title:
VLT Spectroscopy of Globular Cluster Systems, II. Spectroscopic Ages,
  Metallicities, and [alpha/Fe] Ratios of Globular Clusters in Early-Type
  Galaxies

abstract:
  An analysis of ages, metallicities, and [alpha/Fe] ratios of globular cluster
systems in early-type galaxies is presented, based on Lick index measurements
summarized in Puzia et al. (2004, Paper I of this series). In the light of
calibration and measurement uncertainties, age-metallicity degeneracy, and the
relative dynamic range of Lick indices, as well as systematics introduced by
abundance ratio variations (in particular variations of [alpha/Fe] ratios), we
find that the most reliable age indicator for our dataset is a combination of
the Lick Balmer-line indices HgammaA, Hbeta, and HdeltaA. [MgFe]' is used as a
spectroscopic metallicity indicator which is least affected by [alpha/Fe]
variations. We introduce an interpolation routine to simultaneously derive
ages, metallicities, and [alpha/Fe] ratios from diagnostic grids constructed
from Lick indices. From a comparison of high-quality data with SSP model
predictions, we find that ~2/3 of the globular clusters in early-type galaxies
are older than 10 Gyr, up to 1/3 have ages in the range ~5-10 Gyr, and only a
few cluster are younger than ~5 Gyr. Our sample of globular clusters covers
metallicities from [Z/H] = -1.3 up to ~0.5 dex. We find that metal-rich
globular clusters show on average a smaller mean age and a larger age scatter
than their metal-poor counterparts. [alpha/Fe] diagnostic plots show that
globular cluster systems in early-type galaxies have super-solar alpha/Fe
abundance ratios with a mean [alpha/Fe] = 0.47+/-0.06 dex and a dispersion of
about 0.3 dex. We find evidence for a correlation between [alpha/Fe] and
metallicity, in the sense that more metal-rich clusters exhibit lower
alpha-element enhancements. [abridged]


title: Oscillations of Thick Accretion Discs Around Black Holes - II

abstract:
  We present a numerical study of the global modes of oscillation of thick
accretion discs around black holes. We have previously studied the case of
constant distributions of specific angular momentum. In this second paper, we
investigate (i) how the size of the disc affects the oscillation
eigenfrequencies, and (ii) the effect of power-law distributions of angular
momentum on the oscillations. In particular, we compare the oscillations of the
disc with the epicyclic eigenfrequencies of a test particle with different
angular momentum distributions orbiting around the central object. We find that
there is a frequency shift away from the epicyclic eigenfrequency of the test
particle to lower values as the size of the tori is increased. We have also
studied the response of a thick accretion disc to a localized external
perturbation using non constant specific angular momentum distributions within
the disc. We find that in this case it is also possible (as reported previously
for constant angular momentum distributions) to efficiently excite internal
modes of oscillation. In fact we show here that the local perturbations excite
global oscillations (acoustic p modes) closely related to the epicyclic
oscillations of test particles. Our results are particularly relevant in the
context of low mass X-ray binaries and microquasars, and the high frequency
Quasi-Periodic Oscillations (QPOs) observed in them. Our computations make use
of a Smooth Particle Hydrodynamics (SPH) code in azimuthal symmetry, and use a
gravitational potential that mimics the effects of strong gravity.


title: Stellar Photometry and Astrometry with Discrete Point Spread Functions

abstract:
  The key features of the MATPHOT algorithm for precise and accurate stellar
photometry and astrometry using discrete Point Spread Functions are described.
A discrete Point Spread Function (PSF) is a sampled version of a continuous PSF
which describes the two-dimensional probability distribution of photons from a
point source (star) just above the detector. The shape information about the
photon scattering pattern of a discrete PSF is typically encoded using a
numerical table (matrix) or a FITS image file. Discrete PSFs are shifted within
an observational model using a 21-pixel-wide damped sinc function and position
partial derivatives are computed using a five-point numerical differentiation
formula. Precise and accurate stellar photometry and astrometry is achieved
with undersampled CCD observations by using supersampled discrete PSFs that are
sampled 2, 3, or more times more finely than the observational data. The
precision and accuracy of the MATPHOT algorithm is demonstrated by using the
C-language MPD code to analyze simulated CCD stellar observations; measured
performance is compared with a theoretical performance model. Detailed analysis
of simulated Next Generation Space Telescope observations demonstrate that
millipixel relative astrometry and millimag photometric precision is achievable
with complicated space-based discrete PSFs. For further information about
MATPHOT and MPD, including source code and documentation, see
http://www.noao.edu/staff/mighell/matphot


title: The Fine Structure Lines of Hydrogen in HII Regions

abstract:
  The 2s_{1/2} state of hydrogen is metastable and overpopulated in HII
regions. In addition, the 2p states may be pumped by ambient Lyman-alpha
radiation. Fine structure transitions between these states may be observable in
HII regions at 1.1 GHz (2s_{1/2}-2p_{1/2}) and/or 9.9 GHz (2s_{1/2}-2p_{3/2}),
although the details of absorption versus emission are determined by the
relative populations of the 2s and 2p states. The n=2 level populations are
solved with a parameterization that allows for Lyman-alpha pumping of the 2p
states. The density of Lyman-alpha photons is set by their creation rate,
easily determined from the recombination rate, and their removal rate. Here we
suggest that the dominant removal mechanism of Lyman-alpha radiation in HII
regions is absorption by dust. This circumvents the need to solve the
Lyman-alpha transfer problem, and provides an upper limit to the rate at which
the 2p states are populated by Lyman-alpha photons. In virtually all cases of
interest, the 2p states are predominantly populated by recombination, rather
than Lyman-alpha pumping. We then solve the radiative transfer problem for the
fine structure lines in the presence of free-free radiation. In the likely
absence of Lyman-alpha pumping, the 2s_{1/2}-2p_{1/2} lines will appear in
stimulated emission and the 2s_{1/2}-2p_{3/2} lines in absorption. Searching
for the 9.9 GHz lines in high emission measure HII regions offers the best
prospects for detection. The lines are predicted to be weak; in the best cases,
line-to-continuum ratios of several tenths of a percent might be expected with
line strengths of tens to a hundred mK with the Green Bank Telescope.


title: Strong mean field dynamos require supercritical helicity fluxes

abstract:
  Several one and two dimensional mean field models are analyzed where the
effects of current helicity fluxes and boundaries are included within the
framework of the dynamical quenching model. In contrast to the case with
periodic boundary conditions, the final saturation energy of the mean field
decreases inversely proportional to the magnetic Reynolds number. If a
nondimensional scaling factor in the current helicity flux exceeds a certain
critical value, the dynamo can operate even without kinetic helicity, i.e. it
is based only on shear and current helicity fluxes, as first suggested by
Vishniac & Cho (2001, ApJ 550, 752). Only above this threshold is the current
helicity flux also able to alleviate catastrophic quenching. The fact that
certain turbulence simulations have now shown apparently non-resistively
limited mean field saturation amplitudes may be suggestive of the current
helicity flux having exceeded this critical value. Even below this critical
value the field still reaches appreciable strength at the end of the kinematic
phase, which is in qualitative agreement with dynamos in periodic domains.
However, for large magnetic Reynolds numbers the field undergoes subsequent
variations on a resistive time scale when, for long periods, the field can be
extremely weak.


title:
Mimac-He3, a Project for a Micro-TPC Matrix of Chambers of Helium 3 for
  Axial Direct Detection of Non-Baryonic Dark Matter

abstract:
  MIMAC-He3 (MIcro-tpc MAtrix of Chambers of Helium 3) is a project for direct
detection of non-baryonic dark matter search using He3 as sensitive medium. The
priviledged properties of He3 are highlighted. The double detection :
ionization and track projection, is explained and rejection evaluated. A
phenomenological study in effective SUSY models has been to investigate the
MIMAC-He3 complementarity with respect to existing Dark Matter detectors.


title: Neutrino Astronomy beyond and beneath the Horizons

abstract:
  The Earth's Shadow to Cosmic Rays offer a windows to Tau Neutrino Astronomy
at the Horizon edges. Inclined and Horizontal C.R. Showers (70^o-90^o zenith
angle) produce secondary (gamma,e) mostly suppressed by high column atmosphere
depth. The shower Cherenkov photons are diluted and filtered by air opacity,
but secondary penetrating, muon pairs and their decay into electron pairs,
revive additional Cerenkov flash lights. Most largest GeVs gamma telescopes may
detect such UHECR horizontal showers. Arrival angle and column depth, shower
shape, timing may inform on the altitude interaction and on primary UHECR
composition. At larger zenith angle (90^o-99^o) more rare up-going showers are
traced by muon (as well electromagnetic) bundles that would give evidence of
rare Earth-Skimming neutrinos, tau and anti-tau neutrinos, at PeVs-EeVs
energies. Their rate may be comparable with 6.3 PeVs anti-neutrino electron
induced air-shower originated in interposed atmosphere, by W^- resonance at
Glashow peak. Additional and complementary UHE SUSY neutralino or staus may
blaze. Their nature might be disentangled by Stereoscopic Telescopes array.
Magic and Hess telescope in present set up may be already comparable to AMANDA
underground neutrino detector. Such telescopes pointing at the horizons toward
active sources (AGN,BL Lac Objects, GRBs or SGRs blazing micro-quasar jet, and
SNRs) do experience in those directions an air mass corresponding to a km^3
water one. Therefore Horizontal Showering is already the most sensitive windows
to Neutrino Astronomy possibly pointing to AGN,GRB or SGR events.


title: Neutrino asymmetry around black holes: Neutrinos interact with gravity

abstract:
  Propagation of a fermion in curved space-time generates a gravitational
interaction due to coupling of its spin with the space-time curvature
connection. This gravitational interaction, which is an axial-four-vector
multiplied by a four gravitational vector potential, appears as a CPT violating
term in the Lagrangian which generates an opposite sign and thus asymmetry
between the left-handed and the right handed partners under the CPT
transformation. In the case of neutrinos, this property can generate a neutrino
asymmetry in the Universe. If the background metric is of the rotating black
hole, i.e. the Kerr geometry, this interaction for the neutrino is non-zero.
Therefore, the dispersion energy relations for the neutrino and its
anti-neutrino are different which give rise to the difference in their number
densities and the neutrino asymmetry in the Universe in addition to the known
relic asymmetry.


title:
Chandra and XMM-Newton observations of the exceptional pulsar PSR
  B0628-28

abstract:
  PSR B0628-28 is a radio pulsar which was first detected in the X-ray band by
ROSAT and then later observed with Chandra and XMM-Newton. The Chandra
observation yielded an X-ray luminosity two orders of magnitude higher than
what is expected for spin-powered pulsars, also there were no pulsations
detected. The XMM-Newton observation, however, reveals pulsations at the
expected radio period, P=1.244 s. The simultaneously analyzed spectra also
gives a luminosity (in cgs) Log Lx=30.34, which is ~350 times greater than what
would be expected from the correlation between Lx-Edot.


title:
Point-like gamma ray sources as signatures of distant accelerators of
  ultra high energy cosmic rays

abstract:
  We discuss the possibility of observing distant accelerators of ultra high
energy cosmic rays in synchrotron gamma rays. Protons propagating away from
their acceleration sites produce extremely energetic electrons during
photo-pion interactions with cosmic microwave background photons. If the
accelerator is embedded in a magnetized region, these electrons will emit high
energy synchrotron radiation. The resulting synchrotron source is expected to
be point-like and detectable in the GeV-TeV energy range if the magnetic field
is at the nanoGauss level.


title: Formation and Evolution of Supermassive Black Holes

abstract:
  The correlation between the mass of supermassive black holes in galaxy nuclei
and the mass of the galaxy spheroids or bulges (or more precisely their central
velocity dispersion), suggests a common formation scenario for galaxies and
their central black holes. The growth of bulges and black holes can commonly
proceed through external gas accretion or hierarchical mergers, and are both
related to starbursts. Internal dynamical processes control and regulate the
rate of mass accretion. Self-regulation and feedback are the key of the
correlation. It is possible that the growth of one component, either BH or
bulge, takes over, breaking the correlation, as in Narrow Line Seyfert 1
objects. The formation of supermassive black holes can begin early in the
universe, from the collapse of Population III, and then through gas accretion.
The active black holes can then play a significant role in the re-ionization of
the universe. The nuclear activity is now frequently invoked as a feedback to
star formation in galaxies, and even more spectacularly in cooling flows. The
growth of SMBH is certainly there self-regulated. SMBHs perturb their local
environment, and the mergers of binary SMBHs help to heat and destroy central
stellar cusps. The interpretation of the X-ray background yields important
constraints on the history of AGN activity and obscuration, and the census of
AGN at low and at high redshifts reveals the downsizing effect, already
observed for star formation. History appears quite different for bright QSO and
low-luminosity AGN: the first grow rapidly at high z, and their number density
decreases then sharply, while the density of low-luminosity objects peaks more
recently, and then decreases smoothly.


title: Once-ionized helium in superstrong magnetic fields

abstract:
  It is generally believed that magnetic fields of some neutron stars, the
so-called magnetars, are enormously strong, up to 10^{14} - 10^{15} G. Recent
investigations have shown that the atmospheres of magnetars are possibly
composed of helium. We calculate the structure and bound-bound radiative
transitions of the He^+ ion in superstrong fields, including the effects caused
by the coupling of the ion's internal degrees of freedom to its center-of-mass
motion. We show that He^+ in superstrong magnetic fields can produce spectral
lines with energies of up to about 3 keV, and it may be responsible for
absorption features detected recently in the soft X-ray spectra of several
radio-quiet isolated neutron stars. Quantization of the ion's motion across a
magnetic field results in a fine structure of spectral lines, with a typical
spacing of tens electron-volts in magnetar-scale fields. It also gives rise to
ion cyclotron transitions, whose energies and oscillator strengths depend on
the state of the bound ion.


title:
Distance determinations using type II supernovae and the expanding
  photosphere method

abstract:
  Due to their high intrinsic brightness, type II supernovae (SN) can be used
as lighthouses to constrain distances in the Universe using variants of the
Baade-Wesselink method. Based on a large set of CMFGEN models (Hillier & Miller
1998) covering the photospheric phase of type II SN, we study the various
concepts entering one such technique, the Expanding Photosphere Method (EPM).
We compute correction factors $\xi$ needed to approximate the synthetic
Spectral Energy Distribution (SED) with that of a blackbody at temperature $T$.
Our $\xi$, although similar, are systematically greater, by $\sim 0.1$, than
the values obtained by Eastman et al. (1996). This translate into a systematic
enhancement of 10-20% in EPM-distances. We find that line emission and
absorption, not directly linked to color temperature variations, can
considerably alter the synthetic magnitude, and cause above-unity $\xi$-values.
Optically-thick lines, present in the optical at late-times, can also introduce
a strong wavelength-dependence of the photospheric radius, invalidating the use
of the Baade method. Both the impact of line-blanketing on the SED and the
photospheric radius at low $T$ suggest that the EPM is best used at early
times, when the outflow is fully ionized and line-opacity mostly confined to
the UV range. We also investigate how reliably one can measure the photospheric
velocity from P-Cygni line profiles. Contrary to the usually held belief, the
velocity at maximum absorption in the P-Cygni trough of optically-thick lines
can both {\it overestimate or underestimate} the photospheric velocity, with a
magnitude that depends on the SN outflow density gradient and the optical
thickness of the line.


title:
Comments on "Angular Momentum Transport in Quasi-Keplerian Accretion
  Disks"

abstract:
  Subramanian, Pujari and Becker (2004) claim that the correct expression for
the angular momentum transport in an accretion disc, which is proportional to
dOmega/dR, can be derived on the basis of the analysis of the epicyclic motion
of gas parcels in adjacent eddies in the disc. We study their argument and show
that their derivation contains several fundamental errors: 1) the biased choice
of the desired formula from an infinite number of formulae; 2) the biased
choice of parcel trajectories; and 3) confusion regarding the reference frames.
Following 1) we could derive, for example, a (invalid) formula in which the
angular momentum transport is proportional to dv_phi/dR, and from 2) we could
even prove that the angular momentum transport is either inward or null. We
present the correct approach to the problem of angular momentum transport in an
accretion disc in terms of mean free path theory.


title:
Dating the stellar population in massive early-type galaxies at
  $z\sim$1.5

abstract:
  We present the analysis of 10 massive early-type galaxies at $z\sim1.5$. They
have been identified by means of a near-IR low resolution spectroscopic
follow-up of a complete sample of 36 bright (K' $<$ 18.5) Extremely Red Objects
(EROs, R-K'$>$ 5) selected from the Munich Near-IR ClusterSurvey (MUNICS; Drory
et al. 2001). The low resolution near-IR spectra constrain their redshift at
$1.2<z<1.7$, implying absolute magnitudes M$_{K'}<-26.0$ and stellar masses
well in excess of 10$^{11}$ M$_\odot$. Under the hypothesis of pure passive
evolution from $z\sim1.5$ to $z=0$, in the local universe they would have
luminosities L$_K\ge2.5$L$^*$. Thus, they are the high-z counterparts of the
local old massive (10$^{11}-10^{12}$ M$_\odot$) early-type galaxies populating
the bright end of the local luminosity function of galaxies. The comparison of
their spectro-photometric properties with a grid of synthetic models suggests
that the stellar populations in more than half of the sample are about
$\sim$3-5 Gyr old and 1-2 Gyr old in the remaining part. These ages imply
formation redshift $z_{f} > 2$ for all the galaxies and $z_{f} \geq 4$ for the
oldest ones. The comparison of the 4000\AA break and of the overall spectral
shape of the average spectrum of the 10 galaxies at $z\sim1.5$ with those of
their local counterpartsconfirms that field massive early-type galaxies formed
the bulk of their stellar mass at $2<z<4$, most likely over a short ($<$ 1 Gyr)
star formation time scale, consistently with the results derived from the
analysis of their individual spectro-photometric properties.


title: e-VLBI observations of SN2001em - an off-axis GRB candidate

abstract:
  Studying transient phenomena with the Very Long Baseline Interferometry
(VLBI) technique faces severe difficulties because the turnaround time of the
experiments from the observations to the scientific result is rather long. The
e-VLBI technique has made it possible to transfer the data from a number of
European VLBI Network (EVN) telescopes to the central data processor at JIVE
through optical fibres, and correlate them in real time. The main goal of this
paper is to introduce this rapidly developing new technique, by presenting
observational results from a recent experiment. We observed SN2001em, a Type
Ib/c supernova with an e-VLBI array and the Multi-Element Radio Linked
Interferometer Network (MERLIN) in the UK. The source is marginally detected in
our observations. We cannot make definite conclusions whether it is resolved at
1.6 GHz or not. Our data show that SN2001em either started fading in the last
couple of months, or its radio spectrum is inverted at low
frequencies,indicating free-free or synchrotron self-absorption. This is quite
unusual, but not unprecedented in radio SNe.


title:
Constraining beta(z) and Omega_m from redshift-space distortions in z~3
  galaxy surveys

abstract:
  We use sample of 813 Lyman-break galaxies (LBGs) with 2.6<z<3.4 to perform a
detailed analysis of the redshift-space (z-space) distortions in their
clustering pattern and from them derive confidence levels in the
[Omega_m,beta(z=3)] plane. We model the z-space distortions in the shape of the
correlation function measured in orthogonal directions, xi(sigma,pi). This
modeling requires an accurate description of the real-space correlation
function to be given as an input. From the projection of xi(sigma,pi) in the
angular direction, w_p(sigma), we derive the best fitting amplitude and slope
for the LBG real-space correlation function: r_0=4.48(+0.17)(-0.18) h(-1) Mpc
and gamma=1.76(+0.08)(-0.09) (xi(r)= (r/r_0)^-gamma). A comparison between the
shape of xi(s) and w_p(sigma) suggests that xi(r) deviates from a simple
power-law model, with a break at ~9 h(-1) Mpc. This model is consistent with
the observed projected correlation function. However, due to the limited size
of the fields used, the w_p(sigma) results are limited to sigma < 10 h(-1) Mpc.
Assuming this double power-law model, and by analysing the shape distortions in
xi(sigma,pi), we find the following constraints: beta(z=3) = 0.15
(+0.20)(-0.15), Omega_m = 0.35 (+0.65)(-0.22). Combining these results with
orthogonal constraints from linear evolution of density perturbations, we find
that beta(z=3) = 0.25 (+0.05)(-0.06), Omega_m = 0.55 (+0.45)(-0.16).


title: Limits on the primordial stellar multiplicity

abstract:
  Most stars - especially young stars - are observed to be in multiple systems.
Dynamical evolution is unable to pair stars efficiently, which leads to the
conclusion that star-forming cores must usually fragment into \geq 2 stars.
However, the dynamical decay of systems with \geq 3 or 4 stars would result in
a large single-star population that is not seen in the young stellar
population. Additionally, ejections would produce a significant population of
hard binaries that are not observed. This leads to a strong constraint on star
formation theories that cores must typically produce only 2 or 3 stars. This
conclusion is in sharp disagreement with the results of currently available
numerical simulations that follow the fragmentation of molecular cores and
typically predict the formation of 5--10 seeds per core. In addition, open
cluster remnants may account for the majority of observed highly hierarchical
higher-order multiple systems in the field.


title:
Astrometric Binaries in the Age of the Next Generation of Large (Space)
  Telescopes

abstract:
  I analyze several catalogs of known visual and spectroscopic binaries and
conclude that a large number of binaries is missing in current catalogs.
Samples of the best studied (nearby and bright) stars indicate that the true
binary fraction may be as high as 95%. A preliminary analysis indicates that
these binaries can a ect the astrometry signicantly.


title:
Gamma-Ray Bursts and the Earth: Exploration of Atmospheric, Biological,
  Climatic and Biogeochemical Effects

abstract:
  Gamma-Ray Bursts (GRBs) are likely to have made a number of significant
impacts on the Earth during the last billion years. We have used a
two-dimensional atmospheric model to investigate the effects on the Earth's
atmosphere of GRBs delivering a range of fluences, at various latitudes, at the
equinoxes and solstices, and at different times of day. We have estimated DNA
damage levels caused by increased solar UVB radiation, reduction in solar
visible light due to $\mathrm{NO_2}$ opacity, and deposition of nitrates
through rainout of $\mathrm{HNO_3}$. For the ``typical'' nearest burst in the
last billion years, we find globally averaged ozone depletion up to 38%.
Localized depletion reaches as much as 74%. Significant global depletion (at
least 10%) persists up to about 7 years after the burst. Our results depend
strongly on time of year and latitude over which the burst occurs. We find DNA
damage of up to 16 times the normal annual global average, well above lethal
levels for simple life forms such as phytoplankton. The greatest damage occurs
at low to mid latitudes. We find reductions in visible sunlight of a few
percent, primarily in the polar regions. Nitrate deposition similar to or
slightly greater than that currently caused by lightning is also observed,
lasting several years. We discuss how these results support the hypothesis that
the Late Ordovician mass extinction may have been initiated by a GRB.

categories: astro-ph physics.ao-ph physics.bio-ph physics.geo-ph physics.space-ph


title:
The History of the Baryon Budget: Cosmic Logistics in a Hierarchical
  Universe

abstract:
  Using a series of high-resolution N-body hydrodynamical numerical
simulations, we investigate several scenarios for the evolution of the baryon
budget in galactic halos. We derive individual halo star formation history
(SFH), as well as the global star formation rate in the universe. We develop a
simple analytical model that allows us to compute surprisingly accurate
predictions, when compared to our simulations, but also to other simulations
presented in Springel & Hernquist (2003). The model depends on two main
parameters: the star formation time scale t* and the wind efficiency eta_w. We
also compute, for halos of a given mass, the baryon fraction in each of the
following phases: cold disc gas, hot halo gas and stars. Here again, our
analytical model predictions are in good agreement with simulation results, if
one correctly takes into account finite resolution effect.
  We compare predictions of our analytical model to several observational
constraints, and conclude that a very narrow range of the model parameters is
allowed. The important role played by galactic winds is outlined, as well as a
possible `superwind' scenario in groups and clusters. The `anti-hierarchical'
behavior of observed SFH is well reproduced by our best model with t*=3Gyr and
eta_w=1.5. We obtain in this case a present-day cosmic baryon budget of Omega*=
0.004, Omega_cold=0.0004, Omega_hot=0.01 and Omega_back=0.02 (diffuse
background).


title:
Early-Time Chromatic Variations in the Wind-Swept Medium of GRB 021211
  and the Faintness of its Afterglow

abstract:
  We present Follow-Up Network for Gamma-Ray Bursts (FUN GRB) Collaboration
observations of the optical afterglow of GRB 021211 made between 143 seconds
and 102 days after the burst. Our unique data set includes the earliest
filtered detections and color information for an afterglow in the pre-Swift
era. We find that the afterglow is best described by (1) propagation through a
wind-swept medium, (2) a cooling break that is blueward of the observed optical
frequencies, and (3) a hard electron energy distribution. However, superimposed
on this "standard model" behavior we find significant chromatic variations
within the first few hours after the burst. We consider possible reasons for
these variations, including the possibility that they are due to a dust echo.
Finally, we constrain physical parameters that describe the afterglow and
surrounding medium for a variety of scenarios and find that GRB 021211's
afterglow is faint for a combination of 3-4 reasons: (1) a low fraction of
energy in relativistic electrons, (2) a low density for the wind-swept medium,
implying either a low mass-loss rate and/or a high wind velocity for the
progenitor, (3) a wide opening/viewing angle for the jet, and possibly (4)
moderate source frame extinction. The jet appears to be significantly far from
equipartition and magnetically dominated. More extreme versions of this might
explain the darkness of many afterglows in the Swift era.


title: Measurement of core-shifts with astrometric multi-frequency calibration

abstract:
  VLBI is unique, among the space geodetic techniques, in its contribution to
defining and maintaining the International Celestial Reference Frame, providing
precise measurements of coordinates of extragalactic radiosources. The quest
for increasing accuracy of VLBI geodetic products has lead to a deeper revision
of all aspects that might introduce errors in the analysis. The departure of
the observed sources from perfect, stable, compact and achromatic celestial
targets falls within this category. This paper is concerned with the impact of
unaccounted frequency-dependent position shifts of source cores in the analysis
of dual-band S/X VLBI geodesy observations, and proposes a new method to
measure them. The multi-frequency phase transfer technique developed and
demonstrated by Middelberg et al. (2005) increases the high frequency coherence
times of VLBI observations, using the observations at a lower frequency. Our
proposed SOURCE/FREQUENCY PHASE REFERENCING method endows it with astrometric
applications by adding a strategy to estimate the ionospheric contributions.
Here we report on the first successful application to measure the core shift of
the quasar 1038+528 A at S and X-bands, and validate the results by comparison
with those from standard phase referencing techniques. In this particular case,
and in general in the cm-wavelength regime, both methods are equivalent.
Moreover the proposed method opens a new horizon with targets and fields
suitable for high precision astrometric studies with VLBI, especially at high
frequencies where severe limitations imposed by the rapid fluctuations in the
troposphere prevent the use of standard phase referencing techniques.


title:
Constraints on dark energy from the observed density fluctuations
  spectrum and supernova data

abstract:
  One of the greatest challenges in cosmology today is to determine the nature
of dark energy, the source of the observed present acceleration of the
universe. High precision experiments are being developed to reduce the
uncertainties in the observations. Recently, we showed that the agreement to an
accuracy of 10% of measurements of the present density fluctuations
(\delta\rho/\rho)^2, derived from galaxy distribution (GD) data and cosmic
microwave background (CMB) anisotropies in the \LambdaCDM model, puts very
strong limits on the possible decay of the vacuum energy into cold dark matter.
Using this agreement, combined with the evidence that the matter density
\Omega_M^0=0.28\pm 0.02 and that the universe is approximately flat, we show
that the vacuum metamorphosis model (VMM) and the popular brane-world model
(BWM), both used to explain dark energy, can be discarded. When we relax the
\Omega_M^0 requirement, we find that an agreement within 10% can be obtained
only with \Omega_M^0\simeq 0.36 for the VMM and \Omega_M^0\simeq 0.73 for the
BWM, both of which are not consistent with observations. The agreement of the
CMB and GD data and previous constraints from SNIa data exclude, or put strong
limits on, other dark energy models, which have been suggested, that can be
described by the parametrized equation of state (EOS) w=p/\rho= w_0 + w_a(1-a),
where w_0 and w_a are constants, a is the cosmological scale factor and p
(\rho) is the pressure (energy density) of the dark energy. We find that the
supergravity (SUGRA) model with w_0=-0.82 and w_a=0.58 can be discarded. In
general, we find best values -1.86<w_0<-1.72 with 1.53<w_a<2.0. For redshifts
z\sim 0.5-1, where the supernova data is sensitive, w\sim -1 for this
parametrized EOS.


title:
Tracing large-scale structure at high redshift with Lyman-alpha
  emitters: the effect of peculiar velocities

abstract:
  We investigate the effect of peculiar velocities on the redshift space
distribution of z>~2 galaxies, and we focus in particular on Ly-alpha emitters.
We generate catalogues of dark matter (DM) halos and identify emitters with
halos of the same co-moving space density (M(Ly-alpha emitters) ~ 3x10^11
M_sun). We decompose the peculiar velocity field of halos into streaming,
gradient and random components, and compute and analyse these as a function of
scale. Streaming velocities are determined by fluctuations on very large
scales, strongly affected by sample variance, but have a modest impact on the
interpretation of observations. Gradient velocities are the most important as
they distort structures in redshift space, changing the thickness and
orientation of sheets and filaments. Random velocities are typically below or
of the same order as the typical observational uncertainty on the redshift. We
discuss the importance of these effects for the interpretation of data on the
large-scale structure as traced by Ly-alpha emitters (or similar kinds of
astrophysical high-redshift objects), focusing on the induced errors in the
viewing angles of filaments. We compare our predictions of velocity patterns
for Ly-alpha emitters to observations and find that redshift clumping of
Ly-alpha emitters, as reported for instance in the fields of high-redshift
radio galaxies, does not allow to infer whether an observed field is sampling
an early galaxy overdensity.


title: A new inflaton model beginning near the Planck epoch

abstract:
  The Starobinsky model predicts a primordial inflation period without the
presence of an inflaton field. The modified version of this model predicts a
simple time dependence for the Hubble parameter $H(t)$, which decreases slowly
between the Planck epoch and the end of the inflation, $H(t)=M_{\rm Pl}-\beta
M_{\rm Pl}^2 t$, where $\beta$ is a dimensionless constant to be adjusted from
observations. We investigate an inflaton model which has the same time
dependence for $H(t)$. A reverse engineered inflaton potential for the time
dependence of $H$ is derived. Normalization of the derived inflaton potential
is determined by the condition that the observed density fluctuations,
$\delta\rho/\rho\approx 10^{-5}$, are created at $\sim 60 e$-folds before the
end of inflation. The derived potential indicates an energy (mass) scale,
$M_{\rm end}\sim 10^{13} {\rm GeV}$, at the end of inflation. Using the slow
roll parameters, which are obtained from this potential, we calculate the
spectral index for the scalar modes $n_S$ and the relative amplitude of the
tensor to scalar modes $r$. A tensor contribution, $r\simeq 0.13$, and an
approximately Harrison-Zeldovich density perturbation spectrum, $n_S \simeq
0.95$, are predicted.


title: Damped Lyman Alpha Surveys and Statistics - A Review

abstract:
  The history and progress of DLA research over the past several decades is
reviewed here. Larger datasets and deeper surveys, particularly over the last
couple of years, have improved our knowledge of the neutral gas content and
distribution in the universe at all observable redshifts, including the present
epoch. New results on the statistics of DLAs at z<1.65 from our HST-UV surveys
are presented and discussed in the context of recent results at z=0 and at high
redshift. We find that Omega_{DLA}(z>0) remains roughly constant to within the
uncertainties; the z=0 value of the neutral gas mass density, Omega_{g}, is a
factor of ~2 less than Omega_{DLA}. The DLA incidence, n(z), undergoes rapid
evolution between redshifts 5 and 2, but is consistent with the no-evolution
curve in the current concordance cosmology for z ~< 2. We also show that if the
local Schmidt law relating surface density of gas and star formation rate (SFR)
is valid at the DLA redshifts, then the DLA SFR density is too low for them to
provide a significant contribution to the cosmic star formation history (SFH)
at z >~ 1. This implies that the DLAs are unlikely to be the same population as
the star forming galaxies (i.e., the Lyman break and sub-millimeter galaxies)
that dominate the SFH of the high redshift universe. We suggest that this
discrepancy and the DLA ``missing metals'' problem could be the result of
missing very high column density gas due to its very small absorption cross
section. (abridged)


title:
Closing in on a Short-Hard Burst Progenitor: Constraints from Early-Time
  Optical Imaging and Spectroscopy of a Possible Host Galaxy of GRB 050509b

abstract:
  The localization of the short-duration, hard-spectrum GRB 050509b was a
watershed event. Thanks to the nearly immediate relay of the GRB position by
Swift, we began imaging the GRB field 8 minutes after the burst and continued
for the following 8 days. No convincing optical/infrared candidate afterglow or
supernova was found for the object. We present a re-analysis of the XRT
afterglow and find an absolute position that is ~4" to the west of the XRT
position reported previously. Close to this position is a bright elliptical
galaxy with redshift z=0.2248, about 1' from the center of a rich cluster of
galaxies. Based on positional coincidences, the GRB and the bright elliptical
are likely to be physically related. We thus have discovered evidence that at
least some short-duration, hard-spectra GRBs arise at cosmological distances.
However, while GRB 050509b was underluminous compared to long-duration GRBs, we
demonstrate that the ratio of the blast-wave energy to the gamma-ray energy is
consistent with that of long-duration GRBs. Based on this analysis, on the
location of the GRB (40 +- 13 kpc from a bright galaxy), on the galaxy type
(elliptical), and the lack of a coincident supernova, we suggest that there is
now observational consistency with the hypothesis that short-hard bursts arise
during the merger of a compact binary. We limit the properties of a
Li-Paczynski ''mini-supernova.'' Other progenitor models are still viable, and
additional rapidly localized bursts from the Swift mission will undoubtedly
help to further clarify the progenitor picture. (abridged)


title: RAM: A Relativistic Adaptive Mesh Refinement Hydrodynamics Code

abstract:
  We have developed a new computer code, RAM, to solve the conservative
equations of special relativistic hydrodynamics (SRHD) using adaptive mesh
refinement (AMR) on parallel computers. We have implemented a
characteristic-wise, finite difference, weighted essentially non-oscillatory
(WENO) scheme using the full characteristic decomposition of the SRHD equations
to achieve fifth-order accuracy in space. For time integration we use the
method of lines with a third-order total variation diminishing (TVD)
Runge-Kutta scheme. We have also implemented fourth and fifth order Runge-Kutta
time integration schemes for comparison. The implementation of AMR and
parallelization is based on the FLASH code. RAM is modular and includes the
capability to easily swap hydrodynamics solvers, reconstruction methods and
physics modules. In addition to WENO we have implemented a finite volume module
with the piecewise parabolic method (PPM) for reconstruction and the modified
Marquina approximate Riemann solver to work with TVD Runge-Kutta time
integration. We examine the difficulty of accurately simulating shear flows in
numerical relativistic hydrodynamics codes. We show that under-resolved
simulations of simple test problems with transverse velocity components produce
incorrect results and demonstrate the ability of RAM to correctly solve these
problems. RAM has been tested in one, two and three dimensions and in
Cartesian, cylindrical and spherical coordinates. We have demonstrated
fifth-order accuracy for WENO in one and two dimensions and performed detailed
comparison with other schemes for which we show significantly lower convergence
rates. Extensive testing is presented demonstrating the ability of RAM to
address challenging open questions in relativistic astrophysics.


title:
The X-ray Spectral Properties and Variability of Luminous High-Redshift
  Active Galactic Nuclei

abstract:
  We perform a detailed investigation of moderate-to-high quality X-ray spectra
of ten of the most luminous active galactic nuclei (AGNs) known at z>4 (up to
z~6.28). This study includes five new XMM observations and five archived X-ray
observations (four by XMM and one by Chandra). We find that the X-ray power-law
photon indices of our sample, composed of eight radio-quiet sources and two
that are moderately radio loud, are not significantly different from those of
lower redshift AGNs. The upper limits obtained on intrinsic neutral hydrogen
column densities, N_H<~10^{22}-10^{23} cm^{-2}, indicate that these AGNs are
not significantly absorbed. A joint fit performed on our eight radio-quiet
sources, with a total of ~7000 photons, constrains the mean photon index of z>4
radio-quiet AGNs to Gamma=1.97^{+0.06}_{-0.04}, with no detectable intrinsic
dispersion from source to source. We also obtain a strong constraint on the
mean intrinsic column density, N_H<~3x10^{21} cm^{-2}, showing that optically
selected radio-quiet AGNs at z>4 are, on average, not more absorbed than their
lower-redshift counterparts. All this suggests that the X-ray production
mechanism and the central environment in radio-quiet AGNs have not
significantly evolved over cosmic time. The mean equivalent width of a putative
neutral narrow Fe Ka line is constrained to be <~190 eV, and similarly we place
constraints on the mean Compton reflection component (R<~1.2). None of the AGNs
varied on short (~1 hr) timescales, but on longer timescales (months-to-years)
strong variability is observed in four of the sources. In particular, the X-ray
flux of the z=5.41 radio-quiet AGN SDSS 0231-0728 dropped by a factor of ~4
over a rest-frame period of 73 d. This is the most extreme X-ray variation
observed in a luminous z>4 radio-quiet AGN.


title:
High Energy Afterglow Emission from Giant Flares of Soft Gamma-Ray
  Repeaters: The Case of the 2004 December 27 Event from SGR 1806-20

abstract:
  We discuss the high enegry afterglow emission (including high energy photons,
neutrinos and cosmic rays) following the 2004 December 27 Giant Flare from SGR
1806-20. If the initial outflow is relativistic with a bulk Lorentz factor
\Gamma_0\sim {\rm tens}, the high-energy tail of the synchrotron emission from
electrons in the forward shock region gives rise to a prominent sub-GeV
emission, if the electron spectrum is hard enough and if the intial Lorentz
factor is high enough. This signal could serve as a diagnosis of the initial
Lorentz factor of the giant flare outflow. This component is potentially
detectable by GLAST if a similar giant flare occurs in the GLAST era. With the
available 10 MeV data, we constrain that \Gamma_0 < 50 if the electron
distribution is a single power law. For a broken power law distribution of
electrons, a higher \Gamma_0 is allowed. At energies higher than 1 GeV, the
flux is lower because of a high energy cut off of the synchrotron emission
component. The synchrotron self-Compton emission component and the inverse
Compton scattering component off the photons in the giant flare oscillation
tail are also considered, but they are found not significant given a moderate
\Gamma_0 (e.g. \leq 10). The forward shock also accelerates cosmic rays to the
maximum energy 10^{17}eV, and generate neutrinos with a typical energy
10^{14}eV through photomeson interaction with the X-ray tail photons. However,
they are too weak to be detectable.


title: Direct Detection of Extra-Solar Comets is Possible

abstract:
  The dust tails of comets similar to Hale-Bopp can scatter as much optical
light as does the Earth. Space-based observatories such as the Terrestrial
Planet Finder or Darwin that will detect extra-solar terrestrial planets also
will be able to detect extra-solar comets.


title:
An Investigation of Diffuse Interstellar Gas toward a Large, Low
  Extinction Window into the Inner Galaxy

abstract:
  Halpha and Hbeta spectroscopy with the Wisconsin H-Alpha Mapper (WHAM)
reveals a strong concentration of high velocity emission in a ~ 5 by 5 deg area
centered near (l.b) = (27,-3), known as the Scutum Cloud. The high velocities
imply that we are detecting optical emission from near the plane of the Galaxy
out to the tangent point at heliocentric distances of D \gtrsim 6 kpc, assuming
the gas participates in circular Galactic rotation. The ratio of the Halpha to
Hbeta emission as a function of velocity suggests that dust along these lines
of sight produces a total visual extinction of A_v ~ 3 at D ~ 6 kpc. This makes
it possible to use optical emission lines to explore the physical conditions of
ionized gas in the inner Galaxy. At a Galactocentric distance R_G ~ 4 kpc, for
example, we find that the H^+ has an rms midplane density of ~ 1 cm^-3 with a
vertical scale height of ~ 300 pc. We also find evidence for an increase in the
flux of Lyman continuum photons and an increase in the ratio of ionized to
neutral hydrogen toward the inner Galaxy. We have extended the measurements of
E(B-V) in this direction to distances far beyond what has been accessible
through stellar photometry and find E(B-V)/N_H to be near the local mean of 1.7
x 10^-22 cm^2 mag, with evidence for an increase in this ratio at R_G ~ 4 kpc.
Finally, our observations of [NII] 6583, [SII] 6716, and [OIII] 5007 toward the
window reveal that in the inner Galaxy the temperature of the gas and the
ionization state of oxygen increase with increasing height from the midplane.


title:
The obscuration by dust of most of the growth of supermassive black
  holes

abstract:
  Supermassive black holes underwent periods of exponential growth during which
we seem them as quasars in the distant Universe. The summed emission from these
quasars generates the cosmic X-ray background, the spectrum of which has been
used to argue that most black-hole growth is obscured. There are clear examples
of obscured black-hole growth in the form of `type-2' quasars, but their
numbers are fewer than expected from modelling of the X-ray background. Here we
report on the direct detection of a population of distant type-2 quasars which
is at least comparable in size to the well-known unobscured type-1 population.
We selected objects that have mid-infrared and radio emissions characteristic
of quasars, but which are faint at near-infrared and optical wavelengths. This
population is responsible for most of the black hole growth in the young
Universe and, throughout cosmic history, black-hole growth occurs in the dusty,
gas-rich centres of active galaxies.


title: MERLIN monitoring of recent core-collapse supernovae

abstract:
  The star formation rate (SFR) in starburst galaxies can be measured by many
methods, one of which is through the supernova rate. Due to the heavy dust
obscuration in these galaxies, searches for new supernovae in the optical or
infra-red can easily miss events occurring in the central starburst regions. As
part of a long term program to estimate the SFR in a sample of nearby
starbursts we are using MERLIN and the VLA to regularly observe the galaxies
for new radio supernovae. As part of this project, regular MERLIN observations
have been made of two recent optically bright supernovae: 2004dj and 2004et.
Both supernovae are of Type II and have been monitored frequently over periods
of a few months, resulting in well sampled radio "light" curves for both
objects.


title:
A multiwavlength study of PSR B0628-28: The first overluminous
  rotation-powered pulsar?

abstract:
  The ROSAT source RX J0630.8-2834 was suggested by positional coincidence to
be the X-ray counterpart of the old field pulsar PSR B0628-28. This
association, however, was regarded to be unlikely based on the computed
energetics of the putative X-ray counterpart. In this paper we report on
multiwavelength observations of PSR B0628-28 made with the ESO/NTT observatory
in La Silla, the Jodrell Bank radio observatory and XMM-Newton. Although the
optical observations do not detect any counterpart of RX J0630.8-2834 down to a
limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations
finally confirmed it to be the pulsar's X-ray counterpart by detecting X-ray
pulses with the radio pulsar's spin-period. The X-ray pulse profile is
characterized by a single broad peak with a second smaller peak leading the
main pulse component by ~144 degree. The fraction of pulsed photons is (38 +-
7)% with no strong energy dependence in the XMM-Newton bandpass. The pulsar's
X-ray spectrum is well described by a single component power law with photon
index 2.63^{+0.23}_{-0.15}, indicating that the pulsar's X radiation is
dominated by non-thermal emission processes. A low level contribution of
thermal emission from residual cooling or from heated polar caps, cannot be
excluded. The pulsar's spin-down to X-ray energy conversion efficiency is
obtained to be ~16% for the radio dispersion measure inferred pulsar distance.
If confirmed, PSR B0628-28 would be the first X-ray overluminous
rotation-powered pulsar identified among all ~1400 radio pulsars known today.


title: Microlensing in the double quasar SBS1520+530

abstract:
  We present the results of a monitoring campaign of the double quasar
SBS1520+530 at Maidanak observatory from April 2003 to August 2004. We obtained
light curves in V and R filters that show small-amplitude \Delta m~0.1 mag
intrinsic variations of the quasar on time scales of about 100 days. The data
set is consistent with the previously determined time delay of \Delta
t=(130+-3) days by Burud et al. (2002). We find that the time delay corrected
magnitude difference between the quasar images is now larger by (0.14+-0.03)
mag than during the observations by Burud et al. (2002). This confirms the
presence of gravitational microlensing variations in this system.


title: Soft Gamma-Ray Bursts in the BATSE data

abstract:
  We performed the scan of the BATSE DISCLA records inspecting 25-50 keV range
to pick up soft GRBs. We applied the same technique as in our previous (Stern
et al. 2001) scan in the 50-300 keV range. We scanned about 1.8 year of the
data and found 30 new gamma-ray burst (GRB)s. The total number of soft GRBs in
the BATSE data, with the count rate in the 25-50 keV range higher than in the
50-300 keV range, is only 4%. There are about two extremely soft events per
year which are invisible about 50 keV and which could constitute a new class of
events separate from the GRB phenomenon. We also show that X-ray flashes (XRFs)
detected by BeppoSAX have a hardness ratio very similar to that of normal GRBs,
supporting a view that XRFs and GRBs are a single phenomenon with a wide
spectral variety.


title:
The Highest Magnetic Fields in the Universe: Anomalous X-Ray Pulsars and
  Soft Gamma-ray Repeaters

abstract:
  In the last few years it has been recognized that two apparently distinct
classes of peculiar high-energy sources are actually related and can be
explained as young neutron stars with magnetic fields as high as 10e14 - 10e15
Gauss. One of these ''magnetars'', SGR 1806-20, has recently emitted the most
powerful giant flare ever recorded. The high-energy observations of SGR 1806-20
carried out with XMM-Newton and INTEGRAL in the past two years showed a long
term trend of increasing activity preceding the 2004 December 27 event.
INTEGRAL data of this giant flare provided unique evidence for hard X-ray
emission lasting about one hour after the burst onset, possibly due to the
interaction of mildly relativistic ejecta with the circumstellar medium.


title: From ISO to Spitzer: a new view of the AGB-PN transition phase

abstract:
  We present a novel classification scheme for stars evolving in the transition
phase between the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN)
stage based on the results obtained with ISO-SWS. With the better sensitivity
and higher spatial resolution of Spitzer this analysis can now be extended to a
larger number of sources located in the Galactic Bulge, in the Magellanic
Clouds and in other Galaxies of the Local Group, offering an excellent
opportunity to study the validity of the proposed scheme in environments which
are free of the distance scale bias that hinder the observations made with ISO
on galactic sources located at uncertain distances. The new observations will
be used to test the current evolutionary models which predict the dredge-up of
processed material to the surface of low- and intermediate-mass stars as a
function of the progenitor mass and of the metallicity.


title:
Three Dimensional Evolution of a Relativistic Current Sheet : Triggering
  of Magnetic Reconnection by the Guide Field

abstract:
  The linear and non-linear evolution of a relativistic current sheet of pair
($e^{\pm}$) plasmas is investigated by three-dimensional particle-in-cell
simulations. In a Harris configuration, it is obtained that the magnetic energy
is fast dissipated by the relativistic drift kink instability (RDKI). However,
when a current-aligned magnetic field (the so-called "guide field") is
introduced, the RDKI is stabilized by the magnetic tension force and it
separates into two obliquely-propagating modes, which we call the relativistic
drift-kink-tearing instability (RDKTI). These two waves deform the current
sheet so that they trigger relativistic magnetic reconnection at a crossover
thinning point. Since relativistic reconnection produces a lot of non-thermal
particles, the guide field is of critical importance to study the energetics of
a relativistic current sheet.


title: The Limits of Quintessence

abstract:
  We present evidence that the simplest particle-physics scalar-field models of
dynamical dark energy can be separated into distinct behaviors based on the
acceleration or deceleration of the field as it evolves down its potential
towards a zero minimum. We show that these models occupy narrow regions in the
phase-plane of w and w', the dark energy equation-of-state and its
time-derivative in units of the Hubble time. Restricting an energy scale of the
dark energy microphysics limits how closely a scalar field can resemble a
cosmological constant. These results, indicating a desired measurement
resolution of order \sigma(w')\approx (1+w), define firm targets for
observational tests of the physics of dark energy.


title: Finding outlier light-curves in catalogs of periodic variable stars

abstract:
  We present a methodology to discover outliers in catalogs of periodic
light-curves. We use cross-correlation as measure of ``similarity'' between two
individual light-curves and then classify light-curves with lowest average
``similarity'' as outliers. We performed the analysis on catalogs of variable
stars of known type from the MACHO and OGLE projects and established that our
method correctly identifies light-curves that do not belong to those catalogs
as outliers. We show how our method can scale to large datasets that will be
available in the near future such as those anticipated from Pan-STARRS and
LSST.


title: The redshift distribution of gamma-ray bursts revisited

abstract:
  In this letter, we calculate the redshift distribution of gamma-ray bursts
assuming that they trace (i) the globally averaged star formation rate or (ii)
the average metallicity in the Universe. While at redshifts 5 and below, both
the star formation rate and metallicity are observationally determined modulo
some uncertainties, at higher redshifts there are few constraints. We
extrapolate the star formation rate and metallicity to higher redshifts and
explore models that are broadly consistent with bounds on the optical depth
from WMAP results. In addition, we also include parametric descriptions of the
luminosity function, and the typical spectrum for GRBs. With these essential
ingredients included in the modeling, we find that a substantial fraction 75%
of GRBs are expected to originate at redshifts below 4, in variance with some
previous estimates. Conversely, if we assume as expected for the collapsar
model that gamma-ray bursts favour a low metallicity environment and therefore,
relate the GRB rate to a simple model of the average metallicity as a function
of redshift, we find that a higher fraction of bursts, about 40% originate from
redshifts greater than 4. We conclude with the implications of SWIFT GRB
detections.


title:
Spherical Gravitational Collapse of Annihilating Dark Matter and the
  Minimum Mass of CDM Black Holes

abstract:
  Spherical gravitational collapse of a cold gas of annihilating particles
involves a competition between the free-fall rate $\propto\sqrt{\rho}$ and the
(s-wave) annihilation rate $\propto\rho$. Thus, there is a critical density
$\rhoann$ above which annihilation proceeds faster than free fall.
Gravitational collapse of a cloud of (initial) mass $M$ to a black hole is only
possible if $3/32\pi G^3M^2\lesssim\rhoann$, or $M\gtrsim\Mann\equiv (3/32\pi
G^3\rhoann)^{1/2}$. For a particle mass $m$ and freeze-out temperature
$T_f=m/x_f$, the minimum black hole mass is $\Mann\approx 10^{10}\msun
\times(x_f\sqrt{g_\star}/100\omcdm g_{\star S}m({\rm Gev}))$, where $g_{\star
S}$ and $g_\star$ are degeneracy factors. The formation of a black hole of
initial mass $M_{BH}$ is accompanied by the annihilation of about $M_{ann}$
released in a burst lasting a time $\sim GM_{BH}$ that could reach a total
annihilation luminosity $\sim 10^{59} {\rm erg s^{-1}}$. The absence of
astronomical observations of such spectacular events suggests either: (i) the
branching ratio for CDM annihilation to $e^{+}e^{-}$ pairs or quarks $\lesssim
10^{-10}$, while the branching ratio to $\nu{\bar{\nu}}$ is $\lesssim 10^{-5}$;
or (ii) CDM is not made of annihilating particles, but may be in some
non-annihilating form, such as axions; or (iii) CDM black holes never form.


title:
Enhanced abundances in three large-diameter mixed-morphology supernova
  remnants

abstract:
  We present an X-ray study of three mixed-morphology supernova remnants
(SNRs), HB 21, CTB 1 and HB 3, using archival ASCA and ROSAT data. These data
are complemented by archival Chandra X-ray Observatory data for CTB 1 and
XMM-Newton X-ray Observatory data for HB 3. The spectra from HB 21 and HB 3 are
well-described with a single-temperature thermal plasma in ionization
equilibrium, while a two-temperature thermal plasma is found in CTB 1. We found
enhanced abundances in all three SNRs. The elemental abundance of Mg is clearly
enhanced in CTB 1, while HB 21 has enhanced abundances of Si and S. The
situation is not so clear in HB 3 -- the plasma in this SNR either has
significantly enhanced abundances of O, Ne and Mg, or it has marginally
enhanced abundances of Mg and under-abundant Fe. We discuss the plausibility of
mixed-morphology SNR models for the three SNRs and the presence of enhanced
abundances. We revise a list of MM SNRs and their properties, compare the three
SNRs studied here with other members of this class, and discuss the presence of
enhanced elemental abundances in MM SNRs. We also report the ASCA detection of
a compact source in the southern part of HB 3. The source spectrum is
consistent with a power law with a photon index of ~2.7, and an unabsorbed
X-ray flux of ~10^{-12} erg/cm^2/s in the 0.5--10.0 keV band. The column
density towards this source differs from that towards the SNR, and it is
therefore unlikely they are related.


title:
BIMA Array Detections of HCN in Comets LINEAR (C/2002 T7) and NEAT
  (C/2001 Q4)

abstract:
  We present interferometric detections of HCN in comets LINEAR (C/2002 T7) and
NEAT (C/2001 Q4) with the Berkeley-Illinois-Maryland Association (BIMA) Array.
With a 25.4"x20.3" synthesized beam around Comet LINEAR and using a variable
temperature and outflow velocity (VTOV) model, we found an HCN column density
of N_T=6.4+-2.1x10^12 cm^-2, and a production rate of Q(HCN)=6.5+-2.2x10^26
s^-1, giving a production rate ratio of HCN relative to H_2O of ~3.3+-1.1x10^-3
and relative to CN of ~4.6+-1.5. With a 21.3"x17.5" synthesized beam around
Comet NEAT and using a VTOV model, we found an HCN column density of
N_T=8.5+-4.5x10^11 cm^-2, and a production rate of Q(HCN)=8.9+-4.7x10^25 s^-1,
giving a production rate ratio of HCN relative to H_2O of ~7.4+-3.9x10^-4 and
relative to CN of ~0.3+-0.2. For both comets, the production rates relative to
H_2O are similar to those found in previous comet observations. For Comet
LINEAR the production rate relative to CN is consistent with HCN being the
primary parent species of CN, while for Comet NEAT it is too low for this to be
the case.


title: Young Neutron Stars and Their Wind Nebulae

abstract:
  With Teragauss magnetic fields, surface gravity sufficiently strong to
significantly modify light paths, central densities higher than that of a
standard nucleus, and rotation periods of only hundredths of a second, young
neutron stars are sites of some of the most extreme physical conditions known
in the Universe. They generate magnetic winds with particles that are
accelerated to energies in excess of a TeV. These winds form
synchrotron-emitting bubbles as the particle stream is eventually decelerated
to match the general expansion caused by the explosion that formed the neutron
stars. The structure of these pulsar wind nebulae allow us to infer properties
of the winds and the pulsating neutron stars themselves. The surfaces of the
the stars radiate energy from the rapidly cooling interiors where the physical
structure is basically unknown because of our imprecise knowledge of the strong
interaction at ultrahigh densities. Here I present a summary of recent
measurements that allow us to infer the birth properties of neutron stars and
to probe the nature of their winds, the physics of their atmospheres, and the
structure of their interiors.


title: Radio Spectral Index Study of the SNRs OA184 and VRO42.05.01

abstract:
  New images of the Supernova Remnants (SNRs) OA184 and VRO42.05.01 are
presented at 408 MHz and 1420 MHz, from the Canadian Galactic Plane Survey
(CGPS) data. The SNRs' flux densities at both 408 MHz and 1420 MHz are found
and corrected for flux from compact sources within the SNRs. The integrated
flux-density based spectral indices (S$_{\nu}$$\propto$$\nu$$^{-\alpha}$) are
0.25+-0.03 for OA184 and 0.36+-0.06 for VRO42.05.01. These agree with the
respective T-T plot spectral indexes of 0.23+-0.06 and 0.36+-0.03. OA184's
spectral index is smaller than previously published values. The older flux
density values of OA184 from lower resolution data include a contribution from
a non-SNR ridge emission region and from compact sources within OA184.
Subtracting these contributions results in a spectral index of 0.32+-0.06 (38
MHz to 2695 MHz) or 0.28+-0.06 (408 MHz to 2695 MHz). Correction of published
fluxes for point sources for VRO.42.05.01 results in a spectral index of
0.32+-0.05 for 38 MHz to 2695 MHz. We also find spatial variations of spectral
index. For OA184 $\alpha$ varies from 0.1 to 0.3 (with errors $\simeq$0.1). For
VRO42.05.01, the shell region has $\alpha$=0.31 and the wing region has
$\alpha=0.47$ (with errors $\simeq$0.03).


title: Coupled Evolution of Primordial Gravity Waves and Relic Neutrinos

abstract:
  We describe analytically the cosmological evolution of primordial gravity
waves (tensor perturbations) taking into account their coupling to relic
neutrinos. We prove that as a consequence of causality the neutrino-induced
phase shift of subhorizon tensor oscillations tends on small scales to zero.
For the tensor modes that reenter the horizon in the radiation era after
neutrino decoupling we calculate the neutrino suppression factor as
1-5rho_nu/9rho+O[(rho_nu/rho)^2]. This result is consistent with the value
obtained for three neutrino flavors by Weinberg and is in agreement with
numerical Boltzmann evolution. A minimal formula with the correct asymptotic
form on small and large scales reproduces to about ten percent the evolution on
all scales probed by the CMB. A more accurate solution (in terms of elementary
functions) shows that the modes reentering the horizon in the radiation era are
slightly enhanced and the phase of their temporal oscillations is shifted by
subdominant nonrelativistic matter. The phase shift grows logarithmically on
subhorizon scales until radiation-matter equality; the accumulated shift scales
for k>>k_eq as (ln k)/k. The modes reentering the horizon after equality are,
in turn, affected by the residual radiation density. These modes follow the
naive matter-era evolution which is advanced by a redshift and scale
independent increment of conformal time. In an appendix, we introduce a general
relativistic measure of radiation intensity that in any gauge obeys a simple
transport equation and for decoupled particles is conserved on superhorizon
scales for arbitrary initial conditions in the full nonlinear theory.


title: X-ray emission from early-type stars in the Orion Nebula Cluster

abstract:
  The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion
Trapezium are examined with data from the Chandra Orion Ultradeep Project
(COUP). On the basis of simple theories for X-ray emission, we define two
classes separated at spectral type B4: hotter stars have strong winds that may
give rise to X-ray emission in small- or large-scale wind shocks, and cooler
stars that should be X-ray dark due to their weaker winds and absence of outer
convection zones where dynamos can generate magnetic fields.
  Only two of the massive stars show exclusively the constant soft-spectrum
emission expected from the standard model for X-ray emission from hot stars
involving many small shocks in an unmagnetized radiatively accelerated wind.
Most of the other massive O7-B3 stars exhibit some combination of soft-spectrum
wind emission, hard-spectrum flaring, and/or rotational modulation indicating
large-scale inhomogeneity, suggesting magnetic confinement of winds with
large-scale shocks.
  Most of the stars in the weak-wind class exhibit X-ray flares and have
luminosities that are consistent with magnetic activity from known or unseen
low-mass companions. All non-detections belong to the weak-wind class.


title:
The Calibration of the Swift/UVOT Optical Observations: A Recipe for
  Photometry

abstract:
  Swift/UVOT has the capability to provide critical insight into the physics of
the early afterglows of gamma-ray bursts (GRBs). But without precise
calibration of the UVOT to standard photometric systems, it is impossible to
leverage late- time, ground-based follow-up data to the early-time UVOT
observations. In this paper, we present a calibration of the Swift/UVOT
photometry to the standard Johnson UBV system for the UVOT UBV filters,and a
step-by-step photometry recipe for analyzing these data. We base our analysis
on aperture photometry performed on the ground-based and UVOT observations of
the local standard stars in the fields of supernovae (SNe) 2005am and 2005cf,
and a number of Landolt standard stars.We find that the optimal photometry
aperture radius for UVOT data is small (2".5 for unbinned data,3".0 for 2X2
binned data),and show that the coincidence- loss (C-loss) correction is
important even for relatively faint magnitudes (mag 16 to 19). Based on a
theoretically motivated model,we fit the C-loss correction with two parameters,
the photometric zero point (ZP) and the saturation magnitude (m_inf), and
derive tight constraints for both parameters [sigma(ZP) = 0.01 mag and
sigma(m_inf) = 0.02 mag)].We find that the color term correction is not
necessary for the UVOT B and V filters,but is necessary for the U filter for
blue objects [(U - V) < 0.4 mag]. We also apply our calibration results to the
UVOT observations of GRB 050603. There is a scatter of ~0.04--0.08 mag in our
final UVOT photometry, the cause of which is unclear, but may be partly due to
the spatial variation in the pixel sensitivity of the UVOT detector.


title: Branes in Supernova Shells

abstract:
  This paper is firstly intended to review shortly the most recent developments
and ideas resulting from the necessity of having a scale at which gravitation
to unify the other fundamental forces. With the declared intention of
predicting an {\it in situ} distinct possibility for Kaluza-Klein gravitons
formation in the supernova shell we are using state of the art simulations
\citep{langer,ud1,ud2,ud3} for massive stellar winds to infer that the
supernova shock which will hit such winds will meet a non-isotropic and
non-homogeneous matter distribution with a very distinct geometry. By linking
this to the mechanism of particle shock acceleration at cosmic ray energies
(Fermi acceleration) and the related spallation in the wind shell, the result
is the creation of proper conditions for Kaluza-Klein gravitons formation in
the supernova shell from neutrino secondary particles (cosmic ray spallation
products) interacting with $\sim 10^{18}$ eV cosmic rays.


title: Measuring diffuse neutrino fluxes with IceCube

abstract:
  In this paper the sensitivity of a future kilometer-sized neutrino detector
to detect and measure the diffuse flux of high energy neutrinos is evaluated.
Event rates in established detection channels, such as muon events from charged
current muon neutrino interactions or cascade events from electron neutrino and
tau neutrino interactions, are calculated using a detailed Monte Carlo
simulation. Neutrino fluxes as expected from prompt charm decay in the
atmosphere or from astrophysical sources such as Active Galactic Nuclei are
modeled assuming power laws. The ability to measure the normalization and slope
of these spectra is then analyzed.
  It is found that the cascade channel generally has a high sensitivity for the
detection and characterization of the diffuse flux, when compared to what is
expected for the upgoing- and downgoing-muon channels. A flux at the level of
the Waxman-Bahcall upper bound should be detectable in all channels separately
while a combination of the information of the different channels will allow
detection of a flux more than one order of magnitude lower. Neutrinos from the
prompt decay of charmed mesons in the atmosphere should be detectable in future
measurements for all but the lowest predictions.


title: Mass-Varying Neutrinos from a Variable Cosmological Constant

abstract:
  We consider, in a completely model-independent way, the transfer of energy
between the components of the dark energy sector consisting of the cosmological
constant (CC) and that of relic neutrinos. We show that such a cosmological
setup may promote neutrinos to mass-varying particles, thus resembling a
recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without
introducing any acceleronlike scalar fields. Although a formal similarity of
the FNW scenario with the variable CC one can be easily established, one
nevertheless finds different laws for neutrino mass variation in each scenario.
We show that as long as the neutrino number density dilutes canonically, only a
very slow variation of the neutrino mass is possible. For neutrino masses to
vary significantly (as in the FNW scenario), a considerable deviation from the
canonical dilution of the neutrino number density is also needed. We note that
the present `coincidence' between the dark energy density and the neutrino
energy density can be obtained in our scenario even for static neutrino masses.


title: Cosmic Rays VIII

abstract: This paper has been withdrawn.


title: Cosmology with decaying tachyon matter

abstract:
  We investigate the case of a homogeneous tachyon field coupled to gravity in
a spatially flat Friedman-Robertson-Walker spacetime. Assuming the field
evolution to be exponentially decaying with time we solve the field equations
and show that, under certain conditions, the scale factor represents an
accelerating universe, following a phase of decelerated expansion. We make use
of a model of dark energy (with p=-\rho) and dark matter (p=0) where a single
scalar field (tachyon) governs the dynamics of both the dark components. We
show that this model fits the current supernova data as well as the canonical
\LambdaCDM model. We give the bounds on the parameters allowed by the current
data.


title: A substellar companion around the intermediate-mass giant star HD 11977

abstract:
  We report the discovery of a substellar companion to the intermediate-mass
star HD 11977 (G5 III). Radial velocities of this star have been monitored for
five years with FEROS at the 1.52-m ESO and later at the 2.2-m MPG/ESO
telescope in La Silla, Chile. Based on the collected data we calculated an
orbital solution with a period of P=711 days, a semi-amplitude of K1=105 m/s,
and an eccentricity of e=0.4. The period of the radial-velocity variation is
longer than that of the estimated stellar rotation, rendering it unlikely that
rotational modulation is the source of the variation in the radial velocity.
This hypothesis is supported by the absence of a correlation between stellar
activity indicators and radial-velocity variation. By determining a primary
stellar mass of Mstar=1.91 Msun, the best-fit minimum mass of the companion and
semi-major axis of the orbit are m2sini=6.54 Mjup and a2=1.93 AU, respectively.
An upper limit for the mass of the companion of m2 < 65.5 Mjup has been
calculated from Hipparcos astrometric measurements. Although the possibility of
a brown-dwarf companion cannot be excluded, HD 11977 B is one of the few planet
candidates detected around an intermediate-mass star. The progenitor
main-sequence star of HD 11977 is probably an A-type star. This discovery gives
an indirect evidence for planetary companions around early type main-sequence
stars.


title:
A library of high resolution synthetic stellar spectra from 300nm to 1.8
  micron with solar and alpha-enhanced composition

abstract:
  Libraries of stellar spectra are fundamental tools for the study of stellar
populations and both empirical and synthetic libraries have been used for this
purpose. In this paper, a new library of high resolution synthetic spectra is
presented, ranging from the near-ultraviolet (300nm) to the near-infrared
(1.8${\rm \mu}$m). The library spans all the stellar types that are relevant to
the integrated light of old and intermediate-age stellar populations in the
involved spectral region (spectral types F through M and all luminosity
classes). The grid was computed for metallicities ranging from [Fe/H] = --2.5
to +0.5, including both solar and $\alpha$-enhanced ([$\alpha$/Fe] = 0.4)
chemical compositions. The synthetic spectra are a good match to observations
of stars throughout the stellar parameter space encompassed by the library and
over the whole spectral region covered by the computations.


title: Evolution of X-ray emission from young massive star clusters

abstract:
  The evolution of X-ray emission from young massive star clusters is modeled,
taking into account the emission from the stars as well as from the cluster
wind. It is shown that the level and character of the soft (0.2-10 keV) X-ray
emission change drastically with cluster age and are tightly linked with
stellar evolution. Using the modern X-ray observations of massive stars we show
that the correlation between bolometric and X-ray luminosity known for single O
stars also holds for O+O and O+Wolf-Rayet (WR) binaries. The diffuse emission
originates from the cluster wind heated by the kinetic energy of stellar winds
and supernova explosions. To model the evolution of the cluster wind, the mass
and energy yields from a population synthesis are used as input to a
hydrodynamic model. It is shown that in a very young clusters the emission from
the cluster wind is low. When the cluster evolves, WR stars are formed. Their
strong stellar winds power an increasing X-ray emission of the cluster wind.
Subsequent supernova explosions pump the level of diffuse emission even higher.
Clusters at this evolutionary stage may have no X-ray bright stellar point
sources, but a relatively high level of diffuse emission. A supernova remnant
may become a dominant X-ray source, but only for a short time interval of a few
thousand years. We retrieve and analyse Chandra and XMM-Newton observations of
six massive star clusters located in the Large Magellanic Cloud. Our model
reproduces the observed diffuse and point-source emission from these LMC
clusters, as well as from the Galactic clusters Arches, Quintuplet and NGC
3603.


title:
VLTI/MIDI measurements of extended mid-infrared emission in the Galactic
  Center

abstract:
  We investigated with MIDI the extension of dusty mid-infrared excess sources
(IRS 1W, IRS 10W, IRS 2, IRS 8) in immediate vicinity to the black hole (BH) at
the GC. We derive 3$\sigma$ upper limits of the correlated fluxes of our target
sources which give direct constraints on the size of the emitting regions. Most
probably the emission originates from bow shocks generated by windy stars
ploughing through the dense matter of the Northern MiniSpiral.


title: Evolution of Field Dwarf Galaxies with GEMS

abstract:
  We present a study of the evolution of late-type field dwarfs over the last ~
1.9 Gyr, based on HST ACS observations carried out as part of the GEMS survey.
This study is amongst the first to probe the evolution of dwarfs over such a
large timescale. The comparison of structural properties, particularly size and
scale length, indicates that the dwarfs in the redshift range z ~ 0.01 to 0.15
(look-back times up to 1.9 Gyr) are more extended than local dwarfs. We argue
that this difference is due to the star formation activity becoming more
centrally concentrated in late-type dwarfs over the last ~ 1.9 Gyr. We discuss
several possible causes for this evolution. We also find a lack of blue compact
dwarfs in the GEMS sample and interpret this as indicative of the fact that
strong, centrally concentrated star formation is a feature of evolved dwarfs
that are entering their final stages of evolution.


title:
The photometric evolution of FU Orionis objects: disc instability and
  wind-envelope interaction

abstract:
  We present the results of a photometric monitoring campaign of three well
studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken
at Maidanak Observatory between 1981 and 2003. When combined with photometric
data in the literature, this database provides a valuable resource for
searching for short timescale variability - both periodic and aperiodic - as
well as for studying the secular evolution of these systems. In the case of
V1057 Cyg (which is the system exhibiting the largest changes in brightness
since it went into outburst) we compare the photometric data with time
dependent models. We show that prior to the end of the `plateau' stage in 1996,
the evolution of V1057 Cyg in the $V-(B-V)$ colour-magnitude diagram is well
represented by disc instability models in which the outburst is triggered by
some agent - such as an orbiting planet - in the inner disc. Following the end
of the plateau phase in 1996, the dimming and irregular variations are
consistent with occultation of the source by a variable dust screen, which has
previously been interpreted in terms of dust condensation events in the
observed disc wind. Here we instead suggest that this effect results from the
interaction between the wind and an infalling dusty envelope, the existence of
this envelope having been previously invoked in order to explain the mid
infrared emissio of FU Orionis systems. We discuss how this model may explain
some of the photometric and spectroscopic characteristics of FU Orionis systems
in general.


title:
On the nature of two low M-dot X-ray bursters: 1RXS J170854.4-321857 and
  1RXS J171824.2-402934

abstract:
  We carried out Chandra observations of two low-luminosity low-mass X-ray
binaries, 1RXS J170854.4-321857 and 1RXS J171824.2-402934, for which previously
single X-ray bursts had been detected with the Wide Field Cameras (WFCs) on
board BeppoSAX. Both were detected in our Chandra observations in an actively
accreting state three to eight years after the X-ray bursts, with 0.5-10 keV
luminosities between 5x10^34 and 2x10^36 erg/s. The apparently persistent
nature is remarkable for 1RXS J171824.2-402934 given its low luminosity of
0.001L_Edd. The persistence of both sources also distinguishes them from 5
other low-L bursters, which have also been seen during bursts with the WFCs but
were not detected during Chandra observations above a luminosity of 10^33
erg/s. Those are probably transient rather than persistent sources.


title: Magnetic turbulence in cool cores of galaxy clusters

abstract:
  We argue that the recently reported Kolmogorov-like magnetic turbulence
spectrum in the cool core of the Hydra A galaxy cluster can be understood by
kinetic energy injection by active galaxies that drives a turbulent non-helical
magnetic dynamo into its saturated state. Although dramatic differences exist
between small-scale dynamo scenarios, their saturated state is expected to be
similar, as we show for three scenarios: the flux rope dynamo, the fluctuation
dynamo, and the explosive dynamo. Based on those scenarios, we develop an
analytical model of the hydrodynamic and magnetic turbulence in cool cores. The
model implies magnetic field strengths that fit well with Faraday rotation
measurements and minimum energy estimates for the sample of cool core clusters
having such data available. Predictions for magnetic fields in clusters for
which the appropriate observational information is still missing, and for yet
unobserved quantities like the hydrodynamical turbulence velocity and
characteristic length-scale are provided. The underlying dynamo models suggest
magnetic intermittency and possibly a large-scale hydrodynamic viscosity. We
conclude that the success of the model to explain the field strength in cool
core clusters indicates that in general cluster magnetic fields directly
reflect hydrodynamical turbulence, also in clusters without cool cores.


title:
Observations Supporting the Existence of an Intrinsic Magnetic Moment
  Inside the Central Compact Object Within the Quasar Q0957+561

abstract:
  Recent auto-correlation and fluctuation analysis of time series data in the
brightness curves and micro-lensing size scales seen in Q0957+561 A,B has
produced important information about the existence and characteristic physical
dimensions of a new non-standard internal structure contained within this
quasar. We find that the new internal quasar structure, which we shall call the
Schild-Vakulik Structure, can be consistently explained in terms of a new class
of gravitationally collapsing solutions to the Einstein field equations which
describe highly redshifted, Eddington limited, Magnetospheric Eternally
Collapsing Objects (MECO) that contain intrinsic magnetic moments. Since
observation of the Schild-Vakulik structure within Q0957+561 implies that this
quasar contains an observable intrinsic magnetic moment, this represents strong
evidence that this quasar does not have an event horizon


title:
Large Scale Structure in Bekenstein's theory of relativistic Modified
  Newtonian Dynamics

abstract:
  A relativistic theory of modified gravity has been recently proposed by
Bekenstein. The tensor field in Einstein's theory of gravity is replaced by a
scalar, a vector, and a tensor field which interact in such a way to give
Modified Newtonian Dynamics (MOND) in the weak-field non-relativistic limit. We
study the evolution of the universe in such a theory, identifying its key
properties and comparing it with the standard cosmology obtained in Einstein
gravity. The evolution of the scalar field is akin to that of tracker
quintessence fields. We expand the theory to linear order to find the evolution
of perturbations on large scales. The impact on galaxy distributions and the
cosmic microwave background is calculated in detail. We show that it may be
possible to reproduce observations of the cosmic microwave background and
galaxy distributions with Bekenstein's theory of MOND.


title:
Effects of ion and electron correlations on neutrino scattering in the
  infall phase of a supernova

abstract:
  Many authors have used one-component plasma simulations in discussing the
role of ion-ion correlations in reducing neutrino opacities during the collapse
phase of a supernova. In a multicomponent plasma in which constituent ions have
even a small range of N/Z ratios neutrino opacities are much larger, in some
regions of parameters, than for the case of a one component plasma.


title: The Role of Magnetic Fields on Astrophysical Jets

abstract:
  Highly collimated supersonic jets and less collimated outflows are observed
to emerge from a wide variety of astrophysical objects. They are seen in young
stellar objects (YSOs), proto-planetary nebulae, compact objects (such as
galactic black holes or microquasars, and X-ray binary stars), and in the
nuclei of active galaxies (AGNs). Despite their different physical scales (in
size, velocity, and amount of energy transported), they have strong
morphological similarities. What is the universal mechanism that can explain
their origin? In this lecture, I briefly review the role that magnetic fields
seem to play on the formation, structure, and propagation of these jets.


title:
Seismic diagnostics of mixing beyond the convective core in intermediate
  mass main-sequence stars

abstract:
  We study prospects for seismic sounding the layer of a partial mixing above
the convective core in main-sequence stars with masses in the 1.2 -- 1.9 solar
mass range. There is an initial tendency to an increase of convective core mass
in such stars and this leads to ambiguities in modeling. Solar-like
oscillations are expected to be excited in such objects. Frequencies of such
oscillations provide diagnostics, which are sensitive to the structure of the
innermost part of the star and they are known as the small separations. We
construct evolutionary models of stars in this mass range assuming various
scenarios for element mixing, which includes formation of element abundance
jumps, as well as semiconvective and overshooting layers. We find that the
three point small separations employing frequencies of radial and dipole modes
provide the best probe of the element distribution above the convective core.
With expected accuracy of frequency measurement from the space experiments, a
discrimination between various scenarios should be possible.


title:
Internal Alignment of the Halos of Disk Galaxies in Cosmological
  Hydrodynamic Simulations

abstract:
  Seven cosmological hydrodynamic simulations of disk galaxy formation are
analyzed to determine the alignment of the disk within the dark matter halo and
the internal structure of the halo. We find that the orientation of the outer
halo, beyond ~0.1 r_vir, is unaffected by the presence of the disk. In
contrast, the inner halo is aligned such that the halo minor axis aligns with
the disk axis. The relative orientation of these two regions of the halo are
uncorrelated. The alignment of the disk and inner halo appears to take place
simultaneously through their joint evolution. The disconnect between these two
regions of the halo should be taken into account when modelling tidal streams
in the halos of disk galaxies and when calculating intrinsic alignments of disk
galaxies based on the properties of dark matter halos.


title:
The first chemical enrichment in the universe and the formation of hyper
  metal-poor stars

abstract:
  The recent discovery of a hyper metal-poor (HMP) star, whose metallicity Fe/H
is smaller than 1/100,000 of the solar ratio, together with one earlier HMP
star, has raised a challenging question if these HMP stars are the actual first
generation, low mass stars in the Universe. We argue that these HMP stars are
the second generation stars being formed from gases which were chemically
enriched by the first generation supernovae. The key to this solution is the
very unusual abundance patterns of these HMP stars with important similarities
and differences. We can reproduce these abundance features with the
core-collapse ``faint'' supernova models which undergo extensive matter mixing
and fallback during the explosion.


title: SSSPM J1549$-$3544 Is Not a White Dwarf

abstract:
  Spectroscopy and photometry demonstrate that SSSPM J1549$-$3544 is not a cool
white dwarf but a high velocity metal-poor halo star.


title: Discovery of X-ray Jets in the Microquasar H 1743-322

abstract:
  We report on the formation and evolution of two large-scale,
synchrotron-emitting jets from the black hole candidate H 1743-322 following
its reactivation in 2003. In November 2003 after the end of its 2003 outburst,
we noticed, in observations with the Australia Telescope Compact Array, the
presence of a new and variable radio source about 4.6" to the East of H
1743-322, that was later found to move away from H 1743-322. In February 2004,
we detected a radio source to the West of H 1743-322, symmetrically placed
relative to the Eastern jet. In 2004, follow-up X-ray observations with {\em
Chandra} led to the discovery of X-ray emission associated with the two radio
sources. This likely indicates that we are witnessing the interaction of
relativistic jets from H 1743-322 with the interstellar medium causing in-situ
particle acceleration. The spectral energy distribution of the jets during the
decay phase is consistent with a classical synchrotron spectrum of a single
electron distribution from radio up to X-rays, implying the production of very
high energy ($>$ 10 TeV) particles in those jets. We discuss the jet
kinematics, highlighting the presence of a significantly relativistic flow in H
1743-322 almost a year after the ejection event.


title: Thermal Evolution of Supernova Iron in Elliptical Galaxies

abstract:
  In explaining the relative metal abundances observed in galaxy groups and
clusters, it is generally assumed that all metals created by supernovae are
present either in visible stars or the hot gas. We discuss here the possibility
that some of the iron expelled into the hot gas by Type Ia supernovae may have
radiatively cooled, avoiding detection by X-ray and optical observers.
Hydrodynamic models of Type Ia explosions in the hot gas inside elliptical
galaxies result in a gas of nearly pure iron that is several times hotter than
the local interstellar gas. We describe the subsequent thermal evolution of the
iron-rich gas as it radiates and thermally mixes with the surrounding gas.
There is a critical time by which the iron ions must mix into the ambient gas
to avoid rapid radiative cooling. We find that successful mixing is possible if
the iron ions diffuse with large mean free paths, as in an unmagnetized plasma.
However, in microgauss fields the Larmor radii of the iron ions are
exceptionally small, so the field geometry must be highly tangled or radial to
allow the iron to mix by diffusion faster than it cools by radiative losses.
The possibility that some of the supernova iron cools cannot be easily
discounted.


title:
Spectroscopy and Stellar Populations of Star-forming Galaxies at z~3 in
  the Hubble Deep Field - South

abstract:
  We present results of VLT/FORS2 spectroscopy of galaxies at z~3 in the Hubble
Deep Field-South (HDF-S). A sample of galaxies was drawn from the photo-z
catalogue based on the HST/WFPC2 optical images and the deep near-infrared
images obtained with VLT/ISAAC as a part of the FIRES project. We selected
galaxies with photometric redshift between 2.5 and 4. Most of the selected
galaxies are bright in rest-frame UV wavelengths and satisfy color selection
criteria of Lyman break galaxies (LBGs) at z~3. The number of target galaxies
with I(AB)<25.0 was 15. We identified new 5 firm and 2 probable redshifts in
addition to confirmations of previously known 6 galaxies at z~3. We found 6
among these 13 galaxies lie at a quite narrow redshift range at z = 2.80+-0.01.
We examined stellar populations of the galaxies with spectroscopic redshifts
through comparisons of their optical and near-IR photometry data with template
spectra generated by a population synthesis code. The ages from the onset of
star formation for these star-forming galaxies with I<=25.0 are typically
50-200 Myr, and their stellar masses are between (0.5-5) x 10^10 M_sun,
consistent with previous studies. We also compared these SED fitting results
with those for distant red galaxies (DRGs) at z>2 discovered by FIRES. DRGs
have larger stellar masses, larger dust attenuation than our UV-luminous LBG
sample, and their star formation rates are often comparable to LBGs. These
trends suggest that majority of DRGs are indeed the most massive systems at the
redshift and are still in the active star-forming phase. Unless the number
density of DRGs is much smaller than LBGs, estimates based on UV selected
sample could miss substantial part of stellar mass density at z~3.


title:
Kelvin Helmholtz Instability and Circulation Transfer at an
  Isotropic-Anisotropic Superfluid Interface in a Neutron Star

abstract:
  A recent laboratory experiment (Blaauwgeers et al. 2003) suggests that a
Kelvin-Helmholtz (KH) instability at the interface between two superfluids, one
rotating and anisotropic, the other stationary and isotropic, may trigger
sudden spin-up of the stationary superfluid. This result suggests that a KH
instability at the crust-core ($^1S_0$-$^3P_2$-superfluid) boundary of a
neutron star may provide a trigger mechanism for pulsar glitches. We calculate
the dispersion relation of the KH instability involving two different
superfluids including the normal fluid components and their effects on
stability, particularly entropy transport. We show that an entropy difference
between the core and crust superfluids reduces the threshold differential shear
velocity and threshold crust-core density ratio. We evaluate the wavelength of
maximum growth of the instability for neutron star parameters and find the
resultant circulation transfer to be within the range observed in pulsar
glitches.


title:
The Growth of the Local Void and the Origin of the Local Velocity
  Anomaly

abstract:
  The Local Void is the nearest void from us and is thought to be playing an
important role in the kinematics of the local universe, especially as one of
the suspected source of the motion of the Local Group. The imbalance between
the mass in the Local Void region and that contained in the concentration at
the opposite side might contribute to the velocity of the Local group
perpendicular to the Supergalactic plane, and this would be a prototype of the
evolution of the large-scale structure. The proximity of the Local Void
provides us the exclusive opportunity to investigate the kinematics around a
void. Here we report the results of our observational study of the peculiar
velocities of about 40 galaxies at the far-side of the Local Void, using the
near-infrared Tully-Fisher relation. The galaxies at the boundary of the void
shows an excess of receding motion, suggesting the expansion of the Local Void.
We examined the effect of selection biases on the peculiar velocity
distribution, and concluded that the excess of receding motion could not fully
attribute to selection biases.


title:
Baryogenesis and CP-Violating Domain Walls in the Background of a
  Magnetic Field

abstract:
  Within the domain wall-mediated electroweak baryogenesis, we study fermion
scattering off a CP-violating wall in the background of an uniform magnetic
field. In particular, we calculate the asymmetry between the reflection
coefficients for right-handed and left-handed chiral fermions, \Delta R = R_{R
\to L} - R_{L \to R}, which is of relevance to non local baryogenesis
mechanisms.


title:
A large spin-up rate measured with INTEGRAL in the High Mass X-ray
  Binary Pulsar SAXJ2103.5+4545

abstract:
  The High Mass X-ray Binary Pulsar SAXJ2103.5+4545 has been observed with
INTEGRAL several times during the last outburst in 2002-2004. We report a
comprehensive study of all INTEGRAL observations, allowing a study of the pulse
period evolution during the recent outburst. We measured a very rapid spin-up
episode, lasting 130days, which decreased the pulse period by 1.8s. The spin-up
rate, pdot=-1.5e-7 s/s, is the largest ever measured for SAXJ2103.5+4545, and
it is among the fastest for an accreting pulsar. The pulse profile shows
evidence for temporal variability, apparently not related to the source flux or
to the orbital phase. The X-ray spectrum is hard and there is significant
emission up to 150keV. A new derivation of the orbital period, based on RXTE
data, is also reported.


title: The effect of neutrinos on the initial fireballs in gamma-ray bursts

abstract:
  We investigate the fate of very compact, sudden energy depositions that may
lie at the origin of gamma-ray bursts. Following on from the work of Cavallo
and Rees (1978), we take account of the much higher energies now believed to be
involved. The main effect of this is that thermal neutrinos are present and
energetically important. We show that these may provide sufficient cooling to
tap most of the explosion energy. However, at the extreme energies usually
invoked for gamma-ray bursts, the neutrino opacity suffices to prevent dramatic
losses, provided that the heating process is sufficiently fast. In a generic
case, a few tens of percent of the initial fireball energy will escape as an
isotropic millisecond burst of thermal neutrinos with a temperature of about 60
MeV, which is detectable for nearby gamma-ray bursts and hypernovae. For
parameters we find most likely for gamma-ray burst fireballs, the dominant
processes are purely leptonic, and thus the baryon loading of the fireball does
not affect our conclusions.


title: The first near infrared detection of XTE J1118+480 in quiescence

abstract:
  We report the first quiescent detection of KV UMa, the optical counterpart of
XTE J1118+480 at near infrared. The observed magnitudes and colours are
consistent with a K7-M0 V star, at the distance 1.4 +/- 0.2 kpc. The light
curve shows strong orbital modulation with possible contamination from a
superhump detected in the quiescent optical light curves.