title: Are Giant Planets Forming Around HR 4796A?

abstract:
  We have obtained FUSE and HST STIS spectra of HR 4796A, a nearby 8 Myr old
main sequence star that possesses a dusty circumstellar disk whose inclination
has been constrained from high resolution near-infrared observations to be ~17
deg from edge-on. We searched for circumstellar absorption in the ground states
of C II at 1036.3 A, O I at 1039.2 A, Zn II at 2026.1 A, Lyman series H2, and
CO (A-X) and failed to detect any of these species. We place upper limits on
the column densities and infer upper limits on the gas masses assuming that the
gas is in hydrostatic equilibrium, is well-mixed, and has a temperature, Tgas ~
65 K. Our measurements suggest that this system possesses very little molecular
gas. Therefore, we infer an upper limit for the gas:dust ratio (<4.0) assuming
that the gas is atomic. We measure less gas in this system than is required to
form the envelope of Jupiter.


title: Density profiles of LCDM clusters

abstract:
  We analyze the mass accretion histories (MAHs) and density profiles of
cluster- size halos with virial masses of 0.6-2.5x10^14/h Msun in a flat LCDM
cosmology. In agreement with previous studies,we find that the concentration of
the density distribution is tightly correlated with the halo's MAH and its
formation redshift.During the period of fast mass growth the concentration
remains approximately constant and low c_v ~ 3-4,while during the slow
accretion stages it increases with decreasing redshift as c_v ~ (1+z)^-1.We
consider fits of three widely discussed analytic density profiles to the
simulated clusters focusing on the most relaxed inner regions.We find that
there is no unique best fit analytic profile for all the systems.If,however,a
cluster is best fit by a particular analytic profile at z=0,the same is usually
true at earlier epochs out to z ~ 1-2.The local logarithmic slope of the
density profiles at 3% of the virial radius ranges from -1.2 to -2.0,a
remarkable diversity for the relatively narrow mass range of our cluster
sample.For all the studied clusters the logarithmic slope becomes shallower
with decreasing radius without reaching an asymptotic value down to the
smallest resolved scale < ~1% of the virial radius.We do not find a clear
correlation of the inner slope with the formation redshift or the shape of the
halo's MAH.We do find, however,that during the period of rapid mass growth the
density profiles can be well described by a single power law rho(r) ~ r^-gamma
with gamma ~ 1.5-2.The relatively shallow power law slopes result in low
concentrations at these stages of evolution.This indicates that the inner power
law like density distribution of halos is built up during the periods of rapid
mass accretion and active merging,while outer steeper profile is formed when
the mass accretion is slow.


title:
Aberration and the Fundamental Speed of Gravity in the Jovian Deflection
  Experiment

abstract:
  We describe our explicit Lorentz-invariant solution of the Einstein and null
geodesic equations for the deflection experiment of 2002 September 8 when a
massive moving body, Jupiter, passed within 3.7' of a line-of-sight to a
distant quasar. We develop a general relativistic framework which shows that
our measurement of the retarded position of a moving light-ray deflecting body
(Jupiter) by making use of the gravitational time delay of quasar's radio wave
is equivalent to comparison of the relativistic laws of the Lorentz
transformation for gravity and light. Because, according to Einstein, the
Lorentz transformation of gravity field variables must depend on a fundamental
speed $c$, its measurement through the retarded position of Jupiter in the
gravitational time delay allows us to study the causal nature of gravity and to
set an upper limit on the speed of propagation of gravity in the near zone of
the solar system as contrasted to the speed of the radio waves. We discuss the
misconceptions which have inhibited the acceptance of this interpretation of
the experiment. We also comment on other interpretations of this experiment by
Asada, Will, Samuel, Pascual-Sanchez, and Carlip and show that their `speed of
light' interpretations confuse the Lorentz transformation for gravity with that
for light, and the fundamental speed of gravity with the physical speed of
light from the quasar.

categories: astro-ph gr-qc hep-ph hep-th physics.class-ph


title: Fragmentation and Structure Formation

abstract:
  I present an overview of the hierarchy of structures existing in the
interstellar medium (ISM) and the possible mechanisms that cause the
fragmentation of one level into the next, with the formation of stars as its
last step. Within this framework, I then give an overview of the contributions
to this session. Numerical work addresses, at the largest scales, the shaping
and formation of structures in the ISM through turbulence driven by stellar
energy injection, and the resulting star formation rate as a function of mean
density. At the scales of molecular clouds, results comparing observational and
numerical data on the density and velocity structure of turbulence-produced
cores, as well as their mass spectra, are summarized, together with existing
theories of core and star formation controlled by the turbulence.
Observationally, an attempt to discriminate between the standard and turbulent
models of star formation is presented, finding inconclusive results, but
suggesting that both turbulence and the magnetic field are dynamically
important in molecular clouds and their cores. Finally, various determinations
of the magnetic field strength and geometry are also presented.


title:
The Case for Case C Mass Transfer in the Galactic Evolution of Black
  Hole Binaries

abstract:
  Earlier works, which we review, have shown that if the Fe core in a
presupernova star is to be sufficiently massive to collapse into a black hole,
earlier in the evolution of the star the He core must be covered (clothed) by a
hydrogen envelope during He core burning and removed only following this, in,
e.g. common envelope evolution. This is classified as Case C mass transfer.
These previous arguments were based chiefly on stellar evolution, especially
depending on the way in which 12C burned.
  In this work we argue for Case C mass transfer on the basis of binary
evolution. The giant progenitor of the black hole will have a large radius 1000
Rsun at the end of its supergiant stage. Its lifetime at that point will be
short, about 1000 yrs, so it will not expand much further. Thus, the initial
giant radius for Case C mass transfer will be constrained to a narrow band
about 1000 Rsun. This has the consequence that the final separation a_f
following common envelope evolution will depend nearly linearly on the mass of
the companion m_d which becomes the donor after the He core of the giant has
collapsed into the black hole. The separation at which this collapse takes
place is essentially a_f, because of the rapid evolution of the giant. (In at
least two binaries the black hole donor separation has been substantially
increased because of mass loss in the black hole formation. These can be
reconstructed from the amount of mass deposited on the donor in this mass
loss.)
  We show that the reconstructed preexplosion separations of the black hole
binaries fit well the linear relationship.


title: Interaction of Nanoparticles with Radiation

abstract:
  Interstellar grains span a wide range of sizes from a few angstroms to a few
micrometers. The presence of nanometer-sized or smaller particles in the
interstellar medium is indicated directly by the interstellar far ultraviolet
(UV) extinction, the ubiquitous 3.3, 6.2, 7.7, 8.6, and 11.3$\mum$ polycyclic
aromatic hydrocarbon (PAH) emission features, the near and mid infrared
broadband emission seen in the IRAS 12 and 25$\mum$ bands and the COBE-DIRBE
3.5, 4.9, 12 and 25$\mum$ bands, the 10--100$\GHz$ Galactic foreground
microwave emission, and indirectly by the heating of interstellar gas. For
nanoparticles under interstellar conditions, UV/visible photon absorption is
the dominant excitation process. With a heat capacity smaller than or
comparable to the energy of an energetic stellar photon, nanoparticles are
subject to single-photon heating, followed by vibrational relaxation,
photoionization, and photodestruction. With excited electrons spatially
confined, semiconductor nanoparticles are expected to luminesce efficiently.
This review focuses on the photophysics of nanoparticles with emphasis on the
stochastic heating and the vibrational excitation of interstellar PAH
molecules, and the excitation of photoluminescence with special attention given
to silicon nanoparticles.


title:
Design and Performance of the Wide-Field X-Ray Monitor on Board the
  High-Energy Transient Explorer 2

abstract:
  The Wide-field X-ray Monitor (WXM) is one of the scientific instruments
carried on the High Energy Transient Explorer 2 (HETE-2) satellite launched on
2000 October 9. HETE-2 is an international mission consisting of a small
satellite dedicated to provide broad-band observations and accurate
localizations of gamma-ray bursts (GRBs). A unique feature of this mission is
its capability to determine and transmit GRB coordinates in almost real-time
through the burst alert network. The WXM consists of three elements: four
identical Xe-filled one-dimensional position-sensitive proportional counters,
two sets of one-dimensional coded apertures, and the main electronics. The WXM
counters are sensitive to X-rays between 2 keV and 25 keV within a
field-of-view of about 1.5 sr, with a total detector area of about 350 cm$^2$.
The in-flight triggering and localization capability can produce a real-time
GRB location of several to 30 arcmin accuracy, with a limiting sensitivity of
$10^{-7}$ erg cm$^{-2}$. In this report, the details of the mechanical
structure, electronics, on-board software, ground and in-flight calibration,
and in-flight performance of the WXM are discussed.


title:
On Titanium Carbide Nanoparticles as the Origin of the 21 Micron
  Emission Feature in Post-Asymptotic Giant Branch Stars

abstract:
  Titanium carbide (TiC) nanocrystals were recently proposed as the carrier of
the mysterious 21$\mum$ emission feature observed in post-asymptotic giant
branch stars, based on their close spectral match and the presolar nature of
meteoritic TiC nanograins (which reveals their stellar ejecta origin). But we
show in this {\it Letter} that the Kramers-Kronig dispersion relations, which
relate the wavelength-integrated extinction cross section to the total dust
mass, would impose a lower bound on the TiC mass. This Kramers-Kronig lower
limit exceeds the maximum available TiC mass by a factor of at least
$\simali$50, independent of the absolute value of the ultraviolet/visible
absorptivity of nano TiC. The TiC model is therefore readily ruled out by the
Kramers-Kronig physical principle.


title: Modeling the Infrared Emission from the Epsilon Eridani Disk

abstract:
  We model the infrared (IR) emission from the ring-like dust disk around the
main-sequence (MS) star Epsilon Eridani, a young analog to our solar system, in
terms of a porous dust model previously developed for the extended wedge-shaped
disk around the MS star $\beta$ Pictoris and the sharply truncated ring-like
disks around the Herbig Ae/Be stars HR 4796A and HD 141569A. It is shown that
the porous dust model with a porosity of $\simali$90% is also successful in
reproducing the IR to submillimeter dust emission spectral energy distribution
as well as the 850$\mum$ flux radial profile of the dust ring around the more
evolved MS star Epsilon Eridani. Predictions are made for future {\it SIRTF}
observations which may allow a direct test of the porous dust model.


title: Modeling the Infrared Emission from the HD 141569A Disk

abstract:
  We model the infrared (IR) emission from the double-ring disk of HD 141569A,
using a porous dust model that was previously shown successful in reproducing
the spectral energy distributions (SEDs) of the disks around $\beta$ Pictoris
and HR 4796A. The dust consists of either unaltered or highly processed
interstellar materials and vacuum with a volume fraction of ~90%. Together with
a population of polycyclic aromatic hydrocarbon (PAH) molecules of which a
large fraction is charged, the porous dust model made of coagulated but
otherwise unaltered protostellar interstellar grains provides an excellent fit
to the entire SED from the mid-IR to millimeter wavelengths including the PAH
mid-IR emission features. The nondetection of the 21 micron crystalline
silicate feature predicted from the porous dust model composed of
highly-processed grains (mainly crystalline silicate dust) imposes an upper
limit of ~10% on the mass fraction of crystalline silicates. Spectroscopic and
broadband photometric predictions are made for SIRTF observations which will
provide further tests of the applicability of the porous dust model to
circumstellar disks.


title: Modeling the Infrared Emission from the HR 4796A Disk

abstract:
  We model the spectral energy distribution (SED) from the mid-infrared to
submillimeter of the ring-like disk of HR 4796A, the dustiest A-type star. We
consider dust made either of coagulated but otherwise unaltered protostellar
interstellar grains, or grains that are highly-processed in a
protostellar/protoplanetary nebula with silicate dust annealed and carbon dust
oxidized. Both types of dust are successful in reproducing the observed SED,
provided that the grains are highly fluffy, with a vacuum volume fraction of
\~90%. We find no evidence for the existence of a hot ``zodiacal dust''
component a few AU from the star, which was suggested by previous workers to
account for the 10 micron-wavelength emission.


title: The Consistency of Cosmic Flows on 100 Mpc/h Scales

abstract:
  We have compared the bulk flow of recent large-scale peculiar velocity
surveys (SMAC, SC, Lauer and Postman, Willick, EFAR and Tonry's SNIa sample) to
each other, allowing for the errors due to sparse sampling. We conclude that,
contrary to the current perception, there is no significant conflict between
these surveys. The combined peculiar velocity dataset samples a volume $\sim
100 \h^{-1}$ mpc in radius and has a bulk flow of $350 \pm 80 $ km/s. Allowing
for the sparse sampling, we find that this result is not in conflict with the
$\Lambda$CDM models. Structure(s) responsible for the large-scale motion have
not yet been identified, but some likely suspects are presently under
surveillance.


title: Search For Exospheric Signatures From Transiting Planets

abstract:
  We searched for spectral signatures from the exosphere of HD209458 in the UV
and the near-IR with UVES and ISAAC at the VLT. We looked in particular for the
helium absorption feature at 10 830 \AA predicted to be among the strongest
ones. The upper limit of the He I line derived is 0.5% at 3 $\sigma$ for a 3
\AA bandwith. Planet-induced chromospheric activity search on HD209458 was also
performed.


title: The Merger QSO 3C 48 and its Host Galaxy in the Near Infrared

abstract:
  In this contribution we present new near-infrared (NIR) data on the quasar 3C
48 and its host galaxy, obtained with ISAAC at the Very Large Telescope (ESO,
Chile). The NIR images and spectra reveal a reddening of several magnitudes
caused by extinction due to molecular material and dust within the host galaxy.
For the first time we clearly identify the highly reddened potential second
nucleus 3C 48A about 100 northeast of the quasar position in the NIR. Its
reddening can be accounted for by warm dust, heated by star formation or an
interaction of the 3C 48 radio jet with the interstellar medium, or both. The
NIR colors and the CO(6-3) absorption feature both give a stellar contribution
of about 30 percent to the QSO-dominated light. These results will contribute
to the question of how the nuclear activity and the apparent merger process are
influencing the host galaxy properties and they will improve existing models.


title: The late UVOIR light curve of SN 2000cx

abstract:
  We present preliminary data and modeling of the late time light curve of the
Type Ia supernova SN 2000cx. Optical and near-infrared data obtained with the
VLT at 360 to 480 days past maximum light show the increasing importance of the
near-infrared regime. Detailed multi-band modeling based on W7 also show this
effect. Conclusions on positron escape in this phase may therefore require more
detailed observations and modeling than hitherto appreciated.


title:
HE0241-0155 - Evidence for a large scale homogeneous field in a highly
  magnetic white dwarf

abstract:
  In the course of the Hamburg/ESO survey we have discovered a white dwarf
whose spectrum exhibits many similarities with the prototype of magnetic white
dwarfs Grw+70$^{\circ}$8247. In particular several stationary line components
indicative for magnetic fields between about 150 and 400 MG are found in both
objects. However, the features between 5000 and 5500 \AA in the spectrum of
HE0241-0155 cannot be explained by stationary line components and demand a
relatively homogeneous magnetic field with clustering around 200 MG. For this
reason a pure dipole model failed to reproduce this spectral region.An
offset-dipole configuration led to some improvement in the fit but a good
agreement was only possible for a geometry -- described by an expansion into
spherical harmonics -- where most of the surface is covered with magnetic field
strengths strongly clustered around 200 MG. This may indicate the presence of a
large magnetic spot whose presence could be tested with time resolved
spectro-polarimetry.


title: The inner kiloparsec of the jet in 3C264

abstract:
  We present new multi-frequency EVN, MERLIN and VLA observations of the radio
source 3C264, sensitive to linear scales ranging from the parsec to several
kiloparsecs. The observations confirm the existence of regions with different
properties in the first kiloparsec of the jet. The most remarkable feature is
the transition between a well collimated narrow jet at distances from the core
below 80 pc, to a conical-shaped wide jet, with an opening angle of 20 degrees.
Another change of properties, consisting of an apparent deflection of the jet
ridge line and a diminution of the surface brightness, occurs at a distance of
300 pc from the core, coincident with the radius of a ring observed at optical
wavelengths. Our observations add new pieces of information on the spectrum of
the radio-optical jet of 3C264, with results consistent with a synchrotron
emission mechanism and a spectrum break frequency in the infrared. Brightness
profiles taken perpendicularly to the jet of 3C264 are consistent with a spine
brightened jet at distances below 100 pc from the core, and an edge-brightened
jet beyond, which can be interpreted as evidence of a transverse jet velocity
structure. Our observations do not allow us to distinguish between the presence
of a face--on dust and gas disk at the center of the host galaxy of 3C264, or
rather an evacuated bubble. However, the properties of the jet structure, the
changes in the polarization angle, and the plausible jet orientation can be
naturally brought into agreement in the bubble scenario.


title: A SAURON look at galaxy bulges

abstract:
  Kinematic and population studies show that bulges are generally rotationally
flattened systems similar to low-luminosity ellipticals. However, observations
with state-of-the-art integral field spectrographs, such as SAURON, indicate
that the situation is much more complex, and allow us to investigate phenomena
such as triaxiality, kinematic decoupling and population substructure, and to
study their connection to current formation and evolution scenarios for bulges
of early-type galaxies. We present the examples of two S0 bulges from galaxies
in our sample of nearby galaxies: one that shows all the properties expected
from classical bulges (NGC5866), and another case that presents kinematic
features appropriate for barred disk galaxies (NGC7332).


title:
The Liverpool Telescope: Rapid follow-up observation of Targets of
  opportunity with a 2 m robotic telescope

abstract:
  The Liverpool Telescope, situated at Roque de los Muchachos Observatory, La
Palma, Canaries, is the first 2-m, fully instrumented robotic telescope. It
recently began observations. Among Liverpool Telescope's primary scientific
goals is to monitor variable objects on all timescales from seconds to years.
An additional benefit of its robotic operation is rapid reaction to
unpredictable phenomena and their systematic follow up, simultaneous or
coordinated with other facilities. The Target of Opportunity Programme of the
Liverpool Telescope includes the prompt search for and observation of GRB and
XRF counterparts. A special over-ride mode implemented for GRB/XRF follow-up
enables observations commencing less than a minute after the alert, including
optical and near infrared imaging and spectroscopy. In particular, the moderate
aperture and rapid automated response make the Liverpool Telescope excellently
suited to help solving the mystery of optically dark GRBs and for the
investigation of currently unstudied short bursts and XRFs.


title: 44Ti radioactivity in young supernova remnants: Cas A and SN 1987A

abstract:
  We investigate radioactivity from the decay sequence of 44Ti in young
supernova remnants (SNRs), Cassiopeia A (Cas A) and SN 1987A. It is shown by a
linear analysis that ionization of 44Ti, a pure electron capture decay isotope,
affects the radioactivity contradistinctively in these two SNRs: Ionization of
44Ti to H-like and He-like states enhances its present radioactivity in Cas A,
while such high-ionization decreases its radioactivity in SN 1987A. We briefly
discuss the enhancement factor of the present radioactivity of Cas A
considering microscopic (atomic/nuclear) physics combined with a hydrodynamical
SNR evolution model. For SN 1987A, we have obtained the initial 44Ti mass of
(0.82-2.3) X 10^{-4} M_solar from our Monte-Carlo simulations. The resulting
fluxes of gamma and hard X-rays emerged from the 44Ti decay are given for the
current and future experiments.


title: The structure of contact binaries

abstract:
  In radiative layers of rotating stars the luminosity carried by circulation
currents through a surface of constant entropy (circulation luminosity) is
shown to be positive. The corresponding decrease in the temperature gradient is
important in the secondary of contact binaries. This result removes the
deadlock in the theory of contact binaries. The resulting treatment of contact
binaries is investigated, assuming thermal equilibrium. If the circulation
luminosity is adjusted to give a prescribed temperature difference between the
components, details turn out to be unimportant. The temperature difference is
bound to be positive. The fractional extent of radiative regions is larger in
the secondary than in the primary. In the course of evolution the period
increases and the mass ratio decreases. A survey of unevolved and evolved
contact configurations is presented. Observational tests are passed. In stable
systems the degree of contact is small. Stable systems in the period-colour
diagram, unevolved and evolved, cover the strip of observed systems. Lower
limits for period and effective temperature, compatible with the observed
limits, are caused by the requirement of thermal stability. Stable systems with
mass ratios very close to unity are possible, in accordance with recent
observations. These results support the assumption of thermal equilibrium as
well as the treatment of the stability problem. Models for individual observed
systems are well-determined and can be used to calibrate the efficiency of the
energy transfer between the components and to determine metallicity and age.
The results show that evolutionary effects are important and that the
efficiency is very small.


title:
First stars V - Abundance patterns from C to Zn and supernova yields in
  the early Galaxy

abstract:
  In the framework of an ESO Large Programme high quality spectra of 70 very
metal-poor dwarfs and giants were obtained with the VLT-UVES combination. This
paper reports the detailed analyses of the 35 giants of the sample. At the
exception of a few template stars, all the targets are from the H&K Beers et
al. survey. No less than 22 stars have [Fe/H] below -3.0. The imprint of yields
of the first galactic or protogalactic supernovae is sampled in the
photospheres of these stars. If [C/Fe], [Na/Fe] and [Al/Fe] show a spread
significantly above the observational scatter, several abundance ratios present
an amazing low scatter when plotted against [Fe/H], as [Cr/Fe] but also odd
elements, as [K/Fe] or [Sc/Fe]. The abundance of oxygen has been derived from
the [O I] line for 16 of these giants, in spite of the extreme weakness of the
line. No significant slope with [Fe/H] is found. Similar plots have been made
using Mg instead of Fe as reference element. With Mg, no clear trend with
metallicity is obvious below [Mg/H]=-3., except perhaps for [Zn/Mg]. It is
contemplated that the mild slope found in the very low scatter diagram [Cr/Fe]
versus [Fe/H] might be spurious due for example to the LTE approximation plus
use of 1-D models. This would relax the absence of scatter in the dilution of
the SN ejectas within the ambient medium, as needed if [Fe/H] is a well defined
function of [Cr/Fe].


title: Velocity dispersion profile in dark matter halos

abstract:
  Numerous numerical studies indicate that dark matter halos show an almost
universal radial density profile. The origin of the profile is still under
debate. We investigate this topic and pay particular attention to the velocity
dispersion profile. To this end we have performed high-resolution simulations
with two independent codes, ART and {\sc Gadget}. The radial velocity
dispersion can be approximated as function of the potential by $\sigma_r^2 = a
(\Phi / \Phi_{\rm{out}})^\kappa (\Phi_{\rm{out}} - \Phi)$, where
$\Phi_{\rm{out}}$ is the outer potential of the halo. For the parameters $a$
and $\kappa$ we find $a=0.29\pm0.04$ and $\kappa=0.41\pm0.03$. We find that the
power-law asymptote $\sigma^2 \propto \Phi^\kappa$ is valid out to much larger
distances from the halo center than any power asymptote for the density profile
$\rho \propto r^{-n}$. The asymptotic slope $n(r \to 0)$ of the density profile
is related to the exponent $\kappa$ via $n=2\kappa/(1+\kappa)$. Thus the value
obtained for $\kappa$ from the available simulation data can be used to obtain
an estimate of the density profile below presently resolved scales. We predict
a continuously decreasing $n$ towards the halo center with the asymptotic value
$n \lesssim 0.58$ at $r=0$.


title: BeppoSAX Observations of 1-Jy BL Lacertae Objects - II

abstract:
  We present new BeppoSAX LECS and MECS observations, covering the energy range
0.1 - 10 keV (observer's frame), of four BL Lacertae objects selected from the
1 Jy sample. All sources display a flat (alpha_x ~ 0.7) X-ray spectrum, which
we interpret as inverse Compton emission. One object shows evidence for a
low-energy steepening (Delta alpha_x ~ 0.9) which is likely due to the
synchrotron component merging into the inverse Compton one around ~ 2 keV. A
variable synchrotron tail would explain why the ROSAT spectra of our sources
are typically steeper than the BeppoSAX ones (Delta alpha_x} ~ 0.7). The
broad-band spectral energy distributions fully confirm this picture and model
fits using a synchrotron inverse Compton model allow us to derive the physical
parameters (intrinsic power, magnetic field, etc.) of our sources. By combining
the results of this paper with those previously obtained on other sources we
present a detailed study of the BeppoSAX properties of a well-defined
sub-sample of 14 X-ray bright (f_x (0.1 - 10 keV) > 3 x 10^{-12} erg/cm^2/s)
1-Jy BL Lacs. We find a very tight proportionality between nearly simultaneous
radio and X-ray powers for the 1-Jy sources in which the X-ray band is
dominated by inverse Compton emission, which points to a strong link between
X-ray and radio emission components in these objects.


title: Contact binary stars of the W UMa type as distance tracers

abstract:
  Contact binaries can be used for distance determinations of stellar systems.
They are easy to discover and identify and are very abundant among solar-type
stars, particularly for M_V > +3. The period - luminosity - colour (PLC)
relations have similar properties to those for pulsating stars and can
currently predict individual values of M_V to about +/-0.25 mag.


title:
Astrophysical tau neutrinos and their detection by large neutrino
  telescopes

abstract:
  We present results of the detailed Monte Carlo calculation of the rates of
double-bang events in 1 km$^3$ underwater neutrino telescope with taking into
account the effects of $\tau$-neutrino propagation through the Earth. As an
input, the moderately optimistic theoretical predictions for diffuse neutrino
spectra of AGN jets are used.


title:
Serendipity and the SDSS: Discovery of the Largest Known Planetary
  Nebula on the Sky

abstract:
  Investigation of spectra from the Sloan Digital Sky Survey reveals the
presence of a region of ionized gas of >2 degrees diameter centered
approximately at alpha = 10^h 37^m delta = -00^o 18' (J2000) (Galactic
coordinates l=248, b=+48). [OIII] 4959,5007 emission is particularly strong and
emission from H-alpha and [NII] 6548,6583 is also detectable over a substantial
area on the sky. The combination of emission line ratios, the close to zero
heliocentric radial velocity and the morphology of the structure are consistent
with an identification as a very nearby planetary nebula. The proximity of the
hot, DO white dwarf PG1034+001 further strengthens this interpretation. The
object is: i) the largest planetary nebula on the sky, ii) certainly closer
than any planetary nebula other than Sh 2--216, iii) the first to be
unambiguously associated with a DO white dwarf. A parallax distance for
PG1034+001 would establish whether the structure is in fact the closest, and
one of the physically largest, planetary nebula known.


title:
SDSS J161033.64-010223.3: A second Cataclysmic Variable with a
  Non-radially Pulsating Primary

abstract:
  We find from high speed photometry of the Sloan Digital Survey cataclysmic
variable candidate SDSS J161033.64-010223.3 that it has a double humped
modulation, which is probably orbital, with a period of 80.52 minutes, and
shows strong ZZ Cet type pulsations. The largest amplitude oscillations have
periods near 607, 345, 304 and 221 s. The amplitudes of some of the
oscillations are seen to vary on time scales of hours, indicating modes with
unresolved multiplets in which the splittings are ~1 d^-1. This is only the
second dwarf nova found to have non-radial pulsations of its white dwarf
primary.


title: Hot Gas in the Local Group and Low-Redshift Intergalactic Medium

abstract:
  There is increasing observational evidence that hot, highly ionized
interstellar and intergalactic gas plays a significant role in the evolution of
galaxies in the local universe. The primary spectral diagnostics of the
warm-hot interstellar/intergalactic medium are ultraviolet and X-ray absorption
lines of O VI and O VII. In this paper, I summarize some of the recent
highlights of spectroscopic studies of hot gas in the Local Group and
low-redshift universe. These highlights include investigations of the baryonic
content of low-z O VI absorbers,evidence for a hot Galactic corona or Local
Group medium, and the discovery of a highly ionized high velocity cloud system
around the Milky Way.


title: Tracing the Star Stream Through M31 Using Planetary Nebula Kinematics

abstract:
  We present a possible orbit for the Southern Stream of stars in M31, which
connects it to the Northern Spur. Support for this model comes from the
dynamics of planetary nebulae (PNe) in the disk of M31: analysis of a new
sample of 2611 PNe obtained using the Planetary Nebula Spectrograph reveals ~20
objects whose kinematics are inconsistent with the normal components of the
galaxy, but which lie at the right positions and velocities to connect the two
photometric features via this orbit. The satellite galaxy M32 is coincident
with the stream both in position and velocity, adding weight to the hypothesis
that the stream comprises its tidal debris.


title: 26Al yields from rotating Wolf--Rayet star models

abstract:
  We present new $^{26}$Al stellar yields from rotating Wolf--Rayet stellar
models which, at solar metallicity, well reproduce the observed properties of
the Wolf-Rayet populations. These new yields are enhanced with respect to
non--rotating models, even with respect to non--rotating models computed with
enhanced mass loss rates. We briefly discuss some implications of the use of
these new yields for estimating the global contribution of Wolf-Rayet stars to
the quantity of $^{26}$Al now present in the Milky Way.


title: X-ray observations of Be/X-ray binaries in the SMC

abstract:
  (shortened) Fifteen Be/X-ray binaries and candidates in the SMC were observed
serendipitously with the EPIC instruments of XMM-Newton during two observations
of SNR 0047-73.5 and SNR 0103-72.6 in October 2000. A total of twelve of those
sources are detected. For eleven of them an accurate position and in part
detection of X-ray pulsations support the proposed identification as Be/X-ray
binaries. The detection of pulsations (172.2 s, 320.1 s and 751 s) from three
hard X-ray sources with periods known from ASCA observations confirm their
proposed identifications with ROSAT sources and their optical Be star
counterparts. In addition, pulsations with a period of 263.6 s were found from
XMMUJ004723.7-731226=RXJ0047.3-7312. For SAXJ0103.2-7209 a pulse period of
341.2$\pm$0.5 s was determined, continuing the large spin-up seen with ASCA,
BeppoSAX and Chandra between 1996 and 1999 with a period derivative of $-$1.6 s
yr$^{-1}$ covering now 4.5 years. The 0.3-10.0 keV EPIC spectra of all eleven
Be/X-ray binaries and candidates are consistent with power-law energy
distributions with derived photon indices strongly peaked at 1.00 with a
standard deviation of 0.16. No pulsations are detected from RXJ0049.2-7311 and
RXJ0049.5-7310 (both near the 9 s pulsar AXJ0049-732) and RXJ0105.1-7211 (near
AXJ0105-722, which may pulsate with 3.3 s), leaving the identification of the
ASCA sources with ROSAT and corresponding XMM-Newton objects still unclear. We
present an updated list of high mass X-ray binaries (HMXBs) and candidates in
the SMC incorporating improved X-ray positions obtained from Chandra and
XMM-Newton observations. Including the results from this work and recent
publications the SMC HMXB catalogue comprises 65 objects with at least 37
showing X-ray pulsations.


title: Massive scalar fields in the early Universe

abstract:
  We discuss the role of gravitational excitons/radions in different
cosmological scenarios. Gravitational excitons are massive moduli fields which
describe conformal excitations of the internal spaces and which, due to their
Planck-scale suppressed coupling to matter fields, are WIMPs. It is
demonstrated that, depending on the concrete scenario, observational
cosmological data set strong restrictions on the allowed masses and initial
oscillation amplitudes of these particles.


title: Identification of gravity waves in hydrodynamical simulations

abstract:
  The excitation of internal gravity waves by an entropy bubble oscillating in
an isothermal atmosphere is investigated using direct two-dimensional numerical
simulations. The oscillation field is measured by a projection of the simulated
velocity field onto the anelastic solutions of the linear eigenvalue problem
for the perturbations. This facilitates a quantitative study of both the
spectrum and the amplitudes of excited g-modes.


title:
Investigating the central engine of Seyfert 2 galaxies with and without
  Polarized Broad Lines

abstract:
  We study the hard X-ray emission of two samples of Seyfert 2 galaxies with
and without Polarized Broad Lines (PBL). In the hard X-ray domain, absorption
effects do not significantly modify the intrinsic emission allowing us a direct
access to the central engine. The purpose of this study is to compare the
primary emission of the two Seyfert 2 subclasses in order to investigate the
nature of their central engine and to test unified models according to which
they both have a hidden Seyfert 1 nucleus. We compute the average hard X-ray
spectra of Seyfert 2 galaxies with and without PBL observed with
  BeppoSAX/PDS (15-136 keV).
  The two spectra have a common general behavior at first sight, but
investigating deeper we find differences in the intrinsic properties of the two
categories of Seyfert 2 galaxies. Sy 2 with polarized broad lines have physical
conditions close to those of Sy 1 galaxies whereas Sy 2 without PBL differ
substantially, suggesting that they may have a particular place in the scheme
of Seyfert galaxies.


title: On the bispectrum of COBE and WMAP

abstract:
  The COBE-DMR 4-year maps displayed a strong non-Gaussian signal in the
``inter-scale'' components of the bispectrum: their observed values did not
display the scatter expected from Gaussian maps. We re-examine this and other
suggested non-Gaussian features in the light of WMAP. We find that they all
disappear. Given that it was proved that COBE-DMR high noise levels and
documented systematics could at most {\it dilute} the observed non-Gaussian
features, we conclude that this dataset must have contained non-negligible
undocumented systematic errors. It turns out that the culprit is a combination
of QuadCube pixelization and data collected during the ``eclipse season''.


title: Fluctuations of K-band galaxy counts

abstract:
  We measure the variance in the distribution of off-plane (|b|>20 deg.)
galaxies with m_K<13.5 from the 2MASS K-band survey in circles of diameter
between 0.344 deg. and 57.2 deg. The use of a near-infrared survey makes
negligible the contribution of Galactic extinction to these fluctuations. We
calculate these variances within the standard Lambda-CDM model assuming that
the sources are distributed like halos of the corresponding mass, and it
reproduces qualitatively the galaxy counts variance. Therefore, we test that
the counts can be basically explained in terms only of the large scale
structure. A second result of this paper is a new method to determine the two
point correlation function obtained by forcing agreement between model and
data. This method does not need the knowledge of the two-point angular
correlation function, allows an estimation of the errors (which are low with
this method), and can be used even with incomplete surveys.
  Using this method we get xi(z=0, r<10 h^{-1}Mpc)=(29.8+/-0.3)
(r/h^{-1}Mpc)^{-1.79+/-0.02}, which is the first measure of the amplitude of xi
in the local Universe for the K-band. It is more or less in agreement with
those obtained through red optical filters selected samples, but it is larger
than the amplitude obtained for blue optical filters selected samples.


title: XMM-Newton Witness of M86 X-ray Metamorphosis

abstract:
  The environmental influence of cluster media on its member galaxies, known as
Butcher--Oemler effect, has recently been subject to revision due to numerous
observations of strong morphological transformations occurring outside the
cluster virial radii, caused by some unidentified gas removal processes. In
this context we present new XMM-Newton observations of M86 group. The unique
combination of high spatial and spectral resolution and large field of view of
XMM-Newton allows an in-depth investigation of the processes involved in the
spectacular disruption of this object. We identify a possible shock with Mach
number of ~1.4 in the process of crushing the galaxy in the North-East
direction. The latter is ascribed to the presence of a dense X-ray emitting
filament, previously revealed in the RASS data. The shock is not associated
with other previously identified features of M86 X-ray emission, such as the
plume, the north-eastern arm and the southern extension, which are found to
have low entropy, similar to the inner 2 kpc of M86. Finally, mere existence of
the large scale gas halo around the M86 group, suggests that the disruptions of
M86's X-ray halo may be caused by small-scale types of interactions such as
galaxy-galaxy collisions.


title: Parsec-Scale Herbig-Haro Outflows from Intermediate Mass Stars

abstract:
  While there are many parsec-scale Herbig-Haro (HH) outflows known to be
driven by low-mass young stars, few are associated with their intermediate mass
counterparts. Here we present the discovery of five such bipolar outflows. Of
these, LkHalpha 198, 1548C27 IRS1, LkHalpha 233 and LkHalpha 234 were
previously known to possess small-scale HH flows, while no such activity was
observed before near IRAS 19395+2313. The largest of the newly discovered
outflows are seen in the vicinity of LkHalpha 234 and 1548C27 IRS1, and stretch
(in projection) 8pc and 7.5pc respectively. LkHalpha 233 which was previously
known to power a spectroscopically detected small-scale (< 10'') jet is now
seen to drive a 3pc outflow and LkHalpha 198 is shown here to power a 2pc
outflow. Two HH objects in the vicinity of IRAS 19395+2313 lead us to suggest
that it may also be responsible for a 5pc outflow. In total, 27 new HH
objects/complexes were discovered. Examination of these parsec-scale outflows
show that they have similar lengths, morphologies, and dynamical timescales as
those from low-mass sources. Many appear to have blown out of the parent cloud,
suggesting that their total lengths are much greater than optically observed.
The degree of collimation of these outflows is similar to those from low-mass
sources suggesting that the transition to more poorly-collimated outflows must
occur at higher masses than the sources observed here.


title: Properties of Dark Matter Halos in Disk Galaxies

abstract:
  We present a simple technique to estimate mass-to-light (M/L) ratios of
stellar populations based on two broadband photometry measurements, i.e. a
color-M/L relation. We apply the color-M/L relation to galaxy rotation curves,
using a large set of galaxies that span a great range in Hubble type,
luminosity and scale size and that have accurately measured HI and/or Halpha
rotation curves. Using the color-M/L relation, we construct stellar mass models
of the galaxies and derive the dark matter contribution to the rotation curves.
  We compare our dark matter rotation curves with adiabatically contracted
Navarro, Frenk, & White (1997, NFW hereafter) dark matter halos. We find that
before adiabatic contraction most high surface brightness galaxies and some low
surface brightness galaxies are well fit by a NFW dark matter profile. However,
after adiabatic contraction, most galaxies are poorly fit in the central few
kpc. The observed angular momentum distribution in the baryonic component is
poorly matched by LambdaCDM model predictions, indicating that the angular
momentum distribution is not conserved during the galaxy assembly process. We
find that in most galaxies the dark matter distribution can be derived by
scaling up the HI gas contribution. However, we find no consistent value for
the scaling factor among all the galaxies.


title:
Star Clusters in the Galactic Anticenter Stellar Structure and the
  Origin of Outer Old Open Clusters

abstract:
  The Galactic Anticenter Stellar Structure (GASS) has been identified with
excess surface densities of field stars in several large area sky surveys, and
with an unusual, string-like grouping of five globular clusters. At least two
of these are diffuse, young ``transitional'' clusters between open and globular
types. Here we call attention to the fact that four {\it younger} open or
transitional clusters extend the previously identified, string-like cluster
grouping, with at least one having a radial velocity consistent with the
previously found GASS velocity-longitude trend. All nine clusters lie close to
a plane tipped 17$\arcdeg$ to the Galactic plane. This planar orientation is
used to forage for additional potential cluster members in the inner Galaxy,
and a number are found along the same plane and string-like sequence, {\it
including almost all fifteen known outer, old open clusters}. Tidal accretion
of a dwarf satellite galaxy on a low inclination orbit -- perhaps the GASS
system -- appears to be a plausible explanation for the origin of the outer,
old open and transitional clusters of the Milky Way. We use these clusters to
explore the age-metallicity relation of the putative accreted GASS progenitor.
Finally, we provide the first radial velocity of a star in the cluster BH 176
and discuss its implications.


title:
WMAP, neutrino degeneracy and non-Gaussianity constraints on
  isocurvature perturbations in the curvaton model of inflation

abstract:
  In the curvaton model of inflation, where a second scalar field, the
"curvaton", is responsible for the observed inhomogeneity, a non-zero neutrino
degeneracy may lead to a characteristic pattern of isocurvature perturbations
in the neutrino, cold dark matter and baryon components. We find the current
data can only place upper limits on the level of isocurvature perturbations.
These can be translated into upper limits on the neutrino degeneracy parameter.
In the case that lepton number is created before curvaton decay, we find that
the limit on the neutrino degeneracy parameter is comparable with that obtained
from Big-bang nucleosynthesis. For the case that lepton number is created by
curvaton decay we find that the absolute value of the non-Gaussianity
parameter, |f_nl|, must be less than 10 (95% confidence interval).


title:
Photoionization cross sections of O II, O III, O IV, and O V:
  benchmarking R-matrix theory and experiments

abstract:
  For crucial tests between theory and experiment, ab initio close coupling
calculations are carried out for photoionization of O II, O III, O IV, O V. The
relativistic fine structure and resonance effects are studied using the
R-matrix and its relativistic variant the Breit Pauli R-matrix (BPRM)
approximation. Detailed comparison is made with high resolution experimental
measurements carried out in three different set-ups: Advanced Light Source at
Berkeley, and synchrotron radiation experiments at University of Aarhus and
University of Paris-Sud. The comparisons illustrate physical effects in
photoionization such as (i) fine structure, (ii) resolution, and (iii)
metastable components. Photoionization cross sections sigma{PI} of the ground
and a few low lying excited states of these ions obtained in the experimental
spectrum include combined features of these states. Theoretically calculated
resonances need to be resolved with extremely fine energy mesh for precise
comparison. In addition, prominent resonant features are observed in the
measured spectra from transitions allowed with relativistic fine structure, but
not in LS coupling. The sigma_{PI} are obtained for ground and metastable (i)
2s^22p^3(^4S^o, ^2D^o, ^2P^o) states of O II, (ii) 2s^22p^2(^3P,^1D,^1S) and
2s2p^3(^5S^o) states of O III, (iii) 2s^22p(^2P^o_J) and 2s2p^2(^4P_J) levels
of O IV, and (iv) 2s^2(^1S) and 2s2p(^3P^o,^1P^o) states of O V. It is found
that resonances in ground and metastable cross sections can be a diagnostic of
experimental beam composition, with potential ap plications to astrophysical
and laboratory plasma environments.


title: Tomography of lensing cross power spectra

abstract:
  By obtaining photometric redshift information, tomography allows us to
cross-correlate galaxy ellipticities in different source redshift bins. The
cross-correlation is non-vanishing because the different bins share much of the
foreground mass distribution from which, over Gpc scales, the lensing signal is
built. If the redshift bins are thick enough however, the cross-correlations
are insensitive to contamination from the intrinsic alignments of galaxies
since these fall off rapidly on scales larger than a few tens of Mpc. We
forecast how lensing tomography using only the cross-power spectra can
constrain cosmological parameters compared to tomography including the
auto-spectra. It is shown that the parameter errors are degraded by only O(10%)
for 5 or more source redshift bins. Thus, the cross-power spectrum tomography
can be a simple, model-independent means of reducing the intrinsic alignment
contamination while retaining most of the constraints on cosmology.


title: Cluster of Galaxies: An X-ray Perspective

abstract:
  There has been extensive recent progress in X-ray observations of clusters of
galaxies with the analysis of the entire ASCA database and recent new results
from Beppo-SAX, Chandra, and XMM-Newton. The temperature profiles of most
clusters are isothermal from 0.05--0.6 virial radii, contrary to theoretical
expectations and early results from ASCA. Similarly, the abundance profiles of
Fe are roughly constant outside the central regions. The luminosity-temperature
relation for a very large sample of clusters show that L_X is proportional to
T^3 over the whole observable luminosity range at low redshift, but the
variance increases at low luminosity, explaining the previously claimed
steepening at low luminosity. Recent accurate cluster photometry in red and
infrared passbands have resulted in much better correlations of optical and
X-ray properties, but there is still larger scatter than one might expect
between total light and X-ray temperature and luminosity. The velocity
dispersion and the X-ray temperature are strongly correlated, but the slope of
the relation is somewhat steeper than expected. The surface brightness profiles
of clusters are very well fit by the isothermal beta model out to large radii
and show scaling relations, outside the central regions, consistent with a
Lambda-dominated Universe.


title: Star Clusters in Virgo and Fornax Dwarf Irregular Galaxies

abstract:
  We present the results of a search for clusters in dwarf irregular galaxies
in the Virgo and Fornax Cluster using HST WFPC2 snapshot data. The galaxy
sample includes 28 galaxies, 11 of which are confirmed members of the Virgo and
Fornax clusters. In the 11 confirmed members, we detect 237 cluster candidates
and determine their V magnitudes, V-I colors and core radii. After statistical
subtraction of background galaxies and foreground stars, most of the cluster
candidates have V-I colors of -0.2 and 1.4, V magnitudes lying between 20 and
25th magnitude and core radii between 0 and 6 pc. Using H-alpha observations,
we find that 26% of the blue cluster candidates are most likely HII regions.
The rest of the cluster candidates are most likely massive (>10^4 Msol) young
and old clusters. A comparison between the red cluster candidates in our sample
and the Milky Way globular clusters shows that they have similar luminosity
distributions, but that the red cluster candidates typically have larger core
radii. Assuming that the red cluster candidates are in fact globular clusters,
we derive specific frequencies (S_N) ranging from ~0-9 for the galaxies.
Although the values are uncertain, seven of the galaxies appear to have
specific frequencies greater than 2. These values are more typical of
ellipticals and nucleated dwarf ellipticals than they are of spirals or Local
Group dwarf irregulars.


title: The Extragalactic Origin of the Arcturus Group

abstract:
  We reanalyze the group of stars associated kinematically with Arcturus (Eggen
1971), and confirm that they constitute a peculiar grouping of metal-poor stars
with similar apocentric radius, common angular momentum, and distinct metal
abundance patterns. These properties are consistent with those expected for a
group of stars originating from the debris of a disrupted satellite. The
Arcturus group stands out clearly in the catalog of Beers et al. (2000) as well
as in other compilations of metal-poor stars in the solar neighborhood. Its
angular momentum appears too low to arise from dynamical perturbations induced
by the Galactic bar, and coincides with that of the kinematically-peculiar
population of stars identified above and below the Galactic plane by Gilmore,
Wyse & Norris (2002): the Arcturus group is in all likelihood the solar
neighborhood extension of such population. Further analysis is needed to
confirm our proposal that Arcturus, together with some of the brightest stars
in the night sky, may have formed beyond the confines of the Galaxy. However,
validating the extragalactic origin of the Arcturus group would lend support to
the prevalence of accretion events envisioned in hierarchical models of galaxy
formation, and would suggest that early mergers may have contributed a
substantial fraction of the old and metal-deficient stars in the Galactic disk.


title: Outflows vs. Clouds in AGN Intrinsic Absorbers

abstract:
  We discuss the crucial role of a dynamical picture in the analysis of AGN
intrinsic absorbers data. High quality FUSE data of Mrk 279 are used to
demonstrate that the line of sight covering fraction is a strong function of
velocity. In Mrk 279, as well as in most cases where the data is of high enough
quality, the shape of the absorption troughs is mainly determined by the
velocity-dependent covering fraction. We argue that the traditional ``cloud''
picture of AGN outflows is hard pressed to account for the velocity-dependent
covering fraction, as well as for the highly super-thermal width of the troughs
and the detached trough phenomenon. A disk outflow picture naturally explains
these features and furthermore, is using the simplest reservoir for the
outflowing material: The accretion disk around the black hole. Accounting for
velocity dependent covering can drastically increase the inferred ionic column
density of the analyzed trough, an increase which is amplified in the total
column density and ionization parameter solution for the AGN outflow trough.


title:
Earliest detection of the optical afterglow of GRB 030329 and its
  variability

abstract:
  We report the earliest detection of an extremely bright optical afterglow of
the gamma-ray burst (GRB) 030329 using a 30cm-telescope at Tokyo Institute of
Technology (Tokyo, JAPAN). Our observation started 67 minutes after the burst,
and continued for succeeding two nights until the afterglow faded below the
sensitivity limit of the telescope (approximately 18 mag). Combining our data
with those reported in GCN Circulars, we find that the early afterglow light
curve of the first half day is described by a broken power-law (t^{- alpha})
function with indices alpha_{1} = 0.88 +/- 0.01 (0.047 < t < t_{b1} days),
alpha_{2} = 1.18 +/- 0.01 (t_{b1} < t < t_{b2} days), and alpha_{3} = 1.81 +/-
0.04 (t_{b2} < t < 1.2 days), where t_{b1} ~ 0.26 days and t_{b2} ~ 0.54 days,
respectively. The change of the power-law index at the first break at t ~ 0.26
days is consistent with that expected from a ``cooling-break'' when the cooling
frequency crossed the optical band. If the interpretation is correct, the decay
index before the cooling-break implies a uniform ISM environment.


title:
A study of the Galactic star forming region IRAS 02593+6016 / S 201 in
  infrared and radio wavelengths

abstract:
  We present infrared and radio continuum observations of S 201 star forming
region. A massive star cluster is observed in this region, which contains
different classes of young stellar objects. The near-infrared colour-colour and
colour-magnitude diagrams are studied to discuss the nature of these sources.
We have discovered the knots of molecular hydrogen emission at 2.122 micron in
the central region of S 201. These knots are clearly seen along the diffuse
emission in north-west direction which are probably the obscured Herbig-Haro
objects. High sensitivity and high resolution radio continuum images from GMRT
observations at 610 and 1280 MHz show an interesting arc-shaped structure due
to the interaction between the H II region and the adjacent molecular cloud.
The ionization front at the interface between the H II region and the molecular
cloud is clearly seen by comparing the radio, molecular hydrogen and Br Gamma
images. The emission from the carriers of Unidentified Infrared Bands in the
mid-infrared 6-9 micron (possibly due to PAHs) as extracted from the Midcourse
Space Experiment survey (at 8, 12, 14 and 21 micron) is compared with the radio
emission. The HIRES processed IRAS maps at 12, 25, 60, and 100 micron, have
also been used for comparison. The spatial distribution of the temperature and
the optical depth of the warm dust component around S 201 region, has been
generated from the mid-infrared images.


title: On the mechanism of prompt emission of gamma-ray bursts

abstract:
  We propose a model in which prompt gamma emission of gamma-ray bursts is the
synchrotron radiation of electron-positron plasma in the ordered magnetic field
in the direct vicinity of horizon of a young black hole formed in the core
collapse of a massive star. This mechanism can naturally explain high degree of
polarization of the gamma-ray flux and hard low energy photon spectral index.
Interaction of gamma-quanta with ambient matter provides a mechanism of
formation of relativistic ejecta which are responsible for the gamma-ray burst
afterglows.


title:
X-ray Underluminous Active Galactic Nuclei Relative to Broad Emission
  Lines in Ultraluminous Infrared Galaxies

abstract:
  We present X-ray spectra of four ultraluminous infrared galaxies (ULIRGs)
with detectable broad near-infrared emission lines produced by active galactic
nuclei (AGNs): Mrk 463, PKS 1345+12, IRAS 05189-2524, and IRAS 07598+6508. With
the exception of IRAS 07598+6508, high quality X-ray spectra obtained with XMM
or Chandra show modest (30-340 eV) equivalent widths of the 6.4 keV Fe K alpha
emission line and clear signatures for absorption at a level of 4-33 * 10^22
cm^-2 for the main power-law components from the AGNs. These spectral
properties are typical of Compton-thin AGNs, and so we estimate
absorption-corrected 2-10 keV X-ray luminosities for the AGNs, Lx(2-10keV),
using the Compton-thin assumption. We compare the Lx(2-10 keV) values with
broad optical/near-infrared emission-line luminosities, and confirm a previous
finding by Imanishi & Ueno that the Lx(2-10 keV) to broad-emission-line
luminosity ratios in ULIRGs are systematically lower than those of moderately
infrared-luminous type-1 AGNs. A comparison of independent energy diagnostic
methods suggests that the AGNs are underluminous in the 2-10 keV band with
respect to their overall spectral energy distributions, as opposed to the broad
emission lines being overluminous. This X-ray under-luminosity should be taken
into account when using 2-10 keV X-ray data to investigate the energetic
contribution from AGNs to the large infrared luminosities of ULIRGs.


title:
Star formation rates of distant luminous infrared galaxies derived from
  Halpha and IR luminosities

abstract:
  We present a study of the star formation rate (SFR) for a sample of 16
distant galaxies detected by ISOCAM at 15um in the CFRS0300+00 and CFRS1400+52
fields. Their high quality and intermediate resolution VLT/FORS spectra have
allowed a proper correction of the Balmer emission lines from the underlying
absorption. Extinction estimates using the Hbeta/Hgamma and the Halpha/Hbeta
Balmer decrement are in excellent agreement, providing a robust measurement of
the instantaneous SFR based on the extinction-corrected Halpha luminosity. Star
formation has also been estimated exploiting the correlations between IR
luminosity and those at MIR and radio wavelengths. Our study shows that the
relationship between the two SFR estimates follow two distinct regimes: (1) for
galaxies with SFRIR below ~ 100Msolar/yr, the SFR deduced from Halpha
measurements is a good approximation of the global SFR and (2) for galaxies
near of ULIRGs regime, corrected Halpha SFR understimated the SFR by a factor
of 1.5 to 2. Our analyses suggest that heavily extincted regions completely
hidden in optical bands (such as those found in Arp 220) contribute to less
than 20% of the global budget of star formation history up to z=1.


title:
Powerful flaring configurations in solar active regions: magnetic
  topology via special features of delta-structure phenomenon. I. Basic
  principles of topological model

abstract:
  The close connection of magnetic field structure on the one hand and
observable features of complex ARs with high flare efficiency on the other one
is investigated in frames of so-called dynamic classification of flaring
magnetic configurations (FMC) and the simple topological model of interacting
magnetic complexes (IMC) suggested by Ikhsanov (1982). The primary objective of
the present work is to expose general statements of the specified model and
classification, the secondary one assumes the critical analysis and logical
generalization of several important regularities being frequently observable in
evolution stages of a typical complex AR with powerful flares including proton
ones. Those cases are basically examined where the development of photospheric
situation was marked by the formation of delta-configuration phenomenon
described by Kunzel (1960) as one of the most impressive precursors of high
flare activity. Without trying to use any additional assumptions and
alternative hypotheses, the qualitative analysis of physical reasons and
formative conditions of various delta-configuration classes in solar ARs is
carried out. An attempt to construct the non-contradictory physical
interpretation of morphological, flare-productive and magnetic features of such
configurations is also done. In fact, the authors intend to demonstrate that
the analysis of delta-structure phenomenon from the IMC-based point of view
allows to explain well many early established regularities as kindred phenomena
having the uniform physical reason.


title: Microlensing signature of a white dwarf population in the galactic halo

abstract:
  Microlensing and pixel-lensing surveys play a fundamental role in the
searches for galactic dark matter and in the study of the galactic structure.
Recent observations suggest the presence of a population of old white dwarfs
with high proper motion, probably in the galactic halo, with local mass density
in the range $1.3\times 10^{-4}-4.4\times 10^{-3} M_{\odot}$ pc$^{-3}$, in
addition to the standard galactic stellar disk and dark halo components.
Investigation of the signatures on microlensing results towards the LMC of
these different lens populations, with particular emphasis to white dwarfs, is
the main purpose of the present paper. This is done by evaluating optical depth
and microlensing rate of the various lens populations and then calculating
through a Montecarlo program, the probability that a lens which has caused a
microlensing event of duration $t_{\rm E}$ belongs to a certain galactic
population. Data obtained by the MACHO Collaboration allow us to set an upper
bound of $1.6\times 10^{-3} M_{\odot}$ pc$^{-3}$ to the local mass density of
white dwarfs distributed in spheroidal models, while for white dwarfs in disk
models all values for the local mass density are in agreement with
observational results.


title: Self-similar collapse with cooling and heating in an expanding universe

abstract:
  We derive self-similar solutions including cooling and heating in an Einstein
de-Sitter universe, and investigate the effects of cooling and heating on the
gas density and temperature distributions. We assume that the cooling rate has
a power-law dependence on the gas density and temperature,
$\Lambda$$\propto$$\rho^{A}T^{B}$, and the heating rate is
$\Gamma$$\propto$$\rho T$. The values of $A$ and $B$ are chosen by requiring
that the cooling time is proportional to the Hubble time in order to obtain
similarity solutions. In the region where the cooling rate is greater than the
heating rate, a cooling inflow is established, and the gas is compressed and
heats up. Because the compression is greater in the inner region than in the
outer region, the temperature becomes an increasing profile toward the center.
In particular, when a large infall velocity is produced due to an enormous
energy loss, the slope of the density approaches a value that depends on $A$,
$B$, and the velocity slope, and the slope of the temperature approaches $-$1.
On the other hand, in the region where the heating rate is greater than the
cooling rate, the infall velocity is suppressed, compression of the gas is
weakened, and the gas cools down. The slope of the density becomes shallow due
to suppression of the contraction, and the temperature is lower than that
without heating. The self-similar collapse presented here gives insights to the
effects of cooling and heating on the gas distributions in galaxies and
clusters of galaxies.


title: CDM in LSB Galaxies: Toward the Optimal Halo Profile

abstract:
  Low Surface Brightness (LSB) galaxies are dominated by dark matter.
High-resolution rotation curves suggest that their total mass-density
distributions are dominated by constant density cores rather than the steep and
cuspy distributions found in Cold Dark Matter (CDM) simulations. The data are
best described by a model with a soft core with an inner power-law mass-density
slope alpha = 0.2 +/- 0.2. However no single universal halo profile provides an
adequate description of the data. The observed mass profiles appear to be
inconsistent with LambdaCDM.


title:
Faint galaxy population in clusters: X-ray emission, cD halos and
  projection effects

abstract:
  We analyze samples of nearby clusters taken from the Abell catalog and the
X-ray Sample of Bright Clusters(De Grandi et al 1999) including a wide range of
X-ray luminosities.Using the usually adopted background subtraction procedures,
we find that galaxies in clusters selected by means of their X-ray emission
show a flat luminosity function (faint end slope $\alpha \simeq -1.1$)
consistent with that derived for galaxies in the field and groups. By contrast,
the sample of Abell clusters that do not have an X-ray counterpart shows a
galaxy luminosity function with a steep faint end ($\alpha \simeq -1.6$). We
investigate the possibility that cD halos could be formed by the disruption of
galaxies in rich relaxed clusters that show an apparently flat faint end galaxy
luminosity function (Lopez-Cruz et al 1997).
  We find that clusters dominated by a central cD galaxy (Bautz-Morgan classes
I and II) show the same systematic trend: X-ray selected clusters have flatter
faint end slopes than those clusters with no detected X-ray emission. Thus, it
is likely the X-ray selection and not the cluster domination by central
galaxies what correlates with background decontamination estimates of the
galaxy luminosity function. Moreover, no significant correlation between X-ray
luminosity and the galaxy LF faint end slope is found. These results do not
support a scenario where flat faint end slopes are a consequence of cD
formation via the disruption of faint galaxies. We argue that the clusters
without X-ray emission are strongly affected by projection effects which give
rise to spurious faint end slopes estimated using background subtraction
procedures (Valotto et al 2001).


title:
Detection of the Canis Major galaxy at (l;b)=(244;-8) and in the
  background of Galactic open clusters

abstract:
  We report on the detection of Main Sequence stars belonging to the recently
identified Canis Major galaxy in a field located at ~ 4.2 deg from the center
of the stellar system. With Main Sequence fitting we obtain a distance modulus
(m-M)_0=14.5 +/- 0.3 to the dwarf, corresponding to a distance of D_{sun} = 8.0
+/- 1.2 kpc, in full agreement with previous estimates based on the photometric
parallax of M-giants. From the comparison with theoretical isochrones we
constrain the age of the main population of the Canis Major system in the range
\~ 4-10 Gyr. A blue plume of likely younger stars (age < 1-2 Gyr) is also
identified. The available Colour Magnitude Diagrams of open clusters that may
be projected onto the main body of Canis Major are also briefly analyzed. The
position, distance and stellar population of the old open clusters AM-2 and
Tombaugh 2 strongly suggest that they are physically associated with the Canis
Major galaxy. Using our own photometry and data from 2MASS and the GSC2.2
surveys we demonstrate that the claim by Momany et al. that the CMa overdensity
is entirely due to the Galactic warp is not supported by the existing
observations, once all the available pieces of information are taken into
account. It is shown that the CMa overdensity clearly emerges at a heliocentric
distance of ~ 8 kpc above any overdensity possibly produced by the Galactic
warp.


title:
The X-ray Luminosity - Velocity Dispersion relation in the REFLEX
  Cluster Survey

abstract:
  We present an estimate of the bolometric X-ray luminosity - velocity
dispersion L_x - sigma_v relation measured from a new, large and homogeneous
sample of 171 low redshift, X-ray selected galaxy clusters. The linear fitting
of log(L_x) - log(sigma_v) gives L_x = 10^{32.72 \pm 0.08} sigma^{4.1 \pm
0.3}_v erg s^{-1} h^{-2}_{50}. Furthermore, a study of 54 clusters, for which
the X-ray temperature of the intracluster medium T is available, allows us to
explore two other scaling relations, L_x -T and sigma_v -T. From this sample we
obtain L_x \propto T^{3.1 \pm 0.2} and sigma_v \propto T^{1.00 \pm 0.16}, which
are fully consistent with the above result for the L_x-sigma_v. The slopes of
L_x -T and sigma_v -T are incompatible with the values predicted by
self-similarity (L_x \propto T^{2} \propto \sigma_v^4), thus suggesting the
presence of non-gravitational energy sources heating up the intracluster
medium, in addition to the gravitational collapse, in the early stages of
cluster formation. On the other hand, the result on log(L_x) - log(sigma_v)
supports the self-similar model.


title: Spot-like Structures of Neutron Star Surface Magnetic Fields

abstract:
  There is growing evidence, based on both X-ray and radio observations of
isolated neutron stars, that besides the large--scale (dipolar) magnetic field,
which determines the pulsar spin--down behaviour, small--scale poloidal field
components are present, which have surface strengths one to two orders of
magnitude larger than the dipolar component. We argue in this paper that the
Hall--effect can be an efficient process in producing such small--scale field
structures just above the neutron star surface. It is shown that due to a
Hall--drift induced instability, poloidal magnetic field structures can be
generated from strong subsurface toroidal fields, which are the result of
either a dynamo or a thermoelectric instability acting at early times of a
neutron star's life. The geometrical structure of these small--scale surface
anomalies of the magnetic field resembles that of some types of
``star--spots''. The magnetic field strength and the length--scales are
comparable with values that can be derived from various observations.


title:
The Energy Density of the Quaternionic Field as Dark Energy in the
  Universe

abstract:
  In this article we describe a model of the universe consisting of a mixture
of the ordinary matter and a so-called cosmic quaternionic field. The basic
idea here consists in an attempt to interpret $\Lambda$ as the energy density
of the quaternionic field whose source is any form of energy including the
proper energy density of this field. We set the energy density of this field to
$\Lambda$ and show that the ratio of ordinary dark matter energy density
assigned to $\Lambda$ is constant during the cosmic evolution. We investigate
the interaction of the quaternionic field with the ordinary dark matter and
show that this field exerts a force on the moving dark matter which might
possible create the dark matter in the early universe. Such determined
$\Lambda$ fulfils the requirements asked from the dark energy. In this model of
the universe, the cosmical constant, the fine-tuning and the age problems might
be solved. Finally, we sketch the evolution of the universe with the cosmic
quaternionic field and show that the energy density of the cosmic quaternionic
field might be a possible candidate for the dark energy.


title: Quasar host galaxy star formation activity from multicolour data

abstract:
  We investigate multicolour imaging data of a complete sample of 19 low
redshift (z<0.2) quasar host galaxies. The sample was imaged in four optical
(BVRi) and three near-infrared bands (JHK_s). Galaxy types, structural
parameters and robust host galaxy luminosities are extracted for all bands by
means of two-dimensional deblending of galaxy and nucleus. For the disc
dominated fraction of host galaxies (Sa and later) the optical and
optical-to-NIR colours agree well with the average colours of inactive galaxies
of same type. The bulge dominated galaxies (E/S0) on the other hand appear a
significant 0.35 mag bluer in (V-K) than their inactive counterparts, being as
blue as the discs in the sample. This trend is confirmed by fitting population
synthesis models to the extracted broad band SEDs: the stellar population age
of the bulge dominated hosts lies around a few Gyr, much younger than expected
for old evolved ellipticals. Comparison to other studies suggests a strong
trend for stellar age in elliptical host galaxies with luminosity.
Intermediately luminous elliptical hosts have comparably young populations,
either intrinsically or from an enhanced star formation rate potentially due to
interaction, the most luminous and massive ellipticals on the contrary show old
populations. The correspondence between the nuclear activity and the blue
colours suggests a connection between galaxy interaction, induced star
formation and the triggering of nuclear activity. However, the existence of
very symmetric and undisturbed disks and elliptical host galaxies emphasised
that other mechanisms like minor merging or gas accretion must exist.


title: Modeling Molecular-Line Emission from Circumstellar Disks

abstract:
  Molecular lines hold valuable information on the physical and chemical
composition of disks around young stars, the likely progenitors of planetary
systems. This invited contribution discusses techniques to calculate the
molecular emission (and absorption) line spectrum based on models for the
physical and chemical structure of protoplanetary disks. Four examples of
recent research illutrate these techniques in practice: matching resolved
molecular-line emission from the disk around LkCa15 with theoertical models for
the chemistry; evaluating the two-dimensional transfer of ultraviolet radiation
into the disk, and the effect on the HCN/CN ratio; far-infrared CO line
emission from a superheated disk surface layer; and inward motions in the disk
around L1489 IRS.


title:
Chemistry and kinematics of the pre-stellar core L1544: Constraints from
  H2D+

abstract:
  This paper explores the sensitivity of line profiles of H2D+, HCO+ and N2H+,
observed towards the center of L1544, to various kinematic and chemical
parameters. The total width of the H2D+ line can be matched by a static model
and by models invoking ambipolar diffusion and gravitational collapse. The
derived turbulent line width is b=0.15 km/s for the static case and <~ 0.05
km/s for the collapse case. However, line profiles of HC18O+ and N2H+ rule out
the static solution. The double-peaked H2D+ line shape requires either infall
speeds in the center that are much higher than predicted by ambipolar diffusion
models, or a shell-type distribution of H2D+, as is the case for HCO+ and N2H+.
At an offset of ~20 arcsec from the dust peak, the H2D+ abundance drops by a
factor of ~5.


title: FeII/MgII, [Fe/Mg] Ratios and High-z Quasars

abstract:
  It has been suggested in the literature that the (Fe/alpha) abundance ratio
may be used as a chronometer, due to a delay in this ratio reaching its solar
value as predicted by galactic chemical evolution models. Using grids of
photoionization models along a sequence of the (Fe/Mg) abundance ratio vs.\
metallicity with time in a giant elliptical starburst scenario, we investigate
the relationship between the (Fe/Mg) abundance ratio and the FeII/MgII emission
line flux ratio under the assumption that these lines originate in photoionized
clouds within the broad emission line regions of quasars.


title: A sample of radio-loud QSOs at redshift ~ 4

abstract:
  We obtained spectra of 60 red, starlike objects (E< 18.8) identified with
FIRST radio sources, S_{1.4GHz} > 1 mJy. Eight are QSOs with redshift z>
3.6.Combined with our pilot search (Benn et al 2002), our sample of 121
candidates yields a total of 18 z > 3.6 QSOs (10 of these with z > 4.0). 8% of
candidates with S_{1.4GHz}< 10 mJy, and 37% of candidates with S_{1.4GHz}> 10
mJy are QSOs with z > 3.6. The surface density of E < 18.8, S_{1.4GHz} > 1mJy,
z> 4 QSOs is 0.003 deg^{-2}. This is currently the only well-defined sample of
radio-loud QSOs at z ~ 4 selected independently of radio spectral index. The
QSOs are highly luminous in the optical (8 have M_B < -28, q_0 = 0.5, H_0 = 50
kms^{-1}Mpc^{-1}). The SEDs are as varied as those seen in optical searches for
high-redshift QSOs, but the fraction of objects with weak (strongly
self-absorbed) Ly alpha emission is marginally higher (3 out of 18) than for
high-redshift QSOs from SDSS (5 out of 96).


title: Are rotating strange quark stars good sources of gravitational waves?

abstract:
  We study the viscosity driven (Jacobi-like) bar mode instability of rapidly
rotating strange stars in general relativity. A triaxial, "bar shaped" compact
star could be an efficient source of continuous wave gravitational radiation in
the frequency range of the forthcoming interferometric detectors. We locate the
secular instability point along several constant baryon mass sequences of
uniformly rotating strange stars described by the MIT bag model. Contrary to
neutron stars, strange stars with T/|W| (the ratio of the rotational kinetic
energy to the absolute value of the gravitational potential energy) much lower
than the corresponding value for the mass-shed limit can be secularly unstable
to bar mode formation if shear viscosity is high enough to damp out any
deviation from uniform rotation. The instability develops for a broad range of
gravitational masses and rotational frequencies of strange quark stars. It
imposes strong constraints on the lower limit of the frequency at the innermost
stable circular orbit around rapidly rotating strange stars. The above results
are robust for all linear self-bound equations of state assuming the growth
time of the instability is faster than the damping timescale. We discuss
astrophysical scenarios where triaxial instabilities (r-mode and viscosity
driven instability) could be relevant in strange stars described by the
standard MIT bag model of normal quark matter. Taking into account actual
values of viscosities in strange quark matter and neglecting the magnetic field
we show that Jacobi-like instability cannot develop in any astrophysicaly
interesting temperature windows. The main result is that strange quark stars
described by the MIT bag model can be accelerated to very high frequency in Low
Mass X-ray binaries if the strange quark mass is ~ 200 MeV or higher.


title: The Universe behind the Southern Milky Way

abstract:
  A first analysis of a deep blind HI survey covering the southern Zone of
Avoidance plus an extension towards the north (196 < l < 52 deg) obtained with
the Multibeam receiver at the 64m Parkes telescope reveals slightly over a
thousand galaxies within the latitude completeness limit of |b| < 5deg. The
characteristics and the uncovered large-scale structures of this survey are
described, in particular the prominence of the Norma Supercluster, the possible
cluster around PKS 1343-601 (both in the Great Attractor region), as well as
the Local Void and the clustering in the Puppis region. In this blind HI
survey, HIZOA J0836-43, one of the most massive spiral galaxies known to date
was discovered (M(HI) = 7.3 10^10 Msun M(tot) = 1.1 10^12 Msun; Ho = 75
km/s/Mpc). Although of similar mass as Malin 1-like objects, this galaxy does
not share their typical low-surface brightness properties but seems an
exceptionally massive but normal, high-surface brightness, star-forming galaxy.


title: A CFH12K Survey of Red Giant Stars in the M81 Group

abstract:
  We present the preliminary results of a wide-field photometric survey of
individual red giant branch (RGB) and asymptotic giant branch (AGB) stars in
the M81 group, performed with the CFH12K mosaic camera of the CFHT. We use deep
VI images of 0.65 sq. deg. of sky to map out the two-dimensional distribution
of intragroup stars and to search for stars associated with the many HI tidal
tails in the group. We place an upper limit on the presence of metal-poor RGB
stars in a field located 50-80 kpc from M81, and derive an `intragroup'
fraction of <2%. In a field sampling the M81-NGC3077 HI tidal tail, we find
blue stars associated with some of the tidal features, including 2 clumps which
we tentatively describe as tidal dwarf candidates. These objects are ~1 kpc in
size, and, based on their color-magnitude diagrams, have formed stars as
recently as ~30-70 Myr ago, long after the group's most recent interactions.


title: Cosmo MSW effect for mass varying neutrinos

abstract:
  We consider neutrinos with varying masses which arise in scenarios relating
neutrino masses to the dark energy density in the universe. We point out that
the neutrino mass variation can lead to level crossing and thus a cosmo MSW
effect, having dramatic consequences for the flavor ratio of astrophysical
neutrinos.


title:
The impact of shocks on the chemistry of molecular clouds: high
  resolution images of chemical differentiation along the NGC1333-IRAS2A
  outflow

abstract:
  This paper presents a detailed study of the chemistry in the outflow
associated with the low-mass protostar NGC1333-IRAS2A down to 3" (650 AU)
scales. Millimeter-wavelength aperture-synthesis observations from the OVRO and
BIMA interferometers and (sub)millimeter single-dish observations from the
Onsala 20m telescope and CSO are presented. The interaction of the highly
collimated protostellar outflow with a molecular condensation ~15000 AU from
the central protostar is clearly traced by molecular species such as HCN, SiO,
SO, CS, and CH3OH. Especially SiO traces a narrow high velocity component at
the interface between the outflow and the molecular condensation.
Multi-transition single-dish observations are used to distinguish the chemistry
of the shock from that of the molecular condensation and to address the
physical conditions therein. Statistical equilibrium calculations reveal
temperatures of 20 and 70 K for the quiescent and shocked components,
respectively, and densities near 10^6 cm^{-3}. Significant abundance
enhancements of two to four orders of magnitude are found in the shocked region
for molecules such as CH3OH, SiO and the sulfur-bearing molecules. HCO+ is seen
only in the aftermath of the shock consistent with models where it is destroyed
through release of H2O from grain mantles in the shock. N2H+ shows narrow
lines, not affected by the outflow but rather probing the ambient cloud.
Differences in abundances of HCN, H2CO and CS are seen between different
outflow regions and are suggested to be related to differences in the atomic
carbon abundance. Compared to the warm inner parts of protostellar envelopes,
higher abundances of in particular CH3OH and SiO are found in the outflows,
which may be related to density differences between the regions.


title:
Optical polarization observations of NGC 6231: evidence for a past SN
  fingerprint

abstract:
  We present the first linear multicolor polarization observations for a sample
of 35 stars in the direction of the Galactic cluster NGC 6231. We have found a
complex pattern in the angles of the polarimetric vectors. Near the core of
this cluster the structure shows a semi-circular pattern that we have
interpreted as a re-orientation of the dust particles, showing the morphology
of the magnetic field. We propose that a supernova event has occurred some time
ago and produced a shock on the local ISM. We discuss in this paper independent
confirmations othis event, both from the studies on the diffuse interstellar
absorptions Crawford (2001) and the results of the pre-main sequence stars
(PMS) given by Sung et al. (1998). We also show that a supernova is supported
by the evolutive status of the cluster.


title: Wave Modes in Collapsar Jets

abstract:
  Collapsars may be a source for the long Gamma Ray Bursts (GRBs) in the BATSE
catalog. Collapsars may radiate gamma rays anisotropically by beamed jet
emission close to the observer's line of sight. These jets must penetrate the
radiation-dominated medium of their collapsar progenitor and break through its
atmosphere in order to produce a GRB. We present a study of previously
published, axisymmetric, collapsar jet simulations. Here we use the linearized,
relativistic fluid equations to find the Kelvin-Helmholtz modes that are
triggered by recollimation shocks within the jet. The modes will grow as they
propagate with the jet. These are of interest since the light curves of GRBs
show evidence of a variable flow from the GRB engine. We also evaluate effects
of grid scaling in the numerical simulation and show that short wavelength
modes are suppressed by grid scaling before the jet breaks out of the Helium
shell.


title:
The Wendelstein Calar Alto Pixellensing Project(WeCAPP): First MACHO
  Candidates

abstract:
  We report the detection of the first 2 microlensing candidates from the
Wendelstein Calar Alto Pixellensing Project (WeCAPP). Both are detected with a
high signal-to-noise-ratio and were filtered out from 4.5 mill. pixel light
curves using a variety of selection criteria. Here we only consider
well-sampled events with timescales of 1 d < t_fwhm < 20 d, high amplitude, and
low chi^2 of the microlensing fit. The two-color photometry (R,I) shows that
the events are achromatic and that giant stars with colors of (R-I) ~ 1.1 mag
in the bulge of M31 have been lensed. The magnification factors are 64 and 10
which are obtained for typical giant luminosities of M_I = -2.5 mag. Both
lensing events lasted for only a few days (t_fwhm^GL1 = 1.7 d and t_fwhm^GL2 =
5.4 d). The event GL1 is likely identical with PA-00-S3 reported by the
POINT-AGAPE project. Our calculations favor in both cases the possibility that
MACHOs in the halo of M31 caused the lensing events. The most probable masses,
0.08 M_sun for GL1 and 0.02 M_sun for GL2, are in the range of the brown dwarf
limit of hydrogen burning. Solar mass objects are a factor of two less likely.


title: Temporal Bias in the Clustering of Massive Cosmological Objects

abstract:
  It is a well-established fact that massive cosmological objects exhibit a
``geometrical bias'' that boosts their spatial correlations with respect to the
underlying mass distribution. Although this geometrical bias is a simple
function of mass, this is only half of the story. We show using numerical
simulations that objects that are in the midst of accreting material also
exhibit a ``temporal bias,'' which further boosts their clustering far above
geometrical bias levels. These results may help to resolve a discrepancy
between spectroscopic and clustering mass estimates of Lyman Break Galaxies, a
population of high-redshift galaxies that are caught in the act of forming
large numbers of new stars.


title: Precession in the inner jet of 3C 345

abstract:
  VLBI observations have shown that the parsec-jet of 3C 345 is formed by
several components, ejected from the core with superluminal velocities and
travelling along bent trajectories on the plane of the sky. We interpret the
differences in velocity and position angle among the different features at
formation time as the result of parsec-scale precession of the relativistic jet
and calculate the aperture angle of the precession cone, the angle between the
cone axis and the line of sight and the Lorentz factor associated with the jet
bulk motion. We assumed a precession period of 10.1 yr, which is one of the
B-band light curve long-term periods reported in the literature. We propose
that boosting of the underlying jet emission, which is time-dependent due to
precession, is responsible for this long-term optical variability. Jet
precession with periods of several years can be produced in super-massive black
hole binary systems, when the secondary black hole is in an orbit non-coplanar
with the primary accretion disk, inducing torques in the inner parts of the
disk. Assuming that this mechanism is responsible for the jet precession in 3C
345, we estimate upper and lower limits for the masses of the two black holes,
as well as their mean separation. We found a correlation between the formation
of jet components and the occurrence of strong optical flares, as well as a
very strong anti-correlation between the intensity of these flares and the time
required for the components to reach the maximum flux density at radio
frequencies.


title: A Chandra observation of the old open cluster M67

abstract:
  We present the results of a 47-ks Chandra-ACIS observation of the old open
cluster M67. We detected 25 proper-motion cluster members (including ten new
sources) and 12 sources (all new) that we suspect to be members from their
locations close to the main sequence (1 < B-V < 1.7). Of the detected members,
23 are binaries. Among the new sources that are members and probable members
are four spectroscopic binaries with P_orb < 12 d, two contact binaries and two
periodic photometric variables with P_ph < 8.4 d. Their X-rays are likely the
result of coronal activity enhanced by tidally locked rapid rotation. The
X-rays of the new source S997, a blue straggler in a wide eccentric orbit, are
puzzling. Spectral fits show that the X-rays of the brightest sources S1063 (a
binary with a sub-subgiant), S1082 (a triple blue straggler with a close
binary) and S1040 (a circular binary of a giant and a cool white dwarf), are
consistent with coronal emission. We detected a new bright source that must
have brightened at least about ten times since the time of the ROSAT
observations. It is not clear whether its faint blue optical counterpart
belongs to M67. We discuss the possibility that this source is a low-mass X-ray
binary in quiescence, which would be the first of its kind in an open cluster.
In addition to cluster members, we detected about 100 background sources, many
of which we identify with faint objects in the ESO Imaging Survey.


title: Spatially Resolved Circumnuclear Dust in Centaurus A

abstract:
  In this paper we present results from our exploratory mid-IR study of
Centaurus A circumnuclear environment using high-angular resolution imaging at
the Magellan 6.5m telescope with the MIRAC/BLINC camera. We detected emission
from a compact region surrounding the nuclear source, and obtained photometry
at 8.8 microns and in the N band. Our analysis suggests that the nuclear region
is resolved with a size of approximately 3 pc. The mid-IR emission from this
region is likely associated with cool dust with an estimated temperature of
\~160 K, surrounding the central ``hidden'' AGN. We discuss the characteristics
of this emission in relation to other mid-IR observations and the implications
on models of dust formation in AGNs.


title:
Expected Changes of Supernovae with Redshift due to Evolution of their
  Progenitors

abstract:
  We have analyzed the influence of the stellar populations, from which SN
progenitors come from, on the observational outcome, including the metal free
Pop. III. We use our models to study the evolution of the progenitor, the
subsequent explosion and the light curves.
  For Type Ia, the variation of the main sequence mass of the progenitor of the
exploding WD, produces an offset in the maximum-decline relation of 0.2 mag.
This effect is critical for the use of high redshift Type Ia SNe as
cosmological standard candles. In contrast, the metallicity does not change the
above relation (at maximum, Delta M_V < 0.06 mag).
  For Type II, we find a dependence of the light curve properties with both,
main sequence mass and metallicity of the progenitor, and we identify a rather
homogeneous subclass, {\it Extreme} II-P, that may be used as a quasi-standard
candle. Note that, although not as good as Type Ia for distance determinations,
Type II are expected to occur since the first stars were formed.


title: Simulation of Soft X-ray Emission Lines from the Missing Baryons

abstract:
  We study the soft X-ray emission (0.1 - 1 keV) from the Warm-Hot
Intergalactic Medium (WHIM) in a hydrodynamic simulation of a Cold Dark Matter
universe. Our main goal is to investigate how such emission can be explored
with a combination of imaging and spectroscopy, and to motivate future X-ray
missions. We first present high resolution images of the X-ray emission in
several energy bands, in which emission from different ion species dominates.
We pick three different areas to study the high resolution spectra of X-rays
from the warm-hot IGM: (a) a galaxy group; (b) a filament and (c) an
underluminous region. By taking into account the background X-ray emission from
AGNs and foreground emission from the Galaxy, we compute composite X-ray
spectra of the selected regions. We briefly investigate angular clustering of
the soft-X-ray emission, finding a strong signal. Most interestingly, the
combination of high spectral resolution and angular information allows us to
map the emission from the WHIM in 3 dimensions. We cross-correlate the
positions of galaxies in the simulation with this redshift map of emission and
detect the presence of six different ion species (Ne IX, Fe XVII, O VII, O
VIII, N VII, C VI) in the large-scale structure traced by the galaxies. Finally
we show how such emission can be detected and studied with future X-ray
satellites, with particular attention to a proposed mission, the Missing Baryon
Explorer, or MBE. We present simulated observations of the WHIM gas with MBE.


title:
Non-thermal hard X-ray emission in galaxy clusters observed with the
  BeppoSAX PDS

abstract:
  We study the X-ray emission in a sample of galaxy clusters using the BeppoSAX
PDS instrument in the 20 -- 80 keV energy band. The non-thermal hard X-ray
cluster emission (HXR) is detected at a 2 sigma level in 50% of the
non-significantly AGN-contaminated clusters: A2142, A2199, A2256, A3376, Coma,
Ophiuchus and Virgo. The data are consistent with a scenario whereby relaxed
clusters have no hard X-ray component of non-thermal origin, whereas merger
clusters do, with a 20-80 keV luminosity of 10^(43-44) erg/s. The co-added
spectrum of the above clusters indicates a power-law spectrum for the HXR with
a photon index of 2.8+0.3-0.4 in the 12-115 keV band, and we find indication
that it has extended distribution. These indications argue against significant
contamination from obscured AGN, which have harder spectra and centrally
concentrated distribution. These results are supportive of the assumption of
the merger shock acceleration of electrons in clusters. Assuming that the
Cosmic Microwave Background photons experience Inverse Compton scattering from
the merger-accelerated relativistic electrons, and thus produce the observed
HXR, the measured hard X-ray slope corresponds to a differential momentum
spectra of the relativistic electrons with a slope of mu = 3.8-5.0. The
observed slope of HXR is also consistent with that predicted by the non-thermal
bremsstrahlung, which thus cannot be ruled by the fit to the current data, even
though this model requires an extreme, untenable cluster energetics. Assuming
centrally concentrated distribution of HXR, the data requires a harder slope
for the HXR spectrum, which is consistent with secondary electron models, but
this model yields a worse fit to the PDS data and thus seems to be disfavored
over the primary electron Inverse Compton model.


title: The Distribution of Maximum Relative Torques in Disk Galaxies

abstract:
  The maximum ratio of the tangential force to the mean background radial force
is a useful quantitative measure of the strength of nonaxisymmetric
perturbations in disk galaxies. Here we consider the distribution of this
ratio, called Qg, for a statistically well-defined sample of 180 spiral
galaxies from the Ohio State University Bright Galaxy Survey and the Two Micron
All-Sky Survey. Qg is derived from gravitational potentials inferred from
near-infrared images under the assumptions of a constant mass-to-light ratio
and an exponential vertical density law. In order to derive the most reliable
maximum relative torques, orientation parameters based on blue-light isophotes
are used to deproject the galaxies, and the more spherical shapes of bulges are
taken into account using two-dimensional decompositions which allow for
analytical fits to bulges, disks, and bars. Also, vertical scaleheights hz are
derived by scaling the radial scalelengths hR from the two-dimensional
decompositions allowing for the type dependence of hR/hz indicated by optical
and near-infrared studies of edge-on spiral galaxies. The impact of dark matter
is assessed using a "universal rotation curve" parametrization, and is found to
be relatively insignificant for our sample. In agreement with a previous study
by Block et al. (2002), the distribution of maximum relative gravitational
torques is asymmetric towards large values and shows a deficiency of low Qg
galaxies. However, due to the above refinements, our distribution shows more
low Qg galaxies than Block et al. We also find a significant type-dependence in
maximum relative gravitational torques, in the sense that Qg is lower on
average in early-type spirals compared to late-type spirals.


title: HI Study of Southern Galactic Supernova Remnants

abstract:
  We briefly summarize the survey of HI 21 cm emission lines to search for
shocked atomic gas associated with Galactic supernova remnants (SNRs) in the
southern sky. For G347.3-0.5, we discuss the distance to the SNR and the
implications of the HI results.