title:
The chemistry of fluorine-bearing molecules in diffuse and dense
  interstellar gas clouds

abstract:
  We present a theoretical investigation of the chemistry of fluorine-bearing
molecules in diffuse and dense interstellar gas clouds. The chemistry of
interstellar fluorine is qualitatively different from that of any other
element, because - unlike the neutral atoms of any other element found in
diffuse or dense molecular clouds - atomic fluorine undergoes an exothermic
reaction with molecular hydrogen. Over a wide range of conditions attained
within interstellar gas clouds, the product of that reaction - hydrogen
fluoride - is predicted to be the dominant gas-phase reservoir of interstellar
fluorine nuclei. Our model predicts HF column densities ~ 1.E+13 cm-2 in dark
clouds and column densities as large as 1.E-11 cm-2 in diffuse interstellar gas
clouds with total visual extinctions as small as 0.1 mag. Such diffuse clouds
will be detectable by means of absorption line spectroscopy of the J = 1 - 0
transition at 243.2 micron using the Stratospheric Observatory for Infrared
Astronomy (SOFIA) and the Herschel Space Observatory (HSO). The CF+ ion is
predicted to be the second most abundant fluorine-bearing molecule, with
typical column densities a factor ~ 100 below those of HF; with its lowest two
rotational transitions in the millimeter-wave spectral region, CF+ may be
detectable from ground-based observatories. HF absorption in quasar spectra is
a potential probe of molecular gas at high redshift, providing a possible
bridge between the UV/optical observations capable of probing H2 in low column
density systems and the radio/millimeter-wavelength observations that probe
intervening molecular clouds of high extinction and large molecular fraction;
at redshifts beyond ~ 0.3, HF is potentially detectable from ground-based
submillimeter observatories in several atmospheric transmission windows.


title:
Cosmological Three-Point Function: Testing The Halo Model Against
  Simulations

abstract:
  We perform detailed comparison of the semi-analytic halo model predictions
with measurements in numerical simulations of the two and three point
correlation functions (3PCF), as well as power spectrum and bispectrum. We
discuss the accuracy and self-consistency of the halo model description of
gravitational clustering in the non-linear regime and constrain halo model
parameters. We exploit the recently proposed multipole expansion of three point
statistics that expresses rotation invariance in the most natural way. This not
only offers technical advantages by reducing the integrals required for the
halo model predictions, but amounts to a convenient way of compressing the
information contained in the 3PCF. We find that, with an appropriate choice of
the halo boundary and mass function cut-off, halo model predictions are in good
agreement with the bispectrum measured in numerical simulations. However, the
halo model predicts less than the observed configuration dependence of the 3PCF
on ~ Mpc scales. This effect is mainly due to quadrupole moment deficit,
possibly related to the assumption of spherical halo geometry. Our analysis
shows that using its harmonic decomposition, the full configuration dependence
of the 3PCF in the non-linear regime can be compressed into just a few numbers,
the lowest multipoles. Moreover, these multipoles are closely related to the
highest signal to noise eigenmodes of the 3PCF. Therefore this estimator may
simplify future analyses aimed at constraining cosmological and halo model
parameters from observational data.


title: Cosmology with Gamma Ray Bursts

abstract:
  Apparently, Gamma-Ray Bursts (GRBs) are all but standard candles. Their
emission is collimated into a cone and the received flux depends on the cone
aperture angle. Fortunately we can derive the aperture angle through an
achromatic steepening of the lightcurve of the afterglow, and thus we can
measure the "true" energetics of the prompt emission. Ghirlanda et al. (2004)
found that this collimation-corrected energy correlates tightly with
thefrequency at which most of the radiation of the prompt is emitted. Through
this correlation we can infer the burst energy accurately enough for a
cosmological use. Using the best known 15 GRBs we find very encouraging results
that emphasize the cosmological GRB role. Probing the universe with high
accuracy up to high redshifts, GRBs establish a new insight on the cosmic
expanding acceleration history and accomplish the role of "missing link"
between the Cosmic Microwave Background and type Ia supernovae, motivating the
most optimistic hopes for what can be obtained from the bursts detected by
SWIFT.


title:
UVBLUE: a new high-resolution theoretical library of ultraviolet stellar
  spectra

abstract:
  We present an extended ultraviolet-blue (850-4700 AA) library of theoretical
stellar spectral energy distributions (SEDs) computed at high resolution, R=
50,000. The UVBLUE grid, as we named the library, is based on LTE calculations
carried out with ATLAS9 and SYNTHE codes developed by R. L. Kurucz and consists
of nearly 1800 entries that cover a large volume of the parameter space. It
spans a range in effective temperature from 3000 to 50,000 K, the surface
gravity ranges from log g= 0.0 to 5.0 with a step of 0.5 dex, while seven
chemical compositions are considered: [Fe/H]= -2.0, -1.5, -1.0, -0.5, +0.0,
+0.3 and +0.5 dex. For its coverage across the H-R diagram, this library is the
most comprehensive one ever computed at high resolution in the short-wavelength
spectral range, and useful application can be foreseen both for the study of
single stars and in population synthesis models of galaxies and other stellar
systems.


title:
SGR giant flares in the BATSE short GRB catalogue: constraints from
  spectroscopy

abstract:
  The giant flare observed on Dec. 27th 2004 from SGR 1806-20 has revived the
idea that a fraction of short (<2 s) Gamma Ray Bursts (GRBs) is due to giant
flares from Soft Gamma Ray Repeaters located in nearby galaxies. One of the
distinguishing characteristics of these events is the thermal (black body)
spectrum with temperatures ranging from ~50 to ~180 keV, with the highest
temperature observed for the initial 0.2 s spike of the Dec. 27th 2004 event.
We analyzed the spectra of a complete sample of short GRBs with peak fluxes
greater than 4 photon s^(-1) cm^(-2) detected by BATSE. Of the 115 short GRBs
so selected only 76 had sufficient signal to noise to allow the spectral
analysis. We find only 3 short GRBs with a spectrum well fitted by a black
body, with 60<kT<90 keV, albeit with a considerably longer duration (i.e. >1
sec) and a more complex light curve than the Dec. 27th 2004 event. This implies
a stringent limit on the rate of extragalactic SGR giant flares with spectral
properties analogous to the Dec. 27th flare. We conclude that up to 4 per cent
of the short GRBs could be associated to giant flares (2 sigma confidence).
This implies that either the distance to SGR 1806-20 is smaller than 15 kpc or
the rate of Galactic giant flares is lower than the estimated 0.033 per year.


title:
Spectral Variability of Quasars in the Sloan Digital Sky Survey. I:
  Wavelength Dependence

abstract:
  Sloan Digital Sky Survey (SDSS) repeat spectroscopic observations have
resulted in multiple-epoch spectroscopy for roughly 2500 quasars observed more
than 50 days apart. From this sample, we identify 315 quasars that have varied
significantly between observations. We create an ensemble difference spectrum
(bright phase minus faint phase) covering rest-frame wavelengths from 1000 to
6000 Angstroms. This average difference spectrum is bluer than the average
single-epoch quasar spectrum; a power-law fit to the difference spectrum yields
a spectral index alpha_lambda = -2.00, compared to an index of alpha_lambda =
-1.35 for the single-epoch spectrum. The strongest emission lines vary only 30%
as much as the continuum. Due to the lack of variability of the lines, measured
photometric color is not always bluer in brighter phases, but depends on
redshift and the filters used. Lastly, the difference spectrum is bluer than
the ensemble quasar spectrum only for lambda_rest < 2500 Angstroms, indicating
that the variability cannot result from a simple scaling of the average quasar
spectrum.


title: The MAGIC Telescope and the Observation of Gamma Ray Bursts

abstract:
  The MAGIC Telescope, now taking data with an energy threshold well below 100
GeV, will soon be able to take full advantage of the fast slewing capability of
its altazimuthal mount. Exploiting the link with the GCN network, the MAGIC
Telescope could be one of the first ground-based experiments able to see the
prompt emission of Gamma Ray Bursts in the few tens of GeV region.


title: Galaxies, Intergalactic Absorption Lines, and Feedback at High Redshift

abstract:
  The galaxy-IGM part of the Lyman-break survey currently consists of measured
redshifts for more than 1000 galaxies with redshift 1.5<z<3.5 along the
sightlines to 25 background QSOs. One of the goals of the survey was to measure
the influence on the intergalactic medium of energetic feedback from star and
black-hole formation. This talk begins with a description of the observed
correlations between galaxies and intergalactic absorption lines and ends with
a discussion of whether any of the observations provide clear evidence for
Mpc-scale superwinds. Although our own observations remain fairly ambiguous,
other observations disfavor a very high redshift (z~10) for the creation of
intergalactic metals.


title: The Afterglows of Ultraluminous Quasars

abstract:
  Quasars represent a brief phase in the life-cycle of most massive galaxies,
but the evolutionary connection between central black holes and their host
galaxies remains unclear. While quasars are active and shining brighter than
the Compton-limit luminosity, their radiation heats the surrounding medium to
the Compton temperature, forming Compton spheres extending to the Str\"omgren
radius of Fe$^{26+}$/He$^{2+}$. After the quasars shut off, their ``afterglow''
can be detected through three signatures: (1) an extended X-ray envelope, with
a characteristic temperature of $\sim 3\times 10^7$ K; (2) Ly$\alpha$ and
Ly$\beta$ lines and the $K-$edge of Fe$^{26+}$; and (3) nebulosity from
hydrogen and helium recombination emission lines. We discuss the possibility of
detecting these signatures using {\em Chandra}, the planned {\em XEUS} mission,
and ground-based optical telescopes. The luminosity and size of quasar
afterglows can be used to constrain the lifetime of quasars.


title: A Library of Integrated Spectra of Galactic Globular Clusters

abstract:
  We present a new library of integrated spectra of 40 Galactic globular
clusters, obtained with the Blanco 4-m telescope and the R-C spectrograph at
the Cerro Tololo Interamerican Observatory. The spectra cover the range ~ 3350
-- 6430 A with ~ 3.1 A (FWHM) resolution. The spectroscopic observations and
data reduction were designed to integrate the full projected area within the
cluster core radii in order to properly sample the light from stars in all
relevant evolutionary stages. The S/N values of the flux-calibrated spectra
range from 50 to 240/A at 4000 A and from 125 to 500/A at 5000 A. The selected
targets span a wide range of cluster parameters, including metallicity,
horizontal-branch morphology, Galactic coordinates, Galactocentric distance,
and concentration. The total sample is thus fairly representative of the entire
Galactic globular cluster population and should be valuable for comparison with
similar integrated spectra of unresolved stellar populations in remote systems.
For most of the library clusters, our spectra can be coupled with deep
color-magnitude diagrams and reliable metal abundances from the literature to
enable the calibration of stellar population synthesis models. In this paper we
present a detailed account of the observations and data reduction. The spectral
library is publicly available in electronic format from the National Optical
Astronomical Observatory website.


title:
On the effect of the inhomogeneous subsurface flows on the high degree
  solar p-modes

abstract:
  The observed power spectrum of high-degree solar p-modes (l>200) shows
discrepancies with the power spectrum predicted by the stochastic excitement
and damping theory. In an attempt to explain these discrepancies, the present
paper is concerned with the influence of the observed subsurface flows on the
trapped acoustic modes (p-modes). The effect of these inhomogeneous background
flows is investigated by means of a non-modal analysis and a multi-layer model.
It is shown that the rotational and meridional components of the velocity field
change the wavelengths of the oscillation modes which, in turn, results in
modifications of the corresponding modal frequencies. The magnitudes of the
frequency residuals depend on the spatial scales of the modes and on the
gradients of the different components of the flow velocity. Together with other
mechanisms (e.g. the scattering of modes by the large scale convection
(Goldreich & Murray 1994), the non-modal effect of the variation of the
frequencies in time may contribute: 1) to the observed widening of the
corresponding peaks in the observed power spectrum with increasing angular
degree; 2) to the partial dissipation of spectral power, and, as a result, 3)
to the discrepancies between the predicted and the observed power spectrum of
solar p-modes.


title:
Testing homogeneity on large scales in the Sloan Digital Sky Survey Data
  Release One

abstract:
  The assumption that the universe is homogeneous and isotropic on large scales
is one of the fundamental postulates of cosmology. We have tested the large
scale homogeneity of the galaxy distribution in the Sloan Digital Sky Survey
Data Release One (SDSS-DR1) using volume limited subsamples extracted from the
two equatorial strips which are nearly two dimensional (2D). The galaxy
distribution was projected on the equatorial plane and we carried out a 2D
multi-fractal analysis by counting the number of galaxies inside circles of
different radii in the range 5 Mpc/h to 150 Mpc/h centred on galaxies.
Different moments of the count-in-cells were analysed to identify a range of
length-scales (60-70 Mpc/h to 150Mpc/h) where the moments show a power law
scaling behaviour and to determine the scaling exponent which gives the
spectrum of generalised dimension D_q. If the galaxy distribution is
homogeneous, D_q does not vary with q and is equal to the Euclidean dimension
which in our case is 2. We find that D_q varies in the range 1.7 to 2.2. We
also constructed mock data from random, homogeneous point distributions and
from LCDM N-body simulations with bias b=1, 1.6 and 2, and analysed these in
exactly the same way. The values of D_q in the random distribution and the
unbiased simulations show much smaller variations and these are not consistent
with the actual data. The biased simulations, however, show larger variations
in D_q and these are consistent with both the random and the actual data.
Interpreting the actual data as a realisation of a biased LCDM universe, we
conclude that the galaxy distribution is homogeneous on scales larger than
60-70 Mpc/h.


title:
Kinematics, ages and metallicities for F and G type stars in the solar
  neighbourhood

abstract:
  A new metallicity distribution and an age-metallicity relation are presented
for 437 nearby F and G turn-off and sub-giant stars selected from radial
velocity data of Nidever et al. Photometric metallicities are derived from
uvby-H\beta photometry, and the stellar ages from the isochrones of Bergbusch &
VandenBerg as transformed to $uvby$ photometry using the methods of Clem et al.
The X (stellar-population) criterion of Schuster et al., which combines both
kinematic and metallicity information, provides 22 thick-disk stars.
\sigma_{\rm W} = 32 \pm 5 km s^{-1}, <V_{\rm rot}> = 154 \pm 6 km s^{-1} and
<[M/H]> = -0.55 \pm 0.03 dex for these thick-disk stars, which is in agreement
with values from previous studies of the thick disk. \alpha -element abundances
which are available for some of these thick-disk stars show the typical
alpha-element signatures of the thick disk, supporting the classification
procedure based on the $X$ criteria. Both the scatter in metallicity at a given
age and the presence of old, metal-rich stars in the age-metallicity relation
make it difficult to decide whether or not an age-metallicity relation exists
for the older thin-disk stars. For ages greater than 3 Gyr, our results agree
with the other recent studies that there is almost no correlation between age
and metallicity, \Delta ([M/Fe])/\Delta(age) = -0.01 \pm 0.005 dex Gyr^{-1}.
For the 22 thick-disk stars there is a range in ages of 7-8 Gyr, but again
almost no correlation between age and metallicity.


title:
Three-dimensional modeling of Type Ia supernovae - The power of late
  time spectra

abstract:
  Late time synthetic spectra of Type Ia supernovae, based on three-dimensional
deflagration models, are presented. We mainly focus on one
model,"c3_3d_256_10s", for which the hydrodynamics (Roepke 2005) and
nucleosynthesis (Travaglio et al. 2004) was calculated up to the homologous
phase of the explosion. Other models with different ignition conditions and
different resolution are also briefly discussed. The synthetic spectra are
compared to observed late time spectra. We find that while the model spectra
after 300 to 500 days show a good agreement with the observed Fe II-III
features, they also show too strong O I and C I lines compared to the observed
late time spectra. The oxygen and carbon emission originates from the
low-velocity unburned material in the central regions of these models. To get
agreement between the models and observations we find that only a small mass of
unburned material may be left in the center after the explosion. This may be a
problem for pure deflagration models, although improved initial conditions, as
well as higher resolution decrease the discrepancy. The relative intensity from
the different ionization stages of iron is sensitive to the density of the
emitting iron-rich material. We find that clumping, with the presence of low
density regions, is needed to reproduce the observed iron emission, especially
in the range between 4000 and 6000 AA. Both temperature and ionization depend
sensitively on density, abundances and radioactive content. This work therefore
illustrates the importance of including the inhomogeneous nature of realistic
three-dimensional explosion models. We briefly discuss the implications of the
spectral modeling for the nature of the explosion.


title:
The ABC of low-frequency quasi-periodic oscillations in Black-Hole
  Candidates: analogies with Z-sources

abstract:
  Three main types of low-frequency quasi-periodic oscillations (LFQPOs) have
been observed in Black Hole Candidates. We re-analyzed RXTE data of the bright
systems XTE J1859+226, XTE J1550-564 and GX 339-4, which show all three of
them. We review the main properties of these LFQPOs and show that they follow a
well-defined correlation in a fractional rms vs. softness diagram. We show that
the frequency behavior through this correlation presents clear analogies with
that of Horizontal-, Normal- and Flaring-Branch Oscillations in Z sources, with
the inverse of the fractional rms being the equivalent of the curvilinear
coordinate Sz through the Z track.


title:
Strong CaII absorption lines in the reddened quasar SDSS J2339$-$0912:
  Evidence of the collision/merger in the host galaxy?

abstract:
  We report the detection of strong CaII/MgII absorption lines at the quasar
redshift in the narrow line quasar SDSS J2339-0912 (z=0.6604). The quasar
exhibits strong FeII, small Balmer emission line width and a very red B-Ks
color. Both the optical continuum and broad emission lines are reddened by
SMC-like dust of E(B-V)~1.0 mag, while its near-infrared color (J-Ks=1.60)
shows little reddening. The CaII absorption lines are saturated and resolved
with an FWHM of 362 km/s and an equivalent width of W_{CaII K}=4.2\AA (in the
source rest frame). MgII absorption lines are also saturated and have a similar
line width. The line profile and the fact that there is no evidence for
starlight from the host galaxy suggest that these absorption lines are not of a
stellar origin. The ratio of column density of CaII to that of dust is
consistent with that of the ISM in our Galaxy. We suggest that both the heavy
reddening and the large absorption line width are due to the highly disturbed
ISM on the line of sight toward the quasar, and that the disturbance is caused
by a galaxy collision or even merger in the quasar host galaxy.


title: Two extreme double-peaked line emitters in the Sloan Digital Sky Survey

abstract:
  Double-peaked Balmer lines have been observed in about 150 AGNs and were
interpreted preferably as emission from relativistic accretion disks. In this
paper, we report the discovery of extreme double-peaked lines in SDSS
J0942+0900 and SDSS J1417+6141. The FWHM of the Halpha line ~40,600 km/s in the
first object is almost twice as large as the broadest one previously known. By
comparing the line profile with accretion disk models, we find that most of the
line flux is emitted from a narrow annulus around 100Rg in SDSS J0942+0900, and
from a disk of radii between 100 and 400Rg in SDSS J1417+6141. This is the
first time that an accretion disk at radii below 100Rg can be directly probed
through optical emission lines. A certain asymmetry in the disk is required for
both objects. Another much weaker broad Halpha component (EW~20A, and FWHM
4000km/s) is also detected in both objects. Both objects show weak radio
emission and strong high-ionization narrow lines.


title: Optical novae: the major class of supersoft X-ray sources in M 31

abstract:
  We searched for X-ray counterparts of optical novae detected in M 31 and M
33. We combined an optical nova catalogue from the WeCAPP survey with optical
novae reported in the literature and correlated them with the most recent X-ray
catalogues from ROSAT, XMM-Newton and Chandra, and - in addition - searched for
nova correlations in archival data. We report 21 X-ray counterparts for novae
in M 31 - mostly identified as supersoft sources (SSS) by their hardness ratios
- and two in M 33. Our sample more than triples the number of known optical
novae with supersoft X-ray phase. Most of the counterparts are covered in
several observations allowing us to constrain their X-ray light curves.
Selected brighter sources were classified by their XMM-Newton EPIC spectra. We
use the well determined start time of the SSS state in two novae to estimate
the hydrogen mass ejected in the outburst to ~10^{-5}M_sun and ~10^{-6}M_sun,
respectively. The supersoft X-ray phase of at least 15% of the novae starts
within a year. At least one of the novae shows a SSS state lasting 6.1 years
after the optical outburst. Six of the SSSs turned on between 3 and 9 years
after the optical discovery of the outburst and may be interpreted as recurrent
novae. If confirmed, the detection of a delayed SSS phase turn-on may be used
as a new method to classify novae as recurrent. At the moment, the new method
yields a ratio of recurrent novae to classical novae of 0.3 which is in
agreement (within the errors) with previous works.


title:
Optimal column density measurements from multiband near-infrared
  observations

abstract:
  We consider from a general point of view the problem of determining the
extinction in dense molecular clouds. We use a rigorous statistical approach to
characterize the properties of the most widely used optical and infrared
techniques, namely the star count and the color excess methods. We propose a
new maximum-likelihood method that takes advantage of both star counts and star
colors to provide an optimal estimate of the extinction. Detailed numerical
simulations show that our method performs optimally under a wide range of
conditions and, in particular, is significantly superior to the standard
techniques for clouds with high column-densities and affected by contamination
by foreground stars.


title:
Sgr A East as a possible high energy neutron factory in the Galactic
  Centre

abstract:
  Sgr A East is a supernova remnant located within few parsecs from the
Galactic Centre (GC). There are good reasons to believe that this object is the
source of the gamma-ray excess detected by HESS in the direction of the GC
meaning that Sgr A East is likely to be an efficient Cosmic Ray accelerator.
Some observations suggest that strong magnetic fields may be present in that
region allowing the acceleration of composite nuclei in Sgr A East beyond the
EeV. We show that, if this is case, EeV neutrons should be effectively produced
by the photo-disintegration of Ultra High Energy nuclei onto the IR photon
background (with temperature $\sim 40$ K) in which Sgr A East is embedded.
  Neutrons with such an energy can reach the Earth before decaying and may be
detectable under the form of a CR point-like excess in the direction of the GC.
  We determine the expected energy spectrum and the amplitude of this signal
showing that it may be measurable by the AUGER observatory.


title: The C star outer disk population of M31 seen with the SLOAN filters

abstract:
  We employ the CFHT Megacam camera to survey ~ one deg$^2$ of the southern
outer disc of M31, a region which includes the area where Battinelli et al.
(2003) have identified nearly one thousand C stars. In the outer M31 region not
previously surveyed, we identify 361 new C star candidates, having similar
photometric properties to the known ones, and confirm theslight decrease in the
luminosity of C stars with galactocentric distances. We show that the Sloan g',
r', i' filters are a viable approach, comparable to (CN - TiO), to identify C
stars. We find that the (g' - r') colours of cool C stars can be so red that
prohibitively long g' exposures are needed to acquire faint extragalactic C
stars. This makes the Sloan filters a less promising approach to extend a C
star survey to several Mpc. Our uniform large field survey detects the edge of
M31 disk at ~ 35 kpc. The intermediate-age population, represented by C stars,
extends further to ~ 40 kpc.


title: SPI energy calibration

abstract:
  The status of the SPI energy calibration after the first year of INTEGRAL
operations is reported. We have studied the gain variations and we have
demonstrated that the most important parameter is the germanium detector
temperature. This study permits us to determine the limits of our calibration
method and the frequency of calibrations needed.


title:
Angular diameter measurements of evolved variables by lunar occultations
  at 2.2 and 3.8 micron

abstract:
  We report the angular diameters of two Mira variables (U Ari and Z Sco),
three semiregular (SR) and irregular variables (SW Vir, eta Gem and mu Gem) and
a supergiant SR variable (TV Gem) by lunar occultation observations in the
near-IR broad K-band (2.2 micron). Lunar occultations of eta Gem and mu Gem
were also observed for the first time simultaneously in both the K and L'
bands, yielding angular diameters at 2.2 and 3.8 micron. Effective temperatures
and linear radii are also derived for all the observed sources and compared
with earlier measurements. The mode of pulsation of both Mira and SR sources in
our sample is discussed.


title:
Iron abundances derived from RR Lyrae light curves and low-dispersion
  spectroscopy

abstract:
  With the aid of the All Sky Automated Survey (ASAS) database on the Galactic
field, we compare the iron abundances of fundamental mode RR Lyrae stars
derived from the Fourier parameters with those obtained from low-dispersion
spectroscopy. We show from a set of 79 stars, distinct from the original
calibrating sample of the Fourier method and selected without quality control,
that almost all discrepant estimates are the results of some defects or
peculiarities either in the photometry or in the spectroscopy. Omitting objects
deviating by more than 0.4dex, the remaining subsample of 64 stars yields
Fourier abundances that fit the spectroscopic ones with a standard deviation of
0.20dex. Other, more stringent selection criteria and different Fourier
decompositions lead to smaller subsamples and concomitant better agreement,
down to 0.16dex standard deviation. Except perhaps for two variables among the
163 stars, comprised of the ASAS variables and those of the original
calibrating set of the Fourier method, all discrepant values can be accounted
for by observational noise and insufficient data coverage. We suggest that the
agreement can be further improved when new, more accurate spectroscopic data
become available for a test with the best photometric data. As a by-product of
this analysis, we also compute revised periods and select Blazhko variables.


title: Protoneutron star dynamos and pulsar magnetism

abstract:
  We have investigated the turbulent mean-field dynamo action in protoneutron
stars that are subject to convective and neutron finger instabilities during
the early evolutionary phase. While the first one develops mostly in the inner
regions of the star, the second one is favored in the outer regions, where the
Rossby number is much smaller and a mean-field dynamo action is more efficient.
By solving the mean-field induction equation we have computed the critical spin
period below which no dynamo action is possible and found it to be $\sim 1$ s
for a wide range of stellar models and for both axisymmetric and
non-axisymmetric magnetic fields. Because this critical period is substantially
longer than the characteristic spin period of very young pulsars, we expect
that a mean-field dynamo will be effective for most protoneutron stars. The
saturation dipole field estimated by making use of the model of ``global''
quenching fits well the pulsar magnetic fields inferred from the spin-down
data. Apart from the large scale magnetic field, our model predicts also a
generation of small scale fields which are typically stronger than the poloidal
field and can survive during the lifetime of pulsars. Extremely rapidly
rotating protoneutron stars ($P \sim 1$ ms) may have the dipole field $\sim
(3-6) \times 10^{14}$ G.


title: An XMM-Newton observation of Mrk 3 - a Seyfert galaxy just over the edge

abstract:
  A 100ks XMM-Newton observation of the nearby Seyfert 2 galaxy Mrk 3 offers a
unique opportunity to explore the complexity of its X-ray spectrum. We find the
\~3-8 keV continuum to be dominated by reflection from cold matter, with
fluorescent K-shell lines detected from Ni, Fe, Ca, Ar, S, Si and Mg. At higher
energies an intrinsic power law continuum, with canonical Seyfert 1 photon
index, is seen through a near-Compton-thick cold absorber. A soft excess below
\~3 keV is found to be dominated by line emission from an outflow of `warm'
gas, photo-ionised and photo-excited by the intrinsically strong X-ray
continuum. Measured blue-shifts in the strong Fe K-alpha and OVII and VIII
emission lines are discussed in terms of the properties of the putative
molecular torus and ionised outflow.


title:
HST/STIS low dispersion spectroscopy of three Compact Steep Spectrum
  sources Evidence for jet-cloud interaction

abstract:
  We present Hubble Space Telescope Imaging Spectrograph long-slit spectroscopy
of the emission line nebulae in the compact steep spectrum radio sources 3C 67,
3C 277.1, and 3C 303.1. We derive BPT (Baldwin- Philips-Terlevich; Baldwin et
al. 1981) diagnostic emission line ratios for the nebulae which are consistent
with a mix of shock excitation and photoionization in the extended gas. In
addition, line ratios indicative of lower ionization gas are found to be
associated with higher gas velocities. The results are consistent with a
picture in which these galaxy scale radio sources interact with dense clouds in
the interstellar medium of the host galaxies, shocking the clouds thereby
ionizing and accelerating them.


title: Swift observations of GRB050128: the early X-ray afterglow

abstract:
  Swift discovered GRB050128 with the Burst Alert Telescope and promptly
pointed its narrow field instruments to monitor the afterglow. X-ray
observations started 108 s after the trigger time. The early decay of the
afterglow is relatively flat with a temporal decay modeled with a power law
with index ~ -0.3. A steepening occurs at later times (~ 1500 s) with a power
law index of ~ -1.3. During this transition, the observed X-ray spectrum does
not change. We interpret this behaviour as either an early jet break or
evidence for a transition from the fast cooling regime to the slow cooling
regime in a wind environment.


title: Orbital Parameters of the Microquasar LSI +61 303

abstract:
  New optical spectroscopy of the HMXB microquasar LSI +61 303 is presented.
Eccentric orbital fits to our radial velocity measurements yield updated
orbital parameters in good agreement with previous work. Our orbital solution
indicates that the periastron passage occurs at radio phase 0.23 and the
X-ray/radio outbursts are triggered 2.5--4 days after the compact star passage.
The spectrum of the optical star is consistent with a B0 V spectral type and
contributes ~65 percent of the total light, the remaining due to emission by a
circumstellar disc. We also measure the projected rotational velocity to be v
sin i = 113 km/s.


title:
RR Lyrae search and stellar populations study in Canis Major:
  Preliminary Results

abstract:
  We present preliminary results of a RR Lyrae star search and stellar
populations study performed in the Canis Major overdensity, spanning an area of
8.35sq deg. The observations were made in R and V bands, with the QUEST camera
installed in the 1m Jurgen Stock Telescope, at the Venezuela National
Observatory. The resulting Hess diagram shows a possible, but weak, red giant
branch and no obvious horizontal branch, red clump or main sequence turnoff.
After a multi--epoch photometric search, 6 RR Lyrae stars were confirmed with
further observations obtained at the 1.0 and 1.3m telescopes of the SMARTS
consortium at CTIO. Of these confirmed RR Lyrae stars, 5 have heliocentric
distances between 5 and 7 kpc. Confirmation of their physsical association with
the Canis Major system awaits for a study of their radial velocities.


title: A Simple and Accurate Model for Intra-Cluster Gas

abstract:
  Starting with the well-known NFW dark matter halo distribution, we construct
a simple polytropic model for the intracluster medium which is in good
agreement with high resolution numerical hydrodynamical simulations, apply this
model to a very large scale concordance dark matter simulation, and compare the
resulting global properties with recent observations of X-ray clusters,
including the mass-temperature and luminosity-temperature relations. We make
allowances for a non-negligible surface pressure, removal of low entropy (short
cooling time) gas, energy injection due to feedback, and for a relativistic
(non-thermal) pressure component. A polytropic index n=5 (Gamma=1.2) provides a
good approximation to the internal gas structure of massive clusters (except in
the very central regions where cooling becomes important), and allows one to
recover the observed M_500-T, L_x-T, and T/n_e^{2/3} ~ T^0.65 relations. Using
these concepts and generalizing this method so that it can be applied to fully
three-dimensional N-body simulations, one can predict the global X-ray and SZE
trends for any specified cosmological model. We find a good fit to observations
when assuming that twelve percent of the initial baryonic mass condenses into
stars, the fraction of rest mass of this condensed component transferred back
to the remaining gas (feedback) is 3.9E-5, and the fraction of total pressure
from a nonthermal component is near ten percent.


title: The Globular Cluster Content of Maffei 1

abstract:
  Near-infrared images have been used to search for bright globular clusters
near the center of the elliptical galaxy Maffei 1. The number of objects in
various radial intervals from the center of Maffei 1 are compared with the
number density of sources in two control fields, and we find an excess of 31
+/- 11 objects with K between 16.6 and 18.0 in an annulus between 20 and 90
arcsec from the galaxy center. At radii in excess of 90 arcsec the ability to
find clusters is frustrated by statistical noise in the foreground star
population. It is demonstrated that the globular clusters located within 90
arcsec of the center of Maffei 1 span a range of near-infrared colors that are
at least as great as that which is seen among M31 clusters; some of the
clusters appear to have colors that are consistent with them being very young.
The specific globular cluster frequency within 90 arcsec of the center of
Maffei 1 is S_N = 1.3 +/- 0.6 if the distance modulus is 28.1 +/- 0.2 and A_V =
4.7 +/- 0.2. The specific cluster frequency of Maffei 1 is thus similar to that
of other nearby field elliptical galaxies.


title:
Spitzer Detection of PAH and Silicate Dust Features in the Mid-Infrared
  Spectra of z~2 Ultraluminous Infrared Galaxies

abstract:
  We report the initial results from a Spitzer GO-1 program to obtain low
resolution, mid-infrared spectra of infrared luminous galaxies at z~1-2. This
paper presents the spectra of eight sources observed with the Spitzer InfraRed
Spectrograph (IRS). Of the eight spectra, six have mid-IR spectral features,
either emission from Polycyclic Aromatic Hydrocarbon (PAH) or silicate
absorption. Based on these mid-IR features, the inferred six redshifts are in
the range of 1.8-2.6. The remaining two spectra detect only strong continua,
thus do not yield redshift information. Strong, multiple PAH emission features
are detected in two sources, and weak PAH emission in another two. These data
provide direct evidence that PAH molecules are present and directly observable
in ULIRGs at z~2.
  The six sources with measured redshifts are dusty, infrared luminous galaxies
at z~2 with estimated $L_{bol} \sim 10^{13}L_\odot$. Of the eight sources, two
appear starburst dominated; two with only power law continua are probably type
I QSOs; and the remaining four are likely composite systems containing a buried
AGN and a starburst component. Since half of our sample are optically faint
sources with R>25.5mag (Vega), our results demonstrate the potential of using
mid-infrared spectroscopy, especially the Aromatic and silicate features
produced by dust grains to directly probe optically faint and infrared luminous
populations at high redshift.


title:
The Effective Temperature Scale of Galactic Red Supergiants: Cool, But
  Not As Cool As We Thought

abstract:
  We use moderate-resolution optical spectrophotometry and the new MARCS
stellar atmosphere models to determine the effective temperatures of 74
Galactic red supergiants. From these we find a new effective temperature scale
that is significantly warmer than those in the literature. We show that this
temperature scale, along with the newly derived bolometric corrections, gives
much better agreement between our red supergiants and stellar evolutionary
tracks. This agreement provides an independent verification of our new
temperature scale. The combination of effective temperature and bolometric
luminosities allows us to calculate stellar radii; the coolest and most
luminous stars have radii of roughly 1500 solar radii (7 AU), in excellent
accordance with the largest stellar radii predicted from current evolutionary
theory. We find that similar results are obtained for the effective
temperatures and bolometric luminosities using only the de-reddened V-K colors,
providing a powerful demonstration of the self-consistency of the MARCS models.


title: Dwarf spheroidal galaxies in nearby groups imaged with HST

abstract:
  An all-sky list of 88 nearby dwarf spheroidal (dSph) galaxies with distances
D < 10 Mpc is considered. Most of the objects have recently been found by
Karachentseva & Karachentsev based on POSSII/ESO-SERC survey. A hundred more
dSph galaxies are expected in this volume, being missed so far because of their
low luminosity and low surface brightness. Apart from 22 dSph members of the
Local Group, there are 33 dSphs in other nearby groups that have been resolved
recently into stars with HST. Only 5% of the local dSphs are situated outside
the known groups. We discuss observational correlation between basic parameters
of the dwarf spheroidal galaxies, in particular, absolute magnitude, surface
brightness, metallicity, and so-called "tidal index". The observed number of
dSphs in group increases with luminosity of its brightest galaxy. In a
"synthetic" nearby group, dwarf spheroidal galaxies are distributed in depth
quite symmetrically about the principal galaxy, having an rms distance scatter
of 200 kpc. Projected radial distribution of dSphs in the synthetic group
follows the profile N(R) ~ exp(-R/200 kpc).


title: On the Sr I 4607 A Hanle depolarization signals in the quiet Sun

abstract:
  The Hanle depolarization signals of Sr 4607 A have been used to estimate the
unsigned magnetic flux and magnetic energy existing in the quiet Sun
photosphere. However, the Sr 4607 A Hanle signals are not sensitive to the
unsigned flux and energy. They only bear information on the fraction of
photosphere occupied by magnetic field strengths smaller than the Hanle
saturation, which do not contribute to the unsigned flux and energy. We deduce
an approximate expression for the relationship between magnetic fill factor and
Hanle signal. When applied to existing Hanle depolarization measurements, it
indicates that only 40% of the quiet Sun is filled by magnetic fields with a
strength smaller than 60 G. The remaining 60% of the surface has field
strengths above this limit. Such constraint will be needed to determine the
distribution of magnetic field strengths existing in the quiet Sun.


title: Can hidden correlations mimic a variable fine structure constant?

abstract:
  Murphy et al. (2003a, MNRAS, 345, 609) claim to find evidence of cosmological
variations of the fine structure constant $\alpha$ in the spectra of
intervening QSO absorption line systems. We find that this result is affected
by systematic effects. The $\alpha$ values estimated in individual line systems
depend on the set of atomic transitions used and therefore the quoted
dependence on the cosmic age may reflect the fact that different sets of
transitions are used at different redshifts. A correlation between line shifts
and relative optical depths of the atomic transitions is also present. This
correlation is very tight for a high-redshift subsample and accounts for the
anomalous dispersion of the $\alpha$ values found by Murphy et al. (2003a) in
this subsample. The above correlations are consistent with a scenario in which
gravitational redshift, caused by the gravity of the dark halo, contributes to
the shift in frequency of individual components. Gravitational redshift causes
differential spectral shifts of the same order as magnitude of those measured.
In the presence of line misidentification, these shifts can be interpreted in
terms of a variable $\alpha$. In order to verify the gravitational redshift
hypothesis, a direct access to Murphy et al. (2003a) data, or to a large amount
of new high resolution data, is necessary.


title: Outbursts on normal stars. FH Leo misclassified as a novalike variable

abstract:
  We present high resolution spectroscopy of the common proper motion system FH
Leo (components HD 96273 and BD+07 2411B), which has been classified as a
novalike variable due to an outburst observed by Hipparcos, and we present and
review the available photometry. We show from our spectra that neither star can
possibly be a cataclysmic variable, instead they are perfectly normal late-F
and early-G stars. We measured their radial velocities and derived the
atmospheric fundamental parameters, abundances of several elements including
Fe, Ni, Cr, Co, V, Sc, Ti, Ca and Mg, and we derive the age of the system. From
our analysis we conclude that the stars do indeed constitute a physical binary.
However, the observed outburst cannot be readily explained. We examine several
explanations, including pollution with scattered light from Jupiter, binarity,
microlensing, background supernovae, interaction with unseen companions and
planetary engulfment. While no explanation is fully satisfactory, the scattered
light and star-planet interaction scenarios emerge as the least unlikely ones,
and we give suggestions for further study.


title: On the massive stellar population of the Super Star Cluster Westerlund 1

abstract:
  We present new spectroscopic and photometric observations of the young
Galactic open cluster Westerlund 1 (Wd 1) that reveal a unique population of
massive evolved stars. We identify ~200 cluster members and present
spectroscopic classifications for ~25% of these. We find that all stars so
classified are unambiguously post-Main Sequence objects, consistent with an
apparent lack of an identifiable Main Sequence in our photometric data to V~20.
We are able to identify rich populations of Wolf Rayet stars, OB supergiants
and short lived transitional objects. Of these, the latter group consists of
both hot (Luminous Blue Variable and extreme B supergiants) and cool (Yellow
Hypergiant and Red Supergiant) objects - we find that half the known Galactic
population of YHGs resides within Wd1. We obtain a mean V-M_V ~25 mag from the
cluster Yellow Hypergiants, implying a Main Sequence turnoff at or below M_V
=-5 (O7 V or later). Based solely on the masses inferred for the 53
spectroscopically classified stars, we determine an absolute minimum mass of
\~1.5 x 10^3 Msun for Wd 1. However, considering the complete photometrically
and spectroscopically selected cluster population and adopting a Kroupa IMF we
infer a likely mass for Wd 1 of ~10^5 Msun, noting that inevitable source
confusion and incompleteness are likely to render this an underestimate. As
such, Wd 1 is the most massive compact young cluster yet identified in the
Local Group, with a mass exceeding that of Galactic Centre clusters such as the
Arches and Quintuplet. Indeed, the luminosity, inferred mass and compact nature
of Wd 1 are comparable with those of Super Star Clusters - previously
identified only in external galaxies - and is consistent with expectations for
a Globular Cluster progenitor.


title:
Optimization of time data codification and transmission schemes:
  Application to Gaia

abstract:
  Gaia is an ambitious space observatory devoted to obtain the largest and most
precise astrometric catalogue of astronomical objects from our Galaxy and
beyond. On-board processing and transmission of the huge amount of data
generated by the instruments is one of its several technological challenges.
The measurement time tags are critical for the scientific results of the
mission, so they must be measured and transmitted with the highest precision -
leading to an important telemetry channel occupation. In this paper we present
the optimisation of time data, which has resulted in a useful software tool. We
also present how time data is adapted to the Packet Telemetry standard. The
several communication layers are illustrated and a method for coding and
transmitting the relevant data is described as well. Although our work is
focused on Gaia, the timing scheme and the corresponding tools can be applied
to any other instrument or mission with similar operational principles.


title: FIRBACK IV: Towards the nature of the 170microns source population

abstract:
  We present a detailed study of the brighter ($> 4\sigma$ detections) sources
in the 170$\mu$m FIRBACK northern N1 ISO survey, with the help of complementary
data in the optical, radio, and mid-IR domain. For 82% of them, an optical
galaxy counterpart is identified, either as the unique source of the IR
emission, or as part of a multiple identification. With less than 15% of AGNs,
these sources are essentially local, moderate starbursters with a dominating
cold dust component. and represent a population of cold galaxies rather
neglected up to now. Their colours do not match those of the far-IR Cosmic IR
Background (CIB), to which they contribute less than 5%. The bulk of the
sources contributing to the CIB is thus to be searched for in more distant
galaxies, possibly counterparts of the fainter FIRBACK sources still under
study. These bright, local, galaxies however play an important role in the
evolution of IR galaxies: they dominate the number counts at high 170 $\mu$m
fluxes, and represent half of the contribution at 250 mJy. Although not
particularly massive (typically M*), they form more stars than a typical spiral
galaxy and many are bulge dominated, that could represent the remnant of a
former merger. The fainter part of this population may represent the missing
link with the higher-z sources found in sub-mm observations.


title: Simulation of the clock framework of Gaia

abstract:
  Gaia will perform astrometric measurements with an unprecedented resolution.
Consequently, the electronics of the Astro instrument must time tag every
measurement with a precision of a few nanoseconds. Hence, it requires a high
stability clock signal, for which a Rb-type spacecraft master clock has been
baselined. The distribution of its signal and the generation of clock
subproducts must maintain these high accuracy requirements. We have developed a
software application to simulate generic clock frameworks. The most critical
clock structures for Gaia have also been identified, and its master clock has
been parameterised.


title: Peak energy clustering and efficiency in compact objects

abstract:
  We study the properties of plasmas containing a low energy thermal photon
component at comoving temperature \theta \equiv kT'/m_e c^2 \sim 10^{-5} -
10^{-2} interacting with an energetic electron component, characteristic of,
e.g., the dissipation phase of relativistic outflows in gamma-ray bursts
(GRB's), X-ray flashes, and blazars. We show that, for scattering optical
depths larger than a few, balance between Compton and inverse-Compton
scattering leads to the accumulation of electrons at values of $\gamma\beta ~
0.15 - 0.3$. For optical depths larger than ~ 100, this leads to a peak in the
comoving photon spectrum at 1-10 keV, very weakly dependent on the values of
the free parameters. In particular, these results are applicable to the
internal shock model of GRB, as well as to slow dissipation models, e.g. as
might be expected from reconnection, if the dissipation occurs at a
sub-photospheric radii. For GRB bulk Lorentz factors ~ 100, this results in
observed spectral peaks clustering in the 0.1-1 MeV range, with conversion
efficiencies of electron into photon energy in the BATSE range of ~ 30%.


title:
The Reionization History and Early Metal Enrichment inferred from the
  Gamma-Ray Burst Rate

abstract:
  Based on the gamma-ray burst (GRB) event rate at redshifts of $4 \leq z \leq
12$, which is assessed by the spectral peak energy-to-luminosity relation
recently found by Yonetoku et al., we observationally derive the star formation
rate (SFR) for Pop III stars in a high redshift universe. As a result, we find
that Pop III stars could form continuously at $4 \leq z \leq 12$. Using the
derived Pop III SFR, we attempt to estimate the ultraviolet (UV) photon
emission rate at $7 \leq z \leq 12$ in which redshift range no observational
information has been hitherto obtained on ionizing radiation intensity. We find
that the UV emissivity at $7 \leq z \leq 12$ can make a noticeable contribution
to the early reionization. The maximal emissivity is higher than the level
required to keep ionizing the intergalactic matter at $7 \leq z \leq 12$.
However, if the escape fraction of ionizing photons from Pop III objects is
smaller than 10%, then the IGM can be neutralized at some redshift, which may
lead to the double reionization. As for the enrichment, the ejection of all
metals synthesized in Pop III objects is marginally consistent with the IGM
metallicity, although the confinement of metals in Pop III objects can reduce
the enrichment significantly.


title: Simulating galaxy clusters : the ICM and the galaxy populations

abstract:
  Cosmological LambdaCDM TreeSPH simulations of the formation and evolution of
galaxy groups and clusters have been performed. The simulations include: star
formation, chemical evolution with non-instantaneous recycling, metal dependent
radiative cooling, strong star burst and (optionally) AGN driven galactic super
winds, effects of a meta-galactic UV field and thermal conduction. We report
results on the temperature and entropy profiles of the ICM, the X-ray
luminosity, cold fraction, M/L and IMLR ratios in gas and stars, metal
abundances and gradients. Besides, the properties of the galaxy populations in
the two richest clusters are discussed: global star formation rates of the
cluster galaxies, the total K-band luminosity, the galaxy luminosity functions
at z=0 and their redshift evolution, the colour-magnitude relation (``red
sequence'') as resulting from metallicity effects, and the role of the IMF in
reproducing colours and abundances of the stellar populations. Finally the
contribute (20-40 %) to cluster light from the intra-cluster stars and the cD
galaxy has been investigated: surface brightness profiles, mean colours and
chemical abundances, kinematics (velocity dispersion and distributions) of the
IC stellar populations.


title:
The Molecular Condensations Ahead of Herbig-Haro Objects. III. Radiative
  and dynamical perturbations of the HH 2 condensation

abstract:
  We have carried out an extensive observational study (from BIMA data) and
made a preliminary theoretical investigation of the molecular gas around HH2.
The molecular maps show a very complex morphological, kinematical and chemical
structure. The overall main conclusion of this work confirms the findings of
Paper I and II, by demonstrating that in addition to the strong photochemical
effects caused by penetration of the UV photons from HH2 into molecular cloud,
a range of complex radiative and dynamical interactions occur. Thus, despite
the apparent `quiescent' nature of the molecular cloud ahead of HH2, the
kinematical properties observed within the field of view suggest that it is
possibly being driven out by powerful winds from the VLA 1 protostar.


title: The powerful outburst in Hercules A

abstract:
  The radio source Hercules A resides at the center of a cooling flow cluster
of galaxies at redshift z = 0.154. A Chandra X-ray image reveals a shock front
in the intracluster medium (ICM) surrounding the radio source, about 160 kpc
from the active galactic nucleus (AGN) that hosts it. The shock has a Mach
number of 1.65, making it the strongest of the cluster-scale shocks driven by
an AGN outburst found so far. The age of the outburst ~5.9e7 y, its energy
about 3e61 erg and its mean power ~1.6e46 erg/s. As for the other large AGN
outbursts in cooling flow clusters, this outburst overwhelms radiative losses
from the ICM of the Hercules A cluster by a factor of ~100. It adds to the case
that AGN outbursts are a significant source of preheating for the ICM. Unless
the mechanical efficiency of the AGN in Hercules A exceeds 10%, the central
black hole must have grown by more than 1.7e8 Msun to power this one outburst.


title:
A comparison of superradiance and negative-phase-velocity phenomenons in
  the ergosphere of a rotating black hole

abstract:
  The propagation of electromagnetic plane waves with negative phase velocity
(NPV) in the ergosphere of a rotating black hole has recently been reported. A
comparison of NPV propagation and superradiance is presented. We show that,
although both phenomenons involve negative energy densities, there are two
significant differences between them.


title:
The circumstellar environment of T Tau S at high spatial and spectral
  resolution

abstract:
  We have obtained the first high spatial (0.05'') and spectral (R~35000)
resolution 2 micron spectrum of the T Tau S tight binary system using adaptive
optics on the Keck II telescope. We have also obtained the first 3.8 and 4.7
micron images that resolve the three components of the T Tau multiple system,
as well as new 1.6 and 2.2 micron images. Together with its very red
near-infrared colors, the spectrum of T Tau Sb shows that this T Tauri star is
extincted by a roughly constant extinction of Av~15 mag, which is probably the
0.7''x0.5'' circumbinary structure recently observed in absorption in the
ultraviolet. T Tau Sa, which is also observed through this screen and is
actively accreting, further possesses a small edge-on disk that is evidenced by
warm (390 K), narrow overtone CO rovibrational absorption features in our
spectrum. We find that T Tau Sa is most likely an intermediate-mass star
surrounded by a semi-transparent 2-3 AU-radius disk whose asymmetries and short
Keplerian rotation explain the large photometric variability of the source on
relatively short timescales. We also show that molecular hydrogen emission
exclusively arises from the gas that surrounds T Tau S and that its spatial and
kinematic structure, while providing suggestive evidence for a jet-like
structure, is highly complex.


title: Models for the soft X-ray emission of post-outburst classical novae

abstract:
  A hydrostatic and stationary white dwarf envelope model has been developed
for the study of the post-outburst phases of classical novae and their soft
X-ray emission. Several white dwarf masses and chemical compositions typical
for classical novae have been considered. The results show that the luminosity,
maximum effective temperature and envelope masses depend on the white dwarf
mass and on the chemical composition. Envelope masses for which equilibrium
solutions exist are pretty small ~10^{-7}-10^{-6} Msun, thus leading to a short
duration of the soft X-ray emitting phase of classical novae, in agreement with
most of the observations. The models presented provide a useful tool for the
determination of the white dwarf properties from observable parameters in the
X-ray range.


title: Oxygen-rich disk in the V778 Cyg system resolved

abstract:
  Various scenarios have been proposed to explain the presence of silicate
features associated with carbon stars, such as V778 Cyg. We have attempted to
constrain these theories by means of mapping water maser mission from V778 Cyg.
The 22 GHz water maser emission from this star has been mapped using MERLIN
with an astrometric accuracy of 25 mas. The spatially- and
kinematically-resolved maser complex is displaced by about 190 mas from the
position of the C-star as measured 10 years earlier using Tycho. Our
simulations and analysis of available data show that this position difference
is unlikely to be due to proper motion if V778 Cyg is at the assumed distance
of 1.4 kpc. The maser components seem to form a distorted S-shaped structure
extended over 18 mas with a clear velocity gradient. We propose a model which
explains the observed water maser structure as an O-rich warped disk around a
companion of the C-star in V 778 binary system, which is seen almost edge-on.
Analysis of observational data, especially those obtained with MERLIN, suggests
that V778 Cyg (and, by implication, other silicate carbon stars) are binary
systems composed of a C-rich star and a companion which stores circumstellar
O-rich material.


title:
Discovery of multiple ultraluminous X-ray sources in the galaxy KUG
  0214-057

abstract:
  We report the serendipitous discovery of several unresolved X-ray sources
lying in the prominent spiral arms of the galaxy KUG 0214-057 in XMM-Newton
observations. The location of these X-ray sources strongly suggests that at
least three, and possibly four, of these may be physically related to the
galaxy. The luminosity of each of these sources at the distance of KUG 0214-057
is > 5 x 10^39 erg/s (0.3-10 keV), making each a strong candidate ultraluminous
X-ray source (ULX). Using the ULXs as a metric implies that this relatively
low-mass galaxy may be experiencing rather intense starburst activity. The
serendipitous discovery of these ULXs suggests that such objects are not a
negligible component of the overall extragalactic X-ray source population.


title:
Low-Energy Hadron Production Data and Current Status of CERN
  Measurements

abstract:
  Data on low-energy hadron production in collisions of nucleons, pions and
kaons with light nuclei are needed for many astrophysical and accelerator
applications. Modern simulations have reached a level of accuracy that the lack
of detailed understanding of hadron production processes has become one of the
most important limitations to further improvements. After giving some examples
of hadroproduction processes in astrophysics and neutrino experiments we
briefly review existing fixed-target data on light nuclei. Preliminary results
and prospects of current CERN measurements (HARP, NA49) are discussed.


title: The 1st INTEGRAL SPI-ACS Gamma-Ray Burst Catalogue

abstract:
  We present the sample of gamma-ray bursts detected with the anti-coincidence
shield ACS of the spectrometer SPI on-board INTEGRAL for the first 26.5 months
of mission operation (up to Jan 2005). SPI-ACS works as a nearly
omnidirectional gamma-ray burst detector above ~80 keV but lacks spatial and
spectral information. In this catalogue, the properties derived from the 50 ms
light curves (e.g., T90, Cmax, Cint, variability, V/Vmax) are given for each
candidate burst in the sample. A strong excess of very short events with
durations <0.25 s is found. This population is shown to be significantly
different from the short- and long-duration burst sample by means of the
intensity distribution and V/Vmax test and is certainly connected with cosmic
ray hits in the detector. A rate of 0.3 true gamma-ray bursts per day is
observed.


title: Very High Energy Cosmic Rays and Their Interactions

abstract:
  The investigation of high energy cosmic rays and their interactions is a very
active field of research. This article summarizes the progress made during the
last years as reflected by the contributions to the XIII International
Symposium on Very High Energy Cosmic Ray Interactions held in Pylos, Greece.


title: An HST Study of the Supernovae Accompanying GRB 040924 and GRB 041006

abstract:
  We present the results from a {\it Hubble Space Telescope/ACS} study of the
supernovae associated with gamma-ray bursts 040924 ($z=0.86$) and 041006
($z=0.71$). We find evidence that both GRBs were associated with a SN
1998bw-like supernova dimmed by $\sim 1.5$ and $\sim 0.3$ magnitudes,
respectively, making GRB 040924 the faintest GRB-associated SN ever detected.
We study the luminosity dispersion in GRB/XRF-associated SNe and compare to
local Type Ibc supernovae from the literature. We find significant overlap
between the two samples, suggesting that GRB/XRF-associated SNe are not
necessarily more luminous nor produce more $^{56}$Ni than local SNe. Based on
the current (limited) datasets, we find that the two samples may share a
similar $^{56}$Ni production mechanism.


title:
X-Ray Timing, Spectroscopy and Photometry of the Anomalous X-Ray Pulsar
  Candidate CXOU J010043.1-721134

abstract:
  We present new X-ray timing and spectral results on the 8.0-second X-ray
pulsar CXOU J010043.1-721134 from a series of observations using the Chandra
X-ray Observatory. We find a spin period in 2004 January of 8.020392pm0.000009
seconds. Comparison of this to 2001 Chandra observations implies a period
derivative dot{P} = (1.88 pm 0.08) times 10^{-11} s s^{-1}, leading to an
inferred dipole surface magnetic field of 3.9 times 10^{14} G. The spectrum is
well fit to an absorbed blackbody of temperature kT = 0.38pm0.02 keV with a
power law tail of photon index Gamma = 2.0pm0.6. We find that the source has an
unabsorbed X-ray flux (0.5-10 keV) of 4(+2-1) times 10^{-13} erg cm^{-2} s^{-1}
and a corresponding X-ray luminosity of ~2 times 10^{35} erg s^{-1} for a
distance of 60 kpc. These properties support classification of CXOU
J010043.1-721134 as the seventh confirmed anomalous X-ray pulsar,the eleventh
confirmed magnetar, and the first magnetar to be identified in the Small
Magellanic Cloud.


title: Search for Cosmic-Ray Antideuterons

abstract:
  We performed a search for cosmic-ray antideuterons using data collected
during four BESS balloon flights from 1997 to 2000. No candidate was found. We
derived, for the first time, an upper limit of 1.9E-4 (m^2 s sr
GeV/nucleon)^(-1) for the differential flux of cosmic-ray antideuterons, at the
95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the
atmosphere.


title: XMM-Newton EPIC background modeling for extended sources

abstract:
  We use XMM-Newton blank-sky and closed-cover background data to explore the
background subtraction methods for large extended sources filling the EPIC
field of view, such as nearby galaxy clusters, for which local background
estimation is difficult. We find that to keep the 0.8-7.0 keV band background
modeling uncertainty tolerable, one has to use a much more restrictive filter
than that commonly applied. In particular, because flares have highly variable
spectra, not all of them are identified by filtering the E>10 keV light curve.
We tried using the outer part of the EPIC FOV for monitoring the background in
a softer band (1-5 keV). We find that one needs to discard the time periods
when either the hard-band or the soft-band rate exceeds the nominal value by
more than 20% in order to limit the 90% CL background uncertainty to between 5%
at E=4-7 keV and 20% at E=0.8-1 keV, for both MOS and PN. This compares to a
10-30% respective PN uncertainty when only the hard-band light curve is used
for filtering, and to a 15-45% PN uncertainty when applying the commonly used
2-3 sigma filtering method. We illustrate our method on a nearby cluster A1795.
The above background uncertainties convert into the systematic temperature
uncertainties between 1% at r=3-4 arcmin and 20--25% (~1 keV for A1795) at
r=10-15 arcmin. For comparison, the commonly applied 2-3 sigma clipping of the
hard-band light curve misses a significant amount of flares, rendering the
temperatures beyond r=10 arcmin unconstrained. Thus, the background
uncertainties do not prohibit the EPIC temperature profile analysis of
low-brightness regions, like outer regions of galaxy clusters, provided a
conservative flare filtering such as the double filtering method with 20%
limits is used.


title:
The Growth, Polarization, and Motion of the Radio Afterglow from the
  Giant Flare from SGR 1806-20

abstract:
  The extraordinary giant flare (GF) of 2004 December 27 from the soft gamma
repeater (SGR) 1806-20 was followed by a bright radio afterglow. We present an
analysis of VLA observations of this radio afterglow from SGR 1806-20,
consisting of previously reported 8.5 GHz data covering days 7 to 20 after the
GF, plus new observations at 8.5 and 22 GHz from day 24 to 81. We detect motion
in the flux centroid of the afterglow, at an average velocity of 0.26 +/- 0.03
c (assuming a distance of 15 kpc) at a position angle of -45 degrees. This
motion, in combination with the growth and polarization measurements, suggests
an asymmetric outflow, mainly from one side of the magnetar. We find a
deceleration in the expansion, from ~9 mas/day to <5 mas/day. The time of
deceleration is roughly coincident with the rebrightening in the radio light
curve, as expected to result when the ejecta from the GF sweeps up enough of
the external medium, and transitions from a coasting phase to the Sedov-Taylor
regime. The radio afterglow is elongated and maintains a 2:1 axis ratio with an
average position angle of -40 degrees (north through east), oriented
perpendicular to the average intrinsic linear polarization angle.


title: Discrete Quantum Spectrum of Observable Correlations from Inflation

abstract:
  The decoherence of quantum fluctuations into classical perturbations during
inflation is discussed. A simple quantum mechanical argument, using a spatial
particle wavefunction rather than a field description, shows that observable
correlations from inflation must have a discrete spectrum, since they originate
and freeze into the metric within a compact region. The number of discrete
modes is estimated using a holographic bound on the number of degrees of
freedom. The discreteness may be detectable in some models; for example, if
there is a fundamental universal frequency spectrum, the inflationary
gravitational wave background may be resolvable into discrete emission lines.


title: A brief introduction to cosmic topology

abstract:
  Whether we live in a spatially finite universe, and what its shape and size
may be, are among the fundamental long-standing questions in cosmology. These
questions of topological nature have become particularly topical, given the
wealth of increasingly accurate astro-cosmological observations, especially the
recent observations of the cosmic microwave background radiation. An overview
of the basic context of cosmic topology, the detectability constraints from
recent observations, as well as the main methods for its detection and some
recent results are briefly presented.


title:
Effects of collisions and interactions on star formation in galaxy pairs
  in the field

abstract:
  By using cosmological simulations, we studied the effects of galaxy
interactionson the star formation activity in the local Universe. We selected
galaxy pairs from the 3D galaxy distribution according to a proximity
criterion. The 2D galaxy catalog was constructed by projecting the 3D total
galaxy distribution and then selecting projected galaxy pairs. The analysis of
the 3D galaxy pair catalog showed that an enhancement of the star formation
activity can be statistically correlated with proximity.
  The projected galaxy pairs exhibited a similar trend with projected distances
and relative radial velocities. However, the star formation enhancement signal
is diminished with respect to that of the 3D galaxy pair catalog owing to
projection effects and spurious galaxy pairs. Overall, we found that
hierarchical scenarios reproduced the observational dependence of star
formation activity in pairs on orbital parameters and environment. We also
found that geometrical effects due to projection modify the trends more
severely than those introduced by spurious pairs.


title: Can Minor Planets be Used to Assess Gravity in the Outer Solar System?

abstract:
  The twin Pioneer spacecraft have been tracked for over thirty years as they
headed out of the solar system. After passing 20 AU from the Sun, both
exhibited a systematic error in their trajectories that can be interpreted as a
constant acceleration towards the Sun. This Pioneer Effect is most likely
explained by spacecraft systematics, but there have been no convincing
arguments that that is the case. The alternative is that the Pioneer Effect
represents a real phenomenon and perhaps new physics. What is lacking is a
means of measuring the effect, its variation, its potential anisotropies, and
its region of influence. We show that minor planets provide an observational
vehicle for investigating the gravitational field in the outer solar system,
and that a sustained observation campaign against properly chosen minor planets
could confirm or refute the existence of the Pioneer Effect. Additionally, even
if the Pioneer Effect does not represent a new physical phenomenon, minor
planets can be used to probe the gravitational field in the outer Solar System
and since there are very few intermediate range tests of gravity at the
multiple AU distance scale, this is a worthwhile endeavor in its own right.


title: From Neutron Star Binaries to Gamma-ray bursts

abstract:
  I summarize recent results about how a neutron star binary coalescence can
produce short gamma-ray bursts (GRBs). Two possibilities are discussed: the
annihilation of neutrino anti-neutrino pairs above the merged remnant and the
exponential amplification of magnetic fields in the central object up to values
close to equipartition. We find that the neutrino annihilation drives bipolar,
relativistic outflows with Lorentz-factors large enough to circumvent the GRB
'compactness problem'. The total energy within these outflows is moderate by
GRB-standards ($\sim 10^{48}-10^{49}$ ergs), but the interaction with the
baryonic material blown-off by the neutrinos collimates the outflows into
opening angles of typically 0.1 sterad, yielding isotropic energies close to
$10^{51}$ ergs. We further want to stress the plausibility of the central
object resisting the immediate collapse to a black hole. In this case the
central object will --similar to a proto-neutron star-- be subject to neutrino
driven convection that --together with the rapid, differential rotation-- will
lead to a drastic amplification of pre-existing magnetic fields. Within
fractions of a second, field strengths comparable to equipartition field
strength ($> 10^{17}$ G) will be reached. These will produce large torques that
will spin-down the object within about 0.2 s, and would thus naturally explain
the duration of short GRBs.


title: The Plerionic Supernova Remnant G21.5-0.9: In and Out

abstract:
  The absence of a supernova remnant (SNR) shell surrounding the Crab and other
plerions (pulsar wind nebulae) has been a mystery for 3 decades. G21.5-0.9 is a
particularly intriguing plerionic SNR in which the central powering engine is
not yet detected. Early Chandra observations revealed a faint extended X-ray
halo which was suggested to be associated with the SNR shell; however its
spectrum was nonthermal, unlike what is expected from an SNR shell. On the
other hand, a plerionic origin to the halo is problematic since the X-ray
plerion would be larger than the radio plerion. We present here our analysis of
an integrated 245 ksec of archival Chandra data acquired with the
High-Resolution Camera (HRC) and 520 ksec acquired with the Advanced CCD
Imaging Spectrometer (ACIS). This study provides the deepest and highest
resolution images obtained to date. The resulting images reveal for the first
time 1) a limb-brightened morphology in the eastern section of the halo, and 2)
a rich structure in the inner (40"-radius) bright plerion including wisps and a
double-lobed morphology with an axis of symmetry running in the
northwest-southeast direction. Our spatially resolved spectroscopic study of
the ACIS-I data indicates that the photon index steepens with increasing
distance from the central point source out to a radius of 40" then becomes
constant at ~2.4 in the X-ray halo (for a column density N_H=2.2E22/cm^2). No
line emission was found from the eastern limb; however marginal evidence for
line emission in the halo's northern knots was found. This study illustrates
the need for deep Chandra observations to reveal the missing SNR material in
Crab-like plerions.


title:
Membership of the Orion Nebula Population from the Chandra Orion
  Ultradeep Project

abstract:
  The Chandra Orion Ultradeep project (COUP) observation described in a
companion paper by Getman et al. provides an exceptionally deep X-ray survey of
the Orion Nebula Cluster and associated embedded young stellar objects.
Membership of the region is important for studies of the stellar IMF, cluster
dynamics, and star formation. The COUP study detected 1616 X-ray sources. In
this study we confirm cloud membership for 1315 stars, identify 16 probable
foreground field stars having optical counterparts with discrepant proper
motions, and classify the remaining 285 X-ray sources, of which 51 are lightly
and 234 heavily obscured. The 51 lightly obscured sources without known
counterparts fall into three groups. (i) Sixteen are likely new members of the
Orion Nebula Cluster. (ii) Two with unusually soft and non-flaring X-ray
emission appear to be associated with nebular shocks, and may be new examples
of X-rays produced at the bow shocks of Herbig-Haro outflows. (iii) The
remaining thirty three are very weak uncertain sources, possibly spurious. Out
of 234 heavily absorbed sources without optical or near-infrared counterparts
75 COUP sources are likely new embedded cloud members (with membership for 42
confirmed by powerful X-ray flares), and the remaining 159 are likely
extragalactic AGN seen through the molecular cloud, as argued by a careful
simulation of the extragalactic background population. Finally, a few new
binary companions to Orion stars may have been found, but most cases of
proximate COUP sources can be attributed to chance superpositions in this
crowded field.


title: Gamma-Ray Burst Sequences in Hardness Ratio-Peak Energy Plane

abstract:
  The narrowness of the distribution of the peak energy of $\nu F_{\nu}$
spectrum of gamma-ray bursts (GRBs) and the unification of GRB population are
great puzzles yet to be solved. We investigate the two puzzles based on the
global spectral behaviors of different GRB population in the $HR-E_{\rm{p}}$
plane (HR the spectral hardness ratio) with BATSE and HETE-2 observations. It
is found that long GRBs and XRFs observed by HETE-2 seem to follow the same
sequence in the $HR-E_{\rm{p}}$ plane, with the XRFs at the low end of this
sequence. The long and short GRBs observed by BATSE follow significantly
different sequences in the $HR-E_{\rm p}$ plane, with most of the short GRBs
having a larger hardness ratio than the long GRBs at a given $E_{\rm{p}}$.
These results indicate that the global spectral behaviors of the long GRB
sample and the XRF sample are similar, while that of short GRBs is different.
The short GRBs seem to be a unique subclass of GRBs, and they are not the
higher energy extension of the long GRBs (abridged).


title:
Testing the Universal Structured Jet Models of Gamma-Ray Bursts by BATSE
  Observations

abstract:
  Assuming that the observed gamma-ray burst (GRB) rate as a function of
redshift is proportional to a corrected star formation rate, we derive the
empirical distribution of the viewing angles of long BATSE GRBs, $P^{\rm
em}(\theta)$, and the distribution of these bursts in the plane of $\theta$
against redshift, $P^{\rm em}(\theta, z)$, by using a tight correlation between
$E_{\gamma}$) and $E_{\rm p}^{'}$). Our results show that $P^{\rm em}(\theta)$
is well fitted by a log-normal distribution centering at $\log \theta/{\rm
rad}=-0.76$ with a width of $\sigma_{\log \theta}=0.57$. We test different
universal structured jet models by comparing model predictions with our
empirical results. To make the comparisons reasonable, an "effective"
threshold, which corresponds to the sample selection criteria of the long GRB
sample, is used. We find that the predictions of a two-Gaussian jet model are
roughly consistent with our empirical results. A brief discussion shows that
cosmological effect on the $E_{\gamma}-E_{\rm p}^{'}$ relation does not
significantly affect our results, but sample selection effects on this
relationship might significantly influence our results.


title:
Number Density of Bright Lyman-Break Galaxies at z~6 in the Subaru Deep
  Field

abstract:
  We report on the bright Lyman-break galaxies (LBGs) selected in a 767
arcmin^2 area of the Subaru Deep Field. The selection is made in the i-zR vs
zB-zR plane, where zB and zR are new bandpasses with a central wavelength of
8842A and 9841A, respectively. This set of bandpasses enables us to separate
well z~6 LBGs from foreground galaxies and Galactic cool stars. We detect 12
LBG candidates down to zR=25.4, and calculate the normalization of the
rest-frame far-ultraviolet (FUV: 1400A) luminosity function at MFUV = -21.6 to
be \phi(-21.6) = (2.6+/-0.7) x 10^{-5} mag^{-1} Mpc^{-3}. This must be the most
reliable measurement ever obtained of the number density of bright z~6 LBGs,
because it is more robust against both contamination and cosmic variance than
previous values. The FUV luminosity density contributed from LBGs brighter than
MFUV = -21.3 is (2.8+/-0.8) x 10^{24} ergs/s/Hz/Mpc^3, which is equivalent to a
star formation rate density of (3.5+/-1.0) x 10^{-4} Msun/yr/Mpc^3. Combining
our measurement with those at z<6 in the literature, we find that the FUV
luminosity density of bright galaxies increases by an order of magnitude from
z~6 to z~3 and then drops by 10^3 from z~3 to the present epoch, while the
evolution of the total luminosity density is much milder. The evolutionary
behavior of bright LBGs resembles that of luminous dusty star-forming galaxies
and bright QSOs. The redshift of z~3 appears to be a remarkable era in the
cosmic history when massive galaxies were being intensively formed.


title: The Correlation of Metallicity Gradient with Galaxy Mass

abstract:
  A number of previous studies have searched for a correlation between radial
metallicity gradients and early-type galaxy mass -- no convincing trends have
been found. Here we re-examine this issue with several key enhancements: using
total metallicity from studies that have broken the age-metallicity degeneracy,
excluding galaxies with young stellar ages (i.e. tho se that have experienced a
recent central starburst) and using the K-band to derive galaxy luminosities.
We find that Coma cluster galaxies have metallicity gradients which correlate
with galaxy mass. Furthermore, gradients have values similar to those of
monolithic collapse models. The combination of dissipative formation and energy
injection from supernova provides a mechanism for the trends with galaxy mass,
however other explanations are possible. Additional high quality observational
data is needed to further constrain the gas physics involved in galaxy
formation.


title:
Third-order perturbative solutions in the Lagrangian perturbation theory
  with pressure II: Effect of the transverse modes

abstract:
  Lagrangian perturbation theory for cosmological fluid describes structure
formation in the quasi-nonlinear stage well. In a previous paper, we presented
a third-order perturbative equation for Lagrangian perturbation with pressure.
There we considered only the longitudinal modes for the first-order
perturbation. In this paper, we generalize the perturbation, i.e., we consider
both the longitudinal and the transverse modes for the first-order
perturbation. Then we derive third-order perturbative equations and solutions.


title: The rates of Type Ia Supernovae. I. Analytical Formulations

abstract:
  This paper provides a handy tool to compute the impact of Type Ia Supernova
(SNIa) on the evolution of stellar systems. An effective formalism is presented
to couple the SNIa rate to the star formation history, which rests upon the
definition of two key properties of the progenitor's model: the realization
probability of the SNIa event from a single stellar generation and the
distribution function of the delay times. It is shown that the current SNIa
rate in late type galaxies implies that the realization probability is on the
order of 0.001. Analytical formulations for the distribution function of the
delay times for Single (SD) and Double Degenerate (DD) progenitors are derived,
based on stellar evolution arguments. These formulations, which agree well with
the results of Monte Carlo simulations for the evolution of close binaries,
have a built in parametrization of the key properties of the alternative
candidates. The various models for the progenitors have different impact on the
large scales. In particular, the paper examines the systematic trend of the
SNIa rate per unit mass with the color of the parent galaxy, and shows that the
recent observations favor the DD model. The SD scenario can reproduce the data
only if the distribution of the primordial mass ratios is flat, and the
accretion efficiency onto the WD is close to 100%. The timescale for the Fe
release from SNIa to the interstellar medium ranges between 0.3 and 3 Gyr for a
wide variety of hypothesis on the SNIa progenitors. (ABRIDGED)


title: The Spectral Energy Distribution of CO lines in M82

abstract:
  We present an analysis of the excitation conditions of the molecular gas in
the streamers and the outflow of M82 based on observations obtained at the IRAM
30m telescope. Our analysis of J=1-0 and J=2-1 transitions of CO and 13CO and
the CO(3-2) line in 13 regions outside the central starburst disk shows that
the gas density within the streamer/outflow system is about an orderof
magnitude lower (n(H2) ~ 10^3 cm^-3) than in the central molecular disk. We
have used an LVG model and data from the literature to constrain the flux
density in each CO transition (the `CO line SED') arising from the
streamer/outflow system and the central starburst disk itself. Globally, we
find that the CO flux density up to the J=3-2 line is dominated by the diffuse
outer regions while lines above the J=5-4 transition are almost exclusively
emitted by the central starburst disk. We compare the CO line SED of M82 to CO
observations of galaxies at high redshift and suggest that small high-J/low-J
CO flux density ratios (observed in some of these sources) are not necessarily
caused by a different excitation of the central molecular gas concentration,
but may result from an additional, more extended and diffuse gas reservoir
around these systems, reminiscent of the situation in M82.


title:
On the relationship between auroral and nebular oxygen line intensities
  in spectra of HII regions

abstract:
  We investigate relationships between observed auroral and nebular oxygen line
fluxes in spectra of HII regions. We find a relation that is
metallicity-dependent at low metallicities, but becomes independent of
metallicity (within the uncertainties of the available data) above 12+logO/H ~
8.25, i.e. there is one-to-one correspondance (the ff - relation) between
auroral and nebular oxygen line fluxes in spectra of high-metallicity HII
regions. The ff - relation allows one to estimate the flux in the auroral line
from strong oxygen line measurements. This solves the problem of the electron
temperature (and, consequently, abundance) determination in high-metallicity
HII regions. The ff - relation confirms the basic idea of the empirical method,
proposed by Pagel et al. (1979) a qurter of a century ago, that the oxygen
abundance in HII region can be estimated from the strong oxygen lines
measurements only.


title:
An empirical formula for the mass-loss rates of dust-enshrouded red
  supergiants and oxygen-rich Asymptotic Giant Branch stars

abstract:
  We present an empirical determination of the mass-loss rate as a function of
stellar luminosity and effective temperature, for oxygen-rich dust-enshrouded
Asymptotic Giant Branch stars and red supergiants. To this aim we obtained
optical spectra of a sample of dust-enshrouded red giants in the Large
Magellanic Cloud, which we complemented with spectroscopic and infrared
photometric data from the literature. Two of these turned out to be hot
emission-line stars, of which one is a definite B[e] star. The mass-loss rates
were measured through modelling of the spectral energy distributions. We thus
obtain the mass-loss rate formula log Mdot = -5.65 + 1.05 log(L / 10,000 Lsun)
-6.3 log(Teff / 3500 K), valid for dust-enshrouded red supergiants and
oxygen-rich AGB stars. Despite the low metallicity of the LMC, both AGB stars
and red supergiants are found at late spectral types. A comparison with
galactic AGB stars and red supergiants shows excellent agreement between the
mass-loss rate as predicted by our formula and that derived from the 60 micron
flux density for dust-enshrouded objects, but not for optically bright objects.
We discuss the possible implications of this for the mass-loss mechanism.


title: A new population of very high energy gamma-ray sources in the Milky Way

abstract:
  Very high energy gamma-rays probe the long-standing mystery of the origin of
cosmic rays. Produced in the interactions of accelerated particles in
astrophysical objects, they can be used to image cosmic particle accelerators.
A first sensitive survey of the inner part of the Milky Way with the High
Energy Stereoscopic System (H.E.S.S.) reveals a population of eight previously
unknown firmly detected sources of very high energy gamma-rays. At least two
have no known radio or X-ray counterpart and may be representative of a new
class of `dark' nucleonic cosmic ray sources.


title: Magneto-rotational overstability in accretion disks

abstract:
  We present analytical and numerical studies of magnetorotational
instabilities occuring in magnetized accretion disks. In these studies we make
use of the linearised compressible MHD equations. These calculations are
performed for general radially stratified disks in the cylindrical limit. In
particular, we investigate the influence of nonvanishing toroidal magnetic
field component on the growth rate and oscillation frequency of
magnetorotational instabilities in Keplerian disks. We find the persistence of
these instabilities in accretion disks close to equipartition. Our calculations
show that these eigenmodes become overstable (complex eigenvalue), due to the
presence of a toroidal magnetic field component, while their growth rate
reduces slightly. Furthermore, we demonstrate the presence of
magneto-rotational overstabilities in weakly magnetized sub-Keplerian rotating
disks. We show that the growth rate scales with the rotation frequency of the
disk. These eigenmodes also have a nonzero oscillation frequency, due to the
presence of the dominant toroidal magnetic field component. The overstable
character of the MRI increases as the rotation frequency of the disk decreases.


title: The accreting white dwarfs in BW Scl, BC UMa and SW UMa

abstract:
  We have observed the short-period dwarf novae BW Scl, BC UMa and SW UMa using
the Hubble Space Telescope/Space Telescope Imaging Spectrograph. In all three
systems, the white dwarf is the dominant source of far-ultraviolet flux, even
though in BC UMa and SW UMa an additional continuum component contributes ~10%
and ~20% of the 1400A flux, respectively. Fitting the data with detailed white
dwarf model spectra, we determine the effective temperatures to be 14800+-900K
(BW Scl), 15200+-1000K (BC UMa), and 13900+-900K (SW UMa). The additional
continuum component in BC UMa and SW UMa is equally well described by either a
blackbody or a power law, which could be associated with emission from the hot
spot or from an optically thin accretion disk (or an optically thin layer on
top of a colder optically thick disk), respectively. Modelling the narrow metal
lines detected in the STIS spectra results in sub-solar abundances of carbon,
oxygen and silicon for all three systems, and also suggests substantial
supra-solar abundances of aluminium. The narrow absorption line profiles imply
low white dwarf rotation rates, v sin(i)<=300km/s for the three white dwarfs.
SW UMa is the only system that shows significant short-term variability in the
far-ultraviolet range, which is primarily associated with the observed emission
lines.


title: Breaking scale invariance from a singular inflaton potential

abstract:
  In this paper we break the scale invariance of the primordial power spectrum
of curvature perturbations of inflation. Introducing a singular behaviour due
to spontaneous symmetry breaking in the inflaton potential, we obtain fully
analytic expressions of scale dependent oscillation and a modulation in power
on small scale in the primordial spectrum. And we give the associated cosmic
microwave background and matter power spectra which we can observe now and
discuss the signature of the scale dependence. We also address the possibility
of whether some inflationary model with featured potential might mimic the
predictions of the scale invariant power spectrum. We present some examples
which illustrate such degeneracies.


title: Comments on the proposal of Dark Energy Stars by Chapline

abstract:
  We point out that the contentions of Chapline (astro-ph/0503200)[1] that (i)
General Relativity (GR) is in conflict with Quantum Mechanics (QM) and (ii) GR
fails even on macroscopic length scales are incorrect and based on (i)
misunderstanding of GR and (ii) completely misconceived ``thought
experiments''. Even without introduction of any QM, GR actually does not allow
formation of any Event Horizon and is competent to figure out the actual nature
of the supposed Black Hole candidates. The resultant picture is not in conflict
with QM at all.


title: dEs and the dI Fundamental Plane

abstract:
  Despite much work, the connection between dwarf elliptical galaxies (dEs) and
dwarf irregulars (dIs) remains unclear. Recently, we found that the surface
brightness profiles (SBPs) of dIs in the near-infrared can be well fitted with
a hyperbolic secant (sech) function. From sech fits, a tight relationship was
derived between the absolute magnitude, central surface brightness, and 21cm
line widths, which amounts to a fundamental plane for dIs. Here we examine how
closely dEs fit into the dI fundamental plane using published data for 22 dEs
in the Virgo cluster and the Local Group. Over a 9 mag interval in absolute
magnitude the dEs fall in the plane defined by the dIs. The outstanding overlap
suggests more than a casual relationship between the two classes.


title: Convective magneto-rotational instabilities in accretion disks

abstract:
  We present a study of instabilities occuring in thick magnetized accretion
disks. We calculate the growth rates of these instabilities and characterise
precisely the contribution of the magneto-rotational and the convective
mechanism. All our calculations are performed in radially stratified disks in
the cylindrical limit. The numerical calculations are performed using the
appropriate local dispersion equation solver discussed in Blokland et al.
(2005). A comparison with recent results by Narayan et al. (2002) shows
excellent agreement with their approximate growth rates only if the disks are
weakly magnetized. However, for disks close to equipartition, the dispersion
equation from Narayan et al. (2002) loses its validity. Our calculations allow
for a quantitative determination of the increase of the growth rate due to the
magneto-rotational mechanism. We find that the increase of the growth rate for
long wavelength convective modes caused by this mechanism is almost neglible.
On the other hand, the growth rate of short wavelength instabilities can be
significantly increased by this mechanism, reaching values up to 60%.


title: Rotation and anisotropy of galaxies revisited

abstract:
  The use of the tensor virial theorem (TVT) as a diagnostic of anisotropic
velocity distributions in galaxies is revisited. The TVT provides a rigorous
global link between velocity anisotropy, rotation and shape, but the quantities
appearing in it are not easily estimated observationally. Traditionally use has
been made of a centrally averaged velocity dispersion and the peak rotation
velocity. Although this procedure cannot be rigorously justified, tests on
model galaxies show that it works surprisingly well. With the advent of
integral-field spectroscopy it is now possible to establish a rigorous
connection between the TVT and observations. The TVT is reformulated in terms
of sky-averages, and the new formulation is tested on model galaxies.


title:
Klein-Nishina Effects in the Spectra of Non-Thermal Sources Immersed in
  External Radiation Fields

abstract:
  We study Klein-Nishina (KN) effects in the spectrum produced by a steady
state, non-thermal source where rapidly accelerated electrons cool by emitting
synchrotron radiation and Compton upscattering ambient photons produced outside
the source. We focus on the case where the radiation density inside the source
exceeds that of the magnetic field. We show that the KN reduction in the
electron Compton cooling rate causes the steady-state electron spectrum to
harden at energies above \gamma_{KN}, where \gamma_{KN}= 1/4\epsilon_0 and
\epsilon_0=h\nu_0/m_ec^2 is the characteristic ambient photon energy. The
source synchrotron spectrum thus shows a high-energy ``bump'' or excess even
though the electron acceleration spectrum has no such excess. In contrast, the
low-energy Compton gamma-ray spectrum shows little distortion because the
electron hardening compensates for the KN decline in the scattering rate. For
sufficiently high electron energies, however, Compton cooling becomes so
inefficient that synchrotron cooling dominates -- an effect omitted in most
previous studies. The hardening of the electron distribution thus stops,
leading to a rapid decline in Compton gamma-ray emission, i.e., a strong
spectral break whose location does not depend on the maximum electron energy.
This break can limit the importance of Compton gamma-ray pair production on
ambient photons and implies that a source's synchrotron luminosity may exceed
its Compton luminosity even though the source magnetic field energy density is
smaller than the ambient radiation energy density. We discuss the importance of
these KN effects in blazars, micro-quasars, and pulsar binaries.


title: Chemical Abundances in SFG and DLA

abstract:
  We investigate the chemical abundances of local star-forming galaxies which
cause Damped Lyman Alpha lines. A metallicity versus redshift diagram is
constructed, on which the chemical abundances of low-redshift star-forming
galaxy populations are compared with those of high-redshift Damped Lyman Alpha
systems. We disucss two types of experiments on individual star-forming
galaxies. In the first, the Damped Lyman Alpha line is created against an
internal ultraviolet light source generated by a star-forming cluster or a
supernova explosion. In the second, the Damped Lyman Alpha line is seen against
a background Quasar. The metallicities measured from ionized gas in the
star-forming regions, and neutral gas in the Damped Lyman Alpha systems, are
compared with one another on a case-by-case basis. We highlight the occurrence
of the star-forming galaxy/Quasar pair SBS 1543+593/HS 1543+5921, where the
emission- and absorption-line derived abundances give the same result. We argue
that we therefore can in principle, interpret Damped Lyman Alpha system
metallicities as an extension of star-forming galaxy metallicities to higher
redshifts, supporting that gas-rich galaxies had lower chemical abundances when
the were younger.