title:
Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant
  Heliocentric Orbits

abstract:
  Recently, Brown et al. (2004) reported the exciting discovery of an ~800 km
radius object, (90377) Sedna, on a distant, eccentric orbit centered at ~490 AU
from the Sun. Here we undertake a first look exploring the feasibility of
accreting this object and its possible cohorts between 75 AU (Sedna's
perihelion distance) and 500 AU (Sedna's semi-major axis distance) from the
Sun. We find such accretion possible in a small fraction of the age of the
solar system, if such objects were initially on nearly circular orbits in this
region, and if the solar nebula extended outward to distances far beyond the
Kuiper Belt. If Sedna did form in situ, it is likely to be accompanied by a
cohort of other large bodies in this region of the solar system.


title:
Gravitational Lensing by Black Holes: a comprehensive treatment and the
  case of the star S2

abstract:
  Light rays passing very close to a black hole may experience very strong
deviations. Two geometries were separately considered in the recent literature:
a source behind the black hole (standard gravitational lensing); a source in
front of the black hole (retro-lensing). In this paper we start from the Strong
Field Limit approach to recover both situations under the same formalism,
describing not only the two geometries just mentioned but also any intermediate
possible configurations of the system source-lens-observer, without any
small-angle limitations. This is done for any spherically symmetric black holes
and for the equatorial plane of Kerr black holes. In the light of this
formalism we revisit the previous literature on retro-lensing, sensibly
improving the observational estimates. In particular, for the case of the star
S2, we give sharp predictions for the magnitude of the relativistic images and
the time of their highest brightness, which should occur at the beginning of
year 2018. The observation of such images would open fascinating perspectives
on the measure of the physical parameters of the central black hole, including
mass, spin and distance.


title:
The influence of redshift information on galaxy-galaxy lensing
  measurements

abstract:
  We investigate how galaxy-galaxy lensing measurements depend on the knowledge
of redshifts for lens and source galaxies. Galaxy-galaxy lensing allows one to
study dark matter halos of galaxies statistically using weak gravitational
lensing. Redshift information is required to reliably distinguish foreground
lens galaxies from background source galaxies and to convert the measured shear
into constraints on the lens model. Without spectroscopy or multi-colour
information, redshifts can be drawn from independently estimated probability
distributions. The COMBO-17 survey provides redshifts for both lens and source
galaxies. It thus offers the unique possibility to do this investigation with
observational data. We find that it is of great importance to know the
redshifts of individual lens galaxies in order to constrain the properties of
their dark matter halos. Whether the redshifts are derived from $UBVRI$ or the
larger number of filters available in COMBO-17 is not very important. In
contrast, knowledge of individual source redshifts improves the measurements
only very little over the use of statistical source redshift distributions as
long as the source redshift distribution is known accurately.


title:
The null result of a search for pulsational variations of the surface
  magnetic field in the roAp star gamma Equulei

abstract:
  We describe an analysis of the time-resolved measurements of the surface
magnetic field in the roAp star gamma Equ. We have obtained a high-resolution
and high S/N spectroscopic time-series, and the magnetic field was determined
using Zeeman resolved profiles of the Fe II 6149.25 A and Fe I 6173.34 A lines.
Contrary to recent reports we do not find any evidence of magnetic variability
with pulsation phase, and derive an upper limit of 5-10 G for pulsational
modulation of the surface magnetic field in gamma Equ.


title: Cosmic Ray Astrophysics with AMS-02

abstract:
  The Alpha Magnetic Spectrometer (AMS) is a cosmic ray (CR) experiment that
will operate on the International Space Station for three years, measuring the
particle spectra in the rigidity range from 0.2 GV to 2 TV. The AMS-02 detector
will provide measurements with unprecedented statistics of the hadronic and
leptonic cosmic rays, allowing for a better study of the Earth magnetosphere
through the secondaries produced by CR interactions in the atmosphere; of the
solar system environment through the measurement of the solar modulation over a
long period; of the solar system neighborhood through the measurement of the
ratio between unstable isotopes and stable elements; of the interstellar medium
of our Galaxy through the ratio between secondary and primary isotopes and the
measurement of proton and helium spectra.


title: Cosmic Rays and the Monogem Supernova Remnant

abstract:
  Recent findings indicate that the Monogem Ring supernova remnant (SNR) and
the associated pulsar B0656+14 may be the 'Single Source' responsible for the
knee in the cosmic ray (CR) energy spectrum at ~3 PeV. We estimate the
contribution of this pulsar to CR in the PeV region. We conclude that although
the pulsar can contribute to the formation of the knee, it cannot be the
domimant source and a SNR is still needed. We also examine the possibility of
the pulsar giving the peak of the extensive air shower (EAS) intensity observed
from the region inside the Monogem Ring. If the experimental EAS results
concerning a narrow source are confirmed, they can be important, since they
give evidence: (i) for the acceleration of protons and heavier nuclei by the
pulsar; (ii) for the existence of the confinement mechanism in SNR; (iii) that
CR produced by the Monogem Ring SNR and associated pulsar B0656+14 were
released recently giving rise to the formation of the knee and the observed
narrow peak in the EAS intensity; (iv) for the Monogem Ring and the associated
pulsar B0656+14 being identified as the Single Source proposed in our Single
Source Model of the knee. A number of predictions of the examined scenario are
made.


title:
Elucidating the Correlation of the Quasar \ion{Fe}{2}/\ion{Mg}{2} Ratio
  with Redshift

abstract:
  Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from
quasars has a major cosmological motivation. Both Fe and Mg are produced by
short-lived massive stars. In addition, Fe is produced by accreting white dwarf
supernovae somewhat after star formation begins. Therefore, we expect that the
Fe/Mg ratio will gradually decrease with redshift. We have used data from the
Sloan Digital Sky Survey to explore the dependence of the
\ion{Fe}{2}(UV)/\ion{Mg}{2} ratio on redshift and on luminosity in the redshift
range of $0.75< z< 2.20$, and we have used predictions from our 830-level model
for the \ion{Fe}{2} atom in photoionization calculations to interpret our
findings.
  We have split the quasars into several groups based upon the value of their
\ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios, and then checked to see how the
fraction of quasars in each group varies with the increase of redshift. We next
examined the luminosity dependence of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio,
and we found that beyond a threshold of \ion{Fe}{2}(UV)/\ion{Mg}{2} =~ 5, and
$M_{2500} < -25\rm mag$, the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio increases with
luminosity, as predicted by our model.
  We interpret our observed variation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio
with redshift as a result of the correlation of redshift with luminosity in a
magnitude limited quasar sample.


title: The glow of primordial remnants

abstract:
  We determine the expected surface brightness and photometric signature of a
white dwarf remnant population, issued from primordial low-mass stars formed at
high redshifts, in today galactic halos. We examine the radial dependence of
such a contribution as well as its redshift dependence. Such a halo diffuse
radiation is below the detection limit of present large field ground-based
surveys, but should be observable with the HST and with the future JWST
project. Since the surface brightness does not depend on the distance, the
integration of several galactic dark halos along the line of sight will raise
appreciably the chances of detection. Both the detection or the non-detection
of such a remnant diffuse radiation within relevant detection limits offer
valuable information on the minimum mass for star formation in the early
universe and on the evolution of the stellar initial mass function.


title:
On the source of the late-time infrared luminosity of SN 1998S and other
  type II supernovae

abstract:
  We present late-time near-infrared (NIR) and optical observations of the type
IIn SN 1998S. The NIR photometry spans 333-1242 days after explosion, while the
NIR and optical spectra cover 333-1191 days and 305-1093 days respectively. The
NIR photometry extends to the M'-band (4.7 mu), making SN 1998S only the second
ever supernova for which such a long IR wavelength has been detected. The shape
and evolution of the H alpha and HeI 1.083 mu line profiles indicate a powerful
interaction with a progenitor wind, as well as providing evidence of dust
condensation within the ejecta. The latest optical spectrum suggests that the
wind had been flowing for at least 430 years. The intensity and rise of the HK
continuum towards longer wavelengths together with the relatively bright L' and
M' magnitudes shows that the NIR emission was due to hot dust newly-formed in
supernovae may provide the ejecta and/or pre-existing dust in the progenitor
circumstellar medium (CSM). [ABRIDGED] Possible origins for the NIR emission
are considered. Significant radioactive heating of ejecta dust is ruled out, as
is shock/X-ray-precursor heating of CSM dust. More plausible sources are (a) an
IR-echo from CSM dust driven by the UV/optical peak luminosity, and (b)
emission from newly-condensed dust which formed within a cool, dense shell
produced by the ejecta shock/CSM interaction. We argue that the evidence
favours the condensing dust hypothesis, although an IR-echo is not ruled out.
Within the condensing-dust scenario, the IR luminosity indicates the presence
of at least 0.001 solar masses of dust in the ejecta, and probably considerably
more. Finally, we show that the late-time intrinsic (K-L') evolution of type II
supernovae may provide a useful tool for determining the presence or absence of
a massive CSM around their progenitor stars.


title: Galactic discrete sources of high energy neutrinos

abstract:
  We review recently developed models of galactic discrete sources of high
energy neutrinos. Some of them are based on a simple rescaling of the TeV
$\gamma$-ray fluxes from recently detected galactic sources, such as,
shell-type supernova remnants or pulsar wind nebulae. Others present detailed
and originally performed modeling of processes occurring close to compact
objects, i.e. neutron stars and low mass black holes, which are supposed to
accelerate hadrons close to dense matter and radiation fields. Most of the
models considered in this review optimistically assume that the energy content
in relativistic hadrons is equal to a significant part of the maximum
observable power output in specific sources, i.e. typically $\sim 10%$. This
may give a large overestimation of the neutrino fluxes. This is the case of
models which postulate neutrino production in hadron-photon collisions already
at the acceleration place, due to the likely $e^\pm$ pair plasma domination.
Models postulating neutrino production in hadron-hadron collisions avoid such
problems and therefore seem to be more promising. The neutrino telescopes
currently taking data have not detected any excess from discrete sources yet,
although some models could already be constrained by the limits they are
providing.


title:
Neutrino production in UHECR proton interactions in the infrared
  background

abstract:
  We discuss the contribution of proton photoproduction interactions on the
isotropic infrared/optical background to the cosmic neutrino fluxes. This
contribution has a strong dependence on the proton injection energy spectrum,
and is essential at high redshifts.
  It is thus closely correlated with the cosmological evolution of the ultra
high energy proton sources and of the inrared background itself. These
interactions may also contribute to the source fluxes of neutrinos if the
proton sources are located in regious of high infrared emission and magnetic
fields.


title: Relativistic Effects of our Galaxy's Motion on Circles-in-the-sky

abstract:
  We study the geometric effects of our galaxy's peculiar motion on the
circles-in-the-sky. We show that the shape of these circles-in-the-sky remains
circular, as detected by a local observer with arbitrary peculiar velocity.
Explicit expressions for the radius and center position of such an observed
circle-in-the-sky, as well as for the angular displacement of points on the
circle, are derived. In general, a circle is detected as a circle of different
radius, displaced relative to its original position, and centered at a point
which does not correspond to its detected center in the comoving frame.
Further, there is an angular displacement of points on the circles. These
effects all arise from aberration of cosmic microwave background radiation,
exhausting the purely geometric effects due to the peculiar motion of our
galaxy, and are independent of both the large scale curvature of space and the
expansion of the universe, since aberration is a purely local phenomenon. For a
Lorentz-boosted observer with the speed of our entire galaxy, the maximum
(detectable) changes in the angular radius of a circle, its maximum center
displacement, as well as the maximum angular distortion are shown all to be of
order $\beta=(v/c)$ radians. In particular, two back-to-back matching circles
in a finite universe will have an upper bound of $2|\beta|$ in the variation of
either their radii, the angular position of their centers, or the angular
distribution of points.


title: The 2dF Galaxy Redshift Survey as a Cosmological Laboratory

abstract:
  The 2dF Galaxy Redshift Survey (2dFGRS) of 230,000 redshifts of nearby
(z~0.1) galaxies is now complete. It has allowed the 2dFGRS team and others to
estimate fundamental cosmological parameters and to study galaxy intrinsic
properties. Here we highlight three recent key results from the survey: (i) an
upper limit of about 2eV on the total mass of the three neutrino flavours, and
an intriguing reasonable fitting of the 2dFGRS power spectrum to a Mixed Dark
Matter model without a Cosmological Constant, but with a low Hubble constant;
(ii) the bimodality of the galaxy population in both spectral parameterisation
and in colour; and (iii) the clustering of different galaxy types and evidence
for relative stochastic biasing.


title:
Update on Pulsar B1620$-$26 in M4: Observations, Models, and
  Implications

abstract:
  The combination of ever more precise radio timing data and serendipitous {\it
HST} data has confirmed that the outer companion to PSR B1620$-$26 is a planet.
Here we summarize the observational situation, including preliminary new timing
solutions and the implications of the measured system parameters. We detail the
proposed formation scenarios, discussing the advantages and problems of each
for explaining the origin of the triple, and we speculate on some of the
implications for planet formation in the early universe. Future data on this
system will provide additional constraints on fundamental modes of planet
formation. We predict that many more exchanged planets will be discovered
orbiting recycled pulsars in globular clusters as the sensitivity and duration
of radio timing increases. Strong observational tests of some of the
alternative formation models should be possible with additional data.


title: Black Hole Masses from Reverberation Measurements

abstract:
  We have reanalyzed in a consistent way existing reverberation data for 35
AGNs for the purpose of refining the black hole masses derived from these data.
We find that the precision (or random component of the error) of
reverberation-based black hole mass measurements is typically around 30%,
comparable to the precision attained in measurement of black hole masses in
quiescent galaxies by gas or stellar dynamical methods. As discussed in this
volume by Onken et al., we have established an absolute calibration for AGN
reverberation-based masses by assuming that AGNs and quiescent galaxies follow
an identical relationship between black hole mass and host-galaxy bulge
velocity dispersion. The scatter around this relationship implies that the
typical systematic uncertainties in reverberation-based black hole masses are
smaller than a factor of three. We present a preliminary version of a
mass-luminosity relationship that is much better defined than any previous
attempt. Scatter about the mass-luminosity relationship for these AGNs appears
to be real and could be correlated with either Eddington ratio or source
inclination.


title: Escaping the Big Rip?

abstract:
  We discuss dark energy models which might describe effectively the actual
acceleration of the universe. More precisely, for a 4-dimensional
Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) universe we consider two
situations: First of them, we model dark energy by phantom energy described by
a perfect fluid satisfying the equation of state $P=(\beta-1)\rho$ (with
$\beta<0$ and constant). In this case the universe reaches a ``Big Rip''
independently of the spatial geometry of the FLRW universe. In the second
situation, the dark energy is described by a phantom (generalized) Chaplygin
gas which violates the dominant energy condition. Contrary to the previous
case, for this material content a FLRW universe would never reach a ``big rip''
singularity (indeed, the geometry is asymptotically de Sitter). We also show
how this dark energy model can be described in terms of scalar fields,
corresponding to a minimally coupled scalar field, a Born-Infeld scalar field
and a generalized Born-Infeld scalar field. Finally, we introduce a
phenomenologically viable model where dark energy is described by a phantom
generalized Chaplygin gas.


title: A transiting extrasolar giant planet around the star OGLE-TR-113

abstract:
  We report the independent discovery of a new extrasolar transiting planet
around OGLE-TR-113, a candidate star from the Optical Gravitational Lensing
Experiment. Small radial-velocity variations have been detected based on
observations conducted with the MIKE spectrograph on the Magellan I (Baade)
telescope at the Las Campanas Observatory (Chile) during 2003. We have also
carried out a light-curve analysis incorporating new photometry and realistic
physical parameters for the star. OGLE-TR-113b has an orbital period of only
1.43 days, a mass of 1.08 +/- 0.28 M_Jup, and a radius of 1.09 +/- 0.10 R_Jup.
Similar parameters have been obtained very recently in an independent study by
Bouchy et al., from observations taken a year later. The orbital period of
OGLE-TR-113b, and also that of the previously announced planet OGLE-TR-56b
(P_orb = 1.21 days) -- the first two found photometrically -- are much shorter
than the apparent cutoff of close-in giant planets at 3-4-day periods found
from high-precision radial velocities surveys. Along with a third case reported
by Bouchy et al. (OGLE-TR-132b, P_orb = 1.69 days), these objects appear to
form a new class of ``very hot Jupiters'' that pose very interesting questions
for theoretical study.


title:
Detection of Nitrogen and Neon in the X-ray Spectrum of GP Com with
  XMM/Newton

abstract:
  We report on X-ray spectroscopic observations with XMM/Newton of the
ultracompact, double white dwarf binary, GP Com. With the Reflection Grating
Spectrometers (RGS) we detect the Lyman alpha and beta lines of hydrogen-like
nitrogen (N VII) and neon (Ne X), as well as the helium-like triplets (N VI and
Ne IX) of these same elements. All the emission lines are unresolved. These are
the first detections of X-ray emission lines from a double-degenerate, AM CVn
system. We detect the resonance (r) and intercombination (i) lines of the N VI
triplet, but not the forbidden (f) line. The implied line ratios for N VI, R =
f/i < 0.3, and G = (f + i)/r ~1, combined with the strong resonance line are
consistent with formation in a dense, collision-dominated plasma. Both the RGS
and EPIC/MOS spectra are well fit by emission from an optically thin thermal
plasma (model cevmkl in XSPEC). Helium, nitrogen, oxygen and neon are required
to adequately model the spectrum, however, the inclusion of sulphur and iron
further improves the fit, suggesting these elements may also be present at low
abundance. We confirm in the X-rays the underabundance of both carbon and
oxygen relative to nitrogen, first deduced from optical spectroscopy by Marsh
et al. The average X-ray luminosity of ~3e30 ergs/s implies a mass accretion
rate of ~9e-13 solar masses per year. The implied temperature and density of
the emitting plasma, combined with the presence of narrow emission lines are
consistent with production of the X-ray emission in an optically thin boundary
layer just above the surface of the white dwarf.


title:
Chandra Observations of Radio-Loud Quasars at z > 4: X-rays from the
  Radio Beacons of the Early Universe

abstract:
  We present the results of Chandra observations of six radio-loud quasars
(RLQs) and one optically bright radio-quiet quasar (RQQ) at z = 4.1-4.4. These
observations cover a representative sample of RLQs with moderate radio-loudness
(R ~ 40-400), filling the X-ray observational gap between optically selected
RQQs and the five known blazars at z > 4 (R ~ 800-27000). We study the
relationship between X-ray luminosity and radio-loudness for quasars at high
redshift and constrain RLQ X-ray continuum emission and absorption. From a
joint spectral fit of nine moderate-R RLQs observed by Chandra, we find
tentative evidence for absorption above the Galactic N_H, with a best-fit
neutral intrinsic column density of N_H = 2.4^{+2.0}_{-1.8} x 10^{22} cm^{-2},
consistent with earlier claims of increased absorption toward high-redshift
RLQs. We also search for evidence of an enhanced jet-linked component in the
X-ray emission due to the increased energy density of the cosmic microwave
background (CMB) at high redshift, but we find neither spatial detections of
X-ray jets nor a significant enhancement in the X-ray emission relative to
comparable RLQs at low-to-moderate redshifts. Overall, the z ~ 4-5 RLQs have
basic X-ray properties consistent with comparable RLQs in the local universe,
suggesting that the accretion/jet mechanisms of these objects are similar as
well.


title: X-ray Observations of Stellar Clusters Near the Galactic Center

abstract:
  We report the first detection of X-ray emission from the Quintuplet star
cluster and compare its X-ray emission to that of the Arches star cluster. Four
point sources are significantly detected near the core of the Quintuplet
cluster with a total, absorption-corrected luminosity of ~1\times10^{33} ergs
s^{-1}. Diffuse, thermal emission is also detected near the core of the
Quintuplet cluster with an absorption-corrected luminosity of ~1\times10^{34}
ergs s^{-1}. We analyze the diffuse and point-like emission from the Arches and
Quintuplet and discuss the possibility that they are host to cluster wind
outflows. We also present the results of our search for X-ray emission from
candidate star clusters in the Galactic center (GC) region. We use extinction
estimated by near-IR colors and X-ray spectral fits, as well as other IR
properties, to determine if the candidate clusters are new, GC star clusters.
We find that three of the six candidate clusters found toward the GC are likely
foreground clusters, two of the candidate clusters are not detected in the
X-ray data, but have near-IR extinctions consistent with a GC location, and one
of the candidate clusters has X-ray and near-IR extinctions consistent with
being in the GC. The X-ray and IR emission from the candidate clusters is
compared to the known, massive, GC star clusters.


title:
Sunyaev-Zeldovich effect in WMAP and its effect on cosmological
  parameters

abstract:
  We use multi-frequency information in first year WMAP data to search for the
Sunyaev-Zeldovich (SZ) effect. WMAP has sufficiently broad frequency coverage
to constrain SZ without the addition of higher frequency data: the SZ power
spectrum amplitude is expected to increase 50% from W to Q frequency band.
This, in combination with the low noise in WMAP, allows us to strongly
constrain the SZ contribution. We derive an optimal frequency combination of
WMAP cross-spectra to extract SZ in the presence of noise, CMB, and radio point
sources, which are marginalized over. We find that the SZ contribution is less
than 2% (95% c.l.) at the first acoustic peak in W band. Under the assumption
that the removed radio point sources are not correlated with SZ this limit
implies sigma_8<1.07 at 95% c.l. We investigate the effect on the cosmological
parameters of allowing an SZ component. We run Monte Carlo Markov Chains with
and without an SZ component and find that the addition of SZ does not affect
any of the cosmological conclusions. We conclude that SZ does not contaminate
the WMAP CMB or change cosmological parameters, refuting the recent claims that
they may be corrupted.


title: Inflation

abstract:
  The basic workings of inflationary models are summarized, along with the
arguments that strongly suggest that our universe is the product of inflation.
I describe the quantum origin of density perturbations, giving a heuristic
derivation of the scale invariance of the spectrum and the leading corrections
to scale invariance. The mechanisms that lead to eternal inflation in both new
and chaotic models are described. Although the infinity of pocket universes
produced by eternal inflation are unobservable, it is argued that eternal
inflation has real consequences in terms of the way that predictions are
extracted from theoretical models. Although inflation is generically eternal
into the future, it is not eternal into the past: it can be proven under
reasonable assumptions that the inflating region must be incomplete in past
directions, so some physics other than inflation is needed to describe the past
boundary of the inflating region. The ambiguities in defining probabilities in
eternally inflating spacetimes are reviewed, with emphasis on the youngness
paradox that results from a synchronous gauge regularization technique.


title:
A Dynamical Model for the Orbit of the Andromeda Galaxy M31 and the
  Origin of the Local Group of Galaxies

abstract:
  We propose a new model for the origin and evolution of the Local Group of
Galaxies (LGG) which naturally explains the formation of the Magellanic Clouds
and their large orbital angular momenta around the Galaxy. The basic idea is
that an off-center hydrodynamical collision occurred some 10 Gyr ago between
the primordial gas-rich Andromeda galaxy and the similar Galaxy, and compressed
the halo gas to form the LGG dwarf galaxies including the Magellanic Clouds. In
this model, new-born dwarf galaxies can be expected to locate near the orbital
plane of these two massive galaxies. In order to see the reality of this model,
we reexamine the two-dimensional sky distribution of the LGG members and the
Magellanic Stream, we confirm an earlier and widely-discussed idea that they
align along two similar great circles, each with an angular width of $\sim
30^{\circ}$, and the planes of these circles are approximately normal to the
line joining the present position of the sun and the Galactic center. Further
we make a three-dimensional distribution map of these objects, and observe it
from various directions. A well-defined plane of finite thickness is found,
within which most of the member galaxies are confined, supporting the existence
of the above circles on the sky. Thus we could determine the orbital elements
of M31 relative to the Galaxy through reproducing the well-studied dynamics of
the LMC and the SMC around the Galaxy. The expected proper motion of M31 is
$(\mu_l, \mu_b)=(38 \mu as/yr, -49 \mu as/yr)$. Probable orbital motions of the
other dwarfs are also determined, and the corresponding proper motion for each
object is given to compare with observations in near future.


title: Elastic Inflation

abstract:
  Inflation of a universe filled by an elastic continuous medium is considered.
Elastic inflation, while capable of describing current observations, is
qualitatively different from standard inflationary models. The scalar and
tensor modes keep evolving after crossing the horizon. Due to this superhorizon
evolution, the amplitude of the tensor mode (inflationary gravitational wave)
is not simply proportional to the energy density of the universe at the time of
horizon crossing. The spectral index of tensor modes can be positive.


title:
PSRCHIVE and PSRFITS An Open Approach to Radio Pulsar Data Storage and
  Analysis

abstract:
  A new set of software applications and libraries for use in the archival and
analysis of pulsar astronomical data is introduced. Known collectively as the
PSRCHIVE scheme, the code was developed in parallel with a new data storage
format called PSRFITS, which is based on the Flexible Image Transport System
(FITS). Both of these projects utilise a modular, object-oriented design
philosophy. PSRCHIVE is an open source development environment that
incorporates an extensive range of C++ object classes and pre-built command
line and graphical utilities. These deal transparently and simultaneously with
multiple data storage formats, thereby enhancing data portability and
facilitating the adoption of the PSRFITS file format. Here, data are stored in
a series of modular header-data units that provide flexibility and scope for
future expansion. As it is based on FITS, various standard libraries and
applications may be used for data input/output and visualisation. Both PSRCHIVE
and PSRFITS are made publicly available to the academic community in the hope
that this will promote their widespread use and acceptance.


title:
XMM observations of the narrow-line QSO PHL 1092: Detection of a high
  and variable soft component

abstract:
  We present results based on an XMM-Newton observation of the high luminosity
narrow-line QSO PHL 1092 performed in 2003 January. The 0.3 - 10 keV spectrum
is well described by a model which includes a power-law (Gamma ~ 2.1) and two
blackbody components (kT ~ 130 eV and kT ~ 50 eV). The soft X-ray excess
emission is featureless and contributes ~ 80% to the total X-ray emission in
the 0.3 - 10 keV band. The most remarkable feature of the present observation
is the detection of X-ray variability at very short time scale: the X-ray
emission varied by 35% in about 5000 s. We find that this variability can be
explained by assuming that only the overall normalization varied during the
observation. There was no evidence for any short term spectral variability and
the spectral shape was similar even during the ASCA observation carried out in
1997. Considering the high intrinsic luminosity (~ 2x10^45 erg/s) and the large
inferred mass of the putative black hole (~ 1.6x10^8 M_sun), the observed time
scale of variability indicates emission at close to Eddington luminosity
arising from very close to the black hole. We suggest that PHL 1092 in
particular (and narrow line Seyfert galaxies in general) is a fast rotating
black hole emitting close to its Eddington luminosity and the X-ray emission
corresponds to the high-soft state seen in Galactic black hole sources.


title:
WR20a: a massive cornerstone binary system comprising two extreme
  early-type stars

abstract:
  We analyse spectroscopic observations of WR20a revealing that this star is a
massive early-type binary system with a most probable orbital period of \sim
3.675 days. Our spectra indicate that both components are most likely of WN6ha
or O3If^*/WN6ha spectral type. The orbital solution for a period of 3.675 days
yields extremely large minimum masses of 70.7 \pm 4.0 and 68.8 \pm 3.8
M_{\odot} for the two stars. These properties make WR20a a cornerstone system
for the study of massive star evolution.


title: The (n,g) cross sections of short-living s-process branching points

abstract:
  An experimental method to determine the (n,g) cross section of short-living
s-process branching points using data of the inverse (g,n) reaction is
presented. The method was used to observe the branching point nucleus 95Zr
because the elemental abundance patterns corresponding to this branching point
cannot be reproduced by full stellar models and a possible error source is the
neutron capture cross section of 95Zr. The analysis of the experiment is still
under progress, we will outline the current status in this manuscript.


title:
Correlation between grain growth and disk geometry in Herbig Ae/Be
  systems

abstract:
  We have calculated the (sub-)mm spectral indices of 26 Herbig Ae/Be stars,
for which we can determine the infrared spectral energy distribution (SED). We
find a clear correlation between the strength of the ratio of the near- to
mid-infrared excess of these sources, and the slope of the (sub-)mm energy
distribution. Based on earlier multi-dimensional modeling of disks around
Herbig Ae stars, we interpret this as a correlation between the geometry of the
disk (flared or self-shadowed) and the size of the grains: self-shadowed disks
have, on average, larger grains than their flared counterparts. These data
suggest that the geometry of a young stellar disk evolves from flared to
self-shadowed.


title: Quakes in Solid Quark Stars

abstract:
  A starquake mechanism for pulsar glitches is developed in the solid quark
star model. It is found that the general glitch natures (i.e., the glitch
amplitudes and the time intervals) could be reproduced if solid quark matter,
with high baryon density but low temperature, has properties of shear modulus
\mu = 10^{30~34} erg/cm^3 and critical stress \sigma_c = 10^{18~24} erg/cm^3.
The post-glitch behavior may represent a kind of damped oscillations.


title: Hydrodynamical effects in internal shock of relativistic outflows

abstract:
  We study both analytically and numerically hydrodynamical effects of two
colliding shells, the simplified models of the internal shock in various
relativistic outflows such as gamma-ray bursts and blazars. We pay particular
attention to three interesting cases: a pair of shells with the same rest mass
density (``{\it equal rest mass density}''), a pair of shells with the same
rest mass (``{\it equal mass}''), and a pair of shells with the same bulk
kinetic energy (``{\it equal energy}'') measured in the intersteller medium
(ISM) frame. We find that the density profiles are significantly affected by
the propagation of rarefaction waves. A split-feature appears at the contact
discontinuity of two shells for the ``equal mass'' case, while no significant
split appears for the ``equal energy'' and ``equal rest mass density'' cases.
The shell spreading with a few ten percent of the speed of light is also shown
as a notable aspect caused by rarefaction waves. The conversion efficiency of
the bulk kinetic energy to internal one is numerically evaluated. The time
evolutions of the efficiency show deviations from the widely-used inellastic
two-point-mass-collision model.


title: The structure of the ICM from High Resolution SPH simulations

abstract:
  We present results from a set of high (512^3 effective resolution), and
ultra-high (1024^3) SPH adiabatic cosmological simulations of cluster formation
aimed at studying the internal structure of the intracluster medium (ICM). We
derive a self-consistent analytical model of the structure of the intracluster
medium (ICM). We discuss the radial structure and scaling relations expected
from purely gravitational collapse, and show that the choice of a particular
halo model can have important consequences on the interpretation of
observational data. The validity of the approximations of hydrostatic
equilibrium and a polytropic equation of state are checked against results of
our simulations. The properties of the ICM are fully specified when a
'universal' profile is assumed for either the dark or the baryonic component.
We also show the first results from an unprecedented large-scale simulation of
500 Mpc/h and 2 times 512^3 gas and dark matter particles. This experiment will
make possible a detailed study of the large-scale distribution of clusters as a
function of their X-ray properties.


title: Flared Disks and Silicate Emission in Young Brown Dwarfs

abstract:
  We present mid-infrared photometry of three very young brown dwarfs located
in the $\rho$ Ophiuchi star-forming region -- GY5, GY11 and GY310 --obtained
with the Subaru 8-meter telescope. All three sources were detected at 8.6 and
11.7$\mu$m, confirming the presence of significant mid-infrared excess arising
from optically thick dusty disks. The spectral energy distributions of both
GY310 and GY11 exhibit strong evidence of flared disks; flat disks can be ruled
out for these two brown dwarfs. The data for GY5 show large scatter, and are
marginally consistent with both flared and flat configurations. Inner holes a
few substellar radii in size are indicated in all three cases (and especially
in GY11), in agreement with magnetospheric accretion models. Finally, our
9.7$\mu$m flux for GY310 implies silicate emission from small grains on the
disk surface (though the data do not completely preclude larger grains with no
silicate feature). Our results demonstrate that disks around young substellar
objects are analogous to those girdling classical T Tauri stars, and exhibit a
similar range of disk geometries and dust properties.


title: Ionized gas and stellar kinematics of seventeen nearby spiral galaxies

abstract:
  Ionized gas and stellar kinematics have been measured along the major axes of
seventeen nearby spiral galaxies of intermediate to late morphological type. We
discuss the properties of each sample galaxy distinguishing between those
characterized by regular or peculiar kinematics. In most of the observed
galaxies ionized gas rotates more rapidly than stars and have a lower velocity
dispersion, as is to be expected if the gas is confined in the disc and
supported by rotation while the stars are mostly supported by dynamical
pressure. In a few objects, gas and stars show almost the same rotational
velocity and low velocity dispersion, suggesting that their motion is dominated
by rotation.
  Incorporating the spiral galaxies studied by Bertola et al. (1996), Corsini
et al. (1999, 2003) and Vega Beltran et al. (2001) we have compiled a sample of
50 S0/a-Scd galaxies, for which the major-axis kinematics of the ionized gas
and stars have been obtained with the same spatial (~1'') and spectral
(~50km/s) resolution, and measured with the same analysis techniques. This
allowed us to address the frequency of counterrotation in spiral galaxies. It
turns out that less than 12% and less than 8% (at the 95% confidence level) of
the sample galaxies host a counterrotating gaseous and stellar disc,
respectively. The comparison with S0 galaxies suggests that the retrograde
acquisition of small amounts of external gas gives rise to counterrotating
gaseous discs only in gas-poor S0s, while in gas-rich spirals the newly
acquired gas is swept away by the pre-existing gas. Counterrotating gaseous and
stellar discs in spirals are formed only from the retrograde acquisition of
large amounts of gas exceeding that of pre-existing gas, and subsequent star
formation, respectively.


title:
Discovery of an Optical Counterpart to the Supersoft X-ray Source in the
  Globular Cluster M3

abstract:
  We report the detection, with HST, of an optical counterpart to the transient
supersoft X-ray source 1E 1339.8+2837, in the globular cluster M3. The
counterpart is found near the faint end of the subgiant branch in the V vs V-I
color magnitude diagram, but is extremely bright in U. Variability is detected
over a range of timescales suggesting the presence of an accretion disk and
perhaps also ellipsoidal variations of the subgiant secondary. The optical
colors of the binary are similar to those of cataclysmic variables recently
discovered in 47 Tucanae and NGC 6397. We suggest that magnetically channeled
accretion may explain the relatively low X-ray luminosity of this source's
supersoft state.


title:
Dust cloud formation in stellar environments. II. Two-dimensional models
  for structure formation around AGB stars

abstract:
  This paper reports on computational evidence for the formation of cloud-like
dust structures around C-rich AGB stars. This spatio-temporal structure
formation process is caused by a radiative/thermal instability of dust forming
gases as identified by Woitke et al.(2000). Our 2D (axisymmetric) models
combine a time-dependent description of the dust formation process according to
Gail & Sedlmayr (1988) with detailed, frequency-dependent continuum radiative
transfer by means of a Monte Carlo method (Niccolini et al.2003) in an
otherwise static medium (v=0). These models show that the formation of dust
behind already condensed regions, which shield the stellar radiation field, is
strongly favoured. In the shadow of these clouds, the temperature decreases by
several hundred Kelvin which triggers the subsequent formation of dust and
ensures its thermal stability. Considering an initially dust-free gas with
small density inhomogeneities, we find that finger-like dust structures develop
which are cooler than the surroundings and point towards the centre of the
radiant emission, similar to the cometary knots observed in planetary nebulae
and star formation regions. Compared to a spherical symmetric reference model,
the clumpy dust distribution has little effect on the spectral energy
distribution, but dominates the optical appearance in near IR monochromatic
images.


title: Long Period Variables in the Magellanic Clouds: OGLE + 2MASS + DENIS

abstract:
  (abridged) The 68000 I-band light curves of variable stars detected by the
OGLE survey in the Large and Small Magellanic Clouds (MCs) are fitted by
Fourier series, and also correlated with the DENIS and 2MASS databases and with
lists of spectroscopically confirmed M-, S- and C-stars. Lightcurves and the
results of the lightcurve fitting (periods and amplitudes) and DENIS and 2MASS
magnitudes are presented for 2277 M-,S-,C-stars in the MCs. The following
aspects are discussed: the K-band period-luminosity relations for the
spectroscopically confirmed AGB stars, period changes over a timespan of about
17 years in a subset of about 400 LPVs, and candidate obscured AGB stars.


title:
Chaos and the Effects of Planetary Migration on the Orbit of S/2000 S5
  Kiviuq

abstract:
  Among the many new irregular satellites that have been discovered in the last
five years, at least six are in the so-called Kozai resonance. Due to solar
perturbations, the argument of pericenter of a satellite usually precesses from
0 to 360 degrees. However, at inclinations higher than 39.3 degrees and lower
than 140.7 degrees a new kind of behavior occurs for which the argument of
pericenter oscillates around +/-90 degrees. In this work we will concentrate on
the orbital history of the saturnian satellite S/2000 S5 Kiviuq, one of the
satellites currently known to be in such resonance Kiviuq's orbit is very close
to the separatrix of the Kozai resonance. Due to perturbations from the other
jovian planets, it is expected that orbits near the Kozai separatrix may show
significant chaotic behavior. This is important because chaotic diffusion may
transfer orbits from libration to circulation, and vice versa. To identify
chaotic orbits we used two well-known methods: the Frequency Analysis Method
(Laskar 1990) and Maximum Lyapunov Exponents (Benettin et al. 1980). Our
results show that the Kozai resonance is crossed by a web of secondary
resonances, whose arguments involve combinations of the argument of pericenter,
the argument of the Great Inequality, longitude of the node, and other terms
related to the secular frequencies g5, g6, and s6. Many test orbits whose
precession period is close to the period of the Great Inequality (883 yrs), or
some of its harmonics, are trapped by these secondary resonances, and show
significant chaotic behavior. Planetary migration, by moving the locations of
these secondary resonances, may have depleted an original population of Kozai
resonators.


title: Outflows and jets from massive star-forming clusters

abstract:
  Studying outflows from young massive star-forming clusters allows one to
deduce physical processes that lead to the formation of the most massive stars.
I will review the current state of high-spatial-resolution interferometric
(sub-)mm studies of massive molecular outflows and their implications for
high-mass star formation. A possible evolutionary scenario for massive outflows
with highly collimated structures at the very beginning and more wind-like
outflows at later stages will be outlined.


title: Does the 3.3 micron PAH Emission Feature Require UV Excitation?

abstract:
  The unidentified infrared bands (UIBs) have been observed in virtually every
dusty astrophysical environment investigated. The UIB carrier must be abundant
and ubiquitous. Strong evidence points to polycyclic aromatic hydrocarbons
(PAHs) as likely candidates, but the identification is not complete. Additional
diagnostics are needed to further constrain the UIB carrier, such as probing
excitation sources which range from UV-strong to UV-weak, in order to determine
the ``band gap'' of the UIB carrier. Observations and models suggest that the
UIBs can be found in sources with weak UV fields. To that end, we present new
results of observing the 3.3 micron spectral region in six stars embedded in
reflection nebulae, and in six Vega-like stars. These objects have effective
temperatures ranging from 3500 to 12,000 K. Their environments include dust
that should be relatively unprocessed (reflection nebulae) and dust that has
most likely undergone significant processing (Vega-like) by the embedded
illumination source. Together with data from the literature, we have a sample
of 27 sightlines. Our analysis suggests that neither the strength of the UV
field impinging on the dust nor the effective temperature of the star is the
determining factor in whether the 3.3 micron UIB emission is present in an
object. We found three detections of the 3.3 micron-emission band, one in a
Vega-type object, one in a Herbig Ae/Be object and one in a reflection nebula,
and all with disks. The role of disk geometry is likely to be important in
revealing or obscuring the photo-dissociation regions from which the UIB
emission arises.


title: The Properties and the Evolution of the Highly Ionized Gas in MR2251-178

abstract:
  (abridged) We present the first XMM-Newton observations of the radio-quiet
quasar MR2251-178 obtained in 2000 and 2002. The EPIC-pn spectra show a
power-law continuum with a slope of 1.6 at high energies absorbed by at least
two warm absorbers (WAs) intrinsic to the source. The underlying continuum in
the earlier observation shows a soft excess at low X-ray energies which can be
modeled as an additional power-law with a slope of 2.9. The high-resolution
grating spectrum obtained in 2002 shows emission lines from N VI, O VII, O
VIII, Ne IX, and Ne X, as well as absorption lines from the low-ionization ions
of O III, O IV, and O V, and other confirmed and suspected weaker absorption
lines. We suggest a model for the high-resolution spectrum which consist of two
or three WA components. The two-components model has a high-ionization WA with
a column density of 10^21.5 - 10^21.8 cm^-2 and a low-ionization absorber with
a column density of 10^20.3 cm^-2. In the three-components model we add a lower
ionization component that produce the observed iron M-shell absorption lines.
We investigate the spectral variations in MR2251-178 over a period of 8.5 years
using data from ASCA, BeppoSAX, and XMM-Newton. All X-ray observations can be
fitted with the above EPIC-pn model. The 8.5 year history of the source
suggests a changing X-ray absorber due to material that enters and disappears
from the line-of-sight on timescales of several months. We also present the
entire FUSE spectrum of MR2251-178. We detect emission from N III, C III, and O
VI and at least 4 absorption systems in C III, H I, and O VI, one at -580 km/s
and at least 3 others which are blended together and form a wide trough
covering the velocity range of 0 to -500 km/s. The general characteristics of
the UV and X-ray absorbers are consistent with an origin in the same gas.


title:
Opaque or transparent? A link between neutrino optical depths and the
  characteristic duration of short gamma-ray bursts

abstract:
  Cosmological gamma ray bursts (GRBs) are thought to occur from violent
hypercritical accretion onto stellar mass black holes, either following core
collapse in massive stars or compact binary mergers. This dichotomy may be
reflected in the two classes of bursts having different durations. Dynamical
calculations of the evolution of these systems are essential if one is to
establish characteristic, relevant timescales. We show here for the first time
the result of dynamical simulations, lasting approximately one second, of
post--merger accretion disks around black holes, using a realistic equation of
state and considering neutrino emission processes. We find that the inclusion
of neutrino optical depth effects produces important qualitative temporal and
spatial transitions in the evolution and structure of the disk, which may
directly reflect upon the duration and variability of short GRBs.


title: Assessing the effects of foregrounds and sky removal in WMAP

abstract:
  Many recent analyses have indicated that large scale WMAP data display
anomalies that appear inconsistent with the standard cosmological paradigm.
However, the effects of foreground contamination, which require elimination of
some fraction of the data, have not been carefully investigated due to the
complexity in the analysis. Here we develop a general formalism of how to
incorporate these effects in any analysis of this type. Our approach is to
compute the full multi-dimensional probability distribution function of all
possible sky realizations that are consistent with the data and with the
allowed level of contamination. As an example we apply this method to compute
the joint probability distribution function for the possible realizations of
quadrupole and octopole using the WMAP data. This 12 dimensional distribution
function is explored using the Markov Chain Monte Carlo technique. The
resulting chains are used to asses the statistical significance of the low
quadrupole using frequentist methods, the quadrupole-octopole alignment using
several methods (angular momentum dispersion, multipole vectors and a new
method based of feature matching) and the quadrupole-octopole aligment with
ecliptic.


title: Possible astrophysical clues of dark matter

abstract:
  The physics of the supernova may provide a clue of the cosmological dark
matter. In the absence of new physics, the supernova calculations do not
explain the observed velocities of pulsars. However, if there exists a singlet
fermion with mass in the 1-20 keV range and a small mixing with neutrinos, this
particle could be emitted asymmetrically from a cooling neutron star in the
event of a supernova explosion. The asymmetry could explain the long-standing
puzzle of pulsar velocities. The same particle could be the dark matter.
Observations of X-ray telescopes, as well as a future detection of
gravitational waves from a nearby supernova can confirm or rule out this
possibility.


title:
The geometry of the double-pulsar system J0737-3039 from systematic
  intensity variations

abstract:
  The recent discovery of J0737-3039A & B-two pulsars in a highly relativistic
orbit around one another - offers an unprecedented opportunity to study the
elusive physics of pulsar radio emission. The system contains a rapidly
rotating pulsar with a spin period of 22.7 ms and a slow companion with a spin
period of 2.77 s, hereafter referred to as 'A' and 'B', respectively. A unique
property of the system is that the pulsed radio flux from B increases
systematically by almost two orders-of-magnitude during two short portions of
each orbit. Here, we describe a geometrical model of the system that
simultaneously explains the intensity variations of B and makes definitive and
testable predictions for the future evolution of the emission properties of
both stars. Our model assumes that B's pulsed radio flux increases when
illuminated by emission from A. This model provides constraints on the spin
axis orientation and emission geometry of A and predicts that its pulse profile
will evolve considerably over the next several years due to geodetic precession
until it disappears entirely in 15-20 years.


title: Radio-wave propagation in the non-Gaussian interstellar medium

abstract:
  Radio waves propagating from distant pulsars in the interstellar medium
(ISM), are refracted by electron density inhomogeneities, so that the intensity
of observed pulses fluctuates with time. The theory relating the observed pulse
time-shapes to the electron-density correlation function has developed for 30
years, however, two puzzles have remained. First, observational scaling of
pulse broadening with the pulsar distance is anomalously strong; it is
consistent with the standard model only when non-uniform statistics of electron
fluctuations along the line of sight are assumed. Second, the observed pulse
shapes are consistent with the standard model only when the scattering material
is concentrated in a narrow slab between the pulsar and the Earth.
  We propose that both paradoxes are resolved at once if one assumes stationary
and uniform, but non-Gaussian statistics of the electron-density distribution.
Such statistics must be of Levy type, and the propagating ray should exhibit a
Levy flight. We propose that a natural realization of such statistics may be
provided by the interstellar medium with random electron-density
discontinuities. We develop a theory of wave propagation in such a non-Gaussian
random medium, and demonstrate its good agreement with observations. The
qualitative introduction of the approach and the resolution of the
anomalous-scaling paradox was presented earlier in [PRL 91, 131101 (2003); ApJ
584, 791 (2003)].


title:
Radio galaxies in cooling core clusters. Restarted activity in the
  nucleus of 3C317?

abstract:
  We present the results of VLBA observations of the radio galaxy 3C317,
associated with the cD galaxy UGC 09799 at the centre of the cooling core
cluster of galaxies A2052. These observations were carried out at 1.7 GHz, 4.9
GHz and 8.3 GHz, in polarimetric mode, and allowed us to image the parsec scale
region of the source. Our analysis suggests that the nucleus of 3C317 hosts a
very young radio source. The estimated radiative age for the radio structure
within the inner 10 pc is $\sim$ 170 yr. Given the existence of extended radio
emission on the arcsecond scale, we suggest that 3C317 is a restarted radio
galaxy. The implications of this result in the light of the interaction between
radio plasma and thermal hot gas in clusters of galaxies are briefly discussed.


title:
The calibration of the RGB Tip as a Standard Candle: Extension to Near
  Infrared colors and higher metallicity

abstract:
  New empirical calibrations of the Red Giant Branch Tip in the I,J,H and K
bands based on two fundamental pillars, namely omega Centauri and 47 Tucanae,
have been obtained by using a large optical and near infrared photometric
database. Our best estimates give M_I(TRGB)= -4.05 pm 0.12, M_J(TRGB)= -5.20 pm
0.16, M_H(TRGB)= -5.94 pm 0.18 and M_K(TRGB) = -6.04 pm 0.16 at [M/H]=-1.5
(omega Cen) and M_I(TRGB)= -3.91 pm 0.13, M_J(TRGB)= -5.47 pm 0.25, M_H(TRGB)=
-6.35 pm 0.30 and M_K(TRGB)= -6.56 pm 0.20 at [M/H]=-0.6 (47 Tuc). With these
new empirical calibrations we also provide robust relations of the TRGB
magnitude in I, J, H and K bands as a function of the global metallicity
([M/H]). It has also been shown that our calibrations self-consistently provide
a distance modulus of the Large Magellanic Cloud in good agreement with the
standard value ((m-M)_0 = 18.50)).


title: The oxygen abundance gradient in M101: the reliability of the P method

abstract:
  We present the oxygen abundance determination for 90 HII regions in the inner
parts of the grand design galaxy M101. The abundances were derived employing
the P method (Pilyugin 2001a). A comparison is made with previous
determinations using another calibration and direct measurements of electron
temperature to derive the oxygen abundance. The results show agreement with the
abundances derived from the electron temperature method and also show that the
older calibration is not as accurate as the P method.


title: 2QZJ215454.3-305654: a radio-quiet BL Lac object or lineless QSO?

abstract:
  High signal-to-noise spectroscopy has established a redshift of z=0.494 for
the source 2QZJ215454.3-305654, originally selected from the 2dF/6dF QSO
Redshift Surveys as one of 45 candidate BL Lac objects displaying a featureless
continuum at optical wavelengths. Radio observations using the Australia
Telescope Compact Array at 1.4 GHz place a 3\sigma upper limit on the object's
radio flux density of approx 0.14mJy. The radio-to-optical flux ratio of this
object is thus more than 7 times lower than the lowest such ratio observed in
BL Lac objects. While the optical properties of 2QZJ215454.3-305654 are
consistent with a BL Lac identification, the lack of radio and/or X-ray
emission is not. It is uncertain whether this object is an AGN dominated by
optical continuum emission from an accretion disk, or is similar to a BL Lac
object with optical nonthermal emission from a relativistic jet.


title:
Super massive black holes in spiral galaxies: HST/STIS observations for
  3 new objects

abstract:
  We present long-slit HST/STIS measurements of the ionized-gas kinematics in
the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The
sample galaxies have been selected on the basis of their ground-based
spectroscopy, for displaying a strong central velocity gradient for the ionized
gas, which is consistent with the presence of a circum nuclear keplerian disk
(CNKD, Bertola et al. 1998; Funes et al. 2002) rotating around a super massive
black hole (SMBH). For each target galaxy we obtained the H_alpha and [NII]
6583 AA kinematics along the major axis and two 0"25 parallel offset positions.
Out of three objects only NGC 4435 turned out to have a disk of ionized gas in
regular motion and a regular dust-lane morphology. Preliminary modeling
indicates a SMBH mass one order of magnitude lower than the one expected from
the M-sigma relation for galaxies (Ferrarese & Merritt 2000; Gebhardt et al.
2000).


title: A young binary Brown Dwarf in the R-CrA star formation region

abstract:
  We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC
and STIS), VLT (FORS2) and Keck (HIRES) of the dM8 ultra-cool dwarf DENIS-P
J185950.9-370632, located in the R-CrA region. The presence of lithium
absorption at 670.8 nm and the strong Halpha emission indicate a young age and
a sub-stellar mass. Our diffraction-limited images resolve a companion at the
separation limit of HST/ACS (~0.06"). The 2.1 mJy flux in the LW2 filter
(5.0-8.5 microns) of the Infrared Space Observatory (see 1999A&A...350..883)
likely corresponds to an infrared excess, suggesting the presence of
circumstellar material. Proper motion and photometric measurements, as well as
the Halpha activity, confirm membership in the R-CrA star forming region. If
confirmed by further observations, DENIS-P J185950.9-370632 would be the first
accreting sub-stellar multiple system observed to date.


title: The Peculiar Pulsations of PY Vul

abstract:
  The pulsating white dwarf star PY Vul (G~185-32) exhibits pulsation modes
with peculiar properties that set it apart from other variable stars in the ZZ
Ceti (DAV) class. These peculiarities include a low total pulsation amplitude,
a mode with bizarre amplitudes in the ultraviolet, and a mode harmonic that
exceeds the amplitude of its fundamental. Here, we present optical, time series
spectroscopy of PY Vul acquired with the Keck II LRIS spectrograph. Our
analysis has revealed that the mode with unusual UV amplitudes also has
distinguishing characteristics in the optical. Comparison of its line profile
variations to models suggests that this mode has a spherical degree of four. We
show that all the other peculiarities in this star are accounted for by a
dominant pulsation mode of l=4, and propose this hypothesis as a solution to
the mysteries of PY Vul.


title:
Period-colour and amplitude-colour relations in classical Cepheid
  variables II: the Galactic Cepheid model

abstract:
  In this paper, we construct full amplitude non-linear hydrodynamical models
of fundamental mode Galactic Cepheids and analyze the resulting theoretical
period-colour and amplitude-colour relations at maximum, mean and minimum
light. These theoretical relations match the general form of the observed
relations well. This agreement is, to some extent, independent of the
mass-luminosity relations used, pulsation code, numerical techniques, details
of the input physics and methods to convert theoretical quantities, such as
bolometric luminosity and temperature, to observational quantities, such as V
band magnitudes or $(V-I)$ colours. We show that the period-colour and
amplitude-colour properties of fundamental mode Galactic Cepheids with periods
such that $\log (P)>0.8$ can be explained by a simple application of the
Stefan-Boltzmann law and the interaction of the photosphere with the hydrogen
ionization front. We discuss the implications of our results for explaining the
behavior of Galactic Cepheid period-colour, and period-luminosity relations at
mean light.


title: Structuring eccentric-narrow planetary rings

abstract:
  (Abridged) A simple and general description of the dynamics of a narrow
eccentric ring is presented.We view an eccentric ring which precesses uniformly
at a slow rate as exhibiting a global $m=1$ mode originating from a standing
wave superposed on an axisymmetric background.We adopt a continuum description
using the language of fluid dynamics which gives equivalent results for the
secular dynamics of thin rings as the the well known description using discrete
elliptical streamlines formulated by Goldreich and Tremaine (1979). We use this
to discuss the non linear mode interactions that appear through the excitation
of higher $m$ modes due to the coupling of the $m=1$ mode with an external
satellite potential, showing that they can lead to the excitation of the $m=1$
mode through a feedback process.Two conditions for the maintainance of a steady
$m=1$ mode are obtained. One,being the condition for the normal mode pattern to
precess uniformly requires a balance between the differential precession
induced by the oblateness of the central planet,self-gravity and collisional
effects and is the continuum form of that obtained from the $N$ streamline
model of Goldreich and Tremaine (1979).The other condition is for the steady
maintenance of the non-zero radial action of the ring on account of the normal
mode.This requires a balance between input due to eccentric resonances due to
external satellites and additional collisional damping associated with the
presence of the $m=1$ mode We estimate that such a balance can occur in the
$\epsilon-$ring of Uranus,given its currently observed physical and orbital
parameters.


title: Solar wind induced magnetic field around the unmagnetized Earth

abstract:
  The Earth is a planet with a dipolar magnetic field which is agitated by a
magnetized plasma wind streaming from the Sun. The magnetic field shields the
Earth's surface from penetrating high energy solar wind particles, as well as
interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds
of times over the last 400 million years. These polarity reversals correspond
to drastic breakdowns of the dynamo action. The question arises what the
consequences for the Earth's atmosphere, climate, and, in particular, biosphere
are. It is shown by kinematic estimates and three-dimensional plasma-neutral
gas simulations that the solar wind can induce very fast a magnetic field in
the previously completely unmagnetized Earth's ionosphere that is strong enough
to protect Earth from cosmic radiations comparable to the case of an intact
magnetic dynamo.


title: Microlensing by the Halo MACHOs with Spatially Varying Mass Function

abstract:
  The main aim of microlensing experiments is to evaluate the mean mass of
massive compact halo objects (MACHOs) and the mass fraction of the Galactic
halo made by this type of dark matter. Statistical analysis shows that by
considering a Dirac-Delta mass function (MF) for the MACHOs, their mean mass is
about that of a white dwarf star. This result is, however, in discrepancy with
other observations such as those of non-observed expected white dwarfs in the
Galactic halo which give rise to metal abundance, polluting the interstellar
medium by their evolution. Here we use the hypothesis of the spatially varying
MF of MACHOs, proposed by Kerins and Evans to interpret microlensing events. In
this model, massive lenses with a lower population contribute to the
microlensing events more frequently than do dominant brown dwarfs. This effect
causes the mean mass of the observed lenses to be larger than the mean mass of
all the lenses. A likelihood analysis is performed to find the best parameters
of the spatially varying MF that are compatible with the duration distribution
of Large Magellanic Cloud microlensing candidates of the MACHO experiment.


title:
Discovery of hard non-thermal pulsed X-ray emission from the anomalous
  X-ray pulsar 1E 1841-045

abstract:
  We report the discovery of non-thermal pulsed X-ray/soft gamma-ray emission
up to about 150 keV from the anomalous X-ray pulsar AXP 1E 1841-045 located
near the centre of supernova remnant Kes 73 using RXTE PCA and HEXTE data. The
morphology of the double-peaked pulse profile changes rapidly with energy from
2 keV up to about 8 keV, above which the pulse shape remains more or less
stable. The pulsed spectrum is very hard, its shape above 10 keV can be
described well by a power law with a photon index of 0.94 +/- 0.16. 1E 1841-045
is the first AXP for which such very-hard pulsed emission has been detected,
which points to an origin in the magnetosphere of a magnetar.


title:
Gas Around Active Galactic Nuclei and New Phase Calibration Strategies
  for High-Frequency VLBI

abstract:
  We have a project to measure magnetic fields in the obscuring tori of AGNs.
We observed five free-free absorbed jets in radio galaxies with polarimetric
VLBI at 15 GHz to determine Faraday rotation measures. Surprisingly, all
sources are unpolarized, putting severe constraints on the degree of magnetic
field turbulence and the gas distribution in these objects. We have further
carried out multi-frequency VLBI monitoring of the Seyfert 2 galaxy NGC 3079
and find unusually steep and inverted spectra in the radio components, and
derive general properties of Seyfert galaxies using published VLBI observations
of Seyfert galaxies.
  We have developed a new phase-referencing technique for high frequency VLBI
observations with the VLBA. Instead of inserting short scans on a calibrator
into the target source observations, the target source is continuously observed
while rapidly switching between the target frequency and a lower reference
frequency. We demonstrate that the technique allows phase calibration almost
reaching the thermal noise limit and present the first detection of the AGN in
NGC 4261 at 86 GHz. This is the weakest source ever detected with VLBI at that
frequency.


title: HD 137510: An Oasis in the Brown Dwarf Desert

abstract:
  Since the beginning of precise Doppler surveys, which have had stunning
success in detecting extrasolar planetary companions, one surprising enigma has
emerged: the relative paucity of spectroscopic binaries where the secondary
mass lies in between the stellar and planetary mass regime. This gap in the
mass function for close-in (a < 3 - 4 AU) companions to solar-type stars is
generally referred to as the ``Brown Dwarf Desert''. Here we report the
detection of a companion to HD 137510 (G0IV), with a minimum mass of 26
M_Jupiter, moving in an eccentric orbit (e=0.4) with a period of 798 days and
an orbital semimajor axis of 1.85 AU. The detection is based on precise
differential radial velocity (RV) data obtained by the McDonald Observatory and
Thueringer Landessternwarte Tautenburg planet search programs.


title: Neutrinoless Universe

abstract:
  We consider the consequences for the relic neutrino abundance if extra
neutrino interactions are allowed, e.g., the coupling of neutrinos to a light
(compared to $m_\nu$) boson. For a wide range of couplings not excluded by
other considerations, the relic neutrinos would annihilate to bosons at late
times, and thus make a negligible contribution to the matter density today.
This mechanism evades the neutrino mass limits arising from large scale
structure.


title:
XMM-Newton observations of M31: X-ray properties of radio sources and
  SNR candidates

abstract:
  We present the results of the ongoing XMM-Newton survey of M31. 17 X-ray
sources detected in the survey have bright radio counterparts, and 15 X-ray
sources coincide with SNR candidates from optical and radio surveys. 15 out of
17 sources with radio counterparts, not SNR candidates, have spectral
properties similar to that observed for background radio galaxies/quasars or
Crab-like supernova remnants located in M31. The remaining two sources, XMMU
J004046.8+405525 and XMMU J004249.1+412407, have soft X-ray spectra, and are
associated with spatially resolved H-alpha emission regions, which makes them
two new SNR candidates in M31. The observed absorbed X-ray luminosities of SNR
candidates in our sample range from 1e35 to 5e36 ergs/s, assuming the distance
of 760 kpc. Most of the SNR candidates detected in our survey have soft X-ray
spectra. The spectra of the brightest sources show presence of emission lines
and can be fit by thermal plasma models with kT~0.1-0.4 keV. The results of
spectral fitting of SNR candidates suggest that most of them should be located
in a relatively low density regions. We show that X-ray color-color diagrams
can be useful tool for distinguishing between intrinsically hard background
radio sources and Crab-like SNR and thermal SNR in M31 with soft spectra.


title:
The Properties of Satellite Galaxies in External Systems. II. Photometry
  and Colors

abstract:
  In this second paper dedicated to the study of satellite galaxies we present
broad-band photometry in the B, V, R and I filters of 49 satellite galaxies
orbiting giant isolated spiral galaxies. First analysis of the properties of
these objects are presented by means of color--color and color--magnitude
diagrams for early- and late-type satellites. Although we find differences in
the slope of the V-I vs. Mv color magnitude diagram, as a whole, the relations
are in agreement with the trends known to date for galaxies of similar
magnitudes in nearby clusters of galaxies. Comparison with the relations found
for satellites in the Local Group allows us to sample better the bright end of
the luminosity function of satellite galaxies and extends for brighter objects
the validity of the color--magnitude relation found for dwarf galaxies in the
Local Group. Most of the E/S0 galaxies in our sample show a negative color
gradient with values similar to those known for early type galaxies in other
environments.


title:
Prompt Gamma-ray and Early Afterglow Emission in the External Shock
  Model

abstract:
  We describe our attempt to determine if gamma-ray burst (GRB) and afterglow
emissions could both arise in external shocks for simple GRBs--bursts
consisting of just a few peaks in their lightcurves. We calculate peak flux and
peak frequency during the gamma-ray burst for ten well observed bursts using
the same set of parameters that are determined from modeling afterglow
emissions. We find the gamma-ray emission properties for 970508 (which had a
single peak lightcurve) fit nicely with the extrapolation of its afterglow
data, and therefore this burst was likely produced in the external shock. One
can explain two other bursts in this sample as forward shock synchrotron
emission provided that the magnetic field parameter during the burst is close
to equipartition, and larger by a factor of 100 than the afterglow value at ~1
day. The remaining seven bursts cannot be explained in the external shock model
even if we allow the energy fraction in electrons and magnetic field and the
density of the surrounding medium to take on any physically permitted value;
the peak of the spectrum is above the cooling frequency, therefore the peak
flux is independent of the latter of these two parameters, and is too small by
about an order of magnitude than the observed values. We have also considered
inverse-Compton scattering in forward and reverse shock regions and find that
it can explain the gamma-ray emission for a few bursts, but requires the
density to be 1--2 orders of magnitude larger than a typical Wolf-Rayet star
wind and much larger than permitted by late afterglow observations. [Abridged]


title: The subhalo populations of LCDM dark haloes

abstract:
  We use a large cosmological simulation and a variety of high resolution
resimulations of individual cluster and galaxy haloes to study the systematics
of subhalo populations over ranges of 1000 in halo mass and 1000 in the ratio
of subhalo to parent halo mass. The subhalo populations of different haloes are
not scaled copies of each other, but vary systematically with halo properties.
On average, the amount of substructure increases with halo mass. At fixed mass,
it decreases with halo concentration and with halo formation redshift. These
trends are comparable in size to the scatter in subhalo abundance between
similar haloes. Averaged over all haloes of given mass, the abundance of low
mass subhaloes per unit parent halo mass is independendent of parent mass.It is
very similar to the abundance per unit mass of low mass haloes in the universe
as a whole, once differing boundary definitions for subhaloes and haloes are
accounted for. The radial distribution of subhaloes within their parent haloes
is substantially less centrally concentrated than that of the dark matter. It
varies at most weakly with the mass(or concentration) of the parent halo and
not at all with subhalo mass. It does depend on the criteria used to define the
subhalo population considered. About 90% of present-day subhaloes were accreted
after z=1 and about 70% after z=0.5. Only about 8% the total mass of all haloes
accreted at z=1 survives as bound subhaloes at z=0. For haloes accreted at z=2,
the survival mass fraction is just 2%. Subhaloes seen near the centre of their
parent typically were accreted earlier and retain less of their original mass
than those seen near the edge. These strong systematics mean that comparison
with galaxies in real clusters is only possible if the formation of the
luminous component is modelled appropriately.


title:
Disk Temperature Variations and Effects on the Snow Line in the Presence
  of Small Protoplanets

abstract:
  We revisit the computation of a "snow line" in a passive protoplanetary disk
during the stage of planetesimal formation. We examine how shadowing and
illumination in the vicinity of a planet affects where in the disk ice can
form, making use of our method for calculating radiative transfer on disk
perturbations with some improvements on the model. We adopt a model for the
unperturbed disk structure that is more consistent with observations and use
opacities for reprocessed dust instead of interstellar medium dust. We use the
improved disk model to calculate the temperature variation for a range of
planet masses and distances and find that planets at the gap-opening threshold
can induce temperature variations of up to +/-30%. Temperature variations this
significant may have ramifications for planetary accretion rates and migration
rates. We discuss in particular the effect of temperature variations near the
sublimation point of water, since the formation of ice can enhance the
accretion rate of disk material onto a planet. Shadowing effects can cool the
disk enough that ice will form closer to the star than previously expected,
effectively moving the snow line inward.


title: Cosmic acceleration, scalar fields and observations

abstract:
  Conditions for accelerated expansion of Friedmann-Robertson-Walker space-time
are analyzed. Connection of this scenario with present-day observations are
reviewed. It is explained how a scalar field could be responsible for cosmic
acceleration observed in present times and predicted for the very early
Universe. Ideas aimed at answering whether is that the actual case for our
Universe are described.


title:
The Identification of Blue Horizontal Branch Stars in the Integrated
  Spectra of Globular Clusters

abstract:
  A major uncertainty in the spectroscopic dating of extragalactic globular
clusters concerns the degenerate effect that age and horizontal branch
morphology have on the strength of Balmer lines. In this Letter we show that
the ratio between the equivalent widths of Hdelta and Hbeta is far more
sensitive to horizontal branch morphology than to age, thus making it possible
to break the degeneracy. We show that it is possible to distinguish
intermediate-age globular clusters from those whose Balmer lines are
strengthened by the presence of blue horizontal branch stars, purely on the
basis of the clusters' integrated spectra. The degeneracy between age and
horizontal branch morphology can be lifted with Hbeta and Hdelta line strengths
from spectra with S/N >= 30 per Angstrom, which is typical of current studies
of integrated spectroscopy of extragalactic globular clusters.


title: Fe II Diagnostic Tools for Quasars

abstract:
  The enrichment of Fe, relative to alpha-elements such as O and Mg, represents
a potential means to determine the age of quasars and probe the galaxy
formation epoch.
  To explore how \ion{Fe}{2} emission in quasars is linked to physical
conditions and abundance, we have constructed a 830-level \ion{Fe}{2} model
atom and investigated through photoionization calculations how \ion{Fe}{2}
emission strengths depend on non-abundance factors. We have split \ion{Fe}{2}
emission into three major wavelength bands, \ion{Fe}{2} (UV),
\ion{Fe}{2}(Opt1), and \ion{Fe}{2}(Opt2), and explore how the
\ion{Fe}{2}(UV)/\ion{Mg}{2}, \ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt1) and
\ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt2) emission ratios depend upon hydrogen density
and ionizing flux in broad-line regions (BLR's) of quasars. Our calculations
show that: 1) similar \ion{Fe}{2}(UV)/\ion{Mg}{2} ratios can exist over a wide
range of physical conditions; 2) the \ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt1) and
\ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt2) ratios serve to constrain ionizing luminosity
and hydrogen density; and 3) flux measurements of \ion{Fe}{2} bands and
knowledge of ionizing flux provide tools to derive distances to BLR's in
quasars. To derive all BLR physical parameters with uncertainties, comparisons
of our model with observations of a large quasar sample at low redshift ($z<1$)
is desirable.
  The STIS and NICMOS spectrographs aboard the Hubble Space Telescope (HST)
offer the best means to provide such observations.


title: Gamma-Ray Line Observations with RHESSI

abstract:
  The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been
observing gamma-ray lines from the Sun and the Galaxy since its launch in
February 2002. Here I summarize the status of RHESSI observations of solar
lines (nuclear de-excitation, neutron capture, and positron annihilation), the
lines of $^{26}$Al and $^{60}$Fe from the inner Galaxy, and the search for
positron annihilation in novae.


title: 'TeV Gamma-ray Crisis' and an Anisotropic Space Model

abstract:
  To solve the `TeV gamma crisis', we examine a model whose one spatial
direction is discretized at a high energy scale. Assuming the standard
extra-galactic IR photon distribution, we evaluate the mean free-path of a
energetic photon which acquires an effective mass in the model. For a wide
range of the value of the lattice energy scale between a few TeV and around
$10^{10}$ GeV, the mean free-path of a TeV energy photon can be enlarged enough
to solve the `crisis'. Taking into account the effects of the universe
expansion, we find bounds of the lattice constant.


title:
From BeppoSAX to INTEGRAL: PDS observations of hard X-ray sources
  detected in the IBIS survey

abstract:
  The first IBIS galactic plane survey has provided a list of high energy
emitting objects above 20 keV; these sources have been detected mostly in the
crowded region of the Galactic Centre and partly along the Galactic Plane. In
order to validate the detection procedure, to help in the identification
process and to study the nature of these IBIS sources, this list has been cross
correlated with the data archive of the PDS instrument on BeppoSAX, which
operated in a similar energy band and with a similar sensitivity. We discover a
number of associations whose detailed analysis will be particularly useful for
the survey work. Also, thanks to the imaging capability of IBIS/ISGRI, objects
which could not be studied by the PDS due to contamination from nearby sources
can now be associated with a definite source or sources.


title: Interacting clusters and their environment

abstract:
  Central regions of superclusters are the ideal places where to study cluster
merging phenomena: in fact the accretion activity is enhanced, as predicted by
the cosmological simulations. In this paper I review the case-study of the
Shapley Concentration, aimed to understand the effect of major mergings on the
intracluster medium and the galaxy population of the involved clusters.


title: Radio activity in major mergings

abstract:
  Cluster mergings are expected to have an influence on the radio emission of
the galaxy population. We present the results of a deep radio survey in the
A3558 complex in the central region of the Shapley Concentration, in order to
further explore our hypothesis of a dependence of the radio luminosity function
on the age of the merging.


title:
Constraints on perfect fluid and scalar field dark energy models from
  future redshift surveys

abstract:
  We discuss the constraints that future photometric and spectroscopic redshift
surveys can put on dark energy through the baryon oscillations of the power
spectrum. We model the dark energy either with a perfect fluid or a scalar
field and take into account the information contained in the linear growth
function. We show that the growth function helps to break the degeneracy in the
dark energy parameters and reduce the errors on $w_0,w_1$ roughly by 30% making
more appealing multicolor surveys based on photometric redshifts. We find that
a 200 square degrees spectroscopic survey reaching $z = 3$ can constrain
$w_0,w_1$ to within $\Delta w_0=0.21,\Delta w_1=0.26$ and to $\Delta
w_0=0.39,\Delta w_1=0.54$ using photometric redshifts with absolute uncertainty
of 0.02. In the scalar field case we show that the slope $n$ of the inverse
power-law potential for dark energy can be constrained to $\Delta n=0.26$
(spectroscopic redshifts) or $\Delta n=0.40$ (photometric redshifts), i.e.
better than with future ground-based supernovae surveys or CMB data.


title:
Inferring the dark matter power spectrum from the Lyman-alpha forest in
  high-resolution QSO absorption spectra

abstract:
  We use the LUQAS sample (Kim et al. 2004), a set of 27 high-resolution and
high signal-to-noise QSO absorption spectra at a median redshift of z=2.25, and
the data from Croft et al. (2002) at a median redshift of z=2.72, together with
a large suite of high-resolution large box-size hydro-dynamical simulations, to
estimate the linear dark matter power spectrum on scales 0.003 s/km < k <0.03
s/km. Our re-analysis of the Croft et al. data agrees well with their results
if we assume the same mean optical depth and gas temperature-density relation.
The inferred linear dark matter power spectrum at z=2.72 also agrees with that
inferred from LUQAS at lower redshift if we assume that the increase of the
amplitude is due to gravitational growth between these redshifts. We further
argue that the smaller mean optical depth measured from high-resolution spectra
is more accurate than the larger value obtained from low-resolution spectra by
Press et al. (1993) which Croft et al. used. For the smaller optical depth we
obtain a ~ 20% higher value for the rms fluctuation amplitude of the matter
density. By combining the amplitude of the matter power spectrum inferred from
the Lyman-alpha forest with the amplitude on large scales inferred from
measurements of the CMB we obtain constraints on the primordial spectral index
n and the normalisation sigma_8. For values of the mean optical depth favoured
by high-resolution spectra, the inferred linear power spectrum is consistent
with a LambdaCDM model with a scale-free (n=1) primordial power spectrum.


title: A Possible Origin of Dark Energy

abstract:
  We discuss the possibility that the existence of dark energy may be due to
the presence of a spin zero field $\phi(x)$, either elementary or composite. In
the presence of other matter field, the transformation $\phi(x)\to \phi(x) +$
constant can generate a negative pressure, like the cosmological constant. In
this picture, our universe can be thought as a very large bag, similar to the
much smaller MIT bag model for a single nucleon.


title:
X-raying Abell 2125 -- a Large-scale Hierarchical Complex of Galaxies
  and Hot Gas

abstract:
  We present an 82 ksec Chandra ACIS-I observation of a large-scale
hierarchical complex, which consists of various clusters/groups of galaxies and
low-surface brightness X-ray emission at z = 0.247. This high-resolution {\sl
Chandra} observation allows us for the first time to separate unambiguously the
X-ray contributions from discrete sources and large-scale diffuse hot gas. We
detect 99 X-ray sources in a $17^\prime \times 17^\prime$ field. Ten of these
sources are identified as members of the complex and are mostly radio-bright.
Whereas unresolved X-ray sources tend to be associated with galaxies in
intermediate density environments, extended X-ray emission peak at bright radio
galaxies in the central cluster. In particular, a distinct X-ray trail appears
on one side of the fast-moving galaxy C153, clearly due to ram-pressure
stripping. The diffuse X-ray emission from the central cluster can be
characterized by a thermal plasma with a characteristic temperature of
$3.2_{-0.4}^{+0.5}$ keV and a heavy element abundance of $0.24_{-0.12}^{+0.15}$
solar (90% confidence uncertainties). In comparison, a patch of low-surface
brightness X-ray emission apparently originates in relatively low density
intergalactic gas with a characteristic temperature of $0.98_{-0.27}^{+0.22}$
keV and an abundance of $\lesssim 0.09$ solar. The Chandra observation,
together with extensive multi-wavelength data, indicates that the complex
represents a projection of several galaxy sub-structures, which may be
undergoing major mergers. We discuss the dynamic states of the complex and its
sub-structures as well as properties of X-ray-emitting galaxies and the
relationship to their environments.


title:
A look with BeppoSAX at the low-luminosity Galactic X-ray source 4U
  2206+54

abstract:
  A pointed observation of the low-luminosity galactic source 4U 2206+54 was
carried out in November 1998 with BeppoSAX. The light curve of 4U 2206+54 shows
erratic variability on a timescale of about 1 hour; neither hardness variations
nor time periodicities are detected throughout this 67 ks long observation.
Thanks to the wide spectral coverage capabilities of BeppoSAX we could observe
the source X-ray continuum over three energy decades, from 0.6 to 60 keV. The
spectrum could be equally well fitted either with a blackbody plus
Comptonization or with a high energy cutoff power law. No iron emission around
6.5 keV was detected, while a tentative detection of a cyclotron resonant
feature in absorption is presented. Comparison of the present BeppoSAX data
with the information available in the literature for this source suggests that
4U 2206+54 is a close binary system in which a (possibly magnetized) NS is
accreting from the companion star wind.


title: Chandra and XMM-Newton Observations of the Double Cluster Abell 1758

abstract:
  Abell 1758 was classified as a single rich cluster of galaxies by Abell, but
a ROSAT observation showed that this system consists of two distinct clusters
(A1758N and A1758S) separated by approximately $8\arcmin$ (a projected
separation of 2 Mpc in the rest frame of the clusters). Only a few galaxy
redshifts have been published for these two clusters, but the redshift of the
Fe lines in the Chandra and XMM-Newton spectra shows that the recessional
velocities of A1758N and A1758S are within 2,100 km s$^{-1}$. Thus, these two
clusters most likely form a gravitationally bound system, but our imaging and
spectroscopic analyses of the X-ray data do not reveal any sign of interaction
between the two clusters. The Chandra and XMM-Newton observations show that
A1758N and A1758S are both undergoing major mergers.
  A1758N is in the late stages of a large impact parameter merger between two 7
keV clusters. The two remnant cores have a projected separation of 800 kpc.
Based on the measured pressure jumps preceding the two cores, they are receding
from one another at less than 1,600 km s$^{-1}$. The two cores are surrounded
by hotter gas ($\mathrm{kT}=9$--12 keV) that was probably shock heated during
the early stages of the merger. The gas entropy in the two remnant cores is
comparable with the central entropy observed in dynamically relaxed clusters,
indicating that the merger-induced shocks stalled as they tried to penetrate
the high pressure cores of the two merging systems.Each core also has a wake of
low entropy gas indicating that this gas was ram pressure stripped without
being strongly shocked (abridged). (A copy of the paper with higher resolution
images is available at http://asc.harvard.edu/~lpd/a1758.ps).


title: LSI+61303 in the context of microquasars

abstract:
  LSI+61303 is one of the most observed Be/X-ray binary systems because,
peculiarly, it has periodical radio and X-ray emission together with strong,
variable gamma-ray emission. This source remains, however, quite enigmatic.
Some properties of this system can be explained assuming that the unseen
companion is a non-accreting young pulsar with a relativistic wind strongly
interacting with the wind of the Be star. On the contrary, other properties of
LSI+61303 fit a model where the companion is accreting even with two events of
super-critical accretion along the orbit. The very recent discovery of a radio
jet extending ca. 200 AU at both sides of a central core has definitely proved
the occurrence of accretion--ejection processes in this system. Therefore it is
of great interest to combine this result with previous observations at other
wavelengths within the framework of the two-peak accretion (ejection) model.
Concerning the first ejection, we show that the observed gamma-rays variations
might be periodic with outbursts confined around the periastron passage (i.e.
where the first accretion-rate peak occurs and high-energy emission but no
radio emission is predicted). Concerning the second ejection, with radio
bursts, we point out that it can be also traced in the X-ray data, both in
episodes of hardening of the X-ray emission and in a transition from soft- to
hard-states at the onsets of radiobursts. In fact, both hardening and
transitions between spectral states are related to the dramatic change in the
structure of the accretion disk preceeding the ejection. Finally, we explore
the nature of the accretor and we conclude that on the basis of the present
optical data a black hole cannot be ruled out.


title: The SEDs of the revised 200 mJy sample

abstract:
  We address the question of why low-luminosity radio sources with similar flat
radio spectra show a range of optical activity. The investigation is based on
the spectral energy distributions (SEDs) of objects from the 200 mJy sample. We
gathered new data from the VLA at 43 GHz, from SCUBA in the JCMT at 2000, 1350
and 850 micron and from the ISOPHOT instrument on ISO at 170, 90, 60 and 25
micron. There is considerable diversity amongst the SEDs of the objects: there
are objects with steep broadband spectra between centimetre and millimetre
bands (14% of the sample), there are those with flat broadband spectra over
most of the spectral range (48% of the sample) and there are those which show
pronounced sub-mm/infrared excesses (27% of the sample). Some objects of the
first group have two sided radio morphology indicating that their pc-scale
emission is not dominated by beamed jet emission. Amongst the objects that have
smooth broadband spectra from the radio to the infrared there are passive
elliptical galaxies as well as the expected BL Lacs objects. The most
pronounced sub-mm/infrared excesses are shown by the broad emission line
objects.


title: The effect of a meridional flow on Parker's interface dynamo

abstract:
  Parker's interface dynamo is generalized to the case when a homogeneous flow
is present in the high-diffusivity (upper) layer in the lateral direction (i.e.
perpendicular to the shear flow in the lower layer). This is probably a
realistic first representation of the situation near the bottom of the solar
convective zone, as the strongly subadiabatic stratification of the tachocline
(lower layer in the interface dynamo) imposes a strong upper limit on the speed
of any meridional flow there.
  Analytic solutions to the eigenvalue problem are presented for the cases of
vanishing diffusivity contrast and infinite diffusivity contrast, respectively.
Unlike the trivial case of a homogeneous system, the ability of the meridional
flow to reverse the propagation of the dynamo wave is strongly reduced in the
interface dynamo. In particular, in the limit of high diffusivity contrast
relevant to the solar case it is found that a meridional flow of realistic
amplitude cannot reverse the direction of propagation of the dynamo wave. The
implications of this result for the solar dynamo problem are discussed.


title: The Collapsar and Supranova Models

abstract:
  This rapporteur review summarizes results presented in Parallel Session GBT2
(Gamma Ray Burst Theory 2) on the Collapsar and Supranova Models held 25 July
2003 at the 10th Marcel Grossmann Meeting on General Relativity, Rio de
Janeiro, Brazil. A central issue in GRB studies is the process whereby energy
is released from the GRB engine. One scenario is the collapsar model, where the
evolved stellar core promptly collapses to a black hole surrounded by a
massive, intermittently-accreting torus of nuclear density material. A second
scenario is the supranova model, where the first step of a two-step collapse
process leaves behind a rapidly rotating neutron star stabilized by rotation,
which later collapses to a black hole while making the GRB. In the supranova
model, a powerful pulsar wind lasting days to weeks after the supernova makes
distinctive signatures from the heating of the supernova remnant (SNR) shell,
which should be discovered with Swift. This model also predicts nonstandard
reddened excesses from the cooling SNR due to the range of delays between the
two collapse events, contrary to observations of SN emissions from low redshift
GRBs which favor the collapsar model. The observational basis for both models
is critically reviewed. An outline of a GRB model is proposed where the second
collapse takes place within minutes to hours after the primary SN event, during
which time loss of centrifugal support along the rotation axis of the neutron
star provides a relatively baryon-clean polar environment along which a newly
formed, rapidly spinning black hole drives collimated baryon-dilute outflows.


title:
Double-Damped Lyman Alpha Absorption: A Possible Large Neutral Hydrogen
  Gas Filament Near Redshift z=1

abstract:
  We report the discovery of two damped Ly-alpha absorption-line systems (DLAs)
near redshift z=1 along a single quasar sightline (Q1727+5302) with neutral
hydrogen column densities of N(HI) = (1.45\pm0.15)\times10^{21} and
(2.60\pm0.20)\times10^{21} atoms/cm2. Their sightline velocity difference of
13,000 km/s corresponds to a proper separation of 106h_{70}^{-1} Mpc if
interpreted as the Hubble flow (Omega_m=0.3, Omega_Lambda=0.7). The random
probability of such an occurrence is significantly less than 3%. With follow-up
spectroscopy, we find [Zn/H] = -0.58\pm0.15 (26.5% solar) and -1.32\pm0.28
(4.7% solar), respectively, and [Cr/H] = -1.26\pm0.15 (5.5% solar) and
-1.77\pm0.28 (1.7% solar), respectively, which is evidence for depletion onto
grains. Follow-up IR images show the two most likely DLA galaxy candidates to
have impact parameters of 22h_{70}^{-1} kpc and 32h_{70}^{-1} kpc if near z=1.
They are significantly underluminous relative to the galaxy population at z=1.
To investigate the possibility of additional high-N(HI) absorbers we have
searched the SDSS database for z>1 quasars within 30 arcmin of the original
sightline. Five were found, and two show strong MgII-FeII absorption near z=1,
consistent with classical DLA absorption approx 37% of the time, but almost
always N(HI) > 10^{19} atoms/cm2. Consequently, this rare configuration of four
high-N(HI) absorbers with a total sightline velocity extent of 30,600 km/s may
represent a large filament-like structure stretching over a proper distance of
241h_{70}^{-1} Mpc along our sightline, and a region in space capable of
harboring excessive amounts of neutral gas. Future studies of this region of
the sky are encouraged.