title:
Hubble Space Telescope images of submillimeter sources: large, irregular
  galaxies at high redshift

abstract:
  We present new Hubble Space Telescope STIS, high-resolution optical imaging
of a sample of 13 submillimeter (submm) luminous galaxies, for which the
optical emission has been pinpointed either through radio-1.4 GHz or millimeter
interferometry. We find a predominance of irregular and complex morphologies in
the sample, suggesting that mergers are likely common for submm galaxies. The
component separation in these objects are on average a factor two larger than
local galaxies with similarly high bolometric luminosities. The sizes and star
formation rates of the submm galaxies are consistent with the maximal star
formation rate densities of 20 Msun kpc^{-2} in local starburst galaxies
(Lehnert & Heckman 1996). We derive quantitative morphological information for
the optical galaxies hosting the submm emission; total and isophotal
magnitudes, Petrosian radius, effective radius, concentration, aspect ratio,
surface brightness, and asymmetry. We compare these morphological indices with
those of other galaxies lying within the same STIS images. Most strikingly, we
find ~70% of the submm galaxies to be extraordinarily large and elongated
relative to the field population, regardless of optical magnitude. Comparison
of the submm galaxy morphologies with those of optically selected galaxies at
z~2-3 reveal the submm galaxies to be a morphologically distinct population,
with generally larger sizes, higher concentrations and more prevalent
major-merger configurations.


title:
Evidence for a Major Merger Origin of High Redshift Sub-millimeter
  Galaxies

abstract:
  Sub-mm detected galaxies located at redshifts $z > 1$ host a major fraction
of the bolometric luminosity at high redshifts due to thermal emission from
heated dust grains, yet the nature of these objects remains a mystery. The
major problem in understanding their origin is whether the dust heating
mechanism is predominantly caused by star formation or active galactic nuclei,
and what triggered this activity. We address this issue by examining the
structures of a sample of 11 sub-mm galaxies imaged with STIS on the Hubble
Space Telescope. We argue that ~61pm21% of these sub-mm sources are undergoing
an active major merger using the CAS quantitative morphological system. We rule
out at ~5sigma confidence that these sub-mm galaxies are normal Hubble types at
high redshift. This merger fraction appears to be higher than for Lyman-break
galaxies undergoing mergers at similar redshifts. Using reasonable constraints
on the stellar masses of Lyman-Break galaxies and these sub-mm sources, we
further argue that at redshifts z~2-3 systems with high stellar masses are more
likely than lower mass galaxies to be involved in major mergers.


title:
Cosmic ray production in supernova remnants including reacceleration:
  the secondary to primary ratio

abstract:
  We study the production of cosmic rays (CRs) in supernova remnants (SNRs),
including the reacceleration of background galactic cosmic rays (GCRs) - thus
refining the early considerations by Blandford & Ostriker (1980) and Wandel et
al. (1987) - and the effects of the nuclear spallation inside the sources (the
SNRs). This combines for the first time nuclear spallation inside CR sources
and in the diffuse interstellar medium, as well as reacceleration, with the
injection and subsequent acceleration of suprathermal particles from the
postshock thermal pool. Selfconsistent CR spectra are calculated on the basis
of the nonlinear kinetic model. It is shown that GCR reacceleration and CR
spallation produce a measurable effect at high energies, especially in the
secondary to primary (s/p) ratio, making its energy-dependence substantially
flatter than predicted by the standard model. Quantitatively, the effect
depends strongly upon the density of the surrounding circumstellar matter. GCR
reacceleration dominates secondary CR production for a low circumstellar
density. It increases the expected s/p ratio substantially and flattens its
spectrum to an almost energy-independent form for energies larger than 100
GeV/n if the supernovae explode on average into a hot dilute medium with
hydrogen number density $N_H=0.003$cm$^{-3}$. The contribution of CR spallation
inside SNRs to the s/p ratio increases with increasing circumstellar density
and becomes dominant for $N_H\gsim 1$ cm$^{-3}$, leading at high energies to a
flat s/p ratio which is only by a factor of three lower than in the case of the
hot medium. Measurements of the boron to carbon ratio at energies above 100
GeV/n could be used in comparison with the values predicted here as a
consistency test for the supernova origin of the GCRs.


title:
The Millennium Galaxy Catalogue: Star counts and the Structure of the
  Galactic Stellar Halo

abstract:
  We derive a star catalogue generated from the images taken as part of the
37.5 sq. deg Millennium Galaxy Catalogue. These data, alone and together with
colours gained from the Sloan Digital Sky Survey Early Data Release, allow the
analysis of faint star counts (B(MGC) < 20) at high Galactic latitude (41 < b <
63), as a function of Galactic longitude (239 < l < 353). We focus here on the
inner stellar halo, providing robust limits on the amplitude of substructure
and on the large-scale flattening. In line with previous results, the thick
disk, an old, intermediate-metallicity population, is clearly seen in the
colour-magnitude diagram. We find that the Galactic stellar halo within ~10 kpc
(the bulk of the stellar mass) is significantly flattened, with an axial ratio
of (c/a) =0.56 +/- 0.01, again consistent with previous results. Our analysis
using counts-in-cells, angular correlation functions and the Lee 2D statistic,
confirms tidal debris from the Sagittarius dwarf but finds little evidence for
other substructure in the inner halo, at heliocentric distances of < 5 kpc.
This new quantification of the smoothness in coordinate space limits the
contribution of recent accretion/disruption to the build-up of the bulk of the
stellar halo.


title: Chandra Discovery of an X-ray Jet and Lobes in 3C 15

abstract:
  We report the Chandra detection of an X-ray jet in 3C 15. The peak of the
X-ray emission in the jet is 4.1'' (a projected distance of 5.1 kpc) from the
nucleus, and coincident with a component previously identified in the radio and
optical jets. We examine four models for the X-ray jet emission: (I) weak
synchrotron cooling in equip., (II) moderate synchrotron cooling in equip.,
(III) weak synchrotron plus SSC cooling, and (IV) moderate synchrotron plus SSC
cooling. We argue that case (II) can most reasonably explain the overall
emission from knot C. Case (III) is also possible, but requires a large
departure from equipartition and for the jet power to be comparable to that of
the brightest quasars. Diffuse X-ray emission has also been detected,
distributed widely over the full extent (63kpc x 25kpc) of the radio lobes. We
compare the total energy contained in the lobes with the jet power estimated
from knot C, and discuss the energetic link between the jet and the lobes. We
argue that the fueling time (t_fuel) and the source age (t_src) are comparable
for case (II), whereas t_fuel << t_src is likely for case (III). The latter may
imply that the jet has a very small filling factor, ~10^{-3}. We consider the
pressure balance between the thermal galaxy halo and non-thermal relativistic
electrons in the radio lobes. Finally, we show that the X-ray emission from the
nucleus is not adequately fitted by a simple absorbed power-law model, but
needs an additional power-law with heavy absorption intrinsic to the source.
Such a high column density is consistent with the presence of a dense, dusty
torus which obscures the quasar nucleus.


title:
Dynamical evolution of globular cluster systems in clusters of galaxies
  I. The case of NGC 1404 in the Fornax cluster

abstract:
  We investigate, via numerical simulations, the tidal stripping and accretion
of globular clusters (GCs). In particular, we focus on creating models that
simulate the situation for the GC systems of NGC 1404 and NGC 1399 in the
Fornax cluster, which have poor (specific frequency $S_{\rm N}$ $\sim$ 2) and
rich ($S_{\rm N}$ $\sim$ 10) GC systems respectively. We initially assign NGC
1404 in our simulation a typical $S_{\rm N}$ ($\sim$ 5) for cluster
ellipticals, and find that its GC system can only be reduced through stripping
to the presently observed value, if its orbit is highly eccentric (with orbital
eccentricity of $>$ 0.5) and if the initial scale length of the GCs system is
about twice as large as the effective radius of NGC 1404 itself. These stripped
GCs can be said to have formed a `tidal stream' of intracluster globular
clusters (ICGCs) orbiting the centre of Fornax cluster (many of which would be
assigned to NGC 1399 in an imaging study). The physical properties of these GCs
(e.g., number, radial distribution) depend on the orbit and initial
distribution of GCs in NGC 1404. Our simulations also predict a trend for
$S_{\rm N}$ to rise with increasing clustercentric distance - a trend for which
there is some observational support in the Fornax cluster.


title:
Instabilities of Spiral Shocks I: Onset of Wiggle Instability and its
  Mechanism

abstract:
  We found that loosely wound spiral shocks in an isothermal gas disk caused by
a non-axisymmetric potential are hydrodynamically unstable, if the shocks are
strong enough. High resolution, global hydrodynamical simulations using three
different numerical schemes, i.e. AUSM, CIP, and SPH, show similarly that
trailing spiral shocks with the pitch angle of larger than ~10 deg wiggle, and
clumps are developed in the shock-compressed layer. The numerical simulations
also show clear wave crests that are associated with ripples of the spiral
shocks. The spiral shocks tend to be more unstable in a rigidly rotating disk
than in a flat rotation. This instability could be an origin of the secondary
structures of spiral arms, i.e. the spurs/fins, observed in spiral galaxies. In
spite of this local instability, the global spiral morphology of the gas is
maintained over many rotational periods. The Kelvin-Helmholtz (K-H) instability
in a shear layer behind the shock is a possible mechanism for the wiggle
instability. The Richardson criterion for the K-H stability is expressed as a
function of the Mach number, the pitch angle, and strength of the background
spiral potential. The criterion suggests that spiral shocks with smaller pitch
angles and smaller Mach numbers would be more stable, and this is consistent
with the numerical results.


title: Evolution of Dust-to-Metal Ratio in Galaxies

abstract:
  This paper investigates the evolution of the dust-to-metal ratio in galaxies
based on a simple evolution model for the amount of metal and dust with infall.
We take into account grain formation in stellar mass-loss gas, grain growth by
the accretion of metallic atoms in a cold dense cloud, and grain destruction by
SNe shocks. Especially, we propose that the accretion efficiency is independent
of the star-formation history. This predicts various evolutionary tracks in the
metallicity ($Z$)--dust-to-gas ratio ($\cal D$) plane depending on the
star-formation history. In this framework, the observed linear $Z$--$\cal D$
relation of nearby spiral galaxies can be interpreted as a sequence of a
constant galactic age. We emphasize that an observational study of the
$Z$--$\cal D$ relation of galaxies at $z\sim 1$ is very useful to constrain the
efficiencies of dust growth and destruction. We also suggest that the
  Lyman break galaxies at $z\sim 3$ have a very low dust-to-metal ratio,
typically $\ltsim 0.1$. Although the effect of infall on the evolutionary
tracks in the $Z$--$\cal D$ plane is quite small, the dispersion of the infall
rate can disturb the $Z$--$\cal D$ relation with a constant galactic age.


title: Far-infrared detection of 17OH towards Sagittarius B2

abstract:
  The frequencies and line strengths of the 2Pi3/2 J=5/2-3/2 rotational
transition of 17OH have been calculated from an analysis of its far-infrared
laser magnetic resonance spectrum. These results have been used to make the
first detection of a pure rotational transition of 17OH in the ISM. Two
resolved components of this transition appear in absorption towards the giant
molecular cloud Sagittarius B2, which was observed at a spectral resolution of
33 km/s with the Fabry-Perot mode of the ISO Long Wavelength Spectrometer. The
corresponding transition of 18OH was also observed and its line shape was
modelled using HI measurements. The 18O/17O ratio of 3.5 was then used to
compare this with the observed 17OH line shape.


title:
Near-Infrared Colors of Gamma-Ray Burst Afterglows and Cosmic
  Reionization History

abstract:
  Using the near-infrared (NIR) observations of the afterglows of the high
redshift ($5 \la z \la 25$) gamma-ray bursts (GRBs) which will be detected by
the {\it Swift} satellite, we discuss a way to study the cosmic reionization
history. In principle the details of the cosmic reionization history are well
imprinted in the NIR spectra of the GRB afterglows. However the spectroscopy
with a space telescope is required to obtain such an information for a very
high redshift ($z\ga 15$) unless the neutral fraction of the high-$z$ universe
is less than $10^{-6}$. The broad-band photometry has the higher sensitivity
than that of the spectroscopy, so that the NIR photometric follow-up of the GRB
afterglows is very promising to examine the cosmic reionization history. A few
minutes exposure with a 8-m class ground-based telescope of the afterglow of
the high-$z$ GRBs will reveal how many times the reionization occurred in the
universe.


title: On the stability of self-gravitating protoplanetary discs

abstract:
  It has already been shown, using a local model, that accretion discs with
cooling times t_cool <= 3 Omega^-1 fragment into gravitationally bound objects,
while those with cooling times t_cool > 3 Omega^-1 evolve into a quasi-steady
state. We present results of three-dimensional simulations that test if the
local result still holds globally. We find that the fragmentation boundary is
close to that determined using the local model, but that fragmentation may
occur for longer cooling times when the disc is more massive or when the mass
is distributed in such a way as to make a particular region of the disc more
susceptible to the growth of the gravitational instability. These results have
significant implications for the formation of of gaseous planets in
protoplanetary discs and also for the redistribution of angular momentum which
could be driven by the presence of relatively massive, bound objects within the
disc.


title:
Correlated Isocurvature Fluctuation in Quintessence and Suppressed CMB
  Anisotropies at Low Multipoles

abstract:
  We consider cosmic microwave background (CMB) anisotropy in models with
quintessence taking into account of isocurvature fluctuation in the
quintessence. It is shown that, if the primordial fluctuation of the
quintessence has a correlation with the adiabatic density fluctuations, CMB
angular power spectrum $C_l$ at low multipoles can be suppressed without
affecting $C_l$ at high multipoles. Possible scenario of generating correlated
mixture of the quintessence and adiabatic fluctuations is also discussed.


title: Interaction of Galaxies with the ICM

abstract:
  In recent years a wealth of data and detailed hydrodynamical simulations have
appeared that show the effects of interactions between the ICM and galaxies.
Single dish observations show that cluster galaxies are deficient in their HI
content out to 2 Abell radii. The deficient galaxies tend to be on radial
orbits. Imaging of the HI distribution in individual galaxies shows a
remarkable trend of HI extent with location in the cluster. These trends can be
reproduced in simulations of ram pressure stripping by the ICM using SPH and 3D
hydro-codes. Detailed imaging of individual galaxies shows in some caes
undisturbed old stellar disks, truncated gas disks that are much smaller than
the stellar disks, asymmetric extraplanar gas in the center and enhanced
central star formation. These phenomena have all been predicted by
hydrodynamical simulations. Optical imaging and spectroscopic surveys show that
small HI disks go together with truncated star forming disks, that HI
deficiency correlates with suppressed star formation rates and that the spatial
extent of HI deficiency in clusters is matched by or even surpassed by the
extent of reduced star formation rates. Recent volume limited HI imaging
surveys of clusters in the local universe show that most gas rich galaxies are
located in groups and subclumps, that yet have to fall into the clusters. In
these groups we see much evidence for interactions between gas rich galaxies.


title:
Effects of interstellar and solar wind ionized helium on the interaction
  of the solar wind with the local interstellar medium

abstract:
  The Sun is moving through a warm ($\sim$6500 K) and partly ionized local
interstellar cloud (LIC) with a velocity of $\sim$26 km/s. Recent measurements
of the ionization of the LIC (Wolff et al., 1999) suggest that interstellar
helium in the vicinity of the Sun is 30-40 % ionized, while interstellar
hydrogen is less ionized. Consequently, interstellar helium ions contribute up
to 50% of the total dynamic pressure of the ionized interstellar component. Up
to now interstellar helium ions have been ignored in existing models of the
heliospheric interface. In this paper we present results of a new model of the
solar wind interaction with the interstellar medium, which takes into account
interstellar helium ions. Using results of this model we find that the
heliopause, termination and bow shocks are closer to the Sun when compared to
the model results that ignore $He$ ions. The influence of interstellar helium
ions is partially compensated by solar wind alpha particles, which are taken
into account in our new model as well. Finally, we apply our new model to place
constraints on the plausible location of the termination shock.


title: Model of the tail region of the heliospheric interface

abstract:
  Physical processes in the tail of the solar wind interaction region with the
partially ionized local interstellar medium are investigated in a framework of
the self-consistent kinetic-gas dynamic model. It is shown that the charge
exchange process of the hydrogen atoms with the plasma protons results in
suppression of the gas dynamic instabilities and disappearance the contact
discontinuity at sufficiently (~3000 AU) large distances from the Sun. The
solar wind plasma temperature decreases and, ultimately, the parameters of the
plasma and hydrogen atoms approach to the corresponding parameters of the
unperturbed interstellar medium at large heliocentric distances.


title:
Simultaneous observations of the quasar 3C 273 with INTEGRAL, XMM-Newton
  and RXTE

abstract:
  INTEGRAL has observed the bright quasar 3C 273 on 3 epochs in January 2003 as
one of the first observations of the open programme. The observation on January
5 was simultaneous with RXTE and XMM-Newton observations. We present here a
first analysis of the continuum emission as observed by these 3 satellites in
the band from 3 keV to 500 keV. The continuum spectral energy distribution of
3C 273 was observed to be weak and steep in the high energies during this
campaign. We present the actual status of the cross calibrations between the
instruments on the three platforms using the calibrations available in June
2003.


title: High speed outflows driven by the 30 Doradus starburst

abstract:
  Echelle spectroscopy has been carried out towards a sample region of the halo
of the giant HII region 30 Doradus in the Large Magellanic Cloud. This new
kinematical data is the amongst the most sensitive yet obtained for this nebula
and reveals a wealth of faint, complex high speed features. These are
interpreted in terms of localised shells due to individual stellar winds and
supernova explosions, and collections of discrete knots of emission that still
retain the velocity pattern of the giant shells from which they fragmented. The
high speed velocity features may trace the base of the superwind that emanates
from the 30 Doradus starburst, distributed around the super star cluster R136.


title:
Constraints on Lorentz Invariance Violating Quantum Gravity and Large
  Extra Dimensions Models using High Energy Gamma Ray Observations

abstract:
  Observations of the multi-TeV spectra of the nearby BL objects Mkn 421 and
Mkn 501 exhibit the high energy cutoffs predicted to be the result of
intergalactic annihilation interactions, primarily with infrared photons having
a flux level as determined by various astronomical observations. After
correction for this absorption effect, the derived intrinsic spectra of these
multi-TeV sources can be explained within the framework of simple synchrotron
self-Compton emission models. Stecker and Glashow have shown that the existence
of such annihilations via electron-positron pair production interactions up to
an energy of 20 TeV puts strong constraints on Lorentz invariance violation.
Such constraints have important implications for Lorentz invariance violating
(LIV) quantum gravity models as well as LIV models involving large extra
dimensions. We also discuss the implications of observations of high energy
gamma-rays from the Crab Nebula on constraining quantum gravity models.


title: Pulsar Populations and Unidentified Gamma-Ray Sources

abstract:
  The EGRET telescope on the Compton Gamma-Ray Observatory detected over 200
sources and the majority of these are still unidentified. At least three
subpopulations of EGRET sources have been associated with the Galaxy: bright
sources lying along the Galactic plane, weaker sources spatially correlated
with the Gould Belt and a high-latitude, halo population. Many of these sources
may be pulsars and there are more than two-dozen radio pulsars in or near EGRET
source error boxes, most of them recently discovered in the Parkes Multibeam
Survey. We present results from several population synthesis studies of pulsars
in the Galaxy, which predict the number of pulsars detected by gamma-ray and
radio surveys assuming models for the high-energy emission beam and its
relation to the radio beam. Future gamma-ray pulsar detections by AGILE and
GLAST together with the recent large rise in the radio pulsar population will
give greatly improved statistics. The relative numbers of radio and gamma-ray
pulsars detected in the plane and in the Gould Belt populations will provide an
important discriminator between models of high-energy emission and will
profoundly affect the numbers and birth rate of pulsars in the Galaxy.


title:
A New 17F(p,gamma)18Ne Reaction Rate and Its Implications for Nova
  Nucleosynthesis

abstract:
  Proton capture by 17F plays an important role in the synthesis of nuclei in
nova explosions. A revised rate for this reaction, based on a measurement of
the 1H(17F,p)17F excitation function using a radioactive 17F beam at ORNL's
Holifield Radioactive Ion Beam Facility, is used to calculate the
nucleosynthesis in nova outbursts on the surfaces of 1.25 and 1.35 solar mass
ONeMg white dwarfs and a 1.00 solar mass CO white dwarf. We find that the new
17F(p,gamma)18Ne reaction rate changes the abundances of some nuclides (e.g.,
17O) synthesized in the hottest zones of an explosion on a 1.35 solar mass
white dwarf by more than a factor of 10,000 compared to calculations using some
previous estimates for this reaction rate, and by more than a factor of 3 when
the entire exploding envelope is considered. In a 1.25 solar mass white dwarf
nova explosion, this new rate changes the abundances of some nuclides
synthesized in the hottest zones by more than a factor of 600, and by more than
a factor of 2 when the entire exploding envelope is considered. Calculations
for the 1.00 solar mass white dwarf nova show that this new rate changes the
abundance of 18Ne by 21%, but has negligible effect on all other nuclides.
Comparison of model predictions with observations is also discussed.


title:
Microphysics of Shock Acceleration from Observations of X-Ray
  Synchrotron Emission from Supernova Remnants

abstract:
  Recent observations of non-thermal X-rays from supernova remnants have been
attributed to synchrotron radiation from the loss-steepened tail of a
non-thermal distribution of electrons accelerated at the remnant blast wave. In
diffusive shock acceleration, the maximum particle energy depends on the
energy-dependence of the diffusion coefficient kappa. Most work on shock
acceleration has made the plausible assumption that kappa is proportional to
the particle gyroradius, implying a wavelength-independent spectrum of MHD
turbulence, where Kolmogorov or Kraichnan spectra might be more physically
plausible. I derive the wave-spectrum-dependence of the maximum electron energy
resulting from limitations due to radiative (synchrotron and inverse-Compton)
losses and to finite remnant age (or size). I then exhibit calculations of
synchrotron X-ray spectra, and model images, for supernova remnants as a
function of spectrum, and compare to earlier results. Spectra can be
considerably altered, and images are dramatically different, for Kolmogorov or
Kraichnan spectra of turbulence. The predicted images are quite unlike observed
remnants, suggesting that the turbulence near SNRs is generated by the
high-energy particles themselves.


title: Electromagnetic signals from planetary collisions

abstract:
  Planet-planet collisions are expected during the early stages of the
formation of extra-solar planets, and are also possible in mature planetary
systems through secular planet-planet perturbations. We investigate the
electromagnetic signals accompanied with these planetary collisions and their
event rate, and explore the possibility of directly detecting such events. A
typical Earth-Jupiter collision would give rise to a prompt EUV-soft-X-ray
flash lasting for hours and a bright IR afterglow lasting for thousands of
years. It is suggested that with the current and forthcoming observational
technology and facilities, some of these collisional flashes or the
post-collision remnants could be discovered.


title: Long Term Studies of Z sources with HEXTE/RXTE

abstract:
  We have analyzed the long pointed observations of the Z sources in the Rossi
X-Ray Timing Explorer (RXTE) public archive to study the high energy emission
in those sources. Our analysis is concentrated on the High Energy X--Ray Timing
Experiment (HEXTE) waveband, since we are primarily interested in studying the
hard X-ray (i.e., E > 20 keV) production in those sources. We give here the
preliminary results of this ongoing study. We have found no hard X-ray tails
(besides Sco X-1) in our database from any of the Z sources, i.e., GX 349+2 (<
7.9 x 10^-5 photons cm^-2 s^-1, 3 sigma, 50-150 keV), Cyg X-2 (< 8.4 x 10^-5
photons cm^-2 s^-1, 3 sigma, 50-150 keV), GX 17+2 (< 4.2 x 10^-5 photons cm^-2
s^-1, 3 sigma, 50-150 keV), GX 5-1 (< 2.1 x 10^-5 photons cm^-2 s^-1, 3 sigma,
50-150 keV), and Gx 340+0 (< 6.0 x 10^-5 photons cm^-2 s^-1, 3 sigma, 50-150
keV). From the point of view of HEXTE/RXTE observations shown here, the
production of hard X-ray tails in Z sources is a process triggered when special
conditions are fulfilled. One of these conditions, as derived from our
analysis, is a threshold of ~ 4 x 10^36 erg s^-1 for the luminosity of the
source's thermal component.


title: Chandra Observations of SNR 1987A

abstract:
  We report on the results of our monitoring program of the X-ray remnant of
supernova 1987A with the {\it Chandra X-Ray Observatory}. We have performed two
new observations during the {\it Chandra} Cycle 3 period, bringing the total to
six monitoring observations over the past three years. These six observations
provide a detailed time history of the birth of a new supernova remnant in
X-rays. The high angular resolution images indicate that soft X-ray bright
knots are associated with the optical spots, while hard X-ray features are
better correlated with radio images. We interpret this in terms of a model in
which fast shocks propagating through the circumstellar HII region produce the
hard X-ray and radio emission, while the soft X-ray and optical emission arise
in slower shocks entering into dense knots in the circumstellar inner ring. New
observations begin to show changes in the morphology that may herald a new
stage in the development of this incipient supernova remnant. The observed
X-ray fluxes increase by nearly a factor of three over the last 30 months. The
X-ray remnant is expanding at a velocity of $\sim$5000 km s$^{-1}$.


title: |V|: New insight into the circular polarization of radio pulsars

abstract:
  We present a study of single pulses from nine bright northern pulsars to
investigate the behaviour of circular polarisation, V. The observations were
conducted with the Effelsberg 100-m radio telescope at 1.41 GHz and 4.85 GHz
and the Westerbork radio telescope at 352 MHz. For the first time, we present
the average profile of the absolute circular polarisation |V| in the single
pulses. We demonstrate that the average profile of |V| is the distinguishing
feature between pulse components that exhibit low V in the single pulses and
components that exhibit high V of either handedness, despite both cases
resulting in a low mean. We also show that the |V| average profile remains
virtually constant with frequency, which is not generally the case for V,
leading us to the conclusion that |V| is a key quantity in the pulsar emission
problem.


title: On the Origin of X-ray Emission From Millisecond Pulsars in 47 Tuc

abstract:
  The observed spectra and X-ray luminosities of millisecond pulsars in 47 Tuc
can be interpreted in the context of theoretical models based on strong, small
scale multipole fields on the neutron star surface. For multipole fields that
are relatively strong as compared to the large scale dipole field, the emitted
X-rays are thermal and likely result from polar cap heating associated with the
return current from the polar gap. On the other hand, for weak multipole
fields, the emission is nonthermal and results from synchrotron radiation of
$e^{\pm}$ pairs created by curvature radiation. The X-ray luminosity, $L_x$, is
related to the spin down power, $L_{sd}$, expressed in the form $L_x \propto
L^{\beta}_{sd}$ with $\beta \sim 0.5$ and $\sim 1$ for strong and weak
multipole fields respectively. If the polar cap size is of the order of the
length scale of the multipole field, $s$ and $\beta \sim 0.5$, the polar cap
temperature is $\sim 3 \times 10^6 K (\frac{L_{sd}}{10^{34}erg s^{-1}})^{1/8}
(\frac{s}{3\times 10^4 cm})^{-1/2}$.
  A comparison of the X-ray properties of millisecond pulsars in globular
clusters and in the Galactic field suggests that the emergence of relatively
strong small scale multipole fields from the neutron star interior may be
correlated with the age and evolutionary history of the underlying neutron
star.


title: High-Energy Radiation from Pulsars : A Three Dimensional Model Approach

abstract:
  We suggest that some observational features of high-energy radiation from
pulsars should be explained in terms of three dimensional geometric models,
e.g. the phase-resolved X-ray and $\gamma$-ray spectra and the energy dependent
light curves from various pulsars. In this paper, we present a three
dimensional pulsar outer-magnetospheric gap model to explain these
observational features. The outer-magnetospheric gap is proposed to form near
the null charged surface and extend toward the light cylinder. The other two
geometric dimensions of the outer-magnetospheric gap, i.e. the vertical size
and the azimuthal extension can be determined self-consistently. We apply this
model to explain the observed phase-dependent spectra and the energy-dependent
light curves of various pulsars.


title: Microvariability in the optical polarization of 3C279

abstract:
  We present results of a microvariability polarization study in the violently
variable quasar 3C279. We have resolved the polarization curves in the V band
for this object down to timescales of minutes. We found two main components in
the evolution of the degree of linear polarization, one consisting of a flicker
with timescales of several tens of minutes and other component with far more
significant variations on timescales of a few days. The linear polarization
descended from $\sim 17$ % down to $\sim 8$ % in three nights. The polarization
angle underwent a sudden change of more that 10 degrees in a few hours, perhaps
indicating the injection of a new shock in the jet. The amplitude of the
intranight flickering in the degree of polarization is at the level of $\sim
1$%. These are probably the best sampled polarization data ever obtained for
this object. We also performed IR observations and we provide a follow-up of
the evolution of this source at such energies after the main polarization
outburst.


title: The kinematics of the most oxygen-poor planetary nebula PN G135.9+55.9

abstract:
  PN G135.9+55.9 is a compact, high excitation nebula that has been identified
recently as the most oxygen-poor halo planetary nebula. Given its very peculiar
characteristics and potential implications in the realms of stellar and
Galactic evolution, additional data are needed to firmly establish its true
nature and evolutionary history. Here we present the first long-slit, high
spectral resolution observations of this object in the lines of H$\alpha$ and
He II 4686. The position-velocity data are shown to be compatible with the
interpretation of PN G135.9+55.9 being a halo planetary nebula. In both
emission lines, we find the same two velocity components that characterize the
kinematics as that of an expanding elliptical envelope. The kinematics is
consistent with a prolate ellipsoidal model with axis ratio about 2:1, a
radially decreasing emissivity distribution, a velocity distribution that is
radial, and an expansion velocity of 30 km/s for the bulk of the material. To
fit the observed line profiles, this model requires an asymmetric matter
distribution, with the blue-shifted emission considerably stronger than the
red-shifted emission. We find that the widths of the two velocity components
are substantially wider than those expected due to thermal motions, but
kinematic structure in the projected area covered by the slit appears to be
sufficient to explain the line widths. The present data also rule out the
possible presence of an accretion disk in the system that could have been
responsible for a fraction of the H$\alpha$ flux, further supporting the
planetary nebula nature of PN G135.9+55.9.


title: Future Astrometry with ALMA to characterise extra-solar planet orbits

abstract:
  The most complete catalogue of nearby stars (Gliese and Jarheiss, 1991) has
been used to search for the stars whose photospheric thermal emission can be
detected by the future millimeter array ALMA. We found that 446 nearby stars
with spectral types ranging from A to M are detectable. A long-term astrometric
observation programme (> 10 yr) of these stars with ALMA (theoretical
astrometric precision = 0.1 milliarcsecond) would be sensitive to wobbles
caused by the gravitational pull of possible unseen planets. Such a programme
would probe minimum planetary masses as low as 0.1 Jupiter for an orbital
period of 10 years. We provide histogrammes of these minimum masses and of ALMA
integration times for these 446 ALMA stars.


title: Physics of Supermassive Disks: Formation and Collapse

abstract:
  Supermassive disks are thought to be precursors of supermassive black holes
that are believed to power quasars and exist at centers of galaxies. Formation
scenarios of such disks are reviewed and it is argued that gas dynamical
schemes are favourable compared to stellar dynamical schemes which could
however be important feeding mechanisms for the growth of the black hole. A new
self-similar model of a collapse of a self-gravitating disk due to radiation
induced stresses applicable to two different situations of radiative viscosity
and Compton drag is presented. The collapse timescale purely due to radiative
viscosity is found to be a fraction of Hubble time, $\tau_\gamma \sim{\sigma_T
c/ (m_p G)} ({L_{edd}/ L}) \simeq 6 \times 10^9$yrs is slow and probably
magnetic fields play an important role before general relativistic effects take
over. A model of self-gravitating disk collapsing due to Compton drag by the
Cosmic Microwave Background is also presented which is found to be effective at
redshifts $1400>z\gsim 300$. It is proposed that the small $\lsim 10^5 \Msun$
objects that form by this mechanism by $z \sim 20$ can merge and coalesce by
dynamical friction to form the high redshift quasars seen. Supermassive stars
which are systems (and could be end products of a supermassive disk phase) en
route to the final collapse are also briefly reviewed.


title: Supernova Neutrino Spectra and Applications to Flavor Oscillations

abstract:
  We study the flavor-dependent neutrino spectra formation in the core of a
supernova (SN) by means of Monte Carlo simulations. A high-statistics neutrino
signal from a galactic SN may contain information that severely constrains the
parameter space for neutrino oscillations. Therefore, reliable predictions for
flavor-dependent fluxes and spectra are urgently needed. In all traditional
hydrodynamic simulations the nu_mu,tau and nu_mu,tau-bar interactions commonly
included are rather schematic. With our Monte Carlo simulations we find that
the most relevant sources for nu_mu,tau and nu_mu,tau-bar are traditionally not
included. In comparing our numerical results for all flavors we find the
standard hierarchy of mean energies nu_e < nu_e-bar < nu_mu,tau, with, however,
very similar values for nu_mu,tau and nu_e-bar. The luminosities of nu_mu,tau
and nu_mu,tau-bar can differ by up to a factor of 2 from L_nue-bar and L_nue,
the latter two are very similar. The Garching Group obtains similar results
from their self-consistent simulation with the full set of interactions. These
results are almost orthogonal to the previous standard picture of exactly equal
luminosities of all flavors and differences in mean energies of up to a factor
of 2. Existing concepts for identifying oscillation effects in a SN neutrino
signal need to be revised. We present two methods for detecting the
earth-matter effect that are rather independent of predictions from SN
simulations.


title: X-ray Evidence of the Common Envelope Phase of V471 Tauri

abstract:
  Chandra Low Energy Transmission Grating Spectrograph observations of the
pre-cataclysmic binary V471 Tau have been used to estimate the C/N abundance
ratio of the K dwarf component for the first time. While the white dwarf
component dominates the spectrum longward of 50 AA, at shorter wavelengths the
observed X-ray emission is entirely due to coronal emission from the K dwarf.
The H-like resonance lines of C and N yield an estimate of their logarithmic
abundance ratio relative to the Sun of [C/N]=-0.38+/-0.15 - half of the
currently accepted solar value. We interpret this result as the first clear
observational evidence for the presumed common envelope phase of this system,
during which the surface of the K dwarf was contaminated by CN-cycle processed
material dredged up into the red giant envelope. We use the measured C/N ratio
to deduce that 0.015-0.04 Msun was accreted by the K dwarf while engulfed, and
show that this is consistent with a recent tentative detection of 13C in the K
dwarf photosphere, and with the measured Li abundance in the scenario where the
red giant companion was Li-rich during the common envelope phase.


title: From the Heart of The Ghoul: C and N Abundances in the Corona of Algol B

abstract:
  Chandra Low Energy Transmission Grating Spectrograph observations of Algol
have been used to determine the abundances of C and N in the secondary star for
the first time. The analysis was performed relative to similar observations of
an adopted "standard" star HR 1099. It is demonstrated that HR 1099 and Algol
are coronal twins in many respects and that their X-ray spectra are very
similar in nearly all details, except for the observed strengths of C and N
lines. The H-like transitions of C and N in the coronae of Algol and HR 1099
demonstrate that the surface abundances of Algol B have been strongly modified
by CN-processing, as shown earlier by Schmitt & Ness (2002). It is found that N
is enhanced in Algol B by a factor of 3 compared to HR 1099. No C lines are
detected in the Algol spectrum, indicating a C depletion relative to HR 1099 by
a factor of 10 or more. These C and N abundances indicate that Algol B must
have lost at least half of its initial mass, and are consistent with
predictions of evolutionary models that include non-conservative mass transfer
and angular momentum loss through magnetic activity. Little or no dredge-up of
material subjected to CN-processing has occurred on the subgiant component of
HR 1099. It is concluded that Fe is very likely depleted in the coronae of both
Algol and HR 1099 relative to their photospheres by 0.5 dex, and C, N and O by
0.3 dex. Instead, Ne is enhanced by up to 0.5 dex.


title: Chemical Fractionation and Abundances in Coronal Plasma

abstract:
  Much of modern astrophysics is grounded on the observed chemical compositions
of stars and the diffuse plasma that pervades the space between stars, galaxies
and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer
atmospheres of stars have demonstrated that these environments are subject to
chemical fractionation in which the abundances of elements can be enhanced and
depleted by an order of magnitude or more. These coronal abundance anomalies
are discussed and some of the physical mechanisms that might be responsible for
producing them are examined. It is argued that coronal abundances can provide
important new diagnostics on physical processes at work in solar and stellar
coronae. It seems likely that other hot astrophysical plasmas will be subject
to similar effects.


title: Star Formation in Extreme Starburst Environments - "Super" Star Clusters

abstract:
  The currently available empirical evidence on the star formation processes in
the extreme, high-pressure environments induced by galaxy encounters, mostly
based on high-resolution Hubble Space Telescope imaging observations, strongly
suggests that star CLUSTER formation is an important and perhaps even the
dominant mode of star formation in the starburst events associated with galaxy
interactions.
  The production of "super star clusters" (SSCs; luminous, compact star
clusters) seems to be a hallmark of intense star formation, particularly in
interacting and starburst galaxies. Their sizes, luminosities, and mass
estimates are entirely consistent with what is expected for young Milky
Way-type globular clusters (GCs). SSCs are important because of what they can
tell us about GC formation and evolution (e.g., initial characteristics and
early survival rates). They are also of prime importance as probes of the
formation and (chemical) evolution of their host galaxies, and of the initial
mass function in the extreme environments required for cluster formation.
Recent evidence lends support to the scenario that Milky Way-type GCs (although
more metal rich), which were once thought to be the oldest building blocks of
galaxies, are still forming today.


title:
White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of
  Finite Entropy Objects

abstract:
  We discuss the mass-radius (M-R) relations for low-mass (M<0.1 Msun) white
dwarfs (WDs) of arbitrary degeneracy and evolved (He, C, O) composition. We do
so with both a simple analytical model and models calculated by integration of
hydrostatic balance using a modern equation of state valid for fully ionized
plasmas. The M-R plane is divided into three regions where either Coulomb
physics, degenerate electrons or a classical gas dominate the WD structure. For
a given M and central temperature, T_c, the M-R relation has two branches
differentiated by the model's entropy content. We present the M-R relations for
a sequence of constant entropy WDs of arbitrary degeneracy parameterized by M
and T_c for pure He, C, and O. We discuss the applications of these models to
the recently discovered accreting millisecond pulsars. We show the relationship
between the orbital inclination for these binaries and the donor's composition
and T_c. In particular we find from orbital inclination constraints that the
probability XTE J1807-294 can accommodate a He donor is approximately 15% while
for XTE J0929-304, it is approximately 35%. We argue that if the donors in
ultracompact systems evolve adiabatically, there should be 60-160 more systems
at orbital periods of 40 min than at orbital periods of 10 min, depending on
the donor's composition.


title:
From Infall to Rotation around Young Stars: The Origin of Protoplanetary
  Disks

abstract:
  The origin of disks surrounding young stars has direct implications for our
understanding of the formation of planetary systems. In the interstellar clouds
from which star form, angular momentum is regulated by magnetic fields,
preventing the spin up of contracting cores. When ~0.03 pc-sized dense cores
decouple from the magnetic field and collapse dynamically, ~10^-3 km/s*pc of
specific angular momentum is locked into the system. A viscous accretion disk
is one of two possible mechanisms available for the necessary redistribution of
angular momentum; the other one is the formation of a multiple stellar system.
Recent observational results involving high-angular resolution observations are
reviewed: the presence of disks deep inside collapsing envelopes; an accretion
shock surrounding a disk; the velocity field in collapsing and slowly rotating
envelopes; a possible transitional object, characterized as a large,
contracting disk; and the velocity field in disks around T Tauri stars.
Observational facilities becoming available over the next several years promise
to offer significant progress in the study of the origin of protoplanetary
disks.


title: An atlas of line profile studies for SU UMa type cataclysmic variables

abstract:
  We present H-alpha line-profile analyses for the seven SU UMa type dwarf
novae AK Cnc, WX Cet, AQ Eri, VW Hyi, RZ Leo, TU Men, and HS Vir. All data sets
are treated in the same manner, applying a sequence of techniques for each
system. The basic ingredients of this sequence are the diagnostic diagram to
determine the zero point of the orbital phase, and Doppler tomography to
visualise the emission distribution. We furthermore introduce a new qualitative
way of to evaluate the Doppler fit, by comparing the line profile of the
reconstructed with the original spectrum in the form of the V/R plot. We
present the results of the analysis in the compact form of an atlas, allowing a
direct comparison of the emission distribution in our targets. Although most of
the data sets were not taken with the intention of a line-profile analysis, we
obtain significant results and are able to indicate the type of the additional
emission in these systems. Our objects should have in principle very similar
physical properties, i.e. they cover only a small range in orbital periods,
mass ratios, and mass-transfer rates. Nevertheless, we find a large variety of
phenomena both with respect to the individual systems and also within
individual data sets of the same object. This includes `canonical' additional
emission components from the secondary star and the bright spot, but also
emission from the leading side of the accretion disc.


title: The Asymptotic Structure of Space-Time

abstract:
  Astronomical observations strongly suggest that our universe is now
accelerating and contains a substantial admixture of dark vacuum energy. Using
numerical simulations to study this newly consolidated cosmological model (with
a constant density of dark energy), we show that astronomical structures freeze
out in the near future and that the density profiles of dark matter halos
approach the same general form. Every dark matter halo grows asymptotically
isolated and thereby becomes the center of its own island universe. Each of
these isolated regions of space-time approaches a universal geometry and we
calculate the corresponding form of the space-time metric.


title: The Discovery of a Twelfth Wolf-Rayet Star in the Small Magellanic Cloud

abstract:
  We report the discovery of a relatively faint (V=15.5) early-type WN star in
the SMC. The line strength and width of He II lambda 4686 emission is similar
to that of the other SMC WNs, and the presense of N V lambda 4603,19 emission
(coupled with the lack of N III) suggests this star is of spectral type
WN3-4.5, and thus is similar in type to the other SMC WRs. Also like the other
SMC WN stars, an early-type absorption spectrum is weakly present. The absolute
magnitude is comparable to that of other (single) Galactic early-type WNs. The
star is located in the Hodge 53 OB association, which is also the home of two
other SMC WNs. This star, which we designate SMC-WR12, was actually detected at
a high significance level in an earlier interference-filter survey, but the
wrong star was observed as part of a spectroscopic followup, and this case of
mistaken identity resulted in its Wolf-Rayet nature not being recognized until
now.


title: The Changing AGN Population

abstract:
  We investigate how the fraction of broad-line sources in the AGN population
changes with X-ray luminosity and redshift. We first construct the rest-frame
hard-energy (2-8 keV) X-ray luminosity function (HXLF) at z=0.1-1 using Chandra
Lockman Hole-Northwest wide-area data, Chandra Deep Field-North 2 Ms data,
other Chandra deep field data, and the ASCA Large Sky Survey data. We find that
broad-line AGNs dominate above 3e43 ergs/s and have a mean luminosity of 1.3e44
ergs/s. Type II AGNs can only become an important component of the X-ray
population at Seyfert-like X-ray luminosities. We then construct z=0.1-0.5 and
z=0.5-1 HXLFs and compare them with both the local HXLF measured from HEAO-1 A2
survey data and the z=1.5-3 HXLF measured from soft-energy (0.5-2 keV) Chandra
and ROSAT data. We find that the number density of >1e44 ergs/s sources
(quasars) steadily declines with decreasing redshift, while the number density
of 1e43-1e44 ergs/s sources peaks at z=0.5-1. Strikingly, however, the number
density of broad-line AGNs remains roughly constant with redshift while their
average luminosities decline at the lower redshifts, showing another example of
cosmic downsizing.


title: Neutrino signatures of the supernova - gamma ray burst relationship

abstract:
  We calculate the TeV-PeV neutrino fluxes of gamma-ray bursts associated with
supernovae, based on the observed association between GRB 030329 and supernova
SN 2003dh. The neutrino spectral flux distributions can test for possible
delays between the supernova and the gamma-ray burst events down to much
shorter timescales than what can be resolved with photons. As an illustrative
example, we calculate the probability of neutrino induced muon and electron
cascade events in a km scale under-ice detector at the South Pole, from the GRB
030329. Our calculations demonstrate that km scale neutrino telescopes are
expected to detect signals that will allow to constrain supernova-GRB models.


title: Non-Thermal X-ray and Radio Emission from the SNR N 157B

abstract:
  The supernova remnant N 157B contains a pulsar and three distinct synchrotron
components with rather unusual properties. 1) A somewhat irregular elliptical
pulsar wind nebula (PWN) visible in both X-ray and radio wavelengths. The
nebula is quite symmetrical with an extent of about 10 X 5 parsecs but offset
along the long axis by about 4 pc from the pulsar position. It is apparently
the result of a short-lived injection of energetic particles, perhaps starting
at the time of explosion. 2) A very bright X-ray shock region located just
outside the pulsar position in the edge of the PWN. This is undetected in the
radio. We attribute this feature to a new burst of particles from the pulsar
suggesting there are multiple episodes rather than continuous injection. 3) The
beginning of a radio synchrotron shell on the southern side of the SNR where
thermal X-rays appear to arise suggesting that N 157B is starting to become a
composite SNR.


title: HST detection of spiral structure in two Coma Cluster dwarf galaxies

abstract:
  We report the discovery of (stellar) spiral-like structure in Hubble Space
Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the
Coma cluster. GMP 3629 is the faintest such galaxy detected in a cluster
environment, and it is the first such galaxy observed in the dense Coma
cluster. The large bulge and the faintness of the broad spiral-like pattern in
GMP 3629 suggests that its disk may have been largely depleted.
  >We may therefore have found an example of the ``missing link'' in theories
of galaxy evolution which have predicted that dwarf spiral galaxies,
particularly in clusters, evolve into dwarf elliptical galaxies.


title: At the Vigintennial of the Butcher-Oemler Effect

abstract:
  In their study of the evolution of galaxies within clusters, Butcher and
Oemler discovered evidence for a strong evolution in star-formation rate with
redshift. Later studies confirmed this conclusion and uncovered several aspects
of the effect: photometric, spectroscopic, and morphological. This article
reviews a broad sample of these works and discusses selection effects, biases,
and driving mechanisms that might be responsible for the changes in
star-formation rate.


title:
Galaxy threshing and the origin of ultra-compact dwarf galaxies in the
  Fornax cluster

abstract:
  A recent all-object spectroscopic survey centred on the Fornax cluster of
galaxies, has discovered a population of sub-luminous and extremely compact
members, called ``ultra-compact dwarf'' (UCD) galaxies. In order to clarify the
origin of these objects, we have used self-consistent numerical simulations to
study the dynamical evolution a nucleated dwarf galaxy would undergo if
orbiting the center of the Fornax cluster and suffering from its strong tidal
gravitational field. We find that the outer stellar components of a nucleated
dwarf are removed by the strong tidal field of the cluster, whereas the nucleus
manages to survive as a result of its initially compact nature. The developed
naked nucleus is found to have physical properties (e.g., size and mass)
similar to those observed for UCDs. We also find that although this formation
process does not have a strong dependence on the initial total luminosity of
the nucleated dwarf, it does depend on the radial density profile of the dark
halo in the sense that UCDs are less likely to be formed from dwarfs embedded
in dark matter halos with central `cuspy' density profiles. Our simulations
also suggest that very massive and compact stellar systems can be rapidly and
efficiently formed in the central regions of dwarfs through the merging of
smaller star clusters. We provide some theoretical predictions on the total
number and radial number density profile of UCDs in a cluster and their
dependences on cluster masses.


title:
Star clusters and galactic chemodynamics: Implosive formation of super
  star clusters

abstract:
  We numerically investigate dynamical and chemical properties of star clusters
(open and globular clusters, and ``super star clusters'', SSC) formed in
interacting/merging galaxies. The investigation is two-fold: (1) large-scale
(100pc-100kpc) SPH simulations on density and temperature evolution of gas in
interacting/merging galaxies and (2) small-scale ones on the effects of high
gas pressure of ISM on the evolution of molecular clouds. We find that the
pressure of ISM in merging galaxies can become higher than the internal
pressure of GMCs ($\sim$ $10^5$ $\rm k_{\rm B}$ K $\rm cm^{-3}$), in
particular, in the tidal tails or the central regions of mergers. We also find
that GMCs can collapse to form super star clusters within an order of $10^7$ yr
owing to the strong compression by the high presser ISM in mergers.


title: The INTEGRAL ground segment and its science operations centre

abstract:
  The INTEGRAL ground segment is divided into operational and scientific
components. The operational component consists of the Mission Operations
Centre, the ground stations and communications lines while the scientific
component comprises of a Science Operations Centre and Science Data Centre. The
overall architecture of the ground segment is described paying particular
attention to the tasks and functionalities of the INTEGRAL Science Operations
Centre.


title:
The optical system of the H.E.S.S. imaging atmospheric Cherenkov
  telescopes, Part I: layout and components of the system

abstract:
  H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large
imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for
each of four telescopes, and photomultiplier cameras with a large field of view
(5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to
provide good imaging properties over the full field of view, combined with
mechanical stability. The paper describes the design criteria and
specifications of the system, and the individual components -- dish, mirrors,
and Winston cones -- as well as their characteristics. The optical performance
of the telescope as a whole is the subject of a companion paper.


title:
The optical system of the H.E.S.S. imaging atmospheric Cherenkov
  telescopes, Part II: mirror alignment and point spread function

abstract:
  Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are
aligned using stars imaged onto the closed lid of the PMT camera, viewed by a
CCD camera. The alignment procedure works reliably and includes the automatic
analysis of CCD images and control of the facet alignment actuators. On-axis,
80% of the reflected light is contained in a circle of less than 1 mrad
diameter. The spot widens with increasing angle to the telescope axis. In
accordance with simulations, the spot size has roughly doubled at an angle of
1.4 degr. from the axis. The expected variation of spot size with elevation due
to deformations of the support structure is visible, but is completely
non-critical over the usual working range. Overall, the optical quality of the
telescope exceeds the specifications.


title: Towards a complete theory of Gamma Ray Bursts

abstract:
  Gamma Ray Bursts (GRBs) are notorious for their diversity. Yet, they have a
series of common features. The typical energy of their $\gamma$ rays is a
fraction of an MeV. The energy distributions are well described by a ``Band
spectrum'', with ``peak energies'' spanning a surprisingly narrow range. The
time structure of a GRB consists of pulses, superimposed or not, rising and
decreasing fast. The number of photons in a pulse, the pulses' widths and their
total energy vary within broad but given ranges. Within a pulse, the energy
spectrum softens with increasing time. The duration of a pulse decreases at
higher energies and its peak intensity shifts to earlier time. Many other
correlations between pairs of GRB observables have been identified. Last (and
based on one measured event!) the $\gamma$-ray polarization is very large. A
satisfactory theory of GRBs should naturally and very simply explain, among
others, all these facts. We show that the "cannonball" (CB) model does it. In
the CB model the process leading to the ejection of highly relativistic jetted
CBs in core-collapse supernova (SN) explosions is akin to the one observed in
quasars and microquasars. The prompt $\gamma$-ray emission --the GRB-- is
explained extremely well by inverse Compton scattering of light in the near
environment of the SN by the electrons in the CBs' plasma. We have previously
shown that the CB-model's description of GRB afterglows as synchrotron
radiation from ambient electrons --swept in and accelerated within the CBs-- is
also simple, universal and very successful. The only obstacle still separating
the CB model from a complete theory of GRBs is the theoretical understanding of
the CBs' ejection mechanism in SN explosions.


title:
Second Order Accurate Schemes for Magnetohydrodynamics With
  Divergence-Free Reconstruction

abstract:
  In this paper we study the problem of divergence-free numerical MHD and show
that the work done so far still has four key unresolved issues. We resolve
those issues in this paper. The problem of reconstructing MHD flow variables
with spatially second order accuracy is also studied. The other goal of this
paper is to show that the same well-designed second order accurate schemes can
be formulated for more complex geometries such as cylindrical and spherical
geometry. Being able to do divergence-free reconstruction in those geometries
also resolves the problem of doing AMR in those geometries. The resulting MHD
scheme has been implemented in Balsara's RIEMANN framework for parallel,
self-adaptive computational astrophysics. The present work also shows that
divergence-free reconstruction and the divergence-free time-update can be done
for numerical MHD on unstructured meshes. All the schemes designed here are
shown to be second order accurate. Several stringent test problems are
presented to show that the methods work, including problems involving high
velocity flows in low plasma-b magnetospheric environments.


title: Large-scale Gas Dynamics in the Milky Way

abstract:
  We present new gas flow models for the Milky Way inside the solar circle.
Using a mass model derived from the COBE/DIRBE maps and clump giant star
counts, and using a parametric model for the spiral arm pattern in the disk, we
calculate the gas flow and compare with 12CO observations. We find that models
with 4 spiral arms fit the observations better then 2-armed models. We also
find that models with separate pattern speeds for the bar and spiral arms can
explain the gas flow in the bar corotation region better than single-pattern
speed models.


title: Scattering by Interstellar Dust Grains. II. X-Rays

abstract:
  Scattering and absorption of X-rays by interstellar dust is calculated for a
model consisting of carbonaceous grains and amorphous silicate grains. The
calculations employ realistic dielectric functions with structure near X-ray
absorption edges, with resulting features in absorption, scattering, and
extinction.
  Differential scattering cross sections are calculated for energies between
0.3 and 10 keV. The median scattering angle is given as a function of energy,
and simple but accurate approximations are found for the X-ray scattering
properties of the dust mixture, as well as for the angular distribution of the
scattered X-ray halo for dust with simple spatial distributions. Observational
estimates of the X-ray scattering optical depth are compared to model
predictions. Observations of X-ray halos to test interstellar dust grain models
are best carried out using extragalactic point sources.


title: Saturated State of the Nonlinear Small-Scale Dynamo

abstract:
  We consider the problem of incompressible, forced, nonhelical, homogeneous
and isotropic MHD turbulence with no mean magnetic field and large magnetic
Prandtl number. This type of MHD turbulence is the end state of the turbulent
dynamo, which generates folded fields with small-scale direction reversals. We
propose a model in which saturation is achieved as a result of the velocity
statistics becoming anisotropic with respect to the local direction of the
magnetic folds. The model combines the effects of weakened stretching and
quasi-two-dimensional mixing and produces magnetic-energy spectra in remarkable
agreement with numerical results at least in the case of a one-scale flow. We
conjecture that the statistics seen in numerical simulations could be explained
as a superposition of these folded fields and Alfv\'en-like waves that
propagate along the folds.


title:
Resonant Trapping of Planetesimals by Planet Migration: Debris Disk
  Clumps and Vega's Similarity to the Solar System

abstract:
  This paper describes a model which can explain the observed clumpy structures
of debris disks. Clumps arise because after a planetary system forms its
planets migrate due to angular momentum exchange with the remaining
planetesimals. Outward migration of the outermost planet traps planetesimals
outside its orbit into its resonances and resonant forces cause azimuthal
structure in their distribution. The model is based on numerical simulations of
planets of different masses, Mpl, migrating at different rates, dapl/dt,
through a dynamically cold (e<0.01) planetesimal disk initially at a semimajor
axis a. Trapping probabilities and the resulting azimuthal structures are
presented for a planet's 2:1, 5:3, 3:2, and 4:3 resonances. Seven possible
dynamical structures are identified from migrations defined by mu=Mpl/Mstar and
theta=dapl/dt*sqrt(a/Mstar). Application of this model to the 850um image of
Vega's disk shows its two clumps of unequal brightness can be explained by the
migration of a Neptune-mass planet from 40 to 65AU over 56Myr; tight
constraints are set on possible ranges of these parameters. The clumps are
caused by planetesimals in the 3:2 and 2:1 resonances; the asymmetry arises
because of the overabundance of planetesimals in the 2:1(u) over the 2:1(l)
resonance. The similarity of this migration to that proposed for our own
Neptune hints that Vega's planetary system may be much more akin to the solar
system than previously thought. Predictions are made which would substantiate
this model, such as the orbital motion of the clumpy pattern, the location of
the planet, and the presence of lower level clumps.


title:
Probing the Inflow/Out-flow and Accretion Disk of Cyg X-1 in the High
  State with HETG/Chandra

abstract:
  Cyg X-1 was observed in the high state at the conjunction orbital phase (0)
with HETG/Chandra. Strong and asymmetric absorption lines of highly ionized
species were detected, such as Fe XXV, Fe XXIV, Fe XXIII, Si XIV, S XVI, Ne X,
and etc. In the high state the profile of the absorption lines are composed of
an extended red wing and a less extended blue wing. The red wings of higher
ionized species are more extended than that of lower ionized species. The
detection of these lines provides a way to probe the properties of the flow
around the companion and the black hole in Cyg X-1 during the high state. A
broad emission feature around 6.5 keV was significantly detected from the both
spectra of HETG/Chandra and PCA/RXTE. This feature appears to be symmetric and
can be fitted with a Gaussian function rather than the Laor disk line model of
fluorescent Fe K$_\alpha$ line from an accretion disk. The implications of
these results on the structure of the accretion flow of Cyg X-1 in the high
state are discussed.


title: An XMM-Newton observation of the galaxy group MKW 4

abstract:
  We present an X-ray study of the galaxy group or poor cluster MKW 4. Working
with XMM data we examine the distribution and properties of the hot gas which
makes up the group halo. The inner halo shows some signs of structure, with
circular or elliptical beta models providing a poor fit to the surface
brightness profile. This may be evidence of large scale motion in the inner
halo, but we do not find evidence of sharp fronts or edges in the emission. The
temperature of the halo declines in the core, with deprojected spectral fits
showing a central temperature of ~1.3 keV compared to ~3 keV at 100 kpc. In the
central ~30 kpc of the group multi-temperature spectral models are required to
fit the data, but they indicate a lack of gas at low temperatures. Steady state
cooling flow models provide poor fits to the inner regions of the group and the
estimated cooling time of the gas is long except within the central dominant
galaxy, NGC 4073. Abundance profiles show a sharp increase in the core of the
group, with mean abundance rising by a factor of two in the centre of NGC 4073.
Fitting individual elements shows the same trend, with high values of Fe, Si
and S in the core. We estimate that ~50% of the Fe in the central 40 kpc was
injected by SNIa, in agreement with previous ASCA studies. Using our best
fitting surface brightness and temperature models, we calculate the mass, gas
fraction, entropy and mass-to-light ratio of the group. At 100 kpc (~0.1 virial
radii) the total mass and gas entropy of the system (~2x10^13 Msol and ~300 keV
cm^2) are quite comparable to those of other systems of similar temperature,
but the gas fraction is rather low (~1%). We conclude that MKW 4 is a fairly
relaxed group, which has developed a strong central temperature gradient but
not a large-scale cooling flow.


title:
The Formaldehyde Masers in NGC 7538 and G29.96-0.02: VLBA, MERLIN, and
  VLA Observations

abstract:
  The 6 cm formaldehyde (H2CO) maser sources in the compact HII regions NGC
7538-IRS1 and G29.96-0.02 have been imaged at high resolution (beams < 50 mas).
Using the VLBA and MERLIN, we find the angular sizes of the NGC 7538 masers to
be ~10 mas (30 AU) corresponding to brightness temperatures ~10^8 K. The
angular sizes of the G29.96-0.02 masers are ~20 mas (130 AU) corresponding to
brightness temperatures ~10^7 K. Using the VLA, we detect 2 cm formaldehyde
absorption from the maser regions. We detect no emission in the 2 cm line,
indicating the lack of a 2 cm maser and placing limits on the 6 cm excitation
process. We find that both NGC 7538 maser components show an increase in
intensity on 5-10 year timescales while the G29.96-0.02 masers show no
variability over 2 years. A search for polarization provides 3-sigma upper
limits of 1% circularly polarized and 10% linearly polarized emission in NGC
7538 and of 15% circularly polarized emission in G29.96-0.02. A pronounced
velocity gradient of 28 km/s/arcsecond (1900 km/s/pc) is detected in the NGC
7538 maser gas.


title:
Gamma-Ray Bursts and Magnetars as Possible Sources of Ultra High Energy
  Cosmic Rays: Correlation of Cosmic Ray Event Positions with IRAS Galaxies

abstract:
  We use the two-dimensional Kolmogorov-Smirnov (KS) test to study the
correlation between the 60 cosmic ray events above 4x10^19 eV from the AGASA
experiment and the positions of infrared luminous galaxies from the IRAS PSCz
catalog. These galaxies are expected to be hosts to gamma ray bursts (GRB) and
magnetars, both of which are associated with core collapse supernovae and have
been proposed as possible acceleration sites for ultra high energy cosmic rays.
We find consistency between the models and the AGASA events to have been drawn
from the same underlying distribution of positions on the sky with KS
probabilities ~50%. Application of the same test to the 11 highest AGASA events
above 10^20 eV, however, yields a KS probability of < 0.5%, rejecting the
models at >99.5% significance level. Taken at face value, these highest energy
results suggest that the existing cosmic ray events above 10^20 eV do not owe
their origin to long burst GRBs, rapidly rotating magnetars, or any other
events associated with core collapse supernovae. The larger data set expected
from the AUGER experiment will test whether this conclusion is real or is a
statistical fluke that we estimate to be at the 2 sigma level.


title:
Hubble Space Telescope observations of three very young star clusters in
  the Small Magellanic Cloud

abstract:
  We present Space Telescope Imaging Spectrograph (STIS) broad band imagery and
optical slitless spectroscopy of three young star clusters in the Small
Magellanic Cloud (SMC). MA 1796 and MG 2 were previously known as Planetary
Nebulae, and observed as such within our Hubble Space Telescope (HST) survey.
With the HST spatial resolution, we show that they are instead H II regions,
surrounding very young star clusters. A third compact H II region, MA 1797, was
serendipitously observed by us as it falls in the same frame of MA 1796.
Limited nebular analysis is presented as derived from the slitless spectra. We
find that MA 1796 and MG 2 are very heavily extincted, with c>1.4, defining
them as the most extincted optically-discovered star forming regions in the
SMC. MA 1796 and MG 2 are extremely compact (less than 1 pc across), while MA
1797, with diameter of about 3 pc, is similar to the ultra compact H II regions
already known in the SMC. Stellar analysis is presented, and approximate
reddening correction for the stars is derived from the Balmer decrement.
Limited analysis of their stellar content and their ionized radiation shows
that these compact H II regions are ionized by small stellar clusters whose
hottest stars are at most of the B0 class. These very compact, extremely
reddened, and probably very dense H II regions in the SMC offer insight in the
most recent star formation episodes in a very low metallicity galaxy.


title:
MAXIPOL: A Balloon-borne Experiment for Measuring the Polarization
  Anisotropy of the Cosmic Microwave Background Radiation

abstract:
  We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure
the E-mode polarization anisotropy of the cosmic microwave background radiation
(CMB) on angular scales of 10 arcmin to 2 degrees. MAXIPOL is the first CMB
experiment to collect data with a polarimeter that utilizes a rotating
half-wave plate and fixed wire-grid polarizer. We present the instrument
design, elaborate on the polarimeter strategy and show the instrument
performance during flight with some time domain data. Our primary data set was
collected during a 26 hour turnaround flight that was launched from the
National Scientific Ballooning Facility in Ft. Sumner, New Mexico in May 2003.
During this flight five regions of the sky were mapped. Data analysis is in
progress.


title:
Cross-Correlation of the Cosmic Microwave Background with the 2MASS
  Galaxy Survey: Signatures of Dark Energy, Hot Gas, and Point Sources

abstract:
  We cross-correlate the Cosmic Microwave Background (CMB) temperature
anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP) with
the projected distribution of extended sources in the Two Micron All Sky Survey
(2MASS). By modelling the theoretical expectation for this signal, we extract
the signatures of dark energy (Integrated Sachs-Wolfe effect;ISW), hot gas
(thermal Sunyaev-Zeldovich effect;thermal SZ), and microwave point sources in
the cross-correlation. Our strongest signal is the thermal SZ, at the 3.1-3.7
\sigma level, which is consistent with the theoretical prediction based on
observations of X-ray clusters. We also see the ISW signal at the 2.5 \sigma
level, which is consistent with the expected value for the concordance LCDM
cosmology, and is an independent signature of the presence of dark energy in
the universe. Finally, we see the signature of microwave point sources at the
2.7 \sigma level.


title: The White Dwarf Deficit in Open Clusters: Dynamical Processes

abstract:
  In Galactic open clusters, there is an apparent paucity of white dwarfs
compared to the number expected assuming a reasonable initial mass function and
that main-sequence stars with initial mass <= 8 M_sun become white dwarfs. We
suggest that this lack of white dwarfs is due at least in part to dynamical
processes. Non-spherically symmetric mass loss during the post-main-sequence
evolution would lead to a few km/s isotropic recoil speed for the white dwarf
remnant. This recoil speed can cause a substantial fraction of the white dwarfs
formed in a cluster to leave the system. We investigate this dynamical process
by carrying out high-precision N-body simulations of intermediate-mass open
clusters, where we apply an isotropic recoil speed to the white dwarf remnants.
Our models suggest that almost all white dwarfs would be lost from the cluster
if the average recoil speed exceeds twice the velocity dispersion of the
cluster.


title:
The Eye of the Tornado - an isolated, high mass young stellar object
  near the Galactic centre

abstract:
  We present infrared (AAT, UKIRT) and radio (VLA, SEST) observations of the
Eye of the Tornado, a compact source apparently near the head of the Tornado
Nebula. The near-infrared Br-gamma and He I lines are broad (FWHM 40 and 30
km/s, respectively) and have a line centre at Vlsr = -205 km/s. This
corresponds to a feature at the same velocity in the 12CO J=1-0 line profile.
The kinematic velocity derived from Galactic rotation places the Eye at the
distance of the Galactic Centre (i.e. 8.5 kpc) and separated (probably
foreground) from the Tornado Nebula. Four knots of emission are seen in the
Br-gamma line and at 6 and 20 cm. Together with the flat radio spectral index,
we confirm that the Eye contains ionized gas, but that this is embedded within
a dense molecular core. The spectral energy distribution can be modelled as a
two-component blackbody + greybody, peaking at far-IR wavelengths. The knots
are UC HII regions, and the core contains a luminous (2 x 10^4 Lsun), embedded,
massive young stellar source. We also propose a geometrical model for the Eye
to account for both its spectral energy distribution and its morphology.


title: Formation of globular clusters in galaxy mergers

abstract:
  Our numerical simulations first demonstrate that the pressure of ISM in a
major merger becomes so high ($>$ $10^5$ $\rm k_{\rm B}$ K $\rm cm^{-3}$) that
GMCs in the merger can collapse to form globular clusters (GCs) within a few
Myr. The star formation efficiency within a GMC in galaxy mergers can rise up
from a few percent to $\sim$ 80 percent, depending on the shapes and the
temperature of the GMC. This implosive GC formation due to external high
pressure of warm/hot ISM can be more efficient in the tidal tails or the
central regions of mergers. The developed clusters have King-like profile with
the effective radius of a few pc. The structural, kinematical, and chemical
properties of these GC systems can depend on orbital and chemical properties of
major mergers.


title:
Starbursts from strong compression of galactic molecular clouds due to
  the high pressure of the intracluster medium

abstract:
  We demonstrate that the high pressure of the hot intracluster medium (ICM)
can trigger the collapse of molecular clouds in a spiral galaxy, leading to a
burst of star formation in the clouds. Our hydrodynamical simulations show that
the high gaseous (ram pressure and static thermal) pressure of the ICM strongly
compresses a self-gravitating gas cloud within a short time scale ($\sim$
$10^{7}$ yr), dramatically increasing the central gas density, and consequently
causing efficient star formation within the cloud. The stars developed in the
cloud form a compact, gravitationally bound, star cluster. The star formation
efficiency within such a cloud is found to depend on the temperature and the
density of the ICM and the relative velocity of the galaxy with respect to it.
Based on these results, we discuss the origin of starburst/poststarburst
populations observed in distant clusters, the enhancement of star formation for
galaxies in merging clusters, and the isolated compact HII regions recently
discovered in the Virgo cluster.


title: High Precision Differential Astrometry

abstract:
  While conventional imaging in VLBI provides information only about the
relative position between different features of a given source,
phase-referenced observations can provide precise positional information with
respect to an external reference. The use of differential techniques relies on
the fact that most of the instrumental and propagation effects are common for
radio sources sufficiently close together in the sky. These effects cancel by
subtracting the visibility phases of the reference source from that of the
neighboring objects. Differential VLBI astrometry yields relative positions of
radio sources with sub-milliarcsecond accuracy. These high precisions can be
applied to solve various astrophysical problems. In this paper I will review
the progress made recently in this field, both in technique and science.


title: Searching for non-Gaussianity in the VSA data

abstract:
  We have tested Very Small Array (VSA) observations of three regions of sky
for the presence of non-Gaussianity, using high-order cumulants, Minkowski
functionals, a wavelet-based test and a Bayesian joint power
spectrum/non-Gaussianity analysis. We find the data from two regions to be
consistent with Gaussianity. In the third region, we obtain a 96.7% detection
of non-Gaussianity using the wavelet test. We perform simulations to
characterise the tests, and conclude that this is consistent with expected
residual point source contamination. There is therefore no evidence that this
detection is of cosmological origin. Our simulations show that the tests would
be sensitive to any residual point sources above the data's source subtraction
level of 20 mJy. The tests are also sensitive to cosmic string networks at an
rms fluctuation level of $105 \mu K$ (i.e. equivalent to the best-fit observed
value). They are not sensitive to string-induced fluctuations if an equal rms
of Gaussian CDM fluctuations is added, thereby reducing the fluctuations due to
the strings network to $74 \mu K$ rms . We especially highlight the usefulness
of non-Gaussianity testing in eliminating systematic effects from our data.


title: The impact of pollution on stellar evolution models

abstract:
  An approach is introduced for incorporating the concept of stellar pollution
into stellar evolution models. The approach involves enhancing the metal
content of the surface layers of stellar models. In addition, the surface
layers of stars in the mass range of 0.5-2.0 Solar masses are mixed to an
artificial depth motivated by observations of lithium abundance. The behavior
of polluted stellar evolution models is explored assuming the pollution occurs
after the star has left the fully convective pre main sequence phase. Stellar
models polluted with a few Earth masses of iron are significantly hotter than
stars of the same mass with an equivalent bulk metallicity. Polluted stellar
evolution models can successfully reproduce the metal-rich, parent star tau
Bootis and suggest a slightly lower mass than standard evolution models.
Finally, the possibility that stars in the Hyades open cluster have accreted an
average of 0.5 Earth masses of iron is explored. The results indicate that it
is not possible to rule out stellar pollution on this scale from the scatter of
Hyades stars on a color-magnitude diagram. The small amount of scatter in the
observational data set does rule out pollution on the order of 1.5 Earth masses
of iron. Pollution effects at the low level of 0.5 Earth masses of iron do not
produce substantial changes in a star's evolution.


title: Stellar pollution and [Fe/H] in the Hyades

abstract:
  The Hyades open cluster presents a unique laboratory for planet formation and
stellar pollution studies because all of the stars have essentially the same
age and were born from the same cloud of gas. Furthermore, with an age of
roughly 650 Myr most of the intermediate and low mass stars are on the main
sequence. Given these assumptions, the accretion of metal rich material onto
the surface of a star during and shortly after the formation of planetary
systems should be evident via the enhanced metallicity of the star. Building on
previous work, stellar evolution models which include the effects of stellar
pollution are applied to the Hyades. The results of several Monte Carlo
simulations, in which the amount of accreted material is drawn at random from a
Gaussian distribution with standard deviation equal to half the mean, are
presented. An effective temperature-[Fe/H] relation is produced and compared to
recent observations. The theoretical predictions presented in this letter will
be useful in future searches for evidence of stellar pollution due to planet
formation. It is concluded that stellar pollution effects at the mean level of
>=2 Earth masses of iron are ruled out by current observational data.


title:
Radiation environment along the INTEGRAL orbit measured with the IREM
  monitor

abstract:
  The INTEGRAL Radiation Environment Monitor (IREM) is a payload supporting
instrument on board the INTEGRAL satellite. The monitor continually measures
electron and proton fluxes along the orbit and provides this information to the
spacecraft on board data handler. The mission alert system broadcasts it to the
payload instruments enabling them to react accordingly to the current radiation
level. Additionally, the IREM conducts its autonomous research mapping the
Earth radiation environment for the space weather program. Its scientific data
are available for further analysis almost without delay.


title: On the Formation of Giant Elliptical Galaxies and Globular Clusters

abstract:
  I review the current status of understanding when, how long, and how giant
elliptical galaxies formed, focusing on the globular clusters. Several
observational evidences show that massive elliptical galaxies formed at $z>2$
($>10$ Gyr ago). Giant elliptical galaxies show mostly a bimodal color
distribution of globular clusters, indicating a factor of $\approx 20$
metallicity difference between the two peaks. The red globular clusters (RGCs)
are closely related with the stellar halo in color and spatial distribution,
while the blue globular clusters (BGCs) are not. The ratio of the number of the
RGCs and that of the BGCs varies depending on galaxies. It is concluded that
the BGCs might have formed 12--13 Gyr ago, while the RGCs and giant elliptical
galaxies might have formed similarly 10-11 Gyr ago. It remains now to explain
the existence of a gap between the RGC formation epoch and the BGC formation
epoch, and the rapid metallicity increase during the gap ($\Delta t \approx 2$
Gyr). If hierarchical merging can form a significant number of giant elliptical
galaxies $>10$ Gyr ago, several observational constraints from stars and
globular clusters in elliptical galaxies can be explained.


title: Enhanced Optical Emission During Crab Giant Radio Pulses

abstract:
  We detected a correlation between optical and giant radio pulse emission from
the Crab pulsar. Optical pulses coincident with the giant radio pulses were on
average 3% brighter than those coincident with normal radio pulses. Combined
with the lack of any other pulse profile changes, this result indicates that
both the giant radio pulses and the increased optical emission are linked to an
increase in the electron-positron plasma density.


title: GEMS Imaging of Red Sequence Galaxies at z~0.7: Dusty or Old?

abstract:
  We have used the 30'x30' Hubble Space Telescope image mosaic from the Galaxy
Evolution from Morphology and SEDs (GEMS) project in conjunction with the
COMBO-17 deep photometric redshift survey to define a sample of nearly 1500
galaxies with 0.65 < z < 0.75. With this sample, we can study the distribution
of rest-frame V-band morphologies more than 6 Gyr ago, without differential
bandpass shifting and surface brightness dimming across this narrow redshift
slice. Focusing on red-sequence galaxies at z ~ 0.7, we find that 85% of their
combined rest-frame V-band luminosity density comes from visually-classified
E/S0/Sa galaxies (at V-band magnitudes brighter than -19.5). Similar results
are obtained if automated classifiers are used. This fraction is identical to
that found at the present day, and is biased by less than 10% by large scale
structure and the morphology-density relation. Under the assumption that
peculiar and edge-on disk galaxies are red by virtue of their dust content, we
find that less than 13% of the total rest-frame V-band luminosity of the z ~
0.7 red galaxy population is from dusty galaxies.


title:
The Slow Decay of Some Radio Afterglows, a Puzzle for the Simplest GRB
  Fireball Model

abstract:
  Abridged:
  The decay of half of the GRB radio afterglows with long temporal monitoring
is significantly slower than at optical frequencies, contrary to what is
expected in the simplest fireball model. We investigate four ways to decouple
the radio and optical decays: an evolving index of the power-law distribution
of the shock-accelerated electrons, the presence of a spectral break between
the two domains, a structured outflow, and a long-lived reverse shock
contribution to the afterglow emission. [...]
  In the fourth scenario, it is assumed that the radio afterglow emission
arises in the reverse shock propagating in a steady stream of ejecta, which
catch up with the decelerating GRB remnant. This scenario can accommodate the
properties of the afterglows with slow radio decays and requires that the
injected energy is less than or comparable to the initial fireball energy,
while other afterglow parameters have reasonable values.
  For a jet, the transition to a semi-relativistic motion mitigates the radio
decay, however this scenario would work only when the slower radio decay is
observed well after the steeper optical fall-off. A structured outflow with a
relativistic core, yielding a fast decaying optical emission, and a
non-relativistic envelope, producing a slowly falling-off radio afterglow, is
not a viable solution, as it fails to decouple the radio and optical decays.


title:
An Intrinsic Absorption Complex Toward RXJ1230.8+0115: Geometry and
  Photoionization Conditions

abstract:
  We present HST/STIS and FUSE spectra of the quasar RXJ1230.8+0115 (V=14.4,
z=0.117). In addition to Galactic, Virgo, and intervening absorption, this
quasar is host to a remarkable intrinsic absorption complex. Four narrow
absorption line systems, strong in CIV, NV, and OVI, lie within 5000 km/s of
the QSO redshift. Three of the systems appear to be line-locked, two in NV, and
two in OVI, with the common system residing in between the other two (in
velocity). All three systems show signs of an intrinsic origin -- smooth
wind-like profiles, high ionization, and partial coverage of the central
engine. The fourth system, which appears at the systemic redshift of the QSO,
may originate from host galaxy or intervening gas. Photoionization analyses
imply column densities in the range 19.1<log N(H)<21 and ionization parameters
in the range -1.3<log U<0.3. Revisiting the issue of line-locking, we discuss a
possible model in the context of the accretion-disk/wind scenario and point out
several issues that remain for future simulations and observations.


title: A Ring Shaped Embedded Young Stellar (Proto)Cluster

abstract:
  We present sub-arcsec (FWHM ~ 0.5") J, H, K and L' images of a young stellar
cluster associated with a candidate massive protostar IRAS22134+5834. The
observations reveal a centrally symmetric, flattened cluster enclosing a
central dark region. The central dark region is possibly a cavity within the
flattened cluster. It is surrounded by a ring composed of 5 bright stars and
the candidate massive protostar IRAS22134+5834. We construct JHKL' color-color
and HK color-magnitude diagrams to identify the young stellar objects and
estimate their spectral types. All the bright stars in the ring are found to
have intrinsic infrared excess emission and are likely to be early to late B
type stars. We estimate an average foreground extinction to the cluster of A_v
\~ 5mag and individual extinctions to the bright stars in the range A_v ~
20-40mag indicating possible cocoons surrounding each massive star. This ring
of bright stars is devoid of any HII region. It is surrounded by an embedded
cluster making this an example of a (proto)cluster that is in one of the
dynamically least relaxed states. These observations are consistent with the
recent non-axisymmetric calculations of Li & Nakamura, who present a star
formation scenario in which a magnetically subcritical cloud fragments into
multiple magnetically supercritical cores, leading to the formation of small
stellar groups.


title:
Local Surface Density of the Galactic Disk from a 3-D Stellar Velocity
  Sample

abstract:
  We have re-estimated the surface density of the Galactic disk in the solar
neighborhood within $\pm$ 0.4 kpc of the Sun using parallaxes and proper
motions of a kinematically and spatially unbiased sample of 1476 old bright red
giant stars from the Hipparcos catalog with measured radial velocities from
Barbier-Brossat & Figon (2000). We determine the vertical distribution of the
red giants as well as the vertical velocity dispersion of the sample, (14.4
$\pm$ 0.26 km/sec), and combine these to derive the surface density of
gravitating matter in the Galactic disk as a function of the galactic
coordinate $z$. The surface density of the disk increases from 10.5 $\pm$ 0.5
$M_{\odot}$ / pc$^2$ within $\pm$ 50 pc to 42 $\pm$ 6 $M_{\odot}$ / pc$^2$
within $\pm$ 350 pc. The estimated volume density of the galactic disk within
$\pm$ 50 pc is about 0.1 $M_{\odot}$ / pc$^3$ which is close to the volume
density estimates of the observed baryonic matter in the solar neighborhood.


title: A Giant Outburst at Millimeter Wavelengths in the Orion Nebula

abstract:
  BIMA observations of the Orion nebula discovered a giant flare from a young
star previously undetected at millimeter wavelengths. The star briefly became
the brightest compact object in the nebula at 86 GHz. Its flux density
increased by more than a factor of 5 on a timescale of hours, to a peak of 160
mJy. This is one of the most luminous stellar radio flares ever observed.
Remarkably, the Chandra X-ray observatory was in the midst of a deep
integration of the Orion nebula at the time of the BIMA discovery; the source's
X-ray flux increased by a factor of 10 approximately 2 days before the radio
detection. Follow-up radio observations with the VLA and BIMA showed that the
source decayed on a timescale of days, then flared again several times over the
next 70 days, although never as brightly as during the discovery. Circular
polarization was detected at 15, 22, and 43 GHz, indicating that the emission
mechanism was cyclotron. VLBA observations 9 days after the initial flare yield
a brightness temperature Tb > 5 x 10^7 K at 15 GHz. Infrared spectroscopy
indicates the source is a K5V star with faint Br gamma emission, suggesting
that it is a weak-line T Tauri object. Zeeman splitting measurements in the
infrared spectrum find B ~ 2.6 +/- 1.0 kG. The flare is an extreme example of
magnetic activity associated with a young stellar object. These data suggest
that short observations obtained with ALMA will uncover hundreds of flaring
young stellar objects in the Orion region.


title:
The X-ray Properties of the Nearby Star-Forming Galaxy IC 342: The
  XMM-Newton View

abstract:
  We present the X-ray properties of IC342 using XMM-Newton. Thirty-five
sources are detected coincident with the disk of IC342 (more than tripling the
number known), of which ~31 are likely to be intrinsic to IC342. This
population shows a range of spectral properties and has an X-ray luminosity
function slope and infrared luminosity comparable to that of starburst galaxies
such as M82 and the Antennae, while its relative lack of extended X-ray
emission is similar to the properties of quiescent spirals. We do detect
long-term variability between this observation and the 1991 ROSAT and 1993/2000
ASCA observations for five sources. Notably, the second most luminous source
IC342 X-2 is is found to be in its the lowest luminosity state observed for X-2
to date, although the slope of the spectrum is intermediate between the
previously observed low/hard and high/soft states. IC342 X-1, on the other
hand, is found to be in an identical state to that observed in 2000 with ASCA.
Assuming X-1 is in an anomalous very high (VH) state, then either (1) X-1 has
remained in this state between 2000 and 2002, and is therefore the longest
duration VH-state binary ever observed, or (2) it was simply caught in a VH
state by chance in both the 2000 ASCA and 2002 XMM-Newton observations. We have
also confirmed the ROSAT HRI result that the nucleus of IC342 is made up of
both point-like and extended emission. The relative fluxes of the two spectral
components suggest that the nucleus is complex, with a soft extended component
contributing approximately half of the total luminosity. (Abridged)


title: Distribution of Circumstellar Disk Masses in the Young Cluster NGC 2024

abstract:
  We determine the distribution of circumstellar disk masses in the young (~0.3
Myr) cluster NGC 2024 by imaging a 2.5'x2.5' region in 3mm continuum emission
to an RMS noise level of ~0.75 mJy/beam with the Owens Valley Millimeter Array.
The mosaic encompasses 147 K-band sources as well as the molecular ridge seen
previously in dust continuum emission. We detect 10 point-like sources in 3mm
continuum emission above the level of 5-sigma within the unit gain region of
the mosaic. One of these sources corresponds to the near-IR source IRS 2, an
early B-type star. Two other sources are tentatively associated with low-mass
near-IR cluster members, and the remaining 7 sources have no K-band
counterparts. Assuming the millimeter continuum point sources represent
emission from circumstellar disks and/or envelopes, then ~6% of the total
population (infrared and millimeter sources) in the NGC 2024 mosaic has a
circumstellar mass in excess of ~0.06 solar masses. We obtain further
constraints on the average circumstellar disk mass by considering the mean
millimeter continuum flux observed toward a sample of 140 K-band sources that
likely have stellar masses <1-2 Msun. While none of these sources are detected
individually above the 3-sigma limit of ~0.035 Msun, the ensemble of sources
are detected in the mean at the 5-sigma level with a mean disk mass of ~0.005
Msun. Compared to the older (~2 Myr) cluster IC 348, NGC 2024 contains a higher
frequency of massive disks/envelopes and has a higher mean disk mass by a
factor of 2.5 +/- 1.3 among K-band sources, suggesting that the mean
circumstellar mass is decreasing with cluster age. We also compare the results
for the NGC 2024 and IC 348 clusters to those for the lower-density Taurus star
forming region.


title:
A Parametric Representation of Critical Curves and Caustics for a Binary
  Gravitational Lens

abstract:
  We find a simple expression for critical curves of a binary gravitational
lens. On the basis of this, we present a parametric representation of such
curves. The caustics can also be expressed with the same parameterization. The
present result is helpful for efficiently constructing many templates of light
curves due to binary systems, particularly extrasolar planets, which cause
spikes in the light curves when a source crosses the caustics.