title: Deep HST Imaging of Sextans A. II. Cepheids and Distance

abstract:
  We have identified 82 short-period variable stars in Sextans A from deep
WFPC2 observations. All of the periodic variables appear to be short-period
Cepheids, with periods as small as 0.8 days for fundamental-mode Cepheids and
0.5 days for first-overtone Cepheids. These objects have been used, along with
measurements of the RGB tip and red clump, to measure a true distance modulus
to Sextans A of (m-M)_0 = 25.61 +/- 0.07, corresponding to a distance of d =
1.32 +/- 0.04 Mpc. Comparing distances calculated by these techniques, we find
that short-period Cepheids (P < 2 days) are accurate distance indicators for
objects at or below the metallicity of the SMC. As these objects are quite
numerous in low-metallicity star-forming galaxies, they have the potential for
providing extremely precise distances throughout the Local Group. We have also
compared the relative distances produced by other distance indicators. We
conclude that calibrations of RR Lyraes, the RGB tip, and the red clump are
self-consistent, but that there appears to be a small dependence of long-period
Cepheid distances on metallicity. Finally, we present relative distances of
Sextans A, Leo A, IC 1613, and the Magellanic Clouds.


title:
The Weak Outnumbering the Mighty: Normal Galaxies in Deep Chandra
  Surveys

abstract:
  Chandra is detecting a significant population of normal and starburst
galaxies in extremely deep X-ray exposures. For example, approximately 15% of
the sources arising in the 2 Ms Chandra Deep Field-North survey are fairly
normal galaxies, where "normal" means "Milky Way-type" X-ray emission rather
than simply exhibiting an "optically normal" spectrum. Many of these galaxies
are being detected at large look-back times z=0.1-0.5, allowing the study of
the evolution of X-ray binary populations over significant cosmological
timescales. We are also detecting individual off-nuclear ultraluminous X-ray
sources (e.g., X-ray binaries), providing the first direct constraints on the
prevalence of lower-mass black holes at significantly earlier times. The X-ray
emission from such "normal" galaxies may also be a useful star-formation rate
indicator, based on radio/X-ray cross-identifications. We describe the
contribution of normal galaxies to the populations which make up the X-ray
background and present their directly measured X-ray number counts. We find
that normal and starburst galaxies should dominate the 0.5--2 keV number counts
at X-ray fluxes fainter than 7e-18 erg cm^{-2} s^{-1} (thus they will outnumber
the "mighty" AGN). Finally, we look to the future, suggesting that it is
important that the population of X-ray faint normal and starburst galaxies be
well constrained in order to design the next generation of X-ray observatories.


title:
A reduced efficiency of terrestrial planet formation following giant
  planet migration

abstract:
  Substantial orbital migration of massive planets may occur in most extrasolar
planetary systems. Since migration is likely to occur after a significant
fraction of the dust has been locked up into planetesimals, ubiquitous
migration could reduce the probability of forming terrestrial planets at radii
of the order of 1 au. Using a simple time dependent model for the evolution of
gas and solids in the disk, I show that replenishment of solid material in the
inner disk, following the inward passage of a giant planet, is generally
inefficient. Unless the timescale for diffusion of dust is much shorter than
the viscous timescale, or planetesimal formation is surprisingly slow, the
surface density of planetesimals at 1 au will typically be depleted by one to
two orders of magnitude following giant planet migration. Conceivably,
terrestrial planets may exist only in a modest fraction of systems where a
single generation of massive planets formed and did not migrate significantly.


title: Cosmic vacuum and large-scale perturbations in the concordant model

abstract:
  The evolution of cosmological large-scale perturbations is described in terms
of the concordant model based on the recent discovery of cosmic vacuum. It is
demonstrated that the process is robustly controlled by a few epoch-independent
physical parameters. The parameters guarantee that the initially weak
perturbations become nonlinear before (but near) the termination of
gravitational instability by cosmic vacuum. No fine tuning for the perturbation
amplitude is needed.


title: Ground level muons in coincidence with the solar flare of April 15, 2001

abstract:
  The counting rate of single muon tracks from the Project GRAND proportional
wire chamber array is examined during the Ground Level Event (GLE) of April 15,
2001. The GLE was seen by neutron monitor stations shortly after the time of
the solar X-ray flare. GRAND's single muon data are presented and compared with
neutron monitor data from Climax, Newark, and Oulu. The single muon data have
mean primary hadron energies higher than those of these neutron monitor
stations and so contain information about higher energy hadrons. For the single
muon data for Project GRAND, the GLE is detected at a statistical significance
of 6.1-sigma.


title: A Supernova Remnant Collision with a Stellar Wind

abstract:
  Numerical simulations of the interaction between supernova ejecta and a
stellar wind are presented. We follow the temporal evolution of the shock
fronts that are formed through such an interaction and determine the
velocities, temperatures and densities. We model the X-ray emission from the
SNR-stellar wind collision region and we compare it with recent results from
X-ray observations carried out with the Chandra satellite of the SMC supernova
remnant SNR 0057-7226 which could be interacting with the wind of the
Wolf-Rayet system HD 5980. The simulations predict the presence of shell-like
regions of enhanced X-ray emission which are consistent with the presence of
X-ray emitting arcs in the Chandra image. Also the observed X-ray luminosity is
comparable to the X-ray luminosities we obtain from the simulations for a
supernova with an initial energy in the (1-5)E50 erg range.


title:
On the Eccentricity Distribution of Coalescing Black Hole Binaries
  Driven by the Kozai Mechanism in Globular Clusters

abstract:
  In a globular cluster, hierarchical triple black hole systems can be produced
through binary-binary interaction. It has been proposed recently that the Kozai
mechanism could drive the inner binary of the triple system to merge before it
is interrupted by interactions with other field stars. We investigate
qualitatively and numerically the evolution of the eccentricities in these
binaries under gravitational radiation (GR) reaction. We predict that ~ 30 % of
the systems will possess eccentricities >0.1 when their emitted gravitational
waves pass through 10 Hz frequency. The implications for gravitational wave
detection, especially the relevance to data analyses for broad-band
laser-interferometer gravitational wave detectors, are discussed.


title:
The interaction of a giant planet with a disc with MHD turbulence I: The
  initial turbulent disc models

abstract:
  This is the first of a series of papers aimed at developing and interpreting
simulations of protoplanets interacting with turbulent accretion discs. Here we
study the disc models prior to the introduction of a protoplanet.We study
models in which a Keplerian domain is unstable to the magnetorotational
instability (MRI). Various models with B-fields having zero net flux are
considered.We relate the properties of the models to classical viscous disc
theory.All models attain a turbulent state with volume averaged stress
parameter alpha ~ 0.005. At any particular time the vertically and azimuthally
averaged value exhibited large fluctuations in radius. Time averaging over
periods exceeding 3 orbital periods at the outer boundary of the disc resulted
in a smoother quantity with radial variations within a factor of two or so. The
vertically and azimuthally averaged radial velocity showed much larger spatial
and temporal fluctuations, requiring additional time averaging for 7-8 orbital
periods at the outer boundary to limit them. Comparison with the value derived
from the averaged stress using viscous disc theory yielded schematic agreement
for feasible averaging times but with some indication that the effects of
residual fluctuations remained. The behaviour described above must be borne in
mind when considering laminar disc simulations with anomalous Navier--Stokes
viscosity. This is because the operation of a viscosity as in classical viscous
disc theory with anomalous viscosity coefficient cannot apply to a turbulent
disc undergoing rapid changes due to external perturbation. The classical
theory can only be used to describe the time averaged behaviour of the parts of
the disc that are in a statistically steady condition for long enough for
appropriate averaging to be carried out.


title:
UV-Optical Pixel Maps of Face-On Spiral Galaxies -- Clues for Dynamics
  and Star Formation Histories

abstract:
  UV and optical images of the face-on spiral galaxies NGC 6753 and NGC 6782
reveal regions of strong on-going star formation that are associated with
structures traced by the old stellar populations. We make NUV--(NUV-I) pixel
color-magnitude diagrams (pCMDs) that reveal plumes of pixels with strongly
varying NUV surface brightness and nearly constant I surface brightness. The
plumes correspond to sharply bounded radial ranges, with (NUV-I) at a given NUV
surface brightness being bluer at larger radii. The plumes are parallel to the
reddening vector and simple model mixtures of young and old populations, thus
neither reddening nor the fraction of the young population can produce the
observed separation between the plumes. The images, radial surface-brightness,
and color plots indicate that the separate plumes are caused by sharp declines
in the surface densities of the old populations at radii corresponding to disk
resonances. The maximum surface brightness of the NUV light remains nearly
constant with radius, while the maximum I surface brightness declines sharply
with radius. An MUV image of NGC 6782 shows emission from the nuclear ring. The
distribution of points in an (MUV-NUV) vs. (NUV-I) pixel color-color diagram is
broadly consistent with the simple mixture model, but shows a residual trend
that the bluest pixels in (MUV-NUV) are the reddest pixels in (NUV-I). This may
be due to a combination of red continuum from late-type supergiants and [SIII]
emission lines associated with HII regions in active star-forming regions. We
have shown that pixel mapping is a powerful tool for studying the distribution
and strength of on-going star formation in galaxies. Deep, multi-color imaging
can extend this to studies of extinction, and the ages and metallicities of
composite stellar populations in nearby galaxies.


title:
The interaction of a giant planet with a disc with MHD turbulence II:
  The interaction of the planet with the disc

abstract:
  We present a global MHD simulation of a turbulent accretion disc interacting
with a protoplanet of 5 Jupiter masses. The disc model had H/r=0.1,and a value
of the Shakura & Sunyaev alpha ~ 0.005. The protoplanet opened a gap in the
disc, with the interaction leading to inward migration on the expected time
scale. Spiral waves were launched by the protoplanet and although they were
diffused and dissipated through interaction with the turbulence, they produced
an outward angular momentum flow which compensated for a reduced flux
associated with the turbulence, so maintaining the gap. When compared with
laminar disc models with the same estimated alpha, the gap was found to be
deeper and wider indicating that the turbulent disc behaved as if it possessed
a smaller alpha. This may arise for two reasons. First, the turbulence does not
provide a source of constantly acting friction in the near vicinity of the
planet that leads to steady mass flow into the gap region. Instead the
turbulence is characterised by large fluctuations in the radial velocity, and
time averaging over significant time scales is required to recover the
underlying mass flow through the disc. Near the planet the disc material
experiences high amplitude perturbations on time scales that are short relative
to the time scale required for averaging. The disc response is thus likely to
be altered relative to a Navier--Stokes model. Second, the simulation indicates
that an ordered magnetic connection between the inner and outer disc can occur
enabling angular momentum to flow out across the gap, helping to maintain it
independently of the protoplanet's tide. This type of effect may assist gap
formation for smaller mass protoplanets which otherwise would not be able to
maintain them.


title:
Metal Absorption Lines as Probes of the Intergalactic Medium Prior to
  the Reionization Epoch

abstract:
  Winds from star-forming galaxies provide the most promising explanation for
the enrichment of the intergalactic medium with heavy elements. Theoretical and
observational arguments indicate that the pollution may have occurred at z > 6;
however, direct observational tests of such a scenario are needed. We model
starburst winds in the high-redshift universe and find that the fraction of
space filled by enriched material varies strongly with the assumed star
formation efficiency f_* and the fraction of supernova energy powering each
wind, f_esc. We show that metals carried by these winds can be seen in
absorption against bright background sources, such as quasars or gamma-ray
bursts, in narrow lines with characteristic equivalent widths ~0.5 < W < 5
Angstrom. We argue that a substantial fraction of the metals in high-redshift
winds are likely to reside in low ionization states (CII, OI, SiII, and FeII),
but higher ionization states (CIV and SiIV) could also provide useful probes of
the winds. The number of such lines can constrain both f_* and f_esc.
Statistics of metal absorption lines can also be used to identify whether
molecular hydrogen is an efficient coolant in the early universe and to study
the initial mass function of stars at high redshifts.


title:
Seven problems related to the determination of the primordial helium
  abundance

abstract:
  Recent advances on the quest to determine the primordial or pregalactic
helium abundance, Yp, are reviewed. There are seven problems affecting the He/H
abundance determinations of H II regions that are briefly discussed: the
underlying absorption lines in the observed spectra, the ionization,
temperature, and density structures of each object, the collisional
contribution to the intensity of the He I and H I lines, the optical thickness
of the He I lines, and the extrapolation to derive Yp based on the Y and O/H
values.


title:
First full evolutionary computation of the He-flash induced mixing in
  Population II stars

abstract:
  The core helium-flash in low-mass stars with extreme mass loss occurs after
the tip of the RGB, when the H-rich envelope is very thin. The low efficiency
of the H-shell source enables the He-flash driven convective zone to penetrate
H-rich layers and trigger a thermonuclear runaway, resulting in a subsequent
surface enrichment with He and C. In this work we present the first full
computations of Population II low-mass stellar models through this phase.
Models experiencing this dredge-up event are significantly hotter than their
counterparts with H-rich envelopes, which makes them promising candidates for
explaining the existence of stars observed beyond the canonical blue end of the
horizontal branch ("blue hook stars"). Moreover, this temperature difference
could explain the observed gap in M_V between extreme blue horizontal-branch
and blue hook stars. A first comparison with spectroscopic observations of blue
hook stars in the globular cluster omega Cen is also presented.


title:
Gravitational lens time delays for distant supernovae: break the
  degeneracy between radial mass profiles and the Hubble constant

abstract:
  An attempt to measure the Hubble constant with gravitational lens time delays
is often limited by the strong degeneracy between radial mass profiles of lens
galaxies and the Hubble constant. We show that strong gravitational lensing of
type Ia supernovae breaks this degeneracy; the standard candle nature of type
Ia supernova luminosity function allows one to measure the magnification factor
directly, and this information is essential to constrain radial mass profiles
and the Hubble constant separately. Our numerical simulation demonstrates that
the Hubble constant can be determined with \sim 5% accuracy from only several
lens events if magnification factors are used as constraints. Therefore,
distant supernova survey is a promising way to measure the global Hubble
constant independently with the local estimates.


title: WIMP direct detection overview

abstract:
  This review on weakly interacting massive particle (WIMP) dark matter direct
detection focuses on experimental approaches and the corresponding physics
basics. The presentation is intended to provide a quick and concise
introduction for non-specialists to this fast evolving topic of astroparticle
physics.


title:
Detached double-lined eclipsing binaries as critical tests of stellar
  evolution : Age and metallicity determinations from the HR diagram

abstract:
  Detached, double-lined spectroscopic binaries which are also eclipsing
provide the most accurate determinations of stellar mass, radius, temperature
and distance-independent luminosity for each of their individual components,
and hence constitute a stringent test of single-star stellar evolution theory.
We compile a large sample of 60 non interacting, well-detached systems mostly
with typical errors smaller than 2% for mass and radius and smaller than 5% for
effective temperature, and compare them with the properties predicted by
stellar evolutionary tracks from a minimization method. To assess the
systematic errors introduced by a given set of tracks, we compare the results
obtained using three widely-used independent sets of tracks, computed with
different physical ingredients (the Geneva, Padova and Granada models). We also
test the hypothesis that the components of these systems are coeval and have
the same metallicity, and compare the derived ages and metallicities with the
ones obtained by fitting a single isochrone to the system. Overall, there is a
good agreement among the different determinations, and we provide a
comprehensive discussion on the sub-sample of systems which either present
problems or have estimated metallicities. Although within the errors the
published tracks can fit most of the systems, a large degeneracy between age
and metallicity remains. The power of the test is thus limited because the
metallicities of most of the systems are unknown.


title:
A database of molecular line data for rotational transitions from
  selected species of astrophysical interest

abstract:
  Molecular line data for the rotational transitions of a number of
astrophysically interesting species have been collected and are made publically
available through the www. These data, including energy levels, statistical
weights, Einstein A-coefficients and collisional rate coefficients, are
essential input for non-LTE molecular radiative transfer programs. A computer
program for performing statistical equilibrium calculations is made publically
available for use as well. This database should form an important tool in
analyzing observations from current and future infrared and (sub)millimetre
telescopes.


title: Single and binary Black Holes and their active environment

abstract:
  In this short review we describe some of the latest endeavours to understand
the activity around Black Holes. First, it has been possible to demonstrate
that a large part of the electromagnetic emission observed can be interpreted
as arising from the jet; this explains at once all spectral features and their
variability. Second we dwell on the concept that merging galaxies naturally
lead to merging Black Holes. Here we emphasize two aspects: a) the torque
exerted by the binary Black Holes carves a torus like distribution out of the
stellar population near to the Black Hole binary; b) We consider the last
stages of the Black Hole binary merger, taking into account the angle between
the spin of the primary Black Hole, and the orbital spin of the second Black
Hole. We show that the loss of orbital angular momentum is very strongly
spin-dependent; for large angles between the two spins the angular momentum
loss is strongly inhibited, allowing spin flip of the primary Black Hole which
preserves a high angular momentum relative to the maximum allowed. This ensures
that both before and after the merger the accretion disk may reach to very
small distances from the central Black Hole, with very high local temperatures
right near the base of the jet: This is especially interesting in the case that
forming the jet requires the formation of an ADAF like ring near the inner edge
of the disk, as suggested by some earlier work. It also may have consequences
for the initial hadronic interactions right near the base of the jet. Finally,
this may also have important implications for the discovery of gravitational
radiation bursts from the merger of black holes; the spin dependence needs to
be taken into account.


title:
Multi-Detector Multi-Component spectral matching and applications for
  CMB data analysis

abstract:
  We present a new method for analyzing multi--detector maps containing
contributions from several components. Our method, based on matching the data
to a model in the spectral domain, permits to estimate jointly the spatial
power spectra of the components and of the noise, as well as the mixing
coefficients. It is of particular relevance for the analysis of
millimeter--wave maps containing a contribution from CMB anisotropies.


title: Sensitive Limits on the Water Abundance in Cold Low Mass Molecular Cores

abstract:
  We present SWAS observations of water vapor in two cold star-less clouds, B68
and Core D in rho Ophiuchus. Sensitive non-detections of the 1(10)-1(01)
transition of o-H2O are reported for each source. Both molecular cores have
been previously examined by detailed observations that have characterized the
physical structure. Using these rather well defined physical properties and a
Monte-Carlo radiation transfer model we have removed one of the largest
uncertainties from the abundance calculation and set the lowest water abundance
limit to date in cold low-mass molecular cores. These limits are < 3 x 10^{-8}
(relative to H2) and < 8 x 10^{-9} in B68 and rho Oph D, respectively. Such low
abundances confirm the general lack of ortho-water vapor in cold (T < 20 K)
cores. Provided that the ortho/para ratio of water is not near zero, these
limits are well below theoretical predictions and appear to support the
suggestion that most of the water in dense low-mass cores is frozen onto the
surfaces of cold dust grains.


title: Chromospheric Dynamics of Betelgeuse from STIS Spectra

abstract:
  We present a high-resolution spectral analysis of Betelgeuse (M2 Iab).
Between 1998 January and 1999 March four spatially resolved raster scans
(http://cfa-www.harvard.edu/cfa/ep/pressrel/alobel0100.html) have been obtained
with the STIS on the Hubble Space Telescope. The near-UV echelle spectra reveal
double-peaked permitted emission lines of neutral and singly ionized metals,
with self-absorbed line cores. We observe reversals in the intensity of both
emission line components when scanning across the UV disk, for four unsaturated
lines of Si I, Fe I, Al II], and Fe II. We model the Si I lam2516 resonance
line with detailed non-LTE radiative transport calculations in spherical
geometry, and constrain the mean velocity structure in the projected aperture
area, for each scan position on the chromospheric disk. We infer the spatial
velocity structure of Betelgeuse's extended chromosphere, which reveals
localized upflows in the western front hemisphere in 1998 September, that
expand further toward the eastern hemisphere in 1999 March. The spatial scans
exhibit simultaneous up- and downflows across the lower chromosphere with mean
velocities of ~2 km/s. We infer non-radial (or non-coherent) mass movements
during certain phases of the stellar variability cycle from these subsonic
flows. We present a discussion of constructing semi-empiric models for the
chromosphere of this cool supergiant, and of its temporal variability.


title:
The Dynamical State of Barnard 68: A Thermally Supported, Pulsating Dark
  Cloud

abstract:
  We report sensitive, high resolution molecular-line observations of the dark
cloud Barnard 68 obtained with the IRAM 30-m telescope. We analyze
spectral-line observations of C18O, CS(2--1), C34S(2--1), and N2H+(1--0) in
order to investigate the kinematics and dynamical state of the cloud. We find
extremely narrow linewidths in the central regions of the cloud. These narrow
lines are consistent with thermally broadened profiles for the measured gas
temperature of 10.5 K. We determine the thermal pressure to be a factor 4 -- 5
times greater than the non-thermal (turbulent) pressure in the central regions
of the cloud, indicating that thermal pressure is the primary source of support
against gravity in this cloud. This confirms the inference of a thermally
supported cloud drawn previously from deep infrared extinction measurements.
The rotational kinetic energy is found to be only a few percent of the
gravitational potential energy, indicating that the contribution of rotation to
the overall stability of the cloud is insignificant. Finally, our observations
show that CS line is optically thick and self-reversed across nearly the entire
projected surface of the cloud. The shapes of the self-reversed profiles are
asymmetric and are found to vary across the cloud in such a manner that the
presence of both inward and outward motions are observed within the cloud.
Moreover, these motions appear to be globally organized in a clear and
systematic alternating spatial pattern which is suggestive of a small
amplitude, non-radial oscillation or pulsation of the outer layers of the cloud
about an equilibrium configuration.


title:
The Millennium Outburst of the Cool Hypergiant Rho Cassiopeiae:
  Spectroscopy and Modeling

abstract:
  Between 2000 June and September an exceptional variability phase occurred in
the peculiar F-type hypergiant Rho Cas, when the V-brightness dimmed by at
least a full magnitude. The star recovered from this deep minimum by 2001
April. It is the third outburst of Rho Cas on record in the last century. We
observe TiO absorption bands in high-resolution optical and near-IR spectra
obtained with the Utrecht Echelle Spectrograph during the summer of 2000. TiO
formation in the outer atmosphere occurred before the deep brightness
minimum.Atmospheric models reveal that the effective temperature decreases by
at least 3000 K, and the TiO shell is driven supersonically with Mdot =~5.4
10^-2 Msun/yr. Strong episodic mass loss and TiO have also been observed during
the outbursts of 1945-47 and 1985-86. An analysis of the exceptional outburst
spectra of 2000-01 is provided, by comparing with high-resolution optical
spectra of the early M-type supergiants Mu Cep (Ia) and Betelgeuse (Iab).
During the outburst, central emission appears above the local continuum level
in the split Na D lines. The outburst spectra indicate the formation of a low-
temperature, optically thick circumstellar gas shell of 3 10^-2 Msun during
\~200 d, caused by dynamic instability of the upper atmosphere of this
pulsating massive supergiant near the Eddington luminosity limit. We present an
equation that correctly predicts the outburst time-scale, whereby the shell
ejection is driven by the release of hydrogen recombination energy. We observe
that the mass-loss rate during the outburst is of the same order of magnitude
as has been proposed for the outbursts of Eta Carinae. The research results in
this paper are described in further detail in Lobel et al. (2003). A spectral
movie sequence of the outburst is available at
http://cfa-www.harvard.edu/~alobel/


title:
Refining Chandra/ACIS Subpixel Event Repositioning Using a Backside
  Illuminated CCD Model

abstract:
  Subpixel event repositioning (SER) techniques have been demonstrated to
significantly improve the already unprecedented spatial resolution of Chandra
X-ray imaging with the Advanced CCD Imaging Spectrometer (ACIS). Chandra CCD
SER techniques are based on the premise that the impact position of events can
be refined, based on the distribution of charge among affected CCD pixels. ACIS
SER models proposed thus far are restricted to corner split (3- and 4-pixel)
events, and assume that such events take place at the split pixel corners. To
improve the event counting statistics, we modified the ACIS SER algorithms to
include 2-pixel split events and single pixel events, using refined estimates
for photon impact locations. Furthermore, simulations that make use of a
high-fidelity backside illuminated (BI) CCD model demonstrate that mean photon
impact positions for split events are energy dependent leading to further
modification of subpixel event locations according to event type and energy,
for BI ACIS devices. Testing on Chandra CCD X-ray observations of the Orion
Nebula Cluster indicates that these modified SER algorithms further improve the
spatial resolution of Chandra/ACIS, to the extent that the spreading in the
spatial distribution of photons is dominated by the High Resolution Mirror
Assembly, rather than by ACIS pixelization.


title:
Shaping Proto-Planetary and Young Planetary Nebulae with Collimated Fast
  Winds

abstract:
  Using two-dimensional hydrodynamical simulations, we investigate the
interaction of a collimated fast wind (CFW) interacting with a spherical
asymptotic giant branch (AGB) wind as the mechanism for shaping proto-planetary
nebulae and young planetary nebulae. In particular, we compare our simulations
to the observations of an evolved PPN with multiple, highly collimated lobes,
CRL 618.


title:
Interchange Method in Compressible Magnetized Couette Flow:
  Magnetorotational and Magnetoconvective Instabilities

abstract:
  We obtain the general forms of the axisymmetric stability criteria in a
magnetized compressible Couette flow using an energy variational principle, the
so--called interchange or Chandrasekhar's method, which we applied successfully
in the incompressible case. This formulation accounts for the simultaneous
presence of gravity, rotation, a toroidal magnetic field, a weak axial magnetic
field, entropy gradients, and density gradients in the initial equilibrium
state. The power of the method lies in its simplicity which allows us to derive
extremely compact and physically clear expressions for the relevant stability
criteria despite the inclusion of so many physical effects. In the
implementation of the method, all the applicable conservation laws are
explicitly taken into account during the variations of a quantity with
dimensions of energy which we call the "free--energy function." In the limits
of plane--parallel atmospheres and homoentropic flows, our formulation easily
recovers the stability criteria for suppression of convective and Parker
instabilities, as well as some related special cases studied over 40 years ago
by Newcomb and Tserkovnikov via laborious variational techniques.


title: On the Origin of Nitrogen in Damped Ly-alpha Systems

abstract:
  Recent measurements of nitrogen and alpha elements in over 20 damped Ly-alpha
systems (DLA) are compared with similar measurements for numerous emission line
objects and stars. It is found that the DLA distribution in the N/alpha-alpha/H
plane is bimodal, where most sample DLAs fall along the N/alpha plateau defined
at low Z by dwarf irregulars, while a small group possesses N/alpha values
roughly 0.7 dex less than those on the plateau at similar alpha/H values. We
demonstrate with chemical evolution models that a top-heavy or truncated IMF
can account for the low N in this second group.


title: Protostellar jets and magnetic diffusion

abstract:
  We investigate the evolution of a disk wind into a collimated jet under the
influence of magnetic diffusivity. Using the ZEUS-3D code in the axisymmetry
option we solve the time-dependent resistive MHD equations for a model setup of
a central star surrounded by an accretion disk. The disk is taken as a
time-independent boundary condition for the mass flow rate and the magnetic
flux distribution. We find that the diffusive jets propagate slower into the
ambient medium, most probably due to the lower mass flow rate in axial
direction. Close to the star we find that a quasi stationary state evolves
after several hundreds (weak diffusion) or thousands (strong diffusion) of disk
rotations. Magnetic diffusivity affects the protostellar jet structure
de-collimating it. We explain these effects in the framework of the Lorentz
force.


title: Chandra Detection of Hotspot and Knots of 3C 303

abstract:
  We report the detection at X-rays of the radio/optical hotspot and knots of
3C 303 from a short (15 ksec) Chandra exposure in 2001 March. The X-ray
morphology is similar to that of the radio/optical emission with peaks in the
X-ray emission found at 5.5''(knot B), 9'' (knot C) and 17'' (hotspot) from the
core of 3C 303. Despite the limited signal-to-noise ratio of the short Chandra
exposure, the X-ray photon spectrum was measured for the hotspot. We construct
the spectral energy distribution (SED) and find that the X-ray flux is well
below the extrapolation of the radio-to-optical continuum, which we interpret
as resulting from the production of X-rays via inverse Compton scattering of
both synchrotron photons (SSC) and cosmic microwave background photons
(EC/CMB). The magnetic field strength, region size, and the maximum energy of
electrons are self-consistently determined for the hotspot to be B ~ 4.3 \mu G,
R ~ 6.5x10^{21} cm, and G_max ~ 1.4x10^7. This implies a magnetic field
strength a factor of ~30 below the equipartition value; B_eq ~ 150 \mu G. The
origin of this large departure from equipartition is still uncertain, but the
discrepancy is reduced if the plasma in the hotspot is moving with mildly
relativistic speeds. Our observation of 3C 303, as well as recent Chandra
detections of large scale jets and hotspots in a number of radio galaxies,
confirm that particles are accelerated very efficiently in radio galaxies.


title:
Fast Transition between High-soft and Low-soft States in GRS 1915+105:
  Evidence for a Critically Viscous Accretion Flow

abstract:
  We present the results of a detailed analysis of RXTE observations of class
$\omega$ which show an unusual state transition between high-soft and low-soft
states in the microquasar GRS 1915+105. Out of about 600 pointed RXTE
observations, the source was found to exhibit such state transition only on 16
occasions. An examination of the RXTE/ASM data in conjunction with the pointed
observations reveals that these events appeared as a series of quasi-regular
dips in two stretches of long duration (about 20 days during each occasions)
when hard X-ray and radio flux were very low. The X-ray light curve and
color-color diagram of the source during these observations are found to be
different from any reported so far. The duration of these dips is found to be
of the order of a few tens of seconds with a repetition time of a few hundred
seconds. The transition between these dips and non-dips which differ in
intensity by a factor of ~ 3.5, is observed to be very fast (~ a few seconds).
It is observed that the low-frequency narrow QPOs are absent in the power
density spectrum (PDS) of the dip and non-dip regions of class $\omega$ and the
PDS is a power law in 0.1 - 10 Hz frequency range. There is a remarkable
similarity in the spectral and timing properties of the source during the dip
and non-dip regions in these set of observations. These properties of the
source are distinctly different from those seen in the observations of other
classes. This indicates that the basic accretion disk structure during both dip
and non-dip regions of class $\omega$ is similar, but differ only in intensity.
To explain these observations, we invoke a model in which the viscosity is very
close to critical viscosity and the shock wave is weak or absent.


title:
Quasi-Periodic Oscillations in Numerical Simulation of Accretion Flows
  Around Black Holes

abstract:
  We present results of several numerical simulations of two dimensional
axi-symmetric accretion flows around black holes using the Smoothed Particle
Hydrodynamics (SPH). We consider both stellar black holes and as well as
super-massive black holes. We assume bremsstrahlung to be the only source of
cooling as it is simpler to implement in numerical simulations. We observe that
due to both radial and vertical oscillation of shock waves in the accretion
flow, the luminosity and average thermal energy content of the inner disk
exhibit very interesting behaviors. When power density spectra are taken,
quasi-periodic oscillations are seen at a few Hz and also occasionally at
hundreds of Hz for stellar black holes. For super-massive black holes, the
time-scale of the oscillations ranges from hours to weeks. The power density
spectra have usual flat top behavior with average {\it rms} amplitude a few
percent and a broken power-law behavior. The break frequency is generally found
to be close to the QPO frequency as seen in the observed power spectra of black
holes.


title: The Most Massive Clusters in the Universe

abstract:
  Clusters of galaxies need to be investigated using complementary approaches
combining all currently available observational techniques (X-ray,
gravitational lensing, dynamics, SZ) on homogeneous samples if one wants to
understand their evolution and physical properties. This is particularly
important in order to relate the observable quantities to the cosmologically
important cluster mass. We present here a number of on-going projects that aim
at studying cluster physics for samples based on currently available all-sky
X-ray surveys such as XBACs, BCS and MACS.


title:
Constraints on the Ionization Balance of Hot-Star Winds from FUSE
  Observations of O Stars in the Large Magellanic Cloud

abstract:
  We use a Sobolev with Exact Integration model to analyze the winds lines of
25 LMC O stars. The data include FUSE profiles of C III, N III, S IV, P V, S
VI, and O VI and IUE or HST data for Si IV, C IV, and N V. Several of the FUSE
lines are unsaturated, so meaningful optical depths (equivalently, mass loss
rate times ionization fractions), as a function of wind velocity can be
determined. Ratios of these quantities give the relative ionization as a
function of velocity and demonstrate that, except for O VI in all stars and S
VI in the later stars, the wind ionization shifts toward lower stages at higher
velocity. Because O VI and S VI do not behave like the other ions, they must be
produced by a different mechanism. Using mass-loss rates determined from the
Vink et al. relationships, we derive mean ionization fractions. Because these
are all less than one, the derived mass loss rates cannot be too small.
However, the ion fractions for P V (expected to be dominant in some winds),
never exceed 0.20. This implies that either the calculated mass loss rates or
the assumed P abundances are too large, or the winds are strongly clumped. We
examine correlations between the mean ion fractions and stellar parameters, and
find two significant relationships. First, as expected, the mean ionization
fraction of lower ions decreases with increasing temperature. Second, the mean
ionization fraction of S VI in the latest stars and O VI in all stars increases
with terminal velocity, re-affirming Cassinelli and Olson's conjecture that O
VI is produced non-radiatively. Finally, we discuss peculiar aspects of three
stars, BI 272, BI 208, and Sk-67 166.


title:
Implications to CMB from Model Independent evolution of w and Late Time
  Phase Transition

abstract:
  We present model independent determination of the CMB from any kind of fluid
that has an equation of state taking four different values. The first region
has $w=1/3$, the second $w=1$, the third $w=-1$ while the last one has
$-1<w=cte<-2/3$. This kind of dynamical $w$ contains as a limit the
cosmological constant and tracker models. We derive the model independent
evolution of $\wp$, for scalar fields, and we see that it remains most of the
time in either of its three extremal values given by $\wp=1,-1,w_{tr}$. This
"varying" $w$ is the generic behavior of scalar fields, quintessence, and we
determine the size of the different regions by solving the dynamical equations
in a model independent way. The dynamical $w$ models have a better fit to CMB
data then the cosmological constant and the tracker models. We determine the
effect of having the first two regions $w=1/3,1$ and depending on the size of
these periods they can be observed in the CMB. In general, the CMB spectrum
sets a lower limit to $\D N_T$ and to the phase transition scale $\Lm_c$. For
smaller $\D N_T$ the CMB peaks are moved to the right of the spectrum and the
hight increases considerably. For $\Ompi=0.1$ the CMB sets a lower limit to the
phase transition scale $\Lm_c\geq 0.2 eV$.


title: Unusual Phase Reversal of Superhumps in ER Ursae Majoris

abstract:
  We studied the evolution of superhumps in the peculiar SU UMa-type dwarf
nova, ER UMa. Contrary to the canonical picture of the SU UMa-type superhump
phenomena, the superhumps of ER UMa show an unexpected phase reversal during
the very early stage (~5 d after the superoutburst maximum). We interpret that
a sudden switch to so-called late superhumps occurs during the very early stage
of a superoutburst. What had been believed to be (ordinary) superhumps during
the superoutburst plateau of ER UMa were actually late superhumps. The
implication of this discovery is briefly discussed.


title:
Deep Near-Infrared Observations and Identifications of Chandra Sources
  in the Orion Molecular Cloud 2 and 3

abstract:
  We conducted deep NIR imaging observations of the Orion molecular cloud 2 and
3 using QUIRC on the 88-inch telescope of the University of Hawaii. Our
purposes are 1) to generate a comprehensive NIR source catalog of these star
forming clouds, and 2) to identify the NIR counterpart of the Chandra X-ray
sources that have no counterpart in the 2MASS catalog. Our J-, H-, and K-band
observations are about 2 mag deeper than those of 2MASS, and well match the
current Chandra observation. We detected 1448 NIR sources, for which we derived
the position, the J-, H-, and K-band magnitude, and the 2MASS counterpart.
Using this catalog, we identified the NIR counterpart for about 42% of the
2MASS-unIDed Chandra sources. The nature of these Chandra sources are discussed
using their NIR colors and spatial distributions, and a dozen protostar and
brown dwarf candidates are identified.


title: The State of the Dark Energy Equation of State

abstract:
  By combining data from seven cosmic microwave background experiments
(including the latest WMAP results) with large scale structure data, the Hubble
parameter measurement from the Hubble Space Telescope and luminosity
measurements of Type Ia supernovae we demonstrate the bounds on the dark energy
equation of state $w_Q$ to be $-1.38< w_Q <-0.82$ at the 95% confidence level.
Although our limit on $w_Q$ is improved with respect to previous analyses,
cosmological data does not rule out the possibility that the equation of state
parameter $w_Q$ of the dark energy $Q$ is less than -1. We present a tracking
model that ensures $w_Q \le -1$ at recent times and discuss the observational
consequences.


title: The influence of microlensing on the shape of the AGN Fe K-alpha line

abstract:
  We study the influence of gravitational microlensing on the AGN Fe K-alpha
line confirming that unexpected enhancements recently detected in the iron line
of some AGNs can be produced by this effect. We use a ray tracing method to
study the influence of microlensing in the emission coming from a compact
accretion disc considering both geometries, Schwarzschild and Kerr.
  Thanks to the small dimensions of the region producing the AGN Fe K-alpha
line, the Einstein Ring Radii associated to even very small compact objects
have size comparable to the accretion disc hence producing noticeable changes
in the line profiles. Asymmetrical enhancements contributing differently to the
peaks or to the core of the line are produced by a microlens, off-centered with
respect to the accretion disc.
  In the standard configuration of microlensing by a compact object in an
intervening galaxy, we found that the effects on the iron line are two orders
of magnitude larger than those expected in the optical or UV emission lines. In
particular, microlensing can satisfactorily explain the excess in the iron line
emission found very recently in two gravitational lens systems, H 1413+117 and
MG J0414+0534.
  Exploring other physical {scenario} for microlensing, we found that compact
objects (of the order of one Solar mass) which belong to {the bulge or the
halo} of the host galaxy can also produce significant changes in the Fe
K$_\alpha$ line profile of an AGN. However, the optical depth estimated for
this type of microlensing is {very small, $\tau\sim 0.001$, even in a favorable
case.


title: Does IRAS 16293-2422 contain a hot core? New interferometric results

abstract:
  High angular resolution H2CO line observations have been carried out for the
low mass proto-binary star IRAS 16293-2422 using the OVRO millimeter array.
Simultaneous continuum observations reveal that the source most probably
contains two accretion disks, less than 250 AU in size, through which matter is
fed onto the stars. The observations suggest that the binary has cleared most
of the material in the inner part of the envelope, out to the binary
separation. The H2CO interferometer observations indicate the presence of large
scale rotation roughly perpendicular to the large scale CO outflow associated
with this source. The H2CO emission is dominated by the compact dense and hot
(T>100 K) gas close to the positions of the continuum peaks.


title: Molecular abundances in low-mass protostellar envelopes

abstract:
  A study of the chemical structure of the envelopes around a sample protostars
is introduced. Physical models for the envelopes derived using 1D radiative
transfer modeling of their dust continuum emission are used as input for Monte
Carlo modeling of single-dish line observations in order to establish the
chemical inventories for the different sources. CO and HCO+ abundances are
found to be correlated with envelope mass: the sources with the most massive
envelopes show the lowest abundances, supporting the idea that the depletion of
these molecules is most efficient in the colder, denser environments. Other
molecules like CS and HCN do not show a similar trend. Deuterated species like
DCO+ and DCN also show signs of correlations with envelope mass and
temperature: the deuterium fractionation of HCO+ is most prominent for the
coldest and most massive envelopes in the sample and at the same time
anti-correlated with the fractionation of HCN. This puts constraints on the low
temperature gas-phase deuterium chemistry.


title: Studying Infall

abstract:
  The study of protostellar collapse or infall has proven unusually difficult
and controversial. Some historical context will be provided, against which
recent advances can be measured. We now have a substantial number of objects
with signatures that can be interpreted in terms of collapse, but a number of
issues remain. One issue is the effect of chemical variations, especially
depletion in the dense, cold interiors of cores that are likely to form low
mass stars. Strategies for dealing with this issue depend on using dust
emission to constrain the density and temperature distribution, leaving
molecular line observations to constrain dynamics and abundance distributions.
Recent progress in this area will be described and we will consider the next
challenges to be overcome. Interferometeric observations, especially with
future instruments, will provide a powerful tool. In combination with chemical
studies coupled with dynamical models, the observations made possible by
interferometers should finally put this subject on a firm foundation.


title:
Chandra Multi-wavelength Plane (ChaMPlane) Survey: Design and Initial
  Results

abstract:
  The Chandra Multiwavength Plane (ChaMPlane) Survey of the galactic plane
incorporates serendipitous sources from selected Chandra pointings in or near
the galactic plane (b < 12deg; >20 ksec; lack of bright diffuse or point
sources) to measure or constrain the luminosity function of low-luminosity
accretion sources in the Galaxy. The primary goal is to detect and identify
accreting white dwarfs (cataclysmic variables, with space density still
uncertain by a factor of >10-100), neutron stars and black holes (quiescent low
mass X-ray binaries) to constrain their space densities and thus origin and
evolution. Secondary objectives are to identify Be stars in high mass X-ray
binaries and constrain their space densities, and to survey the H-R diagram for
stellar coronal sources. A parallel optical imaging under the NOAO Long Term
Survey program provides deep optical images using the Mosaic imager on the CTIO
and KPNO 4-m telescopes. The 36arcmin X 36arcmin optical images (Halpha, R, V
and I) cover ~5X the area of each enclosed Chandra ACIS FOV, providing an
extended survey of emission line objects for comparison with Chandra.
Spectroscopic followup of optical counterparts is then conducted, thus far with
WIYN and Magellan. The X-ray preliminary results from both the Chandra and
optical surveys will be presented, including logN-logS vs. galactic position
(l,b) and optical idenifications.


title: Initial Optical Results for the ChaMPlane Survey

abstract:
  We provide a brief description of the optical survey being conducted under
the NOAO Long Term Surveys program in support of the Chandra Multiwavelength
Plane (ChaMPlane) Survey (see paper by Grindlay et al. in this Volume). A
representative photometry result is shown, along with spectroscopic followup.


title: Background Measurements from Balloon-Borne CZT Detectors

abstract:
  We report detector characteristics and background measurements from two
prototype imaging CZT detectors flown on a scientific balloon payload in May
2001. The detectors are both platinum-contact 10mm x 10mm x 5mm CZT crystals,
each with a 4 $\times$ 4 array of pixels tiling the anode. One is made from
IMARAD horizontal Bridgman CZT, the other from eV Products high-pressure
Bridgman material. Both detectors were mounted side-by-side in a flip-chip
configuration and read out by a 32-channel IDE VA/TA ASIC preamp/shaper. We
enclosed the detectors in the same 40deg field-of-view collimator (comprisinga
graded passive shield and plastic scintillator) used in our previously-reported
September 2000 flight. I-V curves for the detectors are diode-like, and we find
that the platinum contacts adhere significantly better to the CZT surfaces than
gold to previous detectors. The detectors and instrumentation performed well in
a 20-hour balloon flight on 23/24 May 2001. Although we discovered a
significant instrumental background component in flight, it was possible to
measure and subtract this component from the spectra. The resulting IMARAD
detector background spectrum (from 30 keV to ~450 keV) reaches ~5 x 10^{-3}$
counts/cm^2 -sec-keV at 100 keV and has a power-law index of ~2 at high
energies. The eV Products detector has a similar spectrum, although there is
more uncertainty in the energy scale because of calibration complications.


title:
Detection of diffuse TeV gamma-ray emission from the nearby starburst
  galaxy NGC 253

abstract:
  We report the TeV gamma-ray observations of the nearby normal spiral galaxy
NGC 253. At a distance of $\sim$2.5 Mpc, NGC 253 is one of the nearest
starburst galaxies. This relative closeness, coupled with the high star
formation rate in the galaxy, make it a good candidate TeV gamma-ray source.
Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m
imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at
the $\sim 11\sigma$ level with a flux of $(7.8 \pm 2.5)\times 10^{-12} {\rm
cm}^{-2} {\rm sec}^{-1}$ at energies $>$0.5 TeV. The data indicate that the
emission region is broader than the point spread function of our telescope.


title: Detection of X-ray Emission from the Eastern Radio Lobe of PICTOR A

abstract:
  The XMM-Newton satellite has revealed extended X-ray emission from the
eastern radio lobe of the Fanaroff-Riley II Radio Galaxy Pictor A. The X-ray
spectrum, accumulated on a region covering about half the entire radio lobe, is
well described by both a thermal model and a power law. The X-ray emission
could be thermal and produced by circum-galactic gas shocked by the expanding
radio lobe or, alternatively, by Inverse Compton (IC) of cosmic microwave
background photons by relativistic electrons in the lobe. The latter
possibility seems to be supported by the good agreement between the
lobe-average synchrotron radio index and the X-ray energy slope. However, if
this is the case, the magnetic field, as deduced from the comparison of the IC
X-ray and radio fluxes, is more than a factor 2 below the equipartition value
estimated in the same X-ray region.


title: Starburst Galaxies and the X-Ray Background

abstract:
  Integrated X-ray spectra of an evolving population of starburst galaxies
(SBGs) are determined based on the observed spectra of local SBGs. In addition
to emission from hot gas and binary systems, our model SBG spectrum includes a
nonthermal component from Compton scattering of relativistic electrons by the
intense ambient far-IR and the (steeply evolving) CMB radiation fields. We use
these integrated spectra to calculate the levels of contribution of SBGs to the
cosmic X-ray background assuming that their density evolves as (1+z)^q up to a
maximal redshift of 5. We find that at energies <10 keV this contribution is at
a level of few percent for q up to 3, and in the range of 5%-15% for q ~ 4.5.
The Compton component is predicted to be the main SBG emission at high
energies, and its relative contribution gets progressively higher for
increasing redshift.


title: The XMM-Newton Survey Science Centre Medium Sensitivity Survey

abstract:
  We present preliminary results on the XMM-Newton Survey Science Centre medium
sensitivity survey (XMS), with 0.5-4.5 keV flux limit 2 10^{-14} erg/cm2/s. At
present, 19 fields have been examined with a total of 239 X-ray sources.
Identifications for about 2/3 of these reveal that type 1 AGN dominate, but
type 2 AGN, absorption-line galaxies and clusters as well as stars are also
present. We also discuss on a few X-ray selected Broad-Absorption-Line QSOs
found in this survey.


title:
Critical review of the results of the Homestake solar neutrino
  experiment

abstract:
  The radiochemical experiment in the Homestake mine was designed to measure
the solar neutrino flux through the detection of $^{37}Ar$ produced in the
reaction $\nu_e + ^{37}Cl \longrightarrow e^-+^{37}Ar$. The comparison between
this measurement and the theoretical predictions from solar models evidences a
substantial disagreement. I reanalyzed the data evidencing a bias with high
statistical significance and suggesting a new interpretation of the data.


title: Status of IGEX dark matter search at Canfranc Underground Laboratory

abstract:
  One IGEX 76Ge double-beta decay detector is currently operating in the
Canfranc Underground Laboratory in a search for dark matter WIMPs, through the
Ge nuclear recoil produced by the WIMP elastic scattering. In this talk we
report on the on-going efforts to understand and eventually reject the
background at low energy. These efforts have led to the improvement of the
neutron shielding and to partial reduction of the background, but still the
remaining events are not totally identified. A tritium contamination or
muon-induced neutrons are considered as possible sources, simulations and
experimental test being still under progress. According to the success of this
study we comment the prospects of the experiment as well as those of its future
extension, the GEDEON dark matter experiment.


title:
The thermal radiation of the isolated neutron star RX J1856.5-3754
  observed with Chandra and XMM-Newton

abstract:
  We present results of the analysis of data collected in 57-ks XMM-Newton and
505-ks Chandra observations of the nearby ~= 120 pc isolated neutron star RX
J1856.5-3754. We confirm most of the statements made by Burwitz et al. (2001)
who discussed the original 55-ks Chandra data. Detailed spectral analysis of
the combined X-ray and optical data rules out the currently available
nonmagnetic light and heavy element neutron star atmosphere (LTE) models with
hydrogen, helium, iron and solar compositions. We find that strongly magnetized
atmosphere models also are unable to represent the data. The X-ray and optical
data show no spectral features and are best fitted with a two-component
blackbody model with kT_{bb,X}^{\infty} ~= 63.5 eV and R_{bb,X}^{\infty} ~=
4.4(d/120 pc) km for the hot X-ray emitting region, and kT_{bb,opt}^{\infty}<33
eV and R_{bb,opt}^{\infty}>17(d/120 pc) km for the rest of the neutron star
surface responsible for the optical flux. The large number of counts collected
with XMM-Newton allows us to reduce the upper limit on periodic variation in
the X-ray range down to 1.3% (at a 2\sigma confidence level) in the 10^{-3}-50
Hz frequency range. In an attempt to explain this small variability, we discuss
an one-component model with kT_{bb}^{\infty} ~= 63 eV and R_{bb}^{\infty} ~=
12.3(d/120 pc) km. This model requires a low radiative efficiency in the X-ray
domain, which may be expected if the neutron star has a condensed matter
surface.


title:
12CO(J=2->1) and CO(J=3->2) observations of Virgo Cluster spiral
  galaxies with the KOSMA telescope: global properties

abstract:
  We present 12CO(J=2->1) and CO(J=3->2) observations of quiescent Virgo
Cluster spiral galaxies with the KOSMA 3m submm telescope. The beam sizes of
80" at 345 GHz and 120" at 230 GHz are well suited for the investigation of
global properties of Virgo Cluster galaxies. The observed sample was selected
based on previous 12CO(J=1->0) detections by Stark et al. (1986), performed
with the AT&T Bell Laboratory 7m telescope (beam size 100"). We were able to
detect 18 spiral galaxies in 12CO(2->1) and 16 in 12CO(3->2). Beam matched
observations of the lowest three 12CO transitions allow us to compare our
results with previous high spatial resolution studies of (moderate) starburst
galaxies and galactic core regions. We discuss the global excitation conditions
of the ISM in these quiescent spiral galaxies. The resulting CO (3--2)/(1--0)
integrated line ratios vary over a relatively narrow range of values from 0.35
to 0.14 (on a K km/s-scale) with increasing CO (2--1)/(1--0) ratio (from 0.5 to
1.1). The line ratios between the three lowest rotational transitions of CO
cannot be fitted by any radiative transfer model with a single source
component. A two-component model, assuming a warm, dense nuclear and a cold,
less dense disc component allows us to fit the observed line ratios for most of
the galaxies individually by selecting suitable parameters. The two-component
model, however, fails to explain the observed correlation of the line ratios.
This is due to a variation of the relative filling factor of the warm gas
alone, assuming a typical set of parameters for the two components common for
all galaxies.


title: Application of the global modal approach to the spiral galaxies

abstract:
  We have tested the applicability of the global modal approach in the density
wave theory of spiral structure for a sample of spiral galaxies with measured
axisymmetric background properties. We report here the results of the
simulations for four galaxies: NGC 488, NGC 628, NGC 1566, and NGC 3938. Using
the observed radial distributions for the stellar velocity dispersions and the
rotation velocities we have constructed the equilibrium models for the galactic
disks in each galaxy and implemented two kinds of stability analyses - the
linear global analysis and 2D-nonlinear simulations. In general, the global
modal approach is able to reproduce the observed properties of the spiral arms
in the galactic disks. The growth of spirals in the galactic disks can be
physically understood in terms of amplification by over-reflection at the
corotation resonance. Our results support the global modal approach as a
theoretical explanation of spiral structure in galaxies.


title: Gamma photometric redshifts for long gamma-ray bursts

abstract:
  It is known that the soft tail of the gamma-ray bursts' spectra show excesses
from the exact power-law dependence. In this article we show that this
departure can be detected in the peak flux ratios of different BATSE DISCSC
energy channels. This effect allows to estimate the redshift of the bright long
gamma-ray bursts in the BATSE Catalog. A verification of these redshifts is
obtained for the 8 GRB which have both BATSE DISCSC data and measured optical
spectroscopic redshifts. There is good correlation between the measured and
esti redshifts, and the average error is $\Delta z \approx 0.33$. The method is
similar to the photometric redshift estimation of galaxies in the optical
range, hence it can be called as "gamma photometric redshift estimation". The
estimated redshifts for the long bright gamma-ray bursts are up to $z \simeq
4$. For the the faint long bursts - which should be up to $z \simeq 20$ - the
redshifts cannot be determined unambiguously with this method.


title: Interstellar H_2 in M 33 detected with FUSE

abstract:
  FUSE spectra of the four brightest H II regions in M 33 show absorption by
interstellar gas in the Galaxy and in M 33. On three lines of sight molecular
hydrogen in M 33 is detected. This is the first measurement of diffuse H_2 in
absorption in a Local Group galaxy other than the Magellanic Clouds. A
quantitative analysis is difficult because of the low signal to noise ratio and
the systematic effects produced by having multiple objects in the FUSE
aperture. We use the M 33 FUSE data to demonstrate in a more general manner the
complexity of interpreting interstellar absorption line spectra towards
multi-object background sources. We derive H_2 column densities of
approximately 10^16 to 10^17 cm^{-2} along 3 sight lines (NGC 588, NGC 592, NGC
595). Because of the systematic effects, these values most likely represent
upper limits and the non-detection of H_2 towards NGC 604 does not exclude the
existence of significant amounts of molecular gas along this sight line.


title: On the influence of radio galaxies on cooling flows: M87 and Cygnus A

abstract:
  Results from Chandra studies of the intracluster medium around M87 and Cygnus
A are summarized.


title: The Serpens Star-Forming Region in HCO+, HCN, and N2H+

abstract:
  This poster presents single-dish and aperture-synthesis observations of the
J=1-0 (lambda~3 mm) transitions of HCO+, HCN, and N2H+ towards the Serpens
star-forming region. Jets driven by young stars affect the structure and the
chemistry of their surrounding cloud, and this work aims to assess the extent
to which the emission of these three molecular lines is dominated by such
processes. In Serpens I find that N2H+ 1-0 traces the total amount of material,
except in two regions slightly ahead of shocks. In contrast, the HCO+ and,
especially, HCN emission is dominated by regions impacted by outflows. One
previously unknown, strongly shocked region is located ~0.1 pc northwest of the
young stellar object SMM 4. There is a marked spatial offset between the peaks
in the HCN and the N2H+ emission associated with shocked regions. I construct a
simple, qualitative chemical model where the N2H+ emission increases in the
magnetic precursor of a C-type shock, while N2H+ is destroyed deeper in the
shock as the neutrals heat up and species like HCN and water are released from
icy grain mantles. I conclude that N2H+ is a reliable tracer of cloud material,
and that unresolved observations of HCO+ and HCN will be dominated by material
impacted by outflows.


title: The IR spectral energy distribution of the Seyfert 2 prototype NGC 5252

abstract:
  The complete mid- to far- infrared continuum energy distribution collected
with the Infrared Space Observatory of the Seyfert 2 prototype NGC 5252 is
presented. ISOCAM images taken in the 3--15 micron range show a resolved
central source that is consistent at all bands with a region of about 1.3 kpc
in size. Due to the lack of on going star formation in the disk of the galaxy,
this resolved emission is associated with either dust heated in the nuclear
active region or with bremsstrahlung emission from the nuclear and extended
ionised gas. The size of the mid-IR emission contrasts with the standard
unification scenario envisaging a compact dusty structure surrounding and
hiding the active nucleus and the broad-line region. The mid-IR data are
complemented with ISOPHOT aperture photometry in the 25--200 micron range. The
overall IR spectral energy distribution is dominated by a well-defined
component peaking at about 100$ micron, a characteristic temperature of T ~20
K, and an associated dust mass of 2.5 x 10E7 Msun, which greatly dominates the
total dust mass content of the galaxy. The heating mechanism of this dust is
probably the interstellar radiation field. After subtracting the contribution
of this cold dust component, the bulk of the residual emission is attributed to
dust heated within the nuclear environment. Its luminosity consistently
accounts for the reprocessing of the X-ray to UV emission derived for the
nucleus of this galaxy. The comparison of NGC 5252 spectral energy distribution
with current torus models favors large nuclear disk structure on the kiloparsec
scale.


title: The Fate of Dark Energy

abstract:
  By studying the present cosmological data, particularly on CMB, SNeIA and
LSS, we find that the future fate of the universe, for simple linear models of
the dark energy equation-of-state, can vary between the extremes of (I) a
divergence of the scale factor in as little as 7 Gyr; (II) an infinite lifetime
of the universe with dark energy dominant for all future time; (III) a
disappearing dark energy where the universe asymptotes as $t \to \infty$ to
$a(t) \sim t^{2/3}$ {\it i.e.} matter domination. Our dreadful conclusion is
that no amount of data from our past light-cone can select between these future
scenarios.


title:
Big Bang nucleosynthesis and cosmic microwave background constraints on
  the time variation of the Higgs vacuum expectation value

abstract:
  We derive constraints on the time variation of the Higgs vacuum expectation
value $<\phi>$ through the effects on Big Bang nucleosynthesis (BBN) and the
cosmic microwave background (CMB). In the former case, we include the
(previously-neglected) effect of the change in the deuteron binding energy,
which alters both the $^4$He and deuterium abundances significantly. We find
that the current BBN limits on the relative change in \higgs are $-(0.6 - 0.7)
\times 10^{-2} < Delta<\phi>/<\phi> < (1.5 - 2.0) \times 10^{-2}$, where the
exact limits depend on the model we choose for the dependence of the deuteron
binding energy on \higgs.The limits from the current CMB data are much weaker.


title:
Star Formation and Metallicity History of the SDSS galaxy survey:
  unlocking the fossil record

abstract:
  Using MOPED we determine non-parametrically the star-formation and
metallicity history of over 37,000 high-quality galaxy spectra from the Sloan
Digital Sky Survey (SDSS) early data release. We use the entire spectral range,
rather than concentrating on specific features, and we estimate the complete
star formation history without prior assumptions about its form (by
constructing so-called `population boxes'). The main results of this initial
study are that the star formation rate in SDSS galaxies has been in decline for
~6 Gyr; a metallicity distribution for star-forming gas which is peaked ~3 Gyr
ago at about solar metallicity, inconsistent with closed-box models, but
consistent with infall models. We also determine the infall rate of gas in SDSS
and show that it has been significant for the last 3 Gyr. We investigate errors
using a Monte-Carlo Markov Chain algorithm. Further, we demonstrate that
recovering star formation and metallicity histories for such a large sample
becomes intractable without data compression methods, particularly the
exploration of the likelihood surface. By exploring the whole likelihood
surface we show that age-metallicity degeneracies are not as severe as by using
only a few spectral features. We find that 65% of galaxies contain a
significant old population (with an age of at least 8 Gyr), including recent
starburst galaxies, and that over 97% have some stars older than 2 Gyr. It is
the first time that the past star formation history has been determined from
the fossil record of the present-day spectra of galaxies.


title: Sensitivity of Transit Searches to Habitable Planets

abstract:
  Photon-limited transit surveys in V band are in principle about 20 times more
sensitive to planets of fixed size in the habitable zone around M stars than G
stars. In I band the ratio is about 400. The advantages that the habitable zone
lies closer and that the stars are smaller (together with the numerical
superiority of M stars) more than compensate for the reduced signal due to the
lower luminosity of the later-type stars. That is, M stars can yield reliable
transit detections at much fainter apparent magnitudes than G stars. However,
to achieve this greater sensitivity, the later-type stars must be monitored to
these correspondingly fainter magnitudes, which can engender several practical
problems. We show that with modest modifications, the Kepler mission could
extend its effective sensitivity from its current M_V=6 to M_V=9. This would
not capture the whole M dwarf peak, but would roughly triple its sensitivity to
Earth-like planets in the habitable zone. However, to take advantage of the
huge bump in the sensitivity function at M_V=12 would require major changes.


title: Changes in Solar Dynamics from 1995 to 2002

abstract:
  Data obtained by the GONG and MDI instruments over the last seven years are
used to study how solar dynamics -- both rotation and other large scale flows
-- have changed with time. In addition to the well known phenomenon of bands of
faster and slower rotation moving towards the equator and pole, we find that
the zonal flow pattern rises upwards with time. Like the zonal flows, the
meridional flows also show distinct solar activity related changes. In
particular, the anti-symmetric component of the meridional flow shows a
decrease in speed with activity. We do not see any significant temporal
variations in the dynamics of the tachocline region where the solar dynamo is
believed to be operating.


title:
On breaking the age-metallicity degeneracy in early-type galaxies:
  infall versus star formation efficiency

abstract:
  The correlation between [Mg/Fe] and galaxy mass found in elliptical galaxies
sets a strong constraint on the duration of star formation. Furthermore, the
colour-magnitude relation restricts the range of ages and metallicities of the
stellar populations. We combine these two constraints with a model of star
formation and chemical enrichment including infall and outflow of gas to find
that the trend towards supersolar [Mg/Fe] in massive ellipticals excludes a
pure metallicity sequence as an explanation of the colour-magnitude relation.
An age spread is required, attributable either to a range of star formation
efficiencies or to a range of infall timescales. We find that the inferred
range of stellar ages is compatible with the small scatter and the redshift
evolution of the colour-magnitude relation. Two alternative scenarios can
explain the data: fixed infall with an efficiency which is linearly dependent
on mass, or a fixed efficiency with a mass-dependent infall timescale
t~1/sqrt(M). We conclude that the actual scenario may well involve a
combination of these two parameters, with mass dependencies which should span
the range of those given above.


title:
X-ray Emission Line Profile Modeling of O stars: Fitting a
  Spherically-Symmetric Analytic Wind-Shock Model to the Chandra Spectrum of
  zeta Puppis

abstract:
  X-ray emission line profiles provide the most direct insight into the
dynamics and spatial distribution of the hot, X-ray-emitting plasma above the
surfaces of OB stars. The O supergiant zeta Puppis shows broad, blueshifted,
and asymmetric line profiles, generally consistent with the wind-shock picture.
We model the profiles of eight lines in the Chandra HETGS spectrum of this
prototypical hot star. The fitted lines indicate that the plasma is distributed
throughout the wind starting close to the photosphere, that there is
significantly less attenuation of the X-rays by the overlying wind than is
generally supposed, and that there is not a strong trend in wind absorption
with wavelength.


title: The Chemical Compositions of Galactic Disk F and G Dwarfs

abstract:
  Photospheric abundances are presented for 27 elements from carbon to europium
in 181 F-G dwarfs from a differential LTE analysis of high-resolution and high
signal-to-noise spectra. Stellar $T_{\rm eff}$ were adopted from an infrared
flux method calibration of Str\"{o}mgren photometry. Stellar log $g$ were
calculated from {\it Hipparcos} parallaxes and stellar evolutionary tracks.
Stellar space motions ($U, V, W$) and a Galactic potential were used to
estimate Galactic orbital parameters.
  Results of $\alpha$-elements -- O, Mg, Si, Ca, and Ti -- show [$\alpha$/Fe]
to increase slightly with decreasing [Fe/H]. Heavy elements with dominant
contributions at solar metallicity from the $s$-process show [$s$/Fe] to
decrease slightly with decreasing [Fe/H]. Scatter in [X/Fe] at a fixed [Fe/H]
is entirely attributable to the small measurement errors, after excluding the
few thick disc stars and the $s$-process enriched CH subgiants. Tight limits
are set on `cosmic' scatter.
  By combining our sample with published studies, thick disc stars are
identified by their $V_{LSR}$ in the range $- 40$ to -100 km s$^{-1}$. These
are very old stars with origins in the inner Galaxy and metallicities [Fe/H]
$\leq -0.4$. At the same [Fe/H], the sampled thin disc stars have $V_{LSR} \sim
0$ km s$^{-1}$, and are generally younger with a birthplace at about the Sun's
Galactocentric distance. In the range $-$0.35 $\geq$ [Fe/H] $\geq$ $-$0.70,
well represented by present thin and thick disc samples, [X/Fe] of the thick
disc stars is greater than that of thin disc stars for Mg, Al, Si, Ca, Ti, and
Eu. [X/Fe] is very similar for the thin and thick disc for -- notably -- Na,
and iron-group elements.


title:
X-Ray Emission from Multi-Phase Shock in the Large Magellanic Cloud
  Supernova Remnant N49

abstract:
  The supernova remnant (SNR) N49 in the Large Magellanic Cloud has been
observed with the Advanced CCD Imaging Spectrometer (ACIS) on board the {\it
Chandra X-Ray Observatory}. The superb angular resolution of the {\it
Chandra}/ACIS images resolves a point source, the likely X-ray counterpart of
soft gamma-ray repeater SGR 0526$-$66, and the diffuse filaments and knots
across the SNR. These filamentary features represent the blast wave sweeping
through the ambient interstellar medium and nearby dense molecular clouds. We
detect metal-rich ejecta beyond the main blast wave shock boundary in the
southwest of the SNR, which appear to be explosion fragments or ``bullets''
ejected from the progenitor star. The detection of strong H-like Si line
emission in the eastern side of the SNR requires multi-phase shocks in order to
describe the observed X-ray spectrum, whereas such a multi-phase plasma is not
evident in the western side. This complex spectral structure of N49 suggests
that the postshock regions toward the east of the SNR might have been reheated
by the reverse shock off the dense molecular clouds while the blast wave shock
front has decelerated as it propagates into the dense clouds. The X-ray
spectrum of the detected point-like source is continuum dominated and can be
described with a power law of $\Gamma$ $\sim$ 3. This provides a confirmation
that this point-like X-ray source is the counterpart of SGR 0526$-$66 in the
quiescent state.


title: Opening A New Window to the Early Universe

abstract:
  DASI has ended a 34-year quest to detect the CMB polarization, sounding the
starting gun for a new race to peer further back in time, with more precision
than ever before. Many more CMB polarization experiments are in progress or
planned. NASA's recently launched Microwave Anisotropy Probe (MAP) should
detect the large-angle polarization induced by early star formation. This
should be followed by increasingly precise ground and balloon experiments
leading to the Launch of the European Space Agency's Planck satellite in 2007.
If the recent past is any indication, studies of the CMB will continue to
advance cosmology, even after Planck.


title:
Optical Line profile variability of the B1+neutron star binary system LS
  I+65 010 = 2S 0114+650

abstract:
  We present high resolution spectroscopic observations of the massive X-ray
binary system LS I+65 010=2S 0114+650 in the optical wavelength region. A
correlation between equivalent width and radial velocity of photospheric
absorption lines is found. The systemic velocity, inferred from the weaker
lines is v_helio = -31 +/- 5 km s^-1, which, if attributed solely to the
Galactic rotation curve, implies that LS I+65 010 lies within 3 kpc from the
Sun. The ISM Na I D lines display 2 resolved high velocity components at
v_helio = -70, -48 km s^-1, possibly associated with gas surrounding the binary
system, in addition to the -24, -8 km s^-1 ISM features due to the Orion and
the Perseus arm regions. Strong photospheric line profile variability is
present on a night to night timescale, with He I 5875 A displaying an
additional blue-shifted absorption in some of the spectra, similar to what is
observed in the optical counterpart of Vela X-1. A connection between the
extended blue wing and X-ray maximum is suggested. Short timescale variations
in line profiles are detected on only two nights, but the evidence that these
variations occur on the 2.78 hour X-ray flaring period is marginal.


title:
The effect of stellar compressibility and non-resonant dynamic tides on
  the apsidal-motion rate in close binaries

abstract:
  The paper is devoted to the analysis of the systematic deviations between the
classical formula for the rate of secular apsidal motion in close binaries and
the formula established within the framework of the theory of dynamic tides.
The basic behaviour is found to be governed by the dependency of the forcing
frequencies on the orbital period and the rotational angular velocity,
irrespective of the stellar model. For binaries with short orbital periods a
good agreement between the classical apsidal-motion formula and the formula
established within the framework of the theory of dynamic tides is only
possible for certain values of the rotational angular velocity.


title:
Low-Frequency Gravitational Waves from Massive Black Hole Binaries:
  Predictions for LISA and Pulsar Timing Arrays

abstract:
  The coalescence of massive black hole (BH) binaries due to galaxy mergers
provides a primary source of low-frequency gravitational radiation detectable
by pulsar timing measurements and by the proposed LISA (Laser Interferometry
Space Antenna) observatory. We compute the expected gravitational radiation
signal from sources at all redshifts by combining the predicted merger rate of
galactic halos with recent measurements of the relation between BH mass, M_bh,
and the velocity dispersion of its host galaxy, sigma. Our main findings are as
follows: (i) the nHz frequency background is dominated by BH binaries at
redshifts z<2, and existing limits from pulsar timing data place tight
constraints on the allowed normalization and power-law slope of the M_bh-sigma
relation or on the fraction of BH binaries that proceed to coalescence; (ii)
more than half of all discrete mHz massive BH sources detectable by LISA are
likely to originate at redshifts z>7; (iii) the number of LISA sources per unit
redshift per year should drop substantially after reionization as long as BH
formation is triggered by gas cooling in galaxies. Studies of the highest
redshift sources among the few hundred detectable events per year, will provide
unique information about the physics and history of black hole growth in
galaxies.


title: CK Vul as a Candidate Eruptive Stellar Merging Event

abstract:
  CK Vul (Nova Vul 1670) is one of the most mysterious objects among erupting
stellar objects. Past studies have suggested that CK Vul is a final
helium-flash object resembling V605 Aql and V4334 Sgr (Sakurai's object). The
peculiar outburst light curve of CK Vul, however, had no similar counterpart
among the known eruptive objects. Furthermore, the presence of hydrogen in the
proposed remnant seems to contradict with the final helium-flash scenario. We
propose that the peculiarities of CK Vul can be naturally understood if we
consider a merging of main-sequence stars, following a new interpretation by
Soker and Tylenda (astro-ph/0210463), which was proposed to explain the
peculiar eruptive object V838 Mon. In this case, the 1670 outburst of CK Vul
may be best understood as a V838 Mon-like event which occurred in our vicinity.


title:
Spectral properties of the X-ray binary pulsar LMC X-4 during different
  intensity states

abstract:
  We present spectral variations of the binary X-ray pulsar LMC X-4 observed
with the RXTE/PCA during different phases of its 30.5 day long third period.
Only out of eclipse data were used for this study. The 3-25 keV spectrum,
modeled with high energy cut-off power-law and iron line emission is found to
show strong dependence on the intensity state. Correlations between the Fe line
emission flux and different parameters of the continuum are presented here.


title:
Relics of Cosmic Quark- Hadron Phase Transition and Massive Compact Halo
  Objects

abstract:
  We propose that the cold dark matter (CDM) is composed entirely of quark
matter, arising from a cosmic quark-hadron transition. We show that compact
gravitational objects, with masses around 0.5 (M_{\odot}), could have evolved
out of the such CDM.


title:
Massive Compact Halo Objects from the Relics of the Cosmic Quark-Hadron
  Transition

abstract:
  The existence of compact gravitational lenses, with masses around 0.5
(M_{\odot}), has been reported in the halo of the Milky Way. The nature of
these dark lenses is as yet obscure, particularly because these objects have
masses well above the threshold for nuclear fusion. In this work, we show that
they find a natural explanation as being the evolutionary product of the
metastable false vacuum domains (the so-called strange quark nuggets) formed in
a first order cosmic quark-hadron transition.


title:
Intergalactic globular clusters and the faint end of the galaxy number
  counts in A1656 (Coma)

abstract:
  The existence of an intergalactic globular cluster population in the Coma
cluster of galaxies has been tested using surface-brightness fluctuations. The
main result is that the intergalactic globular cluster surface density ($N_{\rm
IGC}$) does not correlate with the distance to the center of Coma and hence
with the environment. Furthermore, comparing these results with different Coma
mass-distribution model predictions, it is suggested that $N_{\rm IGC}$ must in
fact be zero all over Coma. On the other hand, the results for $N_{\rm IGC}$
and the faint end of the galaxy number counts (beyond $m_R=23.5$) are
connected. So $N_{\rm IGC}=0$ settles the slope of this function, which turns
out to be $\gamma=0.36\pm0.01$ down to $m_R=26.5$.
  The fact that $N_{\rm IGC}=0$ all over Coma suggests that globular clusters
were formed only, or almost only, from protogalactic clouds. None, or perhaps
very few, could have formed in isolated regions. It also seems inappropriate to
advocate a relationship between intergalactic globular clusters and dark matter
distributions, although it is true that the relationship could still exist but
not be strong enough to have been detected. Finally, since our conclusion is
that intergalactic globular clusters do not exist in Coma, accretion of
intergalactic globular clusters might not be significant in galaxy formation
and evolutionary processes in the Coma galaxies.


title:
Selection of Metal-poor Giant Stars Using the Sloan Digital Sky Survey
  Photometric System

abstract:
  We present a method for photometric selection of metal-poor halo giants from
the imaging data of the Sloan Digital Sky Survey (SDSS). These stars are offset
from the stellar locus in the (g-r) vs. (u-g) color-color diagram. Based on a
sample of 29 candidates for which spectra were taken, we derive a selection
efficiency of the order of 50%, for stars brighter than $r \sim 17^m$. The
candidates selected in 400 deg$^2$ of sky from the SDSS Early Data Release
trace the known halo structures (tidal streams from the Sagittarius dwarf
galaxy, the Draco dwarf spheroidal galaxy), indicating that such a
color-selected sample can be used to study the halo structure even without
spectroscopic information. This method, and supplemental techniques for
selecting halo stars, such as RR Lyrae stars and other blue horizontal branch
stars, can produce an unprecedented three-dimensional map of the Galactic halo
based on the SDSS imaging survey.


title: Bare strange quark stars: formation and emission

abstract:
  Recent achievements of bare strange stars are briefly reviewed. A nascent
protostrange star should be bare because of strong mass ejection and high
temperature after the supernova detonation flame, and a crust can also hardly
form except for a super-Eddington accretion. The magnetosphere of a bare
strange star is composed mainly of electron-positron pair plasma, where both
inner and outer vacuum gaps work for radio as well as high energy nonthermal
emission. A featureless thermal spectrum is expected since no ion is above the
quark surface, whilst electron cyclotron lines could appear in some bare
strange stars with suitable magnetic fields. Various astrophysical implications
of bare strange stars are discussed.


title: Line emission from circumstellar disks around A stars

abstract:
  The nature of the tenuous disks around A stars has raised considerable
controversy in the literature during the past decade. The debate whether or not
the disk around beta Pictoris contains gaseous molecular hydrogen is only the
most recent example. Since CO is in general a poor tracer for the gas content
of these low mass disks, we discuss here detailed emission line calculations
for alternative tracers like C and C+, based on recent optically thin disk
models by Kamp & van Zadelhoff (2001). The [CII] 157.7 mum line was searched
toward Vega and beta Pictoris -- the most prominent A stars with disks -- using
ISO LWS data, and a tentative detection is reported toward the latter object.
  From a comparison with emission line observations as well as absorption line
studies of both stars, the gas-to-dust ratio is constrained to lie between 0.5
and 9 for beta Pictoris. For Vega the [CII] observations indicate an upper
limit of 0.2 M_Earth for the disk gas mass. Predicted line intensities of C+
and C are presented for a range of models and appear promising species to trace
the gas content in the disks around A stars with future instrumental
capabilities (SOFIA, Herschel, APEX and ALMA). Searches for CO emission should
focus on the J=3-2 line.


title:
Nebular diagnostics for young stellar populations: Photon escape versus
  atmosphere blanketing

abstract:
  Emission lines in ionized nebulae can provide strong and useful constraints
on the properties of both ionizing and non-ionizing stellar populations in
regions with star formation, provided that stellar evolution and stellar
atmosphere models can be used in a selfconsistent way. Recently, the
application of these techniques has shown important discrepancies between
predicted and observed nebular spectra that point to stellar atmosphere models
of WR stars which are too energetic and/or to a significant leakageof high
energy photons. In this contribution, these two alternatives are analyzed in
detail.


title:
The Fundamental Plane and the evolution of the M/L ratio of early-type
  field galaxies up to z~1

abstract:
  We analyse the Fundamental Plane (FP) of 26 strong gravitational lens
galaxies with redshifts up to z~1, using tabulated data from Kochanek et al.
(2000) and Rusin et al. (2003). The lens galaxies effectively form a
mass-selected sample of early-type galaxies in environments of relatively low
density. We analyse the FP and its evolution in the restframe Johnson B and
Gunn r bands. Assuming that early-type galaxies are a homologous family, the FP
then provides a direct measurement of the M/L ratio evolution. If we assume
that the M/L ratios of field early-type galaxies evolve as power-laws, we find
for the lens galaxies an evolution rate dlog(M/L)/dz of -0.62 +/-0.13 in
restframe B, corresponding to a mean stellar formation redshift of <z*>=1.8
(-0.5/+1.4). This formation epoch does not differ significantly from that of
cluster galaxies <z*cl>=2.0 (-0.2/+0.3), obtained by van Dokkum & Franx (2001)
after correction for maximum progenitor bias. However, if we impose the
constraint that lens and cluster galaxies that are of the same age have equal
M/L ratios and we do not correct for progenitor bias, we find that the stellar
populations of the lens galaxies are 10-15 % younger. We find that both the M/L
ratios as well as the restframe colors of the lens galaxies show significant
scatter. About half of the lens galaxies are consistent with an old
cluster-like stellar populations, but the other galaxies are bluer and best fit
by single burst models with younger stellar formation redshifts as low as z*~1.
Moreover, the scatter in color is correlated with the scatter in M/L ratio. We
interpret this as evidence of a significant age spread among the stellar
populations of lens galaxies, whereas the ages of the stellar populations of
the cluster galaxies are well approximated by a single formation epoch.


title: The XMM-Newton Serendipitous Source Catalogue

abstract:
  We describe the production, properties and scientific potential of the
XMM-Newton catalogue of serendipitous X-ray sources. The first version of this
catalogue is nearing completion and is planned to be released before the end of
2002.


title: Properties of tangential and radial angles of muons in EAS

abstract:
  Tangential and radial angles of muons in EAS, a useful concept in
investigation of the muon production height, can be used also for the
investigation of the muon momenta. A parameter zeta, being a combination of
tangential and radial angles, is introduced and its possible applications in
investigation of muons in showers are presented.


title: A Critical Examination of Halo White Dwarf Candidates

abstract:
  A detailed analysis of halo white dwarf candidates is presented, which is
based on model atmosphere fits to observed energy distributions built from
photoelectric or photographic magnitudes. Most of the candidates identified in
reduced proper motion diagrams are shown to be too warm (Teff > 5000 K) and
most likely too young to be members of the galactic halo, while the tangential
velocities of the cooler and thus older white dwarfs are shown to be entirely
consistent with the disk population. The results suggest that some white dwarf
stars born in the young disk may have high velocities with respect to the local
standard of rest. Such objects could represent the remnants of donor stars from
close mass-transfer binaries that produced type Ia supernovae via the single
degenerate channel, or other scenarios suggested in the literature. Ongoing
surveys that rely solely on reduced proper motion diagrams are likely to
identify more of these high velocity young degenerates, rather than to unveil
the old white dwarf population of the galactic halo. The importance of infrared
photometry for studying extremely cool white dwarfs is also emphasized.


title:
Spatial study with the VLT of a new resolved edge-on circumstellar dust
  disk discovered at the periphery of the rho Ophiuchi dark cloud

abstract:
  We report the discovery in NIR with SofI at the NTT of a resolved
circumstellar dust disk around a 2MASS source at the periphery of the rho
Ophiuchi dark cloud. We present follow-up observations in J, H, and Ks-band
obtained with ISAAC at the VLT, under 0.4"-seeing conditions, which unveil a
dark dust lane oriented East-West between two characteristic northern and
southern reflection nebulae. This new circumstellar dust disk has a radius of
2.15" (300 AU at 140 pc), and a width of 1.2" (170 AU at 140 pc). Thanks to its
location at the periphery of the dense cores, it suffers small foreground
visual extinction (Av=2.1\pm2.6 mag). Although this disk is seen close to
edge-on, the two reflection nebulae display very different colors. We introduce
a new NIR data visualization called ``Pixel NIR Color Mapping'', which allows
to visualize directly the NIR colors of the nebula pixels. Thanks to this
method we identify a ridge, 0.3" (40 AU at 140 pc) to the north of the dark
lane and parallel to it, which displays a NIR color excess. This ridge
corresponds to an unusual increase of brightness from J to Ks, which is also
visible in the NTT observation obtained 130 days before the VLT one. We also
find that the northern nebula shows ~3 mag more extinction than the southern
nebula. We compute axisymmetric disk models to reproduce the VLT scattered
light images and the spectral energy distribution from optical to NIR. Our best
model, with a disk inclination i=86\pm1 deg, correctly reproduces the extension
of the southern reflection nebula, but it is not able to reproduce either the
observed NIR color excess in the northern nebula or the extinction difference
between the two reflection nebulae. We discuss the possible origin of the
peculiar asymmetrical NIR color properties of this object.


title: Status of the BAIKAL neutrino project

abstract:
  We review the present status of the Baikal Neutrino Project and present
results on upward going atmospheric neutrinos, results of a search for high
energy extraterrestrial neutrinos as well as preliminary results of searching
for acoustic signals from EAS in water. We describe the moderate upgrade of
NT-200 planned for next years and discuss a possible detector on the Gigaton
scale.


title:
The discovery of a new non-thermal X-ray filament near the Galactic
  Centre

abstract:
  We report the discovery by XMM-Newton and Chandra of a hard extended X-ray
source (XMM J174540-2904.5) associated with a compact non-thermal radio
filament (the Sgr A-E `wisp'=1LC 359.888-0.086= G359.88-0.07), which is located
within ~4 arcmin of the Galactic Centre. The source position is also coincident
with the peak of the molecular cloud, M -0.13-0.08 (the `20 km/s' cloud). The
X-ray spectrum is non-thermal with an energy index of 1.0 (+1.1 -0.9) and
column density of 38 (+7 -11) x 10^22 H/cm2. The observed 2--10 keV flux of 4 x
10^-13 erg/s/cm2 converts to an unabsorbed X-ray luminosity of 1 x 10^34 erg/s
assuming a distance of 8.0 kpc. The high column density strongly suggests that
this source is located in or behind the Galactic Centre Region. Taking account
of the broad-band spectrum, as well as the source morphology and the positional
coincidence with a molecular cloud, we concluded that both the radio and X-ray
emission are the result of synchrotron radiation. This is the first time a
filamentary structure in the Galactic Centre Region. has been shown,
unequivocally, to have a non-thermal X-ray spectrum.


title: The gamma ray background from large scale structure formation

abstract:
  Hierarchical clustering of dark matter halos is thought to describe well the
large scale structure of the universe. The baryonic component of the halos is
shock heated to the virial temperature while a small fraction of the energy
flux through the shocks may be energized through the first order Fermi process
to relativistic energy per particle. It has been proposed that the electrons
accelerated in this way may upscatter the photons of the universal microwave
background to gamma ray energies and indeed generate a diffuse background of
gamma rays that compares well to the observations. In this paper we calculate
the spectra of the particles accelerated at the merger shocks and re-evaluate
the contribution of structure formation to the extragalactic diffuse gamma ray
background (EDGRB), concluding that this contribution adds up to at most 10% of
the observed EDGRB.


title:
Physical conditions in the Protoplanetary Nebula CRL 618 derived from
  observations of vibrationally excited HCCCN

abstract:
  We used the Effelsberg 100m and IRAM 30m telescopes to observe vibrationally
excited cyanoacetylene (HCCCN) in several rotational transitions toward the
proto-planetary nebula CRL618. Lines from 9 different vibrationally excited
states with energies ranging up to 1600 K above ground were detected. The lines
show P Cygni profiles indicating that the HCCCN emission originates from an
expanding and accelerating molecular envelope. The HCCCN rotational temperature
varies with velocity, peaks at 520 K, 3 km/s blue-shifted from the systemic
velocity and decreases with higher blueshift of the gas. The column density of
the absorbing HCCCN is 3-6 x 1E17 cm^2. We modeled spectra based on spherical
models of the expanding envelope which provide an excellent fit to the
observations, and discuss the implications of the models. Additionally, lines
from 13C substituted cyanoacetylene were observed. They can be used to
constrain the 12C/13C ratio in this source to 10+-2.