title:
Search for nearby stars among proper motion stars selected by
  optical-to-infrared photometry. II. Two late M dwarfs within 10 pc

abstract:
  We have identified two late M dwarfs within 10 parsecs of the Sun, by
cross-correlating the Luyten NLTT catalogue of stars with proper motions larger
than 0.18 arcsec/yr, with objects lacking optical identification in the 2MASS
data base. The 2MASS photometry was then combined with improved optical
photometry obtained from the SuperCOSMOS Sky Surveys. The two objects (LP775-31
and LP655-48) have extremely red optical-to-infrared colours ((R-K)~7) and very
bright infrared magnitudes (K_s<10): follow-up optical spectroscopy with the
ESO 3.6-m telescope gave spectral types of M8.0 and M7.5 dwarfs, respectively.
Comparison of their near-infrared magnitudes with the absolute magnitudes of
known M8 and M7.5 dwarfs with measured trigonometric parallaxes yields
spectroscopic distance estimates of 6.4+/-1.4 parsecs and 8.0+/-1.6 parsecs for
LP775-31 and LP655-48, respectively. In contrast, Cruz & Reid (2002) recently
determined spectral types of M6 for both objects, and commensurately larger
distances of 11.3+/-1.3 parsecs and 15.3+/-2.6 parsecs. LP655-48 is also a
bright X-ray source (1RXS J044022.8-053020). With only a few late M dwarfs
previously known within 10 parsecs, these two objects represent an important
addition to the census of the Solar neighbourhood.


title: A survey of molecular hydrogen in the central galaxies of cooling flows

abstract:
  We present a large sample of H- and K-band spectra of 32 optically line
luminous central cluster galaxies. We find significant rovibrational H_2
emission in 23 of these galaxies as well as H recombination and/or [FeII]
emission in another 5. This represents a fourfold increase in the number of
molecular line detections known. A number of the detections are of extended
emission (5-20 kpc). In several objects we find significant [SiVI] emission
that appears to correlate with the strength of high ionization lines in the
optical (e.g. [OIII]). This comprehensive sample builds on previous work and
confirms that warm (1000-2500K) molecular hydrogen is present wherever there is
ionized material in the cores of cooling flows and in most cases it also
coincides with CO molecular line emission.


title: Spectral analysis of 35 GRBs/XRFs observed with HETE-2/FREGATE

abstract:
  We present a spectral analysis of 35 GRBs detected with the HETE-2 gamma-ray
detectors (the FREGATE instrument) in the energy range 7-400 keV. The GRB
sample analyzed is made of GRBs localized with the Wide Field X-ray Monitor
onboard HETE-2 or with the GRB Interplanetary Network. We derive the spectral
parameters of the time-integrated spectra, and present the distribution of the
low-energy photon index, alpha, and of the peak energy, e_peak . We then
discuss the existence and nature of the recently discovered X-Ray Flashes and
their relationship with classical GRBs.


title:
Report to Anaximander: A Dialogue on the Origin of the Cosmos in the
  Cradle of Western Civilization

abstract:
  The presentations in the 2nd Hellenic Cosmology Workshop covered a broad
range of cosmological subjects. Following the analogy with the architectural
masters of Ancient Greece, the contributions are presented in ``architectural''
sessions. The session on the ``Architects'' involves ``fundamental cosmology'',
focussing on the topology and geometry of our Universe and the fundamental
physical laws and processes at work in the first decisive moments of the (Very)
Early Universe. Following these cosmic blueprints, the ``Constructors'' set out
to present the ultimate realization of the cosmic framework. This concerns the
search for the best available estimates of the parameters characterizing the
Friedmann-Robertson-Walker metric. The specification of these cosmic measures
paves the way for the ``Interior Decorators'' to take care of the cosmic
``Infrastructure''. This involves the patterns and morphology of Megaparsec
scale cosmic structure and its emergence through gravitational instability, as
well as aspects concerning the rise of galaxies through the complex interplay
of gravitational, hydrodynamic, radiative, stellar and other dissipative
processes.


title: Exciting molecular hydrogen in the central galaxies of cooling flows

abstract:
  The origin of rovibrational H_2 emission in the central galaxies of cooling
flow clusters is poorly understood. Here we address this issue using data from
our near-infrared spectroscopic survey of 32 of the most line luminous such
systems, presented in the companion paper by Edge et al. (2002).
  We consider excitation by X-rays from the surrounding intracluster medium, UV
radiation from young stars, and shocks. The v=1-0 K-band lines with upper
levels within 10^4 K of the ground state appear to be mostly thermalised
(implying gas densities above ~10^5 cm^-3), with excitation temperatures
typically exceeding 2000K, as found earlier by Jaffe, Bremer and van der Werf
(2001). Together with the lack of strong v=2-0 lines in the H-band, this rules
out UV fluorescence.
  Using the CLOUDY photoionisation code, we deduce that the H_2 lines can
originate in a population of dense clouds, exposed to the same hot (T~50000K)
stellar continuum as the lower density gas which produces the bulk of the
forbidden optical line emission in the H-alpha luminous systems. This dense gas
may be in the form of self-gravitating clouds deposited directly by the cooling
flow, or may instead be produced in the high-pressure zones behind strong
shocks. Furthermore, the shocked gas is likely to be gravitationally unstable,
so collisions between the larger clouds may lead to the formation of globular
clusters.


title: Constraints on Models for TeV Gamma Rays from Gamma-Ray Bursts

abstract:
  We explore several models which might be proposed to explain recent possible
detections of high-energy (TeV) gamma rays in association with low-energy
gamma-ray bursts (GRBs). Likely values (and/or upper limits) for the source
energies in low- and high-energy gamma rays and hadrons are deduced for the
burst sources associated with possible TeV gamma-ray detections by the Project
GRAND array. Possible spectra for energetic gammas are deduced for three
models: 1) inverse-Compton scattering of ambient photons from relativistic
electrons; 2) proton-synchrotron emission; and 3) inelastic scattering of
relativistic protons from ambient photons creating high-energy neutral pions,
which decay into high-energy photons. These models rely on some basic
assumptions about the GRB properties, e.g. that: the low- and high-energy gamma
rays are produced at the same location; the time variability of the high-energy
component can be estimated from the FWHM of the highest peak in the low-energy
gamma ray light curve; and the variability-luminosity relation of Fenimore &
Ramirez-Ruiz (2000) gives a reliable estimate of the redshifts of these bursts.
We also explore the impact of each of these assumptions upon our models. We
conclude that the energetic requirements are difficult to satisfy for any of
these models unless, perhaps, either the photon beaming angle is much narrower
for the high-energy component than for the low-energy GRB or the bursts occur
at very low redshifts (z<0.01). Nevertheless, we find that the energetic
requirements are most easily satisfied if TeV gamma rays are produced
predominantly by inverse-Compton scattering with a magnetic field strength well
below equipartition or by proton-synchrotron emission with a magnetic field
strength near equipartition.


title: The Local Lyman-Alpha Forest: Absorbers in Galaxy Voids

abstract:
  We have conducted pointed redshift surveys for galaxies in the direction of
bright AGN whose HST far-UV spectra contain nearby (cz <~ 30,000 kms), low
column density (12.5 <= log N_{HI} (cm s^{-2}) <= 14.5) Ly-alpha forest
absorption systems. Here we present results for four lines-of-sight which
contain nearby (cz <~ 3000 kms) Ly-alpha absorbers in galaxy voids. Although
our data go quite deep (-13 <= M_{B}(limit) <= -14) out to impact parameters of
100-250 h_{70}^{-1} kpc, these absorbers remain isolated and thus appear to be
truly intergalactic, rather than part of galaxies or their halos. Since we and
others have discovered no galaxies in voids, the only baryons detected in the
voids are in the Ly-alpha ``clouds''. Using a photoionization model for these
clouds, the total baryonic content of the voids is 4.5% +/- 1.5% of the mean
baryon density.


title:
Constraints on ultra-high energy neutrinos from optically thick
  astrophysical accelerators

abstract:
  The Z-burst mechanism invoked to explain ultra-high energy cosmic rays is
severely constrained by measurements of the cosmic gamma-ray background by
EGRET. We discuss the case of optically thick sources and show that jets and
hot spots of active galaxies cannot provide the optical depth required to
suppress the photon flux. Other extragalactic accelerators (AGN cores and sites
of gamma ray bursts), if they are optically thick, could be tested by future
measurements of the secondary neutrino flux.


title:
Spectropolarimetry of the Type Ic SN 2002ap in M74: More Evidence for
  Asymmetric Core Collapse

abstract:
  High-quality spectropolarimetric data of SN 2002ap were obtained with the ESO
Very Large Telescope Melipal (+ FORS1) at 3 epochs that correspond to -6, -2,
and +1 days for a V maximum of 9 Feb 2002. The polarization spectra show three
distinct broad features at 400, 550, and 750 nm that evolve in shape, amplitude
and orientation in the Q-U plane. The continuum polarization grows from nearly
zero to ~0.2 percent. The 750 nm feature is polarized at a level > 1 %. We
identify the 550 and 750 nm features as Na I D and OI 777.4 nm moving at about
20,000 km/s. The blue feature may be Fe II. We interpret the polarization
evolution in terms of the impact of a bipolar flow from the core that is
stopped within the outer envelope of a carbon/oxygen core. Although the
symmetry axis remains fixed, as the photosphere retreats by different amounts
in different directions due to the asymmetric velocity flow and density
distribution, geometrical blocking effects in deeper, Ca-rich layers can lead
to a different dominant axis in the Q-U plane. We conclude that the features
that characterize SN 2002ap, specifically its high velocity, can be accounted
for in an asymmetric model with a larger ejecta mass than SN 1994I such that
the photosphere remains longer in higher velocity material. The characteristics
of "hypernovae" may be the result of orientation effects in a mildly
inhomogeneous set of progenitors, rather than requiring an excessive total
energy or luminosity. In the analysis of asymmetric events with spherically
symmetric models, it is probably advisable to refer to "isotropic equivalent"
energy, luminosity, ejected mass, and nickel mass.


title: A Candidate M31/M32 Intergalactic Microlensing Event

abstract:
  We report the discovery of a microlensing candidate projected 2'54" from the
center of M32, on the side closest to M31. The blue color (R-I= 0.00 +/- 0.14)
of the source argues strongly that it lies in the disk of M31, while the
proximity of the line of sight to M32 implies that this galaxy is the most
likely host of the lens. If this interpretation is correct, it would confirm
previous arguments that M32 lies in front of M31. We estimate that of order one
such event or less should be present in the POINT-AGAPE data base. If more
events are discovered in this direction in a dedicated experiment, they could
be used to measure the mass function of M32 up to an unknown scale factor. By
combining microlensing observations of a binary-lens event with a measurement
of the M31-M32 relative proper motion using the astrometric satellites SIM or
GAIA, it will be possible to measure the physical separation of M31 and M32,
the last of the six phase-space coordinates needed to assign M32 an orbit.


title: Second Moment of Halo Occupation Number

abstract:
  The halo approach to large scale structure provides a physically motivated
model to understand clustering properties of galaxies. An important aspect of
the halo model involves a description on how galaxies populate dark matter
halos or what is now called the halo occupation distribution. We discuss a way
in which clustering information, especially in the non-linear regime, can be
used to determine moments of this halo occupation number. We invert the
non-linear part of the real space power spectrum from the PSCz survey to
determine the second moment of the halo occupation distribution in a model
independent manner. The precise measurement of higher order correlations can
eventually be used to determine successive higher order moments of this
distribution.


title:
Cosmological Effects of the First Stars: Evolving Spectra of Population
  III

abstract:
  The first stars hold intrinsic interest for their uniqueness and for their
potential importance to galaxy formation, chemical enrichment, and feedback on
the intergalactic medium (IGM). The metal-free composition of the first stars
restricts the stellar energy source to proton-proton burning rather than the
more efficient CNO cycle. Consequently they are hotter, smaller, and have
harder spectra than their present-day counterparts of finite metallicity. We
present new results from a continuing study of metal-free stars from a
cosmological point of view. We have calculated evolving spectra of Pop III
clusters, derived from a grid of zero-metallicity stellar evolutionary tracks.
We find that H-ionizing photon production from metal-free stellar clusters
takes twice as long as that of Pop II to decline to 1/10 its peak value. In
addition, metal-free stars produce substantially more photons than Pop II in
the HeII ($E > 4$ Ryd) continuum. We suggest that large Ly$\alpha$ equivalent
widths ($W_{\rm Ly\alpha} > 400$ Angstroms) may provide a means of detecting
metal-free stellar populations at high redshift, and that HeII recombination
lines ($\lambda$1640, $\lambda$4686) may confirm identifications of Population
III. While Pop III clusters are intrinsically bluer than their Pop II
counterparts, nebular continuum emission makes up this difference and may
confuse attempts to discern Pop III stars with broadband colors. In a companion
paper, we explore the consequences of evolving spectra of Pop III for the
reionization of the IGM in both H and He. (ABRIDGED)


title:
Evolving Spectra of Pop III Stars: Consequences for Cosmological
  Reionization

abstract:
  We examine the significance of the first metal-free stars (Pop III) for the
cosmological reionization of HI and HeII. These stars have unusually hard
spectra, with the integrated ionizing photon rates from a Pop III stellar
cluster for HI and HeII being 1.6 and $10^5$ times stronger respectively than
those from a Pop II cluster. For the currently favored cosmology, we find that
Pop III stars alone can reionize HI and HeII at redshifts, $z$ of about 9 (4.7)
and 5.1 (0.7) for continuous (instantaneous) modes of star formation. More
realistic scenarios involving combinations of Pop III and Pop II stellar
spectra yield similar results for hydrogen. Helium never reionizes completely
in these cases; the ionization fraction of HeIII reaches a maximum of about 60
percent at $z$ of about 5.6 if Pop III star formation lasts for $10^9$ yr.
Future data on HI reionization can test the amount of small-scale power
available to the formation of the first objects, and provide a constraint on
values of $\sigma_8$ less than or about 0.7. Since current UV observations
indicate an epoch of reionization for HeII at $z$ of about 3, HeII may reionize
more than once. Measurements of the HeII Gunn-Peterson effect in the
intergalactic medium at redshifts exceeding about 3 may reveal the significance
of Pop III stars for HeII reionization, particularly in void regions that may
contain relic ionization from early Pop III stellar activity.


title: The Population of the Galactic Plane as Seen by MSX

abstract:
  The combination of mid-infrared data from the MSX satellite mission and
ground-based near-infrared photometry is used to characterise the properties of
the mid-infrared population of the Galactic plane. The colours of the youngest
sources still heavily embedded within their natal molecular clouds are in
general different from evolved stars shrouded within their own dust shells. Our
main motivation is to use MSX for an unbiased search for a large (~1000) sample
of massive young stellar objects (MYSOs). A simple analysis shows that the MSX
point source catalogue should contain most of the MYSOs within our Galaxy. We
develop colour selection criteria using combined near- and mid-infrared data
for MYSOs, which produces a list of 3071 objects, excluding the galactic centre
region. The programme of follow-up observations already underway to separate
the MYSOs from compact H II regions and other remaining objects is briefly
described. We also show that these data can be used, just as IRAS data has been
previously, to provide a separation between evolved stars with carbon rich and
oxygen rich dust. These data may also be used to search for evidence of dust
around normal main sequence stars, such as low mass pre-main sequence stars or
the Vega-excess class of objects where debris disks are presumed to remain from
the planet formation process. We discuss the accuracy and completeness of the
MSX point source catalogue, and show that the errors present tend to be of a
kind that is not significant for the main stellar populations we discuss in
this paper.


title: Collapsar Uncorking and Jet Eruption in GRB

abstract:
  We show that the collapsar model of gamma-ray bursts results in a series of
successive shocks and rarefaction waves propagating in the "cork" of stellar
material being pushed ahead of the jet, as it emerges from the massive stellar
progenitor. These shocks result in a series of characteristic, increasingly
shorter and harder thermal X-ray pulses, as well as a non-thermal gamma-ray
pulse, which precede the usual non-thermal MeV gamma-rays. We consider jets
escaping from both compact (CO or He dwarf) and blue supergiant stellar
progenitors. The period, fluence and hardness of the pulses serves as a
diagnostic for the size and density of the outer envelope of the progenitor
star.


title:
Cosmological SPH simulations: A hybrid multi-phase model for star
  formation

abstract:
  We present a model for star formation and supernova feedback that describes
the multi-phase structure of star forming gas on scales that are typically not
resolved in cosmological simulations. Our approach includes radiative heating
and cooling, the growth of cold clouds embedded in an ambient hot medium, star
formation in these clouds, feedback from supernovae in the form of thermal
heating and cloud evaporation, galactic winds and outflows, and metal
enrichment. Implemented using SPH, our scheme is a significantly modified and
extended version of the grid-based method of Yepes et al. (1997), and enables
us to achieve high dynamic range in simulations of structure formation. We
discuss properties of the feedback model in detail and show that it predicts a
self-regulated, quiescent mode of star formation, which, in particular,
stabilises the star forming gaseous layers of disk galaxies. The
parameterisation of this mode can be reduced to a single free quantity which
determines the overall timescale for star formation. We fix this parameter to
match the observed rates of star formation in local disk galaxies. When
normalised in this manner, cosmological simulations nevertheless overproduce
the observed cosmic abundance of stellar material. We are thus motivated to
extend our feedback model to include galactic winds associated with star
formation. Using small-scale simulations of individual star-forming disk
galaxies, we show that these winds produce either galactic fountains or
outflows, depending on the depth of the gravitational potential. Moreover,
outflows from galaxies in these simulations drive chemical enrichment of the
intergalactic medium, in principle accounting for the presence of metals in the
Lyman alpha forest. (abridged)


title:
Stability and heating of magnetically driven jets from Keplerian
  accretion discs

abstract:
  We have performed 3-D numerical magnetohydrodynamic (MHD) jet experiments to
study the instabilities associated with strongly toroidal magnetic fields and
determine if such magnetic configurations in jets are as unstable as similar
situations are found to be in the laboratory and in analytical estimates. A
perfectly conducting Keplerian disc with fixed density, rotational velocity and
pressure is used as a lower boundary for the jet. The energy equation is
solved, with the inclusion of self-consistently computed heating by viscous and
magnetic dissipation. The resulting jets evolve into time-dependent,
non-axisymmetric configurations, but we find only minor disruption of the jets
by for example the kink instability. We find that magnetic dissipation may have
profound effects on the jet flow as: 1) it turns on in highly wound up magnetic
field regions and helps to prevent critical kink situations; 2) it influences
jet dynamics by re-organizing the magnetic field structure and increasing
thermal pressure in the jet; and 3) it influences mass loading by increasing
temperature and pressure at the base of the jet.


title: The history of star formation in a LCDM universe

abstract:
  Employing hydrodynamic simulations of structure formation in a LCDM
cosmology, we study the history of cosmic star formation from the "dark ages"
at redshift z~20 to the present. In addition to gravity and ordinary
hydrodynamics, our model includes radiative heating and cooling of gas, star
formation, supernova feedback, and galactic winds. By making use of a
comprehensive set of simulations on interlocking scales and epochs, we
demonstrate numerical convergence of our results on all relevant halo mass
scales, ranging from 10^8 to 10^15 Msun/h. The predicted density of cosmic star
formation is broadly consistent with measurements, given observational
uncertainty. From the present epoch, it gradually rises by about a factor of
ten to a peak at z~5-6, which is beyond the redshift range where it has been
estimated observationally. 50% of the stars are predicted to have formed by
redshift z~2.1, and are thus older than 10.4 Gyr, while only 25% form at
redshifts lower than z~1. The mean age of all stars at the present is about 9
Gyr. Our model predicts a total stellar density at z=0 of Omega_*=0.004,
corresponding to about 10% of all baryons being locked up in long-lived stars,
in agreement with recent determinations of the luminosity density of the
Universe. We determine the "multiplicity function of cosmic star formation" as
a function of redshift; i.e. the distribution of star formation with respect to
halo mass. We also briefly examine possible implications of our predicted star
formation history for reionisation of hydrogen in the Universe. We find that
the star formation rate predicted by the simulations is sufficient to account
for hydrogen reionisation by z~6, but only if a high escape fraction close to
unity is assumed. (abridged)


title: HI Narrow Line Absorption in Dark Clouds

abstract:
  We have used the Arecibo telescope to carry out an survey of 31 dark clouds
in the Taurus/Perseus region for narrow absorption features in HI ($\lambda$
21cm) and OH (1667 and 1665 MHz) emission. We detected HI narrow
self--absorption (HINSA) in 77% of the clouds that we observed. HINSA and OH
emission, observed simultaneously are remarkably well correlated. Spectrally,
they have the same nonthermal line width and the same line centroid velocity.
Spatially, they both peak at the optically--selected central position of each
cloud, and both fall off toward the cloud edges. Sources with clear HINSA
feature have also been observed in transitions of CO, \13co, \c18o, and CI.
HINSA exhibits better correlation with molecular tracers than with CI.
  The line width of the absorption feature, together with analyses of the
relevant radiative transfer provide upper limits to the kinetic temperature of
the gas producing the HINSA. Some sources must have a temperature close to or
lower than 10 K. The correlation of column densities and line widths of HINSA
with those characteristics of molecular tracers suggest that a significant
fraction of the atomic hydrogen is located in the cold, well--shielded portions
of molecular clouds, and is mixed with the molecular gas.
  The average number density ratio [HI]/[\h2] is $1.5\times10^{-3}$. The
inferred HI density appears consistent with but is slightly higher than the
value expected in steady state equilibrium between formation of HI via cosmic
ray destruction of H$_2$ and destruction via formation of H$_2$ on grain
surfaces. The distribution and abundance of atomic hydrogen in molecular clouds
is a critical test of dark cloud chemistry and structure, including the issues
of grain surface reaction rates, PDRs, circulation, and turbulent diffusion.


title: A Spectroscopic Study of the Peculiar Galaxy UGC 5600

abstract:
  We present our observations of the galaxy UGS 5600 with a long-slit
spectrograph (UAGS) and a multi-pupil field spectrograph (MPFS) using the 6-m
telescope at Special Astrophysical Observatory. Radial-velocity fields of the
stellar and gaseous components were constructed for the central region and
inner ring of the galaxy. We proved the existence of two almost orthogonal
kinematic subsystems and conclude that UGC 5600 is a galaxy with an inner polar
ring. In the circumnuclear region, we detected noncircular stellar motions and
suspected the existence of a minibar. The emission lines are shown to originate
in H II regions. We estimated the metallicity from the intensity ratio of the
[NII]$\lambda6583$ and \Ha lines to be nearly solar, which rules out the
possibility that the polar ring was produced by the accretion of gas from a
dwarf companion.


title: Dense Molecular Gas and Star Formation in Nearby Seyfert Galaxies

abstract:
  An imaging survey of CO(1-0), HCN(1-0), and HCO$^+$(1-0) lines in the centers
of nearby Seyfert galaxies has been conducted using the Nobeyama Millimeter
Array and the RAINBOW interferometer. Preliminary results reveal that 3
Seyferts out of 7 show abnormally high HCN/CO and HCN/HCO$^+$ ratios, which
cannot occur even in nuclear starburst galaxies. We suggest that the enhanced
HCN emission originated from X-ray irradiated dense obscuring tori, and that
these molecular line ratios can be a new diagnostic tool to search for ``pure''
AGNs. According to our HCN diagram, we suggest that NGC 1068, NGC 1097, and NGC
5194 host ``pure'' AGNs, whereas Seyfert nuclei of NGC 3079, NGC 6764, and NGC
7469 may be ``composite'' in nature.


title: The secondary minimum in YY Her: Evidence for a tidally distorted giant

abstract:
  We present and analyze quiescent UBVRI light curves of the classical
symbiotic binary YY Her. We show that the secondary minimum, which is clearly
visible only in the quiescent VRI light curves, is due to ellipsoidal
variability of the red giant component. Our simple light curve analysis, by
fitting of the Fourier cosine series, resulted in a self-consistent
phenomenological model of YY Her, in which the periodic changes can be
described by a combination of the ellipsoidal changes and a sinusoidal changes
of the nebular continuum and line emission.


title:
Diffuse and Gravitationally Stable Molecular Gas in the Post-Starburst
  Galaxy NGC 5195

abstract:
  The Nobeyama Millimeter Array (NMA) has been used to make aperture synthesis
CO(1-0) observations of the post-starburst galaxy NGC 5195. CO(1-0) and
HCN(1-0) observations of NGC 5195 using the Nobeyama 45 m telescope are also
presented. High-resolution (1".9 x 1".8 or 86 pc x 81 pc at D = 9.3 Mpc) NMA
maps show a strong concentration of CO emission toward the central a few 100 pc
region of NGC 5195, despite the fact that the current massive star formation is
suppressed there. The HCN-to-CO integrated intensity ratio on the brightness
temperature scale, R_{HCN/CO}, is about 0.02 within the central r < 400 pc
region. This R_{HCN/CO} is smaller than those in starburst regions by a factor
of 5 - 15. These molecular gas properties would explain why NGC 5195 is in a
post-starburst phase; most of the dense molecular cores (i.e., the very sites
of massive star formation) have been consumed away by a past starburst event,
and therefore a burst of massive star formation can no longer last, although a
large amount of low density gas still exists. We propose that dense molecular
gas can not be formed from remaining diffuse molecular gas because the
molecular gas in the center of NGC 5195 is too stable to form dense cores via
gravitational instabilities of diffuse molecular gas.


title: Reformulation of Smoothed Particle Hydrodynamics with Riemann Solver

abstract:
  Smoothed Particle Hydrodynamics is reformulated in terms of the convolution
of the original hydrodynamics equations, and the new evolution equations for
the particles are derived. The same evolution equation of motion is also
derived using a new action principle. The force acting on each particle is
determined by solving the Riemann problem. The use of the Riemann Solver
strengthens the method, making it accurate for the study of phenomena with
strong shocks. The prescription for the variable smoothing length is shown.
These techniques are implemented in strict conservation form. The results of a
few test problems are also shown.


title: Study of Spectral Lag for Short GRBs

abstract:
  This paper reports statistically significant correlations between various
burst parameters, observed in a sample of 156 GRBs belonging to BATSE 4B
catalog with T90 less than 2 s. The number of subpulses in a burst is strongly
correlated not only with the object's duration but also with its fluence and
hardness ratio, suggesting that when the central engine is more powerful,
ejecting matter with typically higher values of Lorentz factor, the bulk energy
is dissipated on longer time scales in the form of larger number of gamma
pulses. We estimate hard-to-soft lag in bursts by taking the difference between
centroids corresponding to time profiles at energies $> 100$ keV and $<100$
keV. The number of short GRBs that show soft-to-hard spectral evolution is
slightly over one quarter of the total, in the sample considered here. Bursts
that exhibit hard-to-soft spectral change appear to form a distinct class, with
strength as well as hardness of individual subpeaks tending to decrease with
peak position. Opposite is true for objects with softer photons arriving
earlier than the harder ones, implying some kind of a rejuvenation of the
central engine (may be due to enhanced accretion of matter towards the end).
The two classes also show other diverging trends. For instance, objects
belonging to the larger of the two classes display strong correlations between
spectral lag and the fluence, the hardness ratio as well as the number of
pulse, respectively. While no such correlations are seen in bursts that evolve
from soft to hard. However, the magnitude of lag is strongly correlated with
burst duration in both the classes.


title:
Age, Metallicity and Star Formation History of Cluster Galaxies at z~0.3
  F

abstract:
  We investigate the color-magnitude distribution in the rich cluster AC 118 at
z=0.31. The sample is selected by the photometric redshift technique, allowing
to study a wide range of properties of stellar populations, and is complete in
the K-band, allowing to study these properties up to a given galaxy mass. We
use galaxy templates based on population synthesis models to translate the
physical properties of the stellar populations - formation epoch, time-scale of
star formation, and metallicity - into observed magnitudes and colors. In this
way we show that a sharp luminosity-metallicity relation is inferred without
any assumption on the galaxy formation scenario (either monolithic or
hierarchical). Our data exclude significant differences in star formation
histories along the color-magnitude relation, and therefore confirm a pure
metallicity interpretation for its origin, with an early (z~5) formation epoch
for the bulk of stellar populations. The dispersion in the color-magnitude
diagram implies that fainter galaxies in our sample (K~18) ceased to form stars
as late as z~0.5, in agreement with the picture that these galaxies were
recently accreted into the cluster environment. The trend with redshift of the
total stellar mass shows that half of the luminous mass in AC 118 was already
formed at $z~2, but also that 20% of the stars formed at z<1.


title: Gravitational Radiation from Intermediate-Mass Black Holes

abstract:
  Recent X-ray observations of galaxies with ROSAT, ASCA, and Chandra have
revealed numerous bright off-center point sources which, if isotropic emitters,
are likely to be intermediate-mass black holes, with hundreds to thousands of
solar masses. The origin of these objects is under debate, but observations
suggest that a significant number of them currently reside in young
high-density stellar clusters. There is also growing evidence that some
Galactic globular clusters harbor black holes of similar mass, from
observations of stellar kinematics. In such high-density stellar environments,
the interactions of intermediate-mass black holes are promising sources of
gravitational waves for ground-based and space-based detectors. Here we explore
the signal strengths of binaries containing intermediate-mass black holes or
stellar-mass black holes in dense stellar clusters. We estimate that a few to
tens per year of these objects will be detectable during the last phase of
their inspiral with the advanced LIGO detector, and up to tens per year will be
seen during merger, depending on the spins of the black holes. We also find
that if these objects reside in globular clusters then tens of sources will be
detectable with LISA from the Galactic globular system in a five year
integration, and similar numbers will be detectable from more distant galaxies.
The signal strength depends on the eccentricity distribution, but we show that
there is promise for strong detection of pericenter precession and
Lense-Thirring precession of the orbital plane. We conclude by discussing what
could be learned about binaries, dense stellar systems, and strong gravity if
such signals are detected.


title:
Errata: The X-Ray Emission Measure (EM) of the Young Stellar Objects
  (YSOs) in the Rho Ophiuchi (Rho Oph) and Monoceros R2 Dark Clouds (Mon R2)

abstract:
  Errors were made in the calculations of EMs using the best fit normalizations
in XSPEC. Lists of the errors and corrections are as follows.
  (1)Tables 1, 3, and 4 in ApJ, 557, 747 and astro-ph/0104190 (YSOs in Rho
Oph): All the EMs in these tables should be multiplied by pi; the log(EM) in
the first raw in Table 1, for example, is 52.6(52.2--53.2), not
52.1(51.7--52.7).
  (2)Figures 7 and 9 in ApJ, 557, 747 and astro-ph/0104190 (YSOs in Rho Oph):
The EM plots should be systematically up-shifted by the factor of pi.
  (3)Table 3 in ApJ, 563, 361 and astro-ph/0108078 (young brown dwarfs in Rho
Oph): All the EMs in this table should be multiplied by pi; the log(EM) in the
first raw, for example, is 52.1(52.0--52.6), not 51.6(51.5--52.1).
  (4)Table 1 in ApJ, 567, 423 and astro-ph/0110462 (YSOs in Mon R2): All the
EMs in this table should be divided by 10; the log(EM) in the first raw, for
example, is 52.5(52.1--52.9), not 53.5(53.1--53.9).
  All the spectral parameters except EM are unchanged. These errors of EM do
not affect any of the conclusions of the relevant papers.
  In addition, Gregorio-Hetem, J., Montmerle, T., Casanova, S., and Feigelson,
E. D.1998, A&A, 331, 193 should be included in the reference list of ApJ, 567,
423 (astro-ph/0110462).


title:
Observations of Mira stars with the IOTA/FLUOR interferometer and
  comparison with Mira star models

abstract:
  We present K'-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR fiber optics
beam combiner, which provides high-accuracy visibility measurements in spite of
time-variable atmospheric conditions. For the M-type Miras X Oph, R Aql, RU
Her, R Ser, and the C-type Mira V CrB we derived the uniform-disk diameters
11.7mas, 10.9mas, 8.4mas, 8.1mas, and 7.9mas (+/- 0.3mas), respectively.
Simultaneous photometric observations yielded the bolometric fluxes. The
derived angular Rosseland radii and the bolometric fluxes allowed the
determination of effective temperatures. For instance, the effective
temperature of R Aql was determined to be 2970 +/- 110 K. A linear Rosseland
radius for R Aql of (250 +100/-60) Rsun was derived from the angular Rosseland
radius of 5.5mas +/- 0.2mas and the HIPPARCOS parallax of 4.73mas +/- 1.19mas.
The observations were compared with theoretical Mira star models of Bessel et
al. (1996) and Hofmann et al. (1998). The effective temperatures of the M-type
Miras and the linear radius of R Aql indicate fundamental mode pulsation.


title: The galactic foreground angular spectra

abstract:
  Galactic synchrotron and free-free foregrounds angular spectra are
analytically estimated with account for interstellar turbulence and radiating
process physics. Unknown parameters of the spectra are obtained by fitting to
observational data.


title: On the Origin of the Circular and Hexagonal Formations in Galaxies

abstract:
  The round and arc-shaped formations are known in some galaxies, the Bubble
complex (the Hodge object) in NGC 6946 being the most remarkable. The rim of
the complex has a form of a regular arc in which a part of a hexagonal
structure is embedded. A similar morphology is recognized in NGC 7421 galaxy,
in that part of its rim which is leading in the galaxy motion through the
intergalactic gas, as suggested by the bow-shock appearance of the HI halo of
the galaxy. A hexagonal shape is also found in NGC4676A galaxy. The HII radial
velocities across the Bubble complex are compatible with its retrograde
rotation and drift, which are characteristic for solitary vortices known in
nonlinear hydrodynamics. The drift motion may explain the location of the
Bubble complex at the tip of the largest elliptical HI hole in NGC 6946. The
hexagonal vortices in the atmospheres of Jupiter and Saturn are within the gas
streams what seems to be suggestive as well. It is conjectured that the
hexagonal rims of stellar systems might be relics of flat segments of the shock
wave produced by the ram pressure. The giant stellar arcs in NGC 300 and M33
are associated with the energetic X-ray sources P42 and X-4 respectively (fig.
11), and these might be the relics of Hypernovae.


title: SNOC: a Monte-Carlo simulation package for high-z supernova observations

abstract:
  We present a Monte-Carlo package for simulation of high-redshift supernova
data, SNOC. Optical and near-infrared photons from supernovae are ray-traced
over cosmological distances from the simulated host galaxy to the observer at
Earth. The distances to the sources are calculated from user provided
cosmological parameters in a Friedmann-Lemaitre universe, allowing for
arbitrary forms of ``dark energy''. The code takes into account gravitational
interactions (lensing) and extinction by dust, both in the host galaxy and in
the line-of-sight. The user can also choose to include exotic effects like a
hypothetical attenuation due to photon-axion oscillations. SNOC is primarily
useful for estimations of cosmological parameter uncertainties from studies of
apparent brightness of Type Ia supernovae vs redshift, with special emphasis on
potential systematic effects. It can also be used to compute standard
cosmological quantities like luminosity distance, lookback time and age of the
universe in any Friedmann-Lemaitre model with or without quintessence.


title:
IRC+10216 in Action: Present Episode of Intense Mass-Loss Reconstructed
  by Two-Dimensional Radiative Transfer Modeling

abstract:
  We present two-dimensional (2D) radiative transfer modeling of IRC+10216 at
selected moments of its evolution in 1995-2001, which correspond to three
epochs of our series of 8 near-infrared speckle images (Osterbart et al. 2000,
Weigelt et al. 2002). The high-resolution images obtained over the last 5.4
years revealed the dynamic evolution of the subarcsecond dusty environment of
IRC+10216 and our recent time-independent 2D radiative transfer modeling
reconstructed its physical properties at the single epoch of January 1997
(Men'shchikov et al. 2001). Having documented the complex changes in the
innermost bipolar shell of the carbon star, we incorporate the evolutionary
constraints into our new modeling to understand the physical reasons for the
observed changes. The new calculations imply that during the last 50 years, we
have been witnessing an episode of a steadily increasing mass loss from the
central star, from Mdot ~ 10^-5 Msun/yr to the rate of Mdot ~ 3x10^-4 Msun/yr
in 2001. The rapid increase of the mass loss of IRC+10216 and continuing
time-dependent dust formation and destruction caused the observed displacement
of the initially faint components C and D and of the bright cavity A from the
star which has almost disappeared in our images in 2001. Increasing dust
optical depths are causing strong backwarming that leads to higher temperatures
in the dust formation zone, displacing the latter outward with a velocity v_T ~
27 km/s due to the evaporation of the recently formed dust grains. This shift
of the dust density peak in the bipolar shell mimics a rapid radial expansion,
whereas the actual outflow has probably a lower speed v < v_inf ~ 15 km/s. The
model predicts that the star will remain obscured until Mdot starts to drop
back to lower values in the dust formation zone.


title: NGC 3628: Ejection Activity Associated with Quasars

abstract:
  NGC3628 is a well-studied starburst/low level AGN galaxy in the Leo Triplet
noted for its extensive outgassed plumes of neutral hydrogen. QSOs are shown to
be concentrated around NGC3628 and aligned with the HI plumes. The closest high
redshift quasar has z=2.15 and is at the tip of an X-ray filament emerging
along the minor axis HI plume. Location at this point has an accidental
probability of ~2x10^-4. In addition a coincident chain of optical objects
coming out along the minor axis ends on this quasar. More recent measures on a
pair of strong X-ray sources situated at 3.2 and 5.4 arcmin on either side of
NGC3628 along its minor axis, reveal that they have nearly identical redshifts
of z=0.995 and 0.981. The closer quasar lies directly in the same X-ray
filament which extends from the nucleus out 4.1 arcmin to end on the quasar of
z=2.15. The chain of objects SW along the minor axis of NGC3628 has been imaged
in four colors with the VLT. Images and spectra of individual objects within
the filament are reported. It is suggested that material in various physical
states and differing intrinsic redshifts is ejected out along the minor axis of
this active, disturbed galaxy.


title: The XMM-Newton Science Archive

abstract:
  The XMM-NEWTON Science Archive (XSA) is being developed within the XMM-NEWTON
Science Operations Centre at the ESA VILSPA Satellite Tracking Station of
Villafranca del Castillo, near Madrid in Spain. The first public version was
released on April 15, 2002.
  Based on the ISO Data Archive architecture and design, the XSA is accessible
from the World Wide Web through a Java interface at
http://xmm.vilspa.esa.es/xsa that allows: - powerful and complex queries
against the observations and exposure catalogue for the first release and
against the source catalogue in future releases - configurable results display,
including product visualization tools - customisable product retrieval via a
shopping basket - selection of product level - product retrieval via FTP or
CDROM - proprietary rights protection for both display and data request
  The XSA will also be ready to provide inter-operability with other archives
and applications.


title:
Faint High Latitude Carbon Stars Discovered by the Sloan Digital Sky
  Survey: Methods and Initial Results

abstract:
  We report the discovery of 39 Faint High Latitude Carbon Stars (FHLCs) from
Sloan Digital Sky Survey commissioning data. The objects, each selected
photometrically and verified spectroscopically, range over 16.6 < r* < 20.0,
and show a diversity of temperatures as judged by both colors and NaD line
strengths. At the completion of the Sloan Survey, there will be many hundred
homogeneously selected and observed FHLCs in this sample. We present proper
motion measures for each object, indicating that the sample is a mixture of
extremely distant (>100 kpc) halo giant stars, useful for constraining halo
dynamics, plus members of the recently-recognized exotic class of very nearby
dwarf carbon (dC) stars. Motions, and thus dC classification, are inferred for
40-50 percent of the sample, depending on the level of statistical significance
invoked. The new list of dC stars presented here, although selected from only a
small fraction of the final SDSS, doubles the number of such objects found by
all previous methods. (Abstract abridged).


title: Extensive Air Shower Simulations at the Highest Energies

abstract:
  Air shower simulation programs are essential tools for the analysis of data
from cosmic ray experiments and for planning the layout of new detectors. They
are used to estimate the energy and mass of the primary particle. Unfortunately
the model uncertainties translate directly into systematic errors in the energy
and mass determination. Aiming at energies $> 10^{19}$ eV, the models have to
be extrapolated far beyond the energies available at accelerators. On the other
hand, hybrid measurement of ground particle densities and calorimetric shower
energy, as will be provided by the Pierre Auger Observatory, will strongly
constrain shower models. While the main uncertainty of contemporary models
comes from our poor knowledge of the (soft) hadronic interactions at high
energies, also electromagnetic interactions, low-energy hadronic interactions
and the particle transport influence details of the shower development. We
review here the physics processes and some of the computational techniques of
air shower models presently used for highest energies, and discuss the
properties and limitations of the models.


title:
Abell 1451 and 1RXS J131423.6-251521: a multi-wavelength study of two
  dynamically perturbed clusters of galaxies

abstract:
  We present results from optical, X-ray and radio observations of two X-ray
bright (L_X ~ 10^{45} erg/s) galaxy clusters. A1451 is at redshift z=0.1989 and
has line-of-sight velocity dispersion sigma_v = 1330 km/s as measured from 57
cluster galaxies. It has regular X-ray emission without signs of substructure,
a Gaussian velocity distribution, lack of a cooling flow region and significant
deviations from the observed scaling laws between luminosity, temperature and
velocity dispersion, indicating a possible merging shock. There is only one
spectroscopically confirmed cluster radio galaxy, which is close to the X-ray
peak. 1RXS J131423.6-251521 has z=0.2474 and sigma_v = 1100 km/s from 37
galaxies. There are two distinct galaxy groups with a projected separation of
\~700 kpc. The velocity histogram is bi-modal with a redshift-space separation
of ~1700 km/s, and the X-ray emission is double peaked. Although there are no
spectroscopically confirmed cluster radio galaxies, we have identified a
plausible relic source candidate.


title: The Mg-sigma Relation and the Genesis of Early-Type Galaxies

abstract:
  Available data on the magnesium - velocity dispersion (Mg-sigma) relation for
\~2000 early-type galaxies is collected and compared. As noted previously, the
Mg residuals from a fitted line are roughly Gaussian near the mean but have an
asymmetric blue tail, probably from subpopulations of relatively young stars.
We define statistics for scatter and asymmetry of scatter in the Mg dimension
and find impressive uniformity among data sets. We construct models of galaxy
formation built to be as unbiased as possible toward the question of the
importance of mergers in the formation of early type galaxies. The
observational constraints (Mg-sigma width, asymmetry, and mean Mg strength,
plus mean age and width of abundance distribution) are severe enough to
eliminate almost all of models. Among the casualties are: models with merger
rates proportional to (1+z)^n with n>0, models that assume early formation
followed by recent drizzling of new stars, merger-only models where the number
of mergers exceeds ~80, merger-only models with less than ~20 mergers, and
models with a cold dark matter power spectrum even with biasing included. The
most successful models were those with merger probability constant with time,
with the number of mergers needed to form the galaxy around 40. These models
are characterized by mean light-weighted ages of 7-10 Gyr (consistent with
spectroscopic studies), a narrow abundance distribution, and a lookback time
behavior nearly indistinguishable from passive evolution of old stellar
populations.


title:
X-Ray Spectroscopy of the Low-Mass X-ray Binaries 2S 0918-549 and
  4U1543-624: Evidence for Neon-Rich Degenerate Donors

abstract:
  We present high-resolution spectroscopy of the neutron-star/low-mass X-ray
binaries 2S 0918-549 and 4U 1543-624 with the High Energy Transmission Grating
Spectrometer onboard the Chandra X-ray Observatory and the Reflection Grating
Spectrometer onboard XMM-Newton. Previous low-resolution spectra of both
sources showed a broad line-like feature at 0.7 keV that was originally
attributed to unresolved line emission. We recently showed that this feature
could also be due to excess neutral Ne absorption, and this is confirmed by the
new high-resolution Chandra spectra. The Chandra spectra are each well fit by
an absorbed power-law + blackbody model with a modified Ne/O number ratio of
0.52+/-0.12 for 2S 0918-549 and 1.5+/-0.3 for 4U 1543-624, compared to the
interstellar-medium value of 0.18. The XMM spectrum of 2S 0918-549 is best fit
by an absorbed power-law model with a Ne/O number ratio of 0.46+/-0.03,
consistent with the Chandra result. On the other hand, the XMM spectrum of 4U
1543-624 is softer and less luminous than the Chandra spectrum and has a
best-fit Ne/O number ratio of 0.54+/-0.03. The difference between the measured
abundances and the expected interstellar ratio, as well as the variation of the
column densities of O and Ne in 4U 1543-624, supports the suggestion that there
is absorption local to these binaries. We propose that the variations in the O
and Ne column densities of 4U 1543-624 are caused by changes in the ionization
structure of the local absorbing material. It is important to understand the
effect of ionization on the measured absorption columns before the abundance of
the local material can be determined. This work supports our earlier suggestion
that 2S 0918-549 and 4U 1543-624 are ultracompact binaries with Ne-rich
companions.


title:
XMM-Newton observations of ultraluminous X-ray sources in nearby
  galaxies

abstract:
  An XMM-Newton study of ultraluminous X-ray sources (ULX) has been performed
in a sample of 10 nearby Seyfert galaxies. Eighteen ULX have been found with
positional uncertainty of about 4". The large collecting area of XMM-Newton
makes the statistics sufficient to perform spectral fitting with simple models
in 8 cases. The main results of the present minisurvey strengthen the theory
that the ULX could be accreting black holes in hard or soft state. In some
cases, the contribution of the ULX to the overall X-ray flux appears to be
dominant with respect to that of the active nucleus. In addition, 6 ULX present
probable counterparts at other wavelengths (optical/infrared, radio). A
multiwavelength observing strategy is required to better assess the nature of
these sources.


title: Outer edges of face-on spiral galaxies

abstract:
  We present deep optical imaging of three face-on disk galaxies together with
a detailed description of the reduction and calibration methods used, in order
to measure the intrinsic shape of their outer stellar edges. Whereas it is now
well accepted that disks of spiral galaxies are not infinite exponential beyond
galactocentric distances of about 3-5 radial scalelengths, the genuine
structure of the truncation region is not yet well known. Our data
quantitatively establish a smooth truncation behaviour of the radial surface
brightness profiles and is best described by a two-slope model, characterised
by an inner and outer exponential scalelength separated at a relatively well
defined break radius. This result disagrees with the frequently assumed sharply
truncated nature of the radial surface brightness profiles and implies the
presence of stars and even star-formation beyond the break radius. In addition,
we do not find a strong influence of a nearby companion on the ratio of the
break radius to the radial scalelength. Our results denote new observational
constraints for the search of the physical explanation for these smooth disk
truncations.


title:
High Resolution 4.7 um Keck/NIRSPEC Spectra of Protostars. II: Detection
  of the 13CO Isotope in Icy Grain Mantles

abstract:
  The high resolution (R=25,000) infrared M band spectrum of the massive
protostar NGC 7538 : IRS9 shows a narrow absorption feature at 4.779 um (2092.3
cm-1) which we attribute to the vibrational stretching mode of the 13CO isotope
in pure CO icy grain mantles. This is the first detection of solid 13CO in the
interstellar medium. The 13CO band is a factor of 2.3 narrower than the apolar
component of the 12CO band. With this in mind, we discuss the mechanisms that
broaden solid state absorption bands. It is shown that ellipsoidally shaped
pure CO grains fit the bands of both isotopes at the same time. Reasonable fits
are also obtained by CO embedded in N2-rich ices and thermally processed
O2-rich ices. In addition, we report new insights into the the nature and
evolution of interstellar CO ices by comparing the high quality multi-component
solid 12CO spectrum of NGC 7538 : IRS9 with that of the previously studied low
mass source L1489 IRS. The narrow absorption by apolar CO ices is present in
both spectra, but much stronger in NGC 7538. It is superposed on a smooth broad
absorption feature well fitted by a combination of CO2 and H2O-rich laboratory
CO ices. The abundances of the latter two ices relative to the total H2O ice
column are the same in both sources. We thus suggest that thermal processing
manifests itself as evaporation of apolar ices only, and not the formation of
CO2 or polar ices. Finally, the decomposition of the 12CO band is used to
derive the 12CO/13CO abundance ratio in apolar ices. A ratio of 71+/-15 is
deduced, in good agreement with gas phase CO studies (~77) and the solid
12CO2/13CO2 ratio of 80+/-11 found in the same line of sight. The implications
for the chemical path along which CO2 is formed are discussed.


title:
Linear Gas Dynamics in the Expanding Universe: Why the Jeans Scale does
  not Matter

abstract:
  We investigate the relationship between the dark matter and baryons in the
linear regime. This relation is quantified by the so-called ``filtering
scale''. We show that a simple gaussian ansatz which uses the filtering scale
provides a good approximation to the exact solution.


title:
An XMM-Newton Observation of NGC 1399 Reveals Two Phases of Hot Gas and
  Super-Solar Abundances in the Central Regions

abstract:
  We present an initial analysis of a new XMM observation of NGC 1399, the
central elliptical galaxy of the Fornax group. Spectral fitting of the
spatially resolved spectral data of the EPIC MOS and pn CCDs reveals that a
two-temperature model (2T) of the hot gas is favored over single-phase and
cooling flow models within the central ~20 kpc. The preference for the 2T model
applies whether or not the data are deprojected. The cooler component has a
temperature (~0.9 keV) similar to the kinetic temperature of the stars while
the hotter component has a temperature (~1.5 keV) characteristic of the virial
temperature of a ~10^{13} M_sun halo. The two-phase model (and other
multitemperature models) removes the ``Fe Bias'' within r < ~20 kpc and gives
Z_Fe/Z_sun 1.5-2. At larger radii the iron abundance decreases until Z_Fe/Z_sun
\~0.5 for r ~50 kpc. The Si abundance is super-solar (1.2-1.7 solar) within the
central regions while Z_Si/Z_Fe ~0.8 over the entire region studied. These Fe
and Si abundances imply that ~80% of the Fe mass within r ~50 kpc originates
from Type Ia supernovae (SNIa). This SNIa fraction is similar to that inferred
for the Sun and therefore suggests a stellar initial mass function similar to
the Milky Way.


title: Early GRB Afterglows Revisited

abstract:
  The standard afterglow model neglects the presence of the GRB prompt
radiation ahead of the blast wave. In fact, the blast wave is dramatically
influenced by the leading gamma-ray front which preaccelerates the ambient
medium and loads it with electron-positron pairs. The front sweeps the medium
outward with a high Lorentz factor and results in a spectacular effect: the GRB
ejecta moves freely in a cavity behind its own radiation front. When the front
expands sufficiently and gets diluted, a blast wave develops, and it does it
differently from the standard model used before. The afterglow should initially
appear as a steep rise of soft emission (from infrared to soft X-rays) at a
time comparable to the prompt GRB duration and then the emission should quickly
evolve to a normal X-ray afterglow. This may explain the prompt optical flash
observed in GRB 990123 and allows one to infer the ejecta Lorentz factor in
this burst: \Gamma=200. The effect of the gamma-ray front on the afterglow
emission is especially pronounced if the GRB has a massive progenitor and the
blast wave propagates in the progenitor wind. We emphasize the importance of
early afterglow observations in soft bands, as they will allow one to test
different progenitor models.


title:
Magellan Spectroscopy of the Galaxy Cluster RX J1347.5-1145: Redshift
  Estimates for the Gravitationally Lensed Arcs

abstract:
  We present imaging and spectroscopic observations of the gravitationally
lensed arcs in the field of RX J1347.5-1145, the most X-ray luminous galaxy
cluster known. Based on the detection of the [OII] 3727 emission line, we
confirm that the redshift of one of the arcs is z = 0.806. Its color and [OII]
line strength are consistent with those of distant, actively star forming
galaxies. In a second arc, we tentatively identify a pair of absorption lines
superposed on a red continuum; the lines are consistent with Ca II H & K at z =
0.785. We detected a faint blue continuum in two additional arcs, but no
spectral line features could be measured. We establish lower limits to their
redshifts based on the absence of [OII] emission, which we argue should be
present and detectable in these objects. Redshifts are also given for a number
of galaxies in the field of the cluster.


title:
An investigation of gravitational lens determinations of H_o in
  quintessence cosmologies

abstract:
  There is growing evidence that the majority of the energy density of the
universe is not baryonic or dark matter, rather it resides in an exotic
component with negative pressure. The nature of this `quintessence' influences
our view of the universe, modifying angular diameter and luminosity distances.
Here, we examine the influence of a quintessence component upon gravitational
lens time delays. As well as a static quintessence component, an evolving
equation of state is also considered. It is found that the equation of state of
the quintessence component and its evolution influence the value of the
Hubble's constant derived from gravitational lenses. However, the differences
between evolving and non-evolving cosmologies are relatively small. We
undertake a suite of Monte Carlo simulations to examine the potential
constraints that can be placed on the universal equation of state from the
monitoring of gravitational lens system, and demonstrate that at least an order
of magnitude more lenses than currently known will have to be discovered and
analysed to accurately probe any quintessence component.


title: The Dwarf Novae of Shortest Period

abstract:
  We present observations of the dwarf novae GW Lib, V844 Her, and DI UMa.
Radial velocities of H-alph yield orbital periods of 0.05332 +- 0.00002 d (=
76.78 m) for GW Lib and and 0.054643 +- 0.000007 d (= 78.69 m) for V844 Her.
Recently, the orbital period of DI UMa was found to be only 0.054564 +-
0.000002 d (= 78.57 m) by Fried et al. (1999), so these are the three shortest
orbital periods among dwarf novae with normal-abundance secondaries.
  GW Lib has attracted attention as a cataclysmic binary showing apparent ZZ
Ceti-type pulsations of the white dwarf primary. Its spectrum shows sharp
Balmer emission flanked by strong, broad Balmer absorption, indicating a
dominant contribution by white-dwarf light. Analysis of the Balmer absorption
profiles is complicated by the unknown residual accretion luminosity and lack
of coverage of the high Balmer lines. Our best-fit model atmospheres are
marginally hotter than the ZZ Ceti instability strip, in rough agreement with
recent ultraviolet results from HST. The spectrum and outburst behavior of GW
Lib make it a near twin of WZ Sge, and we estimate it to have a quiescent V
absolute magnitude 12. Comparison with archival data reveals proper motion of
65 +- 12 mas/yr.
  The mean spectrum of V844 Her is typical of SU UMa dwarf novae. We detected
superhumps in the 1997 May superoutburst with superhump period = 0.05597 +-
0.00005 d. The spectrum of DI UMa appears normal for a dwarf nova near minimum
light.
  These three dwarf novae have nearly identical short periods but completely
dissimilar outburst characteristics. We discuss possible implications.


title:
Froth across the Universe Dynamics and Stochastic Geometry of the Cosmic
  Foam

abstract:
  A review on the properties and dynamical origin and nature of the cosmic
foam, the tenuous space-filling frothy network permeating the interior of the
Universe. We discuss the properties of this striking and intriguing pattern,
describing its observational appearance, and seeking to elucidate its dynamical
origin and nature. An extensive discussion on the gravitational formation and
dynamical evolution of weblike patterns puts particular emphasis on the
formative role of the generic anisotropy of the cosmic gravitational force
fields. These tidal fields play an essential role in shaping the pattern of the
large scale cosmic matter distribution. Special attention is put on a
geometrical and stochastic framework for a systematic evaluation of its fossil
information content on the cosmic structure formation process. Its distinct
geometric character and the stochastic nature provides the cosmic web with some
unique and at first unexpected properties. The implications for galaxy
clustering are discussed on the basis of its relevant branch of mathematics,
stochastic geometry. Central within this context are Voronoi tessellations,
which have been found to represent a surprisingly versatile model for spatial
cellular distributions.


title: The Nature of the Ionising Background at z=2.5-5

abstract:
  Using radiative transfer calculations and cosmological simulations of
structure formation, we study constraints that can be placed on the nature of
the cosmic ultraviolet (UV) background in the redshift interval 2.5< z <5. Our
approach makes use of observational estimates of the opacities of hydrogen and
singly ionised helium in the intergalactic medium during this epoch. In
particular, we model the reionisation of He II by sources of hard ultraviolet
radiation, i.e. quasars, and infer values for our parameterisation of this
population from observational estimates of the opacity of the He II Lyman-alpha
forest. Next, we estimate the photoionisation rate of H I from these sources
and find that their contribution to the ionising background is insufficient to
account for the measured opacity of the H I Lyman-alpha forest at a redshift z
3. This motivates us to include a soft, stellar component to the ionising
background to boost the hydrogen photoionisation rate, but which has a
negligible impact on the He II opacity. In order to simultaneously match
observational estimates of the H I and He II opacities, we find that galaxies
and quasars must contribute about equally to the ionising background in H I at
z~ 3.


title: Simultaneous X-ray spectroscopy of YY Gem with Chandra and XMM-Newton

abstract:
  We report on a detailed study of the X-ray spectrum of the nearby eclipsing
spectroscopic binary YY Gem. Observations were obtained simultaneously with
both large X-ray observatories, XMM-Newton and Chandra. We compare the
high-resolution spectra acquired with the Reflection Grating Spectrometer
onboard XMM-Newton and with the Low Energy Transmission Grating Spectrometer
onboard Chandra, and evidence in direct comparison the good performance of both
instruments in terms of wavelength and flux calibration. The strongest lines in
the X-ray spectrum of YY Gem are from oxygen. Oxygen line ratios indicate the
presence of a low-temperature component (1-4 MK) with density n_e < 2 10^{10}
cm^-3. The X-ray lightcurve reveals two flares and a dip corresponding to the
secondary eclipse. An increase of the density during phases of high activity is
suggested from time-resolved spectroscopy. Time-resolved global fitting of the
European Photon Imaging Camera CCD spectrum traces the evolution of temperature
and emission measure during the flares. These medium-resolution spectra show
that temperatures > 10^7 K are relevant in the corona of YY Gem although not as
dominant as the lower temperatures represented by the strongest lines in the
high-resolution spectrum. Magnetic loops with length on the order of 10^9 cm,
i.e., about 5 % of the radius of each star, are inferred from a comparison with
a one-dimensional hydrodynamic model. This suggests that the flares did not
erupt in the (presumably more extended) inter-binary magnetosphere but are
related to one of the components of the binary.


title: Gamma-rays from the Large Scale Structure of the Universe

abstract:
  Gamma-ray astronomy will play a crucial role in the investigation of
nonthermal processes in the large scale structure of the universe.
Particularly, galaxy clusters (GC) observations at this photon energy will help
us understand the origin of radio emitting high energy particles, the possible
level of cosmic-ray (CR) pressure in intracluster environment, and the strength
of intracluster magnetic fields. In addition here we point out the importance
of these observations for a possible detection of cluster accretion shocks and
for constraining their CR acceleration efficiency. We model spatial and
spectral properties of gamma-ray emission due to shock accelerated CRs in GC
and emphasize the importance of imaging capability of upcoming gamma-ray
facilities for a correct interpretation of observational results.


title:
Search for correlation between GRB's detected by BeppoSAX and
  gravitational wave detectors EXPLORER and NAUTILUS

abstract:
  Data obtained during five months of 2001 with the gravitational wave (GW)
detectors EXPLORER and NAUTILUS were studied in correlation with the gamma ray
burst data (GRB) obtained with the BeppoSAX satellite. During this period
BeppoSAX was the only GRB satellite in operation, while EXPLORER and NAUTILUS
were the only GW detectors in operation.
  No correlation between the GW data and the GRB bursts was found. The
analysis, performed over 47 GRB's, excludes the presence of signals of
amplitude h >=1.2 * 10^{-18}, with 95 % probability, if we allow a time delay
between GW bursts and GRB within +-400 s, and h >= 6.5 * 10^{-19}, if the time
delay is within +- 5 s. The result is also provided in form of scaled
likelihood for unbiased interpretation and easier use for further analysis.


title:
Deep radio imaging of the SCUBA 8-mJy survey fields: sub-mm source
  identifications and redshift distribution

abstract:
  The SCUBA 8-mJy survey is the largest submm extragalactic mapping survey
undertaken to date, centred on the Lockman Hole and ELAIS N2 regions. Here, we
present new 1.4-GHz imaging of the depth and resolution necessary to reliably
identify radio counterparts for 18 of 30 submm sources. Armed with this greatly
improved positional information, we present and analyse new optical, near-IR
and XMM-Newton X-ray imaging to identify optical/IR host galaxies to half of
the submm-selected sources in those fields. As many as 15% of the submm sources
detected at 1.4 GHz are resolved by the 1.4'' beam and a further 25% have more
than one radio counterpart, suggesting that radio and submm emission arise from
extended starbursts and that interactions are common. We note that less than a
quarter of the submm-selected sample would have been recovered by targeting
optically faint radio sources, underlining the selective nature of such
surveys. At least 60% of the radio-confirmed optical/IR host galaxies appear to
be morphologically distorted; many are composite systems - red galaxies with
relatively blue companions; just over half are found to be very red or
extremely red; contrary to popular belief, most are sufficiently bright to be
tackled with spectrographs on 8-m telescopes. We estimate the median redshift
of the S(850um) ~ 8 mJy submm galaxy population: if the radio/far-IR
correlation holds at high redshift, and our sample is unbiased, we derive a
conservative median z >= 2.0, or >= 2.4 using spectral templates more
representative of known submm galaxies [abridged].


title: VLT near-infrared spectra of hard serendipitous Chandra sources

abstract:
  We present near-infrared long-slit spectra of eight optically-dim X-ray
sources obtained with ISAAC on the Very Large Telescope. Six of the sources
have hard X-ray emission with a significant fraction of the counts emerging
above 2 keV. All were discovered serendipitously in the fields of three nearby
galaxy clusters observed with Chandra, and identified through near-infrared
imaging. The X-ray fluxes lie close to the break in the source counts. Two of
the sources show narrow emission lines, and a third has a broad line. One of
the narrow line-emitting sources has a clear redshift identification at z=2.18,
while the other has a tentative determination based on the highest redshift
detection of He I 10830 at z=1.26. The remainder have featureless spectra to
deep limiting equivalent widths of 20--60 angstroms and line flux approx= 5 x
10^{-17} erg/s/cm^2 in the K-band. High-quality J, H and Ks--band images of the
sources were combined with archival optical detections or limits to estimate a
photometric redshift for six. Two sources show complex double morphology. The
hard sources have spectral count ratios consistent with heavily obscured AGN,
while the host galaxy emits much of the optical and near-infrared flux. The
most likely explanation for the featureless continua is that the line photons
are being scattered or destroyed by optically-thick gas and associated dust
with large covering fractions.


title: Cosmological Weak Lensing

abstract:
  We present the current status of cosmic shear studies and their implications
on cosmological models. Theoretical expectations and observational results are
discussed in the framework of standard cosmology and CDM scenarios. The
potentials of the next generation cosmic shear surveys are discussed.


title:
QZ Serpentis: A Dwarf Nova with a 2-Hour Orbital Period and an
  Anomalously Hot, Bright Secondary Star

abstract:
  We present spectroscopy and time-series photometry of the dwarf nova QZ Ser.
The spectrum shows a rich absorption line spectrum of type K4 +- 2. K-type
secondary stars are generally seen in dwarf novae with orbital periods P-orb
around 6 h, but in QZ Ser the absorption radial velocities show an obvious
modulation (semi-amplitude 207(5) km/s) at P-orb = 119.752(2) min, much shorter
than typical for such a relatively warm and prominent secondary spectrum. The
H-alpha emission-line velocity is modulated at the same period and roughly
opposite phase. Time-series photometry shows flickering superposed on a
modulation with two humps per orbit, consistent with ellipsoidal variation of
the secondary's light. QZ Ser is a second example of a relatively short-period
dwarf nova with a surprisingly warm secondary. Model calculations suggest that
the secondary is strongly enhanced in helium, and had already undergone
significant nuclear evolution when mass transfer began. Several sodium
absorption features in the secondary spectrum are unusually strong, which may
indicate that the present-day surface was the site of CNO-cycle hydrogen
burning in the past.


title:
Stellar Radio Astronomy. Probing Stellar Atmospheres from Protostars to
  Giants

abstract:
  Radio astronomy has provided evidence for the presence of ionized atmospheres
around almost all classes of non-degenerate stars. Magnetically confined
coronae dominate in the cool half of the Hertzsprung-Russell diagram. Their
radio emission is predominantly of non-thermal origin and has been identified
as gyrosynchrotron radiation from mildly relativistic electrons, apart from
some coherent emission mechanisms. Ionized winds are found in hot stars and in
red giants. They are detected through their thermal, optically thick radiation,
but synchrotron emission has been found in many systems as well. The latter is
emitted presumably by shock-accelerated electrons in weak magnetic fields in
the outer wind regions. Radio emission is also frequently detected in pre-main
sequence stars and protostars, and has recently been discovered in brown
dwarfs. This review summarizes the radio view of the atmospheres of
non-degenerate stars, focusing on energy release physics in cool coronal stars,
wind phenomenology in hot stars and cool giants, and emission observed from
young and forming stars.


title: On conduction, cooling flows and galaxy formation

abstract:
  On the basis of the universal gas fraction in clusters of galaxies, we
estimate that the effective thermal conductivity required to balance radiative
cooling in the cores, where the gas temperature is 3-10keV, is about one tenth
of the Spitzer rate. This confirms that thermal conduction can be important for
the energy balance provided that it is not highly suppressed by magnetic fields
in the gas. We determine the global effective conductivity in a sample of 29
clusters using published X-ray data on the inferred cooling rates and show that
most lie between one and one tenth of the Spitzer rate. More work on the
profiles in cooling flow clusters is required to test the conduction hypothesis
further. We examine the possibility that conduction operates during galaxy
formation, and show that it provides a simple explanation for the upper-mass
cutoff in galaxy masses.


title:
Optical Photometry of the Type Ia SN 1999ee and the Type Ib/c SN 1999ex
  in IC 5179

abstract:
  We present UBVRIz lightcurves of the Type Ia SN 1999ee and the Type Ib/c SN
1999ex, both located in the galaxy IC 5179. SN 1999ee has an extremely well
sampled lightcurve spanning from 10 days before Bmax through 53 days after
peak. Near maximum we find systematic differences ~0.05 mag in photometry
measured with two different telescopes, even though the photometry is reduced
to the same local standards around the supernova using the specific color terms
for each instrumental system. We use models for our bandpasses and
spectrophotometry of SN 1999ee to derive magnitude corrections (S-corrections)
and remedy this problem. This exercise demonstrates the need of accurately
characterizing the instrumental system before great photometric accuracies of
Type Ia supernovae can be claimed. It also shows that this effect can have
important astrophysical consequences since a small systematic shift of 0.02 mag
in the B-V color can introduce a 0.08 mag error in the extinction corrected
peak B magnitudes of a supernova and thus lead to biased cosmological
parameters. The data for the Type Ib/c SN 1999ex present us with the first ever
observed shock breakout of a supernova of this class. These observations show
that shock breakout occurred 18 days before Bmax and support the idea that Type
Ib/c supernovae are due to core collapse of massive stars rather than
thermonuclear disruption of white dwarfs.


title: Radio Emission from Magnetars

abstract:
  We discuss properties of the expected radio emission from Soft Gamma-ray
Repeaters (SGRs) during their bursting activity in the framework of the model
of Thompson, Lyutikov and Kulkarni (2002), in which the high energy emission is
powered by the dissipation of super-strong magnetic fields in the
magnetospheres through reconnection-type events. Drawing on analogies with
Solar flares we predict that coherent radio emission resembling solar type-III
radio bursts may be emitted in SGRs during X-ray bursts. The radio emission
should have correlated pulse profiles with X-rays, narrow-band-type radio
spectrum with $\Delta \nu \leq \nu$ with the typical frequency $ \nu \geq 1 $
GHz, and, possibly, a drifting central frequency. We encourage sensitive radio
observations of SGRs during the bursting activity.


title: WIYN Open Cluster Study XI: WIYN 3.5m Deep Photometry of M35 (NGC 2168)

abstract:
  We present deep BVI observations of the core of M35 and a nearby comparison
field obtained at the WIYN 3.5m telescope under excellent seeing. These
observations display the lower main sequence in BV and VI CMDs down to V = 23.3
and 24.6, respectively. At these faint magnitudes background field stars are
far more numerous than the cluster stars, yet by using a smoothing technique
and CMD density distribution subtraction we recover the cluster fiducial main
sequence and luminosity function to V = 24.6. We find the location of the main
sequence in these CMDs to be consistent with earlier work on other open
clusters, specifically NGC 188, NGC 2420, and NGC 2477. We compare these open
cluster fiducial sequences to stellar models by Baraffe et al. (1998), Siess et
al. (2000), Girardi et al. (2000), and Yi et al. (2001) and find that the
models are too blue in both B-V and V-I for stars below ~0.4 Mo. M35 contains
stars to the limit of the extracted main sequence, at M ~ 0.10-0.15 Mo,
suggesting that M35 may harbor a large number of brown dwarfs, which should be
easy targets for near-IR instrumentation on 8-10m telescopes. We also identify
a new candidate white dwarf in M35 at V = 21.36 +- 0.01. Depending on which WD
models are used to interpret this cluster candidate, it is either a very high
mass WD (1.05 +- 0.05 Mo) somewhat older (0.19-0.26 Gyr, 3-4 sigma) than our
best isochrone age (150 Myr), or it is a modestly massive WD (0.67-0.78 Mo)
much too old (0.42-0.83 Gyr) to belong to the cluster.


title:
Constraining the Redshift z=6 Quasar Luminosity Function Using
  Gravitational Lensing

abstract:
  Recent discoveries by the Sloan Digital Sky Survey (SDSS) of four bright
redshift z=6 quasars could constrain the mechanism by which the supermassive
black holes powering these sources are assembled. Here we compute the
probability that the fluxes of the quasars are strongly amplified by
gravitational lensing, and therefore the likelihood that the black hole masses
are overestimated when they are inferred assuming Eddington luminosities. The
poorly-constrained shape of the intrinsic quasar luminosity function (LF) at
redshift z=6 results in a large range of possible lensing probabilities. If the
LF is either steep, or extends to faint magnitudes, the probability for
amplification by a factor of ten ore more (and with only one image detectable
by SDSS) can reach essentially 100 percent. We show that future observations,
in particular, either of the current four quasars at the high angular
resolution provided by the Hubble Space Telescope, or of an increased sample of
about twenty redshift six quasars at the current angular resolution, should
either discover several gravitational lenses, or else provide interesting new
constraints on the shape of the z=6 quasar LF.


title:
Evidence for Cluster Evolution from an Improved Measurement of the
  Velocity Dispersion and Morphological Fraction of Cluster 1324+3011 at z =
  0.76

abstract:
  We have carried out additional spectroscopic observations in the field of
cluster Cl 1324+3011 at z = 0.76. Combined with the spectroscopy presented in
Postman, Lubin & Oke (2001, AJ, 122, 1125), we now have spectroscopically
confirmed 47 cluster members. With this significant number of redshifts, we
measure accurately the cluster velocity dispersion to be 1016 (+126/-93) km/s.
The distribution of velocity offsets is consistent with a Gaussian, indicating
no substantial velocity substructure. As previously noted for other
optically-selected clusters at redshifts of z > 0.5, a comparison between the
X-ray luminosity (L_x) and the velocity dispersion (sigma) of Cl 1324+3011
implies that this cluster is underluminous in X-rays by a factor of ~3 - 40
when compared to the L_x - sigma relation for local and moderate-redshift
clusters. We also examine the morphologies of those cluster members which have
available high-angular-resolution imaging with the Hubble Space Telescope
(HST). There are 22 spectroscopically-confirmed cluster members within the HST
field-of-view. Twelve of these are visually classified as early-type
(elliptical or S0) galaxies, implying an early-type fraction of 0.55
(+0.17/-0.14) in this cluster. This fraction is a factor of ~1.5 lower than
that observed in nearby rich clusters. Confirming previous cluster studies, the
results for cluster Cl 1324+3011, combined with morphological studies of other
massive clusters at redshifts less than z = 1, suggest that the galaxy
population in massive clusters is strongly evolving with redshift. This
evolution implies that early-type galaxies are forming out of the excess of
late-type (spiral, irregular, and peculiar) galaxies over the ~7 Gyr timescale.


title:
PSR J2021+3651: A Young Radio Pulsar Coincident with an Unidentified
  EGRET Gamma-ray Source

abstract:
  We report on a deep search for radio pulsations toward five unidentified ASCA
X-ray sources coincident with EGRET gamma-ray sources. This search has led to
the discovery of a young and energetic pulsar using data obtained with the new
Wideband Arecibo Pulsar Processor. PSR J2021+3651 is likely associated with the
X-ray source AX J2021.1+3651, which in turn is likely associated with the COS B
high energy gamma-ray source 2CG 075+00, also known as GeV J2020+3658 or 3EG
J2021+3716. PSR J2021+3651 has a rotation period P = 104 ms and P_dot =
9.6x10^{-14}, implying a characteristic age ~17 kyr and a spin-down luminosity
E_dot ~ 3.4x10^{36}ergs/s. The dispersion measure DM ~ 371 pc cm^{-3} is by far
the highest of any observed pulsar in the Galactic longitude range 55 < l < 80.
This DM suggests a distance d > 10 kpc, and a high gamma-ray efficiency of
\~15%, but the true distance may be closer if there is a significant
contribution to the DM from excess gas in the Cygnus region. The implied
luminosity of the associated X-ray source suggests the X-ray emission is
dominated by a pulsar wind nebula unresolved by ASCA.


title:
Blue Variable Stars from the MACHO database I: Photometry and
  Spectroscopy of the LMC sample

abstract:
  We present the photometric properties of 1279 blue variable stars within the
LMC. Photometry is derived from the MACHO database. The lightcurves of the
sample exhibit a variety of quasi-periodic and aperiodic outburst behavior. A
characteristic feature of the photometric variation is that the objects are
reddest when at maximum outburst. A subset of 102 objects were examined
spectroscopically. Within this subset, 91% exhibited Balmer emission in at
least one epoch, in some cases with spectacular spectral variability. The
variability observed in the sample is consistent with the establishment and
maintenance of the Be phenomenon.


title:
Time-Dependent Photoionization in a Dusty Medium I: Code Description and
  General Results

abstract:
  We present a time-dependent photoionization code that combines
self-consistently metal evolution and dust destruction under an intense X-ray
UV radiation field. Firstly, we extend the mathematical formulation of the
time-dependent evolution of dust grains under an intense radiation flux with
the inclusion of the process of ion field emission (IFE). We determine the
relative importance of IFE with respect to X-ray and UV sublimation as a
function of grain size, intensity and hardness of the incident spectrum. We
then combine the processes of dust destruction with a photoionization code that
follows the evolution of the ionization states of the metals and the relative
radiative transitions. Our code treats, self-consistently, the gradual
recycling of metals into gas as dust is sublimated away; it allows for any
initial dust grain distribution and follows its evolution in space and time. In
this first paper, we use our code to study the time-dependent behaviour of the
X-ray and optical opacities in the nearby environment of a Gamma-ray Burst, and
show how the time variability of the low-energy and high-energy opacities can
yield powerful clues on the characteristics of the medium in which the bursts
occur.


title: K dwarfs and the chemical evolution of the Solar cylinder

abstract:
  K-dwarfs have life-times older than the present age of the Galactic disc, and
are thus ideal stars to investigate the disc's chemical evolution. We have
developed several photometric metallicity indicators for K dwarfs, based an a
sample of accurate spectroscopic metallicities for 34 disc and halo G and K
dwarfs. The photometric metallicities lead us to develop a metallicity index
for K dwarfs based only on their position in the colour absolute-magnitude
diagram. Metallicities have been determined for 431 single K dwarfs drawn from
the Hipparcos catalog, selecting the stars by absolute magnitude and removing
multiple systems. The sample is essentially a complete reckoning of the metal
content in nearby K dwarfs. We use stellar isochrones to mark the stars by
mass, and select a subset of 220 of the stars which is complete in a narrow
mass interval. We fit the data with a model of the chemical evolution of the
Solar cylinder. We find that only a modest cosmic scatter is required to fit
our age metallicity relation. The model assumes two main infall episodes for
the formation of the halo-thick disc and thin disc respectively. The new data
confirms that the solar neighbourhood formed on a long timescale of order 7
Gyr.


title: The 1000 Brightest HIPASS Galaxies: Newly Cataloged Galaxies

abstract:
  The HI Parkes All-Sky Survey (HIPASS) is a blind 21-cm survey for
extragalactic neutral hydrogen, covering the whole southern sky. The HIPASS
Bright Galaxy Catalog (BGC; Koribalski et al. 2002) is a subset of HIPASS and
contains the 1000 HI-brightest (peak flux density) galaxies. Here we present
the 138 HIPASS BGC galaxies, which had no redshift measured prior to the Parkes
multibeam HI surveys. Of the 138 galaxies, 87 are newly cataloged. Newly
cataloged is defined as no optical (or infrared) counterpart in the NASA/IPAC
Extragalactic Database. Using the Digitized Sky Survey we identify optical
counterparts for almost half of the newly cataloged galaxies, which are
typically of irregular or magellanic morphological type. Several HI sources
appear to be associated with compact groups or pairs of galaxies rather than an
individual galaxy. The majority (57) of the newly cataloged galaxies lie within
ten degrees of the Galactic Plane and are missing from optical surveys due to
confusion with stars or dust extinction. This sample also includes newly
cataloged galaxies first discovered in the HI shallow survey of the
Zone-of-Avoidance (Henning et al. 2000). The other 30 newly cataloged galaxies
escaped detection due to their low surface brightness or optical compactness.
Only one of these, HIPASS J0546-68, has no obvious optical counterpart as it is
obscured by the Large Magellanic Cloud. We find that the newly cataloged
galaxies with |b| > 10 are generally lower in HI mass and narrower in velocity
width compared with the total HIPASS BGC. In contrast, newly cataloged galaxies
behind the Milky Way are found to be statistically similar to the entire HIPASS
BGC. In addition to these galaxies, the HIPASS BGC contains four previously
unknown HI clouds.


title: Age Constraints on Brane Models of Dark Energy

abstract:
  Inspired by recent developments in particle physics, the so-called brane
world cosmology seems to provide an alternative explanation for the present
dark energy problem. In this paper, we use the estimated age of high-$z$
objects to constrain the value of the cosmological parameters in some
particular scenarios based on this large scale modification of gravity. We show
that such models are compatible with these observations for values of the
crossover distance between the 4 and 5 dimensions of the order of $r_c \leq
1.67H_o^{-1}$.


title:
Ultraviolet Detection of Interstellar 12C17O and the CO Isotopomeric
  Ratios toward X Persei

abstract:
  We report the detection of fully resolved absorption lines of A-X bands from
interstellar 12C17O and 12C18O, through high-resolution spectroscopy of X Per
with the Space Telescope Imaging Spectrograph. The first ultraviolet
measurement of an interstellar 12C17O column density shows that its
isotopomeric ratio is 12C16O/12C17O = 8700 \pm 3600. Simultaneously, the second
ultraviolet detection of interstellar 12C18O establishes its isotopomeric ratio
at 3000 \pm 600. These ratios are about five times higher than local ambient
oxygen isotopic ratios in the ISM. Such severe fractionation of rare species
shows that both 12C17O and 12C18O are destroyed by photodissociation, whereas
12C16O avoids destruction through self-shielding. This is to be contrasted with
our ratio of 12C16O/13C16O = 73 \pm 12 toward X Per, which is indistinguishable
from 12C/13C, the result of a balance between photodissociation of 13C16O and
its preferential formation via the isotope exchange reaction between CO and
C^+.


title: The Pulsar Wind Nebula in G11.2-0.3

abstract:
  We present an X-ray and radio study of the wind nebula surrounding the
central pulsar PSR J1811-1925 in the supernova remnant G11.2-0.3. Using high
resolution data obtained with the Chandra X-ray observatory and with the VLA
radio telescope we show the X-ray and radio emission is asymmetric around the
pulsar, despite the latter's central position in the very circular shell. The
new X-ray data allow us to separate the synchrotron emission of the pulsar wind
nebula from the surrounding thermal emission and that from the pulsar itself.
Based on X-ray data from two epochs, we observe temporal variation of the
location of X-ray hot spots near the pulsar, indicating relativistic motion. We
compare thermal emission observed within the shell, which may be associated
with the forward shock of the pulsar wind nebula, to thermal emission from a
nearby portion of the remnant shell, the temperature of which implies an
expansion velocity consistent with the identification of the remnant with the
historical event of 386 A.D. The measured X-ray and radio spectral indices of
the nebula synchrotron emission are found to be consistent with a single
synchrotron cooling break. The magnetic field implied by the break frequency is
anomalously large given the apparent size and age of the nebula if a spherical
morphology is assumed, but is consistent with a bipolar morphology.


title:
Photometric Properties of Long-period Variables in the Large Magellanic
  Cloud

abstract:
  Approximately four thousand light curves of red variable stars in the LMC
were selected from the 2.3-years duration MOA database by a period analysis
using the Phase Dispersion Minimization method. Their optical features
(amplitudes, periodicities, position in CMD) were investigated. Stars with
large amplitues and high periodicities were distributed on the only one strip
amongst multiple structure on the LMC period-luminosity relation. In the CMD,
the five strips were located in the order of the period. The stars with
characterized light curves were also discussed.


title: General Properties of Quiescent Novae

abstract:
  The observed properties of novae before and after eruption are discussed. The
distribution of orbital periods of novae shows a concentration near 3.2 h,
which resembles that of magnetic cataclysmic variables, and there is some
evidence that many of the novae themselves are magnetic near that orbital
period. Desynchronisation of polars by nova eruptions can lead to an estimate
(~2 x 10^3 y) for the time between eruptions for the strongly magnetic systems;
this is much shorter than that found from other methods. The similarity of pre-
and post-nova luminosities, at high rates of mass transfer, is ascribed to
irradiation of the secondary producing a self-sustained high Mdot state. This
slows cooling of the white dwarf after eruption, delays the onset of full scale
dwarf nova outbursts in most systems, and delays any descent into a hibernation
state of low rate of mass transfer.


title: The UCT Survey of Old Novae

abstract:
  We present a status report on our high speed photometric survey of faint
Cataclysmic Variables, which is concentrating on old novae.


title: Sedimentation and Fouling of Optical Surfaces at the ANTARES Site

abstract:
  ANTARES is a project leading towards the construction and deployment of a
neutrino telescope in the deep Mediterranean Sea. The telescope will use an
array of photomultiplier tubes to detect the Cherenkov light emitted by muons
resulting from the interaction with matter of high energy neutrinos. In the
vicinity of the deployment site the ANTARES collaboration has performed a
series of in-situ measurements to study the change in light transmission
through glass surfaces during immersions of several months. The average loss of
light transmission is estimated to be only ~2% at the equator of a glass sphere
one year after deployment. It decreases with increasing zenith angle, and tends
to saturate with time. The transmission loss, therefore, is expected to remain
small for the several year lifetime of the ANTARES detector whose optical
modules are oriented downwards. The measurements were complemented by the
analysis of the ^{210}Pb activity profile in sediment cores and the study of
biofouling on glass plates. Despite a significant sedimentation rate at the
site, in the 0.02 - 0.05 cm.yr^{-1} range, the sediments adhere loosely to the
glass surfaces and can be washed off by water currents. Further, fouling by
deposits of light-absorbing particulates is only significant for surfaces
facing upwards.


title: The Density Profile of Cluster-scale Dark Matter Halos

abstract:
  We measure the average gravitational shear profile of 6 massive clusters
(M_vir ~ 10^15 M_sun) at z=0.3 out to a radius ~2h^-1 Mpc. The measurements are
fitted to a generalized NFW-like halo model \rho(r) with an arbitrary r -> 0
slope \alpha. The data are well fitted by such a model with a central cusp with
\alpha ~ 0.9 - 1.6 (68% confidence interval). For the standard-NFW case \alpha
= 1.0, we find a concentration parameter c_vir that is consistent with recent
predictions from high-resolution CDM N-body simulations. Our data are also well
fitted by an isothermal sphere model with a softened core. For this model, our
1\sigma upper limit for the core radius corresponds to a limit \sigma_star \leq
0.1 cm^2 g^-1 on the elastic collision cross-section in a self-interacting dark
matter model.


title:
Properties of Quasar-Galaxy Associations and Gravitational Mesolensing
  by Halo Objects

abstract:
  A new catalog of 8382 close quasar-galaxy pairs is presented. The catalog was
composed using published catalogs of quasars and active galactic nuclei
containing 11358 objects, as well as the LEDA catalog of galaxies, which
contains on the order of 100 thousand objects. The search for pairs was carried
out in such a way that the linear distance between the galaxy and projected
quasar does not exceed 150kpc. Based on these new data, the dependence of the
number of pairs on a=z_G/z_Q is analysed, where z_G and z_Q are the redshifts
of the galaxy and quasar, respectively, revealing an excess of pairs with a<0.1
and a>0.9. This means that the galaxies in pairs are preferably located close
to either the observer or the quasar and avoid intermediate distances along the
line of sight to the quasar. Computer simulations demonstrate that it is not
possible to explain this number of pairs with the observed distribution in a as
the result of chance positional coincidences with a uniform spatial
distribution of galaxies. Data on globular clusters show that the excess of
pairs with a<0.1 and a>0.9 is consistent with the hypothesis that we are
observing distant compact objects that are strongly gravitationally lensed by
transparent lenses with a King mass distribution located in the halos of nearby
galaxies. The Hubble diagram for galaxies and quasars is presented.
Observational tests of the mesolensing hypothesis are formulated.


title: Infrared Imaging Polarimetry of Massive Star-forming Regions

abstract:
  Imaging polarimetry is a useful tool to reveal the 3D structure of dust
distributions and to localize embedded young stellar objects. We present maps
of the linear polarization at 2.2 micron for three ultra-compact HII regions
(G192.16-3.82, G331.28-0.19, G339.88-1.26) and the methanol maser source
G305.21+0.21. From the polarization maps, we draw conclusions on the morphology
of these objects and the presence of luminous illuminating sources.