title:
Possibility of a White Dwarf as the Accreting Compact Star in CI Cam (=
  XTE J0421+560)

abstract:
  We present results from ASCA observations of the binary CI Cam both in
quiescence and in outburst in order to identify its central accreting object.
The quiescence spectrum of CI Cam consists of soft and hard components which
are separated clearly at aound 2-3keV. A large equivalent width of an iron Ka
emission line prefers an optically thin thermal plasma emission model to a
non-thermal power-law model for the hard component, which favors a white dwarf
as the accreting object, since the optically thin thermal hard X-ray emission
is a common characteristic among cataclysmic variables (binaries including an
accreting white dwarf).
  The outburst spectrum, on the other hand, is composed of a hard component
represented by a multi-temperature optically thin thermal plasma emission and
of an independent soft X-ray component that appears below 1 keV intermittently
on a decaying light curve of the hard component. The spectrum of the soft
component is represented well by a blackbody with the temperature of
0.07-0.12keV overlaid with several K-edges associated with highly ionized
oxygen. This, together with the luminosity as high as ~1E38 erg/s is similar to
a super-soft source (SSS). The outburst in the hard X-ray band followed by the
appearance of the soft blackbody component reminds us of recent observations of
novae in outburst. We thus assume the outburst of CI Cam is that of a nova, and
obtain the distance to CI Cam to be 5-17kpc by means of the relation between
the optical decay time and the absolute magnitude. This agrees well with a
recent estimate of the distance of 5-9kpc in the optical band. All of these
results from the outburst data prefer a white dwarf for the central object of
CI Cam.


title:
Revealing a Cool Accretion Disk in the Ultraluminous X-ray Source M81
  X-9 (Holmberg IX X-1): Evidence for an Intermediate Mass Black Hole

abstract:
  We report the results of an analysis of two XMM-Newton/EPIC-pn spectra of the
bright ultraluminous X-ray source M81 X-9 (Holmberg IX X-1), obtained in
snapshot observations. Soft thermal emission is clearly revealed in spectra
dominated by hard power-law components. Depending on the model used, M81 X-9
was observed at a luminosity of L_X = 1.0-1.6 E+40 erg/s (0.3--10.0 keV). The
variability previously observed in this source signals that it is an accreting
source which likely harbors a black hole. Remarkably, accretion disk models for
the soft thermal emission yield very low inner disk temperatures (kT =
0.17-0.29 keV, including 90% confidence errors and variations between
observations and disk models), and improve the fit statistic over any
single-component continuum model at the 6 sigma level of confidence. Like NGC
1313 X-1, scaling the temperatures measured in M81 X-9 to those commonly seen
in stellar-mass Galactic black holes at their highest observed fluxes (kT ~ 1
keV) may imply that M81 X-9 harbors a black hole with a mass on the order of
10^3 Msun; the measured disk component normalization and broad-band luminosity
imply black hole masses on the order of 10^2 Msun. It is therefore possible
that these sources harbor 10^3 Msun black holes accreting such at L_X ~
0.1*L_Edd. Radio and optical observations suggest that beaming and anisotropic
emission from a stellar-mass black hole are unlikely to account for the implied
luminosity. We further argue that the strength of the hard emission in these
sources and well-established phenomena frequently observed in stellar-mass
black holes near to the Eddington limit suggest that optically-thick
photospheres are unlikely to be the origin of the cool thermal emission in
bright ULXs.


title: Dynamics of capture in the restricted three-body problem

abstract:
  We propose a new dynamical model for capture of irregular moons which
identifies chaos as the essential feature responsible for initial temporary
gravitational trapping within a planet's Hill sphere. The key point is that
incoming potential satellites get trapped in chaotic orbits close to "sticky"
KAM tori in the neighbourhood of the planet, possibly for very long times, so
that the chaotic layer largely dictates the final orbital properties of
captured moons.


title: Synthetic Spectrum Methods for Three-Dimensional Supernova Models

abstract:
  Current observations stimulate the production of fully three-dimensional
explosion models, which in turn motivates three-dimensional spectrum synthesis
for supernova atmospheres. We briefly discuss techniques adapted to address the
latter problem, and consider some fundamentals of line formation in supernovae
without recourse to spherical symmetry. Direct and detailed extensions of the
technique are discussed, and future work is outlined.


title: The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda II

abstract:
  (abridged) We present the results of a variable star search in Andromeda II,
a dwarf spheroidal galaxy companion to M31, using HST/WFPC2 observations.
Seventy-three variables were found, one of which is an anomalous Cepheid while
the others are RR Lyrae stars. The anomalous Cepheid has properties consistent
with those found in other dwarf spheroidal galaxies. For the RR Lyrae stars,
the mean periods are 0.571 day and 0.363 day for the fundamental mode and
first-overtone mode stars, respectively. With this fundamental mode mean period
and the mean metallicity determined from the red giant branch (<[Fe/H]>=-1.49),
Andromeda II follows the period-metallicity relation defined by the Galactic
globular clusters and other dwarf spheroidal galaxies. We also find that the
properties of the RR Lyrae stars themselves indicate a mean abundance that is
consistent with that determined from the red giants. There is, however, a
significant spread among the RR Lyrae stars in the period-amplitude diagram,
which is possibly related to the metallicity spread in Andromeda II indicated
by the width of the red giant branch in Da Costa et al. In addition, the
abundance distribution of the RR Lyrae stars is notably wider than the
distribution expected from the abundance determination errors alone. The mean
magnitude of the RR Lyrae stars, <V_RR>=24.87+/-0.03, implies a distance
d=665+/-20 kpc to Andromeda II. We also demonstrate that the specific frequency
of anomalous Cepheids in dwarf spheroidal galaxies correlates with the mean
metallicity of their parent galaxy, and that the Andromeda II and Andromeda VI
anomalous Cepheids appear to follow the same relation as those in the Galactic
dwarf spheroidals.


title: Curvature radiation in pulsar magnetospheric plasma

abstract:
  We consider the curvature radiation of the point-like charge moving
relativistically along curved magnetic field lines through a pulsar
magnetospheric electron-positron plasma. We demonstrate that the radiation
power is largely suppressed as compared with the vacuum case, but still at a
considerable level, high enough to explain the observed pulsar luminosities.
The emitted radiation is polarized perpendicularly to the plane of the curved
magnetic filed lines coincides with $ which can freely escape from the
magnetospheric plasma. Our results strongly support the coherent curvature
radiation by the spark-associated solitons as a plausible mechanism of pulsar
radio emission.


title:
The Formation of the First Low-Mass Stars From Gas With Low Carbon and
  Oxygen Abundances

abstract:
  The first stars in the Universe are predicted to have been much more massive
than the Sun. Gravitational condensation accompanied by cooling of the
primordial gas due to molecular hydrogen, yields a minimum fragmentation scale
of a few hundred solar masses. Numerical simulations indicate that once a gas
clump acquires this mass, it undergoes a slow, quasi-hydrostatic contraction
without further fragmentation. Here we show that as soon as the primordial gas
- left over from the Big Bang - is enriched by supernovae to a carbon or oxygen
abundance as small as ~0.01-0.1% of that found in the Sun, cooling by
singly-ionized carbon or neutral oxygen can lead to the formation of low-mass
stars. This mechanism naturally accommodates the discovery of solar mass stars
with unusually low (10^{-5.3} of the solar value) iron abundance but with a
high (10^{-1.3} solar) carbon abundance. The minimum stellar mass at early
epochs is partially regulated by the temperature of the cosmic microwave
background. The derived critical abundances can be used to identify those
metal-poor stars in our Milky Way galaxy with elemental patterns imprinted by
the first supernovae.


title: Emission and absorption in Narrow-Line Seyfert 1 Galaxies

abstract:
  The emission and absorption attributes of the UV-blue nuclear spectra of the
Narrow-Line Seyfert 1 (NLS1) galaxies are analyzed based on high quality
archival HST observations. Measurements from composite spectra as well as from
individual sources reveal differences from the more general AGN samples: NLS1s
have steeper (redder) UV-blue continua. Objects with UV line absorption show
redder spectra, suggesting that internal dust is important in modifying the
continuum shapes. A strong relationship is found between the slopes of the
power-laws that best fit the UV-blue continua and the luminosities: the more
luminous sources have bluer SEDs. This trend is possibly attributed to a
luminosity-dependent inner geometry of the obscuring (dusty) material.


title:
Self-Consistent R-matrix Approach To Photoionization And Unified
  Electron-Ion Recombination

abstract:
  A unified scheme using the R-matrix method has been developed for
electron-ion recombination subsuming heretofore separate treatments of
radiative and dielectronic recombination (RR and DR). The ab initio coupled
channel approach unifies resonant and non-resonant phenomena, and enables a
general and self-consistent treatment of photoionization and electron-ion
recombination employing idential wavefunction expansion. Detailed balance takes
account of interference effects due to resonances in cross sections, calculated
explicitly for a large number of recombined (e+ion) bound levels over extended
energy regions. The theory of DR by Bell and Seaton is adapted for high-n
resonances in the region below series limits. The R-matrix method is employed
for (A) partial and total photoionization and photorecombination cross sections
of (e+ion) bound levels, and (B) DR and (e+ion) scattering cross sections.
Relativistic effects and fine structure are considered in the Breit-Pauli
approximation. Effects such as radiation damping may be taken into account
where necessary. Unfiied recombination cross sections are in excellent
agreement with measurements on ion storage rings to about 10-20%. In addition
to high accuracy, the strengths of the method are: (I) both total and
level-specific cross sections and rate coefficients are obtained, and (II) a
single (e+ion) recombination rate coefficient for any given atom or ion is
obtained over the entire temperature range of practical importance in
laboratory and astrophysical plasmas, (III) self-consistent results are
obtained for photoionization and recombination; comprehensive datasets have
been computed for over 50 atoms and ions. Selected data are presented for iron
ions.


title: Accelerator Experiments for Astrophysics

abstract:
  Many recent discoveries in astrophysics involve phenomena that are highly
complex. Carefully designed experiments, together with sophisticated computer
simulations, are required to gain insights into the underlying physics. We show
that particle accelerators are unique tools in this area of research, by
providing precision calibration data and by creating extreme experimental
conditions relevant for astrophysics. In this paper we discuss laboratory
experiments that can be carried out at the Stanford Linear Accelerator Center
and implications for astrophysics.


title: 1993 Superoutburst of LL Andromedae

abstract:
  We present time-resolved CCD photometry of LL And during its 1993 outburst.
The observation revealed the presence of superhumps with a period of 0.05697(3)
d. This period is one of the smallest among the hydrogen-rich dwarf novae.
Although LL And has been proposed to be a WZ Sge-type dwarf nova based on its
low outburst frequency, our new analysis indicates that the outburst amplitude
(~5 mag) and outburst duration (9+/-2 d) are much smaller and shorter than in
typical WZ Sge-type dwarf novae. We suspect that the unusual outburst
properties of LL And might be explained by assuming a "leaky disk" in
quiescence, which was originally proposed to explain the prototypical WZ
Sge-type outbursts. By combination with the recent suggestion of the orbital
period, the fractional superhump excess is found to be 3.5(1)%, which is
unusually large for this short-period system. LL And may be an object filling
the gap in the evolutionary track, which has recently been proposed to explain
the unusual ultracompact binaries with an evolved mass donor.


title: Mid- to Far-Infrared spectroscopy of Sharpless 171

abstract:
  We have collected one-dimensional raster-scan observations of the active
star-forming region Sharpless 171 (S171), a typical HII region-molecular cloud
complex, with the three spectrometers (LWS, SWS, and PHT-S) on board ISO. We
have detected 8 far-infrared fine-structure lines, [OIII] 52um, [NIII] 57um,
[OI] 63um, [OIII] 88um, [NII] 122um, [OI] 146um, [CII] 158um, and [SiII] 35um
together with the far-infrared continuum and the H2 pure rotation transition
(J=5-3) line at 9.66um. The physical properties of each of the three phases
detected, highly-ionized, lowly-ionized and neutral, are investigated through
the far-infrared line and continuum emission. Toward the molecular region,
strong [OI] 146um emission was observed and the [OI] 63um to 146um line ratio
was found to be too small (about 5) compared to the values predicted by current
photodissociation region (PDR) models. We examine possible mechanisms to
account for the small line ratio and conclude that the absorption of the [OI]
63um and the [CII] 158um emission by overlapping PDRs along the line of sight
can account for the observations and that the [OI] 146um emission is the best
diagnostic line for PDRs. We propose a method to estimate the effect of
overlapping clouds using the far-infrared continuum intensity and derive the
physical properties of the PDR. The [SiII] 35um emission is quite strong at
almost all the observed positions. The correlation with [NII] 122um suggests
that the [SiII] emission originates mostly from the ionized gas. The [SiII]
35um to [NII] 122um ratio indicates that silicon of 30% of the solar abundance
must be in the diffuse ionized gas, suggesting that efficient dust destruction
is undergoing in the ionized region.


title: On the colour-colour properties of the Extremely Red Objects

abstract:
  The colours of the galaxy class known as Extremely Red Objects (EROs; R-K>5)
are considered to be consistent with two distinct galaxy populations at high
redshift: evolved ellipticals or young dusty starbursts. In this paper the
properties of EROs, spanned by the five photometric bands RIJHK, are
investigated as to the possibility to distinguish between these two galaxy
populations using only broad band photometry. The broad band colours of
elliptical and starburst galaxies at redshifts up to 5 are computed from
synthetic spectra obtained using the spectral evolution synthesis programme
PEGASE.2. Two initial mass functions and a range of metallicities and
extinctions are used. In order to be extremely red in the redshift range
considered, the evolution of the R-K colour sets the requirement that
ellipticals have to be less than 7-8 Gyr old, and that the starbursts must have
colour excesses of E(B-V)>1, as derived from the nebular emission lines. In
investigating the overlap in the different colour-colour planes as a function
of redshift, it is found that the planes formed from permutations of the same
three filters exhibit very similar overlap characteristics. In colour-colour
planes formed within such triplets one of the filters will serve as a "pivot"
band against which the two other bands are compared. The configuration where
this pivot band lies between the other two bands has the best performance as a
discriminator among the three possible configurations. A consistent behaviour
cannot be found among the configurations formed by permuting four filters. The
minimal filter configuration R-H vs. H-K is found to be the very best
discriminator, working as such up to redshift 2.9.


title: Gas outflows in radio galaxies

abstract:
  We present a summary of our recent results on gas outflows in radio galaxies.
Fast outflows (up to 2000 km/s) have been detected both in ionized and neutral
gas. The latter is particularly surprising as it shows that, despite the
extremely energetic phenomena occurring near an AGN, some of the outflowing gas
remains, or becomes again, neutral. These results are giving new and important
insights on the physical conditions of the gaseous medium around an AGN.


title:
Very compact radio emission from high-mass protostars. I. CRL 2136:
  Continuum and water maser observations

abstract:
  We report 5-43 GHz radio observations of the CRL 2136 region at 0.6-6 arcsec
resolution. We detect weak (mJy intensity) radio emission from the deeply
embedded high-mass protostar IRS 1, which has an optically thick spectrum up to
frequencies of 22 GHz, flattening at higher frequencies, which might be
explained by emission from a jet. Water maser mapping shows that the strong
emission observed redshifted relative to the systemic velocity is spatially
coincident with the optically thick continuum emission. The H2O maser emission
from this object (and others we know of) seems to have a different origin than
most of these masers, which are frequently tracing bipolar high-velocity
outflows. Instead, the CRL 2136 H2O emission arises in the close circumstellar
environment of the protostar (within 1000 AU). We speculate that most of it is
excited in the hot, dense infalling gas after the accretion shock, although
this cannot explain all the H2O emission. An accretion shock nature for the
continuum emission seems unlikely.


title: ce-61: a Tidal Dwarf Galaxy in the Hercules cluster?

abstract:
  A candidate Tidal Dwarf Galaxy, ce-61, was identified in the merger system IC
1182 in the Hercules supercluster. The multi-wavelength data we obtained so far
do not prove, however, that it is kinematically detached from the IC 1182
system and gravitationally bound.


title: Tidal Remnants and Intergalactic HII Regions

abstract:
  We report the discovery of two small intergalactic HII regions in the loose
group of galaxies around the field elliptical NGC 1490. The HII regions are
located at least 100 kpc from any optical galaxy but are associated with a
number of large HI clouds that are lying along an arc 500 kpc in length and
that have no optical counterpart on the Digital Sky Survey. The sum of the HI
masses of the clouds is almost 10^10 M_sun and the largest HI cloud is about
100 kpc in size. Deep optical imaging reveals a very low surface brightness
counterpart to this largest HI cloud, making this one of the HI richest optical
galaxies known (M_HI/L_V~200). Spectroscopy of the HII regions indicates that
the abundance in these HII regions is only slightly sub-solar, excluding a
primordial origin of the HI clouds. The HI clouds are perhaps remnants
resulting from the tidal disruption of a reasonably sized galaxy, probably
quite some time ago, by the loose group to which NGC1490 belongs.
Alternatively, they are remnants of the merger that created the field
elliptical NGC1490. The isolated HII regions show that star formation on a very
small scale can occur in intergalactic space in gas drawn from galaxies by
tidal interactions. Many such intergalactic small star formation regions may
exist near tidally interacting galaxies.


title: From Large to Small Scales: Global Models of the ISM

abstract:
  We review large scale modelling of the ISM with emphasis on the importance to
include the disk-halo-disk duty cycle and to use a dynamical refinement of the
grid (in regions where steep variations of density and pressure occur) for a
realistic modelling of the ISM. We also discuss the necessity of convergence of
the simulation results by comparing 0.625, 1.25 and 2.5 pc resolution
simulations and show that a minimum grid resolution of 1.25 pc is required for
quantitatively reliable results, as there is a rapid convergence for Delta x
\leq 1.1 pc.


title:
MHD Simulations of the ISM: The Importance of the Galactic Magnetic
  Field on the ISM "Phases"

abstract:
  We have carried out 1.25 pc resolution MHD simulations of the ISM, on a
Cartesian grid of $0 \leq (x,y) \leq 1$ kpc size in the galactic plane and $-10
\leq z \leq 10$ kpc into the halo, thus being able to fully trace the
time-dependent evolution of the galactic fountain. The simulations show that
large scale gas streams emerge, driven by SN explosions, which are responsible
for the formation and destruction of shocked compressed layers. The shocked gas
can have densities as high as 800 cm$^{-3}$ and lifetimes up to 15 Myr. The
cold gas is distributed into filaments which tend to show a preferred
orientation due to the anisotropy of the flow induced by the galactic magnetic
field. Ram pressure dominates the flow in the unstable branch $10^{2}<$T$\leq
10^{3.9}$ K, while for T$\leq 100$ K (stable branch) magnetic pressure takes
over. Near supernovae thermal and ram pressures determine the dynamics of the
flow. Up to 80% of the mass in the disk is concentrated in the thermally
unstable regime $10^{2}<$T$\leq 10^{3.9}$ K with $\sim30%$ of the disk mass
enclosed in the T$\leq 10^{3}$ K gas. The hot gas in contrast is controlled by
the thermal pressure, since magnetic field lines are swept towards the dense
compressed walls.


title: High-redshift X-ray properties of the haloes of simulated disc galaxies

abstract:
  X-ray luminosities and surface brightness profiles of the hot gas haloes of
simulated disc galaxies at redshifts z=0-2 are presented. The galaxies are
extracted from fully cosmological simulations and correspond in mass to the
Milky Way. We find that the bolometric X-ray luminosities of the haloes
decrease by a factor 4-10 from z~1 to z~0, reflecting the decrease in the rate
at which hot halo gas cools out on to the disc. At all redshifts, most of the
emission is found to originate within 10-15 kpc of the disc. When combined with
models in which the evolution of disc X-ray luminosity is dominated by X-ray
binaries, the predicted halo luminosities at z~1 show good agreement with
constraints from spiral galaxies in Chandra Deep Field data. There is an
indication that haloes with a metal abundance of 0.3 solar overpredict observed
X-ray luminosities at z~1, suggesting that halo metallicities are lower than
this value. Prospects for direct detection of the haloes of Milky Way-sized
galaxies with current and future X-ray instrumentation are discussed. It is
found that XEUS should be able to single out the halo emission of highly
inclined Milky Way-sized disc galaxies out to approximately z=0.3. For such
galaxies in this redshift interval, we estimate a lower limit to the surface
density of detectable haloes on the sky of ~10 deg^(-2). More generally, owing
to their luminosity evolution, the optimum redshifts at which to observe such
haloes could be 0.5<z<1, depending on their assembly history.


title: Physics of ultrahigh energy neutrinos

abstract:
  Ultrahigh energy neutrinos can provide important information about the
distant astronomical objects and the origin of the Universe. Precise knowledge
about their interactions and production rates is essential for estimating
background, expected fluxes and detection probabilities. In this paper we
review the applications of the high energy QCD to the calculations of the
interaction cross sections of the neutrinos. We also study the production of
the ultrahigh energy neutrinos in the atmosphere due to the charm and beauty
decays.


title:
Photometric Mapping with ISOPHOT using the "P32" Astronomical
  Observation Template

abstract:
  The ``P32'' Astronomical Observation Template (AOT) provided a means to map
large areas of sky (up to 45 x 45 arcmin) in the far-infrared (FIR) at high
redundancy and with sampling close to the Nyquist limit using the ISOPHOT C100
(3 x 3) and C200 (2 x 2) detector arrays on board the Infrared Space
Observatory (ISO). However, the transient response behaviour of the Ga:Ge
detectors, if uncorrected, can lead to severe systematic photometric errors and
distortions of source morphology on maps. We describe the basic concepts of an
algorithm which can successfully correct for transient response artifacts in
P32 observations. Examples are given to demonstrate the photometric and imaging
performance of ISOPHOT P32 observations of point and extended sources corrected
using the algorithm. For extended sources we give the integrated flux densities
of the nearby galaxies NGC6946, M51 and M101 and an image of M101 at 100
micron.


title: Detecting the WIMP-wind via spin-dependent interactions

abstract:
  Revealing the nature of dark matter is one of the most interesting tasks in
astrophysics. Measuring the distribution of recoil angles is said to be one of
the most reliable methods to detect a positive signature of dark matter. We
focused on measurements via spin-dependent interactions, and studied the
feasibility with carbon tetrafluoride($\rm CF_4$) gas, while taking into
account the performance of an existing three-dimensional tracking detector. We
consequently found that it is highly possible to detect a positive signature of
dark matter via spin-dependent interactions.


title: The distance to the giant elliptical galaxy NGC 5128

abstract:
  The distance to NGC 5128, the central galaxy of the Centaurus group and the
nearest giant elliptical to us, has been determined using two independent
distance indicators: the Mira period-luminosity (PL) relation and the
luminosity of the tip of the red giant branch (RGB). The data were taken at two
different locations in the halo of NGC 5128 with the ISAAC near-IR array on ESO
VLT. From more than 20 hours of observations with ISAAC a very deep Ks-band
luminosity function was constructed. The tip of the RGB is detected at Ks=21.24
\pm 0.05 mag. Using an empirical calibration of the K-band RGB tip magnitude,
and assuming a mean metallicity of [M/H]=-0.4 dex and reddening of E(B-V)=0.11,
a distance modulus of NGC 5128 of (m-M)_0=27.87 \pm 0.16 was derived. The
comparison of the H-band RGB tip magnitude in NGC 5128 and the Galactic Bulge
implies a distance modulus of NGC 5128 of (m-M)_0=27.9 \pm 0.2 in good
agreement with the K-band RGB tip measurement. The population of stars above
the tip of the RGB amounts to 2176 stars in the outer halo field and 6072 stars
in the inner halo field. The large majority of these sources belong to the
asymptotic giant branch (AGB) population in NGC 5128 with numerous long period
variables. Mira variables were used to determine the distance of NGC 5128 from
a period-luminosity relation calibrated using the Hipparcos parallaxes and LMC
Mira period-luminosity relation in the K-band. This is the first Mira
period-luminosity relation outside the Local Group. A distance modulus of 27.96
\pm 0.11 was derived, adopting the LMC distance modulus of 18.50 \pm 0.04. The
mean of the two methods yields a distance modulus to NGC 5128 of 27.92 \pm 0.19
corresponding to D=3.84 \pm 0.35 Mpc.


title:
Searching for sub-millisecond pulsars from highly polarized radio
  sources

abstract:
  Pulsars are among the most highly polarized sources in the universe. The NVSS
has catalogued 2 million radio sources with linear polarization measurements,
from which we have selected 253 sources, with polarization percentage greater
than 25%, as targets for pulsar searches. We believe that such a sample is not
biased by selection effects against ultra-short spin or orbit periods. Using
the Parkes 64m telescope, we conducted searches with sample intervals of 0.05
ms and 0.08 ms, sensitive to submillisecond pulsars. Unfortunately we did not
find any new pulsars.


title: X-ray time lags from a pivoting power law in black holes

abstract:
  Most black hole candidate X-ray binaries show Fourier time lags between
softer and harder X-rays. The hard photons seem to arrive up to a few ms after
the soft for a given Fourier frequency of the perturbation. The energy
dependence of the time lags has a roughly logarithmic behavior. Up to now most
theories fail to explain the observed magnitude and Fourier frequency
dependence of the lags or fail other statistical tests. We show that the time
lags can arise from a simple pivoting power law model, which creates the
logarithmic dependence on the photon energy at once. A pivoting power law
arises naturally from jet/synchrotron models for the X-ray emission, but may
also be applicable to corona models. A hint to the coherence features of the
light-curves can be obtained from the power spectral density, which can be
decomposed into a few broad Lorentzians that could arise from a couple of
strongly damped oscillators with low quality factors below one. Using small
variations of the power law index for each Lorentzian separately the lags can
be derived analytically. They show the correct Fourier frequency dependence of
the time lags. If one assumes variations of the power law index by +- 0.2 the
model can account for the observed magnitude of the time lags in Cyg X-1. As a
further test we calculated the cross- and auto-correlation functions for our
model, which also show qualitatively the observed behavior. The coherence
function for the model is in agreement with the observed data in the Fourier
regime, where the model is valid.


title: Measuring our universe from galaxy redshift surveys

abstract:
  Galaxy redshift surveys have achieved significant progress over the last
couple of decades. Those surveys tell us in the most straightforward way what
our local universe looks like. While the galaxy distribution traces the bright
side of the universe, detailed quantitative analyses of the data have even
revealed the dark side of the universe dominated by non-baryonic dark matter as
well as more mysterious dark energy (or Einstein's cosmological constant). We
describe several methodologies of using galaxy redshift surveys as cosmological
probes, and then summarize the recent results from the existing surveys.
Finally we present our views on the future of redshift surveys in the era of
Precision Cosmology.


title: Boundary Inflation in the Moduli Space Approximation

abstract:
  The evolution of slow--roll inflation in a five--dimensional brane world
model with two boundary branes and bulk scalar field is studied. Assuming that
the inflationary scale is below the brane tension, we can employ the moduli
space approximation to study the dynamics of the system. Detuning the brane
tension results in a potential for the moduli fields which we show will not
support a period of slow--roll inflation. We then study an inflaton field,
confined to the positive tension brane, to which the moduli fields are
non--minimally coupled. We discuss in detail the two cases of $V(\chi) = {1/2}
m^2 \chi^2$ and $V(\chi) = \lambda \chi^4$ and demonstrate that increasing the
coupling results in spectra which are further away from scale--invariance and
in an increase in the tensor mode production, while entropy perturbations are
subdominant. Finally, we point out that the five--dimensional spacetime is
unstable during inflation because the negative tension brane collapses.


title:
Low-Surface-Brightness Galaxies in the Sloan Digital Sky Survey. I.
  Search Method and Test Sample

abstract:
  In this paper we present results of a pilot study to use imaging data from
the Sloan Digital Sky Survey (SDSS) to search for low-surface-brightness (LSB)
galaxies. For our pilot study we use a test sample of 92 galaxies from the
catalog of Impey et al. (1996) distributed over 93 SDSS fields of the Early
Data Release (EDR). Many galaxies from the test sample are either LSB or dwarf
galaxies. To deal with the SDSS data most effectively a new photometry software
was created, which is described in this paper. We present the results of the
selection algorithms applied to these 93 EDR fields. Two galaxies from the
Impey et al. test sample are very likely artifacts, as confirmed by follow-up
imaging. With our algorithms, we were able to recover 87 of the 90 remaining
test sample galaxies, implying a detection rate of $\sim$96.5%. The three
missed galaxies fall too close to very bright stars or galaxies. In addition,
42 new galaxies with parameters similar to the test sample objects were found
in these EDR fields (i.e., $\sim$47% additional galaxies). We present the main
photometric parameters of all identified galaxies and carry out first
statistical comparisons. We tested the quality of our photometry by comparing
the magnitudes for our test sample galaxies and other bright galaxies with
values from the literature. All these tests yielded consistent results. We
briefly discuss a few unusual galaxies found in our pilot study, including an
LSB galaxy with a two-component disk and ten new giant LSB galaxies.


title: SAURON dynamical modeling of NGC 2974

abstract:
  We present dynamical modeling of nearby E4 galaxy NGC 2974. The galaxy was
observed with the integral-field spectrograph SAURON. An axisymmetric stellar
dynamical model is constructed using a three-integral orbit superposition
Schwarschild modeling technique. We explore the dynamical structure and
investigate the distribution and dynamics of the gas.


title:
On the age and mass function of the globular cluster M4: a different
  interpretation of recent deep HST observations

abstract:
  Very deep images of the Galactic globular cluster M4 (NGC 6121) through the
F606W and F814W filters were taken in 2001 with the WFPC2 on board the HST. A
first published analysis of this data set (Richer et al. 2002) produced the
result that the age of M4 is 12.7 +/- 0.7 Gyr (Hansen et al. 2002), thus
setting a robust lower limit to the age of the universe. In view of the great
astronomical importance of getting this number right, we have subjected the
same data set to the simplest possible photometric analysis that completely
avoids uncertain assumptions about the origin of the detected sources. This
analysis clearly reveals both a thin main sequence, from which can be deduced
the deepest statistically complete mass function yet determined for a globular
cluster, and a white dwarf (WD) sequence extending all the way down to the 5
sigma detection limit at I~27. The WD sequence is abruptly terminated at
exactly this limit as expected by detection statistics. Using our most recent
theoretical WD models (Prada Moroni & Straniero 2002) to obtain the expected WD
sequence for different ages in the observed bandpasses, we find that the data
so far obtained do not reach the peak of the WD luminosity function, thence
only allowing one to set a lower limit to the age of M4 of ~9 Gyr. Thus, the
problem of determining the absolute age of a globular cluster and, therefore,
the onset of GC formation with cosmologically significant accuracy remains
completely open. Only observations several magnitudes deeper than the limit
obtained so far would allow one to approach this objective.


title:
Optical Continuum Variability of the Active Galaxy Mrk 279 -
  Implications for Different Accretion Regimes

abstract:
  We present results from a recent broad-band monitoring in optics of the
Seyfert 1 type galaxy Mrk 279. We build and analyse the BVRI light curve
covering a period of seven years (1995 - 2002). We also show some evidence for
the existence of two different states in brightness and suggest, based on a
modelling of the optical continuum, that these states may result from
transition between a thin disk and an ADAF accretion modes. We assume that the
short-term variability is due to a reprocessing of a variable X-ray emission
from an inner ADAF part of the flow, while the long-term one may be a result
from a change of the transition radius. Our tests show a good match with the
observations for a reasonable set of accretion parameters, rather close to the
ones, expected for Mrk 279.


title: Volume-limited SDSS/FIRST quasars and the radio dichotomy

abstract:
  Much evidence has been presented in favor of and against the existence of two
distinct populations of quasars, radio-loud and radio-quiet. The SDSS differs
from earlier optically selected quasar surveys in the large number of quasars
and the targeting of FIRST radio source counterparts as quasar candidates. This
allows a qualitatively different approach of constructing a series of samples
at different redshifts which are volume-limited with respect to both radio and
optical luminosity. This technique avoids any biases from the strong evolution
of quasar counts with redshift and potential redshift-dependent selection
effects. We find that optical and radio luminosities of quasars detected in
both SDSS and FIRST are not well correlated within each redshift shell,
although the fraction of radio detections among optically selected quasars
remains roughly constant at 10% for z <= 3.2. The distribution in the
luminosity-luminosity plane does not appear to be strongly bimodal. The optical
luminosity function is marginally flatter at higher radio luminosities.


title:
Active Galaxies With Double-Peaked Emission Lines and What They Imply
  About the "Broad-Line Region"

abstract:
  I review the distinguishing observational characteristics of active galaxies
with double-peaked emission lines and their implications for the nature of the
line-emitting region. Since double-peaked lines most likely originate in the
outer parts of the accretion disk, they can be used to study the structure and
dynamics of the disk and the associated wind. Such studies lead to general
inferences about the broad-line regions of all AGNs. To this end, I describe
the results of recent UV spectroscopy of double-peaked emitters that probes the
disk-wind relation. I also summarize efforts to exploit the variability of the
lines to study dynamical and thermal phenomena in the disk.


title: CMB Polarization as complementary information to anisotropies

abstract:
  The origin of CMB polarization is reviewed. Special emphasis is placed on the
cosmological information encoded in it: the nature of primordial fluctuations,
the connection with the inflation paradigm. Insights into more recent epochs
are also discussed: early reionization and high redshift matter distribution
from CMB lensing.


title:
A Method for energy estimation and mass composition determination of
  primary cosmic rays at Chacaltaya observation level based on atmospheric
  Cerenkov light technique

abstract:
  A new method for energy and mass composition estimation of primary cosmic ray
radiation based on atmospheric Cerenkov light flux in extensive air showers
(EAS) analysis is proposed. The Cerenkov light flux in EAS initiated by primary
protons and iron nuclei is simulated with CORSIKA 5.62 code for Chacaltaya
observation level (536 g/cm2) in the energy range 10 TeV - 10 PeV. An adequate
model, approximation of lateral distribution of Cerenkov light in showers is
obtained. Using the proposed model and solution of overdetermined system of
nonlinear equations based on Gauss Newton method with autoregularization, two
different array detector arrangements are compared. The detector response for
the detector sets is simulated. The accuracies in energy and shower axis
determination are studied and the corresponding selection criteria are
proposed. An approximation with nonlinear fit is obtained and the energy
dependence of the proposed model function parameters is studied. The
approximation of model parameters as function of the primary energy is carried
out. This permits, taking into account the properties of the proposed method
and model, to distinguish proton primaries from iron primaries. The detector
response for the detector sets is simulated and the accuracies in energy
determination are calculated. Moreover the accuracies in shower axis
determination are studied and criteria in shower axis position estimation are
proposed.


title: Molecular Gas in NUclei of GAlaxies (NUGA): II. The Ringed LINER NGC7217

abstract:
  We present CO(1-0) and CO(2-1) maps of the LINER galaxy NGC7217, obtained
with the IRAM interferometer, at 2.4"x1.9" and 1.2"x0.8" resolution
respectively. The nuclear ring (at r=12"=0.8kpc) dominates the CO maps, and has
a remarkable sharp surface density gradient at its inner edge. The latter is
the site of the stellar/Halpha ring, while the CO emission ring extends farther
or is broader (500-600pc). This means that the star formation has been more
intense toward the inner edge of the CO ring, in a thin layer, just at the
location of the high gas density gradient. In the CO(2-1) map, a central
concentration inside 3" coincides with a spiral dust lane, clearly seen in the
HST V-I color image. N-body simulations including gas dissipation and star
formation are performed to better understand the nature of the nuclear ring
observed. In the best model, the gas content was higher in the recent past
(having been consumed via star formation), and the oval/spiral formed were more
self-gravitating (abridged).


title:
Broad absorption line quasars have the same cool dust emission as
  quasars without BALs

abstract:
  The results of a sub-millimeter survey of SDSS broad CIV absorption line
quasars is discussed. It is found that the sub-millimeter flux distribution of
BAL quasars is similar to that of non-BAL quasars. This is consistent with the
idea that all quasars contain broad absorption line regions, but only a
fraction of them are visible along our line-of-sight. The observations are
inconsistent with BAL quasars being observed at a special evolutionary epoch
co-inciding with a high star-formation rate and dust mass.


title: Chemical Evolution in Omega Centauri

abstract:
  The globular cluster Omega Centauri displays evidence of a complex star
formation history and peculiar internal chemical evolution, setting it apart
from essentially all other globular clusters of the Milky Way. In this review
we discuss the nature of the chemical evolution that has occurred within Omega
Cen and attempt to construct a simple scenario to explain its chemistry.


title: New high-resolution radio observations of the SNR CTB 80

abstract:
  We report new high resolution and high sensitivity radio observations of the
extended supernova remnant (SNR) CTB 80 (G69.0+2.7) at 240 MHz, 324 MHz, 618
MHz, and 1380 MHz. The imaging of CTB 80 at 240 MHz and 618 MHz was performed
using the Giant Metrewave Radio Telescope (GMRT) in India. The observations at
324 MHz and 1380 MHz were obtained using the Very Large Array (VLA, NRAO) in
its C and D configurations. The new radio images reveal faint extensions for
the asymmetric arms of CTB 80. The arms are irregular with filaments and clumps
of size 1' (or 0.6 pc at a distance of 2 kpc). The radio image at 1380 MHz is
compared with IR and optical emission. The correspondence IR/radio is excellent
along the N arm of CTB 80. Ionized gas observed in the [SII] line perfectly
matches the W and N edges of CTB 80. The central nebula associated with the
pulsar PSR B1951+32 was investigated with an angular resolution of 10" x 6".
The new radio image obtained at 618 MHz shows with superb detail structures in
the 8' x 4' E-W ``plateau'' nebula that hosts the pulsar on its western
extreme. A twisted filament, about 6' in extent (~3.5 pc), trails behind the
pulsar in an approximate W-E direction. In the bright ``core'' nebula (size
\~45"), located to the W of the plateau, the images show a distortion in the
morphology towards the W; this feature corresponds to the direction in which
the pulsar escapes from the SNR with a velocity of ~240 km/s. Based on the new
observations, the energetics of the SNR and of the PWN are investigated.


title: Near-Infrared Colors of Submillimeter-Selected Galaxies

abstract:
  We report on deep near-infrared (NIR) observations of submillimeter-selected
galaxies (SMGs) with the Near Infrared Camera (NIRC) on the Keck I telescope.
We have identified K-band candidate counterparts for 12 out of 15 sources in
the SCUBA Cluster Lens Survey. Three SMGs remain non-detections with K-band
limits of K>23 mag, corrected for lensing. Compensating for lensing we find a
median magnitude of K=22+/-1 mag for the SMG population, but the range of NIR
flux densities spans more than a factor of 400. For SMGs with confirmed
counterparts based on accurate positions from radio, CO, and/or millimeter
continuum interferometric observations, the median NIR color is J-K=2.6+/-0.6
mag. The NIR-bright SMGs (K<19 mag) have colors of J-K =~ 2 mag, while the
faint SMGs tend to be extremely red in the NIR (J-K>3 mag). We argue that a
color selection criterion of J-K>~3 mag can be used to help identify
counterparts of SMGs that are undetected at optical and radio wavelengths. The
number density of sources with J-K>3 mag is 5 arcmin^{-2} at K<22.5 mag,
greater than that of SMGs with S(850um)>2 mJy. It is not clear if the excess
represents less luminous infrared-bright galaxies with S(850um)<~2 mJy, or if
the faint extremely red NIR galaxies represent a different population of
sources that could be spatially related to the SMGs.


title:
Calibration of the EDELWEISS Cryogenic Heat-and-ionisation Germanium
  Detectors for Dark Matter Search

abstract:
  Several aspects of the analysis of the data obtained with the cryogenic
heat-and-ionisation Ge detectors used by the EDELWEISS dark matter search
experiment are presented. Their calibration, the determination of their energy
threshold, fiducial volume and nuclear recoil acceptance are detailed.


title:
The Pisgah Automated Survey: A Photometric Search for Low-mass Detached
  Eclipsing Binaries and Other Variable Stars

abstract:
  The Pisgah Survey, located at the facilities of the Pisgah Astronomical
Research Institute in Rosman NC, is a low cost project to acquire
fully-automated I band photometry of selected areas of the sky. The survey
collects multiple images of about 16.5 sq. deg. of sky per night, searching for
variability in stars with apparent magnitudes brighter than I = 15. The main
scientific goal of this project is to discover new low-mass detached eclipsing
binaries to provide precise constraints to the mass-radius relation for the
lower main sequence.
  In this paper we present a technical description of the project, including
the software routines to automate the collection and analysis of the data, and
a description of our variable identification strategy. We prove the feasibility
of our technique by showing the successful detection of the previously known
M-dwarf detached eclipsing binary GJ 2069A, and we present the results of the
analysis of the first set of fields imaged by the survey, in which 15 new
variables have been discovered among 8,201 stars monitored. The paper concludes
with an outline of the project's prospects.


title:
X-rays from the Dawn of the Modern Universe. Chandra and XMM-Newton
  Observations of z>4 Quasars

abstract:
  Quasars at z>4 provide direct information on the first massive structures to
form in the Universe. Recent ground-based optical surveys (e.g., the Sloan
Digital Sky Survey) have discovered large numbers of high-redshift quasars,
increasing the number of known quasars at z>4 to ~500. Most of these quasars
are suitable for follow-up X-ray studies. Here we review X-ray studies of the
highest redshift quasars, focusing on recent advances enabled largely by the
capabilities of Chandra and XMM-Newton. Overall, analyses indicate that the
X-ray emission and broad-band properties of high-redshift and local quasars are
reasonably similar, once luminosity effects are taken into account. Thus,
despite the strong changes in large-scale environment and quasar number density
that have occurred from z~0-6, individual quasar X-ray emission regions appear
to evolve relatively little.


title: The origin and tidal evolution of cuspy triaxial haloes

abstract:
  We present a technique for constructing equilibrium triaxial N-body haloes
with nearly arbitrary density profiles, axial ratios and spin parameters. The
method is based on the way in which structures form in hierarchical
cosmological simulations, where prolate and oblate haloes form via mergers with
low and high angular momentum, respectively. We show that major mergers between
equilibrium spherical cuspy haloes produce similarly cuspy triaxial remnants
and higher angular-momentum mergers produce systems with lower concentrations.
Triaxial haloes orbiting within deeper potentials become more spherical and
their velocity dispersion tensors more isotropic. The rate of mass loss depends
sensitively on the halo shape: a prolate halo can lose mass at a rate several
times higher than an isotropic spherical halo with the same density profile.
Subhaloes within cosmological simulations are significantly rounder than field
haloes with axial ratios that are ~ 30% larger.


title: The K-band Hubble diagram of sub-mm galaxies and hyperluminous galaxies

abstract:
  We present the K-band Hubble diagrams (K-z relations) of sub-mm-selected
galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a
remarkably tight K-z relation of HLIRGs, indistinguishable from that of the
most luminous radiogalaxies. Like radiogalaxies, the HLIRG K-z relation at z<~3
is consistent with a passively evolving ~3L* instantaneous starburst starting
from a redshift of z~10. In contrast, many sub-mm selected galaxies are >~2
magnitudes fainter, and the population has a much larger dispersion. We argue
that dust obscuration and/or a larger mass range may be responsible for this
scatter. The galaxies so far proved to be hyperluminous may have been biased
towards higher AGN bolometric contributions than sub-mm-selected galaxies due
to the 60 micron selection of some, so the location on the K-z relation may be
related to the presence of the most massive AGN. Alternatively, a particular
host galaxy mass range may be responsible for both extreme star formation and
the most massive active nuclei.


title:
Supernova Simulations with Boltzmann Neutrino Transport: A Comparison of
  Methods

abstract:
  Accurate neutrino transport has been built into spherically symmetric
simulations of stellar core collapse and postbounce evolution. The results of
such simulations agree that spherically symmetric models with standard
microphysical input fail to explode by the delayed, neutrino-driven mechanism.
Independent groups implemented fundamentally different numerical methods to
tackle the Boltzmann neutrino transport equation. Here we present a direct and
detailed comparison of such neutrino radiation-hydrodynamical simulations for
two codes, Agile-Boltztran of the Oak Ridge-Basel group and Vertex of the
Garching group. The former solves the Boltzmann equation directly by an
implicit, general relativistic discrete angle method on the adaptive grid of a
conservative implicit hydrodynamics code with second-order TVD advection. In
contrast, the latter couples a variable Eddington factor technique with an
explicit, moving-grid, conservative high-order Riemann solver with important
relativistic effects treated by an effective gravitational potential. The
presented study is meant to test both neutrino radiation-hydrodynamics
implementations and to provide a data basis for comparisons and verifications
of supernova codes to be developed in the future. Results are discussed for
simulations of the core collapse and post-bounce evolution of a 13 solar mass
star with Newtonian gravity and a 15 solar mass star with relativistic gravity.


title: Breaking All the Rules: The Compact Symmetric Object 0402+379

abstract:
  We present results of multi-frequency VLBA observations of the compact
symmetric object (CSO) 0402+379. The parsec-scale morphology of 0402+379 allows
us to confirm it as a CSO, while VLA data clearly show the presence of
kiloparsec-scale structure. Thus, 0402+379 is only the second known CSO to
possess large scale structure. Another puzzling morphological characteristic
found from our observations is the presence of two central, compact,
flat-spectrum components, which we identify as possible active nuclei. We also
present the discovery of neutral hydrogen absorption along the southern hotspot
of 0402+379 with a central velocity ~1000 km/s greater than the systemic
velocity. Multi-epoch observations from the VLA archive, the Caltech-Jodrell
Bank Survey, and the VLBA Calibrator Survey allow us to further analyze these
anomalous features. Results of this analysis reveal significant motion in the
northern hotspot, as well as appreciable variability in both of the core
candidates. We consider the possibility that 0402+379 was formed during a
recent merger. In this case, the two candidate cores could be interpreted as
binary supermassive black holes that have not yet coalesced, whereas the
large-scale radio emission could be attributed to interactions directly linked
to the merger or to previous activity associated with one of the cores.


title:
Metallicity of the intergalactic medium using pixel statistics: III.
  Silicon

abstract:
  (Modified) We study the abundance of silicon in the intergalactic medium by
analyzing the statistics of SiIV, CIV, and HI pixel optical depths in a sample
of 19 high-quality quasar absorption spectra spanning redshifts z ~ 2 - 4,
which we compare to realistic spectra drawn from a hydrodynamical simulation.
We find that silicon is highly overabundant relative to carbon and that the
scatter in Si/C is much smaller than that in C/H, implying a common origin for
Si and C. The inferred [Si/C] depends upon the shape of the UV background (UVB)
(harder backgrounds leading to higher [Si/C]), ranging from [Si/C] ~ 1.5 for a
quasar-only UVB, to [Si/C] ~ 0.25 for a UVB including both galaxies and an
artificial softening. For our fiducial UVB, which includes both quasars and
galaxies, we find [Si/C]=0.77 +/- 0.05, with a possible systematic error of ~
0.1 dex. There is no evidence for evolution in [Si/C] and the data are
inconsistent with previous claims of a sharp change in the SiIV/CIV ratio (or
the UVB) at z ~ 3. Comparisons with low-metallicity halo stars and
nucleosynthetic yields suggest that either our fiducial UVB is too hard or that
supermassive Pop III stars might have to be included. The inferred [Si/C]
corresponds to a contribution to the cosmic Si abundance of [Si/H] = -2.0, a
significant fraction of all Si production expected by z ~ 3.


title: Discovery of a New Transient Magnetar Candidate: XTE J1810-197

abstract:
  We report the discovery of a new X-ray pulsar, XTE J1810-197. The source was
serendipitously discovered on 2003 July 15 by the Rossi X-ray Timing Explorer
(RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a
5.54 s spin-period and a soft spectrum (photon index ~ 4). We detect the source
in earlier RXTE observations back to 2003 January. These show that a transient
outburst began between 2002 November 17 and 2003 January 23 and that the pulsar
has been spinning down since then, with a high rate Pdot ~ 10^-11 s/s showing
significant timing noise, but no evidence for Doppler shifts due to a binary
companion. The rapid spin-down rate and slow spin-period imply a super-critical
magnetic field B=3x10^14 G and a young characteristic age < 7600 yr. These
properties are strikingly similar to those of anomalous X-ray pulsars and soft
gamma repeaters, making the source a likely new magnetar. A follow-up Chandra
observation provided a 2".5 radius error circle within which the 1.5 m
Russian-Turkish Optical Telescope RTT150 found a limiting magnitude of
R_c=21.5, in accord with other recently reported limits. The source is present
in archival ASCA and ROSAT data as well, at a level 100 times fainter than the
\~ 3 mCrab seen in 2003. This suggests that other X-ray sources that are
currently in a state similar to the inactive phase of XTE J1810-197 may also be
unidentified magnetars awaiting detection via a similar activity.


title: The dark matter density problem in massive disk galaxies

abstract:
  I discuss measurements of disk mass from non-circular streaming motions of
gas in the barred galaxies NGC 3095 and NGC 4123. In these galaxies with strong
shocks and non-circular motions, the inner regions must be disk-dominated to
reproduce the shocks. This requires dark matter halos of low central density
and low concentration, compared to LCDM halo predictions. In addition, the
baryonic collapse to a disk should have compressed the halo and increased the
dark matter density, which sharpens the disagreement. One possible resolution
is a substantial amount of angular momentum transfer from disk to halo, but
this is not particularly attractive nor elegant.


title: High-Energy Cosmic Rays from Gamma-Ray Bursts

abstract:
  A model is proposed for the origin of cosmic rays (CRs) from ~10^14 eV to the
highest energies, >10^20 eV. Gamma-Ray Bursts (GRBs) are assumed to inject CR
protons and ions into the interstellar medium of star-forming
galaxies--including the Milky Way--with a power law spectrum extending to a
maximum energy ~10^20 eV. The CR spectrum near the knee is fit with CRs trapped
in the Galactic halo that were accelerated and injected by an earlier Galactic
GRB. These CRs diffuse in the disk and halo of the Galaxy due to gyroresonant
pitch-angle scattering with MHD turbulence in the Galaxy's magnetic field. The
preliminary (2001) KASCADE data through the knee of the CR spectrum are fit by
a model with energy-dependent propagation of CR ions from a single Galactic
GRB. Ultra-high energy CRs (UHECRs), with energies above the ankle are assumed
to propagate rectilinearly with their spectrum modified by photo-pion,
photo-pair, and expansion losses. We fit the measured UHECR spectrum assuming
comoving luminosity densities of GRB sources consitent with possible star
formation rate histories of the universe. For power-law CR proton injection p>2
this model implies that the nonthermal content in the GRB blast waves is
hadronically dominated by a factor ~60-200. Calculations show that 100 TeV-100
PeV neutrinos could be detected several times per year from all GRBs in
kilometer-scale neutrino detectors such as IceCube, for GRB blast-wave Doppler
factors <~200. GLAST measurements of gamma-ray components and cutoffs will
constrain the product of nonthermal baryon loading and radiative efficiency,
limit the Doppler factor, and test this senario.


title: The Diverse Nature of Intrinsic Absorbers in AGNs

abstract:
  Intrinsic absorbers are significant components of AGN environments that
provide valuable information and interesting challenges. We present a very
brief (and biased, and sometimes speculative) overview of intrinsic absorbers
from the perspective of different absorption line classes. We also discuss ways
of addressing and learning from the "problem" of partial coverage of the
background light source, with some examples based on new high-resolution
rest-frame UV spectra of quasars.


title: Accretion and Outflow in the AGN and Starburst of NGC 5135

abstract:
  Observations of the Seyfert 2 and starburst galaxy NGC 5135 with the Chandra
X-ray Observatory demonstrate that both of these phenomena contribute
significantly to its X-ray emission. We spatially isolate the active galactic
nucleus (AGN) and demonstrate that it is entirely obscured by column density
N_H > 10^{24} cm^{-2}, detectable in the Chandra bandpass only as a strongly
reprocessed, weak continuum and a prominent iron K alpha emission line with
equivalent width of 2.4 keV. Most of the soft X-ray emission, both near the AGN
and extending over several-kpc spatial scales, is collisionally-excited plasma.
We attribute this thermal emission to stellar processes. The AGN dominates the
X-ray emission only at energies above 4 keV. In the spectral energy
distribution that extends to far-infrared wavelengths, nearly all of the
emergent luminosity below 10 keV is attributable to star formation, not the
AGN.


title:
Further multiwavelength observations of the SSA22 Ly_alpha emitting
  `blob'

abstract:
  We present new follow-up observations of the sub-mm luminous
Ly_alpha-emitting object in the SSA22 z=3.09 galaxy overdensity, referred to as
`Blob 1' by Steidel et al.(2000). In particular we discuss high resolution
Hubble Space Telescope optical imaging, Owens Valley Radio Observatory spectral
imaging, Keck spectroscopy, VLA 20cm radio continuum imaging, and Chandra X-ray
observations. We also present a more complete analysis of the existing James
Clerk Maxwell Telescope sub-mm data. We detect several optical continuum
components which may be associated with the core of the submillimeter emitting
region. A radio source at the position of one of the HST components
(22:17:25.94, +00:12:38.9) identifies it as the likely counterpart to the
submillimeter source. We also tentatively detect the CO(4-3) molecular line,
centered on the radio position. We use the CO(4-3) intensity to estimate a
limit on the gas mass for the system. The optical morphology of sources within
the Ly_alpha cloud appears to be filamentary, while the optical source
identified with the radio source has a dense knot which may be an AGN or
compact starburst. We obtain a Keck-LRIS spectrum of this object, despite its
faintness (R=26.8). The spectrum reveals weak Ly_alpha emission, but no other
obvious features, suggesting that the source is not an energetic AGN (or that
it is extremely obscured). We use non-detections in deep Chandra X-ray images
to constrain the nature of the `Blob'. Although conclusive evidence regarding
the nature of the object remains hard to obtain at this redshift, the evidence
presented here is at least consistent with a dust-obscured AGN surrounded by a
starburst situated at the heart of this giant Ly_alpha cloud.


title:
Does merger-induced core-collapse produce gamma-ray bursts in type Ib &
  Ic supernovae?

abstract:
  Gamma-ray bursts, discovered over three decades ago, can appear to be a
hundred times as luminous as the brightest supernovae. However, there has been
evidence for some time now of an association of gamma-ray bursts with
supernovae of type Ib and Ic. Here we interpret the overabundance of
millisecond pulsars in globular clusters and the details of supernova 1987A to
reveal the energy source, which powers at least some long-duration gamma-ray
bursts, as core-collapse following the merger of two white dwarfs, either as
stars or stellar cores. In order for the beams/jets associated with gamma-ray
bursts to form in mergers within massive common envelopes (as with SN1987A),
much of the intervening stellar material in the polar directions must be
cleared out by the time of core-collapse, or the beams/jets themselves must
clear their own path. The core-collapse produces supernovae of type Ib, Ic, or
II (as with SN1987A, a SNa IIp), leaving a weakly magnetized neutron star
remnant with a spin period near 2 milliseconds. There is no compelling reason
to invoke any other model for gamma-ray bursts.


title: Atomic and Molecular Absorption at High Redshift

abstract:
  Strong constraints on possible variations in fundamental constants can be
derived from HI 21-cm and molecular rotational absorption lines observed
towards quasars. With the aim of forming a statistical sample of constraints we
have begun a program of systematic searches for such absorption systems. Here
we describe molecular rotational searches in 25 damped Lyman-alpha systems
where, in many cases, we set optical depth limits an order of magnitude better
than that required to detect the 4 known redshifted millimeter-wave absorbers.
We also discuss the contributory factors in the detectability of HI 21-cm
absorption, focusing on possible biases (e.g.low covering factors) in the
currently known sample of absorbers and non-detections.


title: A Review of the Distance and Structure of the Large Magellanic Cloud

abstract:
  The average of 14 recent measurements of the distance to the Large Magellanic
Cloud (LMC) implies a true modulus of 18.50 +- 0.02 mag, and demonstrates a
trend in the past 2 years of convergence toward a standard value. The distance
indicators reviewed are the red clump, the tip of the red giant branch,
Cepheid, RR Lyrae, and Mira variable stars, cluster main-sequence fitting,
supernova 1987A, and eclipsing binaries. The eclipsing binaries yield a
consistent distance on average; however, the internal scatter is twice as large
as the average measurement error. I discuss parameters of LMC structure that
pertain to distance indicators, and speculate that warps discovered using the
color of the clump are not really warps.


title: Discovery of Intergalactic HII Regions

abstract:
  We have discovered a number of very small isolated HII regions 20-30 kpc from
their nearest galaxy. The HII regions appear as tiny emission line dots
(ELdots) in narrow band images obtained by the NOAO Survey for Ionization in
Neutral Gas Galaxies (SINGG). We have spectroscopic confirmation of 5 isolated
HII regions in 3 systems. The H-alpha luminosities of the HII regions are
equivalent to the ionizing flux of only 1 large or a few small OB stars each.
These stars appear to have formed in situ and represent atypical star formation
in the low density environment of galaxy outskirts. In situ star formation in
the intergalactic medium offers an alternative to galactic wind models to
explain metal enrichment. In interacting systems (2 out of 3), isolated HII
regions could be a starting point for tidal dwarf galaxies.


title: Mapping the Remote Milky Way Halo using BHB stars at 70 < r < 130 kpc

abstract:
  We increase the number of remote halo tracers by using blue horizontal branch
(BHB) stars out to Galactocentric distances of 130 kpc. We use SDSS EDR
photometry and the VLT to detect 16 BHB stars at Galactocentric distances 70 <
r < 130, and to measure their radial velocities. We find the mass of the Milky
Way is M =1.7^{+3.0}_{-0.6} x 10^{12} solar masses. When completed this survey
will: (i) substantially reduce the errors in the total mass and extent of the
Milky Way halo, (ii) map the velocity space in a hitherto unexplored region of
the halo.


title: Secondary Globular Cluster Populations

abstract:
  Globular Cluster (GC) systems of most early-type galaxies show bimodal
optical color distributions, yet their Luminosity Functions (LFs) look like
simple Gaussians with turn-over magnitudes used for determination of distances
and the Hubble constant. Taking color distributions and LFs of Milky Way halo
GCs as a reference for the apparently universal old metal-poor GC populations
and assuming their intrinsic widths to be constant in time at the values of the
Milky Way halo GC populations, I study for which combinations of age and
metallicity a secondary GC population formed in some violent star formation
event in the history of a galaxy may or may not be detected in the observed GC
color distributions and LFs (U- through K-bands). Significant differences are
found among the diagnostic efficiencies in various wavelength regions with the
NIR predicted to be able to reveal the presence of GC subpopulations that may
perfectly hide within one inconspicuous optical color peak. If, and only if,
some broad age -- metallicity relation is assumed, as expected e.g. for
secondary GCs forming in spiral galaxy mergers from a pre-enriched ISM, models
indicate single-peak GC LFs even in GC systems with bimodal color
distributions. We point out the importance of having multi-band information
(including NIR) to independently constrain ages and metallicities of GC
subpopulations that will shed light on both cluster and galaxy formation
scenarios. Models presented here are being used for the interpretation of
multi-wavelength data from our ASTROVIRTEL project on GC systems in galaxies of
various types, luminosities and environments as well as on young star cluster
systems in interacting galaxies and mergers.


title:
E3D, The Euro3D Visualization Tool I: Description of the program and its
  capabilities

abstract:
  We present the first version of E3D, the Euro3D visualization tool for data
from integral field spectroscopy. We describe its major characteristics, based
on the proposed requirements, the current state of the project, and some
planned future upgrades. We show examples of its use and capabilities.


title:
E3D, the Euro3D Visualization Tool II: mosaics, VIMOS data and large
  IFUs of the future

abstract:
  In this paper, we describe the capabilities of E3D, the Euro3D visualization
tool, to handle and display data created by large Integral Field Units (IFUs)
and by mosaics consisting of multiple pointings. The reliability of the
software has been tested with real data, originating from the PMAS instrument
in mosaic mode and from the VIMOS instrument, which features the largest IFU
currently available. The capabilities and limitations of the current software
are examined in view of future large IFUs, which will produce extremely large
datasets.


title:
Substellar companions and isolated planetary mass objects from
  protostellar disc fragmentation

abstract:
  Self-gravitating protostellar discs are unstable to fragmentation if the gas
can cool on a time scale that is short compared to the orbital period. We use a
combination of hydrodynamic simulations and N-body orbit integrations to study
the long term evolution of a fragmenting disc with an initial mass ratio to the
star of M_disc/M_star = 0.1. For a disc which is initially unstable across a
range of radii, a combination of collapse and subsequent accretion yields
substellar objects with a spectrum of masses extending (for a Solar mass star)
up to ~0.01 M_sun. Subsequent gravitational evolution ejects most of the lower
mass objects within a few million years, leaving a small number of very massive
planets or brown dwarfs in eccentric orbits at moderately small radii. Based on
these results, systems such as HD 168443 -- in which the companions are close
to or beyond the deuterium burning limit -- appear to be the best candidates to
have formed via gravitational instability. If massive substellar companions
originate from disc fragmentation, while lower-mass planetary companions
originate from core accretion, the metallicity distribution of stars which host
massive substellar companions at radii of ~1 au should differ from that of
stars with lower mass planetary companions.


title: On the optical extinction and distance of GRS 1915+105

abstract:
  Based on new millimeter and radio observations, we reevaluate the total
hydrogen column density along the line of sight to the microquasar GRS 1915+105
to NH=(3.5 +/- 0.3) 10^22 cm^-2. Our value is consistent with the one derived
from X-ray measurements, namely (3.8 +/- 0.3) 10^22 cm^-2 (Ebisawa et al.
1998). Using the empirical law between the visual extinction and the total
column density of hydrogen, Av is found to 19.6 +/- 1.7 mag. This result is 7
mag lower than previously thought, and therefore, a reevaluation of infrared
fluxes after derredening is needed. The revisited kinematic study allows to
give a lower limit to the distance of GRS 1915+105, namely 6.0 kpc. Taking into
account the most accurate upper limit of distance inferred from radio data
(11.2 +/- 0.8 kpc; Fender et al. 1999) as well as this lower limit, this
implies a distance of 9.0 +/- 3.0 kpc .


title: The Nuclear Gas Dynamics and Star Formation of NGC 7469

abstract:
  We report interferometric radio CO2-1 observations at a resolution of 0.7",
and 0.085" resolution adaptive optics K-band spectroscopy of the inner few
arcseconds of NGC7469. The CO2-1 map shows a ring of molecular clouds and a
bright extended nucleus, with a bar or pair of spiral arms between them. The
dynamical structure of both the radio CO2-1 and the K-band H2 1-0S(1) lines can
be reproduced using an axisymmetric mass model comprising 3 components: a broad
disk, a ring 4-5" across, and an inner nuclear ring about 0.5" across. No
non-circular motions faster than the velocity residuals of 25 km/s are seen,
although this may be because in some cases a secondary bar is not expected to
cause gas inflow. From the dynamical mass and estimates of the stellar mass we
find that the CO-to-H_2 conversion is 0.4-0.8 times that for the Milky Way. The
H2 1-0S(1) morphology peaks at the nucleus, although there is no strong nuclear
mass concentration. The 1-0S(1) is likely to originate in X-ray of gas by the
AGN rather than via star formation. Using the 2.3um stellar CO2-0 absorption
and the continuum slope we have directly resolved the nuclear star cluster to
be 0.15-0.20" across, and find that it is asymmetric. This cluster has an age
of less than about 60Myr and contributes 20-30% of the nuclear K-band light,
and about 10% of the nuclear bolometric luminosity. Within a radius of ~4" gas
contributes more than half the total mass; but in the nucleus, within a radius
of 0.1", it is likely that most of the mass is due to stars


title: Search for brown-dwarf like secondaries in cataclysmic variables II

abstract:
  We have examined VTL/ISAAC 1-2.5 $\umu$m spectroscopy of a sample of short
orbital period cataclysmic variables which are candidates for harboring
substellar companions. We provide descriptions of the infrared spectrum of
\hbox{EI Psc}, \hbox{V834 Cen}, \hbox{WX Cet}, \hbox{VW Hyi}, \hbox{TY PsA} and
\hbox{BW Scl}. Fitting of the IR spectral energy distribution (SED) was
performed by comparing the observed spectrum with late-type templates.
Absorption features of the secondary star were detected in \hbox{EI Psc} and
\hbox{V834 Cen}, consistent with dwarf secondaries of spectral type K 5 $\pm$ 1
and M 8 $\pm$ 0.5, respectively. In addition, we report the first detection of
the secondary star in \hbox{VW Hyi}. The SED in this case is well matched by an
L 0 $\pm$ 2 type secondary contributing 23 per cent to the overall flux at
$\lambda$ = 1.15 $\umu$m. This is a surprising result for a system with a
relatively high mass transfer rate. We discuss the implication of our findings
on the current scenarios for cataclysmic variable star evolution.


title: XMM-Newton observation of SNR RX J1713.7-3946

abstract:
  We present the first results of the observations of the supernova remnant RX
J1713.7-3946 (also G347.3-0.5) obtained with the EPIC instrument on board the
XMM-Newton satellite. We show a 5 pointings mosaiced image of the X-ray
synchrotron emission. We characterize this emission by mapping its spectral
parameters (absorbing column density NH and photon index). The synchrotron
spectrum is flat at the shock and steep in the interior of the remnant. NH is
well correlated with the X-ray brightness. A strong NH is found in the
southwest rim of RX J1713.7-3946. We suggest that the SNR is interacting with a
HI region there.


title:
A movie of a star: multi-epoch VLBA imaging of the SiO masers towards
  the Mira variable TX Cam

abstract:
  We describe an observing campaign using the Very Long Baseline Array (VLBA)
to monitor the time-evolution of the v=1, J=1-0 SiO maser emission towards the
Mira variable TX Cam. The data reported here cover the period 1997 May 24 to
1999 February 19, during which the SiO maser emission was imaged at
approximately bi-weekly intervals. The result is an animated movie at an
angular resolution of ~500 microarcsec, over a full pulsation period, of the
gas motions in the near circumstellar environment of this star, as traced by
the SiO maser emission. This paper serves to release the movie and is the first
in a series concerning the scientific results from this observing campaign. In
this paper, we discuss the global proper motion of the SiO maser emission as a
function of pulsation phase. We measure a dominant expansion mode between
optical phases $\phi \sim 0.7-1.5$ confirming ballistic deceleration, and
compare this to predictions from existing pulsation models for late-type,
evolved stars. Local infall and outflow motions are superimposed on the
dominant expansion mode, and non-radial local gas motions are also evident for
individual SiO maser components. The overall morphology and evolution of the
SiO emission deviates significantly from spherical symmetry, with important
implications for models of pulsation kinematics in the near-circumstellar
environments of Mira variables.


title: Type Ia Supernovae: Spectroscopic Surprises

abstract:
  Recent observations have extended the range of diversity among spectra of
Type Ia supernovae. I briefly discuss SN Ia explosion models in the
spectroscopic context, the observed diversity, and some recent results from
direct analysis with the Synow code for one normal and two peculiar SNe Ia.
Relating the observational manifestations of diversity to their physical causes
is looking like an ever more challenging problem.


title: Time-delay quasars: scales and orders of magnitudes

abstract:
  We can think of a lensed quasar as taking the Hubble time, shrinking it by
\~10^{-11}, and then presenting the result to us as a time delay; the shrinking
factor is of the order of fractional sky-area that the lens occupies. This cute
fact is a straightforward consequence of lensing theory, and enables a simple
rescaling of time delays. Observed time delays have a 40-fold range, but after
rescaling the range reduces to 5-fold. The latter range depends on details of
the lens and lensing configuration--for example, quads have systematically
shorter rescaled time delays than doubles--and is as expected from a simple
model. The hypothesis that observed time-delay lenses all come from a
generalized-isothermal family can be ruled out. But there is no indication of
drastically different populations either.


title: XMM-Newton observation of Kepler's supernova remnant

abstract:
  We present the first results coming from the observation of Kepler's
supernova remnant obtained with the EPIC instruments on board the XMM-Newton
satellite. We focus on the images and radial profiles of the emission lines (Si
K, Fe L, Fe K) and of the high energy continuum. Chiefly, the Fe L and Si K
emission-line images are generally consistent with each other and the radial
profiles show that the Si K emission extends to a larger radius than the Fe L
emission (distinctly in the southern part of the remnant). Therefore, in
contrast to Cas A, no inversion of the Si- and Fe-rich ejecta layers is
observed in Kepler. Moreover, the Fe K emission peaks at a smaller radius than
the Fe L emission, which implies that the temperature increases inwards in the
ejecta. The 4-6 keV high energy continuum map shows the same distribution as
the asymmetric emission-line images except in the southeast where there is a
strong additional emission. A two color image of the 4-6 keV and 8-10 keV high
energy continuum illustrates that the hardness variations of the continuum are
weak all along the remnant except in a few knots. The asymmetry in the Fe K
emission-line is not associated with any asymmetry in the Fe K equivalent width
map. The Si K maps lead to the same conclusions. Hence, abundance variations do
not cause the north-south brightness asymmetry. The strong emission in the
north may be due to overdensities in the circumstellar medium. In the
southeastern region of the remnant, the lines have a very low equivalent width
and the X-ray emission is largely nonthermal.


title: The Far Ultraviolet Spectrum of the Io Plasma Torus

abstract:
  The spectrum of the Io plasma torus in the range 905 - 1187 A was recorded at
0.26 A resolution by the Far Ultraviolet Spectroscopic Explorer (FUSE) on 2001
January 14. Five orbits of data were obtained with the west ansa of the torus
centered and tracked in the 30" x 30" apertures of the FUSE spectrographs for a
total observation time of 9740 seconds. This region of the spectrum is
dominated by transitions of S II, S III and S IV, whose multiplet structure is
nearly completely resolved. We confirm our earlier detection of emission from
resonance multiplets of Cl III and Cl II and derive an abundance of Cl^{+2} of
2.1% relative to S^{2+}, leading to an overall chlorine ion abundance in the
torus of slightly less than 1%. A number of features near 990 A remain
unidentified, and C III at 977 A is detected in two independent channels at the
3-sigma level. The inferred relative ion abundance of C^{2+} relative to S^{2+}
is 3.7 x 10^{-4}. We also present spectra at 0.085 A resolution taken on 2001
October 19 and 21 with the 4" x 20" aperture. In these spectra the observed
lines are resolved and their widths correspond to ion temperatures of 60 - 70
eV for all three sulfur ions.


title: A Search for Sodium Absorption from Comets Around HD209458

abstract:
  We monitored the planet-bearing solar-type star HD209458 for sodium
absorption in the region of the stellar NaI D1 line that would be indicative of
cometary activity in the system. We observed the star using the HET HRS with
high S/N and high spectral resolution for 6 nights over the course of two
years, from July 2001 to July 2003. From modelling we determine a 20%
likelihood of a detection, based on a predicted number of comets similar to
that of the solar system. We find that our analytical method is able to recover
a signal and our S/N is sufficient to detect this feature in the spectral
regions on either side of the core of the D1 line, where it is most likely to
appear. No significant absorption was detected for any of the nights based on a
3 sigma detection limit. We derive upper limits on the column density of sodium
of < ~6 x 10^{9} cm^{-2} for a signal in the region around the line core and <
\~2 x 10^{10} cm^{-2} for a signal in the core of the photospheric D1 line.
These numbers are consistent with the sodium released in a single periodic
comet in our own system, though higher S/N may be necessary to uncover a signal
in the core of the D1 line. Implications for cometary activity in the HD209458
system are discussed.


title: Convection in the atmospheres and envelopes of Pre-Main Sequence stars

abstract:
  The Teff location of Pre-Main Sequence (PMS) evolutionary tracks depends on
the treatment of over-adiabaticity. Since the convection penetrates into the
stellar atmosphere, also the treatment of convection in the modeling of stellar
atmospheres will affect the location of the Hayashi tracks. We present new
non-grey PMS tracks for Teff>4000 K. We compute several grids of evolutionary
tracks varying: 1. the treatment of convection: either the Mixing Length Theory
(MLT) or Canuto et al. (1996, CGM) treatment; 2.the atmospheric boundary
conditions: we use the new Vienna grids of ATLAS9 atmospheres (Heiter et al.
2002a), which were computed using either MLT (with alpha=Lambda/Hp=0.5) or CGM
treatments. We compute as well grids of models with the NextGen (Allard &
Hauschildt 1997) atmosphere models, and a 1 Msun grey MLT evolutionary track
using the alpha calibration based on 2D-hydrodynamical models (Ludwig et al.
1999)}. These different grids of models allow us to analyze the effects of
convection modeling on the non--grey PMS evolutionary tracks. We conclude that:
1. In spite of the solar calibration, if MLT convection is adopted a large
uncertainty results in the shape and location of PMS tracks. 2. As long as the
model of convection is not the same in the interior and in the atmosphere the
optical depth at which we take the boundary conditions is an additional
parameter of the models. 3. The comparison between NextGen and ATLAS9 based
models shows that, in the Teff domain they have in common (4000--10000K), the
PMS location is mainly determined by the treatment of the over-adiabatic
convection. 4. Comparison with observations indicates that, for any convection
model and for any of the atmosphere grids, convection in the PMS phase appears
to be less efficient than what is necessary in order to fit the Sun.


title:
X-shaped radio galaxies as observational evidence for the interaction of
  supermassive binary black holes and accretion disk at pc scale

abstract:
  A supermassive black hole binary may form during galaxy mergering. we
investigate the interaction of the supermassive binary black holes (SMBBHs) and
an accretion disk and show that the detected X-shaped structure in some FRII
radio galaxies may be due to the interaction-realignment of inclined binary and
accretion disk occurred within the pc scale of the galaxy center. We compare in
detail the model and observations and show that the configuration is consistent
very well with the observations of X-shaped radio sources. X-shaped radio
feature form only in FRII radio sources due to the strong interaction between
the binary and a standard disk, while the absence of X-shaped FRI radio
galaxies is due to that the interaction between the binary and the radiatively
inefficient accretion flow in FRI radio sources is negligible. It is suggested
that the binary would keep misaligned with the outer disk for most of the life
time of FRII radio galaxies and the orientation of jet in most FRII radio
galaxies distributes randomly, while the jets in most FRI radio galaxies is
expected to be vertical to the accretion disk and thus the major axis of host
galaxy. We discuss the relationship of X-shaped and double-double radio
galaxies (DDRGs). The model is applied in paticular to two X-shaped radio
sources 4C+01.30 and 3C293 and one DDRG source J0116-473 and show that the
SMBBHs in the three objects have black hole mass ratios $q \sim 0.1 - 0.3$.


title: Evidence for the Black Hole Event Horizon

abstract:
  Astronomers have discovered many candidate black holes in X-ray binaries and
in the nuclei of galaxies. The candidate objects are too massive to be neutron
stars, and for this reason they are considered to be black holes. While the
evidence based on mass is certainly strong, there is no proof yet that any of
the objects possesses the defining characteristic of a black hole, namely an
event horizon. Type I X-ray bursts, which are the result of thermonuclear
explosions when gas accretes onto the surface of a compact star, may provide
important evidence in this regard. Type I bursts are commonly observed in
accreting neutron stars, which have surfaces, but have never been seen in
accreting black hole candidates. It is argued that the lack of bursts in black
hole candidates is compelling evidence that these objects do not have surfaces.
The objects must therefore possess event horizons.


title:
Numerical study of the cosmological velocity field as a function of
  density

abstract:
  We report on a new study of the velocity distribution in N-body simulations.
We investigate the center-of-mass and internal kinetic energies of coarsening
cells as a function of time, cell size and cell mass. By using self-similar
cosmological models, we are able to derive theoretical predictions for
comparison and to assess the influence of finite-size and resolution effects.
The most interesting result is the discovery of a polytropic-like relationship
between the average velocity dispersion (internal kinetic energy) and the mass
density in an intermediate range of densities, K ~ rho^{2-eta}. The exponent
eta measures the deviations from the virial prediction, eta_virial=0. For
self-similar models, eta depends only on the spectral index of the initial
power spectrum. We also study CDM models and confirm a previous result that the
same polytropic-like dependence exists (astro-ph/0103313), with a time and
coarsening length dependent eta. The dependence K(rho) is an important input
for a recently proposed theoretical model of cosmological structure formation
which improves over the standard dust model (pressureless fluid) by
regularizing the density singularities.


title: Imprints of neutron stars in the interstellar medium

abstract:
  We have carried out an HI survey towards X-ray central compact objects (CCOs)
inside supernova remnants (SNRs) which shows that many of them are placed
within local HI minima. The nature of these minima is not clear, but the most
likely explanation is that the CCOs have evacuated the neighboring gas. This
survey also allowed us to detect a weak, diffuse radio nebula inside the SNR
Vela Jr, probably created by the winds of its associated CCO.


title: Metallicity, planetary formation and migration

abstract:
  Recent observations show a clear correlation between the probability of
hosting a planet and the metallicity of the parent star. Since radial velocity
surveys are biased, however, towards detecting planets with short orbital
periods, the probability-metallicity correlation could merely reflect a
dependence of migration rates on metallicity. We investigated the possibility,
but find no basis to suggest that the migration process is sensitive to the
metallicity. The indication is, therefore, that a higher metallicity results in
a higher probability for planet formation.


title:
A High-Resolution Study of Nonthermal Radio and X-Ray Emission from SNR
  G347.3-0.5

abstract:
  G347.3-0.5 is one of three shell-type supernova remnants in the Galaxy whose
X-ray spectrum is dominated by nonthermal emission. This puts G347.3-0.5 in the
small, but growing class of SNRs for which the X-ray emission reveals directly
the presence of extremely energetic electrons accelerated by the SNR shock. We
have obtained new high-resolution X-ray and radio data on G347.3-0.5 using the
Chandra X-ray Observatory and the Australia Telescope Compact Array (ATCA)
respectively. The bright northwestern peak of the SNR seen in ROSAT and ASCA
images is resolved with Chandra into bright filaments and fainter diffuse
emission. These features show good correspondence with the radio morphological
structure, providing strong evidence that the same population of electrons is
responsible for the synchrotron emission in both bands in this part of the
remnant. Spectral index information from both observations is presented. We
found significant difference in photon index value between bright and faint
regions of the SNR shell. Spectral properties of these regions support the
notion that efficient particle acceleration is occurring in the bright SNR
filaments. We report the detection of linear radio polarization towards the
SNR, which is most ordered at the northwestern shell where particle
acceleration is presumably occurring. Using our new Chandra and ATCA data we
model the broad-band emission from G347.3-0.5 with the synchrotron and inverse
Compton mechanisms and discuss the conditions under which this is a plausible
scenario.


title: Scaling Relations for Turbulence in the Multiphase Interstellar Medium

abstract:
  We employ a generalization of the She & Leveque model to study velocity
scaling relations based on our simulations of thermal instability--induced
turbulence. Being a by-product of the interstellar phase transition, such
multiphase turbulence tends to be more intermittent than compressible
isothermal turbulence. Due to radiative cooling, which promotes nonlinear
instabilities in supersonic flows, the Hausdorff dimension of the most singular
dissipative structures, D, can be as high as 2.3, while in supersonic
isothermal turbulence D is limited by shock dissipation to D < 2. We also show
that single-phase velocity statistics carry only incomplete information on the
turbulent cascade in a multiphase medium. We briefly discuss the possible
implications of these results on the hierarchical structure of molecular clouds
and on star formation.


title: A Search for $^6$Li in Lithium-Poor Stars with Planets

abstract:
  Using high-resolution, high quality spectra we investigate the presence of
$^6$Li in two lithium-poor stars that host extrasolar planetary systems. We
present improved atomic and molecular line lists for the region in the vicinity
of the lithium line at 6707.8 \AA, and we produce an excellent fit to the solar
spectrum. From line profile fitting, we find results consistent with no $^6$Li
in either of the lithium-poor planet-bearing stars or in three comparison stars
with and without planets, and 1-$\sigma$ upper limits of 0.04 for the isotopic
ratios of the two lithium-poor stars give an upper limit of 0.3 Jupiter masses
of material with primordial abundances that could have been recently deposited
in their outer layers. Our results suggest that post-main sequence accretion of
planets or planetary material that is undepleted in lithium is uncommon.


title:
The Uncertainty in Newton's Constant and Precision Predictions of the
  Primordial Helium Abundance

abstract:
  The current uncertainty in Newton's constant, G_N, is of the order of 0.15%.
For values of the baryon to photon ratio consistent with both cosmic microwave
background observations and the primordial deuterium abundance, this
uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass
fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the
effect from the current uncertainty in the neutron lifetime, which is often
treated as the dominant uncertainty in calculations of Y_P. Recent measurements
of G_N seem to be converging within a smaller range; a reduction in the
estimated error on G_N by a factor of 10 would essentially eliminate it as a
source of uncertainty in the calculation of the primordial 4He abundance.


title: The Iron Project and the RmaX Project

abstract:
  Ongoing activities under an international collaboration of atomic physicists
and astrophysicists under the Iron Project and the RmaX Project, with
applications to X-ray astronomy, are briefly described.


title: Complex X-ray spectral behaviour of NGC 4051 in the low flux state

abstract:
  The Narrow Line Seyfert 1 galaxy NGC 4051 was observed in one of its
prolonged low-lux states by XMM-Newton in November 2002. Here we present the
results of an analysis of EPIC-pn data obtained during the observation. Within
the low state, the source shows complex spectral variability which cannot
easily be explained by any simple model. However, by making a `flux-flux' plot
which combines the low state data with data obtained during a normal flux
state, we demonstrate that the extremely hard spectrum observed above 2 keV
results from a continuation of the spectral variability seen in the normal
state, which is caused by spectral pivoting of the power-law continuum. The
pivoting power-law appears to be attached to a Comptonised thermal component of
variable flux (blackbody temperature kT~0.1 keV, consistent with the small
black hole mass in NGC 4051) which dominates the soft X-ray band in the low
state, and is probably the source of seed photons for Comptonisation.
Additional constant thermal and reflection components, together with absorption
by ionised gas, seem to be required to complete the picture and explain the
complex X-ray spectral variability seen in the low state of NGC 4051.


title:
GRAPE-6: The massively-parallel special-purpose computer for
  astrophysical particle simulation

abstract:
  In this paper, we describe the architecture and performance of the GRAPE-6
system, a massively-parallel special-purpose computer for astrophysical
$N$-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed
in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case
with GRAPE-4, the primary application of GRAPE-6 is simulation of collisional
systems, though it can be used for collisionless systems. The main differences
between GRAPE-4 and GRAPE-6 are (a) The processor chip of GRAPE-6 integrates 6
force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed
3 clock cycles to calculate one interaction), (b) the clock speed is increased
from 32 to 90 MHz, and (c) the total number of processor chips is increased
from 1728 to 2048. These improvements resulted in the peak speed of 64 Tflops.
We also discuss the design of the successor of GRAPE-6.


title: The Dark Matter Distribution in the Central Regions of Galaxy Clusters

abstract:
  Cosmological N-body simulations predict that dark matter halos should have a
universal shape characterized by a steep, cuspy inner profile. Here we report
on a spectroscopic study of six clusters each containing a dominant brightest
cluster galaxy (BCG) with nearby gravitational arcs. Three clusters have both
radial and tangential gravitational arcs, whereas the other three display only
tangential arcs. We analyze stellar velocity dispersion data for the BCGs in
conjunction with the arc redshifts and lens models to constrain the dark and
baryonic mass profiles jointly. For those clusters with radial gravitational
arcs we were able to measure precisely the inner slope of the dark matter halo
and compare it with that predicted from CDM simulations.


title: Variable Star Monitoring in Local Group Dwarf Irregular Galaxies

abstract:
  Dwarf galaxies in the local group provide a unique astrophysical laboratory.
Despite their proximity some of these systems still lack a reliable distance
determination as well as studies of their stellar content and star formation
history. We present first results of our survey of variable stars in a sample
of six local group dwarf irregular galaxies. Taking the Leo A dwarf galaxy as
an example we describe observational strategies and data reduction. We discuss
the lightcurves of two newly found \delta Cephei stars and place them into the
context of a previously derived P-L relation. Finally we discuss the LPV
content of Leo A.


title:
X-ray He-like ions diagnostics: New Computations for Photoionized
  Plasmas: I. preliminary considerations

abstract:
  Using the new version of the photoionization code Titan designed for
plane-parallel photoionized thick hot media, which is unprecedented from the
point of view of line transfer, we have undertaken a study of the influence of
different parameters on the He-like and H-like emission of a medium
photoionized by an X-ray source. We explain why in modelling the emitting
medium it is important to solve in a self-consistent way the thermal and
ionization equilibria and to take into account the interconnection between the
different ions. We give the equivalent widths of the sum of the He-like
triplets and the triplet intensity ratios $G$ and $R$, for the most important
He-like ions, for a range of density, column density, and ionization parameter,
in the case of constant density media. We show that the line intensities from a
given ion can be accounted for, either by small values of both the column
density and of the ionization parameter, or by large values of both quantities,
and it is necessary to take into account several ions to disentangle these
possibilities. We show also that a "pure recombination spectrum" almost never
exists in a photoionized medium: either it is thin, and resonance lines are
formed by radiative excitation, or it is thick, and free-bound absorption
destroys the resonance photons as they undergo resonant diffusion.