title:
Probing the Coevolution of Supermassive Black Holes and Galaxies Using
  Gravitationally Lensed Quasar Hosts

abstract:
  In the present-day universe, supermassive black hole masses (MBH) appear to
be strongly correlated with their galaxy's bulge luminosity, among other
properties. In this study, we explore the analogous relationship between MBH,
derived using the virial method, and the stellar R-band bulge luminosity (Lr)
or stellar bulge mass (M*) at epochs of 1 < z < 4.5 using a sample of 31
gravitationally lensed AGNs and 20 non-lensed AGNs. At redshifts z > 1.7
(10--12 Gyrs ago), we find that the observed MBH--Lr relation is nearly the
same (to within ~0.3 mag) as it is today. When the observed Lr are corrected
for luminosity evolution, this means that the black holes grew in mass faster
than their hosts, with the MBH/M* mass ratio being a factor of > 4(+2)(-1)
times larger at z > 1.7 than it is today. By the redshift range 1<z<1.7 (8-10
Gyrs ago), the MBH/M* ratio is at most two times higher than today, but it may
be consistent with no evolution. Combining the results, we conclude that the
ratio MBH/M* rises with look-back time, although it may saturate at ~6 times
the local value. Scenarios in which moderately luminous quasar hosts at z>1.7
were fully formed bulges that passively faded to the present epoch are ruled
out.


title: "Propeller" Regime of Disk Accretion to Rapidly Rotating Stars

abstract:
  We present results of axisymmetic magnetohydrodynamic simulations of the
interaction of a rapidly-rotating, magnetized star with an accretion disk. The
disk is considered to have a finite viscosity and magnetic diffusivity. The
main parameters of the system are the star's angular velocity and magnetic
moment, and the disk's viscosity, diffusivity. We focus on the "propeller"
regime where the inner radius of the disk is larger than the corotation radius.
Two types of magnetohydrodynamic flows have been found as a result of
simulations: "weak" and "strong" propellers. The strong propeller is
characterized by a powerful disk wind and a collimated magnetically dominated
outflow or jet from the star. The weak propeller have only weak outflows. We
investigated the time-averaged characteristics of the interaction between the
main elements of the system, the star, the disk, the wind from the disk, and
the jet. Rates of exchange of mass and angular momentum between the elements of
the system are derived as a function of the main parameters. The propeller
mechanism may be responsible for the fast spinning-down of the classical T
Tauri stars in the initial stages of their evolution, and for the spinning-down
of accreting millisecond pulsars.


title: Early supersymmetric cold dark matter substructure

abstract:
  Earth-mass ``microhalos'' may be the first objects to virialize in the early
universe. Their ability to survive the hierarchical clustering process as
substructure in the larger halos that form subsequently has implications for
dark matter detection experiments. We present a large N-body simulation of
early substructure in a supersymmetric cold dark matter (SUSY-CDM) scenario
characterized by an exponential cutoff in the power spectrum at M_c=10^-6 Msun.
The simulation resolves a 0.014 Msun parent ``SUSY'' halo at z=75 with 14
million particles. On these scales the effective index of the power spectrum
approaches -3, and a range of mass scales collapse almost simultaneously.
Compared to a z=0 galaxy cluster substructure within our SUSY host is less
evident both in phase-space and in physical space, and it is less resistant
against tidal disruption. As the universe expands by a factor of 1.3, we find
that between 20 and 40 percent of well-resolved SUSY substructure is destroyed,
compared to only about 1 percent in the low-redshift cluster. Nevertheless SUSY
substructure is just as abundant as in z=0 galaxy clusters, i.e. the normalized
mass and circular velocity functions are very similar. The dark matter
self-annihilation gamma-ray luminosity from bound subhalos and other deviations
from a smooth spherical configuration is at least comparable to the
spherically-averaged signal in the SUSY host, and at least three times larger
than the spherically-averaged signal in the cluster host. Such components must
be taken into account when estimating the total cosmological extragalactic
gamma-ray annihilation background.(ABRIDGED)


title:
Steps for Solving the Transfer Equation for Arbitrary Flows in
  Stationary Spacetimes

abstract:
  We derive the radiative transfer equation for arbitrary stationary
relativistic flows in stationary spacetimes, i.e. for steady-state transfer
problems. We show how the standard characteristics method of solution developed
by Mihalas and used throughout the radiative transfer community can be adapted
to multi-dimensional applications with isotropic sources. Because the
characteristics always coincide with geodesics and can always be specified by
constants, direct integration of the characteristics derived from the transfer
equation as commonly done in 1-D applications is not required. The
characteristics are known for a specified metric from the geodesics. We give
details in both flat and static spherically symmetric spacetimes. This work has
direct application in 3-dimensional simulations of supernovae, gamma-ray
bursts, and active galactic nuclei, as well as in modeling neutron star
atmospheres.


title: The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies

abstract:
  (Abridged) The ACS Virgo Cluster Survey is an HST program to obtain
high-resolution, g and z-band images for 100 early-type members of the Virgo
Cluster, spanning a range of ~460 in blue luminosity. Based on this large,
homogeneous dataset, we present a sharp upward revision in the frequency of
nucleation in early-type galaxies brighter than M_B ~ -15 (66 < f_n < 82%), and
find no evidence for nucleated dwarfs to be more concentrated to the center of
Virgo than their non-nucleated counterparts. Resolved stellar nuclei are not
present in galaxies brighter than M_B ~ -20.5, however, there is no clear
evidence from the properties of the nuclei, or from the overall incidence of
nucleation, for a change at M_B ~ -17.6, the traditional dividing point between
dwarf and giant galaxies. On average, nuclei are ~3.5 mag brighter than a
typical globular cluster and have a median half-light radius ~4.2 pc. Nuclear
luminosities correlate with nuclear sizes and, in galaxies fainter than M_B ~
-17.6, nuclear colors. Comparing the nuclei to the "nuclear clusters" found in
late-type spiral galaxies reveals a close match in terms of size, luminosity
and overall frequency, pointing to a formation mechanism that is rather
insensitive to the detailed properties of the host galaxy. The mean
nuclear-to-galaxy luminosity ratio is indistinguishable from the mean
SBH-to-bulge mass ratio, calculated in early-type galaxies with detected
supermassive black holes (SBHs). We argue that compact stellar nuclei might be
the low-mass counterparts of the SBHs detected in the bright galaxies, and that
one should think in terms of "Central Massive Objects" -- either SBHs or
compact stellar nuclei -- that accompany the formation of almost all early-type
galaxies and contain a mean fraction ~0.3% of the total bulge mass.


title: Photoevaporation of protoplanetary discs I: hydrodynamic models

abstract:
  In this paper we consider the effect of the direct ionizing stellar radiation
field on the evolution of protoplanetary discs subject to photoevaporative
winds. We suggest that models which combine viscous evolution with
photoevaporation of the disc (e.g. Clarke, Gendrin & Sotomayor 2001)
incorrectly neglect the direct field after the inner disc has drained, at late
times in the evolution. We construct models of the photoevaporative wind
produced by the direct field, first using simple analytic arguments and later
using detailed numerical hydrodynamics. We find that the wind produced by the
direct field at late times is much larger than has previously been assumed, and
we show that the mass-loss rate scales as $R_{in}^{1/2}$ (where $R_{in}$ is the
radius of the instantaneous inner disc edge). We suggest that this result has
important consequences for theories of disc evolution, and go on to consider
the effects of this result on disc evolution in detail in a companion paper
(Alexander, Clarke & Pringle 2006b).


title:
Photoevaporation of protoplanetary discs II: evolutionary models and
  observable properties

abstract:
  We present a new model for protoplanetary disc evolution. This model combines
viscous evolution with photoevaporation of the disc, in a manner similar to
Clarke, Gendrin & Sotomayor (2001). However in a companion paper (Alexander,
Clarke & Pringle 2006a) we have shown that at late times such models must
consider the effect of stellar radiation directly incident on the inner disc
edge, and here we model the observational implications of this process. We find
that the entire disc is dispersed on a time-scale of order $10^5$yr after a
disc lifetime of a few Myr, consistent with observations of T Tauri (TT) stars.
We use a simple prescription to model the spectral energy distribution of the
evolving disc, and demonstrate that the model is consistent with observational
data across a wide range of wavelengths. We note also that the model predicts a
short ``inner hole'' phase in the evolution of all TT discs, and make
predictions for future observations at mid-infrared and millimetre wavelengths.


title: Oxygen abundance in the Sloan Digital Sky Survey

abstract:
  We present two samples of $\hii$ galaxies from the Sloan Digital Sky Survey
(SDSS) spectroscopic observations data release 3. The electron
temperatures($T_e$) of 225 galaxies are calculated with the photoionized $\hii$
model and $T_e$ of 3997 galaxies are calculated with an empirical method. The
oxygen abundances from the $T_e$ methods of the two samples are determined
reliably. The oxygen abundances from a strong line metallicity indicator, such
as $R_{23}$, $P$, $N2$, and $O3N2$, are also calculated. We compared oxygen
abundances of $\hii$ galaxies obtained with the $T_e$ method, $R_{23}$ method,
$P$ method, $N2$ method, and $O3N2$method. The oxygen abundances derived with
the $T_e$ method are systematically lower by $\sim$0.2 dex than those derived
with the $R_{23}$ method, consistent with previous studies based on $\hii$
region samples. No clear offset for oxygen abundance was found between $T_e$
metallicity and $P$, $N2$ and $O3N2$ metallicity. When we studied the relation
between N/O and O/H, we found that in the metallicity regime of $\zoh > 7.95$,
the large scatter of the relation can be explained by the contribution of small
mass stars to the production of nitrogen. In the high metallicity regime, $\zoh
> 8.2$, nitrogen is primarily a secondary element produced by stars of all
masses.


title:
A Reply to a Comment on "Dark matter: A phenomenological existence
  proof"

abstract:
  In astro-ph/0601489, within the framework of the Einsteinian general
relativity, we made the observation that if the universe is described by a
spatially flat Friedmann-Robertson-Walker (FRW) cosmology with Einsteinian
cosmological constant then the resulting cosmology predicts a significant dark
matter component in the universe. Furthermore, the phenomenologically motivated
existence proof refrained from invoking the data on galactic rotational curves
and gravitational lensing, but used as input the age of the universe as
deciphered from the studies on globular clusters. This claim has been
challenged in astro-ph/0603213. Here we show that the raised objection is
invalid. It, at best, constitutes a trivial consistency check. As such, we
stand by our analysis, and by our conclusions, without reservations.


title:
The History of Cosmological Star Formation: Three Independent Approaches
  and a Critical Test Using the Extragalactic Background Light

abstract:
  Taking three independent approaches, we investigate the simultaneous
constraints set on the cosmic star formation history from various observations,
including stellar mass density and extragalactic background light (EBL). We
compare results based on: 1) direct observations of past light-cone, 2) a model
using local fossil evidence constrained by SDSS observations at z~0 (the
`Fossil' model), and 3) theoretical ab initio models from three calculations of
cosmic star formation history: (a) new (1024)^3 Total Variation Diminishing
(TVD) cosmological hydrodynamic simulation, (b) analytic expression of
Hernquist & Springel based on cosmological Smoothed Particle Hydrodynamics
(SPH) simulations, and (c) semi-analytic model of Cole et al. We find good
agreement among the three independent approaches up to the order of
observational errors, except that all the models predict bolometric EBL of
I_tot ~= 37-52 nW m^-2 sr^-1, which is at the lower edge of the the
observational estimate by Hauser & Dwek. We emphasize that the Fossil model
that consists of two components -- spheroids and disks --, when normalized to
the local observations, provides a surprisingly simple but accurate description
of the cosmic star formation history and other observable quantities. Our
analysis suggests that the consensus global parameters at z=0 are: Omega_* =
0.0023+-0.0004, I_EBL = 43+-7 nW m^-2 sr^-1 rho_SFR=(1.06+-0.22)e-2 Msun yr^-1
Mpc^-3, j_bol = (3.1+-0.2)e8 Lsun Mpc^-3.


title:
A tale of two populations: Rotating Radio Transients and X-ray Dim
  Isolated Neutron Stars

abstract:
  We highlight similarities between recently discovered Rotating Radio
Transients and X-ray Dim Isolated Neutron Stars. In particular, it is shown
that X-ray Dim Isolated Neutron Stars have a birthrate comparable to that of
Rotating Radio Transients. On the contrary, magnetars have too low a formation
rate to account for the bulk of the radio transient population. The
consequences of the recent detection of a thermal X-ray source associated with
one of the Rotating Radio Transients on the proposed scenarios for these
sources are also discussed.


title: How Long Can Tiny HI Clouds Survive?

abstract:
  We estimate the evaporation timescale for spherical HI clouds consisting of
the cold neutral medium surrounded by the warm neutral medium. We focus on
clouds smaller than 1pc, which corresponds to tiny HI clouds recently
discovered by Braun & Kanekar and Stanimirovi{\'c} & Heiles. By performing
one-dimensional spherically symmetric numerical simulations of the two-phase
interstellar medium (ISM), we derive the timescales as a function of the cloud
size and of pressure of the ambient warm medium. We find that the evaporation
timescale of the clouds of 0.01 pc is about 1Myr with standard ISM pressure,
$p/k_{B}\sim 10^{3.5}$ K cm$^{-3}$, and for clouds larger than about 0.1 pc it
depends strongly on the pressure. In high pressure cases, there exists a
critical radius for clouds growing as a function of pressure, but the minimum
critical size is $\sim$ 0.03 pc for a standard environment. If tiny HI clouds
exist ubiquitously, our analysis suggests two implications: tiny HI clouds are
formed continuously with the timescale of 1Myr, or the ambient pressure around
the clouds is much higher than the standard ISM pressure. We also find that the
results agree well with those obtained by assuming quasi-steady state
evolution. The cloud-size dependence of the timescale is well explained by an
analytic approximate formula derived by Nagashima, Koyama & Inutsuka. We also
compare it with the evaporation rate given by McKee & Cowie.


title:
Calibration of the Mass-Temperature Relation for Clusters of Galaxies
  Using Weak Gravitational Lensing

abstract:
  The main uncertainty in current determinations of the power spectrum
normalization, sigma_8, from abundances of X-ray luminous galaxy clusters
arises from the calibration of the mass-temperature relation. We use our weak
lensing mass determinations of 30 clusters from the hitherto largest sample of
clusters with lensing masses, combined with X-ray temperature data from the
literature, to calibrate the normalization of this relation at a temperature of
8 keV, M_{500c,8 keV}=(8.7 +/- 1.6) h^{-1} 10^{14} M_sun. This normalization is
consistent with previous lensing-based results based on smaller cluster
samples, and with some predictions from numerical simulations, but higher than
most normalizations based on X-ray derived cluster masses. Assuming the
theoretically expected slope alpha=3/2 of the mass-temperature relation, we
derive sigma_8 = 0.88 +/-0.09 for a spatially-flat LambdaCDM universe with
Omega_m = 0.3. The main systematic errors on the lensing masses result from
extrapolating the cluster masses beyond the field-of-view used for the
gravitational lensing measurements, and from the separation of
cluster/background galaxies, contributing each with a scatter of 20%. Taking
this into account, there is still significant intrinsic scatter in the
mass-temperature relation indicating that this relation may not be very tight,
at least at the high mass end. Furthermore, we find that dynamically relaxed
clusters are 75 +/-40% hotter than non-relaxed clusters.


title: Metals and dust in high redshift AGNs

abstract:
  We summarize some recent results on the metallicity and dust properties of
Active Galactic Nuclei (AGN) at high redshift (1<z<6.4). By using the spectra
of more than 5000 QSOs from the SDSS we find no evidence for any metallicity
evolution in the redshift range 2<z<4.5, while there is a significant
luminosity-metallicity dependence. These results are confirmed by the spectra
of a smaller sample of narrow line AGNs at high-z (QSO2s and radio galaxies).
The lack of metallicity evolution is interpreted both as a consequence of the
cosmic downsizing and as a selection effect resulting from the joint QSO-galaxy
evolution. The luminosity-metallicity relation is interpreted as a consequence
of the mass-metallicity relation in the host galaxies of QSOs, but a
relationship with the accretion rate is also possible. The lack of metallicity
evolution is observed even in the spectra of the most distant QSOs known (z~6).
This result is particularly surprising for elements such as Fe, C and Si, which
are subject to a delayed enrichment, and requires that the hosts of these QSOs
formed in short bursts and at very high redshift (z>10). The properties of dust
in high-z QSOs are discussed within the context of the dust production
mechanisms in the early universe. The dust extinction curve is observed to
evolve beyond z>4, and by z~6 it is well described by the properties expected
for dust produced by SNe, suggesting that the latter is the main mechanism of
dust production in the early universe. We also show that the huge dust masses
observed in distant QSOs can be accounted for by SN dust within the
observational constraints currently available. Finally, we show that QSO winds,
which have been proposed as an alternative mechanism of dust production, may
also contribute significantly to the total dust budget at high redshift.


title: Circumstellar discs in the young sigma Orionis cluster

abstract:
  We present new K- and L'-band imaging observations for members of the young
(3-5 Myr) sigma Orionis cluster, obtained with UIST at UKIRT. We determine
(K-L') colour excesses with respect to the photospheres, finding evidence for
warm circumstellar dust around 27 out of 83 cluster members that have masses
between 0.04 Msun and 1.0 Msun. This indicates a circumstellar disc frequency
of at least (33 +/- 6)% for this cluster, consistent with previous
determinations from smaller samples (Oliveira et al. 2004) and also consistent
with the 3 Myr disc half-life suggested by Haisch et al. (2001). There is
marginal evidence that the disc frequency declines towards lower masses, but
the data are also consistent with no mass-dependence at all. There is no
evidence for spatial segregation of objects with and without circumstellar
discs.


title: Constrain intergalactic medium from the SZ effect map

abstract:
  In this paper, we try to detect the SZ effect in the 2MASS DWT clusters and
less bound objects in order to constrain the warm-hot intergalactic medium
distribution on large scales by cross-correlation analysis. The results of both
observed WMAP and mock SZ effect map indicate that the hot gas distributes from
inside as well as outside of the high density regions of galaxy clusters, which
is consistent with the results of both observation and hydro simulation.
Therefore, the DWT measurement of the cross-correlation would be a powerful
tool to probe the missing of baryons in the Universe.


title: High resolution optical spectroscopy of IRAS 09425-6040 (=GLMP 260)

abstract:
  We present high resolution optical spectroscopic observations of IRAS
09425-6040, a peculiar, extremely red, C-rich AGB star showing prominent O-rich
dust features in its ISO infrared spectrum attributed to crystalline silicates.
Our analysis shows that IRAS 09425-6040 is indeed a C-rich star slightly
enriched in lithium (log (Li/H) + 12 ~ 0.7) with a low 12C/13C = 15+-6 ratio.
We also found some evidence that it may be enriched in s-elements. Combining
our results with other observational data taken from the literature we conclude
that the star is possibly an intermediate-mass TP-AGB star (M > 3 M_sun) close
to the end of its AGB evolution which may have only very recently experienced a
radical change in its chemistry, turning into a carbon-rich AGB star.


title:
Interferometric Parallax: A Method for Measurement of Astronomical
  Distances

abstract:
  We show that distances of objects at cosmological distances can be measured
directly using interferometry. Our approach to interferometric parallax comes
from analysis of 4-point amplitude and intensity correlations that can be
generated from pairs of well-separated detectors. The baseline required to
measure cosmological distances of Gigaparsec order are within the reach of the
next generation of space-borne detectors. The semi-classical interpretation of
intensity correlations uses a notion of a single photon taking two paths
simultaneously. Semi-classically a single photon can simultaneously enter four
detectors separated by an astronomical unit, developing correlations feasible
to measure with current technology.


title: On horizons and the cosmic landscape

abstract:
  Susskind claims in his recent book The Cosmic Landscape that evidence for the
existence and nature of `pocket universes' in a multiverse would be available
in the detailed nature of the Cosmic Blackbody Background Radiation that
constantly bathes all parts of our observable universe. I point out that
acceptance of the complex chain of argument involved does not imply possible
experimental verification of multiverses at the present time. Rather this claim
relates only to theoretically possible observations in the very far future of
the universe.


title: The masses of PSR J1911-5958A and its white dwarf companion

abstract:
  We present spectroscopic and photometric observations of the optical
counterpart to PSR J1911-5958A, a millisecond pulsar located towards the
globular cluster NGC 6752. We measure radial velocities from the spectra and
determine the systemic radial velocity of the binary and the radial-velocity
amplitude of the white-dwarf orbit. Combined with the pulsar orbit obtained
from radio timing, we infer a mass ratio of Mpsr/Mwd=7.36+-0.25. The spectrum
of the counterpart is that of a hydrogen atmosphere, showing Balmer absorption
lines upto H12, and we identify the counterpart as a helium-core white dwarf of
spectral type DA5. Comparison of the spectra with hydrogen atmosphere models
yield a temperature Teff=10090+-150 K and a surface gravity log g=6.44+-0.20 cm
s^-2. Using mass-radius relations appropriate for low-mass helium-core white
dwarfs, we infer the white-dwarf mass Mwd=0.18+-0.02 Msun and radius
Rwd=0.043+-0.009 Rsun. Combined with the mass ratio, this constrains the pulsar
mass to Mpsr=1.40^+0.16_-0.10 Msun. If we instead use the white-dwarf spectrum
and the distance of NGC 6752 to determine the white-dwarf radius, we find
Rwd=0.058+-0.004 Rsun. For the observed temperature, the mass-radius relations
predict a white-dwarf mass of Mwd=0.175+-0.010 Msun, constraining the pulsar
mass to Mpsr=1.34+-0.08 Msun. We find that the white-dwarf radius determined
from the spectrum and the systemic radial velocity of the binary are only
marginally consistent with the values that are expected if PSR J1911-5958A is
associated with NGC 6752. We discuss possible causes to explain this
inconsistency, but conclude that our observations do not conclusively confirm
nor disprove the assocation of the pulsar binary with the globular cluster.


title:
XMM-Newton observations of a sample of gamma-ray loud active galactic
  nuclei

abstract:
  (abridged) We performed a homogeneous and systematic analysis of simultaneous
X-ray and optical/UV properties of a group of 15 gamma-ray loud AGN, using
observations performed with XMM-Newton. The sample is composed of 13 blazars (6
BL Lac and 7 Flat-Spectrum Radio Quasar) and 2 radio galaxies, that are
associated with detections at energies >100 MeV. The data for 7 of them are
analyzed here for the first time, including the first X-ray observation of PKS
1406-706. Then, the spectral characteristics of the sources in the present
sample have been compared with those in previous catalogs of blazars and other
AGN, in order to search for any difference or long term change. All the
selected sources appear to follow the classic "blazar sequence" and the
spectral energy distributions (SED) built with the present X-ray and optical/UV
data and completed with historical data, confirm the findings of previous
studies on this type of sources. Some sources display interesting features
worth noting: four of them, namely AO 0235+164, PKS 1127-145, S5 0836+710 and
PKS 1830-211 show the presence of an intervening absorption system along the
line of sight, but only the latter is known to be surely gravitationally
lensed. AO 0235+164 was detected during an outburst and its SED shows a clear
shift of the synchrotron peak. 3C 273 shows a change in the state with respect
to the previous BeppoSAX observations, that can be interpreted as an increase
of the Seyfert-like component and a corresponding decline of the jet emission.
This is consistent with the monitoring at radio wavelengths performed during
the same years. PKS 1406-706 is detected with a flux higher than in the past,
but with a corresponding low optical flux. Moreover, although it is classified
as FSRQ, the SED can be modelled with a simple synchrotron self-Compton model.


title:
The puzzling properties of the Helium White Dwarf orbiting the
  millisecond pulsar PSR J1911-5958A in NGC 6752

abstract:
  We have used phase-resolved high-resolution images and low resolution spectra
taken at the ESO Very Large Telescope, to study the properties of the low-mass
Helium White Dwarf companion to the millisecond pulsar \psr (hereafter COM
J1911$-$5958A), in the halo of the Galactic Globular Cluster NGC 6752. The
radial velocity curve confirms that \com is orbiting the pulsar and allows to
derive a systemic velocity of the binary system nicely in agreement with that
of NGC 6752. This strongly indicates that the system is a member of the
cluster, despite its very offset position ($\sim 74$ core radii) with respect
to the core. Constraints on the orbital inclination ($\gapp 70^\circ$) and
pulsar mass ($1.2-1.5 {\rm M_\odot}$) are derived from the mass ratio
$M_{PSR}/M_{COM}= 7.49\pm0.64$ and photometric properties of COM J1911$-$5958A.
The light curve in B-band shows two phases of unequal brightening
($\Delta$mag$\sim 0.3$ and 0.2, respectively) located close to quadratures and
superimposed on an almost steady baseline emission: this feature is quite
surprising and needs to be further investigated.


title:
Metal Enrichment of the ICM: a 3-D Picture of Chemical and Dynamical
  Properties

abstract:
  We develop a model for the metal enrichment of the intracluster medium (ICM)
that combines a cosmological non-radiative hydrodynamical N-Body/SPH simulation
of a cluster of galaxies, and a semi-analytic model of galaxy formation. The
novel feature of our hybrid model is that the chemical properties of the
diffuse gas in the underlying simulation are dynamically and consistently
generated from stars in the galaxies. We follow the production of several
chemical elements, provided by low- and intermediate-mass stars, core collapse
and type Ia supernovae. We analyse the spatial distribution of metals in the
ICM, investigate the way in which the chemical enrichment proceeds, and use
iron emissivity as a tracer of gas motions. Fe and O radial abundance profiles
are enhanced in the inner 100 h^-1 kpc in the last Gyr because of the
convergence of enriched gas clumps to the cluster centre. Our results support a
scenario in which part of the central intracluster gas comes from gas clumps
that, in the redshift range of z~0.2 to ~0.5, have been enriched to solar
values and are at large distances from the cluster centre (from ~1 to ~6 h^-1
Mpc) moving at very high velocities (from ~1300 to ~2500 km s^-1). The
turbulent gas motions within the cluster, originated in the inhomogeneous gas
infall during the cluster assembly, are manifested in emission-weighted
velocity maps as gradients that can be as large as ~1000 km s^-1 over distances
of a few hundred kpc. Gradients of this magnitude are also seen in velocity
distributions along sightlines through the cluster centre. Doppler shifting and
broadening suffered by the Fe K 6.7 keV emission line along such sightlines
could be used to probe these gas large-scale motions when they are produced
within an area characterised by high iron line emissivity.


title:
Probing the Universe on Gigaparsec Scales with Remote Cosmic Microwave
  Background Quadrupole Measurements

abstract:
  Scattering of cosmic microwave background (CMB) radiation in galaxy clusters
induces a polarization signal proportional to the CMB quadrupole anisotropy at
the cluster's location and look-back time. A survey of such remote quadrupole
measurements provides information about large-scale cosmological perturbations.
This paper presents a formalism for calculating the correlation function of
remote quadrupole measurements in spherical harmonic space. The number of
independent modes probed by both single-redshift and volume-limited surveys is
presented, along with the length scales probed by these modes. In a remote
quadrupole survey sparsely covering a large area of sky, the largest-scale
modes probe the same length scales as the quadrupole but with much narrower
Fourier-space window functions. The largest-scale modes are significantly
correlated with the local CMB, but even when this correlation is projected out
the largest remaining modes probe gigaparsec scales (comparable to the CMB at
l=2-10) with narrow window functions. These modes may provide insight into the
possible anomalies in the large-scale CMB anisotropy. At fixed redshift, the
data from such a survey form an E-type spin-2 field on the sphere to a good
approximation; the near-absence of B modes will provide a valuable check on
systematic errors. A survey of only a few low-redshift clusters allows an
independent reconstruction of the five coefficients of the local CMB
quadrupole, providing a test for contamination in the WMAP quadrupole. The
formalism presented here is also useful for analyzing smaller-scale surveys to
probe the late integrated Sachs-Wolfe effect and hence the properties of dark
energy


title:
X-ray Detection of the Proto Supermassive Binary Black Hole at the
  Centre of Abell 400

abstract:
  We report the first X-ray detection of a proto-supermassive binary black hole
at the centre of Abell 400. Using the Chandra ACIS, we are able to clearly
resolve the two active galactic nuclei in 3C 75, the well known double radio
source at the centre of Abell 400. Through analysis of the new Chandra
observation of Abell 400 along with 4.5 GHz and 330 MHz VLA radio data, we will
show new evidence that the Active Galactic Nuclei in 3C 75 are a bound system.
Methods. Using the high quality X-ray data, we map the temperature, pressure,
density, and entropy of the inner regions as well as the cluster profile
properties out to ~18'. We compare features in the X-ray and radio images to
determine the interaction between the intra-cluster medium and extended radio
emission. The Chandra image shows an elongation of the cluster gas along the
northeast-southwest axis; aligned with the initial bending of 3C 75's jets.
Additionally, the temperature profile shows no cooling core, consistent with a
merging system. There is an apparent shock to the south of the core consistent
with a Mach number of M~1.4 or speed of v~1200 km s^-1. Both Active Galactic
Nuclei, at least in projection, are located in the low entropy, high density
core just north of the shock region. We find that the projected path of the
jets does not follow the intra-cluster medium surface brightness gradient as
expected if their path were due to buoyancy. We also find that both central AGN
are extended and include a thermal component. Based on this analysis, we
conclude that the Active Galactic Nuclei in 3C 75 are a bound system from a
previous merger. They are contained in a low entropy core moving through the
intra-cluster medium at 1200 km s^-1. The bending of the jets is due to the
local intra-cluster medium wind.


title: Geometry of giant star model atmospheres: A consistency test

abstract:
  We investigate the effect of a geometric inconsistency in the calculation of
synthetic spectra of giant stars. Spectra computed with model atmospheres
calculated in spherical geometry while using the plane-parallel approximation
for line formation calculations (s_p), as well as the fully plane-parallel case
(p_p), are compared to the consistently spherical case (s_s). We present
abundance differences for solar metallicity models with Teff ranging from 4000
to 6500 K and logg from 0.5 to 3.0 [cgs]. The effects are smaller for s_p
calculations (-0.1 dex in the worst case) than for the p_p case (up to +0.35
dex for minority species and at most -0.04 dex for majority species), both with
respect to the s_s case. In the s_p case the differences increase slightly with
temperature, while in the p_p case they show a more complex behaviour. In both
cases the effects decrease with increasing logg and increase with equivalent
width. Thus, within the parameter range of F, G and K giants, consistency seems
to be less important than using a spherical model atmosphere. The abundance
differences due to sphericity effects presented here can be used for error
estimation in abundance studies relying on plane-parallel modelling.


title:
Properties of the $\delta$ Scorpii Circumstellar Disk from Continuum
  Modeling

abstract:
  We present optical $WBVR$ and infrared $JHKL$ photometric observations of the
Be binary system $\delta$ Sco, obtained in 2000--2005, mid-infrared (10 and $18
\mu$m) photometry and optical ($\lambda\lambda$ 3200--10500 \AA)
spectropolarimetry obtained in 2001. Our optical photometry confirms the
results of much more frequent visual monitoring of $\delta$ Sco. In 2005, we
detected a significant decrease in the object's brightness, both in optical and
near-infrared brightness, which is associated with a continuous rise in the
hydrogen line strenghts. We discuss possible causes for this phenomenon, which
is difficult to explain in view of current models of Be star disks. The 2001
spectral energy distribution and polarization are succesfully modeled with a
three-dimensional non-LTE Monte Carlo code which produces a self-consistent
determination of the hydrogen level populations, electron temperature, and gas
density for hot star disks. Our disk model is hydrostatically supported in the
vertical direction and radially controlled by viscosity. Such a disk model has,
essentially, only two free parameters, viz., the equatorial mass loss rate and
the disk outer radius. We find that the primary companion is surrounded by a
small (7 $R_\star$), geometrically-thin disk, which is highly non-isothermal
and fully ionized. Our model requires an average equatorial mass loss rate of
$1.5\times 10^{-9} M_{\sun}$ yr$^{-1}$.


title:
X-ray properties in massive galaxy clusters: XMM-Newton observations of
  the REFLEX-DXL sample

abstract:
  We selected an unbiased, flux-limited and almost volume-complete sample of 13
distant, X-ray luminous (DXL, $z\sim 0.3$) clusters and one supplementary
cluster at $z=0.2578$ from the REFLEX Survey (the REFLEX-DXL sample). We
performed a detailed study to explore their X-ray properties using XMM-Newton
observations. Based on the precise radial distributions of the gas density and
temperature, we obtained robust cluster masses and gas mass fractions. The
average gas mass fraction of the REFLEX-DXL sample at $r_{500}$, $0.116 \pm
0.007$, agrees with the previous cluster studies and the WMAP baryon fraction
measurement. The scaled profiles of the surface brightness, temperature,
entropy, gas mass and total mass are characterized by a self-similar behaviour
at radii above 0.2--0.3 $r_{500}$. The REFLEX-DXL sample confirms the previous
studies of the normalization of the scaling relations ($L$--$T$, $L$--$M$,
$M$--$T$ and $M_{\rm gas}$--$T$) when the redshift evolution of the scaling
relations is accounted for. We investigated the scatter of the scaling
relations of the REFLEX-DXL sample. This gives the correlative scatter of
(0.20,0.10) for variable of ($M$,$T$) of the $M_{500}$--$T$ relation, for
example.


title: Microlens OGLE-2005-BLG-169 Implies Cool Neptune-Like Planets are Common

abstract:
  We detect a Neptune mass-ratio (q~8e-5) planetary companion to the lens star
in the extremely high-magnification (A~800) microlensing event
OGLE-2005-BLG-169. If the parent is a main-sequence star, it has mass M~0.5
M_sun implying a planet mass of ~13 M_earth and projected separation of ~2.7
AU. When intensely monitored over their peak, high-magnification events similar
to OGLE-2005-BLG-169 have nearly complete sensitivity to Neptune mass-ratio
planets with projected separations of 0.6 to 1.6 Einstein radii, corresponding
to 1.6--4.3 AU in the present case. Only two other such events were monitored
well enough to detect Neptunes, and so this detection by itself suggests that
Neptune mass-ratio planets are common. Moreover, another Neptune was recently
discovered at a similar distance from its parent star in a low-magnification
event, which are more common but are individually much less sensitive to
planets. Combining the two detections yields 90% upper and lower frequency
limits f=0.37^{+0.30}_{-0.21} over just 0.4 decades of planet-star separation.
In particular, f>16% at 90% confidence. The parent star hosts no Jupiter-mass
companions with projected separations within a factor 5 of that of the detected
planet. The lens-source relative proper motion is \mu~7--10 mas/yr, implying
that if the lens is sufficiently bright, I<23.8, it will be detectable by HST
by 3 years after peak. This would permit a more precise estimate of the lens
mass and distance, and so the mass and projected separation of the planet.
Analogs of OGLE-2005-BLG-169Lb orbiting nearby stars would be difficult to
detect by other methods of planet detection, including radial velocities,
transits, or astrometry.


title:
General Relativistic Binary Merger Simulations and Short Gamma Ray
  Bursts

abstract:
  The recent localization of some short-hard gamma ray bursts (GRBs) in
galaxies with low star formation rates has lent support to the suggestion that
these events result from compact object binary mergers. We discuss how new
simulations in general relativity are helping to identify the central engine of
short-hard GRBs. Motivated by our latest relativistic black hole-neutron star
merger calculations, we discuss a scenario in which these events may trigger
short-hard GRBs, and compare this model to competing relativistic models
involving binary neutron star mergers and the delayed collapse of hypermassive
neutron stars. Distinguishing features of these models may help guide future
GRB and gravitational wave observations to identify the nature of the sources.


title: Equilibrium Star Cluster Formation

abstract:
  We argue that rich star clusters take at least several local dynamical times
to form, and so are quasi-equilibrium structures during their assembly.
Observations supporting this conclusion include morphologies of star-forming
clumps, momentum flux of protostellar outflows from forming clusters, age
spreads of stars in the Orion Nebula Cluster (ONC) and other clusters, and the
age of a dynamical ejection event from the ONC. We show that these long
formation timescales are consistent with the expected star formation rate in
turbulent gas, as recently evaluated by Krumholz & McKee. Finally, we discuss
the implications of these timescales for star formation efficiencies, the
disruption of gas by stellar feedback, mass segregation of stars, and the
longevity of turbulence in molecular clumps.


title: The shock break-out of GRB 060218/SN 2006aj

abstract:
  Although the link between long Gamma Ray Bursts (GRBs) and supernovae (SNe)
has been established, hitherto there have been no observations of the beginning
of a supernova explosion and its intimate link to a GRB. In particular, we do
not know however how a GRB jet emerges from the star surface nor how a GRB
progenitor explodes. Here we report on observations of the close GRB060218 and
its connection to SN2006aj. In addition to the classical non-thermal emission,
GRB060218 shows a thermal component in its X-ray spectrum, which cools and
shifts into the optical/UV band as time passes. We interpret these features as
arising from the break out of a shock driven by a mildly relativistic shell
into the dense wind surrounding the progenitor. Our observations allow us for
the first time to catch a SN in the act of exploding, to directly observe the
shock break-out and to provide strong evidence that the GRB progenitor was a
Wolf-Rayet star.


title: Stellar remnants in galactic nuclei: mass segregation

abstract:
  The study of how stars distribute themselves around a massive black hole
(MBH) in the center of a galaxy is an important prerequisite for the
understanding of many galactic-center processes. These include the observed
overabundance of point X-ray sources at the Galactic center, the prediction of
rates and characteristics of tidal disruptions of extended stars by the MBH and
of inspirals of compact stars into the MBH, the latter being events of high
importance for the future space borne gravitational wave interferometer LISA.
In relatively small galactic nuclei, hosting MBHs with masses in the range
10^5-10^7 Msun, the single most important dynamical process is 2-body
relaxation. It induces the formation of a steep density cusp around the MBH and
strong mass segregation, as more massive stars lose energy to lighter ones and
drift to the central regions. Using a spherical stellar dynamical Monte-Carlo
code, we simulate the long-term relaxational evolution of galactic nucleus
models with a spectrum of stellar masses. Our focus is the concentration of
stellar black holes to the immediate vicinity of the MBH. We quantify this mass
segregation for a variety of galactic nucleus models and discuss its
astrophysical implications. Special attention is given to models developed to
match the conditions in the Milky Way nucleus; we examine the presence of
compact objects in connection to recent high-resolution X-ray observations.


title: The non-linear behavior of the black hole system GRS 1915+105

abstract:
  Using non-linear time series analysis, along with surrogate data analysis, it
is shown that the various types of long term variability exhibited by the black
hole system GRS 1915+105, can be explained in terms of a deterministic
non-linear system with some inherent stochastic noise. Evidence is provided for
a non-linear limit cycle origin of one of the low frequency QPO detected in the
source, while some other types of variability could be due to an underlying low
dimensional chaotic system. These results imply that the partial differential
equations which govern the magneto-hydrodynamic flow of the inner accretion
disk, can be approximated by a small number ($\approx 3 -5$) of non-linear but
{\it ordinary} differential equations. While this analysis does not reveal the
exact nature of these approximate equations, they may be obtained in the
future, after results of magneto-hydrodynamic simulation of realistic accretion
disks become available.


title: The faint afterglow and host galaxy of the short-hard GRB 060121

abstract:
  We present optical and X-ray observations of the afterglow and host galaxy of
the short-hard GRB 060121. The faint R-band afterglow is seen to decline as
t^(-0.66) while the X-ray falls as t^-1.18, indicating the presence of the
cooling break between the two frequencies. However, the R-band afterglow is
very faint compared to the predicted extrapolation of the X-ray afterglow to
the optical regime (specifically, beta_OX ~ 0.2), while the K-band is
consistent with this extrapolation (beta_KX ~ 0.6), demonstrating suppression
of the optical flux. Late time {\it HST} observations place stringent limits on
the afterglow R-band flux implying a break in the R-band lightcurve. They also
show that the burst occurred at the edge of a faint red galaxy which most
likely lies at a significantly higher redshift than the previous optically
identified short-duration bursts. Several neighboring galaxies also have very
red colors that are similarly suggestive of higher redshift. We consider
possible explanations for the faintness and color of the burst. Our preferred
model is that the burst occurred at moderately high redshift and was
significantly obscured; however, it is also possible that the burst lies at z >
4.5 in which case the faintness of the R-band afterglow could be attributed to
the Lyman-break. We discuss the implications that either scenario would have
for the nature of the progenitors of short bursts.


title: On the Disalignment of Interstellar Grains

abstract:
  Several mechanisms have been proposed to explain the alignment of grains with
the interstellar magnetic field, including paramagnetic dissipation, radiative
torques, and supersonic gas-grain streaming. These must compete with
disaligning processes, including randomly directed torques arising from
collisions with gas atoms. I describe a novel disalignment mechanism for grains
that have a time-varying electric dipole moment and that drift across the
magnetic field. Depending on the drift speed, this mechanism may yield a much
shorter disalignment timescale than that associated with random gas atom
impacts. For suprathermally rotating grains, the new disaligning process may be
more potent for carbonaceous dust than for silicate dust. This could result in
efficient alignment for silicate grains but poor alignment for carbonaceous
grains.


title: Constraining the GRB Collimation with a Survey for Orphan Afterglows

abstract:
  Gamma-ray bursts are believed to be produced in highly-relativistic
collimated outflows. Support for this comes among others from the association
of the times of detected breaks in the decay of afterglow light curves with the
collimation angle of the jets. An alternative approach to estimate a limit on
the collimation angle uses GRB afterglows without detected prompt-emission
counterparts. Here we report on the analysis of a dedicated survey for the
search of these orphan afterglows using the Wide Field Imager at the 2.2m
MPI/ESO telescope at La Silla, Chile. We monitored ~12 square degrees. in up to
25 nights typically spaced by one to two nights with a limiting magnitude of
R=23. Four previously unknown optical transients were discovered and three of
these associated with a flare star, a cataclysmic variable and a dwarf nova.
The fourth source shows indications for an extragalactic origin but the sparse
sampling of the light curve prevents a reliable classification. We discuss the
results in the context of the collimation of GRBs.


title:
Sources of Radiation in the Early Universe: The Equation of Radiative
  Transfer and Optical Distances

abstract:
  We have derived the radiative-transfer equation for a point source with a
specified intensity and spectrum, originating in the early Universe between the
epochs of annihilation and recombination, at redshifts $z_\s =10^8\div 10^4$.
The direct radiation of the source is separated from the diffuse radiation it
produces. Optical distances from the source for Thomson scattering and
bremsstrahlung absorption at the maximum of the thermal background radiation
are calculated as a function of the redshift z.The distances grow sharply with
decreasing z, approaching asymptotic values, the absorption distance increasing
more slowly and reaching their limiting values at lower z. For the adopted z
values, the optical parameters of the Universe can be described in a flat model
with dusty material and radiation, and radiative transfer can be treated in a
grey approximation.


title: High resolution X-ray spectroscopy of bright O type stars

abstract:
  Archival X-ray spectra of the four prominent single, non-magnetic O stars
Zeta Pup, Zeta Ori, Ksi Per and Zeta Oph, obtained in high resolution with
Chandra HETGS/MEG have been studied. The resolved X-ray emission line profiles
provide information about the shocked, hot gas which emits the X-radiation, and
about the bulk of comparably cool stellar wind material which partly absorbs
this radiation. In this paper, we synthesize X-ray line profiles with a model
of a clumpy stellar wind. We find that the geometrical shape of the wind
inhomogeneities is important: better agreement with the observations can be
achieved with radially compressed clumps than with spherical clumps. The
parameters of the model, i.e. chemical abundances, stellar radius, mass-loss
rate and terminal wind velocity, are taken from existing analyses of UV and
optical spectra of the programme stars. On this basis, we also calculate the
continuum-absorption coefficient of the cool-wind material, using the Potsdam
Wolf-Rayet (PoWR) model atmosphere code. The radial location of X-ray emitting
gas is restricted from analysing the fir line ratios of helium-like ions. The
only remaining free parameter of our model is the typical distance between the
clumps; here, we assume that at any point in the wind there is one clump
passing by per one dynamical time-scale of the wind. The total emission in a
model line is scaled to the observation. There is a good agreement between
synthetic and observed line profiles. We conclude that the X-ray emission line
profiles in O stars can be explained by hot plasma embedded in a cool wind
which is highly clumped in the form of radially compressed shell fragments.


title:
The Virgo CO Survey: VI. Gas Dynamics and Star Formation Along the Bar
  in NGC 4303

abstract:
  We present CO interferometer observations of the barred galaxy NGC 4303
(M61). This galaxy has a gas concentration at the central region and offset
ridges in the bar. Sharp velocity gradients are apparent across the ridges.
Analyses of the CO data and the newborn stellar clusters revealed in HST images
indicate the existence of unresolved molecular clouds with masses of
10^4-6Msun. The observed shear velocity gradient across the ridges is too small
to break up giant molecular clouds. Therefore, the clouds are likely to survive
passage through the ridges. We discuss a cloud orbit model in a bar potential.
The model reproduces the narrow offset ridges and sharp velocity gradients
across the ridges in NGC 4303. We discuss cloud-cloud collisions (and close
interactions) as a possible triggering mechanism for star formation. The
newborn stellar clusters in NGC 4303 are located predominantly at the leading
sides of the offset ridges, where cloud orbits are densely populated and
suggest a high collisional frequency and possibly a high rate of triggered star
formation. Cloud-based dynamics is less dissipative than smooth hydrodynamic
models, possibly extending the timescales of gas dynamical evolution and gas
fueling to central regions in barred galaxies.


title: Restoring Color-magnitude Diagrams with the Richardson-Lucy Algorithm

abstract:
  We present an application of the Richardson-Lucy algorithm to the analysis of
color-magnitude diagrams by converting the CMD into an image and using a
restoring point spread function function ({\it psf}) derived from the known,
often complex, sources of error. We show numerical experiments that demonstrate
good recovery of the original image and establish convergence rates for ideal
cases with single gaussian uncertainties and poisson noise using a $\chi^2$
statistic. About 30-50 iterations suffice. As an application, we show the
results for a particular case, the Hipparcos sample of the solar neighborhood
where the uncertainties are mainly due to parallax which we model with a
composite weighted gaussian using the observed error distributions. The
resulting psf has a slightly narrower core and broader wings than a single
gaussian. The reddening and photometric errors are considerably reduced by
restricting the sample to within 80 pc and to M_V \leq 3.5. We find that the
recovered image, which has a narrower, better defined main sequence and a more
clearly defined red giant clump, can be used as input to stellar evolution
modeling of the star formation rate in the solar vicinity and, with more
contributing uncertainties taken into account, for general Galactic and
extragalactic structure and population studies.


title: Hidden invariance in Gurzadyan-Xue cosmological models

abstract:
  The dark energy formula derived by Gurzadyan and Xue which leads to a value
fitting the SN data, provides a scaling relation between the physical constants
and cosmological parameters and defines a set of cosmological models. In
previous works we have considered several of those models and derived the
cosmological equations for each case. In this letter, we present the phase
portrait analysis of those models. Surprisingly we found, first, that the
separatrix in the phase space which determines the character of solutions
depends solely on the value of the current matter density. Namely, at
$\Omega_m>2/3$ the equations describe Friedmannian Universe with the classical
singularity at the beginning. While at $\Omega_m<2/3$ all solutions for all
models start with zero density and non vanishing scale factor. Secondly, more
remarkable, the value $\Omega_{sep}=2/3$ defining the separatrix is the same
for all models, which reveales an underlying invariance hidden in the models,
possibly, due to the basic nature of the GX-scaling.


title:
First Detection of NaI D lines in High-Redshift Damped Lyman-alpha
  Systems

abstract:
  A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the
gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on
the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897
doublet absorption in high-redshift DLAs at z=1.062 and 1.181, confirming the
presence of NaI, which was first reported for the rest-frame UV NaI
3303.3,3303.9 doublet by Petitjean et al. This is the first detection of NaI D
absorption in a high-redshift (z>1) DLA. In addition, we detected a new NaI
component in the z=1.062 DLA and four new components in the z=1.181 DLA. Using
an empirical relationship between NaI and HI column density, we found that all
"components" have large HI column density, so that each component is classified
as DLA absorption. We also detected strong NaI D absorption associated with a
MgII system at z=1.173. Because no other metal absorption lines were detected
in this system at the velocity of the NaI absorption in previously reported
optical spectra (observed 3.6 years ago), we interpret this NaI absorption
cloud probably appeared in the line of sight toward the QSO after the optical
observation. This newly found cloud is likely to be a DLA based upon its large
estimated HI column density. We found that the N(NaI)/N(CaII) ratios in these
DLAs are systematically smaller than those observed in the Galaxy; they are
more consistent with the ratios seen in the Large Magellanic Cloud. This is
consistent with dust depletion generally being smaller in lower metallicity
environments. However, all five clouds of the z=1.181 system have a high
N(NaI)/N(CaII) ratio, which is characteristic of cold dense gas. We tentatively
suggest that the host galaxy of this system may be the most significant
contributor to the gravitational-lens toward APM 08279+5255.


title: Refined parameters of the planet orbiting HD 189733

abstract:
  We report on the BVRI multi-band follow-up photometry of the transiting
extrasolar planet HD 189733b. We revise the transit parameters and find
planetary radius RP = 1.154+/- 0.032RJ and inclination i_P = 85.79+/-0.24deg.
The new density (~ 1g cm-3) is significantly higher than the former estimate (~
0.75g cm-3); this shows that from the current sample of 9 transiting planets,
only HD 209458 (and possibly OGLE-10b) have anomalously large radii and low
densities. We note that due to the proximity of the parent star, HD 189733b
currently has one of the most precise radius determinations among extrasolar
planets. We calculate new ephemerides: P = 2.218573+/-0.000020 days, T0 =
2453629.39420+/-0.00024 (HJD), and estimate the timing offsets of the 11
distinct transits with respect to the predictions of a constant orbital period,
which can be used to reveal the presence of additional planets in the system.


title: II Zwicky 23 and Family

abstract:
  II Zwicky 23 (UGC 3179) is a luminous, nearby compact narrow emission line
starburst galaxy with blue optical colors and strong emission lines. We present
a photometric and morphological study of II Zw 23 and its interacting
companions using data obtained with the WIYN 3.5-m telescope in Kitt Peak,
Arizona. II Zwicky 23 has a highly disturbed outer structure with long trails
of debris that may be feeding tidal dwarfs. Its central regions appear disky, a
structure that is consistent with the overall rotation pattern observed in the
H-alpha velocity field measured from Densepak observations obtained with WIYN.
We discuss the structure of II Zwicky 23 and its set of companions and possible
scenarios of debris formation in this system.


title: Spherical Accretion

abstract:
  We compare different examples of spherical accretion onto a gravitating mass.
Limiting cases include the accretion of a collisionally dominated fluid and the
accretion of collisionless particles. We derive expressions for the accretion
rate and density profile for semi-collisional accretion which bridges the gap
between these limiting cases. Particle crossing of the Hill sphere during the
formation of the outer planets is likely to have taken place in the
semi-collisional regime.


title: Dynamics and Shape of Brightest Cluster Galaxies

abstract:
  We identified Brightest Cluster Members (BCM) on DSS images of 1083 Abell
clusters, derived their individual and host cluster redshifts from literature
and determined the BCM ellipticity. Half the BCMs move at a speed higher than
37 % of the cluster velocity dispersion sigma_{cl}, suggesting that most BCMs
are part of substructures falling into the main cluster. Both, the BCM's
velocity offset in units of sigma_{cl}, and BCM ellipticity, weakly decrease
with cluster richness.


title:
The Association of Compact Groups of Galaxies with Large-scale
  Structures

abstract:
  We use various samples of compact groups (CGs) to examine the types of
association CGs have with rich and poor clusters of galaxies at low (z~0.04)
and intermediate (z~0.1) redshifts. We find that ~10-20 % of CGs are associated
with rich clusters and a much larger fraction with poorer clusters or loose
groups. Considering the incompleteness of catalogs of poorer systems at
intermediate redshift, our result is consistent with all CGs at intermediate
redshift being associated with larger-scale systems. The richness of the
clusters associated with CGs significantly increases from z~0.04 to z~0.1,
while their Bautz-Morgan type changes from early to late type for the same
range in z. Neither trend is compatible with a selection effect in the cluster
catalogs used. We find earlier morphological types of galaxies to be more
frequent in CGs associated with larger-scale structures, compared to those in
CGs not associated to such structures. We consider this as new evidence that
CGs are part of the large-scale structure formation process and that they may
play an important role in the evolution of galaxies in these structures.


title: Rotational and Cyclical Variability in gamma Cassiopeia

abstract:
  We report results of a nine-year monitoring effort on the unusual classical
Be with a robotic ground-based (APT) B,V-filtered telescope as well as
simultaneous observations in 2004 November with this instrument and the RXTE
(X-ray) telescope. Our observations disclosed no correlated optical response to
the rapid X-ray flares in this star, nor did the star show any sustained flux
changes during the course of either of the two monitored nights in either
wavelength regime. Our optical light curves reveal that gamma Cas undergoes
\~3%-amplitude cycles with lengths of 60--90 days. Over the nine days we
monitored the star with the RXTE, the X-ray flux varied in phase with its
optical cycle and with an amplitude predicted from correlated optical/X-ray
data from an earlier paper. The amplitudes of the V magnitude cycles are
30--40% larger than the B amplitudes, suggesting the seat of the cycles is
circumstellar. The cycle lengths constantly change and can damp or grow on
timescales as short as 13 days. We have also discovered a coherent period of
1.21581 +/-0.00002 days in all our data, which is consistent only with
rotation. The full amplitude of this variation is 0.0060 in both filters. The
derived waveform, somewhat surprisingly, is almost sawtooth in shape. This
variation probably originates on the star's surface. This circumstance hints at
the existence of a strong magnetic field with a complex topology and an
associated heterogeneous surface composition.


title: A non-spherical core in the explosion of supernova SN 2004dj

abstract:
  An important and perhaps critical clue to the mechanism driving the explosion
of massive stars as supernovae is provided by the accumulating evidence for
asymmetry in the explosion. Indirect evidence comes from high pulsar
velocities, associations of supernovae with long-soft gamma-ray bursts, and
asymmetries in late-time emission-line profiles. Spectropolarimetry provides a
direct probe of young supernova geometry, with higher polarization generally
indicating a greater departure from spherical symmetry. Large polarizations
have been measured for 'stripped-envelope' (that is, type Ic) supernovae, which
confirms their non-spherical morphology; but the explosions of massive stars
with intact hydrogen envelopes (type II-P supernovae) have shown only weak
polarizations at the early times observed. Here we report multi-epoch
spectropolarimetry of a classic type II-P supernova that reveals the abrupt
appearance of significant polarization when the inner core is first exposed in
the thinning ejecta (~90 days after explosion). We infer a departure from
spherical symmetry of at least 30 per cent for the inner ejecta. Combined with
earlier results, this suggests that a strongly non-spherical explosion may be a
generic feature of core-collapse supernovae of all types, where the asphericity
in type II-P supernovae is cloaked at early times by the massive, opaque,
hydrogen envelope.


title:
New Supporting Evidence for the Overdensity of Galaxies around the
  Radio-Loud Quasar SDSS J0836+0054 at z =5.8

abstract:
  Recently, Zheng et al. (2005) found evidence for an overdensity of galaxies
around a radio-loud quasar, SDSS J0836+0054, at z=5.8 (a five arcmin$^2$
region). We have examined our deep optical imaging data (B, V, r', i', z', and
NB816) taken with the Suprime-Cam on the Subaru Telescope. The NB816
narrow-band filter (lambda_c = 815 nm and $\Delta\lambda = 12$ nm) is suitable
for searching for Ly$\alpha$ emitters at $z\approx 5.7$. We have found a new
strong Ly$\alpha$ emitter at $z \approx 5.7$ close to object B identified by
Zheng et al. Further, the non detection of the nine objects selected by Zheng
et al. (2005) in our B, V, and r' images provides supporting evidence that they
are high-z objects.


title:
Cosmological evolution with a logarithmic correction in the dark energy
  entropy

abstract:
  In a thermodynamical model of cosmological FLRW event horizons for the dark
energy (DE), we consider a logarithmic corrective term in the entropy to which
corresponds a new term in the DE density. This model of $\Lambda (t)$ in an
interacting two-component cosmology with cold dark matter (DM) as second
component leads to a system of coupled equations, yielding, after numerical
resolution, the evolutions of $\Lambda (t)$, the Hubble $H(t)$, vacuum density
$\Omega \_{\Lambda}(t)$, deceleration $q(t)$ and statefinder $R(t)$ and $S(t)$
parameters. Its results, compatible with an initial inflation and the current
observations of the so-called "concordance model", predict a graceful exit of
early inflation and the present acceleration and solve in the same time the age
and coincidence problems. Moreover they account for the low-$l$ CMBR power
spectrum suppression.


title: A Toy Model for Magnetic Connection in Black-Hole Accretion Disc

abstract:
  A toy model for magnetic connection in black hole (BH) accretion disc is
discussed based on a poloidal magnetic field generated by a single electric
current flowing around a Kerr black hole in the equatorial plane. We discuss
the effects of the coexistence of two kinds of magnetic connection (MC) arising
respectively from (1) the closed field lines connecting the BH horizon with the
disc (henceforth MCHD), and (2) the closed field lines connecting the plunging
region with the disc (henceforth MCPD). The magnetic field configuration is
constrained by conservation of magnetic flux and a criterion of the screw
instability of the magnetic field. Two parameters and are introduced to
describe our model instead of resolving the complicated MHD equations. Compared
with MCHD, energy and angular momentum of the plunging particles are extracted
via MCPD more effectively, provided that the BH spin is not very high. It turns
out that negative energy can be delivered to the BH by the plunging particles
without violating the second law of BH thermodynamics, however it cannot be
realized via MCPD in a stable way.


title:
Statistics of the individual-pulse polarization based on propagation
  effects in pulsar magnetosphere

abstract:
  Pulsar radio emission is modelled as a sum of two completely polarized
non-orthogonal modes with the randomly varying Stokes parameters and intensity
ratio. The modes are the result of polarization evolution of the original
natural waves in the hot magnetized weakly inhomogeneous plasma of pulsar
magnetosphere. In the course of wave mode coupling, the linearly polarized
natural waves acquire purely orthogonal elliptical polarizations. Further on,
as the waves pass through the cyclotron resonance, they become non-orthogonal.
The pulse-to-pulse fluctuations of the final polarization characteristics and
the intensity ratio of the modes are attributed to the temporal fluctuations in
the plasma flow.
  The model suggested allows to reproduce the basic features of the
one-dimensional distributions of the individual-pulse polarization
characteristics. Besides that, propagation origin of pulsar polarization
implies a certain correlation between the mode ellipticity and position angle.
On a qualitative level, for different sets of parameters, the expected
correlations appear compatible with the observed ones. Further theoretical
studies are necessary to establish the quantitative correspondence of the model
to the observational results and to develop a technique of diagnostics of
pulsar plasma on this basis.


title: An $ f(R) $ gravitation for galactic environments

abstract:
  We propose an action-based $ f(R) $ modification of Einstein's gravity which
admits of a modified Schwarzschild-deSitter metric. In the weak field limit
this amounts to adding a small logarithmic correction to the newtonian
potential. A test star moving in such a spacetime acquires a constant
asymptotic speed at large distances. This speed turns out to be proportional to
the fourth root of the mass of the central body in compliance with the
Tully-Fisher relation. A variance of MOND's gravity emerges as an inevitable
consequence of the proposed formalism. It has also been shown (Mendoza et al.
2006) that a) the gravitational waves in this spacetime propagate with the
speed of light in vacuum and b) there is a lensing effect additional to what
one finds in the classic GR.


title: Nearby AGN and their hosts in the near infrared

abstract:
  We present near infrared ISAAC VLT observations of nine (0.01<z<0.06) Active
Galactic Nuclei selected from the Hamburg/ESO Survey and the Veron-Cetty &
Veron catalog. Hydrogen recombination lines Pa$\alpha$ and Br$\gamma$ are
observed in seven of the nine sources of which five show a broad component. In
three sources, extended 1-0S(1) rotational-vibrational molecular hydrogen
emission is detected. Stellar CO absorption is seen in four sources. In one of
these objects, an upper limit of the central mass can be determined from the
stellar velocity field. H- and Ks-band imaging allow us to determine the
morphology class of the host galaxies. Colors (with supplementary J-band 2MASS
images) show that the four galaxies with detected CO absorption are
characterized by an overall strong stellar contribution. One galaxy shows an
increased extinction towards the nucleus. After removal of the nuclear point
source, the host galaxies show colors typical for non-active spiral galaxies.


title: Chaotic Feature in the Light Curve of 3C 273

abstract:
  Some nonlinear dynamical techniques, including state-space reconstruction and
correlation integral, are used to analyze the light curve of 3C 273. The result
is compared with a chaotic model. The similarity between them suggests that
there is a low-dimensional chaotic attractor in the light curve of 3C 273.


title: Chandra LETG Observations of Supernova Remnant 1987A

abstract:
  We discuss the results from deep Chandra LETG observations of the supernova
remnant 1987A (SNR 1987A). We find that a distribution of shocks, spanning the
same range of velocities (from 300 to 1700 km/s) as deduced in the first part
of our analysis (Zhekov et al. 2005, ApJL, 628, L127), can account for the
entire X-ray spectrum of this object. The post-shock temperature distribution
is bimodal, peaking at kT 0.5 and 3 keV. Abundances inferred from the X-ray
spectrum have values similar to those for the inner circumstellar ring, except
that the abundances of nitrogen and oxygen are approximately a factor of two
lower than those inferred from the optical/UV spectrum. The velocity of the
X-ray emitting plasma has decreased since 1999, apparently because the blast
wave has entered the main body of the inner circumstellar ring.


title:
Deep Impact : High Resolution Optical Spectroscopy with the ESO VLT and
  the Keck 1 telescope

abstract:
  We report on observations of comet 9P/Tempel 1 carried out before, during,
and after the NASA DEEP IMPACT event (UT July 4), with the optical
spectrometers UVES and HIRES mounted on the telescopes Kueyen of the ESO VLT
(Chile) and Keck 1 on Mauna Kea (Hawaii), respectively. A total observing time
of about 60 hours, distributed over 15 nights around the impact date, allowed
us (i) to find a periodic variation of 1.709 +/- 0.009 day in the CN and NH
flux, explained by the presence of two major active regions; (ii) to derive a
lifetime > ~ 5 x 10^4 s for the parent of the CN radical from a simple modeling
of the CN light curve after the impact; (iii) to follow the gas and dust
spatial profiles evolution during the 4 hours following the impact and derive
the projected velocities (400 m/s and 150 m/s respectively); (iv) to show that
the material released by the impact has the same carbon and nitrogen isotopic
composition as the surface material (12C/13C = 95 +/- 15 and 14N/15N = 145 +/-
20).


title: Probing the temporal variability of Cygnus X-1 into the soft state

abstract:
  Building on results from previous studies of Cygnus~X-1, we analyze Rossi
X-ray Timing Explorer (RXTE) data taken when the source was in the soft and
transitional spectral states. We look at the power spectrum in the 0.01 -- 50
Hz range, using a model consisting of a cut-off power-law and two Lorentzian
components. We are able to constrain the relation between the characteristic
frequencies of the Lorentzian components, and show that it is consistent with a
power-law relation having the same index (1.2) as previously reported for the
hard state, but shifted by a factor ~2. Furthermore, it is shown that the
change in the frequency relation seen during the transitions can be explained
by invoking a shift of one Lorentzian component to a higher harmonic, and we
explore the possible support for this interpretation in the other component
parameters. With the improved soft state results we study the evolution of the
fractional variance for each temporal component. This approach indicates that
the two Lorentzian components are connected to each other, and unrelated to the
power-law component in the power spectrum, pointing to at least two separate
emission components.


title:
Foreground Subtraction of Cosmic Microwave Background Maps using WI-FIT
  (Wavelet based hIgh resolution Fitting of Internal Templates)

abstract:
  We present a new approach to foreground removal for Cosmic Microwave
Background (CMB) maps. Rather than relying on prior knowledge about the
foreground components, we first extract the necessary information about them
directly from the microwave sky maps by taking differences of temperature maps
at different frequencies. These difference maps, which we refer to as internal
templates, consist only of linear combinations of galactic foregrounds and
noise, with no CMB component. We obtain the foreground cleaned maps by fitting
these internal templates to, and subsequently subtracting the appropriately
scaled contributions of them from, the CMB dominated channels. The fitting
operation is performed in wavelet space, making the analysis feasible at high
resolution with only a minor loss of precision. Applying this procedure to the
WMAP data, we obtain a power spectrum that matches the spectrum obtained by the
WMAP team at the signal dominated scales. Finally, we have revisited previous
claims about a north-south power asymmetry on large angular scales, and confirm
that these remain unchanged with this completely different approach to
foreground separation. This also holds when fitting the foreground contribution
independently to the northern and southern hemisphere indicating that the
asymmetry is unlikely to have its origin in different foreground properties of
the hemispheres. This conclusion is further strengthened by the lack of any
observed frequency dependence.


title: Scalar field haloes as gravitational lenses

abstract:
  A non-topological soliton model with a repulsive scalar self-interaction of
the Emden type provides a constant density core,similarly as the empirical
Burkert profile of dark matter haloes. As a further test, we derive the
gravitational lens properties of our model, in particular, the demarcation
curves between `weak' and `strong' lensing. Accordingly, strong lensing with
typically three images is almost three times more probable for our solitonic
model than for the Burkert fit. Moreover, some prospective consequences of a
possible flattening of dark matter haloes are indicated.


title:
Attempts to measure the magnetic field of the pulsating B star $\nu$
  Eridani

abstract:
  We report on attempts to measure the magnetic field of the pulsating B star
$\nu$ Eridani with the Musicos spectropolarimeter attached to the 2m telescope
at the Pic du Midi, France. This object is one of the most extensively studied
stars for pulsation modes, and the existence of a magnetic field was suggested
from the inequality of the frequency separations of a triplet in the stars'
oscillation spectrum. We show that the inferred 5-10 kG field was not present
during our observations, which cover about one year. We discuss the influence
of the strong pulsations on the analysis of the magnetic field strength and set
an upper limit to the effective longitudinal field strength and to the field
strength for a dipolar configuration. We also find that the observed wind line
variability is caused by the pulsations.


title: Modified Newtonian Dynamics as an extra dimensional effect

abstract:
  Modified Newtonian dynamics can be considered as an effect derived from a
squeezable extra dimension space. The third law of Newtonian dynamics can be
managed to remain valid in the 5-space. The critical acceleration parameter
$a_0$ appears naturally as the bulk acceleration that has to do with the
expanding universe in this setup. A simple toy model is presented in this
Letter to show that consistent theory can be built with the help of the extra
dimensional space.


title:
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. II.
  X-ray and Ultraviolet Continuum Variability

abstract:
  We report on two Chandra observations, and a simultaneous Hubble Space
Telescope ultraviolet observation, of the dwarf Seyfert 1 galaxy NGC 4395. Each
Chandra observation had a duration of ~30 ks, with a separation of ~50 ks. The
spectrum was observed to harden between these observations via a scaling down
of the soft-band flux. The inter-observation variability is in a different
sense to the observed variability within each observation and is most likely
the result of increased absorption. Spectral variations were seen during the
first observation suggesting that the X-ray emission is produced in more than
one disconnected region. We have also re-analyzed a ~17 ks Chandra observation
conducted in 2000. During the three Chandra observations the 2-10 keV flux is
about a factor of 2 lower than seen during an XMM-Newton observation conducted
in 2003. Moreover, the fractional variability amplitude exhibited during the
XMM-Newton observation is significantly softer than seen during the Chandra
observations. A power-spectral analysis of the first of the two new Chandra
observations revealed a peak at 341s with a formal detection significance of
99%. A similar peak was seen previously in the 2000 Chandra data. However, the
detection of this feature is tentative given that it was found in neither the
second of our two new Chandra observations nor the XMM-Newton data, and it is
much narrower than expected. The Hubble Space Telescope observation was
conducted during part of the second Chandra visit. A zero-lag correlation
between the ultraviolet and X-ray fluxes was detected with a significance of
about 99.5%, consistent with the predictions of the two-phase model for the
X-ray emission from active galactic nuclei.


title: Why X-ray--Selected AGN Appear Optically Dull

abstract:
  We investigate why half of X-ray--selected active galactic nuclei (AGN) in
deep surveys lack signs of accretion in their optical spectra. The majority of
these ``optically--dull'' AGN are no more than 6 times fainter than their host
galaxies in rest-frame R-band; as such, AGN lines are unlikely to be
overwhelmed by stellar continuum in at least half the sample. We find that
optically--dull AGN have the mid--infrared emission and L(x)/L(IR) ratios
characteristic of local Seyferts, suggesting that the cause of optical dullness
is not missing UV--optical continua. We compare the morphologies of 22
optically--dull and 9 optically--active AGN at 0.5<z<0.8, and find that
optically--dull AGN show a wide range of axis ratio, but optically--active AGN
have only very round axis ratios. We conclude that hard X-rays select AGN in
host galaxies with a wide range of inclination angle, but only those AGN in the
most face-on or spheroidal host galaxies show optical emission lines. Thus,
extranuclear dust in the host galaxy plays an important role in hiding the
emission lines of optically--dull AGN.


title: New Praesepe white dwarfs and the initial mass-final mass relation

abstract:
  We report the spectroscopic confirmation of four further white dwarf members
of Praesepe. This brings the total number of confirmed white dwarf members to
eleven making this the second largest collection of these objects in an open
cluster identified to date. This number is consistent with the high mass end of
the initial mass function of Praesepe being Salpeter in form. Furthermore, it
suggests that the bulk of Praesepe white dwarfs did not gain a substantial
recoil kick velocity from possible asymmetries in their loss of mass during the
asymptotic giant branch phase of evolution. By comparing our estimates of the
effective temperatures and the surface gravities of WD0833+194, WD0840+190,
WD0840+205 and WD0843+184 to modern theoretical evolutionary tracks we have
derived their masses to be in the range 0.72-0.76Msun and their cooling ages
\~300Myrs. For an assumed cluster age of 625+/-50Myrs the infered progenitor
masses are between 3.3-3.5Msun. Examining these new data in the context of the
initial mass-final mass relation we find that it can be adequately represented
by a linear function (a0=0.289+/-0.051, a1=0.133+/-0.015) over the initial mass
range 2.7Msun to 6Msun. Assuming an extrapolation of this relation to larger
initial masses is valid and adopting a maximum white dwarf mass of 1.3Msun, our
results support a minimum mass for core-collapse supernovae progenitors in the
range ~6.8-8.6Msun.


title:
VLT/UVES Spectroscopy of Individual Stars in Three Globular Clusters in
  the Fornax Dwarf Spheroidal Galaxy

abstract:
  We present a high resolution (R ~ 43000) abundance analysis of a total of
nine stars in three of the five globular clusters associated with the nearby
Fornax dwarf spheroidal galaxy. These three clusters (1, 2 and 3) trace the
oldest, most metal-poor stellar populations in Fornax. We determine abundances
of O, Mg, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba, La, Nd and Eu in most of these
stars, and for some stars also Mn and La. We demonstrate that classical
indirect methods (isochrone fitting and integrated spectra) of metallicity
determination lead to values of [Fe/H] which are 0.3 to 0.5 dex too high, and
that this is primarily due to the underlying reference calibration typically
used by these studies. We show that Cluster 1, with [Fe /H] = -2.5, now holds
the record for the lowest metallicity globular cluster. We also measure an
over-abundance of Eu in Cluster 3 stars that has only been previously detected
in a subgroup of stars in M15. We find that the Fornax globular cluster
properties are a global match to what is found in their Galactic counterparts;
including deep mixing abundance patterns in two stars. We conclude that at the
epoch of formation of globular clusters both the Milky Way and the Fornax dwarf
spheroidal galaxy shared the same initial conditions, presumably pre-enriched
by the same processes, with identical nucleosynthesis patterns.


title: Anomalous extinction behaviour towards the Type Ia SN 2003cg

abstract:
  We present optical and near-infrared photometry and spectroscopy of the Type
Ia SN 2003cg, which exploded in the nearby galaxy NGC 3169. The observations
cover a period between -8.5 and +414 days post-maximum. SN 2003cg is a normal
but highly-reddened Type Ia event. Its B magnitude at maximum B_max =
15.94+/-0.04 and Delta m_15(B)_obs = 1.12+/-0.04 (Delta m_15(B)_intrinsic =
1.25+/-0.05). Allowing R_v to become a free parameter within the Cardelli et
al. (1989) extinction law, simultaneous matches to a range of colour curves of
normal SNe Ia yielded E(B-V) = 1.33+/-0.11, and R_v = 1.80+/-0.19. While the
value obtained for R_v is small, such values have been invoked in the past, and
may imply a grain size which is small compared with the average value for the
local ISM.


title: The Southern Flanking Fields of the 25 Orionis Group

abstract:
  The stellar group surrounding the Be (B1Vpe) star 25 Orionis was discovered
to be a pre-main-sequence population by the Centro de Investigaciones de
Astronomia (CIDA) Orion Variability Survey and subsequent spectroscopy. We
analyze Sloan Digital Sky Survey multi-epoch photometry to map the southern
extent of the 25 Ori group and to characterize its pre-main-sequence
population. We compare this group to the neighboring Orion OB1a and OB1b
subassociations and to active star formation sites (NGC 2068/NGC 2071) within
the Lynds 1630 dark cloud. We find that the 25 Ori group has a radius of 1.4
degrees, corresponding to 8-11 pc at the distances of Orion OB1a and OB1b.
Given that the characteristic sizes of young open clusters are a few pc or less
this suggests that 25 Ori is an unbound association rather than an open
cluster. Due to its PMS population having a low Classical T Tauri fraction
(~10%) we conclude that the 25 Ori group is of comparable age to the 11 Myr
Orion OB1a subassociation.


title:
Effects of a Local Interstellar Magnetic Field on Voyager 1 and 2
  Observations

abstract:
  We show that that an interstellar magnetic field can produce a north/south
asymmetry in solar wind termination shock. Using Voyager 1 and 2 measurements,
we suggest that the angle $\alpha$ between the interstellar wind velocity and
magnetic field is $30^{\circ} < \alpha < 60^{\circ}$. The distortion of the
shock is such that termination shock particles could stream outward along the
spiral interplanetary magnetic field connecting Voyager 1 to the shock when the
spacecraft was within $\sim 2~AU$ of the shock. The shock distortion is larger
in the southern hemisphere, and Voyager 2 could be connected to the shock when
it is within $\sim 5~AU$ of the shock, but with particles from the shock
streaming inward along the field. Tighter constraints on the interstellar
magnetic field should be possible when Voyager 2 crosses the shock in the next
several years.


title: Old Main-Sequence Turnoff Photometry in the SMC

abstract:
  We present ground-based {\it B} and {\it R}-band color-magnitude diagrams
(CMDs) of unprecedented depth for twelve fields in the Small Magellanic Cloud
(SMC). They reach the oldest main-sequence turnoffs and cover a wide range of
galactocentric distances up to $\sim4\arcdeg$ from the SMC center, and are
located at different position angles. A picture of the stellar content in our
SMC fields is presented, through the comparison with theoretical isochrones.
Our study confirms the existence of strong population gradients and spatial
variation in the SMC stellar content.
  None of the SMC fields presented here are dominated by old stellar
populations which proves that at $\sim4\arcdeg$ from the SMC center we do not
reach an old stellar halo similar to that of the Milky Way.


title: Finding benchmark brown dwarfs to probe the IMF as a function of time

abstract:
  Using a simulated disk brown dwarf (BD) population, we find that new large
area infrared surveys are expected to identify enough BDs covering wide enough
mass--age ranges to potentially measure the mass function down to ~0.03Mo, and
the BD formation history out to 10 Gyr, at a level capable of establishing if
BD formation follows star formation. We suggest these capabilities are best
realised by spectroscopic calibration of BD properties (Teff, g and [M/H])
which, when combined with a measured luminosity and an evolutionary model can
give BD mass and age relatively independent of BD atmosphere models. Such
calibration requires an empirical understanding of how BD spectra are affected
by variations in these properties, and thus the identification and study of
"benchmark BDs" whose age and composition can be established independently. We
identify the best sources of benchmark BDs as young open cluster members,
moving group members, and wide (>1000AU) BD companions to both subgiant stars
and high mass white dwarfs (WDs). We have used 2MASS to measure a wide L dwarf
companion fraction of 2.7(+0.7/-0.5)%, which equates to a BD companion fraction
of 34(+9/-6)% for an alpha~1 companion mass function. Using this value we
simulate populations of wide BD binaries, and estimate that 80(+21/-14)
subgiant--BD binaries, and 50(+13/-10) benchmark WD--BD binaries could be
identified using current and new facilities. The WD--BD binaries should all be
identifiable using the Large Area Survey component of UKIDSS combined with
Sloan. Discovery of the subgiant--BD binaries will require a NIR imaging
campaign around a large (~900) sample of Hipparcos subgiants. If identified,
spectral studies of these benchmark brown dwarfs could reveal the spectral
sensitivities across the Teff, g and [M/H] space probed by new surveys.


title:
Radio observations of the planetary nebula around the OH/IR Star
  OH354.88-0.54 (V1018 Sco)

abstract:
  We present radio observations of the unique, recently formed, planetary
nebula (PN) associated with a very long-period OH/IR variable star V1018 Sco
that is unequivocally still in its asymptoticgiant branch phase. Two regions
within the optical nebula are clearly detected in nonthermal radio continuum
emission, with radio spectral indices comparable to those seen in
colliding-wind Wolf-Rayet binaries. We suggest that these represent shocked
interactions between the hot, fast stellar wind and the cold nebular shell that
represents the PN's slow wind moving away from the central star. This same
interface produces both synchrotron radio continuum and the optical PN
emission. The fast wind is neither spherical in geometry nor aligned withany
obvious optical or radio axis. We also report the detection of transient H2O
maser emission in this nebula.


title: Beta decay radiation signature from neutron-rich gamma-ray bursts?

abstract:
  Core collapse of massive stars and binary neutron stars or black hole-neutron
star binary mergers are likely progenitors of long and short duration gamma-ray
bursts respectively. Neutronized material in the former and neutron star
material in the latter are ejected by the central engine implying a
neutron-rich jet outflow. A free neutron, however, beta decays to a proton, an
electron (beta) and an anti-neutrino in about fifteen minutes in its rest
frame. Sudden creation of a relativistic electron is accompanied by radiation
with unique temporal and spectral signature. We calculate here this radiation
signature collectively emitted by all beta decay electrons from neutron-rich
outflow. Detection of this signature may thus provide strong evidence for not
only neutron but also for proton content in the relativistic gamma-ray burst
jets.


title:
A Shot in the Dark: A Technique for Locating the Stellar Counterparts of
  Damped Lyman Alpha Absorbers

abstract:
  We present initial results from a Magellan telescope program to image
galaxies that give rise to damped Lyman absorbers (DLAs) at 1.63 < z_DLA <
2.37. Our program differs from previous efforts in that we target quasars with
intervening Lyman limit systems (LLS) along the line of sight at redshift z_LLS
> 3.5. The higher-redshift LLS is applied as a blocking filter to remove the
glare of the background quasar at the rest-frame ultraviolet wavelengths of the
foreground galaxy. The complete absence of quasar light offers an unimpeded
view along the sightline to the redshift of the LLS, allowing an exhaustive
search for the DLA galaxy to the sensitivity limit of the imaging data (at or
better than 0.25L*). In both of our pilot fields (PKS2000-330, z_DLA=2.033 and
SDSS0322-0558, z_DLA=1.69), we identify an L* galaxy within 5" of the sightline
which has optical colors consistent with star-forming galaxies at z~2. We
examine the correlation between absorption-line properties and galaxy
luminosity and impact distance, and compare the high-redshift galaxy and
absorber pairs with those known at z<1.


title:
The effect of mass-segregation on gravitational wave sources near
  massive black holes

abstract:
  Gravitational waves (GWs) from the inspiral of compact remnants (CRs) into
massive black holes (MBHs) will be observable to cosmological distances. While
a CR spirals in, 2-body scattering by field stars may cause it to fall into the
MBH before reaching a short period orbit that would give an observable signal.
As a result, only CRs very near (~0.01 pc) the MBH can spiral in successfully.
In a multi-mass stellar population, the heaviest objects sink to the center,
where they are more likely to slowly spiral into the MBH without being
swallowed prematurely. We study how mass-segregation modifies the stellar
distribution and the rate of GW events. We find that the inspiral rate per
galaxy for white dwarfs is 30 per Gyr, for neutron stars 6 per Gyr, and for
stellar black holes (SBHs) 250 per Gyr. The high rate for SBHs is due to their
extremely steep density profile, n_{BH}(r)\propto r^{-2}. The GW detection rate
will be dominated by SBHs.


title:
Simultaneous photometry and echelle-spectroscopy of the dwarf nova BZ
  Ursae Majoris during the 2005 January Outburst

abstract:
  We report simultaneous photometric and echelle-spectroscopic observations of
the dwarf nova BZ UMa during which we were lucky to catch the system at the
onset of an outburst, the development of which we traced in detail from
quiescence to early decline. The outburst had a precursor, and was of a short
duration (~5 days) with a highly asymmetrical light curve. On the rise we
observed a `jump' during which the brightness almost doubled over the course of
half an hour. Power spectra analysis revealed well-defined oscillations with
period of ~42 minutes. Using Doppler tomography we found that the unusual
emission distribution detected in quiescence held during the outburst. After
the maximum a new emission source arose, from the inner hemisphere of the
secondary star, which became the brightest at that time. We analyse this
outburst in terms of `inside-out' and `outside-in' types, in order to determine
which of these types occured in BZ UMa.


title:
The hot stars in orbit around the M31 central supermassive black hole:
  are they young or old?

abstract:
  AIMS: The cluster of hot stars observed in orbit around the central black
hole of M31 has been interpreted as a 200 Myr starburst. The formation of a
population of young stars in close proximity to a massive black hole presents a
difficult challenge to star formation theory. We point out that in a high
stellar density environment, the course of stellar evolution is modified by
frequent collisions and mergers. METHODS: Blue stragglers, which are the
results of mergers in globular clusters, occupy the same position in the
color-magnitude diagram as the observed hot stars in M31. For confirmation, the
integrated spectrum of P3 is shown to be compatible with the spectral energy
distribution of a blue horizontal branch field star. RESULTS: We suggest an old
stellar population of evolved blue horizontal-branch stars and of merger
products cannot be ruled out on the basis of the available data. Observations
are suggested that would help distinguish between a ``young'' and ``old''
stellar population interpretation of the observations.


title:
First Results from the CHARA Array VII: Long-Baseline Interferometric
  Measurements of Vega Consistent with a Pole-On, Rapidly Rotating Star

abstract:
  We have obtained high-precision interferometric measurements of Vega with the
CHARA Array and FLUOR beam combiner in the K' band at projected baselines
between 103m and 273m. The measured visibility amplitudes beyond the first lobe
are significantly weaker than expected for a slowly rotating star characterized
by a single effective temperature and surface gravity. Our measurements, when
compared to synthetic visibilities and synthetic spectrophotometry from a
Roche-von Zeipel gravity-darkened model atmosphere, provide strong evidence for
the model of Vega as a rapidly rotating star viewed very nearly pole-on. Our
best fitting model indicates that Vega is rotating at ~91% of its angular
break-up rate with an equatorial velocity of 275 km/s. Together with the
measured vsin(i), this velocity yields an inclination for the rotation axis of
5 degrees. For this model the pole-to-equator effective temperature difference
is 2250 K, a value much larger than previously derived from spectral line
analyses. The derived equatorial T_eff of 7900 K indicates Vega's equatorial
atmosphere may be convective and provides a possible explanation for the
discrepancy. The model has a luminosity of ~37 Lsun, a value 35% lower than
Vega's apparent luminosity based on its bolometric flux and parallax, assuming
a slowly rotating star. The model luminosity is consistent with the mean
absolute magnitude of A0V stars. Our model predicts the spectral energy
distribution of Vega as viewed from its equatorial plane; a model which may be
employed in radiative models for the surrounding debris disk.


title: Neutron-capture elements in the metal-poor globular cluster M15

abstract:
  We report on observations of six giants in the globular cluster M15 (NGC
7078) using the Subaru Telescope to measure neutron-capture elemental
abundances. Our abundance analyses based on high-quality blue spectra confirm
the star-to-star scatter in the abundances of heavy neutron-capture elements
(e.g., Eu), and no significant s-process contribution to them, as was found in
previous studies. We have found, for the first time, that there are
anti-correlations between the abundance ratios of light to heavy
neutron-capture elements ([Y/Eu] and [Zr/Eu]) and heavy ones (e.g., Eu). This
indicates that light neutron-capture elements in these stars cannot be
explained by only a single r-process. Another process that has significantly
contributed to the light neutron-capture elements is required to have occurred
in M15. Our results suggest a complicated enrichment history for M15 and its
progenitor.