title: Near infrared and the inner regions of protoplanetary disks

abstract:
  We examine the ``puffed-up inner disk'' model (Dullemond, Dominik & Natta
2001), proposed for explaining the near-IR excess radiation from Herbig Ae/Be
stars. Detailed model computations show that the observed near-IR excess
requires more hot dust than is contained in the puffed-up disk rim. The rim can
produce the observed near-IR excess only if its dust has perfectly gray
opacity, but such dust is in conflict with the observed 10$\mu$m spectral
feature. We find that a compact ($\sim$ 10 AU) tenuous ($\tau_V \la 0.4$) dusty
halo around the disk inner regions contains enough dust to readily explain the
observations. Furthermore, this model also resolves the puzzling relationship
noted by Monnier and Millan-Gabet (2002) between luminosity and the
interferometric inner radii of disks.


title:
Late internal shock model for bright X-ray flares in Gamma-ray Burst
  afterglows and GRB 011121

abstract:
  We explore two possible models which might give rise to bright X-ray flares
in GRBs afterglows. One is an external forward-reverse shock model, in which
the shock parameters of forward/reverse shocks are taken to be quite different.
The other is a so called "late internal shock model", which requires a
refreshed unsteady relativistic outflow generated after the prompt $\gamma-$ray
emission. In the forward-reverse shock model, after the time $t_\times$ at
which the RS crosses the ejecta, the flux declines more slowly than
$(t_\oplus/t_\times)^{-(2+\beta)}$, where $t_\oplus$ denotes the observer's
time and $\beta$ is the spectral index of the X-ray emission. In the ``late
internal shock model", decaying slopes much steeper than $(t_\oplus/t_{\rm e,
\oplus})^{-(2+\beta)}$ are possible if the central engine shuts down after
$t_{\rm e, \oplus}$ and the observed variability timescale of the X-ray flare
is much shorter than $t_{\rm e, \oplus}$.
  The sharp decline of the X-ray flares detected in GRB 011121, XRF 050406, GRB
050502b, and GRB 050730 rules out the external forward-reverse shock model
directly and favors the "late internal shock model". These X-ray flares could
thus hint that the central engine operates again and a new unsteady
relativistic outflow is generated just a few minutes after the intrinsic hard
burst.


title:
Masers and the Massive Star Formation Process: New Insights Through
  Infrared Observations

abstract:
  Our mid-infrared and near-infrared surveys over the last five years have
helped to strengthen and clarify the relationships between water, methanol, and
OH masers and the star formation process. Our surveys show that maser emission
seems to be more closely associated with mid-infrared emission than cm radio
continuum emission from UC HII regions. We find that masers of all molecular
species surveyed trace a wide variety of phenomena and show a proclivity for
linear distributions. The vast majority of these linear distributions can be
explained by outflows or shocks, and in general do not appear to trace
circumstellar disks as was previously thought. Some water and methanol masers
that are not associated with radio continuum emission appear to trace
infrared-bright hot cores, the earliest observable stage of massive stellar
life before the onset of a UC HII region.


title: Inverse Compton X-ray Flare from GRB Reverse Shock

abstract:
  We study synchrotron self-inverse Compton radiation from a reverse-shocked
fireball. If the inverse Compton process dominates the cooling of shocked
electrons, an X-ray flare produced by the first order Compton scattering would
emerge in the very early afterglow phase, with the bulk of the shock energy
radiated in the second order scattering component at 10-100 MeV. The dominance
of inverse Compton cooling leads to the lack of prompt optical flashes. We show
that for plausible parameters this scattering process can produce an X-ray
flare with a relative amplitude change by a factor of several. Flares with a
larger amplitude and multiple X-ray flares in a single event are likely to be
produced by another mechanism (e.g. internal shocks).


title: Strange star equations of state revisited

abstract:
  Motivated by recent suggestions that strange stars can be responsible for
glitches and other observational features of pulsar, we review some possible
equations of state and their implications for models of neutron, hybrid and
strange stars. We consider the MIT bag model and also strange matter in the
color-flavored-locked phase. The central energy densities for strange stars are
higher than the central densities of ordinary neutron stars. Strange stars are
bound by the strong force and so can also rotate much faster than neutron
stars. These results are only weakly dependent on the model used for the quark
matter. If just one of the existing mass to radius ratio constraint is valid,
most neutron stars equations of state are ruled out, but all the strange stars
equations of state presented in this work remain consistent with the
constraint.


title:
Wide-Angle Wind Driven Bipolar Outflows: High Resolution Models with
  Application to Source I of the Becklin-Neugebauer / Kleinmann-Low OMC-I
  Region

abstract:
  We carry out high resolution simulations of the inner regions of a wide angle
wind driven bipolar outflow using an Adaptive Mesh Refinement code. Our code
follows H-He gas with molecular, atomic and ionic components and the associated
time dependent molecular chemistry and ionization dynamics with radiative
cooling. Our simulations explore the nature of the outflow when a spherical
wind expands into a rotating, collapsing envelope. We compare with key
observational properties of the outflow system of Source I in the BN/KL region.
  Our calculations show that the wind evacuates a bipolar outflow cavity in the
infalling envelope. We find the head of the outflow to be unstable and that it
rapidly fragments into clumps. We resolve the dynamics of the strong shear
layer which defines the side walls of the cavity. We conjecture that this layer
is the likely site of maser emission and examine its morphology and rotational
properties. The shell of swept up ambient gas that delineates the cavity edge
retains its angular momentum. This rotation is roughly consistent with that
observed in the Source I SiO maser spots. The observed proper motions and
line-of-sight velocity are approximately reproduced by the model. The cavity
shell at the base of the flow assumes an X-shaped morphology which is also
consistent with Source I. We conclude that the wide opening angle of the
outflow is evidence that a wide-angle wind drives the Source I outflow and not
a collimated jet.


title:
Three-Dimensional Numerical Simulations of Thermal-Gravitational
  Instability in Protogalactic Halo Environment

abstract:
  We study thermal-gravitational instability in simplified models for
protogalactic halos using three-dimensional hydrodynamic simulations. The
simulations followed the evolution of gas with radiative cooling down to T =
10^4 K, background heating, and self-gravity. Then cooled and condensed clouds
were identified and their physical properties were examined in detail. During
early stage clouds start to form around initial density peaks by thermal
instability. Small clouds appear first and they are pressure-bound.
Subsequently, the clouds grow through compression by the background pressure as
well as gravitational infall. During late stage cloud-cloud collisions become
important, and clouds grow mostly through gravitational merging.
Gravitationally bound clouds with mass M_c > ~6 X 10^6 Msun are found in the
late stage. They are approximately in virial equilibrium and have radius R_c =
\~150 - 200 pc. Those clouds have gained angular momentum through tidal torque
as well as merging, so they have large angular momentum with the spin parameter
<lambda_s> ~ 0.3. The clouds formed in a denser background tend to have smaller
spin parameters. We discuss briefly the implications of our results on the
formation of protoglobular cluster clouds in protogalactic halos. (abridged)


title: Stellar evolutionary models: uncertainties and systematics

abstract:
  In this last decade, our knowledge of evolutionary and structural properties
of stars of different mass and chemical composition is significantly improved.
This result has been achieved as a consequence of our improved capability in
understanding and describing the physical behavior of stellar matter in the
different thermal regimes characteristic of the different stellar mass ranges
and/or evolutionary stages. This notwithstanding, current generation of stellar
models is still affected by significant and, usually, not negligible
uncertainties. These uncertainties are related to our poor knowledge of some
physical procceses occurring in the real stars such as, for instance, some
thermodynamical processes, nuclear reaction rates, as well as the efficiency of
mixing processes. These drawbacks of stellar models have to be properly taken
into account when comparing theory with observations in order to derive
relevant information about the properties of both resolved and unresolved
stellar populations. In this paper we review current uncertainties affecting
low-mass stellar models, i.e. those structures with mass in the range between
0.6Mo and 1.4Mo. We show what are the main sources of uncertainty along the
main evolutionary stages, and discuss the present level of agreement between
theory and observations concerning some selected features of the
Color-Magnitude Diagram of low-mass stars.


title:
Lepton asymmetry and primordial nucleosynthesis in the era of precision
  cosmology

abstract:
  We calculate and display the primordial light-element abundances as a
function of a neutrino degeneracy parameter \xi common to all flavors. It is
the only unknown parameter characterizing the thermal medium at the primordial
nucleosynthesis epoch. The observed primordial helium abundance Y_p is the most
sensitive cosmic ``leptometer.'' Adopting the conservative Y_p error analysis
of Olive and Skillman implies -0.04 \alt \xi \alt 0.07 whereas the errors
stated by Izotov and Thuan imply \xi=0.0245+-0.0092 (1 sigma). Improved
determinations of the baryon abundance have no significant impact on this
situation. A determination of Y_p that reliably distinguishes between a
vanishing or nonvanishing \xi is a crucial test of the cosmological standard
assumption that sphaleron effects equilibrate the cosmic lepton and baryon
asymmetries.


title: Report by the ESA-ESO Working Group on Extra-Solar Planets

abstract:
  Various techniques are being used to search for extra-solar planetary
signatures, including accurate measurement of radial velocity and positional
(astrometric) displacements, gravitational microlensing, and photometric
transits. Planned space experiments promise a considerable increase in the
detections and statistical knowledge arising especially from transit and
astrometric measurements over the years 2005-15, with some hundreds of
terrestrial-type planets expected from transit measurements, and many thousands
of Jupiter-mass planets expected from astrometric measurements.
  Beyond 2015, very ambitious space (Darwin/TPF) and ground (OWL) experiments
are targeting direct detection of nearby Earth-mass planets in the habitable
zone and the measurement of their spectral characteristics. Beyond these, `Life
Finder' (aiming to produce confirmatory evidence of the presence of life) and
`Earth Imager' (some massive interferometric array providing resolved images of
a distant Earth) appear as distant visions.
  This report, to ESA and ESO, summarises the direction of exo-planet research
that can be expected over the next 10 years or so, identifies the roles of the
major facilities of the two organisations in the field, and concludes with some
recommendations which may assist development of the field.
  The report has been compiled by the Working Group members and experts over
the period June-December 2004.


title: Rotational modulation of X-ray emission in Orion Nebula young stars

abstract:
  We investigate the spatial distribution of X-ray emitting plasma in a sample
of young Orion Nebula Cluster stars by modulation of their X-ray light-curves
due to stellar rotation. The study, part of the Chandra Orion Ultradeep Project
(COUP), is made possible by the exceptional length of the observation: 10 days
of ACIS integration during a time span of 13 days, yielding a total of 1616
detected sources in the 17x17 arcmin field of view. We here focus on a
subsample of 233 X-ray-bright stars with known rotational periods. We search
for X-ray modulation using the Lomb Normalized Periodogram method.
  X-ray modulation related to the rotation period is detected in at least 23
stars with periods between 2 and 12 days and relative amplitudes ranging from
20% to 70%. In 16 cases, the X-ray modulation period is similar to the stellar
rotation period while in seven cases it is about half that value, possibly due
to the presence of X-ray emitting structures at opposite stellar longitudes.
These results constitute the largest sample of low mass stars in which X-ray
rotational modulation has been observed. The detection of rotational modulation
indicates that the X-ray emitting regions are distributed inhomogeneneously in
longitude and do not extend to distances significantly larger than the stellar
radius. Modulation is observed in stars with saturated activity levels
(L_X/L_bol ~ 10^(-3)) showing that saturation is not due to the filling of the
stellar surface with X-ray emitting regions.


title: Speckle observations of binary stars with a 0.5 m telescope

abstract:
  We present 36 observations of 17 visual binaries of moderate separation
(range from 0.15'' to 0.79'') made with the 50 cm Cassegrain telescope of the
Jagiellonian University in Cracow. The speckle interferometry technique was
combined with modest optical hardware and a standard photometric CCD camera. We
used broad-band V,R,I filters without a Risley prism to reduce differential
colour refraction, so we performed model analysis to investigate the influence
of this effect on the results of measurements. For binary components of
spectral type O-F, the difference of three spectral classes between them should
bias their relative positions by no more than a couple of tens of
milliarcseconds (mas) for moderate zenith distances. The statistical analysis
of our results confirmed this conclusion. A cross-spectrum approach was applied
to resolve the quadrant ambiguity. Our separations have RMS deviations of
0.012'' and our position angles have RMS deviations of 1.8 deg. Relative
photometry in V, R and I filters appeared to be the less accurately determined
parameter. We discuss our errors in detail and compare them to other speckle
data. This comparison clearly shows the high value of our measurements. We also
present an example of the enhancement of image resolution for an extended
object of angular size greater than the atmospheric coherence patch using
speckle interferometry techniques.


title:
Late Arriving Particles in Cosmic Ray Air Showers and AGASA's
  Determination of UHECR Energies

abstract:
  We give the first detailed study of the arrival time distribution of nucleons
in UHECR air showers. We analyze in detail the influence of late arriving
particles on the energy determination of the AGASA experiment, as well as how
the arrival time distribution changes with distance from shower core. Our
calculations are consistent with experimental observations of the AGASA group.
Crucial to obtaining agreement, is the correct implementation of the energy
loss for low-energy protons. We confirm AGASA's estimation of the error in
their energy determination associated with late-arriving particles, assuming
primary protons.


title: X-ray Emission from the Weak-lined T Tauri Binary System KH 15D

abstract:
  The unique eclipsing, weak-lined T Tauri star KH 15D has been detected as an
X-ray source in a 95.7 ks exposure from the Chandra X-ray Observatory archives.
A maximum X-ray luminosity of 1.5 x 10^{29} erg s$^{-1}$ is derived in the
0.5--8 keV band, corresponding to L_{X}/L_bol = 7.5 x 10^{-5}. Comparison with
samples of stars of similar effective temperature in NGC 2264 and in the Orion
Nebula Cluster shows that this is about an order of magnitude low for a typical
star of its mass and age. We argue that the relatively low luminosity cannot be
attributed to absorption along the line of sight but implies a real deficiency
in X-ray production. Possible causes for this are considered in the context of
a recently proposed eccentric binary model for KH 15D. In particular, we note
that the visible component rotates rather slowly for a weak-lined T Tauri star
and has possibly been pseudosynchronized by tidal interaction with the primary
near periastron.


title:
A Candidate Neutron Star Associated with Galactic Center Supernova
  Remnant Sagittarius A East

abstract:
  We present imaging and spectral studies of the supernova remnant (SNR)
Sagittarius (Sgr) A East from deep observations with the {\it Chandra X-Ray
Observatory}. The spatially-resolved spectral analysis of Sgr A East reveals
the presence of a two-temperature thermal plasma ($kT$ $\sim$ 1 keV and 5 keV)
near the center of the SNR. The central region is dominated by emission from
highly-ionized Fe-rich ejecta. We estimate a conservative upper limit on the
total Fe ejecta mass of the SNR, M$_{Fe}$ $<$ 0.27 M$_{\odot}$. Comparisons
with standard SN nucleosynthesis models suggest that this Fe mass limit is
consistent with a Type II SN explosion for the origin of Sgr A East. On the
other hand, the soft X-ray emission extending toward the north of the SNR can
be described by a single-temperature ($kT$ $\sim$ 1.3 keV) thermal plasma with
normal chemical composition. This portion of the SNR is thus X-ray emission
from the heated interstellar medium rather than the metal-rich stellar ejecta.
We point out that a hard pointlike source CXOGC J174545.5$-$285829 (the
so-called ``cannonball'') at the northern edge of the SNR shows unusual X-ray
characteristics among other Galactic center sources. The morphological,
spectral, and temporal characteristics of this source suggest an identification
as a high-velocity neutron star. Based on the suggested Type II origin for the
SNR Sgr A East and the proximity between the two, we propose that CXOGC
J174545.5$-$285829 is a high-velocity neutron star candidate, born from the
core-collapse SN which also created the SNR Sgr A East.


title:
Radio, millimeter and optical monitoring of GRB030329 afterglow:
  Constraining the double jet model

abstract:
  We present radio, millimeter and optical observations of the afterglow of
GRB030329. UBVR_{C}I_{C} photometry is presented for a period of 3 hours to 34
days after the burst. Radio monitoring at 1280 MHz has been carried out using
the GMRT for more than a year. Simultaneous millimeter observations at 90 GHz
and 230 GHz have been obtained from the Swedish-ESO Submillimeter Telescope
(SEST) and the IRAM-PdB interferometer over more than a month following the
burst. We use these data to constrain the double jet model proposed by Berger
et al. (2003) for this afterglow. We also examine whether instead of the two
jets being simultaneously present, the wider jet could result from the
initially narrow jet, due to a fresh supply of energy from the central engine
after the ``jet break''.


title: Swift, INTEGRAL, RXTE, and Spitzer reveal IGR J16283-4838

abstract:
  We present the first combined study of the recently discovered source IGR
J16283-4838 with Swift, INTEGRAL, and RXTE. The source, discovered by INTEGRAL
on April 7, 2005, shows a highly absorbed (variable N_H = 0.4 - 1.7 x 1e23
1/cm**2) and flat (photon index = 1) spectrum in the Swift/XRT and RXTE/PCA
data. No optical counterpart is detectable (V > 20 mag), but a possible
infrared counterpart within the Swift/XRT error radius is detected in the 2MASS
and Spitzer/GLIMPSE survey. The observations suggest that IGR J16283-4838 is a
high mass X-ray binary containing a neutron star embedded in Compton thick
material. This makes IGR J16283-4838 a member of the class of highly absorbed
HMXBs, discovered by INTEGRAL.


title: Characterizing the Cluster Lens Population

abstract:
  We present a detailed investigation into which properties of CDM halos make
them effective strong gravitational lenses. Strong lensing cross sections of
878 clusters from an N-body simulation are measured by ray tracing through
13,594 unique projections. We measure concentrations, axis ratios,
orientations, and the amount of substructure of each cluster, and compare the
lensing weighted distribution of each quantity to that of the cluster
population as a whole. The concentrations of lensing clusters are on average
34% larger than the typical cluster in the Universe. Despite this bias, the
anomalously high concentrations (c >14) recently measured by several groups,
appear to be inconsistent with the concentration distribution in our
simulations, which predict < 2% of lensing clusters should have concentrations
this high. No correlation is found between lensing cross section and the amount
of substructure. We introduce several types of simplified dark matter halos,
and use them to isolate which properties of CDM clusters make them effective
lenses. Projections of halo substructure onto small radii and the large scale
mass distribution of clusters do not significantly influence cross sections.
The abundance of giant arcs is primarily determined by the mass distribution
within an average overdensity of ~ 10,000. A multiple lens plane ray tracing
algorithm is used to show that projections of large scale structure increase
the giant arc abundance by a modest amount <7%. We revisit the question of
whether there is an excess of giant arcs behind high redshift clusters in the
RCS survey and find that the number of high redshift (z > 0.6) lenses is in
good agreement with LCDM, although our simulations predict more low redshift (z
< 0.6) lenses than were observed. (abridged)


title:
The Long Term Optical Variability of the BL Lac object S5 0716+714:
  Evidence for a Precessing Jet

abstract:
  We present the historic light curve of the BL Lac object S5 0716+714,
spanning the time interval from 1953 to 2003, built using Asiago archive plates
and our recent CCD observations, together with literature data. The source
shows an evident long term variability, over which well known short term
variations are superposed. In particular, in the period from 1961 to 1983 the
mean brightness of S5 0716+714 remained significantly fainter than that
observed after 1994. Assuming a constant variation rate of the mean magnitude
we can estimate a value of about 0.11 magnitude/year. The simultaneous
occurrence of decreasing ejection velocities of superluminal moving components
in the jet reported by Bach et al. (2005) suggests that both phenomena are
related to the change of the direction of the jet to the line of sight from
about 5 to 0.7 degrees for an approximately constant bulk Lorentz factor of
about 12. A simple explanation is that of a precessing relativistic jet, which
should presently be close to the smallest orientation angle. One can therefore
expect in the next ten years a decrease of the mean brightness of about 1
magnitude.


title: Impact of non-uniform surface magnetic fields on stellar winds

abstract:
  Observations of active stars reveal highly non-uniform surface distributions
of magnetic flux. Theoretical models considering magnetised stellar winds
however often presume uniform surface magnetic fields, characterised by a
single magnetic field strength. The present work investigates the impact of
non-uniform surface magnetic field distributions on the stellar mass and
angular momentum loss rates. The approach of Weber & Davis (1967) is extended
to non-equatorial latitudes to quantify the impact of latitude-dependent
magnetic field distributions over a large range of stellar rotation rates and
thermal wind properties. The analytically prescribed field patterns are
dominated by magnetic flux concentrations at intermediate and high latitudes.
The global stellar mass loss rates are found to be rather insensitive to
non-uniformities of the surface magnetic field. Depending on the non-uniformity
of the field distribution, the angular momentum loss rates deviate in contrast
at all rotation rates between -60% and 10% from the Weber & Davis-values, and
the effective Alfvenic radii up to about +/-25%. These large variations albeit
equal amounts of total magnetic flux indicate that a classification of stellar
surface magnetic fields through a single field strength is insufficient, and
that their non-uniformity has to be taken into account. The consequences for
applications involving magnetised stellar winds are discussed in view of the
rotational evolution of solar-like stars and of the observational determination
of their mass loss rates using the terminal velocity and ram pressure of the
wind. For rapidly rotating stars the latitudinal variation of the wind ram
pressure is found to exceed, depending on the actual field distribution on the
stellar surface, over two orders of magnitude.


title:
Simulation of the Gravitational Collapse and Fragmentation of Rotating
  Molecular Clouds

abstract:
  In this paper we study the process of the subsequent (runaway) fragmentation
of the rotating isothermal Giant Molecular Cloud (GMC) complex. Our own
developed Smoothed Particle Hydrodynamics (SPH) gas-dynamical model
successfully reproduce the observed Cloud Mass-distribution Function (CMF) in
our Galaxy (even the differences between the inner and outer parts of our
Galaxy). The steady state CMF is established during the collapse within a
free-fall timescale of the GMC. We show that one of the key parameters, which
defines the observed slope of the present day CMF, is the initial ratio of the
rotational (turbulent) and gravitational energy inside the fragmented GMC.


title: Statistics of Quasars Multiply Imaged by Galaxy Clusters

abstract:
  We compute the expected number of quasars multiply imaged by cluster size
dark halos for current wide field quasar surveys by carrying out a large
ensemble of ray tracing simulations through clusters from a cosmological N-body
simulation of the LCDM cosmology. Our calculation predicts ~ 4 quasar lenses
with splittings theta > 10" in the SDSS spectroscopic quasar sample, consistent
with the recent discovery of the wide separation lens SDSSJ1004+4112 which has
theta=14.6". The SDSS faint photometric quasar survey will contain ~12 multiply
imaged quasars with splittings theta > 10". Of these, ~ 2 will be lenses with
separations theta > 30", and ~ 2 will be at high redshift (z ~ 4).


title: The Intrinsic Properties of SMMJ14011+0252

abstract:
  We discuss the properties of the bright submillimeter source SMMJ14011+0252
at z=2.56 which lies behind the central regions of the z=0.25 lensing cluster
A1835. This system has a complex optical morphology consisting of at least five
separate components. We reassess the extensive multiwavelength observations of
this system and find strong support for the suggestion that one of these five
components represents a foreground galaxy. The spectral and morphological
properties of the foreground galaxy indicate that it is a low-luminosity,
passive early-type disk member of the A1835 cluster. We estimate the likely
properties of the dark matter halo of this galaxy from its stellar
distribution. Based on these estimates we suggest that, contrary to earlier
claims, this foreground galaxy is unlikely to significantly magnify the
background submillimeter source. Thus SMMJ14011+0252 probably represents an
intrinsically luminous submillimeter galaxy.


title:
Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda
  Galaxies

abstract:
  We describe a new set of self-consistent, equilibrium disk galaxy models that
incorporate an exponential disk, a Hernquist model bulge, an NFW halo and a
central supermassive black hole. The models are derived from explicit
distribution functions for each component and the large number of parameters
permit detailed modeling of actual galaxies. We present techniques that use
structural and kinematic data such as radial surface brightness profiles,
rotation curves and bulge velocity dispersion profiles to find the best-fit
models for the Milky Way and M31. Through N-body realizations of these models
we explore their stability against the formation of bars. The models permit the
study of a wide range of dynamical phenomenon with a high degree of realism.


title: Advances in Multi-Dimensional Simulation of Core-Collapse Supernovae

abstract:
  We discuss recent advances in the radiative-hydrodynamic modeling of core
collapse supernovae in multi-dimensions. A number of earlier attempts at fully
radiation-hydrodynamic models utilized either the grey approximation to
describe the neutrino distribution or utilized more sophisticated multigroup
transport methods restricted to radial rays. In both cases these models have
also neglected the O(v/c) terms that couple the radiation and matter strongly
in the optically thick regions of the collapsed core. In this paper we present
some recent advances that resolve some shortcomings of earlier models.


title: Diffusive Acceleration of Ions at Interplanetary Shocks

abstract:
  Heliospheric shocks are excellent systems for testing theories of particle
acceleration in their environs. These generally fall into two classes: (1)
interplanetary shocks that are linear in their ion acceleration
characteristics, with the non-thermal ions serving as test particles, and (2)
non-linear systems such as the Earth's bow shock and the solar wind termination
shock, where the accelerated ions strongly influence the magnetohydrodynamic
structure of the shock. This paper explores the modelling of diffusive
acceleration at a particular interplanetary shock, with an emphasis on
explaining in situ measurements of ion distribution functions. The
observational data for this event was acquired on day 292 of 1991 by the
Ulysses mission. The modeling is performed using a well-known kinetic Monte
Carlo simulation, which has yielded good agreement with observations at several
heliospheric shocks, as have other theoretical techniques, namely hybrid plasma
simulations, and numerical solution of the diffusion-convection equation. In
this theory/data comparison, it is demonstrated that diffusive acceleration
theory can, to first order, successfully account for both the proton
distribution data near the shock, and the observation of energetic protons
farther upstream of this interplanetary shock than lower energy pick-up
protons, using a single turbulence parameter. The principal conclusion is that
diffusive acceleration of inflowing upstream ions can model this pick-up
ion-rich event without the invoking any seed pre-acceleration mechanism, though
this investigation does not rule out the action of such pre-acceleration.


title:
Zn and Cr abundances in damped Lyman alpha systems from the CORALS
  survey

abstract:
  We present metal abundances in 15 damped Lyman alpha systems (DLAs) from the
Complete Optical and Radio Absorption Line System (CORALS) survey, designed to
be free from any biasing effects due to extinction of QSOs by dust in
intervening absorbers. It has long been suggested that such biasing may explain
differences in metallicity between DLAs and coeval luminous galaxies, and
between model predictions and observations. We use our measured zinc and
chromium abundances (combined with those for five more CORALS DLAs from the
literature, giving us a very nearly complete sample) to test whether the
metallicity and degree of dust depletion in CORALS DLAs are significantly
different from those of existing, larger, samples of DLAs drawn from magnitude
limited, optical surveys. We find that the column density weighted metallicity
of CORALS DLAs, [<(Zn/H)_DLA>] = -0.88 +/- 0.21 in the redshift interval 1.86 <
z(abs) < 3.45, is only marginally higher than that of a control sample from the
recent compilation by Kulkarni et al., [<(Zn/H)_DLA>] = -1.09 +/- 0.10. With
the present limited statistics this difference is not highly significant.
Furthermore, we find no evidence for increased dust depletions in CORALS
DLAs--their [Cr/Zn] ratios conform to the known trend of increasing depletion
(decreasing [Cr/Zn]) with increasing metallicity, and we have encountered no
cases where Cr is as depleted as in local cold interstellar clouds. These
results, when combined with the earlier findings of the CORALS survey reported
by Ellison et al. in 2001, make it difficult to invoke a dust-induced bias to
explain the generally low level of chemical evolution exhibited by most DLAs.
Rather, they indicate that large scale optical QSO surveys give a fair census
of the population of high redshift absorbers.


title: Gravitational waves from remnants of ultraluminous X-ray sources

abstract:
  Ultraluminous X-ray sources (ULXs) with X-ray luminosities larger than the
Eddington luminosity of stellar mass objects may be powered by intermediate
mass black holes (IBHs) of masses Mbh~10^3Msun. If IBHs form in young dense
stellar clusters, they can be fed by Roche lobe overflow from a tidally
captured massive (Ms>10Msun) stellar companion. After the donor leaves the main
sequence it forms a compact remnant, which spirals in due to gravitational wave
(GW) emission. We show that space based detectors such as the Laser
Interferometer Space Antenna are likely to detect several of these sources. GW
sources stemming from this scenario have small eccentricities which give
distinct GW signals. Detection of such a GW signal will unambiguously prove the
existence of IBHs, and support the hypothesis that some ULXs are powered by
IBHs with captured companions.


title:
The "Solar Model Problem" Solved by the Abundance of Neon in Stars of
  the Local Cosmos

abstract:
  The interior structure of the Sun can be studied with great accuracy using
observations of its oscillations, similar to seismology of the Earth. Precise
agreement between helioseismological measurements and predictions of
theoretical solar models has been a triumph of modern astrophysics (Bahcall et
al. 2005). However, a recent downward revision by 25-35% of the solar
abundances of light elements such as C, N, O and Ne (Asplund et al. 2004) has
broken this accordance: models adopting the new abundances incorrectly predict
the depth of the convection zone, the depth profiles of sound speed and
density, and the helium abundance (Basu Antia 2004, Bahcall et al. 2005). The
discrepancies are far beyond the uncertainties in either the data or the model
predictions (Bahcall et al. 2005b). Here we report on neon abundances relative
to oxygen measured in a sample of nearby solar-like stars from their X-ray
spectra. They are all very similar and substantially larger than the recently
revised solar value. The neon abundance in the Sun is quite poorly determined.
If the Ne/O abundance in these stars is adopted for the Sun the models are
brought back into agreement with helioseismology measurements (Antia Basu 2005,
Bahcall et al. 2005c).


title: Systematic Analysis of 22 Microlensing Parallax Candidates

abstract:
  We attempt to identify all microlensing parallax events for which the
parallax fit improves \Delta\chi^2 > 100 relative to a standard microlensing
model. We outline a procedure to identify three types of discrete degeneracies
(including a new one that we dub the ``ecliptic degeneracy'') and find many new
degenerate solutions in 16 previously published and 6 unpublished events. Only
four events have one unique solution and the other 18 events have a total of 44
solutions. Our sample includes three previously identified black-hole (BH)
candidates. We consider the newly discovered degenerate solutions and determine
the relative likelihood that each of these is a BH. We find the lens of event
MACHO-99-BLG-22 is a strong BH candidate (78%), event MACHO-96-BLG-5 is a
marginal BH candidate (37%), and MACHO-98-BLG-6 is a weak BH candidate (2.2%).
The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating planet
candidate based on a weak 3 sigma detection of finite-source effects. We find
that event MACHO-179-A is a brown dwarf candidate within ~100 pc of the Sun,
mostly due to its very small projected Einstein radius, \tilde r_E = 0.23+-0.05
AU. As expected, these microlensing parallax events are biased toward lenses
that are heavier and closer than average. These events were examined for
xallarap (or binary-source motion), which can mimic parallax. We find that 23%
of these events are strongly affected by xallarap.


title:
Three routes to jet collimation by the Balbus-Hawley magnetorotational
  instability

abstract:
  Three completely different lines of work have recently led to the conclusion
that the magnetorotational instability (MRI) may create a hoop-stress that
collimates jets. One argument is based upon consideration that
magnetohydrodynamic turbulence, in general, and turbulence driven by the MRI,
in particular, is more nearly viscoelastic than it is viscous. Another argument
is based upon the dispersion relation for the MRI in the context of 1D
simulations of core collapse. Yet a third argument rests in the results of
direct numerical magnetohydrodynamic simulations of collapsars and thick
accretion flows. I elaborate on my previous work regarding the first argument
above and I briefly discuss how these three sets of results are all related. I
also discuss the different roles played by the magnetic tension and the
magnetic pressure within the context of this work. I point out that this leads
to consideration of the normal stress difference between the hoop stress and
the radial stress, in preference to a focus on just the hoop stress itself.
Additionally, I argue that simulations of thick accretion flows and collapsars
are not self-consistent if they include a phenomenological model for an
MRI-induced viscous stress but disregard these other MRI-induced stress
components. I comment briefly on the RHESSI observation of polarization in the
gamma-ray burst GRB0212206. I argue that this polarization is consistent with a
tangled field, and does not require a large-scale organized field. Finally I
suggest that the role of magnetic fields in creating jets, as described here,
should be understood not to work within the confines of magnetocentrifugal
models of jets, but rather as an alternative to them.


title:
X-ray Diagnostics of Grain Depletion in Matter Accreting onto T Tauri
  Stars

abstract:
  Recent analysis of high resolution Chandra X-ray spectra has shown that the
Ne/O abundance ratio is remarkably constant in stellar coronae. Based on this
result, we point out the utility of the Ne/O ratio as a discriminant for
accretion-related X-rays from T Tauri stars, and for probing the measure of
grain-depletion of the accreting material in the inner disk. We apply the Ne/O
diagnostic to the classical T Tauri stars BP Tau and TW Hya--the two stars
found to date whose X-ray emission appears to originate, at least in part, from
accretion activity. We show that TW Hya appears to be accreting material which
is significantly depleted in O relative to Ne. In constrast, BP Tau has an Ne/O
abundance ratio consistent with that observed for post-T Tauri stars. We
interpret this result in terms of the different ages and evolutionary states of
the circumstellar disks of these stars. In the young BP Tau disk (age 0.6 Myr)
dust is still present near the disk corotation radius and can be ionized and
accreted, re-releasing elements depleted onto grains. In the more evolved TW
Hya disk (age 10 Myr), evidence points to ongoing coagulation of grains into
much larger bodies, and possibly planets, that can resist the drag of
inward-migrating gas, and accreting gas is consequently depleted of
grain-forming elements.


title: Infrared Echoes near the Supernova Remnant Cassiopeia A

abstract:
  Two images of Cassiopeia A obtained at 24 micrometer with the Spitzer Space
Telescope over a one year time interval show moving structures outside the
shell of the supernova remnant to a distance of more than 20 arcmin. Individual
features exhibit apparent motions of 10 to 20 arcsec per year, independently
confirmed by near-infrared observations. The observed tangential velocities are
at roughly the speed of light. It is likely that the moving structures are
infrared echoes, in which interstellar dust is heated by the explosion and by
flares from the compact object near the center of the remnant.


title: Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective

abstract:
  We present a sensitive, multiwavelength submillimeter continuum survey of 153
young stellar objects in the Taurus-Auriga star formation region. The
submillimeter detection rate is 61% to a completeness limit of ~10 mJy
(3-sigma) at 850 microns. The inferred circumstellar disk masses are
log-normally distributed with a mean mass of ~0.005 solar masses and a large
dispersion (0.5 dex). Roughly one third of the submillimeter sources have disk
masses larger than the minimal nebula from which the solar system formed. The
median disk to star mass ratio is 0.5%. The empirical behavior of the
submillimeter continuum is best described as F_nu ~ nu^(2.0 +/- 0.5) between
350 microns and 1.3 mm, which we argue is due to the combined effects of the
fraction of optically thick emission and a flatter frequency behavior of the
opacity compared to the ISM. This latter effect could be due to a substantial
population of large dust grains, which presumably would have grown through
collisional agglomeration. In this sample, the only stellar property that is
correlated with the outer disk is the presence of a companion. We find evidence
for significant decreases in submillimeter flux densities, disk masses, and
submillimeter continuum slopes along the canonical infrared spectral energy
distribution evolution sequence for young stellar objects. The fraction of
objects detected in the submillimeter is essentially identical to the fraction
with excess near-infrared emission, suggesting that dust in the inner and outer
disk are removed nearly simultaneously.


title:
Discovery of Three Wide-orbit Binary Pulsars: Implications for Binary
  Evolution and Equivalence Principles

abstract:
  We report the discovery of three binary millisecond pulsars during the Parkes
Multibeam Pulsar Survey of the Galactic Plane. The objects are highly recycled
and are in orbits of many tens of days about low-mass white-dwarf companions.
The eccentricity of one object, PSR J1853+1303, is more than an order of
magnitude lower than predicted by the theory of convective fluctuations during
tidal circularization. We demonstrate that, under the assumption that the
systems are randomly oriented, current theoretical models of the
core-mass--orbital-period relation for the progenitors of these systems likely
overestimate the white-dwarf masses, strengthening previous concerns about the
match of these models to the data. The new objects allow us to update the
limits on violation of relativistic equivalence principles to 95% confidence
upper limits of 5.6 x 10^-3 for the Strong Equivalence Principle parameter
Delta and 4.0 x 10^-20 for the Lorentz-invariance/momentum-conservation
parameter alpha_3.


title: Cluster Populations in Abell 2125 and 2218

abstract:
  We combine new narrow band photometry with archival WFPC2 data for A2218
($z$=0.18) and A2125 ($z$=0.25), two clusters with intermediate redshifts but
very different cluster properties, in order to examine the evolution of galaxy
populations. A2218 is a dense, elliptical-rich cluster (Bautz-Morgan type II)
similar to Coma in its evolutionary appearance; whereas, A2125 is a less dense,
more open cluster (Bautz-Morgan type II-III), although similar in richness to
A2218. The color-magnitude relation indicates that A2125 has a more developed
blue population than A2218 (the Butcher-Oemler effect), although both clusters
have significant numbers of blue galaxies (ranging in star formation rates from
normal, star-forming disks to starburst systems) as compared to a present-day
cluster. The colors of the red populations are identical in A2125 and A2218 and
well fit by passive evolution models. We are able, for the first time, to
combine archived WFPC2 images with our narrow band photometry for a color,
morphological and structural analysis of the blue Butcher-Oemler population. We
find the blue population to composed of two sub-populations, a bright, spiral
population and a fainter, dwarf starburst population. A2125 is richer in bright
starburst systems, apparently induced by the cluster's younger dynamical state.
In addition, a majority of the S0 population in A2125 and A2218 is composed of
bulge+disk systems, whereas, nearby clusters such as Coma are composed
primarily of lenticulars (pure disk S0's). The structural parameters of the S0
bulges in A2125/A2218 are identical to the structure parameters of cluster
ellipticals suggesting that the disks of some S0's in intermediate redshift
clusters are stripped away with the leftover bulges evolving into present-day
ellipticals.


title: Understanding our Origins: Star Formation in H II Region Environments

abstract:
  Recent analysis of the decay products of short-lived radiounclides (SLRs) in
meteorites, in particular the confirmation of the presence of live 60Fe in the
early Solar System, provides unambiguous evidence that the Sun and Solar System
formed near a massive star. We consider the question of the formation of
low-mass stars in environments near massive stars, presenting a scenario for
the evolution of a star and its disk around the periphery of an expanding H II
region. The stages in this scenario begin with compression of molecular gas
around the edge of an H II region, continue as forming stars are overrun by the
advancing ionization front, and culminate when ejecta from one or more nearby
supernova explosions sweeps over YSO disks located in the low density interior
of the H II region, injecting SLRs including 26Al and 60Fe. We review the
evidence that this mode of star formation is more characteristic of formation
of low-mass stars than is the mode of star formation seen in regions such as
the Taurus-Auriga molecular cloud. We discuss the implications of this scenario
for our understanding of star formation, as well as the effects of the young
Sun's astrophysical environment on the formation and evolution of the Solar
System. We conclude that low-mass stars and their accompanying disks form and
evolve very differently near massive stars than they do in regions like
Taurus-Auriga, and that these differences have profound implications for our
understanding of our origins.


title: GRB-supernovae: a new spin on gravitational waves

abstract:
  The discovery of the GRB-supernova association poses the question on the
nature of the inner engine as the outcome of Type Ib/c supernovae. These events
are believed to represent core-collapse of massive stars, probably in
low-period stellar binaries and similar but not identical to the Type II event
SN1987A. The branching ratio of Type Ib/c supernovae into GRB-supernovae has
the remarkably small value of less than 0.5%. These observational constraints
point towards a rapidly rotating black hole formed at low probability with low
kick velocity. The putative black hole hereby remains centered, and matures
into a high-mass object with large rotational energy in angular momentum. As
the MeV-neutrino emissions from SN1987A demonstrate, the most powerful probe of
the inner workings of core-collapse events are radiation channels to which the
remnant envelope is optically thin. We here discuss the prospect of
gravitational-wave emissions powered by a rapidly rotating central black hole
which, in contrast to MeV-neutrinos, can be probed to distances as large as
100Mpc through upcoming gravitational-wave detectors LIGO and Virgo. We
identify the GRB-emissions, commonly attributed to ultrarelativistic
baryon-poor ejecta, with a new process of linear acceleration of charged
particles along the axis of rotation of a black hole in response to spin-orbit
coupling. We include some preliminary numerical simulations on internal shocks
produced by intermittent ejecta. The results showing a radial splash, which
points towards low-luminosity and lower-energy radiation at large angles,
possibly related to X-ray flashes.


title:
Density-potential pairs for spherical stellar systems with Sersic
  light-profiles and (optional) power-law cores

abstract:
  Popular models for describing the luminosity-density profiles of dynamically
hot stellar systems (e.g., Jaffe, Hernquist, Dehnen) were constructed with the
desire to match the deprojected form of an R^{1/4} light-profile. Real
galaxies, however, are now known to have a range of different light-profile
shapes that scale with mass. Consequently, although highly useful, the above
models have implicit limitations, and this is illustrated here through their
application to a number of real galaxy density profiles. On the other hand, the
analytical density profile given by Prugniel & Simien (1997) closely matches
the deprojected form of Sersic R^{1/n} light-profiles - including deprojected
exponential light-profiles. It is thus applicable for describing bulges in
spiral galaxies, dwarf elliptical galaxies, and both ordinary and giant
elliptical galaxies. Here we provide simple equations, in terms of elementary
and special functions, for the gravitational potential and force associated
with this density profile. Furthermore, to match galaxies with partially
depleted cores, and better explore the supermassive black hole / galaxy
connection, we have added a power-law core to this density profile and derived
similar expressions for the potential and force of this hybrid profile.
Expressions for the mass and velocity dispersion, assuming isotropy, are also
given. These models may also prove appropriate for describing the dark matter
distribution in halos formed from LCDM cosmological simulations.


title:
Faint Radio Sources in the NOAO Bootes Field. VLBA Imaging and Optical
  Identifications

abstract:
  As a step toward investigating the parsec-scale properties of faint
extragalactic radio sources, the Very Long Baseline Array (VLBA) was used at
5.0 GHz to obtain phase-referenced images of 76 sources in the NOAO Bootes
field. These 76 sources were selected from the FIRST catalog to have peak flux
densities above 10 mJy at 5 arcsec resolution and deconvolved major diameters
of less than 3 arcsec at 1.4 GHz. Fifty-seven of these faint radio sources were
identified with accretion-powered radio galaxies and quasars brighter than 25.5
mag in the optical I band. On VLA scales at 1.4 GHz, a measure of the
compactness of the faint sources (the ratio of the peak flux density from FIRST
to the integrated flux density from the NVSS catalog) spans the full range of
possibilites arising from source-resolution effects. Thirty of the faint radio
sources, or 39 +9/-7%, were detected with the VLBA at 5.0 GHz with peak flux
densities above 6 sigma ~2 mJy at 2 mas resolution. The VLBA detections occur
through the full range of compactness ratios. The stronger VLBA detections can
themselves serve as phase-reference calibrators, boding well for opening up
much of the radio sky to VLBA imaging. For the adopted cosmology, the VLBA
resolution correponds to 17 pc or finer. Most VLBA detections are unresolved or
slightly resolved but one is diffuse and five show either double or core-jet
structures; the properties of these latter six are discussed in detail. Three
VLBA detections are unidentified and fainter than 25.5 mag in the optical I
band; their properties are highlighted because they likely mark
optically-obscured active nuclei at high redshift.


title: Fourier Phase Analysis of SDSS Galaxies

abstract:
  We present a first analysis of the clustering of SDSS galaxies using the
distribution function of the sum of Fourier phases. This statistic was recently
proposed by one of authors as a new method to probe phase correlations of
cosmological density fields. Since the Fourier phases are statistically
independent of Fourier amplitudes, the phase statistic plays a complementary
role to the conventional two-point statistics of galaxy clustering. In
particular, we focus on the distribution functions of phase sum over three
closed wavevectors as a function of the configurations of triangle wavevectors.
We find that the observed distribution functions of phase sum are in good
agreement with the lowest-order approximation from perturbation theory. For
direct comparison with observations, we construct mock catalogs from N-body
simulations taking account of several observational effects such as the survey
geometry, the redshift distortion, and the discreteness due to the limited
number of data. Indeed the observed phase correlations for the galaxies in the
range of absolute magnitude -22<Mr<-18 agree well with those for Lambda CDM
predictions with sigma8=0.9 evolved from Gaussian initial condition. This
agreement implies that the galaxy biasing is approximately linear in redshift
space. Instead, assuming that the galaxy biasing is described by a quadratic
deterministic function at scale larger than 30Mpc/h, we can constrain the ratio
of the quadratic biasing parameter b2 to the linear biasing parameter b1. We
find that resulting b2/b1 is mainly dependent on sigma8 and that it is well
fitted by b2/b1=0.54(+-0.06)-0.62(+-0.08)sigma8 in CDM models. Indeed, b2/b1 is
nearly zero when sigma8=0.9.


title: Probing 3-D matter distribution at z~2 with QSO multiple lines of sight

abstract:
  We investigate the 3-D matter distribution at z~2 with high resolution (R ~
40000) spectra of QSO pairs and groups obtained with the UVES spectrograph at
ESO VLT. Our sample is unique for the number density of objects and the variety
of separations, between 0.5 and 7 proper Mpc. We compute the real space
cross-correlation function of the Lyman-alpha forest transmitted fluxes. There
is a significant clustering signal up to ~2 proper Mpc, which is still present
when absorption lines with high column density (log N > 13.8) are excluded.


title: Kaon condensation in the quark-meson coupling model and compact stars

abstract:
  The properties of neutron stars constituted of a crust of hadrons and an
internal part of hadrons and kaon condensate are calculated within the
quark-meson-coupling model. We have considered stars with nucleons only in the
hadron phase and also stars with hyperons as well. The results are compared
with the ones obtained from the non-linear Walecka model for the hadronic
phase.


title: The stellar populations of local dwarfs

abstract:
  Recent progress in our knowledge of stellar populations in local dwarf
spheroidal galaxies is briefly discussed. A few results are summarized
including wide field observations of stellar populations and their spatial
variations, studies of AGB and variable stars, extension to near-infrared
wavelengths, and the interpretation effort based on synthetic color-magnitude
diagrams and chemical evolution models.


title:
Two and a half years of GRB localizations with the INTEGRAL Burst Alert
  System

abstract:
  We review the results on Gamma-ray Bursts obtained during the first two and a
half years of operations of the INTEGRAL Burst Alert System (IBAS). In many
cases GRB coordinates have been distributed with an unprecedented combination
of accuracy (3 arcmin) and speed (20-30 s). The resulting rapid follow-ups at
other wavelengths, including sensitive XMM-Newton and Swift observations, have
led to several interesting results.


title:
Is the Bursting Radio-source GCRT J1745-3009 a Double Neutron Star
  Binary ?

abstract:
  GCRT J1745-3009 is a peculiar transient radio-source in the direction of the
Galactic Center. It was observed to emit a series of ~ 1 Jy bursts at 0.33 GHz,
with typical duration ~ 10 min and at apparently regular intervals of ~ 77 min.
If the source is indeed at the distance of the Galactic Center as it seems
likely, we show that its observational properties are compatible with those
expected from a double neutron star binary, similar to the double pulsar system
J0737-3039. In the picture we propose the (coherent) radio emission comes from
the shock originating in the interaction of the wind of the more energetic
pulsar with the magnetosphere of the companion. The observed modulation of the
radio signal is the consequence of an eccentric orbit, along which the
separation between the two stars varies. This cyclically drives the shock
inside the light cylinder radius of the less energetic pulsar.


title:
Dynamical quintessence fields Press-Schechter mass function:
  detectability and effect on dark haloes

abstract:
  We present an investigations on the influence of dynamical quintessence field
models on the formation of non-linear structures. In particular, we focus on
the structure traced by the mass function. Our contribution builds on previous
studies by considering two potentials not treated previousy and investigating
the impact of the free parameters of two other models. Our approach emphasises
the physical insight into the key role of the evolution of the equation of
state. We use the variations in the spherical non-linear collapse caused by
quintessence as a function of the model's potential in a Press Schechter scheme
to obtain the differences in halo mass functions. The comparison is also done
with the more usual scenario $\Lambda$CDM. We conclude the method should be
promissing for discrimination using cluster mass determination and that the key
role lies within the evolution of the equation of state.


title:
RASS-SDSS Galaxy Cluster Survey. IV. A ubiquitous dwarf galaxy
  population in clusters

abstract:
  We analyze the Luminosity Functions (LFs) of a subsample of 69 clusters from
the RASS-SDSS galaxy cluster catalog. When calculated within the cluster
physical sizes, given by r200 or r500, all the cluster LFs appear to have the
same shape, well fitted by a composite of two Schechter functions with a marked
upturn and a steepening at the faint-end. Previously reported
cluster-to-cluster variations of the LF faint-end slope are due to the use of a
metric cluster aperture for computing the LF of clusters of different masses.
  We determine the composite LF for early- and late-type galaxies, where the
typing is based on the galaxy u-r colors. The late-type LF is well fitted by a
single Schechter function with a steep slope (alpha=-2.0 in the r band, within
r200}). The early-type LF instead cannot be fitted by a single Schechter
function, and a composite of two Schechter functions is needed. The faint-end
upturn of the global cluster LF is due to the early-type cluster galaxies. The
shape of the bright-end tail of the early-type LF does not seem to depend upon
the local galaxy density or the distance from the cluster center. The late-type
LF shows a significant variation only very near the cluster center. On the
other hand, the faint-end tail of the early-type LF shows a significant and
continuous variation with the environment. We provide evidence that the process
responsible for creating the excess population of dwarf early type galaxies in
clusters is a threshold process that occurs when the density exceeds ~500 times
the critical density of the Universe. We interpret our results in the context
of the 'harassment' scenario, where faint early-type cluster galaxies are
predicted to be the descendants of tidally-stripped late-type galaxies.


title: Rotating Quark Star in Chiral Colour Dielectric Model

abstract:
  The properties of rotating quark star is studied using the equation of state
obtained from Chiral Colour Dielectric model. The results are compared with the
MIT bag model results. The frequencies in the corotating innermost circular
orbits for different central densities are evaluated and compared with the
observational results.


title:
Propagation of Ultra-High Energy Cosmic Rays above $10^{19}$ eV in a
  Structured Extragalactic Magnetic Field and Galactic Magnetic Field

abstract:
  We present numerical simulations on propagation of Ultra-High Energy Cosmic
Rays (UHECRs) above $10^{19}$ eV in a structured extragalactic magnetic field
(EGMF) and simulate their arrival distributions at the earth. We use the IRAS
PSCz catalogue in order to construct a model of the EGMF and source models of
UHECRs, both of which reproduce the local structures observed around the Milky
Way. We also consider modifications of UHECR arrival directions by the galactic
magnetic field. We follow an inverse process of their propagation from the
earth and record the trajectories. This enables us to calculate only
trajectories of UHECRs arriving at the earth, which saves the CPU time. From
these trajectories and our source models, we construct arrival distributions of
UHECRs and calculate the harmonic amplitudes and the two point correlation
functions of them. We estimate number density of sources which reproduces the
Akeno Ground Air Shower Array (AGASA) observation best. As a result, we find
that the most appropriate number density of the sources is $\sim 5 \times
10^{-6}$ Mpc$^{-3}$. This constrains the source candidates of UHECRs. We also
demonstrate skymaps of their arrival distribution with the event number
expected by future experiments and examine how the EGMF affects their arrival
distribution. A main result is diffusion of clustering events which are
obtained from calculations in the absence of the EGMF. This tendency allows us
to reproduce the observed two point correlation function better.


title: The need for small-scale turbulence in atmospheres of substellar objects

abstract:
  Brown dwarfs and giant gas planets are substellar objects whose spectral
appearance is determined by the chemical composition of the gas and the
solids/liquids in the atmosphere. Atmospheres of substellar objects possess two
major scale regimes: large-scale convective motions + gravitational settling
and small-scale turbulence + dust formation. Turbulence initiates dust
formation spot-like on small scale, while the dust feeds back into the
turbulent fluid field by its strong radiative cooling. Small, imploding dust
containing areas result which eventually become isothermal. Multi-dimensional
simulations show that these small-scale dust structures gather into large-scale
structures, suggesting the formation of clouds made of dirty dust grains. The
chemical composition of the grains, and thereby the chemical evolution of the
gas phase, is a function of temperature and depends on the grain's history.


title: Near Infrared Imaging Survey of Bok Globules: Density Structure

abstract:
  On the basis of near-infrared imaging observations, we derived visual
extinction (Av) distribution toward ten Bok globules through measurements of
both the color excess (E_{H-K}) and the stellar density at J, H, and Ks (star
count). Radial column density profiles for each globule were analyzed with the
Bonnor-Ebert sphere model. Using the data of our ten globules and four globules
in the literature, we investigated the stability of globules on the basis of
xi_max, which characterizes the Bonnor-Ebert sphere as well as the stability of
the equilibrium state against the gravitational collapse. We found that more
than half of starless globules are located near the critical state (xi_max =
6.5 +/- 2). Thus, we suggest that a nearly critical Bonnor-Ebert sphere
characterizes the typical density structure of starless globules. Remaining
starless globules show clearly unstable states (xi_max > 10). Since unstable
equilibrium states are not long maintained, we expect that these globules are
on the way to gravitational collapse or that they are stabilized by non-thermal
support. It was also found that all the star-forming globules show unstable
solutions of xi_max >10, which is consistent with the fact that they have
started gravitational collapse. We investigated the evolution of a collapsing
gas sphere whose initial condition is a nearly critical Bonnor-Ebert sphere. We
found that the column density profiles of the collapsing sphere mimic those of
the static Bonnor-Ebert spheres in unstable equilibrium. The collapsing gas
sphere resembles marginally unstable Bonnor-Ebert spheres for a long time. We
found that the frequency distribution of xi_max for the observed starless
globules is consistent with that from model calculations of the collapsing
sphere.


title:
The metal abundance distribution of the oldest stellar component in the
  Sculptor dwarf spheroidal galaxy

abstract:
  (abridged): Low resolution spectroscopy obtained with FORS2 at the Very Large
Telescope (VLT) has been used to measure individual metal abundances ([Fe/H])
for 107 RR Lyrae stars, and trace the metal distribution of the oldest stellar
component in the Sculptor dwarf spheroidal galaxy. Their metallicities have an
average value of [Fe/H]=-1.83 +/- 0.03 (r.m.s. 0.26 dex) and cover the
metallicity range -2.40<[Fe/H]<-0.85 (only 1 star with [Fe/H]>-1). The
star-to-star scatter is larger than typical errors on individual metallicities
(+/- 0.15-0.16 dex), indicating a real spread in metal abundances. The radial
velocities have a dispersion of 12.9 km/s, consistent with the dispersion
derived in Sculptor by Tolstoy et al. (2004). This along with the metallicity
distribution, suggests that most of the RR Lyr's arise from the same burst of
stellar formation that produced the metal-poor component giving origin to the
galaxy blue horizontal branch, and only a few (if any) come from the centrally
concentrated metal-rich red horizontal branch population. The spectroscopic
metallicities and the apparent luminosities were used to study the
luminosity-metallicity relation, for which we derive a shallow slope of 0.09
mag/dex. This result can be due to a high level of evolution off the zero age
horizontal branch of the RR Lyrae stars in this galaxy, again in agreement with
their origin from the blue horizontal branch population.


title: Cepheid pulsation models at varying metallicity and DY/DZ

abstract:
  In this paper we present an extended set of nonlinear convective pulsation
models at varying the metallicity and DY/DZ ratio. The predicted instability
strip and bolometric light curves are discussed by comparing the new models
with our previous ones. In particular, the dependence on both metal and helium
abundances is investigated. By transforming the bolometric light curves into
the observational bands we are able to derive both Period-Color-Luminosity and
Wesenheit relations for each selected chemical composition. Synthetic
Period-Luminosity relations are obtained by populating the instability strip
according to specific assumptions on the number of pulsators and the mass
distribution. These theoretical results are compared with recent accurate data
by Sandage et al. and Kervella et al., in order to test the predictive
capabilities of the models. We confirm our previous results that the
theoretical metallicity correction to the Key Project Cepheid distance scale
depends both on the period range and DY/DZ ratio, becoming important for
periods longer than 20 days and DY/DZ > 1.5.


title:
Spiral Structure when Setting up Pericentre Glow: Possible Giant Planets
  at Hundreds of AU in the HD141569 Disk

abstract:
  This paper discusses the impact of introducing a planet on an eccentric orbit
into a planetesimal disk. That planet's secular perturbations cause the orbits
of the planetesimals to evolve in such a way that at any one time planetesimals
at the same distance from the star have common pericentres and eccentricities.
This causes the surface density distribution of an extended planetesimal disk
to exhibit two spirals, one exterior the other interior to the planet's orbit.
These two spirals unwind in different directions and their structure is
described by two parameters: the time since the planet was introduced and the
planet's eccentricity. At late times the spirals become tightly wound and the
offset centre of symmetry of the pericentre glow approximation is recovered.
Comparison with spiral structure seen in the HD141569 disk shows that its
spiral at 325 AU is similar to that caused by introducing a planet 5 Myr ago
with a mass 0.2-2M_Jup orbiting at 235-250 AU with an eccentricity of 0.05-0.2;
likewise a Saturn mass planet at 150 AU would cause structure like that seen at
200 AU. More definitive statements about any planets orbiting HD141569 from
this model could be made once the effect of the binary companion on the disk is
known, and once the disk's structure has been better characterised down to 100
AU, including the location of the star within the disk. The relatively young
age of this system (~5 Myr) means that if giant planets really do exist at
hundreds of AU from HD141569, this provides a unique opportunity to set
constraints on the mechanism by which those planets came to be at such large
distances.


title:
Multiwavelength Observations of 3C 66A during the WEBT campaign of 2003
  - 2004

abstract:
  The BL Lac object 3C 66A was the target of an extensive multiwavelength
monitoring campaign from July 2003 through April 2004, involving observations
throughout the electromagnetic spectrum. Radio, infrared, and optical
observations were carried out by the WEBT-ENIGMA collaboration. At higher
energies, 3C 66A was observed in X-rays (RXTE), and at very-high-energy (VHE)
gamma-rays (STACEE, VERITAS). In addition, the source has been observed with
the VLBA at 9 epochs throughout the period September 2003 - December 2004,
including 3 epochs contemporaneous with the core campaign.The WEBT campaign
revealed microvariability with flux changes of ~ 5 % on time scales as short as
\~ 2 hr. The source was in a relatively bright state, with several bright
flares on time scales of several days. The SED indicates a $\nu F_{\nu}$ peak
in the optical regime. A weak trend of optical spectral hysteresis with a trend
of spectral softening throughout both the rising and decaying phases, has been
found. The 3 - 10 keV X-ray flux of 3C 66A during the core campaign was
historically high and its spectrum very soft, indicating that the low-frequency
component of the broadband SED extends beyond ~ 10 keV. No significant X-ray
flux and/or spectral variability was detected. STACEE and Whipple observations
provided upper flux limits at > 150 GeV and > 390 GeV, respectively. The 22 and
43 GHz data from the 3 VLBA epochs between September 2003 and January 2004
indicate a smooth jet with only moderate internal structure. Evidence for
superluminal motion (8.5 +/- 5.6 h^{-1} c) was found in only one out of 6
components. The radial radio brightness profile suggests a magnetic field decay
$\propto r^{-1}$ and, thus, a predominantly perpendicular magnetic field.


title:
Elemental Abundance Ratios in Stars of the Outer Galactic Disk. II.
  Field Red Giants

abstract:
  We summarize a selection process to identify red giants in the direction of
the southern warp of the Galactic disk, employing VI_C photometry and
multi-object spectroscopy. We also present results from follow-up
high-resolution, high-S/N echelle spectroscopy of three field red giants,
finding [Fe/H] values of about -0.5. The field stars, with Galactocentric
distances estimated at 10 to 15 kpc, support the conclusion of Yong, Carney, &
de Almeida (2005) that the Galactic metallicity gradient disappears beyond R_GC
values of 10 to 12 kpc for the older stars and clusters of the outer disk. The
field and cluster stars at such large distances show very similar abundance
patterns, and, in particular, all show enhancements of the "alpha" elements O,
Mg, Si, Ca, and Ti and the r-process element Eu. These results suggest that
Type II supernovae have been significant contributors to star formation in the
outer disk relative to Type Ia supernovae within the past few Gyrs. We also
compare our results with those available for much younger objects. The limited
results for the H II regions and B stars in the outer disk also suggest that
the radial metallicity gradient in the outer disk is shallow or absent. The
much more extensive results for Cepheids confirm these trends, and that the
change in slope of the metallicity gradient may occur at a larger
Galactocentric distance than for the older stars and clusters. However, the
younger stars also show rising alpha element enhancements with increasing R_GC,
at least beyond 12 kpc. These trends are consistent with the idea of a
progressive growth in the size of the Galactic disk with time, and episodic
enrichment by Type II supernovae as part of the disk's growth. [Abridged]


title: Internal dynamics of the z sim 0.8 cluster RX J0152.7-1357

abstract:
  We present the results from the dynamical analysis of the cluster of galaxies
RX J0152-1357, which shows a complex structure in its X-ray emission, with two
major clumps in the central region, and a third clump in the Eastern region.
Our analysis is based on redshift data for 187 galaxies. We compute the
line-of-sight velocity dispersion of galaxies, sigma_V=1322^+74_-68 kms^-1,
which is significantly larger than what is expected in the case of a relaxed
cluster with an observed X-ray temperature of 5-6 keV. We find evidence that
this cluster is far from dynamical equilibrium, as shown by the non Gaussianity
of the velocity distribution, the presence of a velocity gradient and
significant substructure. Our analysis shows that the high value of sigma_V is
due to the complex structure of RX J0152-1357, i.e. to the presence of three
galaxy clumps of different mean velocity. Using optical data we detect a
low-velocity clump (with sigma_V=300-500 kms^-1) in the central SW region and a
high--velocity clump (with sigma_V sim 700 kms^-1) in the E region, well
corresponding to the SW and E peaks detected in the X-ray emission. The central
NE X-ray peak is associated to the main galaxy structure with a velocity which
is intermediate between those of the other two clumps and sigma_V sim 900
kms^-1. The mass of the whole system within 2 Mpc is estimated to lie in the
range (1.2-2.2)X10^{15} M_sun. Analytic calculations based on the two-body
model indicate that the system is most likely bound, currently undergoing
merging. In particular, we suggest that the SW clump is not a small group, but
rather the dense cluster-core of a massive cluster.


title:
An Efficient Numerical Scheme for Simulating Particle Acceleration in
  Evolving Cosmic-Ray Modified Shocks

abstract:
  We have developed a new, very efficient numerical scheme to solve the CR
diffusion convection equation that can be applied to the study of the nonlinear
time evolution of CR modified shocks for arbitrary spatial diffusion
properties. The efficiency of the scheme derives from its use of coarse-grained
finite momentum volumes. This approach has enabled us, using $\sim 10 - 20$
momentum bins spanning nine orders of magnitude in momentum, to carry out
simulations that agree well with results from simulations of modified shocks
carried out with our conventional finite difference scheme requiring more than
an order of magnitude more momentum points. The coarse-grained, CGMV scheme
reduces execution times by a factor approximately half the ratio of momentum
bins used in the two methods. Depending on the momentum dependence of the
diffusion, additional economies in required spatial and time resolution can be
utilized in the CGMV scheme, as well. These allow a computational speed-up of
at least an order of magnitude in some cases.


title: The Formation Histories of Galaxy Clusters

abstract:
  A sample of hundreds of simulated galaxy clusters is used to study the
statistical properties of galaxy cluster formation. Individual assembly
histories are discussed, the degree of virialization is demonstrated and
various commonly used formation times are measured and inter-compared. In
addition, the fraction of clusters which have ``recently'' undergone a major
merger or significant mass jump is calculated as a function of lookback time
and interval. The fraction of three- and four-body mergers is also studied.


title:
Metallicity Effects on Mid-Infrared Colors and the 8 micron PAH Emission
  in Galaxies

abstract:
  We examine colors from 3.6 micron to 24 micron as a function of metallicity
(O/H) for a sample of 34 galaxies. The galaxies range over 2 orders of
magnitude in metallicity. They display an abrupt shift in the 8 micron to 24
micron color between metallicities 1/3 to 1/5 of the solar value. The mean 8
micron to 24 micron flux density ratio below and above 12 + log (O/H) = 8.2 is
0.08 +/- 0.04 and 0.70 +/- 0.53, respectively. We use mid-infrared colors and
spectroscopy to demonstrate that the shift is primarily due to a decrease in
the 8 micron flux density as opposed to an increase in the 24 micron flux
density. This result is most simply interpreted as due to a weakening at low
metallicity of the mid-infrared emission bands usually attributed to PAHs
(polycyclic aromatic hydrocarbons) relative to the small-grain dust emission.
However, existing empirical spectral energy distribution models cannot account
for the observed short-wavelength (i.e., below 8 micron) colors of the
low-metallicity galaxies merely by reducing the strength of the PAH features;
some other emission source (e.g., hot dust) is required.


title:
The Birthplace of Low-Mass X-ray Binaries: Field Versus Globular Cluster
  Populations

abstract:
  Recent Chandra studies of low-mass X-ray binaries (LMXBs) within early-type
galaxies have found that LMXBs are commonly located within globular clusters of
the galaxies. However, whether all LMXBs are formed within globular clusters
has remained an open question. If all LMXBs formed within globular clusters,
the summed X-ray luminosity of the LMXBs in a galaxy should be directly
proportional to the number of globular clusters in the galaxy regardless of
where the LMXBs currently reside. We have compared these two quantities over
the same angular area for a sample of 12 elliptical and S0 galaxies observed
with Chandra and found that the correlation between the two quantities is
weaker than expected if all LMXBs formed within globular clusters. This
indicates that a significant number of the LMXBs were formed in the field, and
naturally accounts for the spread in field-to-cluster fractions of LMXBs from
galaxy to galaxy. We also find that the "pollution" of globular cluster LMXBs
into the field has been minimal within elliptical galaxies, but there is
evidence that roughly half of the LMXBs originally in the globular clusters of
S0 galaxies in our sample have escaped into the field. This is due to higher
globular cluster disruption rates in S0s resulting from stronger gravitational
shocks caused by the passage of globular clusters through the disks of S0
galaxies that are absent in elliptical galaxies.


title:
The effect of MHD turbulence on massive protoplanetary disk
  fragmentation

abstract:
  Massive disk fragmentation has been suggested to be one of the mechanisms
leading to the formation of giant planets. While it has been heavily studied in
quiescent hydrodynamic disks, the effect of MHD turbulence arising from the
magnetorotational instability (MRI) has never been investigated. This paper
fills this gap and presents 3D numerical simulations of the evolution of
locally isothermal, massive and magnetized disks. In the absence of magnetic
fields, a laminar disk fragments and clumps are formed due to the effect of
self--gravity. Although they disapear in less than a dynamical timescale in the
simulations because of the limited numerical resolution, various diagnostics
suggest that they should survive and form giant planets in real disks. When the
disk is magnetized, it becomes turbulent at the same time as gravitational
instabilities develop. At intermediate resolution, no fragmentation is observed
in these turbulent models, while a large number of fragments appear in the
equivalent hydrodynamical runs. This is because MHD turbulence reduces the
strength of the gravitational instability. As the resolution is increased, the
most unstable wavelengths of the MRI are better resolved and small scale
angular momentum transport starts to play a role: fragments are found to form
in massive and turbulent disks in that case. All of these results indicate that
there is a complicated interaction between gravitational instabilities and MHD
turbulence that influences disk fragmentation processes.


title: Einstein-de Sitter model re-examined for the newly discovered SNe Ia

abstract:
  Consistency of Einstein-de Sitter model with the recently observed SNe Ia by
the Hubble Space Telescope is examined. The model shows a reasonable fit to the
observation, if one takes into account the extinction of SNe light by the
intergalactic metallic dust ejected from the SNe explosions. Though the fit to
the new data is worsened considerably compared with the earlier data, it can
still be regarded acceptable. We should wait for more accurate observations at
higher redshifts (as expected from the coming space missions such as SNAP and
JWST) in order to rule out a model, which seems to explain all the other
existing observations well (some even better than the favoured $\Lambda$CDM
model), is consistent with beautiful theoretical ideas like inflation and cold
dark matter, and is not as speculative as the models of dark energy.


title: On the stellar luminosity of the universe

abstract:
  It has been noted at times that the rate of energy release in the most
violent explosive events in the Universe, such as supernovae and gamma-ray
bursts, rivals the stellar luminosity of the observable universe, Lstar. The
underlying reason turns out to be that both can be scaled to c^5/G = Lgrav,
albeit that for the explosions Lstar/Lgrav follows from first principles,
whereas for Lstar the scaling involves quantities too complex to derive from
elementary considerations at the present time. Under fairly general
circumstances, Lstar is dominated by stars whose age is similar to the Hubble
time.


title: High-energetic Cosmic Antiprotons from Kaluza-Klein Dark Matter

abstract:
  The lightest Kaluza-Klein particle (LKP) in models with universal extra
dimensions is an interesting dark matter candidate that has recently received
great attention. Here, we investigate the antiproton flux from LKP
annihilations in the galactic halo. In our analysis we include different halo
density profiles and allow for part of the dark matter to be concentrated in
'clumps' rather than being distributed homogeneously. After re-analyzing the
observational bounds on the allowed amount of clumpiness, we find that LKP
annihilations may well give a significant contribution to the antiproton flux
at energies higher than about 10 GeV, while for energies above around 500 GeV
the conventional background is expected to dominate again. The shortly upcoming
PAMELA satellite will already be able to measure part of this high-energy
window, while planned experiments like AMS-02 will have access to the full
energy range of interest.


title:
Generation of Mesoscale Magnetic Fields and the Dynamics of Cosmic Ray
  Acceleration

abstract:
  The problem of the cosmic ray origin is discussed in connection with their
acceleration in supernova remnant shocks. The diffusive shock acceleration
mechanism is reviewed and its potential to accelerate particles to the maximum
energy of (presumably) galactic cosmic rays ($10^{18}eV $) is considered. It is
argued that to reach such energies, a strong magnetic field at scales larger
than the particle gyroradius must be created as a result of the acceleration
process, itself. One specific mechanism suggested here is based on the
generation of Alfven wave at the gyroradius scale with a subsequent transfer to
longer scales via interaction with strong acoustic turbulence in the shock
precursor. The acoustic turbulence in turn, may be generated by Drury
instability or by parametric instability of the Alfven waves.


title:
Cosmological Implications of the Uncertainty in H- Destruction Rate
  Coefficients

abstract:
  In primordial gas, molecular hydrogen forms primarily through associative
detachment of H- and H, thereby destroying the H-. The H- anion can also be
destroyed by a number of other reactions, most notably by mutual neutralization
with protons. However, neither the associative detachment nor the mutual
neutralization rate coefficients are well determined: both may be uncertain by
as much as an order of magnitude. This introduces a corresponding uncertainty
into the H2 formation rate, which may have cosmological implications. Here, we
examine the effect that these uncertainties have on the formation of H2 and the
cooling of protogalactic gas in a variety of situations. We show that the
effect is particularly large for protogalaxies forming in previously ionized
regions, affecting our predictions of whether or not a given protogalaxy can
cool and condense within a Hubble time, and altering the strength of the
ultraviolet background that is required to prevent collapse.


title: Phantom damping of matter perturbations

abstract:
  Cosmological scaling solutions are particularly important in solving the
coincidence problem of dark energy. We derive the equations of sub-Hubble
linear matter perturbations for a general scalar-field Lagrangian--including
quintessence, tachyon, dilatonic ghost condensate and k-essence--and solve them
analytically for scaling solutions. We find that matter perturbations are
always damped if a phantom field is coupled to dark matter and identify the
cases in which the gravitational potential is constant. This provides an
interesting possibility to place stringent observational constraints on scaling
dark energy models.


title:
Evidence for Orbital Motion of Material Close to the Central Black Hole
  of Mrk 766

abstract:
  Time-resolved X-ray spectroscopy has been obtained for the narrow line
Seyfert galaxy Mrk766 from XMM-Newton observations. We present analysis in the
energy-time plane of EPIC pn data in the 4-8 keV band with energy resolution
R~50. A component of Fe Ka emission detected in the maps shows a variation of
photon energy with time that appears both to be statistically significant and
to be consistent with sinusoidal variation. We investigate the interpretation
that there exists a component of line emission from matter in a Keplerian orbit
around a supermassive black hole. The orbit has a period ~165 ks and a
line-of-sight velocity ~13,500 km/s. This yields a lower limit for the central
mass of M > 4.9x10^5 solar masses within a radius of 3.6 x 10^13 cm (2.4 A.U.).
The orbit parameters are consistent with higher black hole masses, but the lack
of any substantial gravitational redshift of the orbit implies an upper limit
to the black hole mass of 4.5x10^7 solar masses.


title:
A Neutral Hydrogen Survey of the Large Magellanic Cloud: Aperture
  Synthesis and Multibeam Data Combined

abstract:
  Using a Fourier-plane technique, we have merged HI ATCA and Parkes data sets
providing an accurate set of images of the LMC sensitive to structure on scales
of 15 pc (for an LMC distance of 55 kpc) upwards. The spatial dynamic range
(2.8 orders of magnitude), velocity resolution (1.649 km/s), brightness
temperature sensitivity (2.4 K) and column density sensitivity ($8.9 \times 10^
{18}$ cm$^{-2}$ per 1.649 km/s channel) allow for the studies of phenomena
ranging from the galaxy-wide interaction of the LMC with its close neighbours
to the small-scale injection of energy from supernovae and stellar associations
into the ISM of the LMC. We find that a previous analysis of the holes and
shells (Kim et al. 1999) in the HI distribution shows the same power- law
behavior with that of clumps. The measured perimeter P and measured enclosed
area A of each HI cloud in a log-log plot give us a set of points lying along
with a slope of D/2 = 0.73 $\pm$ 0.1. The relation between area and perimeter
of each identified HI cloud, P $\propto$ $A^{D/2}$, can determine the fractal
dimension D=1.47 $\pm$ 0.2 of a cloud boundary (Vogelaar & Wakker 1994;
Williams, Blitz, & McKee 2000). The measured fractal dimension of HI clouds in
the LMC is similar to the dimension, D=1.4, found in many studies of the
molecular ISM.


title: The Masses of the Orion Proplyds from Submillimeter Dust Emission

abstract:
  We have imaged the 880 micron continuum emission from the "proplyds" in the
center of the Trapezium Cluster in Orion using the Submillimeter Array with a
beam size 1.5'' FWHM and an rms of 2.7 mJy. Five sources are detected with
fluxes in the range 18 to 38 mJy, which includes dust emission from four
proplyds and ionized gas from theta1 Ori G. The total masses of the detected
proplyds derived from their dust emission range from 0.013 to 0.024 Msun
assuming a dust temperature of 20 K and mass opacity of 0.03 cm^2/g. The
eighteen other proplyds within the field-of-view were not formally detected
individually, but by combining the fluxes measured at their locations, an
average flux of 1.1mJy was determined for them on a statistical basis,
corresponding to a mass of 8e-4 Msun. The four detected proplyds have
sufficient disk mass bound to their central stars to form planetary systems on
the scale of our Solar System.


title: Discovery of a massive SCUBA core with both inflow and outflow motions

abstract:
  We report the discovery of a massive SCUBA core with evidence of inflow and
outflow motions. This core is detected by SCUBA at both 450 and 850 micro
meter. Barely resolved by the telescope beam at 450 micro meter, it has a size
of 10 arcsec, corresponding to 0.28 pc at a distance of 5.7 kpc. The dust
temperature is estimated to be less than 29 K, the total mass is 820 solar mass
and the average density is 1.1e-6 per cube-cm in a region with a radius of 5
arcsec. Follow-up spectral line observations, including HCN (3-2), HCO+ (3-2),
H13CO+ (3-2) and C17O (2-1) reveal a typical blue profile which indicates that
this core is collapsing. The CO (3-2) line profile is as broad as 38 km/s,
indicating outflow motions in this region. This core is approximately 1.5 pc
away from the known HII region G25.4NW, but there are no obvious radio, IRAS,
MSX or Spitzer sources associated with it. We suggest that this core is at a
very early stage of massive star or cluster formation.


title:
X-ray Spectral Evolution of Her X-1 in a Low State and the Following
  Short High State

abstract:
  We analyzed spectral variations of $\sim 8.5$ days long RXTE monitoring
observations of Her X-1 in December 2001. This set of observations enables, for
the first time, frequent continuous monitoring (111 pointings in $\sim 8.5$
days) of the source with RXTE including $\sim 1.7$ days long low state part and
the following $\sim 6.8$ days long short high state part. We used absorbed
power law model with iron line energy complex modeled as a Gaussian to fit both
the 3-60 keV PCA-HEXTE overall short high state spectrum and 3-20 keV
individual PCA spectra. Additional partial cold absorber model was used for
both cases. Using 3-20 keV individual PCA spectra, absorption in anomalous dips
and preeclipse dips in short high state were compared. Decreasing ratio of
unabsorbed flux to absorbed flux with increasing unabsorbed flux in anomalous
and preeclipse dips was interpreted as an evidence of the fact that the regions
causing opaque obscuration and soft absorption are not geometrically far away
from each other. Higher iron line peak energies in low state and short high
state ($\sim 6.6-6.9$ keV) were interpreted as a clue of the presence of iron
line components other than K$\alpha$ emission line.


title: Two new ZZ Ceti pulsators from the HS and HE surveys

abstract:
  We report the detection of nonradial g-mode oscillations in the DA white
dwarfs HS1039+4112 (B=15.9) and HE1429-0343 (B=15.8) from time-series
photometry made at the Loiano 1.5 m telescope. The two stars were previously
selected as probable pulsators based on two-color photometry and spectral
analysis respectively. Following our temperature and surface gravity
determinations, HS1039+4112 (Teff=11200 K, logg=8.2) is located near the red
edge of the ZZ Ceti instability strip, whereas HE1429-0343 (Teff=11400 K,
logg=7.8) falls in the middle of the strip. Both stars show a multi-mode
behavior with the main periods at about 850 and 970 s respectively, and
relatively large amplitudes (~7% and ~2.5%).


title: Slingshot prominences above stellar X-ray coronae

abstract:
  We present a new model for the coronal structure of rapidly rotating
solar-type stars. The presence of prominences trapped in co-rotation 2 to 5
stellar radii above the stellar surface has been taken as evidence that the
coronae of these stars must be very extended. The observed surface magnetic
fields, however, cannot contain X-ray emitting gas out to these distances. We
present an alternative model: that these prominences are trapped in long thin
loops embedded not in the X-ray corona, but in the wind. Above coronal helmet
streamers, oppositely-directed wind-bearing field lines reconnect to form
closed loops which then fill up with gas that was originally part of the wind.
We demonstrate that static equilibria exist for these loops at a range of
pressures and temperatures. The maximum loop height falls as the rotation rate
increases, but rises as the loop temperature decreases. For a solar-mass star
with rotation period 0.5 days, whose X-ray corona extends 1stellar radius above
the surface, loops at temperatures of 10, 000 K can extend out to 5 stellar
radii.


title:
Long-term optical/IR variability of the Be/X-ray binary LS V +44 17/RX
  J0440.9+4431

abstract:
  We present the first long-term study of the optical counterpart to the X-ray
pulsar LS V +44 17/RX J0440.9+4431. The results of our photometric and
spectroscopic analysis show that LS V +44 17/RX J0440.9+4431 contains a
moderately reddened, E(B-V)=0.65+-0.05, B0.2V star located at about 3.3 kpc.
The Ha line consistently shows a double-peak profile varying from symmetric
shape to completely distorted on one side (V/R phases). A correlation between
the equivalent width of the Ha line and the infrared magnitudes is seen: as the
EW(Ha) decreases the IR magnitudes become fainter. This long-term optical/IR
variability is attributed to structural changes in the Be star's circumstellar
disc. The observations include a recent decline in the circumstellar disc and
subsequent recovery. We have witnessed the cessation of a global oscillation
due to the decline of the circumstellar disc. If the present disc growth rate
continues we predict the onset of another episode of V/R variability by the end
of 2006. We have investigated the typical time scales for disc variability of
various Be/X-ray binaries and found a correlation with the orbital period. This
correlation is hard to establish due to the difficulty in defining the exact
duration of the various activity states, but it is seen both in the duration of
the disc growth/dissipation phase and the value of the Ha equivalent width
prior to the appearance of asymmetric profiles. These relationships provide
further evidence for the interaction of the neutron star with the circumstellar
disc of the Be star's companion and confirms the need of a fully developed disc
for the V/R variability to be observed.


title:
Binaries discovered by the SPY project. IV. Five single-lined DA double
  white dwarfs

abstract:
  We present results from our ongoing follow-up observations of double white
dwarf binaries detected in the ESO SN Ia Progenitor SurveY
  (SPY). We discuss our observing strategy and data analysis and present the
orbital solutions of five close double white dwarf binaries: HE0320-1917,
HE1511-0448, WD0326-273, WD1013-010 and WD1210+140. Their periods range from
0.44 to 3.22 days. In none of these systems we find any spectral lines
originating from the companion. This rules out main sequence companions and
indicates that the companion white dwarfs are significantly older and cooler
than the bright component. Infrared photometry suggests the presence of a cool,
helium-rich white dwarf companion in the binary
  WD0326-273. We briefly discuss the consequences of our findings for our
understanding of the formation and evolution of double white dwarfs.


title:
Optical Afterglow Observations of the Unusual Short-Duration Gamma-Ray
  Burst 040924

abstract:
  The 1-m telescope at Lulin Observatory and the 0.76-m Katzman Automatic
Imaging Telescope at Lick Observatory were used to observe the optical
afterglow of the short-duration (1.2--1.5 s) gamma-ray burst (GRB) 040924. This
object has a soft high-energy spectrum, thus making it an exceptional case,
perhaps actually belonging to the short-duration tail of the long-duration
GRBs. Our data, combined with other reported measurements, show that the early
R-band light curve can be described by two power laws with index alpha = -0.7
(at t = 16-50 min) and alpha = -1.06 (at later times). The rather small
difference in the spectral indices can be more easily explained by an afterglow
model invoking a cooling break rather than a jet break.


title: GRB follow-up observations in the East-Asian region

abstract:
  In 2004, we established a Japan-Taiwan-China collaboration for GRB study in
the East-Asian region. This serves as a valuable addition to the world-wide
optical and infrared follow-up network, because the East-Asia region would
otherwise be blank. We have been carrying out imaging and spectroscopic
follow-up observations at Lulin (Taiwan), Kiso (Japan), WIDGET (Japan) and
Xinglong (China). From Xinglong and Kiso, we can locate candidates and obtain
early time spectra for afterglows. While WIDGET provides early time
observations before the burst, the high-time resolution for multi-band light
curves can be obtained at Lulin. With the data from these sites, we can obtain
detailed information about the light curve and redshift of GRBs, which are
important to understand the mechanism of the afterglows. Up to March 2005, ten
follow-up observations have been provided by this East-Asia cooperation. Two
optical afterglows were detected, GRB 040924 and GRB 041006. The results of the
two detected afterglows are reported in this article.