title: The Status of VHE Gamma-Ray Astronomy

abstract:
  This paper presents a summary of the status of the field of very high-energy
(VHE) gamma-ray astronomy, as of early 2006. The paper is based on the
Rapporteur Talk given at the 29th International Cosmic Ray Conference in Pune,
India (ICRC 2005). It covers astrophysical results from observations made by
high-energy and very high-energy telescopes operating at photon energies above
1 GeV. The majority of recent observations in this field have been made by
ground-based telescopes using the atmospheric Cherenkov or air shower
techniques.


title:
Photometric monitoring of the ROSAT selected weak-line T Tauri stars in
  the Taurus-Auriga field

abstract:
  We monitored the light variations of 22 weak-line T Tauri stars (WTTS)
discovered among the X-ray sources in the field of the Taurus-Auriga cloud. The
photometric variability of 12 out of these WTTS samples is confirmed. They are
all proved to be in periodic variations. By using the methods of the Phase
Dispersion Minimization (PDM) and Fourier analysis, the rotational periods of
these stars were determined based on this observation. Most of them are found
to be shorter than one day. This gives further evidences for the spin up of
solar-type stars as predicted by models of angular momentum evolution of
pre-main sequence stars.


title:
Dust Destruction in the High-Velocity Shocks Driven by Supernovae in the
  Early Universe

abstract:
  We investigate the destruction of dust grains by sputtering in the
high-velocity interstellar shocks driven by supernovae (SNe) in the early
universe to reveal the dependence of the time-scale of dust destruction on the
gas density $n_{{\rm H}, 0}$ in the interstellar medium (ISM) as well as on the
progenitor mass $M_{\rm pr}$ and explosion energy $E_{\rm 51}$ of SN. The
sputtering yields for the combinations of dust and ion species of interest to
us are evaluated by applying the so-called universal relation with a slight
modification. The dynamics of dust grains and their destruction by sputtering
in shock are calculated by taking into account the size distribution of each
dust species, together with the time evolution of temperature and density of
gas in spherically symmetric shocks. The results of calculations show that the
efficiency of dust destruction depends not only on the sputtering yield but
also on the initial size distribution of each grain species. The efficiency of
dust destruction increases with increasing $E_{\rm 51}$ and/or increasing
$n_{{\rm H}, 0}$, but is almost independent of $M_{\rm pr}$ as long as $E_{\rm
51}$ is the same. The mass of gas swept up by shock is the increasing function
of $E_{\rm 51}$ and the decreasing function of $n_{{\rm H}, 0}$. Combining
these results, we present the approximation formula for the time-scale of
destruction for each grain species in the early universe as a function of
$E_{\rm 51}$ and $n_{{\rm H}, 0}$. This formula is applicable for investigating
the evolution of dust grains at the early epoch of the universe with the
metallicity of $Z \la 10^{-3}$ $Z_\odot$. The effects of the cooling processes
of gas on the destruction of dust are briefly discussed.


title:
Two evolutional paths of an axisymmetric gravitational instability in
  the dust layer of a protoplanetary disk

abstract:
  Nonlinear numerical simulations are performed to investigate the density
evolution in the dust layer of a protoplanetary disk due to the gravitational
instability and dust settling toward the midplane. We assume the region where
the radial pressure gradient at equilibrium is negligible so that the
shear-induced instability is avoided, and also restrict to an axisymmetric
perturbation as a first step of nonlinear numerical simulations of the
gravitational instability. We find that there are two different evolutional
paths of the gravitational instability depending on the nondimensional gas
friction time, which is defined as the product of the gas friction time and the
Keplerian angular velocity. If the nondimensional gas friction time is equal to
0.01, the gravitational instability grows faster than dust settling. On the
other hand, if the nondimensional gas friction time is equal to 0.1, dust
aggregates settle sufficiently before the gravitational instability grows. In
the latter case, an approximate analytical calculation reveals that dust
settling is faster than the growth of the gravitational instability regardless
of the dust density at the midplane. Thus, the dust layer becomes extremely
thin and may reach a few tenth of the material density of the dust before the
gravitational instability grows.


title:
The Possibility of Cosmic Acceleration via Spatial Averaging in
  Lemaitre-Tolman-Bondi Models

abstract:
  We investigate the possible occurrence of a positive cosmic acceleration in a
spatially averaged, expanding, unbound Lemaitre-Tolman-Bondi cosmology. By
studying an approximation in which the contribution of three-curvature
dominates over the matter density, we construct numerical models which exhibit
acceleration.


title: The periodic variations of a white-light flare observed with ULTRACAM

abstract:
  High time resolution observations of a white--light flare on the active star
EQ PegB show evidence of intensity variations with a period of approximately 10
s. The period drifts to longer values during the decay phase of the flare. If
the oscillation is interpreted as an impulsively--excited, standing--acoustic
wave in a flare loop, the period implies a loop length of 1.7 Mm and 3.4 Mm for
the case of the fundamental mode and the second harmonic, respectively.
However, the small loop lengths imply a very high modulation depth making the
acoustic interpretation unlikely. A more realistic interpretation may be that
of a fast--MHD wave, with the modulation of the emission being due to the
magnetic field. Alternatively, the variations could be due to a series of
reconnection events. The periodic signature may then arise as a result of the
lateral separation of individual flare loops or current sheets with oscillatory
dynamics (i.e. periodic reconnection).


title:
Modelling the components of binaries in Hyades: The dependence of the
  mixing-length parameter on stellar mass

abstract:
  We present our findings based on a detailed analysis for the binaries of the
Hyades, in which the masses of the components are well known. We fit the models
of components of a binary system to the observations so as to give the observed
total V and B-V of that system and the observed slope of the main-sequence in
the corresponding parts. According to our findings, there is a very definite
relationship between the mixing-length parameter and the stellar mass. The
fitting formula for this relationship can be given as $alpha = 9.19
(M/M_sun-0.74)^{0.053}-6.65$, which is valid for stellar masses greater than
0.77 M_sun. While no strict information is gathered for the chemical
composition of the cluster, as a result of degeneracy in the colour-magnitude
diagram, by adopting Z=0.033 and using models for the components of 70 Tau and
theta^2 Tau we find the hydrogen abundance to be X=0.676 and the age to be 670
Myr. If we assume that Z=0.024, then X=0.718 and the age is 720 Myr. Our
findings concerning the mixing length parameter are valid for both sets of the
solution. For both components of the active binary system V818 Tau, the
differences between radii of the models with Z=0.024 and the observed radii are
only about 4 percent. More generally, the effective temperatures of the models
of low mass stars in the binary systems studied are in good agreement with
those determined by spectroscopic methods.


title: Cosmological Acceleration: Dark Energy or Modified Gravity?

abstract:
  We review the evidence for recently accelerating cosmological expansion or
"dark energy", either a negative pressure constituent in General Relativity
(Dark Energy) or modified gravity (Dark Gravity), without any Dark Energy
constituent. If constituent Dark Energy does not exist, so that our universe is
now dominated by pressure-free matter, Einstein gravity must be modified at low
curvature. The vacuum symmetry of any Robertson-Walker universe then
characterizes Dark Gravity as low- or high-curvature modifications of Einstein
gravity. The dynamics of either kind of "dark energy" cannot be derived from
the homogeneous expansion alone, but requires also observing the growth of
inhomogeneities. Present and projected observations are all consistent with a
small fine tuned cosmological constant, with nearly static Dark Energy, or with
gravity modified at cosmological scales. The growth of cosmological
fluctuations will potentially distinguish static "dark energy" from dynamic
"dark energy" with equation of state $w(z)$ either changing rapidly or tracking
the background matter. But to cosmologically distinguish $\Lambda$CDM from
modified gravity will require a weak lensing shear survey more ambitious than
any now projected. Dvali-Gabadadze-Porrati modifications of Einstein gravity
may also be detected in refined bservations in the solar system or at the
intermediate Vainstein scale.
  Dark Energy's epicyclic character, failure to explain the original Cosmic
Coincidence ("Why now?") without fine tuning, inaccessibility to laboratory or
solar system tests, along with braneworld theories, now motivate future
precision solar system, Vainstein-scale and cosmological-scale studies of Dark
Gravity.


title: The X-ray Halo of GX5-1

abstract:
  Using Chandra observations we have measured the energy-resolved
dust-scattered X-ray halo around the low-mass X-ray binary GX5-1, which shows
signs of both singly- and multiply-scattered X-rays. We compared the observed
X-ray halo at various energies to predictions from a range of dust models.
These fits used both smoothly-distributed dust as well as dust in clumped
clouds, with CO and 21 cm observations helping to determine the position of the
clouds along the line of sight. We found that the BARE-GR-B model of Zubko,
Dwek & Arendt (2004 generally led to the best results, although inadequacies in
both the overall model and the data limit our conclusions. We also found that
the composite dust models of Zubko, Dwek & Arendt (2004), especially the ``no
carbon'' models, gave uniformly poor results. Although models using cloud
positions and densities derived naively from CO and 21 cm data gave generally
poor results, plausible adjustments to the distance of the largest cloud and
the mass of a cloud in the expanding 3 kpc Arm lead to significantly improved
fits. We suggest that combining X-ray halo, CO, and 21 cm observations will be
a fruitful method to improve our understanding of both the gas and dust phases
of the interstellar medium.


title:
Low Luminosity Gamma-Ray Bursts as a Unique Population: Luminosity
  Function, Local Rate, and Beaming Factor

abstract:
  Swift/BAT has detected ~ 200 long-duration GRBs, with redshift measurements
for ~50 of them. We derive the luminosity function (Phi^{HL}) and the local
event rate (rho_0^{HL}) of the conventional high luminosity (HL) GRBs by using
the z-known Swift GRBs. Our results are generally consistent with that derived
from the CGRO/BATSE data. However, the fact that Swift detected a low
luminosity (LL) GRB, GRB 060218, at z=0.033 within ~ 2 year of operation,
together with the previous detection of the nearby GRB 980425, suggests a much
higher local rate for these LL-GRBs. We explore the possibility that LL-GRBs as
a distinct GRB population from the HL-GRBs. We find that rho_0^{LL} is
325_{-177}^{+352} Gpc^{-3} yr^{-1}, which is much higher than
rho_0^{HL}(1.12_{-0.20}^{+0.43} Gpc^{-3} yr^{-1}). This rate is ~ 0.7% of the
local Type Ib/c SNe. Our results, together with the finding that less than 10%
of Type Ib/c SNe are associated with off-beam GRBs, suggest that LL-GRBs have a
beaming factor typically less than 14, or a jet angle typically wider than
31^{o}. The high local GRB rate, the small beaming factor, and low luminosity
make the LL-GRBs distinct from the HL-GRBs. Although the current data could not
fully rule out the possibility that both HL- and LL-GRBs are the same
population, our results suggest that LL-GRBs are likely a unique GRB population
and the observed low redshift GRB sample is dominated by the LL-GRBs.


title: Statistics of the drifting subpulse phenomenon

abstract:
  We present the statistical results of a systematic, unbiased search for
subpulse modulation of 187 pulsars performed with the Westerbork Synthesis
Radio Telescope (WSRT) in the Netherlands at an observing wavelength of 21 cm
(Weltevrede et al. 2006). We have increased the list of pulsars that show the
drifting subpulse phenomenon by 42, indicating that more than 55% of the
pulsars show this phenomenon. The large number of new drifters we have found
allows us, for the first time, to do meaningful statistics on the drifting
phenomenon. We find that the drifting phenomenon is correlated with the pulsar
age such that drifting is more likely to occur in older pulsars. Pulsars that
drift more coherently seem to be older and have a lower modulation index.
Contrary claims from older studies, both P3 (the repetition period of the
drifting subpulse pattern) and the drift direction are found to be uncorrelated
with other pulsar parameters.


title:
Post-starburst--AGN Connection: Spatially Resolved Spectroscopy of
  Hdelta-Strong AGNs

abstract:
  Ever since the co-existence of an active galactic nucleus (AGN) and a
starburst was observationally discovered, there has been a significant
controversy over whether there is a physical connection between starbursts and
AGNs. If yes, it is a subject of interest to reveal which one triggers another.
Here we bring a unique insight onto the subject by identifying 840 galaxies
with both a post-starburst signature (strong Balmer absorption lines) and an
AGN (based on the emission line ratio). These poststarburst-AGNs account for
the 4.2% of all the galaxies in a volume-limited sample. The presence of a
post-starburst phase with an active AGN itself is of importance, suggesting
that AGNs may outlive starbursts in the starburst-AGN connection. In addition,
we have performed spatially resolved spectroscopy of three of our
poststarbusrst-AGN galaxies, obtaining some evidence that the post-starburst
region is more extended, but sharply centred around the central AGN, confirming
a spatial connection between the post-starburst and the AGN.


title: Environmental Effects on Galaxy Evolution Based on the SDSS

abstract:
  We have constructed a large, uniform galaxy cluster catalog from the Sloan
Digital Sky Survey data. By studying the morphology--cluster-centric-radius
relation, we have found two characteristic environments where galaxy
morphologies change dramatically, indicating there exist two different physical
mechanisms responsible for the cluster galaxy evolution. We also found an
unusual population of galaxies, which have spiral morphology but do not have
any emission lines, indicating these spiral galaxies do not have any on-going
star formation activity. More interestingly, these passive spiral galaxies
preferentially exist in the cluster outskirts. Therefore, these passive spiral
galaxies are likely to be a key galaxy population being transformed from blue,
star-forming galaxies into red, early-type galaxies.


title:
Breaking Cosmological Degeneracies in Galaxy Cluster Surveys with a
  Physical Model of Cluster Structure

abstract:
  Forthcoming large galaxy cluster surveys will yield tight constraints on
cosmological models. It has been shown that in an idealized survey, containing
> 10,000 clusters, statistical errors on dark energy and other cosmological
parameters will be at the percent level. It has also been shown that through
"self-calibration", parameters describing the mass-observable relation and
cosmology can be simultaneously determined, though at a loss in accuracy by
about an order of magnitude. Here we examine the utility of an alternative
approach of self-calibration, in which a parametrized ab-initio physical model
is used to compute cluster structure and the resulting mass-observable
relations. As an example, we use a modified-entropy ("pre-heating") model of
the intracluster medium, with the history and magnitude of entropy injection as
unknown input parameters. Using a Fisher matrix approach, we evaluate the
expected simultaneous statistical errors on cosmological and cluster model
parameters. We study two types of surveys, in which a comparable number of
clusters are identified either through their X-ray emission or through their
integrated Sunyaev-Zel'dovich (SZ) effect. We find that compared to a
phenomenological parametrization of the mass-observable relation, using our
physical model yields significantly tighter constraints in both surveys, and
offers substantially improved synergy when the two surveys are combined. These
results suggest that parametrized physical models of cluster structure will be
useful when extracting cosmological constraints from SZ and X-ray cluster
surveys. (abridged)


title: Inflation, dark matter and dark energy in the string landscape

abstract:
  We consider the conditions needed to unify the description of dark matter,
dark energy and inflation in the context of the string landscape. We find that
incomplete decay of the inflaton field gives the possibility that a single
field is responsible for all three phenomena. By contrast, unifying dark matter
and dark energy into a single field, separate from the inflaton, appears rather
difficult.


title: On the geometrical evolution of the ionized gas in HII galaxies

abstract:
  In this paper, we investigate the behaviour of the number of Lyman continuum
ionizing photons as compared to the actual number of hydrogen recombinations in
HII galaxies.
  We evaluate the number of ionizing photons from the population synthesis of
spectra observed in the visible, extrapolating the spectra to the extreme
ultraviolet (EUV), beyond the Lyman limit. We check for possible systematic
deviations of the predicted ionizing spectra in the EUV by comparing the ratio
of the predicted number of ionizing photons to the number of recombinations, as
measured in H$\beta$, ${\rm \Delta \log Q(H^0)}$, with the metallicity.
  We find that, as far as the number of ionizing photons is concerned, no
systematic tendency can be detected. The ${\rm H\beta}$ equivalent width can be
understood as a nebular age indicator, decreasing with age, although the
observed ${\rm H\beta}$ equivalent width can also be affected by the
contribution to the continuum by the accumulation of previous, non-ionizing
stellar populations.
  We attribute the increase of ${\rm \Delta \log Q(H^0)}$ with the age of the
burst to the fact that more and more ionizing photons escape the nebulae when
the nebulae get older, because of their increasing, expansion-induced
subfragmentation.


title: Detecting Extrasolar Planets with Integral Field Spectroscopy

abstract:
  Observations of extrasolar planets using Integral Field Spectroscopy (IFS),
if coupled with an extreme Adaptive Optics system and analyzed with a
Simultaneous Differential Imaging technique (SDI), are a powerful tool to
detect and characterize extrasolar planets directly; they enhance the signal of
the planet and, at the same time, reduces the impact of stellar light and
consequently important noise sources like speckles. In order to verify the
efficiency of such a technique, we developed a simulation code able to test the
capabilities of this IFS-SDI technique for different kinds of planets and
telescopes, modelling the atmospheric and instrumental noise sources. The first
results obtained by the simulations show that many significant extrasolar
planet detections are indeed possible using the present 8m-class telescopes
within a few hours of exposure time. The procedure adopted to simulate IFS
observations is presented here in detail, explaining in particular how we
obtain estimates of the speckle noise, Adaptive Optics corrections, specific
instrumental features, and how we test the efficiency of the SDI technique to
increase the signal-to-noise ratio of the planet detection. The most important
results achieved by simulations of various objects, from 1 M_J to brown dwarfs
of 30 M_J, for observations with an 8 meter telescope, are then presented and
discussed.


title: Gamma-Ray Bursts

abstract:
  Gamma-ray bursts are the most luminous explosions in the Universe, and their
origin and mechanism are the focus of intense research and debate. More than
three decades after their discovery, and after pioneering breakthroughs from
space and ground experiments, their study is entering a new phase with the
recently launched Swift satellite. The interplay between these observations and
theoretical models of the prompt gamma ray burst and its afterglow is reviewed.


title: Globular clusters and galaxy fomation

abstract:
  We first discuss recent progress in using the Milky Way globular cluster (GC)
system as a `test-bed' for properties derived from integrated spectra and
stellar population models. Standard techniques may give rise to spuriously high
alpha-element ratios at low metallicities. We then discuss evidence for early
epoch (z > 2) formation for most GCs in galaxies today. Recent accretions of
GCs (and their host galaxy) make a small contribution but recent mergers form
few if any new GCs in today's elliptical galaxies. The early formation of
metal-poor GCs and the bimodality seen in GC specific frequency requires a
`truncation' which may be due to reionization.


title:
Extremely alpha-Enriched Globular Clusters in Early-Type Galaxies: A
  Step towards the Dawn of Stellar Populations?

abstract:
  We compare [alpha/Fe], metallicity, and age distributions of globular
clusters in elliptical, lenticular, and spiral galaxies, which we derive from
Lick line index measurements. We find a large number of globular clusters in
elliptical galaxies that reach significantly higher [alpha/Fe] values (>0.5)
than any clusters in lenticular and spiral galaxies. Most of these extremely
alpha-enriched globular clusters are old (t > 8 Gyr) and cover the metallicity
range -1 <~ [Z/H] <~ 0. A comparison with supernova yield models suggests that
the progenitor gas clouds of these globular clusters must have been
predominantly enriched by massive stars (>~20 M_sol) with little contribution
from lower-mass stars. The measured [alpha/Fe] ratios are also consistent with
yields of very massive pair-instability supernovae (~130-190 M_sol). Both
scenarios imply that the chemical enrichment of the progenitor gas was
completed on extremely short timescales of the order of a few Myr. Given the
lower [alpha/Fe] average ratios of the diffuse stellar population in early-type
galaxies, our results suggest that these extremely alpha-enhanced globular
clusters could be members of the very first generation of star clusters formed,
and that their formation epochs would predate the formation of the majority of
stars in giant early-type galaxies.


title:
On the sensitivity of HeI singlet lines to the FeIV model atom in O
  stars

abstract:
  Recent calculations and analyses of O star spectra have revealed
discrepancies between theory and observations, and between different
theoretical calculations, for the strength of optical HeI singlet
transitions.We investigate the source of these discrepancies. Using a non-LTE
radiative transfer code we have undertaken detailed test calculations for a
range of O star properties. Our principal test model has parameters similar to
those of the O9V star, 10 Lac. We show that the discrepancies arise from
uncertainties in the radiation field in the HeI resonance transition near
584Angs. The radiation field at 584Angs. is influenced by model assumptions,
such as the treatment of line-blanketing and the adopted turbulent velocity,
and by the FeIV atomic data. It isshown that two FeIV transitions near 584Angs
can have a substantial influence on the strength of the HeI singlet
transitions. Because of the difficulty of modeling the HeI singlet lines,
particularly in stars with solar metalicity, the HeI triplet lines should be
preferred in spectral analyses. These lines are much less sensitive to model
assumptions.


title: Understanding Galaxy Formation and Evolution

abstract:
  The old dream of integrating into one the study of micro and macrocosmos is
now a reality. Cosmology, astrophysics, and particle physics intersect in a
scenario (but still not a theory) of cosmic structure formation and evolution
called Lambda Cold Dark Matter (LCDM) model. This scenario emerged mainly to
explain the origin of galaxies. In these lecture notes, I first present a
review of the main galaxy properties, highlighting the questions that any
theory of galaxy formation should explain. Then, the cosmological framework and
the main aspects of primordial perturbation generation and evolution are
pedagogically detached. Next, I focus on the ``dark side'' of galaxy formation,
presenting a review on LCDM halo assembling and properties, and on the main
candidates for non-baryonic dark matter. It is shown how the nature of
elemental particles can influence on the features of galaxies and their
systems. Finally, the complex processes of baryon dissipation inside the
non-linearly evolving CDM halos, formation of disks and spheroids, and
transformation of gas into stars are briefly described, remarking on the
possibility of a few driving factors and parameters able to explain the main
body of galaxy properties. A summary and a discussion of some of the issues and
open problems of the LCDM paradigm are given in the final part of these notes.


title:
The Faulty Assumptions of the Expanding-Universe Model vs. the Simple
  and Consistent Principles of a Flat-Universe Model -- with Moving Pisa Tower
  Experiment which Tests General Relativity

abstract:
  Mach Principle presents the absolute universe. For example, when Einstein
stood on the ground and relaxed, his arms fell down naturally. However, if he
rotated his body then his arms were lifted up as the rotation was faster and
faster. Mach principle is that the matter of the whole universe can affect
local dynamic systems. That is, the matter of the whole universe sets up the
local absolute reference frames. However, Einstein's general theory of
relativity is against the absolute reference frames of Mach Principle.


title: Constraints on the cosmological density parameters and cosmic topology

abstract:
  A nontrivial topology of the spatial section of the universe is an
observable, which can be probed for all locally homogeneous and isotropic
universes, without any assumption on the cosmological density parameters. We
discuss how one can use this observable to set constraints on the density
parameters of the Universe by using a specific spatial topology along with type
Ia supenovae and X-ray gas mass fraction data sets.


title:
Kinematics of Interstellar Gas in Nearby UV-Selected Galaxies Measured
  with HST/STIS Spectroscopy

abstract:
  We measure Doppler shifts of interstellar absorption lines in HST/STIS
spectra of individual star clusters in nearby UV-selected galaxies. Values for
systemic velocities, which are needed to quantify outflow speeds, are taken
from the literature, and verified with stellar lines. We detect outflowing gas
in eight of 17 galaxies via low-ionization lines (e.g., CII, SiII, AlII), which
trace cold and/or warm gas. The starbursts in our sample are intermediate in
luminosity (and mass) to dwarf galaxies and luminous infrared galaxies (LIRGs),
and we confirm that their outflow speeds (ranging from -100 km/s to nearly -520
km/s with an accuracy of ~80 km/s) are intermediate to those previously
measured in dwarf starbursts and LIRGs. We do not detect the outflow in
high-ionization lines (such as CIV or SiIV); higher quality data will be needed
to empirically establish how velocities vary with the ionization state of the
outflow. We do verify that the low-ionization UV lines and optical NaI doublet
give roughly consistent outflow velocities solidifying an important link
between studies of galactic winds at low and high redshift. To obtain higher
signal-to-noise, we create a local average composite spectrum, and compare it
to the high-z Lyman Break composite spectrum. Surprisingly, the low-ionization
lines show similar outflow velocities in the two samples. We attribute this to
a combination of weighting towards higher luminosities in the local composite,
as well as both samples being on average brighter than the ``turnover''
luminosity in the v-SFR relation.


title: Matching Catalogues by Probabilistic Pattern Classification

abstract:
  We consider the statistical problem of catalogue matching from a machine
learning perspective with the goal of producing probabilistic outputs, and
using all available information. A framework is provided that unifies two
existing approaches to producing probabilistic outputs in the literature, one
based on combining distribution estimates and the other based on combining
probabilistic classifiers. We apply both of these to the problem of matching
the HIPASS radio catalogue with large positional uncertainties to the much
denser SuperCOSMOS catalogue with much smaller positional uncertainties. We
demonstrate the utility of probabilistic outputs by a controllable completeness
and efficiency trade-off and by identifying objects that have high probability
of being rare. Finally, possible biasing effects in the output of these
classifiers are also highlighted and discussed.


title: SiO Maser Survey of the Inner Bar of the Galactic Bulge

abstract:
  We surveyed 291 MSX/2MASS infrared objects in the 7 x 2 deg area of the
galactic center in the 43 GHz SiO J=1--0 v=1 and 2 maser lines, obtaining
accurate radial velocities of 163 detected objects. The surveyed area is the
region where the IRAS catalog is incomplete due to contamination by high source
density. The objects in the present MSX/2MASS sample were chosen to have
similar infrared characteristics to those of the previous SiO-maser-survey
samples based on the color selected IRAS sources. The sampling based on the
2MASS catalog causes a bias to the foreside objects of the bulge due to heavy
obscuration by interstellar dust; the detections are considerably leaned on the
V_{lsr}<0 side. The l--v diagram reveals two conspicuous features, which were
not present or tenuous in the previous studies: one feature indicating a linear
velocity increase with longitude with |l|<1.5 deg, which is likely associated
with the inner bar, and the other feature having considerably eccentric
velocities more than those of the normal x_1-orbit family feature. The
extinction-corrected K magnitudes (if used as a distance modulus) tend to show
a sequential deposition of these objects along the line of sight toward the
Galactic center depending on their radial velocities. The tendency that
appeared in the distance measures is consistent with the bulge-bar dynamical
model utilizing the periodic orbit families in the bar potential.


title: R Coronae Borealis at the 2003 Light Minimum

abstract:
  High-resolution optical spectra of R CrB obtained in 2003 March is discussed.
The 2003 spectra are compared with the extensive collection of spectra from the
1995-1996 minimum. Spectroscopic features common to the two minima include
sharp emission lines of neutral and singly-ionized atoms, broad emission lines
including He {\sc i}, [N {\sc ii}] 6583 \AA, Na D, and Ca {\sc ii} H & K lines,
and blueshifted aborption lines of Na D, and K {\sc i} resonance lines.
Prominent differences between the 2003 and 1995-96 spectra are seen. The 2003
profiles of Na D, Ca II H & K are fit by a single Gaussian but in 1995-1996 two
Gaussians separated by about 200 km s$^{-1}$ were required. However, the He
{\sc i} broad emission lines are fit by a single Gaussian at all times; the
emitting He and Na-Ca atoms are probably not colocated. The C$_2$ Phillips 2-0
lines are detected as sharp absorption lines in 2003 indicating presence of gas
at 1300 K.The 2003 spectra show C {\sc i} sharp emission lines at minimum light
with a velocity changing in five days by about 20 km s$^{-1}$ when the velocity
of `metal' sharp lines is unchanged; the C {\sc i} emission may arise from
shock-heated gas. Spectra at maximum shows extended blue wings to strong lines
with the extension dependent on a line's lower excitation potential a signature
of stellar wind. Changes in the cores of the resonance lines of Al {\sc i} and
Na D and the Ca {\sc ii} IR lines suggest complex flow patterns near the
photosphere. The spectroscopic differences at the two mimima show the
importance of continued scrutiny of the declines of R CrB.


title:
The chemical compositions of the extreme halo stars HE0107-5240 and
  HE1327-2326 inferred from 3D hydrodynamical model atmospheres

abstract:
  We investigate the impact of realistic 3D hydrodynamical model stellar
atmospheres on the determination of elemental abundances in the carbon-rich,
hyper iron-poor stars HE0107-5240 and HE1327-2326. We derive the chemical
compositions of the two stars by means of a detailed 3D analysis of spectral
lines under the assumption of local thermodynamic equilibrium (LTE). The lower
temperatures of the line-forming regions of the hydrodynamical models cause
changes in the predicted spectral line strengths. In particular we find the 3D
abundances of C, N, and O to be lower by ~ -0.8 dex (or more) than estimated
from a 1D analysis. The 3D abundances of iron-peak elements are also decreased
but by smaller factors (~ -0.2 dex). We caution however that the neglected
non-LTE effects might actually be substantial for these metals. We finally
discuss possible implications for studies of early Galactic chemical evolution.


title:
High-precision elements of double-lined spectroscopic binaries from
  combined interferometry and spectroscopy. Application to the beta Cephei star
  beta Centauri

abstract:
  We present methodology to derive high-precision estimates of the fundamental
parameters of double-lined spectroscopic binaries. We apply the methods to the
case study of the double-lined beta Cephei star beta Centauri. We also present
a detailed analysis of beta Centauri's line-profile variations caused by its
oscillations. We point out that a systematic error in the orbital amplitudes,
and any quantities derived from them, occurs if the radial velocities of
blended component lines are computed without spectral disentangling. This
technique is an essential ingredient in the derivation of the physical
parameters if the goal is to obtain a precision of only a few percent. We have
devised iteration schemes to obtain the orbital elements for systems whose
lines are blended throughout the orbital cycle. We find the following
parameters for beta Cen: $M_1=10.7\pm 0.1 M_\odot$ and $M_2=10.3\pm 0.1
M_\odot$, an age of $(14.1\pm 0.6)\times 10^6$ years. We deduce two oscillation
frequencies for the broad-lined primary of beta Centauri with degrees higher
than 2. We propose that our iteration schemes be used in any future derivations
of the spectroscopic orbital parameters of double-lined binaries with blended
component lines to which disentangling can be successfully applied.


title:
Towards a Phylogenetic Analysis of Galaxy Evolution : a Case Study with
  the Dwarf Galaxies of the Local Group

abstract:
  Context: The Hubble tuning fork diagram has always been the preferred scheme
for classification of galaxies. It is based on morphology only. At the
opposite, biologists have long taken into account the genealogical relatedness
of living entities for classification purposes. Aims: Assuming branching
evolution of galaxies as a 'descent with modification', we show here that the
concepts and tools of phylogenetic systematics widely used in biology can be
heuristically transposed to the case of galaxies. Methods: This approach that
we call "astrocladistics" is applied to Dwarf Galaxies of the Local Group and
provides the first evolutionary tree for real galaxies. Results: The trees that
we present here are sufficiently solid to support the existence of a
hierarchical organization in the diversity of dwarf galaxies of the Local
Group. This also shows that these galaxies all derive from a common ancestral
kind of objects. We find that some kinds of dIrrs are progenitors of both dSphs
and other kinds of dIrrs.We also identify three evolutionary groups, each one
having its own characteristics and own evolution. Conclusions: The present work
opens a new way to analyze galaxy evolution and a path towards a new
systematics of galaxies. Work on other galaxies in the Universe is in progress.


title: Local Group surveys for Planetary Nebulae

abstract:
  The Local Group (LG) represents the best environment to study in detail the
PN population in a large number of morphological types of galaxies. The
closeness of the LG galaxies allows to investigate the faintest side of the PN
luminosity function and to detect PNe also in the less luminous galaxies, the
dwarf galaxies, where a small number of them is expected.
  A review of the results of the most recent imaging surveys in the LG is
presented. Some applications of the surveys for PNe to the study of the star
formation history of the host galaxies are analyzed. In addition, these new
observational data are an invaluable resource for follow-up spectroscopy to
derive the chemical properties of not only PNe, but also other important
emission-line sources like HII regions. These are fundamental tools for the
discussion of the chemical evolution of the host galaxies, mapping the history
of their chemical enrichment at different epochs. The latest results on this
subject are presented.


title: A non-LTE abundance analysis of the post-AGB star ROA 5701

abstract:
  An analysis of high-resolution Anglo-Australian Telescope (AAT)/ University
College London Echelle Spectrograph (UCLES) optical spectra for the ultraviolet
(UV)-bright star ROA 5701 in the globular cluster omega Cen (NGC 5139) is
performed, using non-local thermodynamic equilibrium (non-LTE) model
atmospheres to estimate stellar atmospheric parameters and chemical
composition. Abundances are derived for C, N, O, Mg, Si and S, and compared
with those found previously by Moehler et al. We find a general metal
underabundance relative to young B-type stars, consistent with the average
metallicity of the cluster. Our results indicate that ROA 5701 has not
undergone a gas-dust separation scenario as previously suggested. However, its
abundance pattern does imply that ROA 5701 has evolved off the AGB prior to the
onset of the third dredge-up.


title:
Particle motion and gravitational lensing in the metric of a dilaton
  black hole in a de Sitter universe

abstract:
  We consider the metric exterior to a charged dilaton black hole in a de
Sitter universe. We study the motion of a test particle in this metric.
Conserved quantities are identified and the Hamilton-Jacobi method is employed
for the solutions of the equations of motion. At large distances from the black
hole the Hubble expansion of the universe modifies the effective potential such
that bound orbits could exist up to an upper limit of the angular momentum per
mass for the orbiting test particle. We then study the phenomenon of strong
field gravitational lensing by these black holes by extending the standard
formalism of strong lensing to the non-asymptotically flat dilaton-de Sitter
metric. Expressions for the various lensing quantities are obtained in terms of
the metric coefficients.


title:
Observations of Ultracool dwarfs with ULTRACAM on the VLT: a search for
  weather

abstract:
  We present multi-colour photometry of four field ultracool dwarfs with the
triple-beam photometer ultracam. Data were obtained simultaneously in the
Sloan-g' band and a specially designed narrow-band NaI filter. The previously
reported 1.8-hr period of Kelu-1 is here recovered in the g'-band, but the lack
of any significant variability in the NaI light of this object precludes any
conclusion as to the cause of the variability. 2MASS 2057-0252 and DENIS
1441-0945 show no convincing evidence for variability. 2MASS 1300+1912, on the
other hand, shows good evidence for gradual trends in both bands at the 5%
level. These trends are anti-correlated at a high level of significance, a
result which is incompatible with models of starspot-induced variability. It
would seem likely that dust cloud "weather" is responsible for the short-term
variability in this object.


title:
The Araucaria Project. A Wide-Field Photometric Survey for Cepheid
  Variables in NGC 3109

abstract:
  We have obtained mosaic images of NGC 3109 in the V and I bands on 74 nights,
spanning approximately one year. From these data, we have conducted an
extensive search for Cepheid variables over the entire field of the galaxy,
resulting in the discovery of 113 variables with periods ranging from 3.4 to
31.4 days. In this sample, 76 Cepheids, including many long-period variables,
were not known before. For the previously known 45 Cepheids in this galaxy, our
data proved that reported periods were wrong for 14 objects; for nearly all
other previously known Cepheid variables we were able to significantly improve
on the periods. We construct period-luminosity relations from our data and
obtain reddening-corrected distance moduli of 25.72 $\pm$ 0.05 mag in V, and
25.66 $\pm$ 0.04 mag in I. The distance modulus derived form the
reddening-independent V-I Wesenheit index turns out to be significantly shorter
(25.54 $\pm$ 0.05 mag), which indicates that in addition to the foreground
extinction of E(B-V) = 0.05 mag, there is an intrinsic to NGC 3109 redening of
about 0.05 mag. Our distance obtained based on the reddening-free Wesenheit
magnitudes is consistent with earlier distance determinations of NGC 3109 from
Cepheids, and the tip of the red giant branch. We will improve on our distance
and extinction determination combining our optical data with the follow-up
near-infrared observations of a subsample of NGC 3109 Cepheids.


title: The LISA verification binaries

abstract:
  The Laser Interferometer Space Antenna (LISA) guarantees the detection of
gravitational waves by monitoring a handful of known nearby galactic binary
systems, the so-called ``verification binaries''. We consider the most updated
information on the source parameters for the thirty more promising verification
binaries. We investigate which of them are indeed guaranteed sources for LISA
and estimate the accuracy of the additional information that can be extracted
during the mission. Our analysis considers the two independent Michelson
outputs that can be synthesised from the LISA constellation, and we model the
LISA transfer function using the rigid adiabatic approximation. We carry out
extensive Monte Carlo simulations to explore the dependency of our results on
unknown or poorly constrained source parameters. We find that four sources --
RXJ0806.3+1527, V407 Vul, ES Cet and AM CVn -- are clearly detectable in one
year of observation; RXJ0806.3+1527 should actually be observable in less than
a week. For these sources LISA will also provide information on yet unknown
parameters with an error between approximately 1 percent and 10 percent. Four
additional binary systems -- HP Lib, 4U 1820-30, WZ Sge and KPD 1930+2752 --
might also be marginally detectable.


title:
The INTEGRAL - HESS/MAGIC connection: a new class of cosmic high energy
  accelerators from keV to TeV

abstract:
  The recent completion and operation of the High Energy Stereoscopic System,
an array of ground based imaging Cherenkov telescopes, has provided a survey
with unprecedented sensitivity of the inner part of the Galaxy and revealed a
new population of very high energy gamma-rays sources emitting at E$>$100 GeV.
Most of them were reported to have no known radio or X-ray counterpart and
hypothesised to be representative of a new class of dark nucleonic cosmic
sources. In fact, very high energy gamma-rays with energies E $>$ 10$^{11}$ eV
are the best proof of non-thermal processes in the universe and provide a
direct in-site view of matter-radiation interaction at energies by far greater
than producible in ground accelerators. At lower energy INTEGRAL has regularly
observed the entire galactic plane during the first 1000 day in orbit providing
a survey in the 20-100 keV range resulted in a soft gamma-ray sky populated
with more than 200 sources, most of them being galactic binaries, either BHC or
NS. Very recently, the INTEGRAL new source IGR J18135-1751 has been identified
as the soft gamma-ray counterpart of HESS J1813-178 and AXJ1838.0-0655 as the
X/gamma-ray counterpart of HESS J1837-069.
  Detection of non thermal radio, X and gamma-ray emission from these TeV
sources is very important to discriminate between various emitting scenarios
and, in turn, to fully understand their nature.
  The implications of these new findings in the high energy Galactic population
will be addressed.


title: Variability of V838 Mon Before Its Outburst

abstract:
  Archival observations of the progenitor of V838 Mon were re-calibrated as
well as multiple images from the 2MASS and the DENIS near infrared surveys.
Both - the better calibrated values as well as the variability found in the
photographic material has strong effects for the fitting of the spectral energy
distribution of the progenitor.


title:
Early multi-wavelength emission from Gamma-ray Bursts: from Gamma-ray to
  X-ray

abstract:
  The study of the early high-energy emission from both long and short
Gamma-ray bursts has been revolutionized by the Swift mission. The rapid
response of Swift shows that the non-thermal X-ray emission transitions
smoothly from the prompt phase into a decaying phase whatever the details of
the light curve. The decay is often categorized by a steep-to-shallow
transition suggesting that the prompt emission and the afterglow are two
distinct emission components. In those GRBs with an initially steeply-decaying
X-ray light curve we are probably seeing off-axis emission due to termination
of intense central engine activity. This phase is usually followed, within the
first hour, by a shallow decay, giving the appearance of a late emission hump.
The late emission hump can last for up to a day, and hence, although faint, is
energetically very significant. The energy emitted during the late emission
hump is very likely due to the forward shock being constantly refreshed by
either late central engine activity or less relativistic material emitted
during the prompt phase. In other GRBs the early X-ray emission decays
gradually following the prompt emission with no evidence for early temporal
breaks, and in these bursts the emission may be dominated by classical
afterglow emission from the external shock as the relativistic jet is slowed by
interaction with the surrounding circum-burst medium. At least half of the GRBs
observed by Swift also show erratic X-ray flaring behaviour, usually within the
first few hours. The properties of the X-ray flares suggest that they are due
to central engine activity. Overall, the observed wide variety of early
high-energy phenomena pose a major challenge to GRB models.


title:
The Araucaria Project. An Accurate Distance to the Local Group Galaxy
  NGC 6822 from Near-Infrared Photometry of Cepheid Variables

abstract:
  We have measured near-infrared magnitudes in the J and K bands for 56 Cepheid
variables in the Local Group galaxy NGC 6822 with well-determined periods and
optical light curves in the V and I bands. Using the template light curve
approach of Soszynski, Gieren and Pietrzynski, accurate mean magnitudes were
obtained from these data which allowed us to determine with unprecedented
accuracy the distance to NGC 6822 from a multi-wavelength period-luminosity
solution in the VIJK bands. From our data, we obtain a distance to NGC 6822 of
(m-M)_{0} = 23.312 +- 0.021 (random error) mag, with an additional systematic
uncertainty of about 3 %. This distance value is tied to an assumed LMC
distance modulus of 18.50. From our multiwavelength approach, we find for the
total (average) reddening to the NGC 6822 Cepheids E(B-V) = 0.356 +- 0.013 mag,
which is in excellent agreement with a previous determination of McGonegal et
al. from near-infrared photometry and implies significant internal reddening of
the Cepheids in NGC 6822. Our present, definitive distance determination of NGC
6822 from Cepheids agrees within 2 % with the previous distance we had derived
from optical photometry alone, but has significantly reduced error bars.
  Our Cepheid distance to NGC 6822 is in excellent agreement with the recent
independent determination of Cioni and Habing from the I-band magnitude of the
tip of the red giant branch. It also agrees well, within the errors, with the
early determination of McGonegal et al. (1983) from random-phase H-band
photometry of nine Cepheids.


title: A Time Variation of Proton-Electron Mass Ratio and Grand Unification

abstract:
  Astrophysical observations indicate a time variation of the proton-electron
mass ratio and of the fine-structure constant. We discuss this phenomenon in
models of Grand Unification. In these models a time variation of the
fine-structure constant and of the proton mass are expected, if either the
unified coupling constant or the scale of unification changes, or both change.
We discuss in particular the change of the proton mass. Experiments in Quantum
Optics could be done to check these ideas.


title: Dynamic Alignment and Exact Scaling Laws in MHD Turbulence

abstract:
  Magnetohydrodynamic (MHD) turbulence is pervasive in astrophysical systems.
Recent high-resolution numerical simulations suggest that the energy spectrum
of strong incompressible MHD turbulence is $E(k_{\perp})\propto
k_{\perp}^{-3/2}$. So far, there has been no phenomenological theory that
simultaneously explains this spectrum and satisfies the exact analytic
relations for MHD turbulence due to Politano & Pouquet. Indeed, the
Politano-Pouquet relations are often invoked to suggest that the spectrum of
MHD turbulence instead has the Kolmogorov scaling -5/3. Using geometrical
arguments and numerical tests, here we analyze this seeming contradiction and
demonstrate that the -3/2 scaling and the Politano-Pouquet relations are
reconciled by the phenomenon of scale-dependent dynamic alignment that was
recently discovered in MHD turbulence.

categories: astro-ph nlin.CD physics.flu-dyn physics.plasm-ph


title: On the formation of H-alpha line emission around classical T Tauri stars

abstract:
  We present radiative transfer models of the circumstellar environment of
classical T Tauri stars, concentrating on the formation of the H-alpha
emission. The wide variety of line profiles seen in observations are indicative
of both inflow and outflow, and we therefore employ a circumstellar structure
that includes both magnetospheric accretion and a disc wind. We perform
systematic investigations of the model parameters for the wind and the
magnetosphere to search for possible geometrical and physical conditions which
lead to the types of profiles seen in observations. We find that the hybrid
models can reproduce the wide range of profile types seen in observations, and
that the most common profile types observed occupy a large volume of parameter
space. Conversely, the most infrequently observed profile morphologies require
a very specific set of models parameters. We find our model profiles are
consistent with the canonical value of the mass-loss rate to mass-accretion
rate ratio (mu=0.1) found in earlier magneto-hydrodynamic calculations and
observations, but the models with 0.05<mu<0.2 are still in accord with observed
H-alpha profiles. We investigate the wind contribution to the line profile as a
function of model parameters, and examine the reliability of H-alpha as a mass
accretion diagnostic. Finally, we examine the H-alpha spectroscopic
classification used by Reipurth et. al, and discuss the basic physical
conditions that are required to reproduce the profiles in each classified type.


title:
bHROS high spectral resolution observations of PN forbidden and
  recombination line profiles

abstract:
  We have acquired high spectral resolution observations (R=150,000) of the
planetary nebulae NGC 7009 and NGC 6153, using bHROS on Gemini South.
Observations of this type may provide a key to understanding why optical
recombination lines (ORLs) yield systematically higher heavy element abundances
for photoionized nebulae than do the classical forbidden collisionally excited
lines (CELs) emitted by the same ions; NGC 7009 and NGC 6153 have notably high
ORL/CEL abundance discrepancy factors (ADFs) of 5 and 10, respectively. Due to
the opposite temperature dependences of ORLs and CELs, ORLs should be
preferentially emitted by colder plasma. Our bHROS observations of NGC 7009
reveal that the [O III] 4363A CEL has a FWHM linewidth that is 1.5 times larger
than that shown by O II ORLs in the same spectrum, despite the fact that all of
these lines are emitted by the O2+ ion. The bHROS spectra of NGC 6153 also show
that its O II ORLs have significantly narrower linewidths than do the [O III]
4363A and 5007A lines but, in addition, the [O III] 4363A and 5007A lines show
very different velocity profiles, implying the presence of large temperature
variations in the nebula.


title:
On the X-ray, optical emission line and black hole mass properties of
  local Seyfert galaxies

abstract:
  We investigate the relation between X-ray nuclear emission, optical emission
line luminosities and black hole masses for a sample of 47 Seyfert galaxies.
The sample, which has been selected from the Palomar optical spectroscopic
survey of nearby galaxies (Ho, Filippenko & Sargent 1997), covers a wide range
of nuclear powers, from L_{2-10 keV} ~ 10^{43} erg/s down to very low
luminosities (L_{2-10 keV} ~ 10^{38} erg/s). Best available data from Chandra,
XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks
to the good spatial resolution available from these observations and a proper
modeling of the various spectral components, it has been possible to obtain
accurate nuclear X-ray luminosities not contaminated by off-nuclear sources
and/or diffuse emission. X-ray luminosities have then been corrected taking
into account the likely candidate Compton thick sources, which are a high
fraction (> 30%) among type 2 Seyferts in our sample. The main result of this
study is that we confirm strong linear correlations between 2-10 keV,
[OIII]\lambda5007, H_{alpha} luminosities which show the same slope as quasars
and luminous Seyfert galaxies, independent of the level of nuclear activity
displayed. Moreover, despite the wide range of Eddington ratios (L/L_{Edd})
tested here (six orders of magnitude, from 0.1 down to ~ 10^{-7}), no
correlation is found between the X-ray or optical emission line luminosities
and the black hole mass. Our results suggest that Seyfert nuclei in our sample
are consistent with being a scaled-down version of more luminous AGN.


title: A comparative study of disc-planet interaction

abstract:
  We perform numerical simulations of a disc-planet system using various
grid-based and smoothed particle hydrodynamics (SPH) codes. The tests are run
for a simple setup where Jupiter and Neptune mass planets on a circular orbit
open a gap in a protoplanetary disc during a few hundred orbital periods. We
compare the surface density contours, potential vorticity and smoothed radial
profiles at several times. The disc mass and gravitational torque time
evolution are analyzed with high temporal resolution. There is overall
consistency between the codes. The density profiles agree within about 5% for
the Eulerian simulations while the SPH results predict the correct shape of the
gap although have less resolution in the low density regions and weaker
planetary wakes. The disc masses after 200 orbital periods agree within 10%.
The spread is larger in the tidal torques acting on the planet which agree
within a factor 2 at the end of the simulation. In the Neptune case the
dispersion in the torques is greater than for Jupiter, possibly owing to the
contribution from the not completely cleared region close to the planet.


title:
Detection of [OI] 6300 and Other Diagnostic Emission Lines in the
  Diffuse Ionized Gas of M33 with Gemini-North

abstract:
  We present spectroscopic observations of diffuse ionized gas (DIG) in M33
near the HII region NGC 604. We present the first detection of [OI] 6300 in the
DIG of M33, one of the critical lines for distinguishing photo- from shock
ionization models. We measure [OI]/Ha in the range of 0.04 to 0.10 and an
increase in this ratio with decreasing emission measure. Our measurements of
[SII]/Ha and [NII]/Ha also rise with decreasing emission measure, while our
[OIII]/Hb measurements remain fairly constant. We have one tentative detection
of He I in the region of brightest emission measure, with a ratio of He I/Ha =
0.033 +- 0.019, indicating that the helium is at least partially ionized. We
compare our observed emission line ratios to photoionization models and find
that field star ionization models do not fit our data well. Leaky HII region
models are consistent with our data, without the need to invoke additional
ionization mechanisms to fit our [OI] or [OIII] measurements. The closest large
HII region is NGC 604 and is therefore a likely candidate for the source of the
ionizing photons for the gas in this region.


title: Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy

abstract:
  A new, 2.8 deg^2 J,H,K_s infrared survey from the 2MASS 6x program across the
extent of the optical disk of the Andromeda (M31) galaxy provides a clear view
of the M31 center almost completely unfettered by dust extinction, and reveals
a high contrast bulge with extremely boxy isophotes dominating the NIR light to
a semi-major axis of ~700''(2.6 kpc). The inner bulge (<~50'') is relatively
circular, but shows some isophotal twisting. Beyond this, the ellipticity and
boxiness of the bulge increase with radius -- achieving a boxiness that rivals
that of any other known disk galaxy observed in the near infrared -- and the
position angle is constant at ~50 deg, which is about 10 deg higher than the
position angle of the M31 disk. Boxy bulges in highly inclined disks have been
shown to be the vertical structure of bars, and self-consistent, N-body
modeling specific to the NIR images presented here can reproduce the observed
NIR M31 features with a combination of a classical bulge and a boxy bulge/bar.
Beyond the boxy bulge region and nearly along the 40 deg position angle of the
disk a narrow ridge of infrared flux, which can be identified with the thin
part of the bar, more or less symmetrically extends into the inner disk at
semi-major axis radii of 700'' to 1200'' or more. Little variation in the
morphology or relative brightnesses of these various M31 structures is seen
across the NIR bands (i.e., no color gradients are seen). These new data verify
that M31 is a barred spiral galaxy like the Milky Way.


title:
Loki, Io: New groundbased observations and a model describing the change
  from periodic overturn

abstract:
  Loki Patera is the most powerful volcano in the solar system. We have
obtained measurements of Loki's 3.5 micron brightness from NASA's Infrared
Telescope Facility (IRTF) and have witnessed a change from the periodic
behavior previously noted. While Loki brightened by a factor of several every
540 days prior to 2001, from 2001 through 2004 Loki remained at a constant,
medium brightness. We have constructed a quantitative model of Loki as a
basaltic lava lake whose solidified crust overturns when it becomes buoyantly
unstable. By altering the speed at which the overturn propagates across the
patera, we can match our groundbased brightness data. In addition, we can match
other data taken at other times and wavelengths. By slowing the propagation
speed dramatically, we can match the observations from 2001-2004. This slowing
may be due to a small change in volatile content in the magma.


title:
Far-Ultraviolet & X-ray Observations of VV 114: Feedback in a Local
  Analog to Lyman Break Galaxies

abstract:
  We have analyzed FUSE, XMM, and Chandra observations of VV 114, a local
galaxy merger with strong similarities to typical high-redshift Lyman Break
Galaxies (LBGs). Diffuse thermal X-ray emission encompassing VV114 has been
observed by Chandra and XMM. This region of hot (kT~0.59 keV) gas has an
enhanced alpha to iron element ratio relative to solar abundances and follows
the same relation as typical starbursts between its properties (luminosity,
size, and temperature) and those of the starburst galaxy (star formation rate,
dust temperature, galaxy mass). These results are consistent with the X-ray gas
having been produced by shocks driven by a galactic superwind. The FUSE
observations of VV 114 show strong, broad interstellar absorption lines with a
pronounced blueshifted component(similar to what is seen in LBGs). This implies
an outflow of material moving at 300-400 km/s relative to VV 114. The
properties of the strong OVI absorption line are consistent with radiative
cooling at the interface between the hot outrushing gas seen in X-rays and the
cooler material seen in the other outflowing ions in the FUSE data. We show
that the wind in VV114 has not created a ``tunnel'' that enables more than a
small fraction (< few percent) of the ionizing photons from VV114 to escape
into the IGM. Taken together, these data provide a more complete physical basis
for understanding the outflows that seem to be generic in LBGs. This will lead
to improved insight into the role that such outflows play in the evolution of
galaxies and the inter-galactic medium.


title: The vacuum energy crisis

abstract:
  The smallness of the vacuum energy density and its near coincidence with the
average matter density of the universe are naturally explained by anthropic
selection. An alternative explanation, based on the cyclic model of Steinhardt
and Turok, does not address the coincidence problem and is therefore less
convincing. This article appeared in ``Science'' (4 May 2006) as a
``perspective'' for Steinhardt and Turok's paper in the same issue
(astro-ph/0605173).


title:
The Araucaria Project: Distance to the Local Group Galaxy NGC 3109 from
  Near-Infrared Photometry of Cepheids

abstract:
  We present near-infrared J- and K-band photometry of 77 Cepheid variables in
the Local Group galaxy NGC 3109. Combining our data with the previously
published optical V- and I-band photometry of Cepheids in this galaxy we derive
an accurate distance and interstellar reddening to NGC 3109. Adopting a
distance modulus of 18.5 mag for the Large Magellanic Cloud, we obtain a true
distance modulus to NGC 3109 of (m-M)_0 = 25.571 +- 0.024 mag (random error),
corresponding to a distance of 1.30 +- 0.02 Mpc. The systematic uncertainty on
this value (apart from the adopted LMC distance) is of the order of +-3%, the
main contributors to this value being the uncertainty on the photometric zero
points, and the effect of blending with unresolved companion stars. The total
reddening determined from our multiwavelength solution is E(B-V)=0.087 +- 0.012
mag. About half of the reddening is produced internal to NGC 3109. Our distance
result is consistent with previous determinations of the distance to NGC 3109,
but has significantly reduced error bars.


title: Carbon stars in local group dwarf galaxies: C and O abundances

abstract:
  We present abundances of carbon and oxygen as well as abundance ratios
12C/13C for a sample of carbon stars in the LMC, SMC, Carina, Sculptor and
Fornax dwarf galaxies. The overall metallicities in these dwarf galaxies are
lower than in the galactic disc. The observations cover most of the AGB and we
discuss the abundance patterns in different regions along the AGB. The
abundances are determined from infrared spectra obtained with the ISAAC
spectrometer on VLT (R=1500) and the Phoenix Spectrometer on Gemini South
(R=50000). The synthetic spectra used in the analysis were computed with MARCS
model atmospheres. We find that the oxygen abundance is decreasing with
decreasing overall metallicity of the system while the C/O ratio at a given
evolutionary phase is increasing with decreasing oxygen abundance. keywords
Stars: abundances -- Stars: carbon -- Stars: AGB and post-AGB -- Galaxies:
dwarf -- Local Group -- Infrared: stars


title: Cosmography with cluster strong lensing

abstract:
  By stacking an ensemble of strong lensing clusters, we demonstrate the
feasibility of placing constraints on the dark energy equation of state. This
is achieved by using multiple images of sources at two or more distinct
redshift planes. The sample of smooth clusters in our simulations is based on
observations of massive clusters and the distribution of background galaxies is
constructed using the Hubble Deep Field. Our source distribution reproduces the
observed redshift distribution of multiply imaged sources in Abell 1689. The
cosmology recovery depends on the number of image families with known
spectroscopic redshifts and the number of stacked clusters. Our simulations
suggest that constraints comparable to those derived from other competing
established techniques on a constant dark energy equation of state can be
obtained using 10 to 40 clusters with 5 or more families of multiple images. We
have also studied the observational errors in the image redshifts and
positions. We find that spectroscopic redshifts and high resolution {\it Hubble
Space Telescope} images are required to eliminate confidence contour relaxation
relative to the ideal case in our simulations. This suggests that the dark
energy equation of state, and other cosmological parameters, can be constrained
with existing {\it Hubble Space Telescope} images of lensing clusters coupled
with dedicated ground-based arc spectroscopy.


title:
Newly arising problems in the research of SU UMa-type dwarf novae from
  VSNET collaborations

abstract:
  Our research on variable objects based on the VSNET collaborations has
achieved much progress in understanding the nature of many kinds of phenomena.
Many problems have appeared, instead. Among them, we here review three newly
arising problems in the research of SU UMa-type dwarf novae: 1) how do EI Psc
and V485 Cen evolve as a cataclysmic variable?, 2) is the early superhump a
particular phenomenon for WZ Sge-type dwarf novae?, and 3) what parameters
determine variations of the superhump period?


title:
The First Extrasolar Planet Discovered with a New Generation High
  Throughput Doppler Instrument

abstract:
  We report the detection of the first extrasolar planet, ET-1 (HD 102195b),
using the Exoplanet Tracker (ET), a new generation Doppler instrument. The
planet orbits HD 102195, a young star with solar metallicity that may be part
of the local association. The planet imparts radial velocity variability to the
star with a semiamplitude of $63.4\pm2.0$ m s$^{-1}$ and a period of 4.11 days.
The planetary minimum mass ($m \sin i$) is $0.488\pm0.015$ $M_J$.


title: New Analytical Formula for Supercritical Accretion Flows

abstract:
  We examine a new family of global analytic solutions for optically thick
accretion disks, which includes the supercritical accretion regime. We found
that the ratio of the advection cooling rate, $Q_{\rm adv}$, to the viscous
heating rate, $Q_{\rm vis}$, i.e., $f=Q_{\rm adv}/Q_{\rm vis}$, can be
represented by an analytical form dependent on the radius and the mass
accretion rate. The new analytic solutions can be characterized by the
photon-trapping radius, $\rtrap$, inside which the accretion time is less than
the photon diffusion time in the vertical direction; the nature of the
solutions changes significantly as this radius is crossed. Inside the trapping
radius,
  $f$ approaches $f \propto r^0$, which corresponds to the advection-dominated
limit ($f \sim 1$), whereas outside the trapping radius, the radial dependence
of $f$ changes to $f \propto r^{-2}$, which corresponds to the
radiative-cooling-dominated limit. The analytical formula for $f$ derived here
smoothly connects these two regimes. The set of new analytic solutions
reproduces well the global disk structure obtained by numerical integration
over a wide range of mass accretion rates, including the supercritical
accretion regime. In particular, the effective temperature profiles for our new
solutions are in good agreement with those obtained from numerical solutions.
Therefore, the new solutions will provide a useful tool not only for evaluating
the observational properties of accretion flows, but also for investigating the
mass evolution of black holes in the presence of supercritical accretion flows.


title:
The Three Dimensional Structural Shape of the Gravitational Potential in
  the Local Group

abstract:
  The Local Group is a small galaxy cluster with the membership of 62 nearby
galaxies including the Milky Way and M31. Although the Local Group has yet to
be virialized, it interacts with the surrounding matter as one gravitationally
bound system. To understand the formation and evolution of the Local Group as
well as its member galaxies, it is important to reconstruct the gravitational
potential field from the surrounding matter distribution in the local cosmic
web. By measuring the anisotropy in the spatial distribution of the Local Group
galaxies, which is assumed to be induced by the local gravitational tidal field
, we resolve the three dimensional structure of the gravitational potential in
the vicinity of the Milky Way smoothed on the Local Group mass scale. Our
results show that (i) the minor principal axis of the Local Group tidal field
is in the equatorial direction of alpha_{p}=15^{h}00^{m} and delta_{p}=20^{d};
(ii) it has a prolate shape with axial ratio of 0.5 +/- 0.13; (iii) the global
tides in the Local Group is quite strong, which may provide a partial
explanation for the low abundance of dwarf galaxies in the Local Group.


title:
Improving the Lagrangian perturbative solution for cosmic fluid:
  Applying Shanks transformation

abstract:
  We study the behavior of Lagrangian perturbative solutions. For a spherical
void model, the higher order the Lagrangian perturbation we consider, the worse
the approximation becomes in late-time evolution. In particular, if we stop to
improve until an even order is reached, the perturbative solution describes the
contraction of the void. To solve this problem, we consider improving the
perturbative solution using Shanks transformation, which accelerates the
convergence of the sequence. After the transformation, we find that the
accuracy of higher-order perturbation is recovered and the perturbative
solution is refined well. Then we show that this improvement method can apply
for a $\Lambda$CDM model and improved the power spectrum of the density field.


title:
Measurement of non-axisymmetry in centres of advanced mergers of
  galaxies

abstract:
  We measure the non-axisymmetry in the luminosity distribution in the inner
few kpc of the remnants of advanced mergers of galaxies with a view to
understand the relaxation in the central regions. For this, we analyze the
images from the 2MASS archival data for a selected sample of 12 merging
galaxies, which show signs of interaction but have a single nucleus. The
central regions are fitted by elliptical isophotes whose centres are allowed to
vary to get the best fit. The centres of isophotes show a striking sloshing
pattern with a spatial variation of up to 20-30 % within the central 1 kpc.
This indicates mass asymmetry and a dynamically unrelaxed behaviour. Next, we
Fourier-analyze the galaxy images while keeping the centre constant and measure
the deviation from axisymmetry in terms of the fractional Fourier amplitudes
(A_1, A_2 etc) as a function of radius. All mergers show a high value of
lopsidedness (upto A_1 ~ 0.2) in the central 5 kpc. The m=2 asymmetry is even
stronger, with values of A_2 upto ~ 0.3, and in three cases these are shown to
represent bars. The corresponding values denoting non-axisymmetry in inner
regions of a control sample of eight non-merger galaxies are found to be
several times smaller. Surprisingly, this central asymmetry is seen even in
mergers where the outer regions have relaxed into a smooth elliptical-like
r^{1/4} profile or a spiral-like exponential profile. Thus the central
asymmetry is long-lived, estimated to be ~ 1 Gyr, and hence lasts for over 100
local dynamical timescales. These central asymmetries are expected to play a
key role in the future dynamical evolution of the central region of a merger,
and can help in feeding a central AGN.


title:
Tidal tails around globular clusters: are they good tracers of cluster
  orbits?

abstract:
  In the last decade, observational studies have shown the existence of tidal
streams in the outer part of many galactic globular clusters. The most striking
examples of clusters with well defined tidal tails are represented by Palomar 5
and NGC 5466 (both observed in the framework of the Sloan Digital Sky Survey),
which show structures elongated for 4 kpc and 1 kpc in length, respectively.
Unfortunately, most of the observational studies about globular clusters (GCs)
do not cover such a large field of the sky as the SDSS does. In this framework,
by mean of a parallel, adaptive tree-code, we performed detailed N-body
simulations of GCs moving in a realistic three-components (bulge, disk and
halo) Milky Way potential, in order to clarify whether and to what extent tails
in the clusters outer regions (few tidal radii) are tracers of the local orbits
and, also, if some kind of correlation exists among the cluster orbital phase
and the orientation of such streams.


title:
Diffraction Limited Imaging Spectroscopy of the SgrA* Region using
  OSIRIS, a new Keck Instrument

abstract:
  We present diffraction limited spectroscopic observations of an infrared
flare associated with the radio source SgrA*. These are the first results
obtained with OSIRIS, the new facility infrared imaging spectrograph for the
Keck Observatory operated with the laser guide star adaptive optics system.
After subtracting the spectrum of precursor emission at the location of Sgr A*,
we find the flare has a spectral index of -2.6 +- 0.9. If we do not subtract
the precursor light, then our spectral index is consistent with earlier
observations by Ghez et al. (2005). All observations published so far suggest
that the spectral index is a function of the flare's K-band flux.


title:
Indirect Dark Matter Search: Cosmic Positron Fraction Measurement from 1
  to 50 GeV with AMS-01

abstract:
  A new measurement of the cosmic ray positron fraction in the energy range of
1-50 GeV is presented. The measurement is based on data taken by the AMS-01
experiment during its 10 day space shuttle flight in June 1998. A proton
background suppression in the order of 10^6 is reached by identifying converted
bremsstrahlung photons emitted from electrons and positrons.


title: $^6$Li Production by the Radiative Decay of Long-Lived Particles

abstract:
  Recent spectroscopic observations of metal poor stars have indicated that
both $^7$Li and $^6$Li have abundance plateaus with respect to the metallicity.
Abundances of $^7$Li are about a factor three lower than the primordial
abundance predicted by standard big-bang nucleosynthesis (SBBN), and $^6$Li
abundances are $\sim 1/20$ of $^7$Li, whereas SBBN predicts negligible amounts
of $^6$Li compared to the detected level. These discrepancies suggest that
$^6$Li has another cosmological or Galactic origin than the SBBN. Furthermore,
it would appear that $^7$Li (and also $^6$Li) has been depleted from its
primordial abundance by some post-BBN processes. In this paper we study the
possibility that the radiative decay of long-lived particles has affected the
cosmological lithium abundances. We calculate the non-thermal nucleosynthesis
associated with the radiative decay and explore the allowed region of the
parameters specifying the properties of long-lived particles. We also impose
constraints from observations of the CMB energy spectrum. We find that
non-thermal nucleosynthesis produces $^6$Li at the level detected in metal poor
halo stars (MPHSs), when the lifetime of the unstable particles is of the order
$\sim 10^8-10^{12}$~s and their initial abundance with respect to that of the
photons is $\sim (10^{-13}-10^{-12}~{\rm GeV})/E_{\gamma 0}$, where $E_{\gamma
0}$ is the emitted photon energy in the radiative decay. We conclude that the
most likely nucleosynthetic scenario involves two different processes. First, a
non-thermal cosmological nucleosynthesis associated with the radiative decay of
unstable particles; and second, the stellar depletion of both of the primordial
lithium isotopic abundances.


title: The first Swift X-ray Flash: The faint afterglow of XRF 050215B

abstract:
  We present the discovery of XRF 050215B and its afterglow. The burst was
detected by the Swift BAT during the check-out phase and observations with the
X-ray telescope began approximately 30 minutes after the burst. These
observations found a faint, slowly fading X-ray afterglow near the centre of
the error box as reported by the BAT. Infrared data, obtained at UKIRT after 10
hours also revealed a very faint K-band afterglow. The afterglow appear unusual
since it is very faint, especially in the infrared with K>20 only 9 hours post
burst. The X-ray and infrared lightcurves exhibit a slow, monotonic decay with
alpha=0.8 and no evidence for steepening associated with the jet break to 10
days post burst. We discuss possible explanations for the faintness and slow
decay in the context of present models for the production of X-ray Flashes.


title: Shock excitation of the knots of Hen 3-1475

abstract:
  We present new optical STIS HST spectroscopic observations of the jets of the
proto-planetary nebula Hen 3-1475. The excitation conditions of the knots of
Hen 3-1475 are derived from the observed optical spectra, confirming that the
knots are shock excited. The shocked spectra are qualitatively reproduced by
simple ``3/2''D bow shock models. We present a set of bow shock models devoted
to planetary nebulae, and discuss the effects of the pre-ionization conditions,
the bow shock velocity, the bow shock shape and the chemical abundances on the
predicted spectra.
  To explore the reliability of the ``3/2''D bow shock models, we also compare
the observed spectra of other three proto-planetary nebulae (M 1-92, M 2-56 and
CRL 618) to the predicted spectra.


title:
Generation of density inhomogeneities by magnetohydrodynamic waves in
  two dimensions

abstract:
  Using two dimensional simulations, we study the formation of structures with
a high-density contrast by magnetohydrodynamic waves in regions in which the
ratio of thermal to magnetic pressure is small. The initial state is a uniform
background perturbed by fast-mode wave. Our most significant result is that
dense structures persist for far longer in a two-dimensional simulation than in
the one-dimensional case. Once formed, these structures persist as long as the
fast-mode amplitude remains high.


title:
Models of Forbidden Line Emission Profiles from Axisymmetric Stellar
  Winds

abstract:
  A number of strong infrared forbidden lines have been observed in several
evolved Wolf-Rayet star winds, and these are important for deriving metal
abundances and testing stellar evolution models. In addition, because these
optically thin lines form at large radius in the wind, their resolved profiles
carry an imprint of the asymptotic structure of the wind flow. This work
presents model forbidden line profile shapes formed in axisymmetric winds. It
is well-known that an optically thin emission line formed in a spherical wind
expanding at constant velocity yields a flat-topped emission profile shape.
Simulated forbidden lines are produced for a model stellar wind with an
axisymmetric density distribution that treats the latitudinal ionization
self-consistently and examines the influence of the ion stage on the profile
shape. The resulting line profiles are symmetric about line centre. Within a
given atomic species, profile shapes can vary between centrally peaked, doubly
peaked, and approximately flat-topped in appearance depending on the ion stage
(relative to the dominant ion) and viewing inclination. Although application to
Wolf-Rayet star winds is emphasized, the concepts are also relevant to other
classes of hot stars such as luminous blue variables and Be/B[e] stars.


title:
Dissipationless collapse, weak homology and central cores of elliptical
  galaxies

abstract:
  By means of high-resolution N-body simulations we revisited the
dissipationless collapse scenario for galaxy formation. We considered both
single-component collapses and collapses of a cold stellar distribution in a
live dark matter halo. Single-component collapses lead to stellar systems whose
projected profiles are fitted very well by the Sersic R^(1/m) law with 3.6 < m
< 8. The stellar end-products of collapses in a dark matter halo are still well
described by the R^(1/m) law, but with 1.9 < m < 12, where the lowest m values
are obtained when the halo is dominant. In all the explored cases the profiles
at small radii deviate from their global best-fit R^(1/m) model, being
significantly flatter. The break-radius values are comparable with those
measured in `core' elliptical galaxies, and are directly related to the
coldness of the initial conditions. The dissipationless collapse of initially
cold stellar distributions in pre-existing dark matter haloes may thus have a
role in determining the observed weak homology of elliptical galaxies.


title:
Faint U-Band Dropouts in the WFPC2 Parallels of the Hubble Ultra Deep
  Field

abstract:
  We combine data from the extremely deep Hubble Space Telescope $U$ (F300W)
image obtained using WFPC2 as part of the parallel observations of the Hubble
Ultra Deep Field campaign, with $BVi$ images from the Great Observatories
Origins Deep Survey (GOODS) to identify a sample of Lyman break galaxies in the
redshift range $2.0 \lesssim z \lesssim 3.5$. We use recent stellar population
synthesis models with a wide variety of ages, metallicities, redshifts, and
dust content, and a detailed representation of the \HI cosmic opacity as a
function of redshift to model the colors of galaxies in our combination of
WFPC2/ACS filters. Using these models, we derive improved color selection
criteria that provide a clean selection of relatively unobscured, star forming
galaxies in this redshift range. Our WFPC2/F300W image is the deepest image
ever obtained at that wavelength. The $10\sigma$ limiting magnitude measured
over 0.2 arcsec$^2$ is 27.5 magnitudes in the WFPC2/F300W image, about 0.5
magnitudes deeper than the F300W image in the Hubble Deep Field (HDF)-N. This
extra depth relative to the HDFs allows us to directly probe the luminosity
function about 0.5 magnitudes deeper than the depth accessible with the HDF
data along an independent line of sight. Our sample of star-forming galaxies
with $2.0 \lesssim z \lesssim 3.5$ includes 125 objects, the majority of which
show clumpy morphologies. We measure a star formation rate density of 0.18
  $M_\odot \rm yr^{-1} Mpc^{-3}$, marginally higher than the value measured for
the Hubble Deep Fields.


title:
Galaxies in the Hubble Ultra Deep Field: I. Detection, Multiband
  Photometry, Photometric Redshifts, and Morphology

abstract:
  We present aperture-matched PSF-corrected BVi'z'JH photometry and Bayesian
photometric redshifts (BPZ) for objects detected in the Hubble Ultra Deep Field
(UDF), 8,042 of which are detected at the 10-sigma level (e.g., i'<29.01 or
z'<28.43). Most of our objects are defined identically to those in the public
STScI catalogs, enabling straightforward object-by-object comparison. We have
combined detections from i', z', J+H, and B+V+i'+z' images into a single
comprehensive segmentation map. Using a new program called SExSeg we are able
to force this segmentation map into SExtractor for photometric analysis. The
resulting photometry is corrected for the wider NIC3 PSFs using our ColorPro
software. We also correct for the ACS z'-band PSF halo. The NIC3 magnitudes are
found to be too faint relative to the ACS fluxes. Based on BPZ SED fits to
objects of know spectroscopic redshift, we derived corrections of -0.30 +/-
0.03 mag in J and -0.18 +/- 0.04 mag in H. The offsets appear to be supported
by a recent recalibration of the UDF NIC3 images combined with non-linearity
measured in NICMOS itself. The UDF reveals a large population of faint blue
galaxies (presumably young starbursts), bluer than those observed in the
original Hubble Deep Fields (HDF). To accommodate these galaxies, we have added
two new starburst templates to the SED library used in previous BPZ papers. The
resulting photometric redshifts are accurate to within 0.04 * 1+z_spec out to z
< 6. Finally, we measure galaxy morphology, including Sersic index and
asymmetry. Our full catalog, software packages, and more are available at
http://adcam.pha.jhu.edu/~coe/UDF/ (abridged)


title:
A multiwavelength radial velocity search for planets around the brown
  dwarf LP 944-20

abstract:
  The nearby brown dwarf LP 944-20 has been monitored for radial velocity
variability at optical and near-infrared wavelengths using the VLT/UVES and the
Keck/NIRSPEC spectrographs, respectively. The UVES radial velocity data
obtained over 14 nights spanning a baseline of 841 days shows significant
variability with an amplitude of 3.5 km s$^{-1}$. The periodogram analysis of
the UVES data indicates a possible period between 2.5 hours and 3.7 hours,
which is likely due to the rotation of the brown dwarf. However, the NIRSPEC
data obtained over 6 nights shows an rms dispersion of only 0.36 km s$^{-1}$
and do not follow the periodic trend. These results indicate that the
variability seen with UVES is likely to be due to rotationally modulated
inhomogeneous surface features. We suggest that future planet searches around
very low-mass stars and brown dwarfs using radial velocities will be better
conducted in the near-infrared than in the optical.


title:
Groups of galaxies: relationship between environment and galaxy
  properties

abstract:
  We analyse how the properties of galaxies in groups identified in the Sloan
Digital Sky Survey depend on the environment. In particular, we study the
relationship between galaxy properties and group mass and group-centric
distance. Among the galaxy properties we have considered here, we find that the
$g-r$ colour is the most predictive parameter for group mass, while the most
predictive pair of properties are $g-r$ colour and $r-$band absolute magnitude.
Regarding the position inside the systems, the $g-r$ colour is the best tracer
of group-centric distance and the most predictive pair of properties are $g-r$
colour and spectral type taken together. These results remain unchanged when a
subsample of high mass groups is analysed. The same happens if the brightest
group galaxies are excluded.


title:
The N/O Plateau of Blue Compact Galaxies: Monte Carlo Simulations of the
  Observed Scatter

abstract:
  Chemical evolution models and Monte Carlo simulation techniques have been
combined for the first time to study the distribution of blue compact galaxies
on the N/O plateau. Each simulation comprises 70 individual chemical evolution
models. For each model, input parameters relating to a galaxy's star formation
history (bursting or continuous star formation, star formation efficiency),
galaxy age, and outflow rate are chosen randomly from ranges predetermined to
be relevant. Predicted abundance ratios from each simulation are collectively
overplotted onto the data to test its viability. We present our results both
with and without observational scatter applied to the model points. Our study
shows that most trial combinations of input parameters, including a simulation
comprising only simple models with instantaneous recycling, are successful in
reproducing the observed morphology of the N/O plateau once observational
scatter is added. Therefore simulations which include delay of nitrogen
injection are no longer favored over those which propose that most nitrogen is
produced by massive stars, if only the plateau morphology is used as the
principal constraint. The one scenario which clearly cannot explain plateau
morphology is one in which galaxy ages are allowed to range below 250 Myr. We
conclude that the present data for the N/O plateau are insufficient by
themselves for identifying the portion of the stellar mass spectrum most
responsible for cosmic nitrogen production.


title: FUSE Spectroscopy of the White Dwarf in U Geminorum

abstract:
  Observations of U Gem with FUSE confirm that the WD is heated by the outburst
and cools during quiescence. At the end of an outburst, the best uniform
temperature WD model fits to the data indicate a temperature of 41,000 - 47,000
K, while in mid-quiescence, the temperature is 28,000 - 31,000 K, depending on
the gravity assumed for the WD. Photospheric abundance patterns at the end of
the outburst and in mid-quiescence show evidence of CNO processing. Improved
fits to the spectra can be obtained assuming there is a hotter, heated portion
of the WD, presumably an accretion belt, with a temperature of 60,000 - 70,000
K occupying 14-32% of the surface immediately after outburst. However, other
relatively simple models for the second component fit the data just as well and
there is no obvious signature that supports the hypothesis that the second
component arises from a separate region of the WD surface. Hence, other
physical explanations still must be considered to explain the time evolution of
the spectrum of U Gem in quiescence. Strong orbital phase dependent absorption,
most likely due to gas above the disk, was observed during the mid-quiescence
spectrum. This material, which can be modeled in terms of gas with a
temperature of 10,000-11,000 K and a density of 10**13 cm**-3, has a column
density of ~2 10**21 cm**-2 at orbital phase 0.6-0.85, and is probably the same
material that has been observed to cause dips in the lightcurve at X-ray
wavelengths in the past. The discrepancy described by Naylor et al. (2005)
between the radius of the WD derived on the one hand by the UV spectral
analysis and the distance to U Gem, and on the other, by the orbital elements
and the gravitational redshift remains a serious problem.


title: Long Gamma-Ray Burst prompt emission properties as a cosmological tool

abstract:
  Recently, a tight correlation among three quantities that characterize the
prompt emission of long Gamma-Ray Bursts (GRBs) with known redshift z, was
discovered (Firmani et al. 2006). We use this correlation to construct the
Hubble diagram (HD) with a sample of 19 GRBs in the broad range of z=0.17-4.5,
and carry out a full statistical analysis to constrain cosmological parameters
(CPs). To optimally solve the problem of circularity, a Bayesian approach is
applied. The main result is that the concordance LambdaCDM cosmology is fully
consistent with the GRB data at the level of several tests. If we assume the
Lambda cosmology, then we find Om_M=0.31^{+0.09}_{-0.08} and
Om_Lambda=0.80^{+0.20}_{-0.30}$ (1sigma); the flat-geometry case is within
1sigma. Assuming flatness, we find Om_M=0.29^{+0.08}_{-0.06}, and fixing
Om_M=0.28, we obtain a dark energy equation of state parameter
w=-1.07^{+0.25}_{-0.38}, i.e. the ambdaCDM model (w=-1) is within 1sigma. Given
the low number of usable GRBs we cannot yet constrain well the possible
evolution of w=w(z). However, the case w(z)=-1 (LambdaCDM) is consistent at the
68.3% CL with GRBs. It is shown also how a broad range of z's in the used
sample improves the determination of CPs from the HD, which is the case of GRBs
as distance indicators.


title: Remarks on Rapid vs. Slow Star Formation

abstract:
  We discuss problems with some observational estimates indicating long
protostellar core lifetimes and large stellar age spreads in molecular clouds.
We also point out some additional observational constraints which suggest that
protostellar cores do not have long lifetimes before collapsing. For external
galaxies, we argue that the widths of spiral arms does not imply a long
star-formation process, since the formation of massive stars will disrupt
molecular clouds, move material around, compress it in other regions which
produce new star-forming clouds. Thus, it seems unavoidable that this cyclical
process will result in an extended period of enhanced star formation, which
does not represent the survival time of any individual molecular cloud. We
argue that the rapid star formation indicated observationally is also easier to
understand theoretically than the traditional scenario of slow quasi-static
contraction with ambipolar diffusion.


title: Anomalies in the low CMB multipoles and extended foregrounds

abstract:
  We discuss how an extended foreground of the cosmic microwave background
(CMB) can account for the anomalies in the low multipoles of the CMB
anisotropies. The distortion needed to account for the anomalies is consistent
with a cold spot with the spatial geometry of the Local Supercluster (LSC) and
a temperature quadrupole of order DeltaT_2^2 ~ 50 microK^2. If this hypothetic
foreground is subtracted from the CMB data, the amplitude of the quadrupole
(l=2) is substantially increased, and the statistically improbable alignment of
the quadrupole with the octopole (l=3) is substantially weakened, increasing
dramatically the likelihood of the "cleaned" maps. By placing the foreground on
random locations and then computing the likelihood of the cleaned maps we can
estimate the most likely place for this foreground. Although the 1-year WMAP
data clearly points the location of this hypothetical foreground to the LSC or
its specular image (i.e., the vicinity of the poles of the cosmic dipole axis),
the three-year data seems to point to these locations as well as the north
ecliptic pole. We show that this is consistent with the symmetries of the
cosmic quadrupole. We also discuss a possible mechanism that could have
generated this foreground: the thermal Sunyaev-Zeldovich effect caused by hot
electrons in the LSC. We argue that the temperature and density of the hot gas
which are necessary to generate such an effect, though in the upper end of the
expected range of values, are marginally consistent with present observations
of the X-ray background of spectral distortions of the CMB.


title:
Common Proper Motion Search for Faint Companions Around Early-Type Field
  Stars - Progress Report - II

abstract:
  The multiplicity of early-type stars is still not well established. The
studies of individual star forming regions suggest a connection with the age
and the environment. To fill in this gap, we started the first detailed
adaptive-optic-assisted imaging survey of 308 BA-type field stars within 300 pc
from the Sun, to derive their multiplicity in a homogeneous way. Our first
epoch observations yield 195 companion candidates around 117 sample targets.
The second epoch observations are underway.


title: Constraints on Sterile Neutrino Dark Matter

abstract:
  We present a comprehensive analysis of constraints on the sterile neutrino as
a dark matter candidate. The minimal production scenario with a standard
thermal history and negligible cosmological lepton number is in conflict with
conservative radiative decay constraints from the cosmic X-ray background in
combination with stringent small-scale structure limits from the Lyman-alpha
forest. We show that entropy release through massive particle decay after
production does not alleviate these constraints. We further show that radiative
decay constraints from local group dwarf galaxies are subject to large
uncertainties in the dark matter density profile of these systems. Within the
strongest set of constraints, resonant production of cold sterile neutrino dark
matter in non-zero lepton number cosmologies remains allowed.


title:
High-Resolution Infrared Imaging of Herschel 36 SE: A Showcase for the
  Influence of Massive Stars in Cluster Environments

abstract:
  We present high-resolution infrared imaging of the massive star-forming
region around the O-star Herschel 36. Special emphasis is given to a compact
infrared source at 0".25 southeast of the star. The infrared source, hereafter
Her 36 SE, is extended in the broad-band images, but features spatially
unresolved Br gamma line emission. The line-emission source coincides in
position with the previous HST detections in H alpha and the 2 cm radio
continuum emission detected by VLA interferometry. We propose that the infrared
source Her 36 SE harbors an early B-type star, deeply embedded in a dusty
cloud. The fan shape of the cloud with Herschel 36 at its apex, though,
manifests direct and ongoing destructive influence of the O7V star on Her 36
SE.


title: X-rays from Radio Millisecond Pulsars: Comptonized Thermal Radiation

abstract:
  X-ray emission from many rotation-powered millisecond pulsars (MSPs) is
observed to be of predominantly thermal nature. In PSR J0437--4715, the nearest
MSP known, an additional faint power-law tail is observed above 2.5 keV,
commonly attributed to non-thermal magnetospheric radiation. We propose that
the hard emission in this and other similar MSPs is instead due to weak
Comptonization of the thermal (blackbody or hydrogen atmosphere) polar cap
emission by energetic electrons/positrons of small optical depth in the pulsar
magnetosphere. This spectral model implies that all soft X-rays are of purely
thermal origin, which has profound implications in the study of neutron star
structure and fundamental pulsar physics.