title: The earliest spectroscopy of the GRB 030329 afterglow with 6-m telescope

abstract:
  The earliest BTA (SAO RAS 6-m telescope) spectroscopic observations of the
GRB 030329 optical transient (OT) are presented, which almost coincide in time
with the "first break" ($t\sim 0.5$ day after the GRB) of the OT light curve.
The beginning of spectral changes are seen as early as $\sim 10-12$ hours after
the GRB. So, the onset of the spectral changes for $t<1$ day indicates that the
contribution from Type Ic supernova (SN) into the OT optical flux can be
detected earlier. The properties of early spectra of GRB 030329/SN 2003dh can
be consistent with a shock moving into a stellar wind formed from the pre-SN.
Such a behavior (similar to that near the UV shock breakout in SNe) can be
explained by the existence of a dense matter in the immediate surroundings of
massive stellar GRB/SN progenitor). The urgency is emphasized of observation of
early GRB/SN spectra for solving a question that is essential for understanding
GRB physical mechanism: {\it Do all} long-duration gamma-ray bursts are caused
by (or physically connected to) {\it ordinary} core-collapse supernovae? If
clear association of normal/ordinary core-collapse SNe (SN Ib/c, and others SN
types) and GRBs would be revealed in numbers of cases, we may have strong
observational limits for gamma-ray beaming and for real energetics of the GRB
sources.


title:
Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV.
  Fine Scale Structure

abstract:
  We have used VLBA fringe visibility data obtained at 15 GHz to examine the
compact structure in 250 extragalactic radio sources. For 171 sources in our
sample, more than half of the total flux density seen by the VLBA remains
unresolved on the longest baselines. There are 163 sources in our list with a
median correlated flux density at 15 GHz in excess of 0.5 Jy on the longest
baselines. For about 60% of the sources, we have at least one observation in
which the core component appears unresolved (generally smaller than 0.05 mas)
in one direction, usually transverse to the direction into which the jet
extends. BL Lacs are on average more compact than quasars, while active
galaxies are on average less compact. Also, in an active galaxy the
sub-milliarcsecond core component tends to be less dominant. IDV sources
typically have a more compact, more core-dominated structure on
sub-milliarcsecond scales than non-IDV sources, and sources with a greater
amplitude of intra-day variations tend to have a greater unresolved VLBA flux
density. The objects known to be GeV gamma-ray loud appear to have a more
compact VLBA structure than the other sources in our sample. This suggests that
the mechanisms for the production of gamma-ray emission and for the generation
of compact radio synchrotron emitting features are related. The brightness
temperature estimates and lower limits for the cores in our sample typically
range between 10^11 and 10^13 K, but they extend up to 5x10^13 K, apparently in
excess of the equipartition brightness temperature, or the inverse Compton
limit for stationary synchrotron sources. The largest component speeds are
observed in radio sources with high observed brightness temperatures, as would
be expected from relativistic beaming (abridged).


title:
Constraining fundamental stellar parameters using seismology.
  Application to Alpha Centauri AB

abstract:
  We apply the Levenberg-Marquardt minimization algorithm to seismic and
classical observables of the Alpha Cen binary system in order to derive the
fundamental parameters of Alpha Cen A+B and to analyze the dependence of these
parameters on the chosen observables, on their uncertainty and on the physics
used in stellar modelling. The seismological data are those by Bouchy & Carrier
(2002) for Alpha Cen A, and those by Carrier & Bourban (2003) for Alpha Cen B.
We show that while the fundamental stellar parameters do not depend on the
treatment of convection adopted (Mixing Length Theory -- MLT -- or ``Full
Spectrum of Turbulence'' -- FST), the age of the system depends on the
inclusion of gravitational settling, and is deeply biased by the small
frequency separation of component B.
  We try to answer the question of the universality of the mixing length
parameter, and we find a statistically reliable dependence of the
alpha--parameter on the HR diagram location (with a trend similar to the one
predicted by Ludwig et al.1999).
  We propose the frequency separation ratios introduced by Roxburgh &
Voronstsov (2003) as better observables to determine the fundamental stellar
parameters, and to use the large frequency separation and frequencies to
extract information about the stellar structure. The effects of diffusion and
equation of state on the oscillation frequencies are also studied, but present
seismic data do not allow their detection.


title: The pulsed X-ray light curves of the isolated neutron star RBS1223

abstract:
  We present a multi-epoch spectral and timing analysis of the isolated neutron
star RBS1223. New XMM-Newton data obtained in January 2004 confirm the spin
period to be twice as long as previously thought, P_spin = 10.31 s. The
combined ROSAT, Chandra, XMM-Newton data (6 epochs) give, contrary to earlier
findings, no clear indication of a spin evolution of the neutron star. The
X-ray light curves are double-humped with pronounced hardness ratio variations
suggesting an inhomogeneous surface temperature with two spots separated by
about ~160 degr. The sharpness of the two humps suggests a mildly relativistic
star with a ratio between R_ns, the neutron star radius at source, and r_S, the
Schwarzschild-radius, of R_ns/r_S > 3.5. Assuming Planckian energy
distributions as local radiation sources, light curves were synthesized which
were found to be in overall qualitative agreement with observed light curves in
two different energy bands. The temperature distribution used was based on the
crustal field models by Geppert et al. (2004) for a central temperature of T_c
= 10^8 K and an external dipolar field of B ~ 10^{13} G. This gives a mean
atmospheric temperature of 55 eV. A much simpler model with two homogeneous
spots with T_\infty = 92 eV, and 84 eV, and a cold rest star, T_star,\infty <
45 eV, invisible at X-ray wavelengths, was found to be similarly successful.
The new temperature determination and the new dot(P)_{spin} suggest that the
star is older than previously thought, T \simeq 10^(5..6) yrs. The
model-dependent distance to RBS1223 is estimated between 76 pc and 380 pc (for
R_ns = 12 km).


title: The 3-D Structure of the Helix Nebula

abstract:
  The 3-D structure of the Helix Nebula has been addressed multiple times and
is slowly yielding to application of monochromatic emission line imaging, high
resolution spectroscopy, and photoionization theory. The inner structure of the
nebula is a toroidal disk filled with doubly ionized helium and is ionization
bounded, with an extended vertical component resembling the structure of
numerous bipolar nebulae. The outer structure is less well defined, with one
construction being that there is an open-center outer-disk that is nearly
perpendicular to the inner-disk and an alternate construction that explains the
features seen just outside the inner-disk as being the result of the observer's
line of sight passing through extended lobes perpendicular to the inner-disk. A
definitive model awaits thorough velocity mapping in the major diagnostic
emission lines. However, even our well-defined knowledge of the inner-disk
defies explanation by the simplest application of the broadly accepted two-wind
model for the formation of PN.


title: A dearth of planetary transits in the direction of NGC 6940

abstract:
  We present results of our survey for planetary transits in the field of NGC
6940. We think nearly all of our observed stars are field stars. We have
obtained high precision (3-10 millimags at the bright end) photometric
observations of 50,000 stars spanning 18 nights in an attempt to identify low
amplitude and short period transit events. We have used a matched filter
analysis to identify 14 stars that show multiple events, and four stars that
show single transits. Of these 18 candidates, we have identified two that
should be further researched. However, none of the candidates are convincing
hot Jupiters.


title: A tiny Galactic dust cloud projected onto NGC 3269?

abstract:
  We report on new observations obtained with the Magellan Clay-telescope of a
tiny dust patch in the Sa-galaxy NGC 3269 in the Antlia galaxy cluster. It has
already been suspected to be a projected Galactic foreground cloud. In this
case a size of about 4 arcsec and a maximum absorption of ~1 mag in the B-band
would make it unique so far. We present further evidence for its Galactic
nature from imaging under excellent seeing conditions (0.3-0.6 arcsec). This
dust cloud could be the first optically identified counterpart of a new type of
molecular cloud recently discovered by Heithausen (2004).


title:
Ly-alpha and UV emission from high-redshift GRB hosts: To what extent do
  GRBs trace star formation?

abstract:
  We report the result of a search for Ly-alpha emission from the host galaxies
of the gamma-ray bursts (GRBs) 030226 (z = 1.986), 021004 (z = 2.335) and
020124 (z = 3.198). We find that the host galaxy of GRB 021004 is an extended
(around 8 kpc) strong Ly-alpha emitter with a restframe equivalent width (EW)
of 68^{+12}_{-11} AA, and a star-formation rate of 10.6 +/- 2.0 M_sun/yr. We do
not detect the hosts of GRB 030226 and GRB 020124, but the upper limits on
their Ly-alpha fluxes do not rule out large restframe EWs. In the fields of GRB
021004 and GRB 030226 we find seven and five other galaxies, respectively, with
excess emission in the narrow-band filter. These galaxies are candidate
Ly-alpha emitting galaxies in the environment of the host galaxies. We have
also compiled a list of all z > 2 GRB hosts, and demonstrate that a scenario
where they trace star formation in an unbiased way is compatible with current
observational constraints. Fitting the z=3 luminosity function (LF) under this
assumption, results in a characteristic luminosity of R* = 24.6 and a faint end
slope of alpha = -1.55, consistent with the LF measured for Lyman-break
galaxies.


title:
Low T/|W| dynamical instability in differentially rotating stars:
  Diagnosis with canonical angular momentum

abstract:
  We study the nature of non-axisymmetric dynamical instabilities in
differentially rotating stars with both linear eigenmode analysis and
hydrodynamic simulations in Newtonian gravity. We especially investigate the
following three types of instability; the one-armed spiral instability, the low
T/|W| bar instability, and the high T/|W| bar instability, where T is the
rotational kinetic energy and W is the gravitational potential energy. The
nature of the dynamical instabilities is clarified by using a canonical angular
momentum as a diagnostic. We find that the one-armed spiral and the low T/|W|
bar instabilities occur around the corotation radius, and they grow through the
inflow of canonical angular momentum around the corotation radius. The result
is a clear contrast to that of a classical dynamical bar instability in high
T/|W|. We also discuss the feature of gravitational waves generated from these
three types of instability.


title: The Formation of Fossil Galaxy Groups in the hierarchical Universe

abstract:
  We use a set of twelve high-resolution N-body/hydrodynamical simulations in
the $\Lambda$CDM cosmology to investigate the origin and formation rate of
fossil groups (FGs), which are X-ray bright galaxy groups dominated by a large
elliptical galaxy, with the second brightest galaxy being at least two
magnitudes fainter. The simulations invoke star formation, chemical evolution
with non-instantaneous recycling, metal dependent radiative cooling, strong
star burst driven galactic super winds, effects of a meta-galactic UV field and
full stellar population synthesis. We find an interesting correlation between
the magnitude gap between the first and second brightest galaxy and the
formation time of the group. It is found that FGs have assembled half of their
final dark matter mass already at $z\ga1$, and subsequently typically grow by
minor merging only, wheras non-FGs on average form later. The early assembly of
FGs leaves sufficient time for galaxies of $L \sim L_*$ to merge into the
central one by dynamical friction, resulting in the large magnitude gap at
$z=0$. A fraction of 33$\pm$16% of the groups simulated are found to be fossil,
whereas the observational estimate is $\sim$10-20%. The FGs are found to be
X-ray over-luminous relative to non-FGs of the same optical luminosity, in
qualitative agreement with observations. Finally, from a dynamical friction
analysis is found that only because infall of $L \sim L_*$ galaxies happens
along filaments with small impact parameters do FGs exist at all.


title:
Gravitational Wave Astrometry for Rapidly Rotating Neutron Stars and
  Estimation of Their Distances

abstract:
  We discuss an astrometric timing effect on data analysis of continuous
gravitational waves from rapidly rotating isolated neutron stars. Special
attention is directed to the possibility of determining their distances by
measuring the curvature of the wave fronts. We predict that if continuous
gravitational waves from an unknown neutron star with a stable rotation are
detected around 1kHz within 1/3yr by initial LIGO detectors and the ellipticity
parameter epsilon is smaller than 10^{-6}, the distance r to the source can be
estimated with relative error \Delta r/r of \sim 10% by using the broad band
configuration of advanced LIGO detectors over 3 years. By combining the
observed amplitude of the waves with the estimated distance, information on the
parameter $\epsilon$ can be obtained purely through gravitational wave
measurements.


title:
Constraints from Galaxy-AGN Clustering on the Correlation between Galaxy
  and Black Hole Mass at Redshifts 2<Z<3

abstract:
  We use the clustering of galaxies around distant active-galactic nuclei to
derive an estimate of the relationship between galaxy and black hole mass that
obtained during the ancient quasar epoch, at redshifts 2 <~ z <~ 3, when giant
black holes accreted much of their mass. Neither the mean relationship nor its
scatter differs significantly from what is observed in the local universe, at
least over the ranges of apparent magnitude (16 <~ G_AB <~ 26) and black-hole
mass (10^6 <~ M_BH/M_sun <~ 10^10.5) that we are able to probe.


title: TeV neutrinos from microquasars in compact massive binaries

abstract:
  We consider a compact binary system in which a Wolf-Rayet star supplies
matter onto a stellar mass black hole or a neutron star. This matter forms an
accretion disk which ejects a jet as observed in Galactic microquasars. A part
of the jet kinetic energy, typically 10%, can be transfered to relativistic
nuclei. These nuclei lose nucleons as a result of photo-disintegration process
in collisions with thermal photons from the accretion disk and the massive
star. Due to the head on photon-nucleus collisions most of neutrons released
from nuclei move towards the surface of the accretion disk and/or the massive
star producing neutrinos in collisions with the matter. We calculate the
spectra of muon neutrinos and expected neutrino event rates in a 1 km^2
neutrino detector of the IceCube type from a microquasar inside our Galaxy
applying, as an example, the parameters of the Cyg X-3 binary system, provided
that nuclei are accelerated to the Lorentz factors above 10^6 with the power
law spectrum with an index close to 2.


title: Fossil records of cosmic reionization in galactic stellar halos

abstract:
  Galactic stellar halos have long been considered to contain fossil
information on early dynamical and chemical evolution of galaxies. We propose
that the surface brightness distributions of old stellar halos contain the
influence of reionization on early formation histories of galaxies. By assuming
that reionization significantly suppresses star formation in small subgalactic
clumps virialized after reionization redshift ($z_{\rm reion}$), we first
numerically investigate how structural and kinematical properties of stellar
halos formed from merging of these subgalactic clumps depend on $z_{\rm
reion}$. We then discuss what observable properties of galactic stellar halos
offer us the fossil records of reionization influence on hierarchical formation
of halos based on the current results of numerical simulations. We particularly
suggest that both the half-light radius of stellar halos and the slope of their
surface brightness profile contain useful information on when star formation in
subgalactic clumps were significantly influenced by reionization. By using the
simulated surface brightness distributions of galactic stellar halos for models
with different $z_{\rm reion}$, we also discuss how wide-field imaging studies
of extragalactic halos will help us to elucidate the epoch of cosmic
reionization.


title: XMM-Newton observations of AM CVn binaries

abstract:
  We present the results of XMM-Newton observations of four AM CVn systems --
AM CVn, CR Boo, HP Lib and GP Com. Their light curves show very different
characteristics. The X-ray light curves show no coherent pulsations, suggesting
the accreting white dwarfs have relatively low magnetic field strengths. Their
spectra were best modelled using a multi-temperature emission model and a
strong UV component. We find that CR Boo and HP Lib have X-ray spectra with
abundances consistent with relatively low temperature CNO processed material,
while AM CVn and GP Com show an enhancement of nitrogen. A large fraction of
the accretion luminosity is emitted in the UV. We determine accretion
luminosities of ~1.6x10^{33} ergs/s and 1.7x10^{31} ergs/s for AM CVn and GP
Com respectively. Comparing the implied mass transfer rates with that derived
using model fits to optical and UV spectra, we find evidence that in the case
of AM CVn, we do not detect a significant proportion of the accretion energy.
This missing component could be lost in the form of a wind.


title:
Flux and field line conservation in 3--D nonideal MHD flows: Remarks
  about criteria for 3--D reconnection without magnetic neutral points

abstract:
  We make some remarks on reconnection in plasmas and want to present some
calculations related to the problem of finding velocity fields which conserve
magnetic flux or at least magnetic field lines. Hereby we start from views and
definitions of ideal and non-ideal flows on one hand, and of reconnective and
non-reconnective plasma dynamics on the other hand. Our considerations give
additional insights into the discussion on violations of the frozen--in field
concept which started recently with the papers by Baranov & Fahr (2003a;
2003b). We find a correlation between the nonidealness which is given by a
generalized form of the Ohm's law and a general transporting velocity, which is
field line conserving.


title:
Neutrino masses and the dark energy equation of state - relaxing the
  cosmological neutrino mass bound

abstract:
  Cosmology at present provides the nominally strongest constraint on the
masses of standard model neutrinos. However, this constraint extremely
dependent on the nature of the dark energy component of the Universe. When the
dark energy equation of state parameter is taken as a free (but constant)
parameter, the neutrino mass bound is sum m_nu < 1.48 eV (95% C.L.), compared
with sum m_nu < 0.65 eV (95% C.L.) in the standard model where the dark energy
is in the form of a cosmological constant. This has important consequences for
future experiments aimed at the direct measurement of neutrino masses. We also
discuss prospects for future cosmological measurements of neutrino masses.


title: Inflation with violation of the null energy condition

abstract:
  Inflation may have been driven by a component which violated the Null-Energy
Condition, thereby leading to {\it super inflation}. We provide the formalism
to study cosmological perturbations when such a component is described by a
scalar field with arbitrary Lagrangian. Since the background curvature grows
with time, gravitational waves always have a blue spectrum. Scalar
perturbations may also have a blue spectrum, {\em albeit} in single field
models. We apply our formalism to the case of phantom inflation with an
exponential potential (whose pole-like inflationary stage is an attractor for
inhomogeneous cosmological models for any value of the potential slope). We
finally compare the predictions of super inflation with those of standard
inflation stressing the role of gravitational waves.


title: Reconnection at the Heliopause

abstract:
  In this MHD-model of the heliosphere, we assume a Parker-type flow, and a
Parker-type spiral magnetic field, which is extrapolated further downstream
from the termination shock to the heliopause. We raise the question whether the
heliopause nose region may be leaky with respect to fields and plasmas due to
nonideal plasma dynamics, implying a breakdown of the magnetic barrier. We
analyse some simple scenarios to find reconnection rates and circumstances,
under which the heliosphere can be an "open" or a "closed" magnetosphere. We do
not pretend to offer a complete solution for the heliosphere, on the basis of
nonideal MHD theory, but present a prescription to find such a solution on the
basis of potential fields including the knowledge of neutral points. As an
example we imitate the Parker spiral as a monopole with a superposition of
homogeneous asymptotical boundary conditions. We use this toy model for x < -R
where R = 100 AU is the distance of the termination shock to describe the
situation in the nose region of the heliopause.


title:
2D stationary resistive MHD flows: borderline to magnetic reconnection
  solutions

abstract:
  We present the basic equations for stationary, incompressible resistive MHD
flows in two dimensions. This leads to a system of differential equations for
two flux functions, one elliptic partial differential equation
(Grad-Shafranov-like) for the magnetic flux function and one for the stream
function of the flow. In these equations two potentials appear: one potential
is a generalized pressure. The second potential couples the magnetic and the
flow shear components of the system. With the restriction to flux or at least
line conserving flows one has to solve a modified Ohm's law. For the two
dimensional case these are two coupled differential equations, which represent
the borderline between the resistive but flux conserving (or line conserving)
case, and that of reconnective solutions. We discuss some simplified solutions
of these equations.


title: Pulsars as Tools for Fundamental Physics and Astrophysics

abstract:
  The sheer number of pulsars discovered by the SKA, in combination with the
exceptional timing precision it can provide, will revolutionize the field of
pulsar astrophysics. The SKA will provide a complete census of pulsars in both
the Galaxy and in Galactic globular clusters that can be used to provide a
detailed map of the electron density and magnetic fields, the dynamics of the
systems, and their evolutionary histories. This complete census will provide
examples of nearly every possible outcome of the evolution of massive stars,
including the discovery of very exotic systems such as pulsar black-hole
systems and sub-millisecond pulsars, if they exist. These exotic systems will
allow unique tests of the strong field limit of relativistic gravity and the
equation of state at extreme densities. Masses of pulsars and their binary
companions -- planets, white dwarfs, other neutron stars, and black holes --
will be determined to $\sim 1$% for hundreds of objects. With the SKA we can
discover and time highly-stable millisecond pulsars that comprise a
pulsar-timing array for the detection of low-frequency gravitational waves. The
SKA will also provide partial censuses of nearby galaxies through periodicity
and single-pulse detections, yielding important information on the
intergalactic medium.


title:
Elastic alpha-scattering of 112Sn and 124Sn at astrophysically relevant
  energies

abstract:
  The cross sections for the elastic scattering reactions
{112,124}Sn(a,a){112,124}Sn at energies above and below the Coulomb barrier are
presented and compared to predictions for global alpha-nucleus potentials. The
high precision of the new data allows a study of the global alpha-nucleus
potentials at both the proton and neutron-rich sides of an isotopic chain. In
addition, local alpha-nucleus potentials have been extracted for both nuclei,
and used to reproduce elastic scattering data at higher energies. Predictions
from the capture cross section of the reaction 112Sn(a,g)116Te at
astrophysically relevant energies are presented and compared to experimental
data.


title: Iron Needles in Supernova Remnants?

abstract:
  It has been suggested by Dwek (2004) that iron needles could explain the
submillimetre emission from the Cas A supernova remnant (SNR) with only a very
small total mass. We investigate whether a similar model holds for the Kepler
supernova remnant, and find that its emission could indeed be explained by a
dust mass of less than 10^-2 M_sun dependent on the axial ratio (l/a) of the
needles - which we constrain to be less than 700. But the implied needle model
for Kepler is inconsistent with that suggested for Cas A since either the
needles would have to have a resistivity one or two orders of magnitude greater
than those in Cas A or the electron density in Kepler's shocked plasma must be
40 times greater than suggested by X-ray observations. An additional problem
with the needle model is that the implied thickness of the needles seems to be
implausibly small, if the emission properties are calculated under the usual
approximations.


title:
An analytical description of the disruption of star clusters in tidal
  fields with an application to Galactic open clusters

abstract:
  We present a simple analytical description of the disruption of star clusters
in a tidal field, which agrees excellently with detailed N-body simulations.
The analytic expression can be used to predict the mass and age histograms of
surviving clusters for any cluster initial mass function and any cluster
formation history. The method is applied to open clusters in the solar
neighbourhood, based on the new cluster sample of Kharchenko et al. From a
comparison between the observed and predicted age distributions in the age
range between 10 Myr to 3 Gyr we find the following results: (1) The disruption
time of a 10^4 M_sun cluster in the solar neighbourhood is about 1.3+/-0.5 Gyr.
This is a factor 5 shorter than derived from N-body simulations of clusters in
the tidal field of the galaxy. (2) The present starformation rate in bound
clusters within 600 pc from the Sun is 5.9+/-0.8 * 10^2 M_sun / Myr, which
corresponds to a surface star formation rate in bound clusters of 5.2+/-0.7
10^(-10) M_sun/yr/pc^2. (3) The age distribution of open clusters shows a bump
between 0.26 and 0.6 Gyr when the cluster formation rate was 2.5 times higher
than before and after. (4) The present star formation rate in bound clusters is
half as small as that derived from the study of embedded clusters. The
difference suggests that half of the clusters in the solar neighbourhood become
unbound within 10 Myr. (5) The most massive clusters within 600 pc had an
initial mass of 3*10^4 M_sun. This is in agreement with the statistically
expected value based on a cluster initial mass function with a slope of -2,
even if the physical upper mass limit is as high as 10^6 M_sun.


title: Second order perturbation theory for spin-orbit resonances

abstract:
  We implement Lie transform perturbation theory to second order for the planar
spin-orbit problem. The perturbation parameter is the asphericity of the body,
with the orbital eccentricity entering as an additional parameter. We study
first and second order resonances for different values of these parameters. For
nearly spherical bodies like Mercury and the Moon first order perturbation
theory is adequate, whereas for highly aspherical bodies like Hyperion the spin
is mostly chaotic and perturbation theory is of limited use. However, in
between, we identify a parameter range where second order perturbation theory
is useful and where as yet unidentified objects may be in second order
resonances.


title: The XO Project: Searching for Transiting Extra-solar Planet Candidates

abstract:
  The XO project's first objective is to find hot Jupiters transiting bright
stars, i.e. V < 12, by precision differential photometry. Two XO cameras have
been operating since September 2003 on the 10,000-foot Haleakala summit on
Maui. Each XO camera consists of a 200-mm f/1.8 lens coupled to a 1024x1024
pixel, thinned CCD operated by drift scanning. In its first year of routine
operation, XO has observed 6.6% of the sky, within six 7 deg-wide strips
scanned from 0 deg to +63 deg of declination and centered at RA=0, 4, 8, 12,
16, and 20 hours. Autonomously operating, XO records 1 billion pixels per clear
night, calibrates them photometrically and astrometrically, performs aperture
photometry, archives the pixel data and transmits the photometric data to STScI
for further analysis. From the first year of operation, the resulting database
consists of photometry of 100,000 stars at more than 1000 epochs per star with
differential photometric precision better than 1% per epoch. Analysis of the
light curves of those stars produces transiting-planet candidates requiring
detailed follow up, described elsewhere, culminating in spectroscopy to measure
radial-velocity variation in order to differentiate genuine planets from the
more numerous impostors, primarily eclipsing binary and multiple stars.


title:
Statistical Mechanics of the self-gravitating gas: thermodynamic limit,
  phase diagrams and fractal structures

abstract:
  We provide a complete picture to the self-gravitating non-relativistic gas at
thermal equilibrium using Monte Carlo simulations, analytic mean field methods
(MF) and low density expansions. The system is shown to possess an infinite
volume limit in the grand canonical (GCE), canonical (CE) and microcanonical
(MCE) ensembles when (N, V) -> infty, keeping N/V^{1/3} fixed. We compute the
equation of state (we do not assume it as is customary in hydrodynamics), as
well as the energy, free energy, entropy, chemical potential, specific heats,
compressibilities and speed of sound; we analyze their properties, signs and
singularities. All physical quantities turn out to depend on a single variable
eta = G m^2 N /[V^{1/3} T} that is kept fixed in the N -> infty and V -> infty
limit. The system is in a gaseous phase for eta < eta_T and collapses into a
dense object for eta > eta_T in the CE with the pressure becoming large and
negative. At eta \simeq eta_T the isothermal compressibility diverges and the
gas collapses. Our Monte Carlo simulations yield eta_T \simeq 1.515. We find
that PV/[NT] = f(eta). The function f(eta) has a second Riemann sheet which is
only physically realized in the MCE. In the MCE, the collapse phase transition
takes place in this second sheet near eta_{MC} = 1.26 and the pressure and
temperature are larger in the collapsed phase than in the gaseous phase. Both
collapse phase transitions (in the CE and in the MCE) are of zeroth order since
the Gibbs free energy has a jump at the transitions.

categories: astro-ph cond-mat.stat-mech gr-qc hep-th


title:
X-Ray Flares of Sun-Like Young Stellar Objects and Their Effects on
  Protoplanetary Disks

abstract:
  Astronomical observations of flares from analogs of the early Sun have the
potential to give critical insights into the high energy irradiation
environment of protoplanetary disks. Solar-mass young stellar objects are
significantly more X-ray luminous than the typical low-mass T Tauri star. They
undergo frequent strong flaring on a several day time scale. Very powerful
flares also occur, but on a longer time frame. The hard X-ray spectrum of these
stars become even harder during flaring. The X-rays from these sun-like young
stellar objects have the potential to ionize circumstellar material out to
large distances. Three specific illustrations are given of the effects of the
X-rays: The physics and chemistry of the atmospheres of the inner accretion
disks; the ionization level at the disk midplane, important for the viability
of the magnetorotational instability; and the nuclear fluence in the
irradiation zone just interior to the inner edge of the disk, important in
local irradiation scenarios for producing the short-lived radionuclides found
in meteorites.


title: Z-bursts from the Virgo cluster

abstract:
  Resonant annihilation of ultra-high energy cosmic neutrinos (UHECnu) on the
cosmic neutrino background (CnuB) into Z bosons--the Z-burst mechanism--and its
associated absorption and emission phenomenology provide a unique, albeit
indirect, probe of the CnuB in its present state. In this paper, we examine the
implications of gravitational clustering of the CnuB in nearby galaxy clusters
for the Z-burst phenomenology. In particular, we study the emission features of
the Z-decay products originating from the Virgo cluster, and the potential of
future cosmic ray experiments to observe clustering-enhanced Z-burst rates. We
find that a detector with an exposure equivalent to three years of observations
at the Extreme Universe Space Observatory (EUSO) will very likely measure these
enhanced rates together with the associated UHECnu flux, provided that the
latter saturates current observational limits and the neutrino masses are
quasi-degenerate, m_nu_i < 0.1 eV. In the case of UHECnu fluxes below the
electromagnetic cascade limit, or a hierarchical neutrino mass spectrum, an
experimental sensitivity exceeding that of EUSO by at least two orders of
magnitude is required to detect the clustering enhancements with any certainty.


title:
FrogEye, the Quantum Coronagraphic mask. The Photon Orbital Angular
  Momentum and its applications to Astronomy

abstract:
  We propose to realize an optical device based on the properties of photon
orbital angular momentum (POAM) to detect the presence of closeby faint
companions in double systems using Laguerre-Gaussian (L-G) modes of the light.
We test also the possibility of using L-G modes to build coronagraph mask. We
realized in the laboratory a prototype using a blazed l=1 hologram to simulate
the separation between two stars, as observed with a telescope, in
Laguerre-Gaussian modes.


title:
Dependence of the non-linear mass power spectrum on the equation of
  state of dark energy

abstract:
  We present N-body simulation calculations of the dependence of the power
spectrum of non-linear cosmological mass density fluctuations on the equation
of state of the dark energy, w=p/rho. At fixed linear theory power, increasing
w leads to an increase in non-linear power, with the effect increasing with k.
By k=10 h/Mpc, a model with w=-0.75 has ~12% more power than a standard
cosmological constant model (w=-1), while a model with w=-0.5 has ~33% extra
power (at z=0). The size of the effect increases with increasing dark energy
fraction, and to a lesser extent increasing power spectrum normalization, but
is insensitive to the power spectrum shape (the numbers above are for
Omega_m=0.281 and sigma_8=0.897). A code quantifying the non-linear effect of
varying w, as a function of k, z, and other cosmological parameters, which
should be accurate to a few percent for k<10 h/Mpc for models that fit the
current observations, is available at
http://www.cita.utoronto.ca/~pmcdonal/code.html. This paper also serves as an
example of a detailed exploration of the numerical convergence properties of
ratios of power spectra for different models, which can be useful because some
kinds of numerical error cancel in a ratio. When precision calculations based
on numerical simulations are needed for many different models, efficiency may
be gained by breaking the problem into a calculation of the absolute prediction
at a central point, and calculations of the relative change in the prediction
with model parameters.


title:
UHE nuclei propagation and the interpretation of the ankle in the
  cosmic-ray spectrum

abstract:
  We consider the stochastic propagation of high-energy protons and nuclei in
the cosmological microwave and infrared backgrounds, using revised photonuclear
cross-sections and following primary and secondary nuclei in the full 2D
nuclear chart. We confirm earlier results showing that the high-energy data can
be fit with a pure proton extragalactic cosmic ray (EGCR) component if the
source spectrum is \propto E^{-2.6}. In this case the ankle in the CR spectrum
may be interpreted as a pair-production dip associated with the propagation. We
show that when heavier nuclei are included in the source with a composition
similar to that of Galactic cosmic-rays (GCRs), the pair-production dip is not
present unless the proton fraction is higher than 85%. In the mixed composition
case, the ankle recovers the past interpretation as the transition from GCRs to
EGCRs and the highest energy data can be explained by a harder source spectrum
\propto E^{-2.2} - E^{-2.3}, reminiscent of relativistic shock acceleration
predictions, and in good agreement with the GCR data at low-energy and holistic
scenarios.


title: Constraining the properties of spots on Pleiades very low mass stars

abstract:
  We present results of a multi-filter monitoring campaign for very low mass
(VLM) stars in the Pleiades. Simultaneous to our I-band time series (Scholz &
Eisloeffel 2004), which delivered photometric periods for nine VLM stars, we
obtained light curves in the J- and H-band. One VLM star with M~0.15 Ms
(BPL129) shows a period in all three wavelength bands. The amplitudes in I, J,
and H are 0.035, 0.035, and 0.032 mag. These values are compared to
simulations, in which we compute the photometric amplitude as a function of
spot temperature and filling factor. The best agreement between observations
and models is found for cool spots with a temperature contrast of 18-31% and a
very low surface filling factor of 4-5%. We suggest that compared to more
massive stars VLM objects may have either very few spots or a rather symmetric
spot distribution. This difference might be explained with a change from a
shell to a distributed dynamo in the VLM regime.


title:
Interstellar Polarization and the Position Angle Orientations of Seyfert
  1 Galaxies

abstract:
  We comment on recent spectropolarimetric studies that compare the observed
polarization position angles (PAs) of Seyfert 1 galaxies near H alpha with the
observed orientations of their radio source axes on the sky. For a Seyfert
galaxy in which scattering occurs mainly in an equatorial scattering region,
one expects the polarization PA to be parallel to the radio axis, while in a
case in which light scatters predominantly in the polar regions, the H alpha
polarization PA should be perpendicular to the radio axis. In practice, these
correlations are difficult to establish because a Galactic interstellar
polarization contribution can introduce a significant uncertainty into the
polarization PA determination, even when the magnitude of interstellar
polarization is small. We show how such uncertainties may affect the analysis
of PA alignments and present spectropolarimetric observations of a probe star
along the line of sight to the Seyfert 1 galaxy Mrk 871 that allow us to assess
the intrinsic H alpha polarization and PA of Mrk 871. These results suggest
that spectropolarimetric observations of such probe stars should form an
integral part of future Seyfert galaxy polarization studies.


title:
Modeling Accelerated Pick-up Ion Distributions at an Interplanetary
  Shock

abstract:
  The acceleration of interstellar pick-up ions as well as solar wind species
has been observed at a multitude of interplanetary (IP) shocks by different
spacecraft. The efficiency of injection of the pick-up ion component differs
from that of the solar wind, and is expected to be strongly enhanced at highly
oblique and quasi-perpendicular shock events, in accord with inferences from
{\it in situ} observations. This paper explores theoretical modeling of the
phase space distributions of accelerated ions obtained by the Ulysses mission
for the Day 292, 1991 shock associated with a corotating interaction region,
encountered before Ulysses' fly-by of Jupiter. A Monte Carlo simulation is used
to model the acceleration process, adapting a technique that has been
successfully tested on earlier IP shocks possessing minimal pick-up ion
presence. Phase space distributions from the simulation technique for various
low mass ions are compared with SWICS and HI-SCALE data to deduce values of a
``turbulence parameter'' that controls the efficiency of injection, and the
degree of cross-field diffusion. Acceptable fits are obtained for the $H^+$ and
$He^+$ populations using standard prescriptions for the pick-up ion
distribution; $He^{++}$ spectral data was only fit well for scenarios very
close to the Bohm diffusion limit. It is also found that the simulation
successfully accounts for the observation of energetic protons farther upstream
of the forward shock than lower energy pick-up protons, using the same
turbulence parameter that is required to achieve reasonable spectral fits.


title:
Self-similar structure of the magnetized radiation-dominated accretion
  disks

abstract:
  We investigate the effects of a large-scale magnetic field with open field
lines on the steady-state structure of a radiation-dominated accretion disk,
using self-similarity technique. The disk is supposed to be turbulent and
possesses an effective viscosity and an effective magnetic diffusivity. We
consider the extreme case in which the generated energy due to viscous and
magnetic dissipation is balanced by the advection cooling. While the magnetic
field outside of the disk is treated in a phenomenological way, the internal
field is determined self-consistently. Magnetized and nonmagnetized solutions
have the same radial dependence, irrespective of the values of the input
parameters. Generally, our self-similar solutions are very sensitive to the
viscosity or diffusivity coefficients. For example, the density and the
rotation velocity increase when the viscosity coefficient decreases. The gas
rotates with sub-Keplerian angular velocity with a factor less than unity which
depends on the magnetic field configuration. Magnetic field significantly
reduce disk thickness, however, tends to increase the radial velocity comparing
to the nonmagnetic self-similar solutions.


title: Grain Alignment by Radiation in Dark Clouds and Cores

abstract:
  We study alignment of grains by radiative torques. We found steep rise of
radiative torque efficiency as grain size increases. This allows larger grains
that are known to exist within molecular clouds to be aligned by the attenuated
and reddened interstellar radiation field. In particular, we found that, even
deep inside giant molecular clouds, e.g. at optical depths corresponding to
less than Av of 10 large grains can still be aligned by radiative torque. This
means that, contrary to earlier claims, far-infrared/submillimeter polarimetry
provides a reliable tool to study magnetic fields of pre-stellar cores. Our
results show that the grain size distribution is important for determining the
relation between the degree of polarization and intensity.


title:
Spectral Properties of Interstellar Turbulence via Velocity Channel
  Analysis

abstract:
  In this presentation we review the link between the statistics of intensity
fluctuations in spectral line data cubes with underlying statistical properties
of turbulence in the interstellar medium. Both the formalism of Velocity
Channel Analysis for optically thin lines and its extension to the lines with
self-absorption is described. We demonstrate that by observing optically thin
lines from cold gas in sufficiently narrow (thin) velocity channels one may
recover the scaling of the stochastic velocities from turbulent cascade, in
particular, Kolmogorov velocities give $K^{-2.7}$ contribution to the intensity
power spectrum. Synthetically increasing the channel thickness separates out
the underlying density inhomogeneities of the gas. Effects of self absorption,
on the other hand, retain the velocity signature even for integrated lines. As
a result, intensity fluctuations tend to show universal but featureless scaling
of the power $\propto K^{-3}$ over the range of scales.


title: Statistics of turbulence via polarimetry: alignment of grains and atoms

abstract:
  Most astrophysical fluids are turbulent and magnetized. Fluctuations of
polarization provide a promising way to study astrophysical magnetic
turbulence. We discuss polarization that arises from grains and atoms aligned
in respect to magnetic field, describe the processes of alignment, explain when
the alignment reflects the direction of magnetic field. We show that temporal
fluctuations of interplanetary magnetic field can be studied using aligned
sodium atoms.


title:
Astrophysical Implications of Turbulent Reconnection: from cosmic rays
  to star formation

abstract:
  Turbulent reconnection allows fast magnetic reconnection of astrophysical
magnetic fields. This entails numerous astrophysical implications and opens new
ways to approach long standing problems. I briefly discuss a model of turbulent
reconnection within which the stochasticity of 3D magnetic field enables rapid
reconnection through both allowing multiple reconnection events to take place
simultaneously and by restricting the extension of current sheets. In fully
ionized gas the model in Lazarian and Vishniac 99 predicts reconnection rates
that depend only on the intensity of turbulence. In partially ionized gas a
modification of the original model in Lazarian, Vishniac and Cho 04 predicts
the reconnection rates that, apart from the turbulence intensity depend on the
degree of ionization. In both cases the reconnection may be slow and fast
depending on the level of turbulence in the system. As the result, the
reconnection gets bursty, which provides a possible explanation to Solar flares
and possibly to gamma ray busts. The implications of the turbulent reconnection
model have not been yet studied in sufficient detail. I discuss first order
Fermi acceleration of cosmic ray that takes place as the oppositely directed
magnetic fluxes move together. This acceleration would work in conjunction with
the second order Fermi acceleration that is caused by turbulence in the
reconnection region. In partially ionized gas the stochastic reconnection
enables fast removal of magnetic flux from star forming molecular clouds.


title: Cosmic ray transport in MHD turbulence

abstract:
  Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call
for revisions in the picture of cosmic ray transport. In this paper we use
recently obtained scaling laws for MHD modes to obtain the scattering frequency
for cosmic rays. We account for the turbulence cutoff arising from both
collisional and collisionless damping. We obtain the scattering rate and show
that fast modes provide the dominant contribution to cosmic ray scattering for
the typical interstellar conditions in spite of the fact that fast modes are
subjected to damping. We determine how the efficiency of the scattering depends
on the characteristics of ionized media, e.g. plasma $\beta$. We show that
streaming instability is suppressed by the ambient MHD turbulence.


title: Turbulence Statistics from Spectral Line Observations

abstract:
  Turbulence is a crucial component of dynamics of astrophysical fluids
dynamics, including those of ISM, clusters of galaxies and circumstellar
regions. Doppler shifted spectral lines provide a unique source of information
on turbulent velocities. We discuss Velocity-Channel Analysis (VCA) and its
offspring Velocity Coordinate Spectrum (VCS) that are based on the analytical
description of the spectral line statistics. Those techniques are well suited
for studies of supersonic turbulence. We stress that a great advantage of VCS
is that it does not necessary require good spatial resolution. Addressing the
studies of mildly supersonic and subsonic turbulence we discuss the criterion
that allows to determine whether Velocity Centroids are dominated by density or
velocity. We briefly discuss ways of going beyond power spectra by using of
higher order correlations as well as genus analysis. We outline the relation
between Spectral Correlation Functions and the statistics available through VCA
and VCS.


title: MHD Turbulence: Properties of Alfven, Slow and Fast Modes

abstract:
  We summarise basic properties of MHD turbulence. First, MHD turbulence is not
so messy as it is believed. In fact, the notion of strong non-linear coupling
of compressible and incompressible motions along MHD cascade is not tenable.
Alfven, slow and fast modes of MHD turbulence follow their own cascades and
exhibit degrees of anisotropy consistent with theoretical expectations. Second,
the fast decay of turbulence is not related to the compressibility of fluid.
Rates of decay of compressible and incompressible motions are very similar.
Third, the properties of Alfven and slow modes are similar to their
counterparts in the incompressible MHD. The properties of fast modes are
similar to accoustic turbulence, which does require more studies. Fourth, the
density at low Mach numbers and logarithm of density at higher Mach numbers
exhibit Kolmogorov-type spectrum.


title: OI Line Emission in the Quasar PG 1116+215

abstract:
  By observing the near-infrared spectrum of the quasar PG 1116+215 at z =
0.176 and combining with the HST/FOS spectrum, we obtained the relative
strengths of three permitted OI lines ({lambda}1304, {lambda}8446, and
{lambda}11287) in a quasar for the first time. The photon flux ratios of the OI
lines of the quasar were compared with those previously measured in a Seyfert 1
and six narrow-line Seyfert 1s. No significant differences were found in the OI
line flux ratios between the quasar and the other Seyferts, suggesting that the
gas density in the OI and FeII line-emitting regions in the quasar is of the
same order as those in low-luminosity AGNs. It was also found that the line
width of OI {lambda}11287 is significantly narrower than that of Ly{alpha},
which is consistent with OI and FeII emission occurring in the partly ionized
regions at the outermost portion of the broad-line region where velocities are
small.


title: An Equilibrium Dark Matter Halo with the Burkert Profile

abstract:
  In this paper a prescription for generating an equilibrium spherical system
depicted with cuspy density profiles is extended to a core density profile, the
Burkert profile, which is observationally more suitable to dwarfs. By using a
time-saving Monte Carlo method instead of N-body simulations, we show that the
Burkert halo initialized with the distribution function that depends only on
energy is in a practically stable equilibrium. The one generated using the
local Maxwellian approximation is unstable, where the flat core density
structure tends to steepen. This is fundamentally different from the previous
study on a halo with cuspy density profile. The deviation of the unstable
"Burkert" from the initial Burkert profile is found to be closely related to
taking a Gaussian as the velocity distribution at any given point. The
significance of not using the local Maxwellian approximation is further
demonstrated by exploring the dynamical evolution of compact super star
clusters in the Burkert halo. In particular, the local Maxwellian approximation
will result in underestimating the dynamical friction and overestimating
sinking time scale. Accordingly, it will lead to lower probability of forming
massive bulges and young nuclear star clusters in bulgeless galaxies.


title:
Dark galaxies or tidal debris? Kinematical clues to the origin of
  massive isolated HI clouds

abstract:
  An extended HI cloud (VIRGOHI 21) with an HI mass of $\sim10^8$ M$_{\odot}$
and no apparent optical counterpart was recently discovered in the Virgo
cluster. In order to understand the origin of physical properties of apparently
isolated HI clouds like the VIRGOHI21, we numerically investigate physical
properties of tidal HI debris that were formed by galaxy-galaxy interaction in
clusters of galaxies. Our hydrodynamical simulations demonstrate that tidal
debris with total HI masses of $10^8-10^9$ M$_{\odot}$ can have (1) wide HI
velocity widths ($>200$ km s$^{-1}$), (2) a small mass fraction of stars
($\sim$10%), and (3) a mean $B$-band surface brightness of the stellar
components fainter than 30 mag arcsec$^{-2}$. These results suggest that the
VIRGOHI21, which lies at a projected distance of $\sim$ 150 kpc from the
one-armed, HI-rich spiral galaxy M99 (NGC 4254), is tidal debris. We propose
that the comparison between the simulated and the observed velocity fields of
HI clouds allows us to better understand their nature and origin (e.g., whether
they are just tidal debris or ``dark galaxies'' that have HI gas only and are
embedded by dark matter halos). We also discuss the timescales for isolated HI
gas to be evaporated by thermal conduction of the hot intracluster gas.


title:
Cosmological parameters from combined second- and third-order aperture
  mass statistics of cosmic shear

abstract:
  We present predictions for cosmological parameter constraints from combined
measurements of second- and third-order statistics of cosmic shear. We define
the generalized third-order aperture mass statistics <M_ap^3> and show that it
contains much more information about the bispectrum of the projected matter
density than the skewness of the aperture mass. From theoretical models as well
as from LCDM ray-tracing simulations, we calculate <M_ap^2> and <M_ap^3> and
their dependence on cosmological parameters. The covariances including shot
noise and cosmic variance of M_ap^2, M_ap^3 and their cross-correlation are
calculated using ray-tracing simulations. We perform an extensive Fisher matrix
analysis, and for various combinations of cosmological parameters, we predict
1-sigma-errors corresponding to measurements from a deep 29 square degree
cosmic shear survey. Although the parameter degeneracies can not be lifted
completely, the (linear) combination of second- and third-order aperture mass
statistics reduces the errors significantly. The strong degeneracy between
Omega_m and sigma_8, present for all second-order cosmic shear measures, is
diminished substantially, whereas less improvement is found for the
near-degenerate pair consisting of the shape parameter Gamma and the spectral
index n_s. Uncertainties in the source galaxy redshift z_0 increase the errors
of all other parameters.


title:
The Nature of the Driving Mechanism in the Pulsating Hybrid PG 1159 Star
  Abell 43

abstract:
  We extend our previous pulsational stability analyses of PG 1159 stars by
modeling the hybrid PG 1159 type star Abell 43. We show that the standard
kappa-mechanism due to the ionization of C and O in the envelope of this H-rich
PG 1159 star is perfectly able to drive g-mode pulsations. Thus, contrary to a
recent suggestion, there is no need to invoke any new or exotic mechanism to
explain the pulsational instabilities observed in this particular star. Our
expected instability band for l = 1 modes extends in period from ~ 2604 s to ~
5529 s, which is consistent with the available photometric observations of
Abell 43. We also suggest that efforts to detect luminosity variations in its
sibling NGC 7094 be pursued.


title: Phenomenology of cosmic ray air showers

abstract:
  The properties of cosmic rays with energies above 1PeV have to be deduced
from the spacetime structure and particle content of the air showers which they
initiate. In this review, a summary of the phenomenology of these giant air
showers is presented. We describe the hadronic interaction models used to
extrapolate results from collider data to ultra high energies, an also the main
electromagnetic processes that govern the longitudinal shower evolution as well
as the lateral spread of particles.


title: Seismic Search for Strange Quark Nuggets

abstract:
  Bounds on masses and abundances of Strange Quark Nuggets (SQNs) are inferred
from a seismic search on Earth. Potential SQN bounds from a possible seismic
search on the Moon are reviewed and compared with Earth capabilities. Bounds
are derived from the data taken by seismometers implanted on the Moon by the
Apollo astronauts. We show that the Apollo data implies that the abundance of
SQNs in the region of 10 kg to one ton must be at least an order of magnitude
less than would saturate the dark matter in the solar neighborhood.


title:
Pulsar timing and the detection of black hole binary systems in globular
  clusters

abstract:
  The possible existence of intermediate mass binary black holes (IMBBHs) in
globular clusters (GCs) offers a unique geometry in which to detect space-time
oscillations. For certain pulsar-IMBBH configurations possible within a GC, the
usual far-field plane wave approximation for the IMBBH metric perturbation
severely underestimates the magnitude of the induced pulsar pulse
time-of-arrival (TOA) fluctuations. In this letter, the expected TOA
fluctuations induced by an IMBBH lying close to the line-of-sight between a
pulsar and the Earth are calculated for the first time. For an IMBBH consisting
of 10 Msolar and 10^3 Msolar components, a 10 year orbital period, and located
0.1 lyr from the Earth-Pulsar line of sight, the induced pulsar timing residual
amplitude will be of order 5 to 500 ns.


title: The Low-Redshift Lyman Alpha Forest toward PKS 0405-123

abstract:
  We present STIS 7km/s resolution data of the Ly-a forest toward PKS0405-123
(z=0.574). We make two samples. The strong sample (60 systems) has column
density logNHI>13.3 over 0.002<z<0.423, and the weak sample (44) has
logNHI>13.1 at 0.020<z<0.234; 7 absorbers show metals, all with OVI, but often
offset in velocity from HI. The strong sample Doppler parameters show
<b>=47+-22km/s; for the weak, <b>=44+-21km/s. Line blending and s/n effects
likely inflate b. The redshift density dN/dz is consistent with previous, lower
resolution results for logNHI>14.0. For 13.1<logNHI<14.0, we find a dN/dz
overdensity of ~0.2-0.3 dex at 0.127<z<0.234, which we believe arises from
cosmic variance. We find Ly-a clustering over Delta v<250km/s for logNHI>13.3,
consistent with a numerical model. There is a void in the strong sample at
0.0320<z<0.0814. We detect radial velocity correlations for Delta v<250km/s
between Ly-a absorbers and 39 galaxies in a 10' field. The correlation grows
with minimum NHI, peaking for logNHI ~> 13.5-14.0. The strength is similar to
that of the galaxy-galaxy correlation for our sample, implying that such Ly-a
systems have mass log M/Msun= 11.3+1.0-0.6. Including lower column density
systems in the sample shows correlations only out to Delta v <125km/s, as would
be expected for smaller density perturbations. Galaxy counts and local HI
column density appear correlated, peaking at ~5000km/s. We also give column
densities for Galactic species. (Abridged)


title: Nanodiamond dust and the far-ultraviolet quasar break

abstract:
  We explore the possibility that the steepening observed shortward of 1000A in
the energy distribution of quasars may result from absorption by dust, being
either intrinsic to the quasar environment or intergalactic. We find that a
dust extinction curve consisting of nanodiamonds, composed of terrestrial cubic
diamonds or with surface impurities as found in carbonaceous chondrite
meteorites, such as Allende, is successful in reproducing the sharp break
observed. The intergalactic dust model is partially successful in explaining
the shape of the composite energy distribution, but must be discarded in the
end, as the amount of crystalline dust required is unreasonable and would imply
an improbable fine tuning among the dust formation processes. The alternative
intrinsic dust model requires a mixture of both cubic diamonds and Allende
nanodiamonds and provide a better fit of the UV break. The gas column densities
implied are of the order 10^{20} cm^{-2} assuming solar metallicity for carbon
and full depletion of carbon into dust. The absorption only occurs in the
ultraviolet and is totally negligible in the visible. The minimum dust mass
required is of the order ~ 0.003 r_{pc}^{2}M_o, where r_{pc} is the distance in
parsec between the dust screen and the continuum source. The intrinsic dust
model reproduces the flux {\it rise} observed around 660A in key quasar spectra
quite well. We present indirect evidence of a shallow continuum break near 670A
(18.5 eV), which would be intrinsic to the quasar continuum.


title: Relic Gravitational Waves and the Evolution of the Universe

abstract:
  In the inflation models, the relic gravitational waves (RGW) generated in the
inflation stage, and evolved in the Universe until now. In the different
cosmological evolution models, one can get different gravitational waves power
spectrum. In this paper, we give a simple formula to estimate this spectrum in
a general cosmological model. From this formula, one can easily find the
relation between this power spectrum and the cosmological evolution models. The
spectrum includes all the information about the evolution of the scale factor
$a$ from inflation to now.
  So RGW is a more clear fossil, which records the cosmological evolution
information, and be a useful complementarity for another fossil$-$Cosmic
  Microwave Background Radiation (CMB).


title: Numeric Spectrum of Relic Gravitational Waves in Accelerating Universe

abstract:
  The accelerating expansion of the Universe at the present stage is a process
that will change the spectrum of relic gravitational waves. Here we present a
numerical calculation for the power spectrum of relic gravitational waves in
the accelerating Universe. The results show that although the overall features
of the power spectrum is similar to that in the non-accelerating models, the
amplitude is smaller by an order of $10^{-1}$. We also find that the spectrum
is very sensitive to the index $\beta$ of the inflationary expansion with the
scale factor $a(\tau) \propto |\tau|^{1+\beta}$. With increase of $\beta$, the
resulting spectrum is tilted to be flatter with more power on high frequencies,
and the sensitivity of the second science run of the LIGO detectors puts a
restriction on the parameter $\beta < -1.8$. The influence of reheating
following the inflation has been examined.


title: Can Cosmic Rays Heat the Intergalactic Medium?

abstract:
  Supernova explosions in the early star forming galaxies will accelerate
cosmic rays (CRs). CRs are typically confined in the collapsed objects for a
short period before escaping into the intergalactic medium (IGM). Galactic
outflows can facilitate this escape by advecting CRs into the IGM. An outflow
that results in a termination shock can also generate more CRs. We show that
the CR protons from the above processes can significantly affect the thermal
history of the IGM. Within plausible range of parameters, cosmic ray heating
can compensate for adiabatic cooling and explain the measured IGM temperature
at redshifts z between 2 to 4, even with early reionization.


title:
The HIPASS Catalogue: III - Optical Counterparts & Isolated Dark
  Galaxies

abstract:
  We present the largest catalogue to date of optical counterparts for HI
radio-selected galaxies, Hopcat. Of the 4315 HI radio-detected sources from the
HI Parkes All Sky Survey (Hipass) catalogue, we find optical counterparts for
3618 (84%) galaxies. Of these, 1798 (42%) have confirmed optical velocities and
848 (20%) are single matches without confirmed velocities. Some galaxy matches
are members of galaxy groups. From these multiple galaxy matches, 714 (16%)
have confirmed optical velocities and a further 258 (6%) galaxies are without
confirmed velocities. For 481 (11%), multiple galaxies are present but no
single optical counterpart can be chosen and 216 (5%) have no obvious optical
galaxy present. Most of these 'blank fields' are in crowded fields along the
Galactic plane or have high extinctions.
  Isolated 'Dark galaxy' candidates are investigated using an extinction cut of
ABj < 1 mag and the blank fields category. Of the 3692 galaxies with an ABj
extinction < 1 mag, only 13 are also blank fields. Of these, 12 are eliminated
either with follow-up Parkes observations or are in crowded fields. The
remaining one has a low surface brightness optical counterpart. Hence, no
isolated optically dark galaxies have been found within the limits of the
Hipass survey.


title: New High-Redshift Galaxies at $z$ = 5.8 - 6.5 in the Subaru Deep Field

abstract:
  In order to search for high-redshift galaxies around $z \sim 6$ in the Subaru
Deep Field, we have investigated NB816-dropout galaxies where NB816 is the
narrowband filter centered at 815nm with FWHM of 12.5 nm for the Suprime-Cam on
the Subaru Telescope. Since the NB816 imaging is so deep we can detect 10
well-defined NB816-dropout galaxies that we identify to lie at $z$ = 5.8 --
6.5. We discuss their observational properties.


title: All Coronal Loops are the Same: Evidence to the Contrary

abstract:
  The 1998 April 20 spectral line data from the Coronal Diagnostics
Spectrometer (CDS) on the {\it Solar and Heliospheric Observatory} (\SOHO)
shows a coronal loop on the solar limb. Our original analysis of these data
showed that the plasma was multi-thermal, both along the length of the loop and
along the line of sight. However, more recent results by other authors indicate
that background subtraction might change these conclusions, so we consider the
effect of background subtraction on our analysis. We show Emission Measure (EM)
Loci plots of three representative pixels: loop apex, upper leg, and lower leg.
Comparisons of the original and background-subtracted intensities show that the
EM Loci are more tightly clustered after background subtraction, but that the
plasma is still not well represented by an isothermal model. Our results taken
together with those of other authors indicate that a variety of temperature
structures may be present within loops.


title: A simple model for the evolution of disc galaxies: The Milky Way

abstract:
  A simple model for the evolution of disc galaxies is presented. We adopt
three numbers from observations of the Milky Way disc, the local surface mass
density, the stellar scale length (of the assumedly exponential disc) and the
amplitude of the (assumedly flat) rotation curve, and physically, the (local)
dynamical Kennicutt star formation prescription, standard chemical evolution
equations assuming and a model for spectral evolution of stellar populations.
We can determine the detailed evolution of the model with only the addition of
standard cosmological scalings with time of the dimensional parameters. A
surprising wealth of detailed specifications follows from this prescription
including the gaseous infall rate as a function of radius and time, the
distribution of stellar ages and metallicities with time and radius, surface
brightness profiles at different wavelengths, colours etc. At the solar
neighbourhood stars start to form $\approx 10 Gyrs$ ago at an increasing rate
peaking 4 billion years ago and then slowly declining in good agreement with
observations. The mean age of long lived stars at the solar neighbourhood is
about $4 Gyrs$. The local surface density of the stars and gas are 35 and $15
M_{\odot}pc^{-2}$, respectively. The metallicity distribution of the stars at
the solar radius is narrow with a peak at $[Z/Z_{\odot}] = -0.1$.Both a
Salpeter IMF and a Chabrier IMF are consistent with observations. Comparisons
with the current and local fossil evidence provides support for the model which
can then be used to assess other local disc galaxies, the evolution of disc
galaxies in deep optical surveys and also for theoretical investigations such
as simulations of merging disc galaxies (abbreviated).


title: Observational Constraints on Pulsar Wind Theories

abstract:
  Two-dimensional, relativistic, MHD simulations of pulsar-wind powered nebulae
provide strong constraints on the properties of the winds themselves. In
particular, they confirm that Poynting flux must be converted into particle
energy close to or inside the termination shock front, emphasising the puzzle
known as the $\sigma$ paradox. To distinguish between the different possible
resolutions of this paradox, additional observational constraints are required.
In this paper, I briefly discuss two recents developments in this respect: the
modelling of high time-resolution optical polarimetry of the Crab pulsar, and
the detection of the pulsar/Be star binary PSR 1259-63 in TeV energy
gamma-rays.


title: Is there a phase constraint for solar dynamo models?

abstract:
  The spatio-temporal relationship between the sign of the observed radial
component of the magnetic field at the solar surface and the sign of the
toroidal field as inferred from Hale's polarity rules for sunspots is usually
interpreted as signifying the phase relation between the poloidal and the
toroidal magnetic field components involved in the solar dynamo process. This
has been taken as a constraint for models of the solar dynamo. This note draws
attention to the fact that the observed phase relation is naturally and
inevitably produced by the emergence of tilted bipolar regions and flux
transport through surface flows, without any necessity of recourse to the
dynamo process. Consequently, there is no constraint on dynamo models resulting
from the observed phase relation.


title:
Identification of extragalactic sources of the highest energy EGRET
  photons by correlation analysis

abstract:
  We found significant correlations between the arrival directions of the
highest energy photons (E>10 GeV) observed by EGRET and positions of the BL Lac
type objects (BL Lacs). The observed correlations imply that not less than
three per cent of extragalactic photons at these energies originate from BL
Lacs. Some of the correlating BL Lacs have no counterparts in the EGRET source
catalog, i.e. do not coincide with strong emitters of gamma-rays at lower
energy. The study of correlating BL Lacs suggests that they may form a subset
which is statistically different from the total BL Lac catalog; we argue that
they are prominent candidates for TeV gamma-ray sources. Our results
demonstrate that the analysis of positional correlations is a powerful approach
indispensable in cases when low statistics limits or even prohibits the
standard case-by-case identification.


title:
Particle acceleration in thick parallel shocks with high compression
  ratio

abstract:
  We report studies on first-order Fermi acceleration in parallel modified
shock waves with a large scattering center compression ratio expected from
turbulence transmission models. Using a Monte Carlo technique we have modeled
particle acceleration in shocks with a velocity ranging from nonrelativistic to
ultrarelativistic and a thickness extending from nearly steplike to very wide
structures exceeding the particle diffusion length by orders of magnitude. The
nonrelativistic diffusion approximation is found to be surprisingly accurate in
predicting the spectral index of a thick shock with large compression ratio
even in the cases involving relativistic shock speeds.


title:
Formation of Population III Stars in Fossil HII Regions: Significance of
  HD

abstract:
  We study the evolution of gas in HII regions around the first stars after the
death of the exciting stars. If the first star in a small halo dies without
supernova (SN), subsequent star formation is possible in the same halo. We thus
investigate the effect of ionization of the gas on subsequent star formation
within small halos in the early universe using one-dimensional hydrodynamics
with spherical symmetry along with non-equilibrium primordial gas chemistry. We
find that the enhanced electron fraction facilitates the formation of molecular
hydrogen at the cores of these halos. The low temperature circumstances
produced by the H_2 cooling is suitable for HD formation and the resultant
cooling further drops the temperature below 100 K. Consequently, low-mass stars
with primordial abundances can form even in a small halo. After accreting the
interstellar metals, these stars might resemble low-mass ultra metal-poor stars
discovered in the present Galactic halo.


title:
Studying the coincidence excess between EXPLORER and NAUTILUS during
  1998

abstract:
  The coincidences between EXPLORER and NAUTILUS during 1998 (Astone et al.
2001) are more deeply studied. It is found that the coincidence excess is
greater in the ten-day period 7-17 September 1998 and it occurs at the sidereal
hour 4, when the detectors axes are perpendicular to the Galactic Disk. The
purpose of this paper is to bring our results with the GW detectors to the
attention of scientists working in the astrophysical field, and ask them
whether are they aware of any special phenomenon occurring when EXPLORER and
NAUTILUS showed a coincidence excess.


title: Dark energy and the generalized second law

abstract:
  We explore the thermodynamics of dark energy taking into account the
existence of the observer's event horizon in accelerated universes. Except for
the initial stage of Chaplygin gas dominated expansion, the generalized second
law of gravitational thermodynamics is fulfilled and the temperature of the
phantom fluid results positive. This substantially extends the work of Pollock
and Singh [10] on the thermodynamics of super--inflationary expansion.


title: Scalar Dark Matter and Cold Stars

abstract:
  In a medium composed of scalar particles with non-zero mass, the range of
Van-der-Waals-type scalar mediated interactions among nucleons becomes infinite
when the medium makes a transition to a Bose-Einstein condensed phase. We
explore this phenomenon in an astrophysical context. Namely, we study the
effect of a scalar dark matter background on the equilibrium of degenerate
stars.In particular we focus on white dwarfs and the changes induced in their
masses and in their radii.


title:
The composition and size distribution of the dust in the coma of comet
  Hale-Bopp

abstract:
  We discuss the composition and size distribution of the dust in the coma of
comet Hale-Bopp. We do this by fitting simultaneously the infrared emission
spectrum measured by the infrared space observatory (ISO) and the measured
degree of linear polarization of scattered light at various phase angles and 12
different wavelengths. The effects of particle shape on the modeled optical
properties of the dust grains are taken into account. We constrain our fit by
forcing the abundances of the major rock forming chemical elements to be solar.
The infrared spectrum at long wavelengths reveals that large grains are needed
in order to fit the spectral slope. The size and shape distribution we employ
allows us to estimate the sizes of the crystalline silicates. The ratios of the
strength of various forsterite features show that the crystalline silicate
grains in Hale-Bopp must be submicron sized. We exclude the presence of large
crystalline silicate grains in the coma. Because of this lack of large
crystalline grains combined with the fact that we do need large amorphous
grains to fit the emission spectrum at long wavelengths, we need only
approximately 4% of crystalline silicates by mass. After correcting for
possible hidden crystalline material included in large amorphous grains, our
best estimate of the total mass fraction of crystalline material is
approximately 7.5%, significantly lower than deduced in previous studies in
which the typical derived crystallinity is 20-30%. The implications of this on
the possible origin and evolution of the comet are discussed. The crystallinity
we observe in Hale-Bopp is consistent with the production of crystalline
silicates in the inner solar system by thermal annealing and subsequent radial
mixing to the comet forming region.


title: Rates and Progenitors of Type Ia Supernovae

abstract:
  The remarkable uniformity of Type Ia supernovae (SNe Ia) has allowed
astronomers to use them as distance indicators to measure the properties and
expansion history of the Universe. However, SNe Ia exhibit intrinsic variation
in both their spectra and observed brightness. To reduce these systematic
uncertainties, we need a deeper understanding of the observed variations in SNe
Ia. Toward this end, the Nearby Supernova Factory (SNfactory) has been designed
to discover hundreds of SNe Ia in a systematic and automated fashion and study
them in detail.
  A prototype run of the SNfactory search pipeline conducted from 2002 to 2003
discovered 83 SNe at a final rate of 12 SNe/month. A large, homogeneous search
of this scale offers an excellent opportunity to measure the rate of SNe Ia.
This dissertation presents a new method for analyzing the true sensitivity of a
multi-epoch supernova search and finds a SN Ia rate from $z\sim0.01$--0.1 of
$r_V = 4.26 (+1.39 -1.93) (+0.10 - 0.10)$ SNe Ia/yr/Mpc$^3$ from a preliminary
analysis of a subsample of the SNfactory prototype search.
  Several unusual supernovae were found in the course of the SNfactory
prototype search. One in particular, SN 2002ic, was the first SN Ia to exhibit
convincing evidence for a circumstellar medium and offers valuable insight into
the progenitors of SNe Ia.


title: Stringy Dark Energy Model with Cold Dark Matter

abstract:
  Cosmological consequences of adding the Cold Dark Matter (CDM) to the exactly
solvable stringy Dark Energy (DE) model are investigated. The model is
motivated by the consideration of our Universe as a slowly decaying D3-brane.
The decay of this D-brane is described in the String Field Theory framework.
Stability conditions of the exact solution with respect to small fluctuations
of the initial value of the CDM energy density are found. Solutions with large
initial value of the CDM energy density attracted by the exact solution without
CDM are constructed numerically. In contrast to the LambdaCDM model the Hubble
parameter in the model is not a monotonic function of time. For specific
initial data the DE state parameter w_{DE} is also not monotonic function of
time. For these cases there are two separate regions of time where w_{DE} being
less than -1 is close to -1.


title:
High-resolution spectroscopy of the old open cluster Collinder
  261:abundances of Iron and other elements

abstract:
  We present the analysis of high resolution spectra of six red giant stars in
the old open cluster Collinder 261. Reddening values for individual stars,
derived from the relation between colours and temperatures (deduced from our
fully spectroscopic analysis) are consistent with previous determinations based
on photometry. For this cluster we derive an iron abundance of [Fe/H] = -0.03
+/- 0.03. We also obtain the abundances of light metals (O, Na and Al),
alpha-elements (Mg, Si, Ca, Ti), elements of the Fe-group (Sc, Cr, Mn, Co, Ni)
and the neutron-capture element Ba. No intrinsic star-to-star scatter is
present in any of these elements within our sample. We compare our findings
with previous investigations on this cluster, discussing in detail differences
in analysis methods and results.


title: The fractal distribution of haloes

abstract:
  We examine the proposal that a model of the large-scale matter distribution
consisting of randomly placed haloes with power-law profile, as opposed to a
fractal model, can account for the observed power-law galaxy-galaxy
correlations. We conclude that such model, which can actually be considered as
a degenerate multifractal model, is not realistic but suggests a new picture of
multifractal models, namely, as sets of fractal distributions of haloes. We
analyse, according to this picture, the properties of the matter distribution
produced in cosmological N-body simulations, with affirmative results; namely,
haloes of similar mass have a fractal distribution with a given dimension,
which grows as the mass diminishes.


title:
Measuring the cosmic evolution of dark energy with baryonic oscillations
  in the galaxy power spectrum

abstract:
  We use Monte Carlo techniques to simulate the ability of future large
high-redshift galaxy surveys to measure the temporal evolution of the dark
energy equation-of-state w(z), using the baryonic acoustic oscillations in the
clustering power spectrum as a 'standard ruler'. Our analysis only utilizes the
oscillatory component of the power spectrum and not its overall shape, which is
potentially susceptible to broadband tilts induced by a host of model-dependent
systematic effects. Our results are therefore robust and conservative. We show
that baryon oscillation constraints can be thought of, to high accuracy, as a
direct probe of the distance - redshift and expansion rate - redshift relations
where distances are measured in units of the sound horizon. Distance precisions
of 1% are obtainable for a fiducial redshift survey covering 10,000 deg^2 and
redshift range 0.5 < z < 3.5. If the dark energy is further characterized by
w(z) = w_0 + w_1 z (with a cut-off in the evolving term at z = 2), we can then
measure the parameters w_0 and w_1 with a precision exceeding current knowledge
by a factor of ten: 1 sigma accuracies Delta w_0 ~ 0.03 and Delta w_1 ~ 0.06
are obtainable (assuming a flat universe and that the other cosmological
parameters Omega_m} and h could be measured independently to a precision of +/-
0.01 by combinations of future CMB and other experiments). We quantify how this
performance degrades with redshift/areal coverage and knowledge of Omega_m and
h, and discuss realistic observational prospects for such large-scale
spectroscopic redshift surveys, with a variety of diverse techniques. We also
quantify how large photometric redshift imaging surveys could be utilized to
produce measurements of (w_0,w_1) with the baryonic oscillation method which
may be competitive in the short term.


title:
Quantifying orbital migration from exoplanet statistics and host
  metallicities

abstract:
  We investigate how the statistical distribution of extrasolar planets may be
combined with knowledge of the host stars' metallicity to yield constraints on
the migration histories of gas giant planets. At any radius, planets that
barely manage to form around the lowest metallicity stars accrete their
envelopes just as the gas disk is being dissipated, so the lower envelope of
planets in a plot of metallicity vs semi-major axis defines a sample of
non-migratory planets that will have suffered less than average migration
subsequent to gap opening. Under the assumption that metallicity largely
controls the initial surface density of planetesimals, we use simplified core
accretion models to calculate how the minimum metallicity needed for planet
formation varies as a function of semi-major axis. Models that do not include
core migration prior to gap opening (Type I migration) predict that the
critical metallicity is largely flat between the snow line and a semimajor axis
of about 6 AU, with a weak dependence on the initial surface density profile of
planetesimals. When slow Type I migration is included, the critical metallicity
is found to increase steadily from 1-10 AU. Large planet samples, that include
planets at modestly greater orbital radii than present surveys, therefore have
the potential to quantify the extent of migration in both Type I and Type II
regimes.


title:
Feedback and Brightest Cluster Galaxy Formation: ACS Observations of the
  Radio Galaxy TN J1338--1942 at z=4.1

abstract:
  We present deep optical imaging of the z=4.1 radio galaxy TN J1338--1942
obtained using the ACS on-board HST. The radio galaxy is known to reside within
a large galaxy overdensity (both in physical extent and density contrast).
There is good evidence that this `protocluster' region is the progenitor of a
present-day rich galaxy cluster. TN J1338 is the dominant galaxy in the
protocluster, in terms of size and luminosity and therefore seems destined to
evolve into the brightest cluster galaxy. The high spatial-resolution ACS
images reveal several kpc-scale features within and around the radio galaxy.
The continuum light is aligned with the radio axis and is resolved into two
clumps in the i-band and z-band bands. These components have luminosities ~10^9
L_sun and sizes of a few kpc. The estimated star-formation rate for the whole
radio galaxy is ~200 M_sun/yr. A simple model in which the jet has triggered
star-formation in these continuum knots is consistent with the available data.
An unusual feature is seen in Lyman-alpha emission. A wedge-shaped extension
emanates from the radio galaxy perpendicularly to the radio axis. This `wedge'
naturally connects to the surrounding, asymmetric, large-scale (~100 kpc)
Lyman-alpha halo. We posit that the wedge is a starburst-driven superwind,
associated with the first major epoch of formation of the brightest cluster
galaxy. The shock and wedge are examples of feedback processes due to both AGN
and star-formation in the earliest stages of massive galaxy formation.


title: The Core-Collapse Supernova with "Non-Uniform" Magnetic Fields

abstract:
  We perform two-dimensional numerical simulations on the core-collapse of a
massive star with strong magnetic fields and differential rotations using a
numerical code ZEUS-2D. Changing field configurations and laws of differential
rotation parametrically, we compute 14 models and investigate effects of these
parameters on the dynamics. In our models, we do not solve the neutrino
transport and instead employ a phenomenological parametric EOS that takes into
account the neutrino emissions. As a result of the calculations, we find that
the field configuration plays a significant role in the dynamics of the core if
the initial magnetic field is large enough. Models with initially concentrated
fields produce more energetic explosions and more prolate shock waves than the
uniform field. Quadrapole-like fields produce remarkably collimated and fast
jet, which might be important for gamma-ray bursts(GRB). The Lorentz forces
exerted in the region where the plasma-beta is less than unity are responsible
for these dynamics. The pure toroidal field, on the other hand, does not lead
to any explosion or matter ejection. This suggests the presupernova models of
Heger et al.(2003), in which toroidal fields are predominant, is
disadvantageous for the magnetorotation-induced supernova considered here.
Models with initially weak magnetic fields do not lead to explosion or matter
ejection, either. In these models magnetic fields play no role as they do not
grow on the timescale considered in this paper so that the magnetic pressure
could be comparable to the matter pressure. This is because the exponential
field growth as expected in MRI is not seen in our models. The magnetic field
is amplified mainly by field-compression and field-wrapping in our simulations.


title: Cosmic ray threshold in an asymptotically dS spacetime

abstract:
  We discuss the threshold anomaly in ultra-high energy cosmic ray physics by
assuming that the matter world just be perturbation of a de Sitter universe,
which is consistent with the recent astronomical observations: about two thirds
of the whole energy in the universe is contributed by a small positive
cosmological constant. One-particle states are presented explicitly. It is
noticed that the dispersion relation of free particles is dependent on the
degrees of freedom of angular momentum. This fact can be regarded as the
effects of the cosmological constant on kinematics of particles.


title:
Bright OB stars in the Galaxy.II. Wind variability in O supergiants as
  traced by H-alpha

abstract:
  We investigate the line-profile variability (lpv) of H-alpha for a large
sample of O-type supergiants. We used the Temporal Variance Spectrum (TVS)
analysis, developed by Fullerton et al 1996 and modified by us to take into
account the effects of wind emission. By means of a comparative analysis we put
a number of constraints on the properties of the variability as a function of
stellar and wind parameters. The results of our analysis show that all the
stars in the sample show evidence of significant lpv in H-alpha, mostly
dominated by processes in the wind. The variations occur between zero and 0.3
v_inf (i.e., below ~1.5 R_star), in good agreement with the results from
similar studies. A comparison between observations and line-profile simulations
indicates that for stars with intermediate wind densities the H-alpha
variability can be explained by simple models, consisting of coherent or broken
shells (blobs) uniformly distributed over the wind volume, with an intrinsic
scatter in the maximum density contrast of about a factor of two. For stars at
lower and higher wind densities, on the other hand, we found certain
inconsistencies between observations and our predictions, most importantly
concerning the mean amplitude and the symmetry properties of the TVS. This
disagreement might be explained with the presence of coherent large-scale
structures, partly confined in a volume close to the star. Interpreted in terms
of a variable mass-loss rate, the observed variations of H-alpha indicate
changes of 4% with respect to the mean value of M_dot for stars with stronger
winds and of 16% for stars with weaker winds. The effect of these variations on
the corresponding wind momenta is rather insignificant (<0.16 dex), increasing
the local scatter without affecting the Wind Momentum Luminosity Relationship.


title: Spectral properties and origin of the radio halo in A3562

abstract:
  We present a new detailed multiband study of the merging cluster A3562, in
the core of the Shapley Concentration Supercluster. We analyzed new, low
frequency radio data performed at 240 MHz, 332 MHz and 610 MHz with the Giant
Metrewave Radio Telescope (GMRT). The new GMRT data allowed us to carry out a
detailed study of the radio halo at the centre of A3562, as well as of the
head--tail radio galaxy J1333--3141 embedded in it, and of the extended
emission around the peripheral cluster galaxy J1332--3146a. Thanks to the
present observations we could derive the integrated spectrum of the radio halo
with five data points in the frequency range 240 MHz -- 1.4 GHz. Our data show
a clear steepening of the total spectrum in this frequency range. Furthermore,
by comparing the GMRT 332 MHz image with a previously published VLA 1.4 GHz
image, we produced an image of the halo spectral index distribution. The image
shows a very complex structure, with an average value of
$\alpha^{1.4GHz}_{332MHz} \sim 1.5$ and a number of knots steepening up to
$\sim 2$. We performed a combined morphological and statistical analysis using
the radio images and the quantities derived from XMM--Newton and {\it Chandra}
observations. We discuss our results in the light of particle re--acceleration
processes in galaxy clusters. In particular, we outline an overall picture,
consistent with the available radio and X-ray data, in which the cluster merger
kinematics, the injection of turbulence and B--amplification induced by the
merger between A 3562 and SC 1329--313 are jointly taken into account.


title: Dark Energy Condensation

abstract:
  The two most popular candidates for dark energy, i.e. a cosmological constant
and quintessence, are very difficult to distinguish observationally, mostly
because the quintessence field does not have sizable fluctuations. We study a
scalar field model for dark energy in which the scalar field is invariant under
reflection symmetry, phi -> -phi. Under general assumptions, there is a phase
transition at late times (z < 0.5). Before the phase transition, the field
behaves as a cosmological constant. After the phase transition, a
time-dependent scalar condensate forms, the field couples with dark matter and
develops sizable perturbations tracking those of dark matter. The background
cosmological evolution is in agreement with existing observations, but might be
distinguished from that of a cosmological constant by future Supernovae
surveys. The growth of cosmological perturbations carries the imprint of the
phase transition, however a non-linear approach has to be developed in order to
study it quantitatively.


title:
Ultra High Energy Cosmic Rays from charged black holes. A new
  theoretical possibility?

abstract:
  In General Relativity, there is a new field of activity concerning the study
of charged stars. In a recent paper, Ray et al. have shown the possibility that
the collapse of a charged star could form a charged black hole before all the
charge leaves the system. In this field of view we propose a new model for
UHECR and we will show that it is possible to accelerate cosmic rays up to EeV.
In this talk we will compute the UHECR flux, the charged black hole density and
the energy spectrum associated with them in order to reproduce experimental
data. We will see that we need only a small number of these hidden sources in
order to account for observed UHECR properties and we will study the limits on
charge and mass of black holes.


title: The very young planetary nebula LS IV -12 111

abstract:
  In the last few years we have started a systematic study aimed at detecting
very young Planetary Nebulae (YPNs). The project, based on both radio
(multi-frequency and high resolution) and optical observations, has already
provided interesting results, including the identification of new YPNs and the
observation, for the first time in PN in this very early phase of their
formation, of radio bipolar morphologies.
  In this paper we present radio and optical results on one of our targets,
namely IRAS 19590-1249 (LS IV -12 111). The analysis of spectroscopic
observations, obtained with the Anglo Australian Telescope (AAT) in different
epochs, has allowed us to conclude that the optical spectrum of this object has
evolved quite rapidly, showing, very recently, strong forbidden nebular
emission lines consistent with a young PN. This result confirms that IRAS
19590-1249, has turned into a PN within the last decades and makes this source
a perfect target for studying the early evolution and structure of Planetary
Nebulae.


title: The Accretion of Dark Energy onto a Black Hole

abstract:
  The stationary, spherically symmetric accretion of dark energy onto a
Schwarzschild black hole is considered in terms of relativistic hydrodynamics.
The approximation of an ideal fluid is used to model the dark energy. General
expressions are derived for the accretion rate of an ideal fluid with an
arbitrary equation of state p=p(\rho) onto a black hole. The black hole mass
was found to decrease for the accretion of phantom energy. The accretion
process is studied in detail for two dark energy models that admit an
analytical solution: a model with a linear equation of state,
p=\alpha(\rho-\rho_0), and a Chaplygin gas. For one of the special cases of a
linear equation of state, an analytical expression is derived for the accretion
rate of dark energy onto a moving and rotating black hole. The masses of all
black holes are shown to approach zero in cosmological models with phantom
energy in which the Big Rip scenario is realized.


title: Formation of HD molecules in merging dark matter haloes

abstract:
  HD molecules can be an important cooling agent of the primordial gas behind
the shock waves originated through mergings of the dark matter haloes at epochs
when first luminous objects were to form. We study the necessary conditions for
the HD cooling to switch on in the low temperature range $T<200$ K. We show
that these conditions are fulfiled in merging haloes with the total (dark
matter and baryon) mass in excess of $M_{\rm cr}\sim 10^7[(1+z)/20]^{-2}\msun$.
Haloes with masses $M>M_{\rm cr}$ may be the sites of low-mass star formation.


title: The Shape-Alignment relation in $\Lambda$CDM Cosmic Structures

abstract:
  In this paper we study the supercluster - cluster morphological properties
using one of the largest ($2\times 512^{3}$ SPH+N-body simulations of large
scale structure formation in a $\Lambda$CDM model, based on the publicly
available code GADGET. We find that filamentary (prolate-like) shapes are the
dominant supercluster and cluster dark matter halo morphological feature, in
agreement with previous studies. However, the baryonic gas component of the
clusters is predominantly spherical. We investigate the alignment between
cluster halos (using either their DM or baryonic components) and their parent
supercluster major-axis orientation, finding that clusters show such a
preferential alignment. Combining the shape and the alignment statistics, we
also find that the amplitude of supercluster - cluster alignment increases
although weakly with supercluster filamentariness.


title:
Photodissociation of water in crystalline ice: a molecular dynamics
  study

abstract:
  Ultraviolet irradiation of ice is of great interest for understanding the
chemistry in both atmospheric and astrophysical environments. In interstellar
space, photodissociation of H2O molecules can be a driving force behind the
chemistry on icy dust grains in dense, cold molecular clouds even though the
flux of UV photons is extremely low. The mechanisms of such photoinduced
processes are poorly understood, however. In this work the photodissociation
dynamics of a water molecule in crystalline ice at 10 K is studied
computationally using classical molecular dynamics. Photodissociation in the
first bilayer leads mainly to H atoms desorbing (65%), while in the third
bilayer trapping of H and OH dominates (51%). The kinetic energy distribution
of the desorbing H atoms is much broader than that for the corresponding
gas-phase photodissociation. The H atoms on average move 11 Angstroms before
becoming trapped, while OH radicals typically move 2 Angstroms. In accordance
with experiments a blueshift of the absorption spectrum is obtained relative to
gas-phase water.