanic Clouds and other galaxies of the Local Group will
certainly improve our knowledge on the evolutionary connections between AGB
stars and PNe.


title: Microquasar hadronic jets at very high-energy gamma-rays

abstract:
  Microquasars (MQs) present emission over the whole spectrum, from radio
wavelengths to gamma-rays. The microquasar spectral energy distribution is very
complex, being a signature of the different physical processes that generate
the radiation emitted by these objects. In this work, we estimate the amount of
broad-band emission produced by relativistic protons, released from the jet of
a MQ, interacting with high density regions of the ISM. We show that a two
components source, the microquasar itself and the region of interaction between
the jets and the ISM, could be unveiled by the new instruments at high-energy
and very high-energy gamma-rays.


title:
Deep spectroscopy of 9C J1503+4528: a very young CSS radio source at
  z=0.521

abstract:
  9C J1503+4528 is a very young CSS radio galaxy, with an age of order 10^4
years. This source is therefore an ideal laboratory for the study ofthe
intrinsic host galaxy/IGM properties, interactions between the radio source and
surrounding ISM, links between star formation and AGN activity and the radio
source triggering mechanism. Here we present the results of a spectroscopic
analysis of this source, considering each of these aspects of radio source
physics.
  We find that shock ionization by the young radio source is important in the
central regions of the galaxy on scales similar to that of the radio source
itself, whilst evidence for an AGN ionization cone is observed at greater
distances. Line and continuum features require the presence of a young stellar
population, the best-fit model for which implies an age of 5x10^6 years,
significantly older than the radio source.
  Most interestingly, the relative sizes of radio source and extended emission
line region suggest that both AGN and radio source are triggered at
approximately the same time.
  If both the triggering of the radio source activity and the formation of the
young stellar population had the same underlying cause, this source provides a
sequence for the events surrounding the triggering process. We propose that the
AGN activity in 9C J1503+4528 was causedby a relatively minor interaction, and
that a super-massive black hole powering the radio jets must have been in place
before the AGN was triggered.


title:
Elastic or magnetic? A toy model for global magnetar oscillations with
  implications for QPOs during flares

abstract:
  We use a simple toy-model to discuss global MHD modes of a neutron star,
taking into account the magnetic coupling between the elastic crust and the
fluid core. Our results suggest that the notion of pure torsional crust modes
is not useful for the coupled system, all modes excite Alfven waves in the
core. However, we also show that the modes that are most likely to be excited
by a fractured crust, eg. during a magnetar flare, are such that the crust and
the core oscillate in concert. For our simple model, the frequencies of these
modes are similar to the ``pure crustal'' frequencies. In addition, our model
provides a natural explanation for the presence of lower frequency ($< 30$~Hz)
QPOs seen in the December 2004 giant flare of SGR 1806-20.


title:
The Compton-Getting effect on ultra-high energy cosmic rays of
  cosmological origin

abstract:
  Deviations from isotropy have been a key tool to identify the origin and the
primary type of cosmic rays at low energies. We suggest that the
Compton-Getting effect can play a similar role at ultra-high energies: If at
these energies the cosmic ray flux is dominated by sources at cosmological
distances, then the movement of the Sun relative to the cosmic microwave
background frame induces a dipole anisotropy at the 0.6% level. The energy
dependence and the orientation of this anisotropy provide important information
about the transition between galactic and extragalactic cosmic rays, the charge
of the cosmic ray primaries, the galactic magnetic field and, at the highest
energies, the energy-loss horizon of cosmic rays. A 3-sigma detection of this
effect requires around 10^6 events in the considered energy range and is thus
challenging but not impossible with present detectors. As a corollary we note
that the Compton-Getting effect allows one also to constrain the fraction of
the diffuse gamma-ray background emitted by sources at cosmological distance,
with promising detection possibilities for the GLAST satellite.


title: A 0.8-2.4 microns spectral atlas of Active Galactic Nuclei

abstract:
  Aims: We present a near-infrared spectral atlas of 47 active galactic nuclei
(AGN), of all degrees of activity, in the wavelength interval of 0.8-2.4
microns, including the fluxes of the observed emission lines. We analyze the
spectroscopic properties of the continuum and emission line spectra of the
sources Methods: In order to exclude aperture and seeing effects we use
near-infrared spectroscopy in the short cross-dispersed mode (SXD, 0.8-2.4
microns), taking the JHK-bands spectra simultaneously. Results: We present the
most extensive NIR spectral atlas of AGN to date. This atlas offers a suitable
database for studying the continuum and line emission properties of these
objects in a region full of interesting features. The shape of the continuum of
QSOs and Seyfert 1's are similar, being essentially flat in H and K band, in
the J band, a strong variation is found. In Seyfert 2 galaxies, the continuum
in the F_lambda X lambda space smoothly decreases from 1.2 microns redwards in
almost all sources. In J, it smoothly rises bluewards in some sources while in
others a small decreased in flux is observed. The spectra are dominated by
strong emission features of H I, He I, He II, [S III] and conspicuous forbidden
lines of low and high ionization species. Molecular lines of H2 are common
features to most objects. The absence of O I and Fe II lines in Seyfert 2
galaxies give observational support to the fact that these lines are formated
in the outermost portion of the broad line region. [P II] and coronal lines are
detected in all degrees of activity. The [Fe II] 12570A/16436A line ratio
becomes a reliable reddening indicator for the narrow-line region of Seyfert
galaxies.


title: Mid-Infrared Spectroscopy of Disks around Classical T Tauri Stars

abstract:
  We present the first Spitzer Infrared Spectrograph (IRS; The IRS was a
collaborative venture between Cornell University and Ball Aerospace Corporation
funded by NASA through the Jet Propulsion Laboratory and the Ames Research
Center.) observations of the disks around classical T Tauri stars: spectra in
the 5.2-30 micron range of six stars. The spectra are dominated by emission
features from amorphous silicate dust, and a continuous component from 5 to 8
microns that in most cases comprises an excess above the photosphere throughout
our spectral range. There is considerable variation in the silicate
feature/continuum ratio, which implies variations of inclination, disk flaring,
and stellar mass accretion rate. In most of our stars, structure in the
silicate feature suggests the presence of a crystalline component. In one, CoKu
Tau/4, no excess above the photosphere appears at wavelengths shortward of the
silicate features, similar to 10 Myr old TW Hya, Hen 3-600, and HR 4796A. This
indicates the optically thick inner disk is largely absent. The silicate
emission features with peaks at 9.7 and 18 microns indicate small dust grains
are present. The extremely low 10-20 micron color temperature of the dust
excess, 135 K, indicates these grains are located more than 10 AU from the
star. These features are suggestive of gravitational influence by planets or
close stellar companions and grain growth in the region within 10 AU of the
star, somewhat surprising for a star this young (1 Myr).


title: Reionization from cosmic string loops

abstract:
  Loops formed from a cosmic string network at early times would act as seeds
for early formation of halos, which would form galaxies and lead to early
reionization. With reasonable guesses about astrophysical and string
parameters, the cosmic string scale $G\mu$ must be no more than about $3\times
10^{-8}$ to avoid conflict with the reionization redshift found by WMAP. The
bound is much stronger for superstring models with a small string reconnection
probability. For values near the bound, cosmic string loops may explain the
discrepancy between the WMAP value and theoretical expectations.


title:
Leptonic emission from microquasar jets: from radio to very high-energy
  gamma-rays

abstract:
  Microquasars are sources of very high-energy gamma-rays and, very probably,
high-energy gamma-ray emitters. We propose a model for a jet that can allow to
give accurate observational predictions for jet emission at different energies
and provide with physical information of the object using multiwavelength data.


title: Elementary Physics in the Cellular Automaton Universe

abstract:
  General relativity is a mathematical model that uses sophisticated geometry
to describe simple physics. It agrees with experiment in the few tests that can
be made, but the whole edifice is not physics. Instead of using observations to
test that model, I derive a simple empirical model of elementary physics and
cosmology from the observations. The observations imply that the universe is a
finite cellular automaton; that there is no curved space; that fundamental
particles are massless; that "massy" particles, including electrons, are
composed of fundamental particles; that gravitational mass is inertial mass;
that black holes are made from neutrons compressed into bosons; that the
universe was produced from cold compressed particles, not radiation; and that
the universe is not expanding.


title: {Millimeter Multiplicity in NGC 6334 I and I(N)

abstract:
  Using the Submillimeter Array (SMA), we have imaged the 1.3 millimeter
continuum emission at the center of the massive star-forming regions NGC 6334 I
and I(N). In both regions, the SMA observations resolve the emission into
multiple millimeter sources, with most of the sources clustered into areas only
10,000 AU in diameter. Toward NGC 6334 I, we find four compact sources: the two
brightest (I-SMA1 and I-SMA2) are associated with previously-known ammonia
cores; I-SMA3 is coincident with the peak of the compact HII region (NGC 6334
F); and I-SMA4 is a newly-discovered object. While I-SMA3 exhibits a mixture of
free-free and dust emission, the rest of the objects are dust cores. Toward NGC
6334 I(N), seven compact dust cores are found, one of which is associated with
a faint centimeter source. With the exception of I-SMA3, none of the millimeter
sources have infrared counterparts in Spitzer Space Telescope 3-8 micron
images. Using a simple physical model for the dust continuum emission, the
estimated mass of interstellar material toward each of these compact objects is
in the range of 3 to 66 solar masses. The total mass in the compact objects
appears to be similar in I and I(N). The small size of these groups of sources
suggest that these objects are proto-Trapezia forming in the centers of
clusters of low to intermediate-mass stars.


title: Radiatively-Driven Cosmology in the Cellular Automaton Universe

abstract:
  This is an updated version of my paper "An outline of radiatively-driven
cosmology" (Kurucz 2000). Here the Big Bang universe is replaced by a finite
cellular automaton universe with no expansion (Kurucz 2006). The Big Bang is
replaced by many little bangs spread throughout the universe that interact to
produce the initial perturbations that form Population III stars, globular
clusters, and galaxies, but no large-scale structure. These perturbations
evolve into the universe as we now observe it. Evolution during the first
billion years is controlled by radiation. Globular clusters are formed by
radiatively-driven implosions, galaxies are formed by radiatively-triggered
gravitational collapse of systems of globular clusters, and voids and the
microwave background are formed by radiatively-driven expansion. After this
period most of the strong radiation sources are exhausted and the universe
relaxes into gravitational old age as we know it. To relieve the boredom we
present the results of gedanken experiments (Kurucz 1992) in a traditional,
linear, chronological sequence in the hope of stimulating research on the many
topics considered.


title: Parametric Strong Gravitational Lensing Analysis of Abell 1689

abstract:
  (Abridged) We measure the mass distribution of galaxy cluster Abell 1689
within 0.3 Mpc/h_70 of the cluster centre using its strong lensing effect on 32
background galaxies. The multiple images are based on those of Broadhurst et
al. 2005 with some modifications. The cluster profile is explored further out
to ~2.5 Mpc/h_70 with weak lensing shear measurements from Broadhurst et al.
2005b. The masses of ~200 cluster galaxies are measured with Fundamental Plane
in order to accurately model the small scale mass structure in the cluster. The
galaxies are modelled as elliptical truncated isothermal spheres. The dark
matter component of the cluster is described by either non-singular isothermal
ellipsoids (NSIE) or elliptical versions of the universal dark matter profile
(ENFW). We use two dark matter haloes to model the smooth DM in the cluster.
The total mass profile is well described by either an NSIS profile with
sigma=1514+-18 km/s and core radius of r_c=71+-5kpc/h_70, or an NFW profile
with C=6.0+-0.5 and r_200=2.82+-0.11 Mpc/h_70. The errors are assumed to be due
to the error in assigning masses to the individual galaxies in the galaxy
component. The derived total mass is in good agreement with the mass profile of
Broadhurst et al. 05. Using also weak lensing we can constrain the profile
further out to r~2.5 Mpc/h_70. The best fit parameters are then sigma=1499+-15
km/s and r_c=66+-5 kpc/h_70 for the NSIS profile and C=7.6+-0.5 and
r_200=2.55+-0.07 Mpc/h_70 for the NFW profile. Using the same image
configuration as Broadhurst et al. 2005 we obtain a strong lensing model that
is superior to that of Broadhurst et al. 2005 (rms of 2.7'' compared to 3.2'').


title:
Detection of Diffuse Interstellar Bands in the z=0.5 Damped Lyman alpha
  system towards AO 0235+164

abstract:
  We report the first detection of the 5705 and 5780 A Diffuse Interstellar
Bands (DIBs) in a moderate redshift Damped Lyman alpha (DLA) system. We measure
a rest frame equivalent width of 63.2 +- 8.7 mA for the 5705 and 216+-9 mA for
the 5780 A feature in the z_abs 0.524 DLA towards AO 0235+164 and derive limits
for the equivalent widths of the bands at 5797, 6284, and 6613 A. The
equivalent width of the 5780 band is lower than would be expected based on the
Galactic correlation of DIB strength with N(HI), but is in good agreement with
the correlation with E(B-V). The relative strengths of the 5780 and 6284 A DIBs
are inconsistent with all Galactic and extragalactic sightlines, except one
Small Magellanic Cloud wing sightline towards Sk 143. However, the relative
strengths of the 5705 and 5780 A DIBs are consistent with the Galactic
relation, indicating that the relative strengths of these bands may be less
sensitive to environment or that they may be associated with a similar carrier.
The detection of DIBs at z~0.5 demonstrates that the organic compounds usually
assumed to be the band carriers were already present in the universe some five
gigayears ago.


title:
Energy input and response from prompt and early optical afterglow
  emission in gamma-ray bursts

abstract:
  The taxonomy of optical emission detected during the critical first few
minutes after the onset of a gamma-ray burst (GRB) defines two broad classes:
prompt optical emission correlated with prompt gamma-ray emission, and early
optical afterglow emission uncorrelated with the gamma-ray emission. The
standard theoretical interpretation attributes prompt emission to internal
shocks in the ultra-relativistic outflow generated by the internal engine;
early afterglow emission is attributed to shocks generated by interaction with
the surrounding medium. Here we report on observations of a bright GRB that,
for the first time, clearly show the temporal relationship and relative
strength of the two optical components. The observations indicate that early
afterglow emission can be understood as reverberation of the energy input
measured by prompt emission. Measurements of the early afterglow reverberations
therefore probe the structure of the environment around the burst, whereas the
subsequent response to late-time impulsive energy releases reveals how earlier
flaring episodes have altered the jet and environment parameters. Many GRBs are
generated by the death of massive stars that were born and died before the
Universe was ten per cent of its current age, so GRB afterglow reverberations
provide clues about the environments around some of the first stars.


title: Dissecting Galaxy Colors with GALEX, SDSS, and Spitzer

abstract:
  We combine data from SDSS and the GALEX and Spitzer observatories to create a
sample of galaxies observed homogeneously from the UV to the Far-IR. This
sample, consisting of ~460 galaxies observed spectroscopically by SDSS provides
a multiwavelength (0.15-24 micron) view of obscured and unobscured star
formation in nearby (z<0.3) galaxies with SFRs ranging from 0.01 to 100
M_solar/yr. We calculate a robust dust measure from the infrared to UV ratio
(IRX) and explore the influence of star formation history (SFH) on the dust-UV
color relation (i.e. the IRX-beta relation). We find that the UV colors of
galaxies are only weakly dependent on their SFH as measured by the 4000A break.
However, we find that the contributions of dust and SFH are distinguishable
when colors at widely separated wavelengths (e.g. 0.23-3.6 micron) are
introduced. We show this explicitly by recasting the IRX-beta relation as a
more general IRX-SFH-color relation, which we examine in different projections.
We also determine simple fits to this relation.


title: Sub-Structures in the Halo of the Milky Way

abstract:
  The latest results of the QUEST survey for RR Lyrae stars are described. This
survey, which is designed to find and characterize sub-structures in the halo
of our Galaxy, has covered about 700 square degrees of the sky and has detected
693 RR Lyrae stars, most of which are new discoveries. The spatial distribution
of the RR Lyrae stars reveals several interesting groups in the halo. Some of
them appear to be related to previous detections of the destruction of dwarf
spheroidal galaxies (the Sagittarius tidal streams, the Virgo stellar stream,
the Monoceros ring) or globular clusters (Palomar 5), while others still have
an unknown origin.


title:
The Spitzer c2d Survey of Nearby Dense Cores: III: Low Mass Star
  Formation in a Small Group, L1251B

abstract:
  We present a comprehensive study of a low-mass star-forming region,L1251B, at
wavelengths from the near-infrared to the millimeter. L1251B, where only one
protostar, IRAS 22376+7455, was known previously, is confirmed to be a small
group of protostars based on observations with the Spitzer Space Telescope. The
most luminous source of L1251B is located 5" north of the IRAS position. A
near-infrared bipolar nebula, which is not associated with the brightest object
and is located at the southeast corner of L1251B, has been detected in the IRAC
bands. OVRO and SMA interferometric observations indicate that the brightest
source and the bipolar nebula source in the IRAC bands are deeply embedded disk
sources.Submillimeter continuum observations with single-dish telescopes and
the SMA interferometric observations suggest two possible prestellar objects
with very high column densities. Outside of the small group, many young stellar
object candidates have been detected over a larger region of 12' x 12'.
Extended emission to the east of L1251B has been detected at 850 micron; this
"east core" may be a site for future star formation since no point source has
been detected with IRAC or MIPS. This region is therefore a possible example of
low-mass cluster formation, where a small group of pre- and protostellar
objects (L1251B) is currently forming, alongside a large starless core (the
east core).


title:
Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy
  weak lensing

abstract:
  We present results of a measurement of the shape of the density profile of
galaxy groups and clusters traced by 43 335 Luminous Red Galaxies (LRGs) with
spectroscopic redshifts from the Sloan Digital Sky Survey (SDSS). The galaxies
are selected such that they are the brightest within a cylindrical aperture,
split into two luminosity samples, and modeled as the sum of stellar and dark
matter components. We present a detailed investigation of many possible
systematic effects that could contaminate our signal and develop methods to
remove them, including a detected intrinsic alignment for galaxies within 100
kpc/h of LRGs which we remove using photometric redshift information. The
resulting lensing signal is consistent with NFW profile dark matter halos; the
SIS profile is ruled out at the 96 (conservatively) and 99.96 per cent
confidence level (CL) for the fainter and brighter lens samples (respectively)
when we fit using lensing data between 40 kpc/h and 2 Mpc/h with total
signal-to-noise of 19 and 25 for the two lens samples. The lensing signal
amplitude suggests that the faint and bright sample galaxies typically reside
in haloes of mass (2.9+/-0.4)x10^{13} M_{sun}/h and (6.7+/-0.8)x10^{13}
M_{sun}/h respectively, in good agreement with predictions based on halo
spatial density with normalization lower than the 'concordance' sigma_8=0.9.
When fitting for the concentration parameter in the NFW profile, we find c =
5.0+/-0.6 (stat) +/-1 (sys), and c = 5.6+/-0.6 (stat) +/-1 (sys) for the faint
and bright samples, consistent with Lambda-CDM simulations. We also split the
bright sample further to determine masses and concentrations for cluster-mass
halos, finding mass (1.3+/-0.2)x10^{14} M_{sun}/h for the sample of LRGs
brighter than -22.6 in r. (Abridged)


title: Fluorescent Lyman-alpha Emission from Gas Near a QSO at Redshift 4.28

abstract:
  We use integral field spectroscopy with the Gemini North Telescope to detect
probable fluorescent Ly-alpha emission from gas lying close to the luminous QSO
PSS 2155+1358 at redshift 4.28. The emission is most likely coming not from
primordial gas, but from a multi-phase, chemically enriched cloud of gas lying
about 50 kpc from the QSO. It appears to be associated with a highly ionised
associated absorber seen in the QSO spectrum. With the exception of this gas
cloud, the environment of the QSO is remarkably free of neutral hydrogen. We
also marginally detect Ly-alpha emission from a foreground sub-Damped-Ly-alpha
absorption-line system.


title: Distribution of dust clouds around the central engine of NGC 1068

abstract:
  We studied the distribution of dust clouds around the central engine of NGC
1068 based on shifted-and-added 8.8 - 12.3 micron (MIR) multi-filter images and
3.0 - 3.9 micron (L-band) spectra obtained with the Subaru Telescope. In a
region of 100 pc (1.4") around the central peak, we successfully constructed
maps of color temperatures and emissivities of the MIR and L-band continua as
well as the 9.7 micron and 3.4 micron dust features with spatial resolutions of
26 pc (0.37") in the MIR and 22 pc (0.3") in the L-band. Our main results are:
1) color temperature of the MIR continuum scatters around the thermal
equilibrium temperature with the central engine as the heat source while that
of the L-band continuum is higher and independent upon distance from the
central engine; 2) the peak of the 9.7 micron silicate absorption feature is
shifted to a longer wavelength at some locations; 3) the ratio of the optical
depths of the dust features is different from the Galactic values and show
complicated spatial distribution; and 4) there is a pie shaped warm dust cloud
as an enhancement in the emissivity of the MIR continuum extending about 50 pc
to the north from the central engine. We speculate that material falls into the
central engine through this cloud.


title:
The Black Hole in NGC 3379: A Comparison of Gas and Stellar Dynamical
  Mass Measurements with HST and Integral-Field Data

abstract:
  We combine Hubble Space Telescope spectroscopy and ground-based
integral-field data from the SAURON and OASIS instruments to study the central
black hole in the nearby elliptical galaxy NGC 3379. From these data, we obtain
kinematics of both the stars and the nuclear gaseous component. Axisymmetric
three-integral models of the stellar kinematics find a black hole of mass 1.4
(+2.6 / -1.0) x 10^8 M_sun (3 sigma errors). These models also probe the
velocity distribution in the immediate vicinity of the black hole and reveal a
nearly isotropic velocity distribution throughout the galaxy and down to the
black hole sphere of influence R_BH. The morphology of the nuclear gas disc
suggests that it is not in the equatorial plane; however the core of NGC 3379
is nearly spherical. Inclined thin-disc models of the gas find a nominal black
hole of mass 2.0 (+/- 0.1) x 10^8 M_sun (3 sigma errors), but the model is a
poor fit to the kinematics. The data are better fit by introducing a twist in
the gas kinematics (with the black hole mass assumed to be 2.0 x 10^8 M_sun),
although the constraints on the nature and shape of this perturbation are
insufficient for more detailed modelling. Given the apparent regularity of the
gas disc's appearance, the presence of such strong non-circular motion
indicates that caution must be used when measuring black hole masses with gas
dynamical methods alone.


title:
Limits on the Transient Ultra-High Energy Neutrino Flux from Gamma-Ray
  Bursts (GRB) Derived from RICE Data

abstract:
  We present limits on ultra-high energy (UHE; E(nu)>1 PeV) neutrino fluxes
from gamma-ray bursts (GRBs), based on recently presented data, limits, and
simulations from the RICE experiment. We use data from five recorded transients
with sufficient photon spectral shape and redshift information to derive an
expected neutrino flux, assuming that the observed photons are linked to
neutrino production through pion decay via the well-known 'Waxman-Bahcall'
prescription. Knowing the declination of the observed burst, as well as the
RICE sensitivity as a function of polar angle and the previously published
non-observation of any neutrino events allows an estimate of the sensitivity to
a given neutrino flux. Although several orders of magnitude weaker than the
expected fluxes, our GRB neutrino flux limits are nevertheless the first in the
PeV--EeV energy regime. For completeness, we also provide a listing of other
bursts, recorded at times when the RICE experiment was active, but requiring
some assumptions regarding luminosity and redshift to permit estimates of the
neutrino flux.


title:
Implication of Dark Energy Parametrizations on the Determination of the
  Curvature of the Universe

abstract:
  We investigate how the nature of dark energy affects the determination of the
curvature of the universe from recent observations. For this purpose, we
consider the constraints on the matter and dark energy density using
observations of type Ia supernovae, baryon acoustic oscillation peak and cosmic
microwave background with several types of dark energy equation of state.
Although it is usually said that the combination of current observations favors
a flat universe, we found that a relatively large parameter space allows the
universe to be open for a particular model of dark energy. We also discuss what
kind of dark energy model or prior allow a non-flat universe.


title: On the dynamical evolution of hot spots in powerful radio loud AGNs

abstract:
  We describe the dynamical evolution of hot spots velocity, pressure and mass
density in radio loud active galactic nuclei (AGNs), taking proper account of
(1) the conservations of the mass, momentum, and kinetic energy flux of the
unshocked jet, (2) the deceleration process of the jet by shocks, and (3) the
cocoon expansion without assuming the constant aspect ratio of the cocoon. By
the detailed comparison with two dimensional relativistic hydrodynamic
simulations, we show that our model well reproduces the whole evolution of
relativistic jets. Our model can explain also the observational trends of the
velocity, the pressure, the size, and mass density of hot spots in compact
symmetric objects (CSOs) and FR II radio galaxies.


title:
High resolution optical spectroscopy of an LBV-candidate inside the
  CygOB2 association

abstract:
  For the first time, we obtained the high-resolution (R=15000 and 60000)
optical spectra for the extremely luminous star No.12, associated with the
IR-source IRAS20308+4104, a member of the CygOB2 association. We have found
about 200 spectral features in range 4552-7939AA, including the interstellar
NaI, KI lines and numerous DIBs, which are the strongest absorption lines in
the spectrum, along with the HeI, CII, and SiII lines. A two-dimensional
spectral classification indicates that the spectral type is B5+/-0.5 Ia+. Our
analysis of the Vr data shows the presence of a Vr gradient in the stellar
atmosphere, caused by the infall of matter onto the star. The strong Halpha
emission displays broad Thompson wings and time-variable core absorption,
providing evidence that the stellar wind is inhomogeneous, and a slightly
blue-shifted PCyg type absorption profile. We concluded that the wind is
variable in time.


title: A multi-object, multi-field spectrometer and imager for a European ELT

abstract:
  One of the highlights of the European ELT Science Case book is the study of
resolved stellar populations, potentially out to the Virgo Cluster of galaxies.
A European ELT would enable such studies in a wide range of unexplored distant
environments, in terms of both galaxy morphology and metallicity. As part of a
small study, a revised science case has been used to shape the conceptual
design of a multi-object, multi-field spectrometer and imager (MOMSI). Here we
present an overview of some key science drivers, and how to achieve these with
elements such as multiplex, AO-correction, pick-off technology and spectral
resolution.


title: The distribution of SiO in the circumstellar envelope around IRC+10216

abstract:
  New interferometric observations of SiO J=5-4 circumstellar line emission
around the carbon star IRC+10216, using the Submillimeter Array, are presented.
Complemented by multi-transition single-dish observations, including infrared
observations of ro-vibrational transitions, detailed radiative transfer
modelling suggests that the fractional abundance of SiO in the inner part of
the envelope, between approximately 3-8 stellar radii, is as high as 1.5E-6.
This is more than an order of magnitude higher than predicted by equilibrium
stellar atmosphere chemistry in a carbon-rich environment and indicative of the
importance of non-LTE chemical processes. In addition to the compact component,
a spatially more extended (2.4E16 cm) low-fractional-abundance (1.7E-7) region
is required to fit the observations. This suggests that the majority of the SiO
molecules are effectively accreted onto dust grains in the inner wind while the
remaining gas-phase molecules are eventually photodissociated at larger
distances. Evidence of departure from a smooth wind is found in the observed
visibilities, indicative of density variations of a factor 2 to 5 on an angular
scale corresponding to a time scale of about 200 years. Additionally,
constraints on the velocity structure of the wind are obtained.


title:
The coherence of kHz quasi-periodic oscillations in the X-rays from
  accreting neutron stars

abstract:
  We study in a systematic way the quality factor of the lower and upper kHz
QPOs in a sample of low luminosity neutron star X-ray binaries, showing both
QPOs varying over a wide frequency range. The sample includes 4U 1636-536, 4U
1608-522, 4U 1735-44, 4U 1728-34, 4U 1820-303 and 4U 0614+09. We find that all
sources except 4U 0614+091 show evidence of a drop in the quality factor of
their lower kHz QPOs at high frequency. For 4U 0614+091 only the rising part of
the quality factor versus frequency curve has been sampled so far. At the same
time, in all sources but 4U 1728-34, the quality factor of the upper kilo-Hz
QPO increases all the way to the highest detectable frequencies. We show that
the high-frequency behaviours of both the lower and upper kHz QPO quality
factors are consistent with what is expected if the drop is produced by the
approach of an active oscillating region to the innermost stable circular
orbit: the existence of which is a key feature of General Relativity in the
strong field regime. Within this interpretation, our results imply
gravitational masses around 2 solar masses for the neutron stars in those
systems.


title:
Submillimeter spectroscopy of southern hot cores: NGC6334(I) and
  G327.3-0.6

abstract:
  High-mass star-forming regions are known to have a rich molecular spectrum
from many species. Some of the very highly excited lines are emitted from very
hot and dense gas close to the central object(s). The physics and chemistry of
the inner cores of two high mass star forming regions, NGC6334(I) and
G327.3-0.6, shall be characterized. Submillimeter line surveys with the APEX
telescope provide spectra which sample many molecular lines at high excitation
stages. Partial spectral surveys were obtained, the lines were identified,
physical parameters were determined through fitting of the spectra. Both
sources show similar spectra that are comparable to that of the only other high
mass star forming region ever surveyed in this frequency range}, Orion-KL, but
with an even higher line density. Evidence for very compact, very hot sources
is found.


title: Challenges for scaling cosmologies

abstract:
  A cosmological model that aims at solving the coincidence problem should show
that dark energy and dark matter follow the same scaling solution from some
time onward. At the same time, the model should contain a sufficiently long
matter-dominated epoch that takes place before acceleration in order to
guarantee a decelerated epoch and structure formation. So a successful
cosmological model requires the occurrence of a sequence of epochs, namely a
radiation era, a matter-dominated era and a final accelerated scaling attractor
with $\Omega_{\phi} \simeq 0.7$. In this paper we derive the generic form of a
scalar-field Lagrangian that possesses scaling solutions in the case where the
coupling $Q$ between dark energy and dark matter is a free function of the
field $\phi$. We then show, rather surprisingly, that the aforementioned
sequence of epochs cannot occur for a vast class of generalized coupled scalar
field Lagrangians that includes, to our knowledge, all scaling models in the
current literature.


title:
Radio to TeV radiation initiated by termination of hadronic jets from
  microquasars in the ISM

abstract:
  Microquasars (MQs) are potential candidates to produce a non-negligible
fraction of the observed galactic cosmic rays. The protons accelerated at the
jet termination shock interact with the interstellar medium and may produce
extended emission detectable at different energy bands through several
processes: neutral pion-decay produce high-energy and very high-energy
gamma-rays, secondary electrons produced by charged pion-decay generate
synchrotron and bremsstrahlung emission. In addition, the jets of MQs
themselves are likely sources of gamma-rays. We discuss about the association
between the intrinsic and the indirect emission coming from these objects.


title:
Cooling of the quasi-persistent neutron star X-ray transients KS
  1731-260 and MXB 1659-29

abstract:
  We present Chandra and XMM-Newton X-ray observations that monitor the neutron
star cooling of the quasi-persistent neutron star X-ray transients KS 1731-260
and MXB 1659-29 for approximately 4 years after these sources returned to
quiescence from prolonged outbursts. In both sources the outbursts were long
enough to significantly heat the neutron star crust out of thermal equilibrium
with the core. We analyse the X-ray spectra by fitting absorbed neutron star
atmosphere models to the observations. The results of our analysis strengthen
the preliminary findings of Wijnands et al. that in both sources the neutron
star crust cools down very rapidly suggesting it has a high heat conductivity
and that the neutron star core requires enhanced core cooling processes.
Importantly, we now detect the flattening of the cooling in both sources as the
crust returns to thermal equilibrium with the core. We measure the thermal
equilbrium flux and temperature in both sources by fitting a curve that decays
exponentially to a constant level. The cooling curves cannot be fit with just a
simple exponential decay without the constant offset. We find the constant
bolometric flux and effective temperature components to be (9.2 +/- 0.9)E-14
ergs/cm^2/s and 70.0 +/- 1.6 eV in KS 1731-260 and (1.7 +/- 0.3)E-14
ergs/cm^2/s and 51.6 +/- 1.4 eV in MXB 1659-29. In addition, we find that the
crust of KS 1731-260 cools faster than that of MXB 1659-29 by a factor of ~2,
likely due to different crustal properties. This is the first time that the
cooling of a neutron star crust into thermal equilibrium with the core has been
observed in such detail.


title:
Spectral and variability properties of LS 5039 from radio to very
  high-energy gamma-rays

abstract:
  Microquasars are X-ray binaries with relativistic jets. The microquasar LS
5039 turned out to be the first high-energy gamma-ray microquasar candidate due
to its likely association with the EGRET source 3EG J1824-1514. Further
theoretical studies supported this association, which could be extended to
other EGRET sources. Very recently, Aharonian et al. (2005) have communicated
the detection of the microquasar LS 5039 at TeV energies. This fact confirms
the EGRET source association and leaves no doubt about the gamma-ray emitting
nature of this object. The aim of the present work is to show that, applying a
cold-matter dominated jet model to LS 5039, we can reproduce many of the
spectral and variability features observed in this source. Jet physics is
explored, and some physical quantities are estimated as a by-product of the
performed modeling. Although at the moment only LS 5039 has been detected on
the entire electromagnetic spectrum, it does not seem unlikely that other
microquasars will show similar spectral properties. Therefore, an in-depth
study of the first gamma-ray microquasar, on theoretical grounds supported by
observations, can render a useful knowledge applicable elsewhere.


title:
An empirical tool to derive metallicity, reddening and distance for old
  stellar populations from near IR Color Magnitude Diagrams

abstract:
  We present an empirical method to derive photometric metallicity, reddening
and distance to old stellar populations by using a few major features of the
Red Giant Branch (RGB) in near IR color magnitude diagrams. We combine the
observed RGB features with a set of equations linking the global metallicity
[M/H] to suitable RGB parameters (colors, magnitudes and slope), as calibrated
from a homogeneous sample of Galactic Globular Clusters with different
metallicities. This technique can be applied to efficiently derive the main
population parameters of old stellar systems, in the view of using ground-based
adaptive optics and space facilities to probe the stellar content of remote
galaxies.


title:
A New Mechanism for Gravitational Wave Emission in Core-Collapse
  Supernovae

abstract:
  We present a new theory for the gravitational wave signatures of
core-collapse supernovae. Previous studies identified axisymmetric rotating
core collapse, core bounce, postbounce convection, and anisotropic neutrino
emission as the primary processes and phases for the radiation of gravitational
waves. Our results, which are based on axisymmetric, Newtonian
radiation-hydrodynamics supernova simulations (Burrows et al. 2006), indicate
that the dominant emission process of gravitational waves in core-collapse
supernovae may be the oscillations of the protoneutron star core. The
oscillations are predominantly of g-mode character, are excited hundreds of
milliseconds after bounce, and typically last for several hundred milliseconds.
Our results suggest that even nonrotating core-collapse supernovae should be
visible to current LIGO-class detectors throughout the Galaxy, and depending on
progenitor structure, possibly out to Megaparsec distances.


title:
Constraints on the late X-ray emission from the low-energy GRB 031203:
  INTEGRAL data

abstract:
  Comparison of the INTEGRAL upper limits on the hard X-ray flux before and
after the low-energy GRB 031203 with the XMM measurements of the dust-scattered
radiation at lower energies suggests that a significant fraction of the total
burst energy could be released in the form of soft X-rays at an early afterglow
stage with a characteristic duration of ~100-1000s. The overall time evolution
of the GRB 031203 afterglow may have not differed qualitatively from the
behavior of standard (i.e., more intense) bursts studied by the SWIFT
observatory. The available data also admit the possibility that the
dust-scattered radiation was associated with an additional soft component in
the spectrum of the gamma-ray burst itself.


title: A focal plane detector design for a wide-band Laue-lens telescope

abstract:
  The energy range above 60 keV is important for the study of many open
problems in high energy astrophysics such as the role of Inverse Compton with
respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in
SNR, the study of the high energy cut-offs in AGN spectra, and the detection of
nuclear and annihilation lines. Recently the development of high energy Laue
lenses with broad energy bandpasses from 60 to 600 keV have been proposed for a
Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of
celestial sources. The required focal plane detector should have high detection
efficiency over the entire operative range, a spatial resolution of about 1 mm,
an energy resolution of a few keV at 500 keV and a sensitivity to linear
polarization. We describe a possible configuration of the focal plane detector
based on several CdTe/CZT pixelated layers stacked together to achieve the
required detection efficiency at high energy. Each layer can operate both as a
separate position sensitive detector and polarimeter or work with other layers
to increase the overall photopeak efficiency. Each layer has a hexagonal shape
in order to minimize the detector surface required to cover the lens field of
view. The pixels would have the same geometry so as to provide the best
coupling with the lens point spread function and to increase the symmetry for
polarimetric studies.


title: Status and Outlook of the EDELWEISS WIMP Search

abstract:
  EDELWEISS is a direct dark matter search using cryogenic germanium
heat-ionisation detectors, located in the Modane underground laboratory beneath
the Alps. We summarize the final results of EDELWEISS I, which deployed up to
almost one kg of detectors in its final stage. EDELWEISS II recently started
commissioning runs. With an increased detection mass and better shielding, this
stage aims to gain two orders of magnitude in sensitivity and to serve as a
testbed for a larger, ton-scale experiment.


title:
Detection of the radial velocity curve of the B5-A0 supergiant companion
  star of Cir X-1?

abstract:
  In this Paper we report on phase resolved I-band optical spectroscopic and
photometric observations of CirX-1 obtained with the Very Large Telescope. The
spectra are dominated by Paschen absorption lines at nearly all orbital phases
except near phase zero (coinciding with the X-ray dip) when the absorption
lines are filled-in by broad Paschen emission lines. The radial velocity curve
of the absorption lines corresponds to an eccentric orbit (e=0.45) whose period
and time of periastron passage are consistent with the period and phase
predicted by the most recent X-ray dip ephemeris. We found that the I-band
magnitude decreases from 17.6 to ~16.8 near phase 0.9-1.0, this brightening
coincides in phase with the X-ray dip. Even though it is likely that the
absorption line spectrum is associated with the companion star of CirX-1, we
cannot exclude the possibility that the spectrum originates in the accretion
disc. However, if the spectrum belongs to the companion star, it must be a
supergiant of spectral type B5-A0. If we assume that the compact object does
not move through the companion star at periastron, the companion star mass is
constrained to ~<10 Msun for a 1.4 Msun neutron star, whereas the inclination
has to be ~> 13.7 degrees. Alternatively, the measured absorption lines and
their radial velocity curve can be associated with the accretion disc
surrounding a 1.4 Msun neutron star and its motion around the centre of mass.
An absorption line spectrum from an accretion disc is typically found when our
line-of-sight passes through the accretion disc rim implying a high
inclination. However, from radio observations it was found that the angle
between the line-of-sight and the jet axis is smaller than 5 degrees implying
that the jet ploughs through the accretion disc in this scenario.


title:
Imprints of deviations from the gravitational inverse-square law on the
  power spectrum of mass fluctuations

abstract:
  Deviations from the gravitational inverse-square law would imprint
scale-dependent features on the power spectrum of mass density fluctuations. We
model such deviations as a Yukawa-like contribution to the gravitational
potential and discuss the growth function in a mixed dark matter model with
adiabatic initial conditions. Evolution of perturbations is considered in
general non-flat cosmological models with a cosmological constant, and an
analytical approximation for the growth function is provided. The coupling
between baryons and cold dark matter across recombination is negligibly
affected by modified gravity physics if the proper cutoff length of the
long-range Yukawa-like force is > 10 h^{-1} Mpc. Enhancement of gravity affects
the subsequent evolution, boosting large-scale power in a way that resembles
the effect of a lower matter density. This phenomenon is almost perfectly
degenerate in power-spectrum shape with the effect of a background of massive
neutrinos. Back-reaction on density growth from a modified cosmic expansion
rate should however also affect the normalization of the power spectrum, with a
shape distortion similar to the case of a non-modified background.


title: A Search for H2O in the Strongly Lensed QSO MG 0751+2716 at z=3.2

abstract:
  We present a search for 183 GHz H_2O(3_13-2_20) emission in the
infrared-luminous quasar MG 0751+2716 with the NRAO Very Large Array (VLA). At
z=3.200+/-0.001, this water emission feature is redshifted to 43.6 GHz. As
opposed to the faint rotational transitions of HCN (the standard high-density
tracer at high-z), H_2O(3_13-2_20) is observed with high maser amplification
factors in Galactic star-forming regions. It therefore holds the potential to
trace high-density star-forming regions in the distant universe. If indeed all
star-forming regions in massively star-forming galaxies at z>3 have similar
physical properties as e.g. the Orion or W49N molecular cloud cores, the flux
ratio between the maser-amplified H_2O(3_13-2_20) and the thermally excited
CO(1-0) transitions may be as high as factor of 20 (but has to be corrected by
their relative filling factor). MG 0751+2716 is a strong CO(4-3) emitter, and
therefore one of the most suitable targets to search for H_2O(3_13-2_20) at
cosmological redshifts. Our search resulted in an upper limit in line
luminosity of L'(H_2O) < 0.6 x 10^9 K km/s pc^2. Assuming a brightness
temperature of T_b(H_2O) ~= 500 K for the maser emission and CO properties from
the literature, this translates to a H_2O(3_13-2_20)/CO(4-3) area filling
factor of less than 1%. However, this limit is not valid if the H_2O(3_13-2_20)
maser emission is quenched, i.e. if the line is only thermally excited. We
conclude that, if our results were to hold for other high-z sources, H_2O does
not appear to be a more luminous alternative to HCN to detect high-density gas
in star-forming environments at high redshift.


title:
The ZEPLIN-III dark matter detector: instrument design, manufacture and
  commissioning

abstract:
  We present details of the technical design and manufacture of the ZEPLIN-III
dark matter experiment. ZEPLIN-III is a two-phase xenon detector which measures
both the scintillation light and the ionisation charge generated in the liquid
by interacting particles and radiation. The instrument design is driven by both
the physics requirements and by the technology requirements surrounding the use
of liquid xenon. These include considerations of key performance parameters,
such as the efficiency of scintillation light collection, restrictions placed
on the use of materials to control the inherent radioactivity levels,
attainment of high vacuum levels and chemical contamination control. The
successful solution has involved a number of novel design and manufacturing
features which will be of specific use to future generations of direct dark
matter search experiments as they struggle with similar and progressively more
demanding requirements.


title:
Dynamical Expansion of H II Regions from Ultracompact to Compact Sizes
  in Turbulent, Self-Gravitating Molecular Clouds

abstract:
  The nature of ultracompact H II regions (UCHRs) remains poorly determined. In
particular, they are about an order of magnitude more common than would be
expected if they formed around young massive stars and lasted for one dynamical
time, around 10^4 yr. We here perform three-dimensional numerical simulations
of the expansion of an H II region into self-gravitating, radiatively cooled
gas, both with and without supersonic turbulent flows. In the laminar case, we
find that H II region expansion in a collapsing core produces nearly spherical
shells, even if the ionizing source is off-center in the core. This agrees with
analytic models of blast waves in power-law media. In the turbulent case, we
find that the H II region does not disrupt the central collapsing region, but
rather sweeps up a shell of gas in which further collapse occurs. Although this
does not constitute triggering, as the swept-up gas would eventually have
collapsed anyway, it does expose the collapsing regions to ionizing radiation.
We suggest that these regions of secondary collapse, which will not all
themselves form massive stars, may form the bulk of observed UCHRs. As the
larger shell will take over 10^5 years to complete its evolution, this could
solve the timescale problem. Our suggestion is supported by the ubiquitous
observation of more diffuse emission surrounding UCHRs.


title:
An Outbursting Protostar of the FU~Orionis type in the Cygnus OB7
  Molecular Cloud

abstract:
  Context: To follow the early evolution of stars we need to understand how
young stars accrete and eject mass. It is generally assumed that the FU Orionis
phenomenon is related to the variations in the disk accretion, but many
questions remain still open, in particular because of the rarity of FU Ori type
stars.
  Aims: We explore here the characteristics of the outburst and of the
environment of one new object, discovered recently in the in the active star
formation region containing RNO127, within the Cygnus OB7 dark cloud complex.
  Methods: We present an extensive optical and near-infrared study of a new
candidate of FU Orionis object, including its direct imaging, spectroscopy and
scanning Fabry-Perot interferometry.
  Results: The source, associated with the variable reflection nebula,
underwent prodigious outburst. The "Braid" nebula, which appeared in 2000, as
is indicated by its name, consists of two intertwined features, illuminated by
the outburst. Subsequent NIR observations revealed the bright source, which was
not visible on 2MASS images, and its estimated brightening was more than 4
magnitudes. Optical and infrared spectral data show features, which are
necessary for the system to be referred to as a FUor object. The bipolar
optical flow directed by the axis of nebula also was found. Various estimates
give the November/December 1999 as the most probable date for the eruption.


title:
Acoustic oscillations of rapidly rotating polytropic stars. II. Effects
  of the Coriolis and centrifugal accelerations

abstract:
  Context: With the launch of space missions devoted to asteroseismology (like
COROT), the scientific community will soon have accurate measurements of
pulsation frequencies in many rapidly rotating stars.
  Aims: The present work focuses on the effects of rotation on pulsations of
rapidly rotating stars when both the Coriolis and centrifugal accelerations
require a non-perturbative treatment.
  Method: We develop a 2-dimensional spectral numerical approach which allows
us to compute acoustic modes in centrifugally distorted polytropes including
the full influence of the Coriolis force. This method is validated through
comparisons with previous studies, and the results are shown to be highly
accurate.
  Results: In the frequency range considered and with COROT's accuracy, we
establish a domain of validity for perturbative methods, thus showing the need
for complete calculations beyond v.sin i = 50 km/s for a R = 2.3 R_\odot, M =
1.9 M_\odot polytropic star. Furthermore, it is shown that the main differences
between complete and perturbative calculations come essentially from the
centrifugal distortion.


title: Fourth order Weyl gravity

abstract:
  The fourth order Weyl gravity theory of Mannheim and Kazanas is based on
replacing the Einstein-Hilbert action with the square of the Weyl tensor, and
on modifying the matter action of the standard model of particle physics to
make it conformally invariant. This theory has been suggested as a model of
both dark matter and dark energy. We argue that the conformal invariance is not
a fundamental property of the theory, and instead is an artifact of the choice
of variables used in its description. We deduce that in the limit of weak
fields and slow motions the theory does not agree with the predictions of
general relativity, and is therefore ruled out by Solar System observations.


title: Dispersal of Gaseous Circumstellar Discs around High-Mass Stars

abstract:
  We study the dispersal of a gaseous disc surrounding a central high-mass
stellar core once this circumstellar disc becomes fully ionized. If the stellar
and surrounding EUV and X-ray radiations are so strong as to rapidly heat up
and ionize the entire circumstellar disc as further facilitated by disc
magnetohydrodynamic (MHD) turbulence, a shock can be driven to travel outward
in the fully ionized disc, behind which the disc expands and thins. For an
extremely massive and powerful stellar core, the ionized gas pressure
overwhelms the centrifugal and gravitational forces in the disc. In this limit,
we construct self-similar shock solutions for such an expansion and depletion
phase. As a significant amount of circumstellar gas being removed, the relic
disc becomes vulnerable to strong stellar winds and fragments into clumps. We
speculate that disc disappearance happens rapidly, perhaps on a timescale of
$\sim 10^3-10^4\hbox{yr}$ once the disc becomes entirely ionized sometime after
the onset of thermal nuclear burning in a high-mass stellar core.


title: X-ray observations of three young, early-type galaxies

abstract:
  Massive halos of hot plasma exist around some, but not all elliptical
galaxies. There is evidence that this is related to the age of the galaxy. In
this paper new X-ray observations are presented for three early-type galaxies
that show evidence of youth, in order to investigate their X-ray components and
properties. NGC 5363 and NGC 2865 were found to have X-ray emission dominated
by purely discrete stellar sources. Limits are set on the mass distribution in
one of the galaxies observed with XMM-Newton, NGC 4382, which contains
significant hot gas. We detect the X-ray emission in NGC 4382 out to 4r$_e$.
The mass-to-light ratio is consistent with a stellar origin in the inner
regions but rises steadily to values indicative of some dark matter by 4r$_e$.
These results are set in context with other data drawn from the literature, for
galaxies with ages estimated from dynamical or spectroscopic indicators. Ages
obtained from optical spectroscopy represent central luminosity weighted
stellar ages. We examine the X-ray evolution with age, normalised by B and K
band luminosities. Low values of Log(L$_X$/L$_B$) and Log(L$_X$/L$_K$) are
found for all galaxies with ages between 1 and 4 Gyrs. Luminous X-ray emission
only appears in older galaxies. This suggests that the interstellar medium is
removed and then it takes several gigayears for hot gas halos to build up,
following a merger. A possible mechanism for gas expulsion might be associated
with feedback from an active nucleus triggered during a merger.


title:
GRB 050717: A Long, Short-Lag, High Peak Energy Burst Observed by Swift
  and Konus

abstract:
  The long burst GRB 050717 was observed simultaneously by the Burst Alert
Telescope (BAT) on Swift and the Konus instrument on Wind. Significant hard to
soft spectral evolution was seen. Early gamma-ray and X-ray emission was
detected by both BAT and the X-Ray Telescope (XRT) on Swift. The XRT continued
to observe the burst for 7.1 days and detect it for 1.4 days. The X-ray light
curve showed a classic decay pattern; the afterglow was too faint for a jet
break to be detected. No optical, infrared or ultraviolet counterpart was
discovered despite deep searches within 14 hours of the burst. Two particular
features of the prompt emission make GRB 050717 a very unusual burst. First,
the peak of the nu Fnu spectrum was observed to be 2401(-568/+781) keV for the
main peak, which is the highest value of Epeak ever observed. Secondly, the
spectral lag for GRB 050717 was determined to be 2.5 +- 2.6 ms, consistent with
zero and unusually short for a long burst. This lag measurement suggests that
this burst has a high intrinsic luminosity and hence is at high redshift (z >
2.7). Despite these unusual features GRB 050717 exhibits the classic prompt and
afterglow behaviour of a gamma-ray burst.


title:
Far Ultraviolet Spectroscopic Explorer Survey of Magellanic Cloud
  Supernova Remnants

abstract:
  We report the progress to date from an ongoing unbiased ultraviolet survey of
supernova remnants in the Magellanic Clouds using the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite. This survey is obtaining spectra of a
random large sample of Magellanic Cloud supernova remnants with a broad range
of radio, optical, and X-ray properties. To date, 39 objects have been observed
in the survey (38 in the LMC and one in the SMC) and 15 have been detected, a
detection rate of nearly 40%. Our survey has nearly tripled the number of
UV-detected SNRs in the Magellanic Clouds (from 8 to 22). Because of the
diffuse source sensitivity of FUSE, upper limits on non-detected objects are
quite sensitive in many cases. Estimated total luminosities in O~VI span a
broad range from considerably brighter to many times fainter than the inferred
soft X-ray luminosities, indicating that O~VI can be an important and largely
unrecognized coolant in certain objects. We compare the optical and X-ray
properties of the detected and non-detected objects but do not find a simple
indicator for ultraviolet detectability. Non-detections may be due to
clumpiness of the emission, high foreground extinction, slow shocks whose
emission gets attenuated by the Magellanic interstellar medium, or a
combination of these effects.


title:
Warm Molecular Gas in the Outflow and Envelope of IRAS 12496-7650 (DK
  Cha)

abstract:
  Aims:To obtain insight into the physical structure of the warm gas in the
inner envelope of protostars and the interaction with the outflow. Methods:
Sub-millimeter observations of 12CO, 13CO and/or C18O in J=3-2, J=4-3 and J=7-6
were obtained with the APEX Telescope towards IRAS 12496-7650, an intermediate
mass young stellar object. The data are compared to ISO-LWS observations of CO
J=14-13 up to J=19-18 lines to test the different proposed origins of the CO
lines. Results: The outflow is prominently detected in the 3-2 and 4-3 lines,
but not seen at similar velocities in the 7-6 line, constraining the
temperature in the high-velocity (> 5 km/s from line center) gas to less than
50 K, much lower than inferred from the analysis of the ISO-LWS data. In
addition, no isothermal gas model can reproduce the emission in both the 7-6
and the higher-J ISO-LWS lines.The 7-6 line probably originates in the inner
(<250 AU) region of the envelope at ~150 K. Detailed radiative transfer
calculations suggest that the ISO-LWS lines are excited by a different
mechanism, possibly related to the larger-scale outflow. All possible
mechanisms on scales smaller than 8 " are excluded. High-resolution continuum
as well as high-J 12CO and isotopic line mapping are needed to better constrain
the structure of the warm gas in the inner envelope and the interaction with
the outflow.


title: Timing properties of XB 1254-690

abstract:
  We analyze archival Rossi X-ray Timing Explorer (RXTE) Proportional Counter
Array (PCA) data of the low mass X-ray binary (LMXB) system XB 1254-690. We
calculate colour-colour diagram, hardness-intensity diagram and power spectra
of this source, associate its broad low-frequency timing features with the
portions of the colour-colour diagram, and establish that XB 1254-690 is an
atoll source. This will be important to correlate the timing and spectral
features of this dipping LMXB with its various states, which may be useful to
understand LMXBs in general. We find the source always in the high intensity
banana state, which may explain why ~ 1 Hz "dipper QPOs" have never been
observed from XB 1254-690. We also report a suggestive evidence of millisecond
period brightness oscillations at the frequency ~ 95 Hz during a thermonuclear
X-ray burst for the first time from this source.


title: Recognizing the First Radiation Sources Through Their 21-cm Signature

abstract:
  At the beginning of the reionization epoch, radiation sources produce
fluctuations in the redshifted 21-cm background. We show that different types
of sources (such as miniquasars, Pop II and III stars, supernovae, etc.)
produce distinct signatures in the 21-cm signal radial profiles and statistical
fluctuations, through which they can be identified. Further, we show that the
21-cm signal from X-ray emitting sources is much easier to observe than was
expected, due to a previously neglected pumping mechanism.


title:
Black Hole-Neutron Star Binary Merger Calculations: GRB Progenitors and
  the Stability of Mass Transfer

abstract:
  We have calculated the first dynamical evolutions of merging black
hole-neutron star binaries that treat the combined spacetime in a
nonperturbative general relativistic framework. Using the conformal flatness
approximation, we have studied how the location of the tidal disruption radius
with respect to the the black hole horizon and innermost stable circular orbit
(ISCO) affects the qualitative evolution of the system. Based on simple
arguments, we show that for a binary mass ratio q>~0.24, tidal disruption
occurs outside the ISCO, while the opposite is true for q<~0.24. When tidal
disruption occurs sufficiently far outside the ISCO, mass is transferred
unstably from the neutron star to the black hole, resulting in the complete
disruption of the neutron star. When tidal disruption occurs slightly within
the ISCO, we find that some of the mass forms an extremely hot disk around the
black hole. The resulting configurations in this case are excellent candidates
for the progenitors of short-hard gamma ray bursts.


title:
On the internal structure of starless cores. II. A molecular survey of
  L1498 and L1517B

abstract:
  [Abridged] We present a molecular survey of the starless cores L1498 and
L1517B. These cores have been selected for their relative isolation and
close-to-round shape, and they have been observed in a number of lines of 13
molecular species (4 already presented in the first part of this series): CO,
CS, N2H+, NH3, CH3OH, SO, C3H2, HC3N, C2S, HCN, H2CO, HCO+, and DCO+. Using a
physical model of core structure and a Monte Carlo radiative transfer code, we
determine for each core a self-consistent set abundances that fits
simultaneously the observed radial profile of integrated intensity and the
emergent spectrum towards the core center (for abundant species, optically thin
isopologues are used). From this work, we find that L1498 and L1517B have
similar abundance patterns, with most species suffering a significant drop
toward the core center. This occurs for CO, CS, CH3OH, SO, C3H2, HC3N, C2S,
HCN, H2CO, HCO+, and DCO+, which we fit with profiles having a sharp central
hole. The size of this hole varies with molecule: DCO+, HCN, and HC3N have the
smallest holes while SO, C2S and CO have the largest holes. Only N2H+ and NH3
are present in the gas phase at the core centers. From the different behavior
of molecules, we select SO, C2S, and CH3OH as the most sensitive tracers of
molecular depletion. Comparing our abundance determinations with the
predictions from current chemical models we find order of magnitude
discrepancies. Finally, we show how the ``contribution function'' can be used
to study the formation of line profiles from the different regions of a core.


title: An algorithm for solving the pulsar equation

abstract:
  We present an algorithm of finding numerical solutions of pulsar equation.
The problem of finding the solutions was reduced to finding expansion
coefficients of the source term of the equation in a base of orthogo- nal
functions defined on the unit interval by minimizing a multi-variable mismatch
function defined on the light cylinder. We applied the algorithm to Scharlemann
& Wagoner boundary conditions by which a smooth solu- tion is reconstructed
that by construction passes success- fully the Gruzinov's test of the source
function exponent.