title:
Searching for cosmic missing baryons with DIOS -- Diffuse Intergalactic
  Oxygen Surveyor --

abstract:
  Approximately 30 to 50 percent of the total baryons in the present universe
is supposed to take a form of warm/hot intergalactic medium (WHIM) whose X-ray
continuum emission is very weak. In order to carry out a direct and homogeneous
survey of elusive cosmic missing baryons, we propose a dedicated soft-X-ray
mission, {\it DIOS} (Diffuse Intergalactic Oxygen Surveyor). The unprecedented
energy resolution ($\sim 2$eV) of the XSA (X-ray Spectrometer Array) on-board
{\it DIOS} enables us to identify WHIM with gas temperature $T=10^{6-7}$K and
overdensity $\delta=10-100$ located at $z<0.3$ through emission lines of O{\sc
vii} and O{\sc viii}. {\it DIOS}, hopefully launched in several years, promises
to open a new window of detection and characterization of cosmic missing
baryons, and to provide yet another important and complementary tool to trace
the large-scale structure of the universe.


title: Interactions of Satellite Galaxies in Cosmological Dark Matter Halos

abstract:
  We present a statistical analysis of the interactions between satellite
galaxies in cosmological dark matter halos taken from fully self-consistent
high-resolution simulations of galaxy clusters. We show that the number
distribution of satellite encounters has a tail that extends to as many as 3-4
encounters per orbit. On average 30% of the substructure population had at
least one encounter (per orbit) with another satellite galaxy. However, this
result depends on the age of the dark matter host halo with a clear trend for
more interactions in younger systems. We also report a correlation between the
number of encounters and the distance of the satellites to the centre of the
cluster: satellite galaxies closer to the centre experience more interactions.
However, this can be simply explained by the radial distribution of the
substructure population and merely reflects the fact that the density of
satellites is higher in those regions.
  In order to find substructure galaxies we applied (and present) a new
technique based upon the N-body code MLAPM. This new halo finder MHF
(MLAPM's-Halo-Finder) acts with exactly the same accuracy as the N-body code
itself and is therefore free of any bias and spurious mismatch between
simulation data and halo finding precision related to numerical effects.


title: Synchrotron aging and the radio spectrum of SN 1993J

abstract:
  We combine the GMRT low frequency radio observations of SN 1993J with the VLA
high frequency radio data to get a near simultaneous spectrum around day 3200
since explosion. The low frequency measurements of the supernova determine the
turnover frequency and flux scale of the composite spectrum and help reveal a
steepening in the spectral index, $\Delta \alpha \sim 0.6$, in the optically
thin part of the spectrum. This is the first observational evidence of a break
in the radio spectrum of a young supernova. We associate this break with the
phenomenon of synchrotron aging of radiating electrons. From the break in the
spectrum we calculate the magnetic field in the shocked region independent of
the equipartition assumption between energy density of relativistic particles
and magnetic energy density. We determine the ratio of these two energy
densities and find that this ratio is in the range: $8\times 10^{-6}-5\times
10^{-4}$. We also predict the nature of the evolution of the synchrotron break
frequency with time, with competing effects due to diffusive Fermi acceleration
and adiabatic expansion of the radiative electron plasma.


title:
Magnetic Field Evolution in Neutron Star Crusts due to the Hall Effect
  and Ohmic Decay

abstract:
  We present calculations of magnetic field evolution by the Hall effect and
Ohmic decay in neutron star crusts. We first discuss when and for which neutron
stars the Hall effect is important relative to Ohmic decay. We compute the
evolution of an initial field distribution by Ohmic decay, and give approximate
analytic formulas for both the surface and interior fields as a function of
time. We then discuss the subsequent evolution by the Hall effect, giving
several examples which illustrate how the field configuration evolves. Hall
wave eigenfunctions are computed, including the effect of the large density
change across the crust. We estimate the response of the crust to the magnetic
stresses induced by Hall waves, and give a detailed discussion of the boundary
conditions at the solid-liquid interface. Finally, we discuss the implications
for the Hall cascade proposed by Goldreich & Reisenegger.


title: RATAN-600 and PLANCK Mission: new results after First General Meeting

abstract:
  We present activity at RATAN-600 connected with future PLANCK mission. It
includes special radio telescope upgrading, multi-frequencies observations in
the 0.6GHz-30GHz band with 40 channels, new results, connected with
synchrotron, spinning dust and polarized Galaxy emission at small scales. Much
lower limits were found than expected before the First Planck meeting. New deep
sub-mJy survey of the 100 sq.deg. field at cm. waves demonstrated, that NVSS
objects will dominate at LFI frequencies, and new, invisible by NVSS population
will be below PLANCK sensitivity limit with only few exceptions. Preparation to
the next generation experiments, connected with PLANCK mission we describe as
well. They include high l polarization, SZ- blind survey, and test observations
of the cosmological highly redshifted lines at small scales.


title:
The structure and radiation spectra of illuminated accretion disks in
  AGN. II. Flare/spot model of X-ray variability

abstract:
  We discuss a model of X-ray variability of active galactic nuclei (AGN). We
consider multiple spots which originate on the surface of an accretion disk
following intense irradiation by coronal flares. The spots move with the disk
around the central black hole and eventually decay while new spots continuously
emerge. We construct time sequences of the spectra of the spotted disk and
compute the corresponding energy-dependent fractional variability amplitude. We
explore the dependence on the disk inclination and other model parameters. AGN
seen at higher inclination with respect to the observer, such as Seyfert 2
galaxies, are expected to have fractional variability amplitude of the direct
emission by a factor of a few higher than objects seen face on, such as the
Seyfert 1s.


title: On the excitation of the infrared knots along protostellar jets

abstract:
  The complete near infrared (0.9-2.5 micron) spectra in three different star
forming regions (HH24-26, HH72 and BHR71) are presented and analyzed in the
framework of shock excitation models. The spectra are dominated by H_2
rovibrational emission (vibrational state nu up to 5, excitation energy T_ex up
to 35000 K), while emission from ionized material, recognizable from [Fe II]
and [S II] lines, is significantly fainter. The analysis of the H_2 excitation
diagrams points to the existence of two different excitation regimes: whilst
condensations observed only in the infrared appear to have temperatures rarely
exceeding 3000 K and can be modelled in the framework of steady-state C-shock
models, the infrared counterparts of Herbig Haro (HH) objects exhibit a
temperature stratification with components up to more than 5000 K. The H_2
emission from representative HH objects (HH26A, HH72A and HH320A) has been
successfully modelled by planar J-shocks with magnetic precursors, for which
the main parameters (pre-shock density, speed) are derived. However, these same
models are unable to reproduce the observed atomic and ionic emission, which
probably arises from a distinct and perhaps more embedded region with respect
to that traced by the H_2. Some of the physical parameters of such regions
(fractional ionization, density) have been estimated in HH72, on the basis of
the observed ionic lines.


title: Asymmetries in the local curvature of the WMAP data

abstract:
  We use the local curvature to investigate the possible existence of
non-Gaussianity/asymmetry in the WMAP data. Considering the full sky we find
results which are consistent with the Gaussian assumption. However, strong
non-Gaussian features emerge when considering the northern and southern
galactic hemisphere separately, particularly on scales between 1 and 5 degrees.
Quite interestingly, the maximum non-Gaussianity is found for hemispheres
centered near the ecliptic poles, which might suggest the presence of some
systematic effect. The direction of the asymmetry seems consistent with the
findings by Eriksen et al. 2004.


title: Multi-site, multi-technique survey of Gamma Doradus candidates

abstract:
  We present the first results of a 2-year high-resolution spectroscopy
campaign of 59 candidate Gamma Doradus stars which were mainly discovered from
the HIPPARCOS astrometric mission. More than 60 % of the stars present line
profile variations which can be interpreted as due to pulsation related to
Gamma Doradus stars. For all stars we also derived the projected rotation
velocity (up to more than 200 km\s). The amplitude ratios 2K/Delta m for the
main HIPPARCOS frequency are in the range 35 - 96 (km\s)\mag. Less than 50 % of
the candidates are possible members of binary systems, with 20 stars being
confirmed Gamma Doradus. At least 6 stars present composite spectra, and in all
but one case (for which only one spectrum could be obtained), the narrow
component shows line profile variations, pointing towards an uncomfortable
situation if this narrow component originates from a shell surrounding the
star. This paper is the first of a series concerning mode identification using
both photometric and spectroscopic methods for the confirmed Gamma Doradus
stars of the present sample.


title:
New Variable Stars in Open Clusters I: Methods and Results for 20 Open
  Clusters

abstract:
  We present high precision CCD photometry of 1791 objects in 20 open clusters
with an age from 10 Myr to 1 Gyr. These observations were performed within the
Delta a photometric system which is primarily used to detect chemically
peculiar stars of the upper main sequence. Time bases range between 30 minutes
and up to 60 days with data from several nights. We describe the way of time
series analysis reaching a detection limit of down to 0.006 mag. In total, we
have detected 35 variable objects from which four are not members of their
corresponding clusters. The variables cover the entire
Hertzsprung-Russell-diagram, hence they are interesting targets for follow-up
observations.


title: WMAP confirming the ellipticity in BOOMERanG and COBE CMB maps

abstract:
  The recent study of BOOMERanG 150 GHz Cosmic Microwave Background (CMB)
radiation maps have detected ellipticity of the temperature anisotropy spots
independent on the temperature threshold. The effect has been found for spots
up to several degrees in size, where the biases of the ellipticity estimator
and of the noise are small. To check the effect, now we have studied, with the
same algorithm and in the same sky region, the WMAP maps. We find ellipticity
of the same average value also in WMAP maps, despite of the different
sensitivity of the two experiments to low multipoles. Large spot elongations
had been detected also for the COBE-DMR maps. If this effect is due to geodesic
mixing and hence due to non precisely zero curvature of the hyperbolic
Universe, it can be linked to the origin of WMAP low multipoles anomaly.


title:
The variable star population in Phoenix: coexistence of Anomalous and
  short-period Classical Cepheids, and detection of RR Lyrae variables

abstract:
  We present the results of a search for variable stars in the Local Group
dwarf galaxy Phoenix. Nineteen Cepheids, six candidate long-period variables,
one candidate eclipsing binary and a large number of candidate RR Lyrae stars
have been identified. Periods and light curves have been obtained for all the
Cepheid variables. Their distribution in the period-luminosity diagram reveals
that both Anomalous Cepheids (AC) and short-period Classical Cepheids s-pCC are
found in our sample. This is the first time that both types of variable star
are identified in the same system even though they likely coexist, but have
gone unnoticed so far, in other low-metallicity galaxies like Leo A and Sextans
A. We argue that the conditions for the existence of both types of variable
star in the same galaxy are a low metallicity at all ages, and the presence of
both young and intermediate-age (or old, depending on the nature of AC) stars.
The RR Lyrae candidates trace, together with the well developed horizontal
branch, the existence of an important old population in Phoenix. The different
spatial distributions of s-pCC, AC and RR Lyrae variables in the Phoenix field
are consistent with the stellar population gradients found in Phoenix, in the
sense that the younger population is concentrated in the central part of the
galaxy. The gradients in the distribution of the young population within the
central part of Phoenix, which seem to indicate a propagation of the recent
star formation, are also reflected in the spatial distribution of the s-pCC.


title: The galaxy population of intermediate-redshift clusters

abstract:
  Using photometric redshifts we determine the galaxy population of the
clusters of galaxies Cl0016+16 at z=0.55, Cl1600+41 at z=0.54, Cl1601+42 at
z=0.54 and MS1008-1224 at z=0.31. Comparing the clusters, we find no evidence
for a universal shape of the total luminosity function (LF) at these redshifts.
When dividing the LFs into spectral types, we find that the LF of the
early-type galaxies alone can be described by a Gaussian, while the LF of the
late-type galaxies is well fitted by a Schechter function, suggesting that the
separate LFs for different populations may be universal. The difference in the
total LFs can mainly be attributed to the varying relative normalisation of
these populations, implying that clusters with an abundant population of
late-type galaxies also have steeper faint-end slopes. In MS1008-1224 we detect
a faint blue population that dominates over a population with colours
consistent with dwarf ellipticals, opposite to clusters at lower redshift.
Compared to low redshift clusters, we find that a general fading of the
late-type population by ~2 mag and the early-type population by ~1 mag
describes the evolution from z=0.55 to z=0 well. As a consequence of the
different early-type and late-type LFs and their dependence on cluster radius,
the fraction of blue cluster galaxies, as measured by the Butcher-Oemler
effect, differs between the clusters and depends on limiting magnitude and
radius. We find a correlation between the dwarf-to-giant ratio and the surface
density, indicating that the high density environment in the cluster cores is
hostile to dwarf galaxies.


title:
Volume Phase Holographic Gratings: Polarization Properties and
  Diffraction Efficiency

abstract:
  We discuss the polarization properties and first-order diffraction
efficiencies of volume phase holographic (VPH) transmission gratings, which can
be exploited to improve the throughput of modern spectrographs. The wavelength
of peak efficiency can be tuned by adjustment of the incidence angle. We show
that the variation of the Kogelnik efficiency versus Bragg angle depends only
on one parameter, given by $P_{tune} = (\Delta n d)/(n \Lambda)$, where:
$\Delta n$ is semi-amplitude of the refractive index modulation; $n$ is the
average index; $d$ is the thickness of the active layer; and $\Lambda$ is the
grating period. The efficiency has a well defined dependence on polarization.
In particular, it is possible to obtain theoretical 100% diffraction efficiency
with one linear polarization at any angle or to obtain 100% efficiency with
unpolarized light at specific angles. In the latter case, high efficiency is
the result of aligning the peaks of the s- and p-polarization
efficiency-versus-thickness curves. The first of these `s-p-phased gratings'
for astronomy is in use with the 6dF spectrograph. Consideration of
polarization is particularly important for high spectral resolution, which
requires large incidence angles. We also discuss the possibility of separating
polarization states for improved throughput along the entire optical train of a
spectrograph.


title: Electrodynamics of black hole magnetospheres

abstract:
  Numerical simulations combined with simple analytical arguments are used to
reach a number of important conclusions on the nature of the Blandford-Znajek
mechanism. We show that, just like in the Penrose mechanism and in the MHD
models of Punsly and Coroniti, the key role in this mechanism is played by the
black hole ergosphere. The poloidal currents are driven by the gravitationally
induced electric field which cannot be screened within the ergosphere by any
static distribution of the electric charge of locally created pair plasma.
Contrary to what is expected in the Membrane paradigm, the energy and angular
momentum are extracted not only along the magnetic field lines penetrating the
event horizon but along all field lines penetrating the ergosphere. In dipolar
magnetic configurations symmetric relative to the equatorial plane the
force-free approximation breaks down within the ergosphere where a strong
current sheet develops along the equatorial plane. This current sheet supplies
energy and angular momentum at infinity to the surrounding force-free
magnetosphere. The Blandford-Znajek monopole solution is found to be
asymptotically stable and causal. The so-called horizon boundary condition of
Znajek is shown to be a regularity condition at fast critical surface.


title:
Quark deconfinement and implications for the radius and the limiting
  mass of compact stars

abstract:
  We study the consequences of the hadron-quark deconfinement phase transition
in stellar compact objects when finite size effects between the deconfined
quark phase and the hadronic phase are taken into account. We show that above a
threshold value of the central pressure (gravitational mass) a neutron star is
metastable to the decay (conversion) to a hybrid neutron star or to a strange
star. The "mean-life time" of the metastable configuration dramatically depends
on the value of the stellar central pressure. We explore the consequences of
the metastability of ``massive'' neutron stars and of the existence of stable
compact quark stars (hybrid neutron stars or strange stars) on the concept of
limiting mass of compact stars. We discuss the implications of our scenario on
the interpretation of the stellar mass and radius extracted from the spectra of
several X-ray compact sources. Finally, we show that our scenario implies, as a
natural consequence a two step-process which is able to explain the inferred
``delayed'' connection between supernova explosions and GRBs, giving also the
correct energy to power GRBs.


title:
The origin and implications of dark matter anisotropic cosmic infall on
  ~L* haloes

abstract:
  We measure the anisotropy of dark matter flows on small scales in the near
environment of haloes using a large set of simulations. We rely on two
different approaches to quantify the anisotropy of the cosmic infall: we
measure the flows at the haloes' virial radius while describing the infalling
matter via fluxes through a spherical shell; we measure the spatial and
kinematical distributions of satellites and substructures around haloes
detected by the subclump finder ADAPTAHOP first described in the appendix. The
two methods are found to be in agreement both qualitatively and quantitatively
via one and two points statistics.The infall takes place preferentially in the
plane perpendicular to the direction defined by the halo's spin. We computed
the excess of equatorial accretion both through rings and via a harmonic
expansion of the infall. The level of anisotropy of infalling matter is found
to be ~15 %. The substructures have their spin orthogonal to their velocity
vector in the halo's rest frame at a level of about 5%, suggestive of an image
of a flow along filamentary structures which provides an explanation for the
measured anisotropy. We conclude that a halo does not see its environment as an
isotropic perturbation, investigate how the anisotropy is propagated inwards
using perturbation theory, and discuss briefly implications for weak lensing,
warps and the thickness of galactic disks.


title:
The European Large Area ISO Survey (ELAIS): Optical Identifications of
  15 micron and 1.4 GHz sources in N1 and N2

abstract:
  We present the optical identification of mid-IR and radio sources detected in
the European Large Area ISO Survey (ELAIS) areas N1 and N2. Using the r' band
optical data from the Wide Field Survey we apply a likelihood ratio method to
search for the counterparts of the 1056 and 691 sources detected at 15 micron
and 1.4 GHz respectively, down to flux limits of S_{15}=0.5 mJy and S_{1.4
GHz}=0.135 mJy. We find that ~92% of the 15 micron ELAIS sources have an
optical counterpart down to the magnitude limit of the optical data, r'=24. All
mid-IR sources with fluxes S_{15} >= 3 mJy have an optical counterpart. The
magnitude distribution of the sources shows a well defined peak at relatively
bright magnitudes r'~18. About 20% of the identified sources show a point-like
morphology; its magnitude distribution has a peak at fainter magnitudes than
those of galaxies. The mid-IR-to-optical and radio-to-optical flux diagrams are
presented and discussed in terms of actual galaxy models. Objects with
mid-IR-to-optical fluxes larger than 1000 are found that can only be explained
as highly obscured star forming galaxies or AGNs. Blank fields being 8% of the
15 micron sample have even larger ratios suggesting that they may be associated
with higher redshift and higher obscured objects.


title:
A brief review of long-term X-ray and optical variability in radio-quiet
  AGN

abstract:
  Long-time-scale X-ray and optical variability is a key characteristic of AGN.
Here, we summarise our current understanding of the X-ray and optical continuum
variability of radio-quiet AGN and the relation between the two bands. We
demonstrate the strong connection between the X-ray variability properties of
AGN and the variability of stellar-mass black hole candidates on much shorter
time-scales, and discuss the implications of this result for the origins of the
variability. The relationship between optical and X-ray variability is complex,
with some AGN showing strong X-ray/optical correlations while others show no
obvious correlation. We suggest a possible explanation for this variety of
behaviour.


title: The Distance and Interstellar Sight Line to GX339-4

abstract:
  The distance to the black hole binary GX339-4 remains a topic of debate. We
examine high-resolution optical spectra of the NaD lines resolving the velocity
structure along the line of sight. We find this to be complex, with at least
nine components, mostly blue-shifted, spanning a velocity range of nearly
200km/s. The presence of components with a large blue-shift rules out a nearby
location and requires that the binary be located at or beyond the tangent
point, implying a lower limit to the distance of ~6kpc. The presence of a
significant red-shifted component at +30km/s is even more intriguing as GX339-4
also has a slightly positive systemic velocity, suggesting that the source, and
this cloud, could be on the far side of the Galaxy, where the radial velocities
due to Galactic rotation become positive again. If this is the case, we require
a distance of ~15kpc. This is less secure than the 6kpc lower limit however. We
discuss the implications of these possible distances for the outburst and
quiescent luminosities, and the nature of the companion star, and argue that a
large distance is consistent with these characteristics. In particular, it
would explain the non-detection of the companion star during the faintest
states.


title: Monte Carlo Photoionization Simulations of Diffuse Ionized Gas

abstract:
  We demonstrate that the observed increase of some nebular line ratios with
height above the midplane in the diffuse ionized gas (DIG) in the Milky Way and
other galaxies is a natural consequence of the progressive hardening of the
radiation field far from the midplane ionizing sources. To obtain increasing
temperatures and line ratios away from the midplane, our photoionization
simulations of a multi-component interstellar medium do not require as much
additional heating (over and above that from photoionization) as previous
studies that employed one dimensional, spherically averaged models.
  Radiation leaking into the DIG from density bounded H II regions is generally
harder in the H-ionizing continuum and has its He-ionizing photons suppressed
compared to the ionizing source of the H II region. In line with other recent
investigations, we find that such leaky H II region models can provide elevated
temperatures and line ratios, and a lower He+ fraction in the DIG. For a
composite model representing the relative spectral types of O stars in the
solar neighbourhood, we find that additional heating less than 1.0E-26 n_e
ergs/s/cm^3 can reproduce the observed elevated line ratios in the DIG. This
additional heating is considerably less than previous estimates due to the
natural hardening of the radiation field reaching large heights in our
simulations.


title:
Disruption of a Dwarf Galaxy Under Strong Shocking: The Origin of omega
  Centauri

abstract:
  We perform N-body simulations of the dynamical evolution of a dwarf galaxy
falling into the Milky Way galaxy in order to understand the formation scenario
of the peculiar globular cluster $\omega$ Centauri. We use self-consistent
models of the bulge and the disc of the Milky Way, as well as of the dwarf
galaxy, and explore a range of dwarf models with different density
distributions. Namely, we use King (1966) and Hernquist (1990) density profiles
to model the density distribution in the dwarf. The central region of our King
model has a density profile approximately $\propto r^{-2}$, while that of the
Hernquist model is $\propto r^{-1}$. The difference in the dwarf's density
distributions leads to distinct evolutionary scenarios. The King model dwarf
loses its mass exponentially as a function of apocentric distance, with the
mass-loss rate depending on the initial mass and size of the dwarf. Regardless
of the initial mass and size, the King model dwarf remains more massive than
$10^8$ \msun after a few Gyr of evolution. The Hernquist model dwarf
experiences an accelerated mass loss, and the mass of the remnant falls below
$10^8$ \msun within a few Gyr. By exploring an appropriate set of parameters,
we find a Hernquist model that can attain the mass and orbital characteristics
of $\omega$ Cen after a few Gyr.


title:
The Southern Proper Motion Program III. A Near-Complete Catalog to
  V=17.5

abstract:
  We present the third installment of the Yale/San Juan Southern Proper Motion
Catalog, SPM3. Absolute proper motions, positions, and photographic B,V
photometry are given for roughly 10.7 million objects, primarily stars, down to
a magnitude of V=17.5. The Catalog covers an irregular area of 3700 square
degrees, between the declinations of -20 and -45 degrees, excluding the
Galactic plane. The proper-motion precision, for well-measured stars, is
estimated to be 4.0 mas/yr. Unlike previous releases of the SPM Catalog, the
proper motions are on the International Celestial Reference System by way of
Hipparcos Catalog stars, and have an estimated systematic uncertainty of 0.4
mas/yr. The SPM3 Catalog is available via electronic
transfer,(http://www.astro.yale.edu/astrom/) As an example of the potential of
the SPM3 proper motions, we examine the Galactocentric velocities of a group of
metal-poor, main-sequence A stars. The majority of these exhibit thick-disk
kinematics, lending support to their interpretation as thick-disk blue
stragglers, as opposed to being an accreted component.


title:
A phase-resolved XMM-Newton Campaign on the Colliding Wind Binary HD
  152248

abstract:
  We report the first results of an XMM-Newton monitoring campaign of the NGC
6231 open cluster in the Sco OB1 association. This first paper focuses on the
massive colliding wind binary HD 152248, which is the brightest X-ray source of
the cluster. The campaign, with a total duration of 180 ksec, was split into
six separate observations, following the orbital motion of HD 152248. The X-ray
flux from this system presents a clear, asymmetric modulation with the phase
and ranges from 0.73 to 1.18 10-12 erg s-1 cm-2 in the [0.5-10.0 keV] energy
band. The maximum of the emission is reached slightly after apastron. The EPIC
spectra are quite soft and peak around 0.8-0.9 keV. We characterize their shape
using several combinations of mekal models and power-law spectra and we detect
significant spectral variability in the [0.5-2.5 keV] energy band. We also
perform 2-D hydrodynamical simulations using different sets of parameters that
closely reproduce the physical and orbital configuration of the HD 152248
system at the time of the six XMM-Newton pointings. This allows a direct
confrontation of the model predictions with the constraints deduced from the
X-ray observations of the system. We show that the observed variation of the
flux can be explained by a variation of the X-ray emission from the colliding
wind zone, diluted by the softer X-ray contribution of the two O-type stars of
the system. Our simulations also reveal that the interaction region of HD
152248 should be highly unstable, giving rise to shells of dense gas that are
separated by low density regions. Finally, we perform a search for short-term
variability in the light curves of the system and we show that trends are
present within several of the 30 ksec exposures of our campaign. Further, most
of these trends are in good .


title: Instant preheating mechanism and UHECR

abstract:
  Top-down models assume that the still unexplained Ultra High Energy Cosmic
Rays (UHECR's) are the decay products of superheavy particles. Such particles
may have been produced by one of the post-inflationary reheating mechanisms and
may account for a fraction of the cold dark matter. In this paper, we assess
the phenomenological applicability of the simplest instant preheating framework
not to describe a reheating process, but as a mechanism to generate relic
supermassive particles as possible sources of UHECR's. We use cosmic ray flux
and cold dark matter observational data to constrain the parameters of the
model.


title: RXTE all-sky slew survey. Catalog of X-ray sources at |b|>10deg

abstract:
  We report results of a serendipitous hard X-ray (3--20 keV), nearly all-sky
(|b|>10deg) survey based on RXTE/PCA observations performed during satellite
reorientations in 1996--2002. The survey is 80% (90%) complete to a 4$\sigma$
limiting flux of ~1.8 (2.5) e-11 erg/s/cm2 in the 3--20 keV band. The achieved
sensitivity in the 3--8 keV and 8--20 keV subbands is similar to and an order
of magnitude higher than that of the previously record HEAO-1 A1 and HEAO-1 A4
all-sky surveys, respectively. A combined 7000 sq. deg area of the sky is
sampled to flux levels below 1e-11 erg/s/cm2 (3--20 keV). In total 294 sources
are detected and localized to better than 1 deg. 236 (80%) of these can be
confidently associated with a known astrophysical object; another 22 likely
result from the superposition of 2 or 3 closely located known sources. 35
detected sources remain unidentified, although for 12 of these we report a
likely soft X-ray counterpart from the ROSAT all-sky survey bright source
catalog. Of the reliably identified sources, 63 have local origin (Milky Way,
LMC or SMC), 64 are clusters of galaxies and 100 are active galactic nuclei
(AGN). The fact that the unidentified X-ray sources have hard spectra suggests
that the majority of them are AGN, including highly obscured ones (nH>1e23
cm^{-2}). For the first time we present a logN-logS diagram for extragalactic
sources above 4e-12 erg/s/cm2 at 8-20 keV.


title:
Statistical properties of local active galactic nuclei inferred from the
  RXTE 3-20 keV all-sky survey

abstract:
  We compiled a sample of 95 AGNs serendipitously detected in the 3-20 keV band
at Galactic latitude |b|>10 during the RXTE slew survey (XSS, Revnivtsev et
al.), and utilize it to study the statistical properties of the local
population of AGNs, including X-ray luminosity function and absorption
distribution. We find that among low X-ray luminosity (Lx < 10^43.5 erg/s)
AGNs, the ratio of absorbed (characterized by intrinsic absorption in the range
10^22 cm^-2 < NH < 10^24 cm^-2) and unabsorbed (NH < 10^22 cm^-2) objects is
2:1, while this ratio drops to less than 1:5 for higher luminosity AGNs. The
summed X-ray output of AGNs with Lx > 10^41 erg/s estimated here is smaller
than the earlier estimated total X-ray volume emissivity in the local Universe,
suggesting that a comparable X-ray flux may be produced together by lower
luminosity AGNs, non-active galaxies and clusters of galaxies. Finally, we
present a sample of 35 AGN candidates, composed of the unidentified XSS
sources.


title:
INTEGRAL/IBIS survey of the Sagittarius Arm Tangent region: A source
  catalog

abstract:
  Analysis of 18-120 keV images of the Sagittarius Arm Tangent region (SATR)
obtained by IBIS telescope onboard INTEGTRAL observatory during the spring of
2003 is performed. In the 18-60 keV energy range, 28 sources have been detected
with a flux level above 1.4 mCrab. Of these sources, 16 were identified earlier
as galactic X-ray binary systems, 3 as extragalactic objects, 2 as pulsars
inside supernova remnants, and 7 has unknown nature. The analysis revealed the
presence of three previously unknown sources. Fourteen sources show significant
flux in the 60-120 keV energy range


title:
The Many Possible Interpretations of Microlensing Event
  OGLE-2002-BLG-055

abstract:
  Microlensing event OGLE-2002-BLG-055 is characterized by a smooth, slightly
asymmetric single-lens curve with an isolated, secure data point that is ~0.6
magnitudes brighter than neighboring points separated by a few days. It was
previously suggested that the single deviant data point and global asymmetry
were best explained by a planetary companion to the primary lens with mass
ratio log(q)=-3 to -2, and parallax effects induced by the motion of the Earth.
We revisit the interpretation of OGLE-2002-BLG-055, and show that the data can
be explained by wide variety of models. We find that the deviant data point can
be fit by a large number of qualitatively different binary-lens models whose
mass ratios range, at the ~3-sigma level, from log(q) ~ -4 to -1. This range is
consistent with a planet, brown dwarf, or M-dwarf companion for reasonable
primary masses of M> 0.8 M_sun. A subset of these binary-lens fits consist of a
family of continuously degenerate models whose mass ratios differ by an
order-of-magnitude, but whose light curves differ by <2% for the majority of
the perturbation. The deviant data point can also explained by a binary
companion to the source with secondary/primary flux ratio of ~1%. This model
has the added appeal that the global asymmetry is naturally explained by the
acceleration of the primary induced by the secondary. The binary-source model
yields a measurement of the Einstein ring radius projected on source plane of
\hat r_E=1.87 +/- 0.40 AU. OGLE-2002-BLG-055 is an extreme example that
illustrates the difficulties and degeneracies inherent in the interpretation of
weakly perturbed and/or poorly sampled microlensing light curves.


title:
A Strong, Broad Absorption Feature in the X-ray Spectrum of the Nearby
  Neutron Star RX J1605.3+3249

abstract:
  We present X-ray spectra taken with XMM-Newton of RX J1605.3+3249, the third
brightest in the class of nearby, thermally emitting neutron stars. In contrast
to what is the case for the brightest object, RX J1856.5-3754, we find that the
spectrum of RX J1605.3+3249 cannot be described well by a pure black body, but
shows a broad absorption feature at 27\AA (0.45 keV). With this, it joins the
handful of isolated neutron stars for which spectral features arising from the
surface have been detected. We discuss possible mechanisms that might lead to
the features, as well as the overall optical to X-ray spectral energy
distribution, and compare the spectrum with what is observed for the other
nearby, thermally emitting neutron stars. We conclude that we may be observing
absorption due to the proton cyclotron line, as was suggested for the other
sources, but weakened due to the strong-field quantum electrodynamics effect of
vacuum resonance mode conversion.


title:
Radiative transfer in the refractive atmospheres of very cool white
  dwarfs

abstract:
  We consider the problem of radiative transfer in stellar atmospheres where
the index of refraction departs from unity and is a function of density and
temperature. We present modified Feautrier and Lambda-iteration methods to
solve the equation of radiative transfer with refraction in a plane parallel
atmosphere. These methods are general and can be used in any problem with 1-D
geometry where the index of refraction is a monotonically varying function of
vertical optical depth. We present an application to very cool white dwarf
atmospheres where the index of refraction departs significantly from unity. We
investigate how ray curvature and total internal reflection affect the limb
darkening and the pressure-temperature structure of the atmosphere. Refraction
results in a much weakened limb darkening effect. We find that through the
constraint of radiative equilibrium, total internal reflection warms the white
dwarf atmosphere near the surface ($\tau \wig< 1$). This effect may have a
significant impact on studies of very cool white dwarf stars.


title:
Imaging extrasolar planets by stellar halo suppression in
  separately-corrected color bands

abstract:
  Extra-solar planets have not been imaged directly with existing ground or
space telescopes because they are too faint to be seen against the halo of the
nearby bright star. Most techniques being explored to suppress the halo are
achromatic, with separate correction of diffraction and wavefront errors.
Residual speckle structure may be subtracted by differencing images taken
through narrowband filters, but photon noise remains and ultimately limits
sensitivity. Here we describe two ways to take advantage of narrow bands to
reduce speckle photon flux and to obtain better control of systematic errors.
Multiple images are formed in separate color bands of 5-10% bandwidth, and
recorded by coronagraphic interferometers equipped with active control of
wavefront phase and/or amplitude. In one method, a single deformable pupil
mirror is used to actively correct both diffraction and wavefront components of
the halo. This yields good diffraction suppression for complex pupil
obscuration, with high throughput over half the focal plane. In a second
method, the coronagraphic interferometer is used as a second stage after
conventional apodization. The halo from uncontrollable residual errors in the
pupil mask or wavefront is removed by destructive interference made directly at
the detector focal plane with an "anti-halo", synthesized by spatial light
modulators in the reference arm of the interferometer. In this way very deep
suppression may be achieved by control elements with greatly relaxed, and thus
achievable, tolerances. In both examples, systematic errors are minimized
because the planet imaging cameras themselves also provide the error sensing
data.


title:
Dynamics and Energetics of Turbulent, Magnetized Disk Accretion around
  Black Holes: a First-Principles Approach to Disk-Corona-Outflow Coupling

abstract:
  We present an analytic description of turbulent, MHD disk accretion around
black holes that specifically addresses the relationship between radial and
vertical, transport, thereby complementing and extending numerical simulations.
The azimuthal-vertical component of the magnetic stress is fundamental to an
understanding of disk--corona--outflow coupling: when it is important for
driving the angular momentum transport and mass accretion in the disk, it also
has an important influence on the disk--corona--outflow energy budget. The
Poynting flux derived from the product of this term with the Keplerian velocity
dominates the Poynting flux into the corona. The ratio of the coronal Alfven
velocity to the Keplerian velocity is an important parameter. If this parameter
is greater than unity then energetically significant winds and Poynting flux
into the corona occur. However, significant effects could occur when this
parameter is much less than unity. A limiting solution describing the case of
angular momentum transport solely by the vertical-azimuthal stress features all
of the accretion power being channeled into a wind, some of which would be
dissipated in the corona. More realistic solutions in which there is both
radial and vertical transport of angular momentum would have different
fractions of the accretion power emitted by the disk and corona. These results
have important implications for existing accretion disk theory and for our
interpretation of high-energy emission and nuclear outflows from black holes.


title:
RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced
  Camera for Surveys

abstract:
  We present a complete census of RR Lyrae stars in a halo field of the
Andromeda galaxy. These deep observations, taken as part of a program to
measure the star formation history in the halo, spanned a period of 41 days
with sampling on a variety of time scales, enabling the identification of short
and long period variables. Although the long period variables cannot be fully
characterized within the time span of this program, the enormous advance in
sensitivity provided by the Advanced Camera for Surveys on the Hubble Space
Telescope allows accurate characterization of the RR Lyrae population in this
field. We find 29 RRab stars with a mean period of 0.594 days, 25 RRc stars
with a mean period of 0.316 days, and 1 RRd star with a fundamental period of
0.473 days and a first overtone period of 0.353 days. These 55 RR Lyrae stars
imply a specific frequency S_RR=5.6, which is large given the high mean
metallicity of the halo, but not surprising given that these stars arise from
the old, metal-poor tail of the distribution. This old population in the
Andromeda halo cannot be clearly placed into one of the Oosterhoff types: the
ratio of RRc/RRabc stars is within the range seen in Oosterhoff II globular
clusters, the mean RRab period is in the gap between Oosterhoff types, and the
mean RRc period is in the range seen in Oosterhoff I globular clusters. The
periods of these RR Lyraes suggest a mean metallicity of [Fe/H]=-1.6, while
their brightness implies a distance modulus to Andromeda of 24.5+/-0.1, in good
agreement with the Cepheid distance.


title:
High Angular Resolution Mid-infrared Imaging of Young Stars in Orion
  BN/KL

abstract:
  We present Keck LWS images of the Orion BN/KL star forming region obtained in
the first multi-wavelength study to have 0.3-0.5" resolution from 4.7 to 22
microns. The young stellar objects designated infrared source-n and radio
source-I are believed to dominate the BN/KL region. We have detected extended
emission from a probable accretion disk around source-n but infer a stellar
luminosity on the order of only 2000 Lsun. Although source-I is believed to be
more luminous, we do not detect an infrared counterpart even at the longest
wavelengths. However, we resolve the closeby infrared source, IRc2, into an arc
of knots ~1000 AU long at all wavelengths. Although the physical relation of
source-I to IRc2 remains ambiguous, we suggest these sources mark a high
density core (10^7-10^8 pc^-3 over 1000 AU) within the larger BN/KL star
forming cluster. The high density may be a consequence of the core being young
and heavily embedded. We suggest the energetics of the BN/KL region may be
dominated by this cluster core rather than one or two individual sources.


title:
New Period-Luminosity and Period-Color Relations of Classical Cepheids:
  II. Cepheids in LMC

abstract:
  Photometric data for 593 Cepheids in the LMC, measured by Udalski et al. in
the OGLE survey, augmented by 92 longer period Cepheids from other sources, are
analyzed for the P-C and P-L relations, and for the variations of amplitude,
light curve shape, and period across the instability strip at constant absolute
magnitude. Both the P-C and P-L relations have different slopes for periods
smaller and larger than 10 days. The break at 10 days is also seen in the
period-amplitude relations, and the compound Fourier combinations of R_21 and
Phi_21 introduced by Simon and Lee.
  The LMC Cepheids are bluer than Galactic Cepheids in the B,V,I color bands,
part of which is due to differential Fraunhofer line blanketing and part to
real differences in the temperature boundaries of the instability strip. The
LMC strip is hotter by between 80K and 350K depending on the period. Hence,
both the slopes and (necessarily) the zero points of the P-L relations in B,V,I
must differ between LMC and the the Galaxy, and in fact they do. The LMC
Cepheids are brighter by up to 0.5 mag at log P=0.4 (2 days) and fainter by 0.2
mag at log P=1.5 (32 days). These facts complicate the use of Cepheid as
precision distance indicators until the reason is found for the
non-universality of the P-L and P-C relations.
  The very large data base permits mapping of various Cepheid properties at
different positions within the instability strip, both at constant period and
at constant absolute magnitude over the range of 2 < P < 40 days and -2 > M_V >
-5. (...)


title: Detection of Giant Pulses from the Pulsar PSR B0031-07

abstract:
  Giant pulses have been detected from the pulsar PSR B0031-07. A pulse with an
intensity higher than the intensity of the average pulse by a factor of 50 or
more is encountered approximately once per 300 observed periods. The peak flux
density of the strongest pulse is 530 Jy, which is a factor of 120 higher than
the peak flux density of the average pulse. The giant pulses are a factor of 20
narrower than the integrated profile and are clustered about its center.


title: Are vertical cosmic rays the most suitable to radio detection ?

abstract:
  The electric field induced by extensive air showers generated by high energy
cosmic rays is considered and, more specifically, its dependence on the shower
incident angle. It is shown that for distances between the shower axis and the
observation point larger than a few hundred meters, non-vertical showers
produce larger fields than vertical ones. This may open up new prospects since,
to some extent, the consideration of non-vertical showers modifies the scope of
the radio-detection domain.


title:
Mass-to-Light ratio, Initial Mass Function and chemical evolution in
  disc galaxies

abstract:
  Cosmological simulations of disc galaxy formation, when compared to the
observed Tully-Fisher relation, suggest a low Mass-to-Light (M/L) ratio for the
stellar component in spirals. We show that a number of "bottom-light" Initial
Mass Functions (IMFs) suggested independently in literature, do imply M/L
ratios as low as required, at least for late type spirals (Sbc/Sc). However the
typical M/L ratio, and correspondingly the zero-point of the Tully-Fisher
relation, is expected to vary considerably with Hubble type.
  Bottom-light IMFs tend to have a metal production in excess of what is
tipically estimated for spiral galaxies. Suitable tuning of the IMF slope and
mass limits, post-supernova fallback of metals onto black holes or metal
outflows must then be invoked, to reproduce the observed chemical properties of
disc galaxies.


title: Unbiased Estimation of an Angular Power Spectrum

abstract:
  We discuss the derivation of the analytic properties of the cross-power
spectrum estimator from multi-detector CMB anisotropy maps. The method is
computationally convenient and it provides unbiased estimates under very broad
assumptions. We also propose a new procedure for testing for the presence of
residual bias due to inappropriate noise subtraction in pseudo-$C_{\ell}$
estimates. We derive the analytic behavior of this procedure under the null
hypothesis, and use Monte Carlo simulations to investigate its efficiency
properties, which appear very promising. For instance, for full sky maps with
isotropic white noise, the test is able to identify an error of 1% on the noise
amplitude estimate.


title:
Effect of neutrino asymmetry on the estimation of cosmological
  parameters

abstract:
  The recent analysis of the cosmic microwave background data carried out by
the WMAP team seems to show that the sum of the neutrino masses is <0.7 eV.
However, this result is not model-independent, depending on precise assumptions
on the cosmological model. We study how this result is modified when the
assumption of perfect lepton symmetry is dropped out.


title:
General relativistic MHD simulations of monopole magnetospheres of black
  holes

abstract:
  In this paper we report the results of the first ever time-dependent general
relativistic magnetohydrodynamic simulations of the magnetically dominated
monopole magnetospheres of black holes. It is found that the numerical solution
evolves towards a stable steady-state solution which is very close to the
corresponding force-free solution found by Blandford and Znajek. Contrary to
the recent claims, the particle inertia does not become dynamically important
near the event horizon and the force-free approximation provides a proper
framework for magnetically dominated magnetospheres of black holes. For the
first time, our numerical simulations show the development of an
ultra-relativistic particle wind from a rotating black hole. However, the flow
remains Poynting dominated all the way up to the fast critical point. This
suggests that the details of the so-called ``astrophysical load'', where the
electromagnetic energy is transferred to particles, may have no effect on the
efficiency of the Blandford-Znajek mechanism.


title: A Search for Luminous Be stars

abstract:
  As Be stars are restricted to luminosity classes III-V, but early B-type
stars are believed to evolve into supergiants, it is to be expected that the Be
phenomenon disappears at some point in the evolution of a moderately massive
star, before it reaches the supergiant phase. As a first stage in an attempt to
determine the physical reasons of this cessation, a search of the literature
has provided a number of candidates to be Be stars with luminosity classes Ib
or II. Spectroscopy has been obtained for candidates in a number of open
clusters and associations, as well as several other bright stars in those
clusters. Among the objects observed, HD207329 is the best candidate to be a
high-luminosity Be star, as it appears like a fast-rotating supergiant with
double-peaked emission lines. The lines of HD229059, in Berkeley 87, also
appear morphologically similar to those of Be stars, but there are reasons to
suspect that this object is an interacting binary. At slightly lower
luminosities, LS I +56 92 (B4II) and HD333452 (O9II), also appear as
intrinsically luminous Be stars. Two Be stars in NGC 6913, HD229221 and
HD229239, appear to have rather higher intrinsic magnitudes than their spectral
type (B0.2III in both cases) would indicate, being as luminous as luminosity
class II objects in the same cluster. HD344863, in NGC 6823, is also a rather
early Be star of moderately high luminosity. The search shows that, though
high-luminosity Be stars do exist, they are scarce and, perhaps surprisingly,
tend to have early spectral types


title:
A three-dimensional model for the radio emission of magnetic chemically
  peculiar stars

abstract:
  In this paper we present a three-dimensional numerical model for the radio
emission of Magnetic Chemically Peculiar stars, on the hypothesis that
energetic electrons emit by the gyrosynchrotron mechanism. For this class of
radio stars, characterized by a mainly dipolar magnetic field whose axis is
tilted with respect to the rotational axis, the geometry of the magnetosphere
and its deformation due to the stellar rotation are determined. The radio
emitting region is determined by the physical conditions of the magnetosphere
and of the stellar wind. Free-free absorption by the thermal plasma trapped in
the inner magnetosphere is also considered. Several free parameters are
involved in the model, such as the size of the emitting region, the energy
spectrum and the number density of the emitting electrons, and the
characteristics of the plasma in the inner magnetosphere. By solving the
equation of radiative transfer, along a path parallel to the line of sight, the
radio brightness distribution and the total flux density as a function of
stellar rotation are computed. As the model is applied to simulate the observed
5 GHz lightcurves of HD37479 and HD37017, several possible magnetosphere
configurations are found. After simulations at other frequencies, in spite of
the large number of parameters involved in the modeling, two solutions in the
case of HD37479 and only one solution in the case of HD37017 match the observed
spectral indices. The results of our simulations agree with the magnetically
confined wind-shock model in a rotating magnetosphere. The X-ray emission from
the inner magnetosphere is also computed, and found to be consistent with the
observations.


title: Protostellar mass accretion rates from gravoturbulent fragmentation

abstract:
  We analyse protostellar mass accretion rates from numerical models of star
formation based on gravoturbulent fragmentation, considering a large number of
different environments. To within one order of magnitude, the mass accretion
rate is approximately given by the mean thermal Jeans mass divided by the
corresponding free-fall time. However, mass accretion rates are highly
time-variant, with a sharp peak shortly after the formation of the protostellar
core. We present an empirical exponential fit formula to describe the time
evolution of the mass accretion and discuss the resulting fit parameters. There
is a positive correlation between the peak accretion rate and the final mass of
the protostar. We also investigate the relation of the accretion rate with the
turbulent flow velocity as well as with the driving wavenumbers in different
environments. We then compare our results with other theoretical models of star
formation and with observational data.


title:
Equilibria of a Self-Gravitating, Rotating Disk Around a Magnetized
  Compact Object

abstract:
  We examine the effect of self-gravity in a rotating thick-disk equilibrium in
the presence of a dipolar magnetic field. In the first part, we find a
self-similar solution for non-self-gravitating disks. The solution that we have
found shows that the pressure and density equilibrium profiles are strongly
modified by a self-consistent toroidal magnetic field. We introduce 3
dimensionless variables $C_B$, $C_c$, $C_t$ that indicate the relative
importance of toroidal component of magnetic field ($C_B$), centrifugal ($C_c$)
and thermal ($C_t$) energy with respect to the gravitational potential energy
of the central object. We study the effect of each of them on the structure of
the disk. In the second part, we investigate the effect of self-gravity on the
these disks; thus we introduce another dimensionless variable ($C_g$) that
shows the importance of self-gravity. We find a self-similar solution for the
equations of the system. Our solution shows that the structure of the disk is
modified by the self-gravitation of the disk, the magnetic field of the central
object, and the azimuthal velocity of the gas disk. We find that self-gravity
and magnetism from the central object can change the thickness and the shape of
the disk. We show that as the effect of self-gravity increases the disk becomes
thinner. We also show that for different values of the star's magnetic field
and of the disk's azimuthal velocity, the disk's shape and its density and
pressure profiles are strongly modified.


title: The Indo-U.S. Library of Coude Feed Stellar Spectra

abstract:
  We have obtained spectra for 1273 stars using the 0.9m Coud\'e Feed telescope
at Kitt Peak National Observatory. This telescope feeds the coud\'e
spectrograph of the 2.1m telescope. The spectra have been obtained with the #5
camera of the coud\'e spectrograph and a Loral 3K X 1K CCD. Two gratings have
been used to provide spectral coverage from 3460 \AA to 9464 \AA, at a
resolution of $\sim$1\AA FWHM and at an original dispersion of 0.44 \AA/pixel.
For 885 stars we have complete spectra over the entire 3460 \AA to 9464 \AA
wavelength region (neglecting small gaps of $<$ 50 \AA), and partial spectral
coverage for the remaining stars. The 1273 stars have been selected to provide
broad coverage of the atmospheric parameters T$_{eff}$, log g, and [Fe/H], as
well as spectral type. The goal of the project is to provide a comprehensive
library of stellar spectra for use in the automated classification of stellar
and galaxy spectra and in galaxy population synthesis. In this paper we discuss
the characteristics of the spectral library, viz., details of the observations,
data reduction procedures, and selection of stars. We also present a few
illustrations of the quality and information available in the spectra. The
first version of the complete spectral library is now publicly available from
the National Optical Astronomy Observatory (NOAO) via FTP and HTTP.


title:
The Gemini Deep Deep Survey: I. Introduction to the Survey, Catalogs and
  Composite Spectra

abstract:
  The Gemini Deep Deep Survey (GDDS) is an ultra-deep (K<20.6 mag, I<24.5 mag)
redshift survey targeting galaxies in the "redshift desert" between 1<z<2. The
primary goal of the survey is to constrain the space density at high redshift
of evolved high-mass galaxies. We obtained 309 spectra in four widely-separated
30 arcmin^2 fields using the Gemini North telescope and the Gemini Multi-Object
Spectrograph (GMOS). The spectra define a one-in-two sparse sample of the
reddest and most luminous galaxies near the I-K vs. I color-magnitude track
mapped out by passively evolving galaxies in the redshift interval 0.8<z<1.8.
This sample is augmented by a one-in-seven sparse sample of the remaining
high-redshift galaxy population. Typical exposures times were 20-30 hours per
field (in Nod & Shuffle mode), and the resulting spectra are the deepest ever
obtained. In this paper we present our sample of 309 spectra, along with
redshifts, identifications of spectral features, and photometry. The infrared
selection underlying the survey means that the GDDS is observing not only
star-forming galaxies, as in most high-redshift galaxy surveys, but also
quiescent evolved galaxies. The median redshift of the whole GDDS sample is
z=1.1. Together with the data and catalogs, we present a summary of the
criteria for selecting the GDDS fields, the rationale behind our mask designs,
an analysis of the completeness of the survey, and a description of the data
reduction procedures used. All data from the GDDS are publicly available.
(ABRIDGED)


title: Discovery of X-ray flaring on the magnetic Bp-star sigma Ori E

abstract:
  We report the detection of an X-ray flare on the Bp star sigma Ori E with the
ROSAT high resolution imager (HRI). The flare is shown to have likely occurred
on the early-type star, rather than on an hypothesized late-type companion. We
derive flare parameters such as total energy release, coarse estimates of size
and density, and also present arguments for a magnetic origin of the flare. We
place our observations in the context of a magnetic character of Bp-type stars
and speculate on a common physical basis and connection between Bp and Be
stars.


title: Photoabsorption of Gamma Rays in Relativistic Jets

abstract:
  A derivation of the \gamma\gamma --> e^+ e^- optical depth for \gamma rays
produced in a comoving spherical emitting region is presented. Employing a
simplified expression for the \gamma\gamma absorption cross section, analytic
expressions for the minimum Doppler factor implied by the requirement of
gamma-ray transparency are derived for a broken power-law spectrum of target
photons which are isotropically distributed in the comoving frame. Application
to specific systems is illustrated.


title:
The GEMS project: X-ray analysis and statistical properties of the group
  sample

abstract:
  The GEMS project involves a multi-wavelength study of a sample of 60 galaxy
groups. Substantial ROSAT PSPC observations are used to characterise the state
of the intergalactic medium in each. We present the results of a uniform
analysis of these ROSAT data, and a statistical investigation of the
relationship between X-ray and optical properties across the sample. The
steepening of the LX-TX relation in the group regime reported previously is not
seen in our sample, which fits well onto the cluster trend. A number of biases
affect the fitting of regression lines under these circumstances, and until the
impact of these has been thoroughly investigated it seems best to regard the
slope of the group LX-TX relation as being poorly determined. A significant
problem in comparing the properties of groups and clusters is the derivation of
system radii, to allow different systems to be compared within regions having
the same overdensity. We find evidence that group velocity dispersion provides
a very unreliable measure of system mass (and hence radius), with a number of
groups having remarkably low values of sigma. We confirm that the surface
brightness profiles of groups are significantly flatter than those of clusters,
however we find no significant tendency within our sample for cooler groups to
show flatter profiles. This result is inconsistent with simple universal
preheating models. The morphology of the galaxies in the GEMS groups is
correlated to their X-ray properties in a number of ways: we confirm the very
strong relationship between X-ray emission and a dominant early-type central
galaxy, and also find that spiral fraction is correlated with the temperature
of the hot gas. A class of spiral-rich groups with little or no X-ray emission,
probably corresponds to groups which have not yet fully collapsed.


title: Large scale simulations of the jet-IGM interaction

abstract:
  In a parameter study extending to jet densities of $10^{-5}$ times the
ambient one, I have recently shown that light large scale jets start their
lives in a spherical bow shock phase. This allows an easy description of the
sideways bow shock propagation in that phase. Here, I present new, bipolar,
simulations of very light jets in 2.5D and 3D, reaching the observationally
relevant scale of $>200$ jet radii. Deviations from the early bow shock
propagation law are expected because of various effects. The net effect is,
however, shown to remain small. I calculate the X-ray appearance of the shocked
cluster gas and compare it to Cygnus A and 3C 317. Rings, bright spots and
enhancements inside the radio cocoon may be explained.


title: Quenching Cluster Cooling Flows with Recurrent Hot Plasma Bubbles

abstract:
  The observed cooling rate of hot gas in clusters is much lower than that
inferred from the gas density profiles. This suggests that the gas is being
heated by some source. We use an adaptive-mesh refinement code (FLASH) to
simulate the effect of multiple, randomly positioned, injections of thermal
energy within 50 kpc of the centre of an initially isothermal cluster with mass
M_200=3x10^(14) Msol and kT=3.1 keV. We have performed eight simulations with
spherical bubbles of energy generated every 10^8 years, over a total of 1.5
Gyr. Each bubble is created by injecting thermal energy steadily for 10^7
years; the total energy of each bubble ranges from 0.1--3x10^(60) erg,
depending on the simulation. We find that 2x10^(60) erg per bubble
(corresponding to a average power of 6.3x10^(44) erg/s) effectively balances
energy loss in the cluster and prevents the accumulation of gas below kT=1 keV
from exceeding the observational limits of 30 Msol/yr. This injection rate is
comparable to the radiated luminosity of the cluster, and the required energy
and periodic timescale of events are consistent with observations of bubbles
produced by central AGN in clusters. The effectiveness of this process depends
primarily on the total amount of injected energy and the initial location of
the bubbles, but is relatively insensitive to the exact duty cycle of events.


title: Weak Lensing of the CMB: Sampling Errors on B-Modes

abstract:
  The B modes generated by the lensing of CMB polarization are a primary target
for the upcoming generation of experiments and can potentially constrain
quantities such as the neutrino mass and dark energy equation of state. The net
sample variance on the small scale B modes out to l=2000 exceeds Gaussian
expectations by a factor of 10 reflecting the variance of the larger scale
lenses that generate them. It manifests itself as highly correlated band powers
with correlation coefficients approaching 70% for wide bands of Delta l/l
\~0.25. It will double the total variance for experiments that achieve a
sensitivity of approximately 4 uK-arcmin and a beam of several arcminutes or
better. This non-Gaussianity must be taken into account in the analysis of
experiments that go beyond first detection.


title: Towards optimal parallel PM N-body codes: PMFAST

abstract:
  We present a new parallel PM N-body code named PMFAST that is freely
available to the public. PMFAST is based on a two-level mesh gravity solver
where the gravitational forces are separated into long and short range
components. The decomposition scheme minimizes communication costs and allows
tolerance for slow networks. The code approaches optimality in several
dimensions. The force computations are local and exploit highly optimized
vendor FFT libraries. It features minimal memory overhead, with the particle
positions and velocities being the main cost. The code features support for
distributed and shared memory parallelization through the use of MPI and
OpenMP, respectively.
  The current release version uses two grid levels on a slab decomposition,
with periodic boundary conditions for cosmological applications. Open boundary
conditions could be added with little computational overhead. We present timing
information and results from a recent cosmological production run of the code
using a 3712^3 mesh with 6.4 x 10^9 particles. PMFAST is cost-effective,
memory-efficient, and is publicly available.


title: Out-of-Core Hydrodynamic Simulations for Cosmological Applications

abstract:
  We present an out-of-core hydrodynamic code for high resolution cosmological
simulations that require terabytes of memory. Out-of-core computation refers to
the technique of using disk space as virtual memory and transferring data in
and out of main memory at high I/O bandwidth. The code is based on a two-level
mesh scheme where short-range physics is solved on a high-resolution, localized
mesh while long-range physics is captured on a lower resolution, global mesh.
The two-level mesh gravity solver allows FFTs to operate on data stored
entirely in memory, which is much faster than the alternative of computing the
transforms out-of-core through non-sequential disk accesses. We also describe
an out-of-core initial conditions generator that is used to prepare large data
sets for cosmological simulations. The out-of-core code is accurate,
cost-effective, and memory-efficient and the current version is implemented to
run in parallel on shared-memory machines. I/O overhead is significantly
reduced down to less than 10% by performing disk operations concurrently with
numerical calculations. The current computational setup, which includes a 32
processor Alpha server and a 3 TB striped SCSI disk array, allows us to run
cosmological simulations with up to 4000^3 grid cells and 2000^3 dark matter
particles.


title:
On the Origin of the Radio/X-Ray Luminosity Correlation in Black Hole
  Candidates

abstract:
  In previous work we found that the spectral state switch and other spectral
properties of both neutron star (NS) and galactic black hole candidates (GBHC),
in low mass x-ray binary systems could be explained by a magnetic propeller
effect that requires an intrinsically magnetic central compact object. In later
work we showed that intrinsically magnetic GBHC could be easily accommodated by
general relativity in terms of magnetospheric eternally collapsing objects
(MECO), with lifetimes greater than a Hubble time, and examined some of their
spectral properties. In this work we show how a standard thin accretion disk
and corona can interact with the central magnetic field in atoll class NS, and
GBHC and active galactic nuclei (AGN) modeled as MECO, to produce jets that
emit radio through infrared luminosity $L_R$ that is correlated with mass and
x-ray luminosity as $L_R \propto M^{0.75 - 0.92}L_x^{2/3}$ up to a mass scale
invariant cutoff at the low/high spectral state switch. Comparing the
MECO-GBHC/AGN model to observations, we find that the correlation exponent, the
mass scale invariant cutoff, and the radio luminosity ratios of AGN, GBHC and
atoll class NS are correctly predicted, which strongly implies that GBHC and
AGN have observable intrinsic magnetic moments and hence do not have event
horizons.


title: 3D Simulations of the Local Bubble

abstract:
  We have performed high resolution 3D simulations of the Local Bubble (with
1.25 pc finest resolution) in a realistic background ISM, jointly with the
dynamical evolution of the neighbouring Loop I superbubble. We can reproduce
(i) the size of the bubbles (in contrast to similarity solutions), (ii) the
interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging
of the two bubbles in about 3 Myr, when the interaction shell starts to
fragment, and, (iv) the generation of blobs like the Local Cloud as a
consequence of a dynamical instability.


title: Flux ratio [Ne V] 14.3/24.3 as a test of collision strengths

abstract:
  From ISO [Ne V] 14.3/24.3 micron line flux ratios, we find that 10 out of 20
planetary nebulae (PNs) have measured ratios below the low-electron density
(N_e) theoretical predicted limit. Such astronomical data serve to provide
important tests of atomic data, collision strengths in this case. In principle,
well-calibrated measurements of the [Ne V] 14.3/24.3 flux ratio could improve
upon the existing atomic data.


title:
3D HD and MHD Adaptive Mesh Refinement Simulations of the Global and
  Local ISM

abstract:
  We have performed high resolution 3D simulations with adaptive mesh
refinement, following the ISM evolution in a star forming galaxy both on small
(<1 pc) and large (>10 kpc) scales, enabling us to track structures in cooling
shock compressed regions as well as the entire Galactic fountain flow. It is
shown in an MHD run that the latter one is not inhibited by a large scale disk
parallel magnetic field. The fountain plays a vital role in limiting the volume
filling factor of the hot gas. Contrary to classical models most of the gas
between 100K and 8000 K is found to be thermally unstable. On scales of
superbubbles we find that the internal temperature structure is rather
inhomogeneous for an old object like our Local Bubble, leading to low OVI
column densities, consistent with observations.


title:
The hybrid SZ power spectrum: Combining cluster counts and SZ
  fluctuations to probe gas physics

abstract:
  Sunyaev-Zeldovich (SZ) effect from a cosmological distribution of clusters
carry information on the underlying cosmology as well as the cluster gas
physics. In order to study either cosmology or clusters one needs to break the
degeneracies between the two. We present a toy model showing how complementary
informations from SZ power spectrum and the SZ flux counts, both obtained from
upcoming SZ cluster surveys, can be used to mitigate the strong cosmological
influence (especially that of sigma_8) on the SZ fluctuations. Once the strong
dependence of the cluster SZ power spectrum on sigma_8 is diluted, the cluster
power spectrum can be used as a tool in studying cluster gas structure and
evolution. The method relies on the ability to write the Poisson contribution
to the SZ power spectrum in terms the observed SZ flux counts. We test the toy
model by applying the idea to simulations of SZ surveys.


title: GSH23.0-0.7+117, a neutral hydrogen shell in the inner Galaxy

abstract:
  GSH23.0-0.7+117 is a well-defined neutral hydrogen shell discovered in the
VLA Galactic Plane Survey (VGPS). Only the blueshifted side of the shell was
detected. The expansion velocity and systemic velocity were determined through
the systematic behavior of the HI emission with velocity. The center of the
shell is at (l,b,v)=(23.05,-0.77,+117 km/s). The angular radius of the shell is
6.8', or 15 pc at a distance of 7.8 kpc. The HI mass divided by the volume of
the half-shell implies an average density n_H = 11 +/- 4 cm^{-3} for the medium
in which the shell expanded. The estimated age of GSH23.0-0.7+117 is 1 Myr,
with an upper limit of 2 Myr. The modest expansion energy of 2 * 10^{48} erg
can be provided by the stellar wind of a single O4 to O8 star over the age of
the shell. The 3 sigma upper limit to the 1.4 GHz continuum flux density
(S_{1.4} < 248 mJy) is used to derive an upper limit to the Lyman continuum
luminosity generated inside the shell. This upper limit implies a maximum of
one O9 star (O8 to O9.5 taking into account the error in the distance) inside
the HI shell, unless most of the incident ionizing flux leaks through the HI
shell. To allow this, the shell should be fragmented on scales smaller than the
beam (2.3 pc). If the stellar wind bubble is not adiabatic, or the bubble has
burst (as suggested by the HI channel maps), agreement between the energy and
ionization requirements is even less likely. The limit set by the non-detection
in the continuum provides a significant challenge for the interpretation of
GSH23.0-0.7+117 as a stellar wind bubble. A similar analysis may be applicable
to other Galactic HI shells that have not been detected in the continuum.


title:
Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects
  of Temperature, Clouds, and Gravity

abstract:
  We present JHK photometry and spectroscopy for a sample of newly identified L
and T dwarfs from the Sloan Digital Sky Survey (SDSS) and known dwarfs from the
SDSS and the Two Micron All Sky Survey (2MASS). Spectral classification has
been carried out using four infrared indices; we identify 9 new L8-9.5 dwarfs
and 14 new T dwarfs from SDSS, including the latest SDSS dwarf yet found, the
T7 SDSS J1758+4633. We classify 2MASS J0415-0935 as T9, the latest and coolest
dwarf found to date. We combine these results with previously published data to
produce a sample of 59 L dwarfs and 42 T dwarfs. We compare the near-IR colors
and absolute magnitudes of dwarfs near the L-T transition with predictions made
by models of the distribution and evolution of photospheric condensates. There
is scatter in the spectral indices for L dwarfs, suggesting that these indices
are probing different levels of the atmosphere. The near-IR colors of the L
dwarfs also scatter, likely due to variations in the altitudes, spatial
distributions and thicknesses of the condensate clouds. We identify a group of
late L dwarfs that are blue for their spectral type and that have enhanced FeH,
H2O and KI absorption, possibly due to an unusually small amount of
condensates. The scatter seen in the H-K color for late T dwarfs can be
reproduced by models with a range in surface gravity. The variation is probably
due to the effect on the K-band flux of pressure-induced H2 opacity. The
correlation of H-K color with gravity is supported by the strengths of the
J-band KI doublet. Gravity is closely related to mass for field T dwarfs and
the gravities implied by the H-K colors indicate that the T dwarfs in our
sample have masses in the range 15-75 M_Jupiter, except for SDSS J1110+0116
which possibly has a mass of 10-15 M_Jupiter.


title:
HST STIS Ultraviolet Spectral Evidence of Outflow in Extreme Narrow-line
  Seyfert 1 Galaxies: II. Modeling and Interpretation

abstract:
  We present modeling to explore the conditions of the broad-line emitting gas
in two extreme Narrow-line Seyfert 1 galaxies, using the observational results
described in the first paper of this series. Photoionization modeling using
Cloudy was conducted for the broad, blueshifted wind lines and the narrow,
symmetric, rest-wavelength-centered disk lines separately. A broad range of
physical conditions were explored for the wind component, and a figure of merit
was used to quantitatively evaluate the simulation results. Of the three minima
in the figure-of-merit parameter space, we favor the solution characterized by
an X-ray weak continuum, elevated abundances, a small column density
(log(N_H)\approx 21.4), relatively high ionization parameter (log(U)\approx
-1.2 - -0.2), a wide range of densities (log(n)\approx 7 - 11), and a covering
fraction of ~0.15. The presence of low-ionization emission lines implies the
disk component is optically thick to the continuum, and the SiIII]/CIII] ratio
implies a density of 10^10 - 10^10.25 cm^-3. A low ionization parameter
(log(U)=-3) is inferred for the intermediate-ionization lines, unless the
continuum is ``filtered'' through the wind before illuminating the
intermediate-line emitting gas, in which case log(U)=-2.1. The location of the
emission regions was inferred from the photoionization modeling and a simple
``toy'' dynamical model. A large black hole mass (1.3 x 10^8 M_\odot) radiating
at 11% of the Eddington luminosity is consistent with the kinematics of both
the disk and wind lines, and an emission radius of ~10^4 R_S is inferred for
both. We compare these results with previous work and discuss implications.


title:
HST STIS Ultraviolet Spectral Evidence for Outflow in Extreme
  Narrow-line Seyfert 1 Galaxies: I. Data and Analysis

abstract:
  We present HST STIS observations of two extreme NLS1s, IRAS 13224-3809 and 1H
0707-495. The spectra are characterized by very blue continua, broad, strongly
blueshifted high-ionization lines (including \ion{C}{4} and \ion{N}{5}), and
narrow, symmetric intermediate- (including \ion{C}{3}], \ion{Si}{3}],
\ion{Al}{3}) and low-ionization (e.g., \ion{Mg}{2}) lines centered at their
rest wavelengths. The emission-line profiles suggest that the high-ionization
lines are produced in a wind, and the intermediate- and low-ionization lines
are produced in low-velocity gas associated with the accretion disk or base of
the wind. In this paper, we present the analysis of the spectra from these two
objects; in a companion paper we present photoionization analysis and a toy
dynamical model for the wind. The highly asymmetric profile of \ion{C}{4}
suggests that it is dominated by emission from the wind, so we develop a
template for the wind from the \ion{C}{4} line. We model the bright emission
lines in the spectra using a combination of this template, and a narrow,
symmetric line centered at the rest wavelength. We also analyzed a comparison
sample of HST spectra from 14 additional NLS1s, and construct a correlation
matrix of emission line and continuum properties. A number of strong
correlations were observed, including several involving the asymmetry of the
\ion{C}{4} line.


title:
A SCUBA Map in the Spitzer First Look Survey: Source Catalog and Number
  Counts

abstract:
  Using the SCUBA instrument on the JCMT, we have made a submillimeter mosaic
at 850um of a subarea of the Spitzer First Look Survey (FLS). Our image covers
the central 151 square arcmin of the northern extragalactic Continuous Viewing
Zone (CVZ) field of the FLS to a median 3sigma depth of 9.7 mJy. The image
contains ten 850um sources detected at 3.5sigma or higher significance, of
which five are detected at greater than or equal 4sigma. We make the catalog of
these SCUBA-selected FLS sources available to the community. After correcting
for incompleteness and flux bias, we find that the density of sources brighter
that 10mJy in our field is (1.3 +1.1 -0.7)x10^2 deg^-2 (95% Poisson confidence
limits), which is consistent with other surveys that probe the bright end of
the submillimeter population.


title:
Group actions, geodesic loops, and symmetries of compact hyperbolic
  3-manifolds

abstract:
  Compact hyperbolic 3-manifolds are used in cosmological models. Their
topology is characterized by their homotopy group $\pi_1(M)$ whose elements
multiply by path concatenation. The universal covering of the compact manifold
$M$ is the hyperbolic space $H^3$ or the hyperbolic ball $B^3$. They share with
$M$ a Riemannian metric of constant negative curvature and allow for the
isometric action of the group $Sl(2,C)$. The homotopy group $\pi_1(M)$ acts as
a uniform lattice $\Gamma(M)$ on $B^3$ and tesselates it by copies of $M$. Its
elements $g$ produce preimage and image points for geodesic sections on $B^3$
which by self-intersection form geodesic loops on $M$. For any fixed hyperbolic
$g \in \Gamma$ we construct a continuous commutative two-parameter normalizer
$N_g <Sl(2,C)$ and its orbit surfaces on $B^3$. The orbit surfaces classify
sets of geodesic loops of equal length. We give general expressions for the
length of geodesic loops and for the defect angle at the self-intersection on
$M$ in terms of the group parameters of $g$ and orbit parameters on $B^3$.
Geodesic loops of minimal length, given from the character $\chi(g)$, belong to
a single orbit. These and only these minimal geodesic loops have vanishing
defect angle and hence are smooth everywhere. The role of symmetries is
illuminated by the example of the dodecahedral hyperbolic Weber-Seifert
manifold $M$. $\Gamma(M)$ is normal in the hyperbolic Coxeter group with
Coxeter diagram ${\bf \circ \frac{5}{}\circ\frac{3}{}\circ\frac{5}{}\circ}$.
This leads to symmetry relations between geodesic loops.


title:
Deep SAURON Spectral-Imaging of the diffuse Lyman-alpha halo LAB1 in
  SSA22

abstract:
  We have used the SAURON panoramic integral field spectrograph to study the
structure of the Ly-alpha emission-line halo, LAB1, surrounding the
sub-millimeter galaxy SMM J221726+0013. This emission-line halo was discovered
during a narrow-band imaging survey of the z=3.1 large-scale structure in the
SSA22 region. Our observations trace the emission halo out to almost 100 kpc
from the sub-millimeter source and identify two distinct Ly-alpha `mini-haloes'
around the nearby Lyman-break galaxies. The main emission region has a broad
line profile, with variations in the line profile seeming chaotic and lacking
evidence for a coherent velocity structure. The data also suggests that
Ly-alpha emission is suppressed around the sub-mm source. Interpretation of the
line structure needs care because Ly-alpha may be resonantly scattered, leading
to complex radiative transfer effects, and we suggest that the suppression in
this region arises because of such effects. We compare the structure of the
central emission-line halo with local counter-parts, and find that the emission
line halo around NGC 1275 in the Perseus cluster may be a good local analogue,
although the high redshift halo is factor of ~100 more luminous and appears to
have higher velocity broadening. Around the Lyman-break galaxy C15, the
emission line is narrower, and a clear shear in the emission wavelength is
seen. A plausible explanation for the line profile is that the emission gas is
expelled from C15 in a bipolar outflow, similar to that seen in M82.


title:
Polarization of GRB by scattering off relativistically moving material:
  Compton sailing and high polarization

abstract:
  The polarization of gamma ray emission scattered off the baryon rich material
that collimates a GRB fireball and the coasting speed of the irradiated matter
are calculated numerically for different geometries of the radiation source and
the collimating wall. It is shown that when the scattering material is Compton
sailing, the direction of maximum polarization is quite generally well within
the beaming cone of scattered radiation. As a result, the probability for
observing bright highly polarized GRB's increases considerably, provided the
Lorentz factor of the coasting matter is not well below 30, and the scattered
radiation is highly polarized even when the beam thickness is large compared to
$1/\Gamma$. It is suggested that correlation between polarization and intensity
could provide clues as to whether energy flows from matter to photons or the
reverse.


title: On the Nature of the Binary Components of RX J0806.3+1527

abstract:
  We present imaging circular polarimetry and near-infrared photometry of the
suspected ultra-short period white-dwarf binary RX J0806.3+1527 obtained with
the ESO VLT and discuss the implications for a possible magnetic nature of the
white dwarf accretor and the constraints derived for the nature of the donor
star. Our V-filter data show marginally significant circular polarization with
a modulation amplitude of ~0.5% typical for cyclotron emission from an
accretion column in a magnetic field of order 10 MG and not compatible with a
direct-impact accretor model. The optical to near-infrared flux distribution is
well described by a single blackbody with temperature kT_bb = 35000 K and
excludes a main-sequence stellar donor unless the binary is located several
scale heights above the galactic disk population.


title:
Low-Mass Pre-Main Sequence Stars in the Large Magellanic Cloud - III:
  Accretion Rates from HST-WFPC2 Observations

abstract:
  We have measured the present accretion rate of roughly 800 low-mass (~1-1.4
Mo) pre-Main Sequence stars in the field of Supernova 1987A in the Large
Magellanic Cloud (LMC, Z~0.3 Zo). It is the first time that this fundamental
parameter for star formation is determined for low-mass stars outside our
Galaxy. The Balmer continuum emission used to derive the accretion rate
positively correlates with the Halpha excess. Both these phenomena are believed
to originate from accretion from a circumstellar disk so that their
simultaneous detection provides an important confirmation of the pre-Main
Sequence nature of the Halpha and UV excess objects, which are likely to be the
LMC equivalent of Galactic Classical TTauri stars. The stars with statistically
significant excesses are measured to have accretion rates larger than
1.5x10^{-8}Mo/yr at an age of 12-16 Myrs. For comparison, the time scale for
disk dissipation observed in the Galaxy is of the order of 6 Myrs. Moreover,
the oldest Classical TTauri star known in the Milky Way (TW Hydrae, with 10
Myrs of age) has a measured accretion rate of only 5x10^{-10} Mo/yr, ie 30
times less than what we measure for stars at a comparable age in the LMC. Our
findings indicate that metallicity plays a major role in regulating the
formation of low-mass stars.


title:
The Luminosity Function and Color-Magnitude Diagram of the Globular
  Cluster M12

abstract:
  In this paper we present the V and I luminosity functions and color-magnitude
diagrams derived from wide-field (23 arcmin by 23 arcmin) BVI photometry of the
intermediate metallicity ([Fe/H]=-1.3) Galactic globular cluster M12. Using
observed values (and ranges of values) for the cluster metallicity, reddening,
distance modulus, and age we compare these data to recent alpha-enhanced
stellar evolution models for low mass metal-poor stars. We describe several
methods of making comparisons between theoretical and observed luminosity
functions in order to isolate the evolutionary timescale information the
luminosity functions contain. We find no significant evidence of excesses of
stars on the red giant branch, although the morphology of the subgiant branch
in the observed luminosity function does not match theoretical predictions in a
satisfactory way. Current uncertainties in Teff-color transformations (and
possibly also in other physics inputs to the models) make more detailed
conclusions about the subgiant branch morphology impossible. Given the recent
constraints on cluster ages from the WMAP experiment (Spergel et al. 2003), we
find that good fitting models that do not include He diffusion (both
color-magnitude diagrams and luminosity functions) are too old (by
approximately 1-2 Gyr) to adequately represent the cluster luminosity function.
The inclusion of helium diffusion in the models provides an age reduction
(compared to non-diffusive models) that is consistent with the age of the
universe being 13.7+/-0.2 Gyr (Bennett et al. 2003).


title: The case for non-gaussianity on cluster scales

abstract:
  We address whether possible scale-dependent deviations from gaussianity in
the primordial density field that are consistent with the cosmic microwave
background observations could explain the apparent excess of early cluster
formation at high redshift. Using two phenomenological non-gaussian models we
find that at fixed normalisation to the observed local abundance of massive
clusters, the protoclusters observed at z~4 are significantly more likely to
develop in strongly non-gaussian models than in the gaussian paradigm. We
compute the relative z<1 evolution of X-ray cluster counts in the non-gaussian
case with respect to the gaussian expectation, and the relative excess
contribution to the CMB power spectrum due to the integrated thermal SZ effect.
We find that both the observed hints of an unexpectedly slow evolution in the
X-ray counts and the excess power at high l that may have been observed by CMB
interferometers can also be reproduced in our non-gaussian simulations.


title: High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps

abstract:
  We explore the pulsar slot gap electrodynamics up to very high altitudes,
where for most relatively rapidly rotating pulsars both the standard
small-angle approximation and the assumption that the magnetic field lines are
ideal stream lines break down. We address the importance of the electrodynamic
conditions at the slot gap boundaries and the occurrence of a steady-state
drift of charged particles across the slot gap field lines at very high
altitudes. These boundary conditions and the deviation of particle trajectories
from stream lines determine the asymptotic behavior of the scalar potential at
all radii from the polar cap to near the light cylinder. As a result, we
demonstrate that the steady-state accelerating electric field must approach a
small and constant value at high altitude above the polar cap. This parallel
electric field is capable of maintaining electrons moving with high Lorentz
factors (a few times 10^7) and emitting curvature gamma-ray photons up to
nearly the light cylinder. By numerical simulations, we show that primary
electrons accelerating from the polar cap surface to high altitude in the slot
gap along the outer edge of the open field region will form caustic emission
patterns on the trailing dipole field lines. Acceleration and emission in such
an extended slot gap may form the physical basis of a model that can
successfully reproduce some pulsar high-energy light curves.


title: Properties of Cluster Radio Emission

abstract:
  Relevant studies of the non-thermal components of the intracluster medium are
performed at radio wavelengths. A number of clusters, indeed, exhibits
cluster-wide diffuse radio emission, which is indication of the existence of
large scale magnetic fields and of relativistic electrons in the cluster
volume. There is strong evidence that the presence of diffuse radio emission is
related to cluster merger processes. The details of the halo-merger connection
are discussed and a brief outline of current models of halo formation is
presented.


title: Detection of CO J=1-0 in the z=3.79 radio galaxy 4C60.07

abstract:
  We report on the detection of the lowest CO J = 1 - 0 transition in the
powerful high-redshift radio galaxy 4C60.07 at z = 3.79. The CO emission is
distributed in two spatially and kinematically distinct components as was
previously known from the observations of the higher excitation CO J = 4 - 3
line. The total molecular gas mass in 4C60.07 inferred from the CO J = 1 - 0
emission is M(H_2) = 1.3 x 10^11 M_sun, sufficient to fuel the inferred
star-formation rate of ~1600 M_sun yr^-1 for 10^8 yrs. From our high-resolution
CO J = 1 - 0 VLA maps we find the dynamical mass of 4C60.07 to be comparable to
that of a giant elliptical at the present time. A significant fraction of the
mass is in the form of molecular gas suggesting that 4C60.07 is in an early
state of its evolution. The merging nature of 4C60.07 along with its large
dynamical mass imply that this system is a giant elliptical caught in its
formative stages.


title: Flickering variability of T Coronae Borealis

abstract:
  We present electro-photometric UBV and high-speed U-band flickering
observations of the recurrent nova T CrB during a period when its U brightness
varies by more than 2 mag. The V band is dominated by the ellipsoidal
variability of the red giant, however, the variability of the hot component
also causes 0.15 mag variations in V. We define a set of parameters which
characterise the flickering. The Fourier spectra of all 27 nights are similar
to each other. The power spectral density of the variations has a power law
component (f^{-1.46} on average). We do not detect a dependence of the Fourier
spectra and autocorrelation function on the brightness of the object. Having
subtracted the contribution of the red giant, we show that the flickering
amplitude correlates with the average flux of the accreting component. A
comparison with CH Cyg and MWC 560 indicates that the flickering of T CrB is
more stable (at least during the time of our observations), than that in the
jet-ejecting symbiotic stars. The data are available in electronic form from
the authors.


title:
Cosmological parameter estimation using Very Small Array data out to
  l=1500

abstract:
  We estimate cosmological parameters using data obtained by the Very Small
Array (VSA) in its extended configuration, in conjunction with a variety of
other CMB data and external priors. Within the flat $\Lambda$CDM model, we find
that the inclusion of high resolution data from the VSA modifies the limits on
the cosmological parameters as compared to those suggested by WMAP alone, while
still remaining compatible with their estimates. We find that $\Omega_{\rm
b}h^2=0.0234^{+0.0012}_{-0.0014}$, $\Omega_{\rm
dm}h^2=0.111^{+0.014}_{-0.016}$, $h=0.73^{+0.09}_{-0.05}$, $n_{\rm
S}=0.97^{+0.06}_{-0.03}$, $10^{10}A_{\rm S}=23^{+7}_{-3}$ and
$\tau=0.14^{+0.14}_{-0.07}$ for WMAP and VSA when no external prior is
included.On extending the model to include a running spectral index of density
fluctuations, we find that the inclusion of VSA data leads to a negative
running at a level of more than 95% confidence ($n_{\rm run}=-0.069\pm 0.032$),
something which is not significantly changed by the inclusion of a stringent
prior on the Hubble constant. Inclusion of prior information from the 2dF
galaxy redshift survey reduces the significance of the result by constraining
the value of $\Omega_{\rm m}$. We discuss the veracity of this result in the
context of various systematic effects and also a broken spectral index model.
We also constrain the fraction of neutrinos and find that $f_{\nu}< 0.087$ at
95% confidence which corresponds to $m_\nu<0.32{\rm eV}$ when all neutrino
masses are the equal. Finally, we consider the global best fit within a general
cosmological model with 12 parameters and find consistency with other analyses
available in the literature. The evidence for $n_{\rm run}<0$ is only marginal
within this model.


title:
Time Variation in the Radio Flux Density from the Bipolar Ultracompact H
  II Region NGC 7538 IRS1

abstract:
  We present high angular resolution ($\sim0\rlap.{''}1$-$0\rlap.{''}4$) VLA
observations at 2 and 6 cm made in 1983, 1986, and 1995 toward the ultracompact
bipolar H II region NGC 7538 IRS1. We find, at both wavelengths, clear evidence
of a decrease in the emission from the lobes. This decrease, of orden 20-30%,
has not been observed previously in any ultracompact H II region. Most likely,
it is due to recombination of the ionized gas in the lobes as a result of a
decrease in the available ionizing photon flux. It is unclear if this decrease
in the ionizing photon flux is due to an intrinsic change in the exciting star
or to increased absorption of ionizing photons in the optically-thick core of
the nebula.


title:
A Huge Drop in X-ray Luminosity of the Non-Active Galaxy
  RXJ1242.6-1119A, and First Post-Flare Spectrum - Testing the Tidal Disruption
  Scenario

abstract:
  It has been suggested that an unavoidable consequence of the existence of
supermassive black holes, and the best diagnostic of their presence in
non-active galaxies, would be occasional tidal disruption of stars captured by
the black holes. These events manifest themselves in form of luminous flares
powered by accretion of debris from the disrupted star into the black hole.
  Candidate events among optically non-active galaxies emerged in the past few
years. For the first time, we have looked with high spatial and spectral
resolution at one of these most extreme variability events ever recorded among
galaxies. Here, we report measuring a factor ~200 drop in luminosity of the
X-ray source RXJ 1242-1119 with the X-ray observatories Chandra and XMM-Newton,
and perform key tests of the favored outburst scenario, tidal disruption of a
star by a supermassive black hole. We show that the detected `low-state'
emission has properties such that it must still be related to the flare. The
power-law shaped post-flare X-ray spectrum indicates a `hardening' compared to
outburst. The inferred black hole mass, the amount of liberated energy, and the
duration of the event favor an accretion event of the form expected from the
(partial or complete) tidal disruption of a star (abstract abbreviated).