title: On the Probability of Microlensing in GRB Afterglows

abstract:
  The declining lightcurve of the optical afterglow of gamma-ray burst
GRB000301C showed rapid variability with one particularly bright feature at
about t-t0=3.8 days. This event was interpreted as gravitational microlensing
by Garnavich, Loeb & Stanek (2000) and subsequently used to derive constraints
on the structure of the GRB optical afterglow. In this paper, we use these
structural parameters to calculate the probability of such a microlensing event
in a realistic scenario, where all compact objects in the universe are
associated with observable galaxies. For GRB000301C at a redshift of z=2.04,
the `a posteriori' probability for a microlensing event with an amplitude of
dm>=0.95 mag (as observed) is 0.7% (2.7%) for the most plausible scenario of a
flat Lambda-dominated FRW universe with Omega_m=0.3 and a fraction f_*=0.2
(1.0) of dark-matter in the form of compact objects. If we lower the
magnification threshold to dm>=0.10 mag, the probabilities for microlensing
events of GRB afterglows increase to 17% (57%). We emphasise that this low
probability for a microlensing signature of almost a magnitude does not exclude
that the observed event in the afterglow lightcurve of GRB000301C was caused by
microlensing, especially in light of the fact that a galaxy was found within 2
arcsec from the GRB. In that case, however, a more robust upper limit on the `a
posteriori' probability of ~5% is found. It does show, however, that it will
not be easy to create a large sample of strong GRB afterglow microlensing
events for statistical studies of their physical conditions on micro-arcsec
scales.


title:
High-Resolution Keck Spectra of the Associated Absorption Lines in 3C
  191

abstract:
  Associated absorption lines (AALs) are valuable probes of the gaseous
environments near quasars. Here we discuss high-resolution (6.7 km/s) spectra
of the AALs in the radio-loud quasar 3C 191 (redshift z=1.956). The measured
AALs have ionizations ranging from Mg I to N V, and multi-component profiles
that are blueshifted by ~400 to ~1400 km/s relative to the quasar's broad
emission lines. These data yield the following new results. 1) The density
based on Si II*/Si II lines is ~300 cm-3, implying a distance of ~28 kpc from
the quasar if the gas is photoionized. 2) The characteristic flow time is thus
\~3 x 10^7 yr. 3) Strong Mg I AALs identify neutral gas with very low
ionization parameter and high density. We estimate n_H > 5 x 10^4 cm-3 in this
region, compared to ~15 cm-3 where the N V lines form. 4) The total column
density is N_H < 4 x 10^18 cm-2 in the neutral gas and N_H ~ 2 x 10^20 cm-2 in
the moderately ionized regions. 5) The total mass in the AAL outflow is M ~ 2 x
10^9 Mo, assuming a global covering factor (as viewed from the quasar) of ~10%
>. 6) The absorbing gas only partially covers the background light source(s)
along our line(s) of sight, requiring absorption in small clouds or filaments
<0.01 pc across. The ratio N_H/n_H implies that the clouds have radial (line-
of-sight) thicknesses <0.2 pc. These properties might characterize a sub-class
of AALs that are physically related to quasars but form at large distances. We
propose a model for the absorber in which pockets of dense neutral gas are
surrounded by larger clouds of generally lower density and higher ionization.
This outflowing material might be leftover from a blowout associated with a
nuclear starburst, the onset of quasar activity or a past broad absorption line
(BAL) wind phase.


title: Constraints in the lambda_0-Omega_0 plane from gravitational lensing

abstract:
  I review simultaneous constraints on the cosmological parameters lambda_0 and
Omega_0 from gravitational lensing. The emphasis is on systematic extragalactic
surveys for strong gravitational lenses, mainly the largest and best-defined
such survey, JVAS/CLASS.


title: The JVAS/CLASS 6'' to 15'' Lens Search

abstract:
  We present the strategy and status of a gravitational lens search for
multiple imaging with angular separations between 6'' and 15'' with the
combined JVAS and CLASS data set of ~15,000 flat-spectrum radio sources.
Currently all but one lens candidate have been rejected.


title: Radio Supernova 1987A at 843 MHz

abstract:
  We report the flux densities of the evolving radio source SN1987A at 843 MHz
measured from observations made with the Molonglo Observatory Synthesis
Telescope between 1994 September and 2000 May. The radio light curve shows that
the rate of increase of the flux density jumped markedly around days 2800-3000
(i.e. in the first half of 1995), and that since then the radio evolution has
been remarkably well fitted by a simple linear increase of (62.7 +- 0.5)
microJansky/day. We discuss in detail the relationship between the radio light
curve and the recent brightening of the system at optical wavelengths.


title: Radio Microlensing: Past, Present & Near Future

abstract:
  Strongly correlated non-intrinsic variability between 5 and 8.5 GHz has been
observed in one of the lensed images of the gravitational lens B1600+434. These
non-intrinsic (i.e. `external') variations are interpreted as
`radio-microlensing' of relativistic micro-arsec-scale jet components in the
source at a redshift of z=1.59 by massive compact objects in the halo of the
edge-on disk lens galaxy at z=0.41. We shortly summarize these observations and
discuss several new observational and theoretical programs to investigate this
new phenomenon in more detail.


title:
First XMM-Newton observations of an isolated neutron star:
  RXJ0720.4-3125

abstract:
  We present the high resolution spectrum of the isolated neutron star
RXJ0720.4-3125, obtained with the Reflection Grating Spectrometer on
XMM-Newton, complemented with the broad band spectrum observed with the EPIC PN
camera. The spectrum appears smooth, with no evidence for strong photospheric
absorption or emission features. We briefly discuss the implications of our
failure to detect structure in the spectrum.


title: QCD phase transition and primordial density perturbations

abstract:
  We analyze the effect of primordial density perturbations on the cosmic QCD
phase transition. According to our results hadron bubbles nucleate at the cold
perturbations. We call this mechanism inhomogeneous nucleation. We find the
typical distance between bubble centers to be a few meters. This exceeds the
estimates from homogeneous nucleation by two orders of magnitude. The resulting
baryon inhomogeneities may affect primordial nucleosynthesis.


title: The Edge of the Solar System

abstract:
  The population of the Kuiper Belt within 50 AU of the Sun has likely been
severely depleted by gravitational perturbations from the giant planets,
particularly Neptune. The density of Kuiper Belt objects is expected to be two
orders of magnitude higher just beyond 50 AU, where planetary perturbations are
insignificant. In 1998 and 1999, we surveyed for Kuiper Belt Objects (KBOs) in
6 fields of the ecliptic (total sky area 1.5 deg^2) to limiting magnitudes
between R=24.9 and R=25.9. This is deep enough to detect KBOs of diameter >~
160 km at a distance of 65 AU. We detected 24 objects. None of these objects,
however, is beyond 53 AU. Our survey places a 95% CL upper limit of Sigma<5
deg^-2 on the surface density of KBOs larger than ~160 km beyond 55 AU. This
can be compared to the surface density of ~6 deg^-2 of 160 km KBOs at distances
30--50 AU determined from this survey and previous shallower surveys. The mean
volume density of D>160 km KBOs in the 55--65 AU region is, at >95% confidence,
less than the mean density in the 30--50 AU region, and at most twothirds of
the mean density from 40--50 AU. Thus, a substantial density increase beyond 50
AU is excluded in this model-independent estimate, implying that some process
or event in the history of the Solar System has truncated the distribution of
160-km planetesimals at ~50 AU. A dense primordial disk could be present beyond
50 AU if it contains only smaller objects, or is sufficiently thin and inclined
to have escaped detection in our 6 survey fields.


title:
A High Resolution Spectroscopic Observation of CAL 83 with
  XMM-Newton/RGS

abstract:
  We present the first high resolution photospheric X-ray spectrum of a
Supersoft X-ray Source, the famous CAL~83 in the Large Magellanic Cloud. The
spectrum was obtained with the Reflection Grating Spectrometer on XMM-Newton
during the Calibration/Performance Verification phase of the observatory. The
spectrum covers the range 20-40 A at an approximately constant resolution of
0.05 A, and shows very significant, intricate detail, that is very sensitive to
the physical properties of the object. We present the results of an initial
investigation of the spectrum, from which we draw the conclusion that the
spectral structure is probably dominated by numerous absorption features due to
transitions in the L-shells of the mid-$Z$ elements and the M-shell of Fe, in
addition to a few strong K-shell features due to CNO.


title: Tessellation Reconstruction Techniques

abstract:
  The application of Voronoi and Delaunay tessellation based methods for
reconstructing continuous fields from discretely sampled data sets is
discussed. The succesfull operation as ``multidimensional interpolation''
method is corroborated through their ability to reproduce even intricate
statistical aspects of the analytical predictions of perturbation theory of
cosmic velocity field evolution. The newly developed and fully self-adaptive
technique for density field estimation by means of Delaunay tessellations,
basically exploiting their ``minimum triangulation'' quality, is shown to
succesfully reproduce the morphology of the foamlike structure in N-body
simulations of cosmic structure formation. The full hierarchy of structure is
implicitly and directly reproduced at every spatial resolution scale present in
the particle distribution, at the same time automatically and sharply rendering
its characteristic anisotropic filamentary and wall-like features.


title:
Shocks and sonic booms in the intracluster medium: X-ray shells and
  radio galaxy activity

abstract:
  Motivated by hydrodynamic simulations, we discuss the X-ray appearance of
radio galaxies embedded in the intracluster medium (ICM) of a galaxy cluster.
We distinguish three regimes. In the early life of a powerful source, the
entire radio cocoon is expanding supersonically and hence drives a strong shock
into the ICM. Eventually, the sides of the cocoon become subsonic and the ICM
is disturbed by the sonic booms of the jet's working surface. In both of these
regimes, X-ray observations would find an X-ray shell. In the strong shock
regime, this shell will be hot and relatively thin. However, in the weak shock
(sonic-boom) regime, the shell will be approximately the same temperature as
the undisturbed ICM. If a cooling flow is present, the observed shell may even
be cooler than the undisturbed ICM due to the lifting of cooler material into
the shell from the inner (cooler) regions of the cluster. In the third and
final regime, the cocoon has collapsed and no well-defined X-ray shell will be
seen. We discuss ways of estimating the power and age of the source once its
regime of behavior has been determined.


title: Tidal stirring and the origin of dwarf spheroidals in the Local Group

abstract:
  N-Body/SPH simulations are used to study the evolution of dwarf irregular
galaxies (dIrrs) entering the dark matter halo of the Milky Way or M31 on
plunging orbits. We propose a new dynamical mechanism driving the evolution of
gas rich, rotationally supported dIrrs, mostly found at the outskirts of the
Local Group (LG), into gas free, pressure supported dwarf spheroidals (dSphs)
or dwarf ellipticals (dEs), observed to cluster around the two giant spirals.
The initial model galaxies are exponential disks embedded in massive dark
matter halos and reproduce nearby dIrrs. Repeated tidal shocks at the
pericenter of their orbit partially strip their halo and disk and trigger
dynamical instabilities that dramatically reshape their stellar component.
After only 2-3 orbits low surface brightness (LSB) dIrrs are transformed into
dSphs, while high surface brightness (HSB) dIrrs evolve into dEs. This
evolutionary mechanism naturally leads to the morphology-density relation
observed for LG dwarfs. Dwarfs surrounded by very dense dark matter halos, like
the archetypical dIrr GR8, are turned into Draco or Ursa Minor, the faintest
and most dark matter dominated among LG dSphs. If disks include a gaseous
component, this is both tidally stripped and consumed in periodic bursts of
star formation. The resulting star formation histories are in good qualitative
agreement with those derived using HST color-magnitude diagrams for local
dSphs.


title: Gamma Rays from Dark Matter

abstract:
  I give a brief review of high energy gamma-ray signatures of dark matter. The
decay of massive $X$-particles and subsequent hadronization have been suggested
as the origin of the highest energy cosmic rays. Propagation over cosmological
distances to Earth (as would be the case in some topological defect origin
models for the $X$-particles) results in potentially observable gamma-ray
fluxes at GeV energies. Massive relic particles on the other hand, would
cluster in galaxy halos, including that of our Galaxy, and may give rise to
anisotropic gamma ray and cosmic ray signals at ultra high energies. Future
observations above 100 Gev of gamma rays due to WIMP annihilation in the halo
of the Galaxy may be used to place constraints on supersymmetry parameter
space.


title: Oxygen line formation in 3D hydrodynamical model atmospheres

abstract:
  The formation of [O I], O I and OH lines in metal-poor stars has been studied
by means of 3D hydrodynamical model atmospheres. For O I detailed 3D non-LTE
calculations have been performed. While the influence of 3D model atmospheres
is minor for [O I] and O I lines, the very low temperatures encountered at low
metallicities have a drastic impact on the OH lines. As a result, the derived O
abundances are found to be systematically overestimated in 1D analyses, casting
doubts on the recent claims for a monotonic increase in [O/Fe] towards lower
metallicities.


title:
Relativistic Thermal Bremsstrahlung Gaunt Factor for the Intracluster
  Plasma. III. Frequency Integrated Emissivity

abstract:
  We present accurate analytic fitting formulae for the frequency integrated
Gaunt factors for the relativistic as well as nonrelativistic thermal
bremsstrahlung which is relevant to the intracluster plasma. The fitting is
carried out for 1 =< Zj =< 28, 6.0 < log T < 8.5, where Zj is the charge number
of the ion, and T is the electron temperature in kelvins. The present analytic
fitting formulae will be useful for the analysis of the X-ray emission which
comes from the intracluster plasma as well as the other X-ray sources.


title:
HST-NICMOS Observations of M31's Metal Rich Globular Clusters and Their
  Surrounding Fields: I. Techniques

abstract:
  We have obtained HST-NICMOS observations of five of M31's most metal rich
globular clusters. These data allow photometry of individual stars in the
clusters and their surrounding fields. However, to achieve our goals -- obtain
accurate luminosity functions to compare with their Galactic counterparts,
determine metallicities from the slope of the giant branch, identify long
period variables, and estimate ages from the AGB tip luminosity, we must be
able to disentangle the true properties of the population from the
observational effects associated with measurements made in very crowded fields.
  In this paper we present a careful analysis of photometry in crowded regions,
and show how image blending affects the results and interpretation of such
data. Although this analysis is specifically for our NICMOS observations in
M31, the techniques we develop can be applied to any imaging data taken in
crowded fields; we show how the effects of image blending will even limit NGST.
We use three different techniques to analyze the effects of crowding on our
data, including the insertion of artificial stars (traditional completeness
tests) and the creation of completely artificial clusters. They are used to
derive threshold- and critical-blending radii for each cluster, which determine
how close to the cluster center reliable photometry can be achieved. The
simulations also allow us to quantify and correct for the effects of blending
on the slope and width of the RGB at different surface brightness levels.


title:
Observations of the BL Lacertae Object OJ 287 in 1997 April and Nov
  ember

abstract:
  X-ray properties of the BL Lacertae object OJ 287, observed with ASCA on 1997
April 26 and November 17, are reported. The 0.5 -- 10 keV flux was lower than
those obtained in previous X-ray observations, and no evidence of intensity
variations was found during each observation. The obtained flux densities at 1
keV, 0.22~0.26 uJy, exceed the extrapolations from lower frequency synchrotron
continua, which were measured in nearly the same period as the present ASCA
observations. The X-ray spectra acquired with the GIS and SIS were consistently
described with a single power law model modified with the Galactic absorption,
and the derived photon indices, 1.5 ~ 1.6, are flatter than those observed so
far. These results strongly suggest that the X-ray spectra observed in 1997
arise via inverse Compton process alone. The X-ray spectra obtained in 1994
(Idesawa et al 1997), exhibiting a steeper slope than those in 1997, is thought
to be contaminated by "synchrotron soft tail".


title:
HST-NICMOS Observations of M31's Metal Rich Globular Clusters and Their
  Surrounding Fields: II. Results

abstract:
  We have obtained HST-NICMOS observations of five of M31's most metal rich
globular clusters: G1, G170, G174, G177 & G280. For the two clusters farthest
from the nucleus we statistically subtract the field population and estimate
metallicities using K-(J-K) color-magnitude diagrams (CMDs). Based on the
slopes of their infrared giant branches we estimate [Fe/H]=-1.22+/-0.43 for G1
and -0.15+/-0.37 for G280. We combine our infrared observations of G1 with two
epochs of optical HST-WFPC2 V-band data and identify at least one LPV based on
color and variability. The location of G1's giant branch in the K-(V-K) CMD is
very similar to that of M107, indicating a higher metallicity than our purely
infrared CMD: [Fe/H]=-0.9+/-0.2.
  For the field surrounding G280, we estimate the metallicity to be -1.3 with a
spread of 0.5 from the slope and width of the giant branch. Based on the
numbers and luminosities of the brightest giants, we conclude that only a small
fraction of the stars in this field could be as young as 2 Gyr, while the
majority have ages closer to 10 Gyr.
  The K-band luminosity functions (LFs) of the upper few magnitudes of G1 and
G280, as well as for the fields surrounding all clusters, are indistinguishable
from the LF measured in the bulge of our Galaxy. This indicates that these
clusters are very similar to Galactic clusters, and at least in the surrounding
fields observed, there are no significant populations of young luminous stars.


title: Star Formation Histories of Nearby Dwarf Galaxies

abstract:
  Properties of nearby dwarf galaxies are briefly discussed. Dwarf galaxies
vary widely in their star formation histories, the ages of their
subpopulations, and in their enrichment history. Furthermore, many dwarf
galaxies show evidence for spatial variations in their star formation history;
often in the form of very extended old populations and radial gradients in age
and metallicity. Determining factors in dwarf galaxy evolution appear to be
both galaxy mass and environment. We may be observing continuous evolution from
low-mass dwarf irregulars via transition types to dwarf spheroidals, whereas
other evolutionary transitions seem less likely.


title: Discovery of 101-s Pulsations from AX J0057.4-7325 in the SMC with ASCA

abstract:
  The results from two ASCA observations of AX J0057.4-7325 = RX J0057.3-7325
are presented. Coherent pulsations with a barycentric period of 101.45 +/- 0.07
s were discovered in the second observation. The X-ray spectrum was found to be
hard (photon index ~ 0.9) and unchanged through these observations, except for
the flux. The ROSAT archival data show that AX J0057.4-7325 exhibits a flux
variation with a factor >~ 10. A discussion on a possible optical counterpart
is given.


title: Lead: Asymptotic Giant Branch production and Galactic Chemical Evolution

abstract:
  The enrichment of Pb in the Galaxy is followed in the framework of a detailed
model of Galactic chemical evolution that already proved adequate to reproduce
the chemical enrichment of O and of the elements from Ba to Eu. The stellar
yields are computed through nucleosynthesis calculations in the Asymptotic
Giant Branch (AGB) phase of low- and intermediate-mass stars, covering a wide
range of metallicities. The physical parameters of the stellar structure were
derived from full stellar evolutionary models previously computed. We show that
low-mass AGB stars are the main producers of Pb in the Galaxy, with a complex
dependence on metallicity and a maximum efficiency at [Fe/H] ~ -1. Our
calculations succeed in reproducing the abundances of Pb isotopes in the solar
system: the role attributed by the classical analysis of the s-process to the
'strong component', in order to explain more than 50% of solar 208Pb, is
actually played by the high production of Pb in low-mass and low-metallicity
AGB stars. We then follow the Galactic chemical evolution of Pb isotopes and
give our expectations on the s-process contribution to each of them at the
epoch of the solar system formation. Finally, we present new spectroscopic
estimates of Pb abundance on a sample of field stars and compare them, together
with a few other determinations available, with the predicted trend of [Pb/Fe]
in the Galaxy.


title:
XTE J1550-564: A superluminal ejection during the September 1998
  outburst

abstract:
  In 1998 September, the X-ray transient XTE J1550-564 underwent a major
outburst in soft and hard X-rays, followed by a radio flare. Australian Long
Baseline Array images obtained shortly after the peak in the radio flare showed
evolving structure. The components observed have an apparent separation
velocity of >2c.


title: Particle Acceleration and Diffusion in Fossil Radio Plasma

abstract:
  The strong activity of radio galaxies should have led to a nearly ubiquitous
presence of fossil radio plasma in the denser regions of the inter-galactic
medium as clusters, groups and filaments of galaxies. This fossil radio plasma
can contain large quantities of relativistic particles (electrons and possibly
protons) by magnetic confinement. These particles might be released and/or
re-energized under environmental influences as turbulence and shock waves.
Possible connections of such processes to the formation of the observed sources
of diffuse radio emission in clusters of galaxies (the cluster radio halos and
the cluster radio relics) are discussed.


title: An Ultraviolet Study of the Short-Period Binary OO Aquilae

abstract:
  OO Aql is a rare W UMa-type eclipsing binary in which the two solar-type
stars may have only recently evolved into contact. The binary has an unusually
high mass ratio (0.84), and a relatively long orbital period (0.506 d) for it
spectral type (mid-G). Twelve ultraviolet spectra of OO Aql were obtained in
1988 with the IUE satellite, including a series of consecutive observations
that cover nearly a complete orbital cycle. Chromospheric activity is studied
by means of the Mg II h+k emission at 2800 A. The Mg II emission is found to
vary, even when the emission is normalized to the adjacent continuum flux. This
variation may be correlated with orbital phase in the 1988 observations. It
also appears that the normalized Mg II emission varies with time, as seen in
spectra obtained at two different epochs in 1988 and when compared with two
spectra obtained several years earlier. The level of chromospheric activity in
OO Aql is less than that of other W UMa-type binaries of similar colors, but
this is attributed to its early stage of contact binary evolution. Ultraviolet
light curves were composed from measurements of the ultraviolet continuum in
the spectra. These were analyzed along with visible light curves of OO Aql to
determine the system parameters. The large wavelength range in the light curves
enabled a well-constrained fit to a cool spot in the system.


title: NGC 6251 at multiple scales and wavelengths

abstract:
  We have studied the FR I radio galaxy NGC 6251 and its environment at several
wavelengths and scale lengths. On the large scale, we have probed the gravity
field by measuring the velocity dispersion of the cluster members associated
with NGC 6251 and relating this to the cluster's X-ray emission. On the small
scale, the gravitational information is provided by cold HI near the nucleus
and the distribution of stars and gas near the centre of the galaxy. The cold
HI gas which we have measured explains the absorption of the central X-ray
emission and is consistent with the extinction through the recently discovered
HST gas disc of NGC 6251.


title:
Constraints on the neutrino mass and the cosmological constant from
  large scale structure observations

abstract:
  The observational data on the large scale structure (LSS) of the Universe are
used to establish the upper limit on the neutrino content marginalized over all
other cosmological parameters within the class of adiabatic inflationary
models. It is shown that the upper 2$\sigma$ limit on the neutrino content can
be expressed in the form $\Omega_{\nu}h^2/N_{\nu}^{0.64}\le0.042$ or, via the
neutrino mass, $m_{\nu}\le4.0$eV.


title:
The distance modulus of the Large Magellanic Cloud based on double-mode
  RR Lyrae stars

abstract:
  We use double-mode RR Lyrae (RRd) stars from the MACHO variable star database
of the Large Magellanic Cloud (LMC) to estimate its distance, by utilizing
photometric data, linear pulsation and stellar atmosphere models. If we set
E_(B-V)=0.11 and [M/H]=-1.5 for LMC, we get M-m=18.52 mag, which is in
agreement with the value obtained from Galactic cluster RRd stars. Although the
formal statistical error (standard deviation) of M-m derived from the MACHO set
is only 0.024 mag, the systematic errors are more substantial. These errors are
mostly due to the zero point ambiguity of the temperature scale and to the
error of the photometric calibration. However, the fact that the distance
moduli obtained in this and in our former studies of cluster RRd and Small
Magellanic Cloud beat Cepheids agree so well, implies that the only serious
source of error is the zero point of the temperature scale, which should not
have larger than +/-0.10 mag effect on the distance modulus.


title: Models for the Origin of the Knee in the Cosmic-Ray Spectrum

abstract:
  A sudden steepening of the cosmic-ray energy spectrum (the knee) is observed
at an energy of about 3 PeV (1 PeV = $10^{15}$ eV). The experimental study of
the PeV cosmic rays has intensified greatly during the last 3 years. The recent
results on extensive air showers allow us to conclude that: a) the knee has an
astrophysical origin; b) the `sharpness' and the fine structure of the knee
rule out `Galactic Modulation' as the origin of the knee; c) most likely the
knee is the result of the explosion of a single, recent, nearby supernova.


title:
Time dependent cosmic-ray shock acceleration with self-consistent
  injection

abstract:
  One of the key questions to understanding the efficiency of diffusive shock
acceleration of the cosmic rays (CRs) is the injection process from thermal
particles. A self-consistent injection model based on the interactions of the
suprathermal particles with self-generated magneto-hydrodynamic waves has been
developed recently by Malkov (1998, Phys. Rev. E 58, 4911). By adopting this
analytic solution, a numerical treatment of the plasma-physical injection model
at a strong quasi-parallel shock has been devised and incorporated into the
combined gas dynamics and the CR diffusion-convection code. In order to
investigate self-consistently the injection and acceleration efficiencies, we
have applied this code to the CR modified shocks of both high and low Mach
numbers (M=30 and M=2.24) with a Bohm type diffusion model. We find the
injection process is self-regulated in such a way that the injection rate
reaches and stays at a nearly stable value after quick initial adjustment. For
both shocks about 0.1% of the incoming thermal particles are injected into the
CRs. For the weak shock, the shock has reached a steady state within our
integration time and about 10% of the total available shock energy is
transfered into the CR energy density. The strong shock has achieved a higher
acceleration efficiency of about 20% by the end of our simulation, but has not
yet reached a steady-state.


title:
Peering through the dust: Evidence for a supermassive Black Hole at the
  nucleus of Centaurus A from VLT IR spectroscopy

abstract:
  We used the near infrared spectrometer ISAAC at the ESO 'Very Large
Telescope' to map the velocity field of Centaurus A (NGC 5128) at several
position angles and locations in the central 20" of the galaxy. The high
spatial resolution (~0.5") velocity fields from both ionized and molecular gas
(PaBeta, [FeII], BrGamma, and H2) are not compromised by either excitation
effects or obscuration. We identify three distinct kinematical systems: (i) a
rotating 'nuclear disk' of ionized gas, confined to the inner 2", the
counterpart of the PaAlpha feature previously revealed by HST/NICMOS imaging;
(ii) a ring-like system with a ~6" inner radius detected only in H2, likely the
counterpart of the 100pc-scale structure detected in CO by other authors; (iii)
a normal extended component of gas rotating in the galactic potential. The
nuclear disk is in keplerian rotation around a central mass concentration, dark
(M/L>20 Msun/LsunK) and point-like at the spatial resolution of the data
(R<0.25" ~4pc). We interpret this mass concentration as a supermassive black
hole. Its dynamical mass based on the line velocities and disk inclination
(i>15deg) is M=2(+3.0;-1.4) 10^8 Msun. The ring-like system is probably
characterized by non-circular motions; a 'figure-of-8' pattern observed in the
H2 position-velocity diagram might provide kinematical evidence for the
presence of a nuclear bar.


title: The protostellar system HH108MMS

abstract:
  We probe the region around the protostar HH108MMS by deep mid infrared
photometric and polarimetric imaging. The protostar is detected at 14mu in
absorption against the diffuse background. Next to HH108MMS, we find a second
absorbing core, named Q1, and the young stellar object IRAS18331-0035 which is
more advanced in its evolution and already seen in emission at 12mu and 14mu.
HH108MMS, Q1 and IRAS18331-0035 form a triplet along an extended filamentary
absorption feature. From the variation of the surface brightness across the
source, we derive for HH108MMS and Q1 the optical depth and density profile. As
HH108MMS is also seen in the millimeter dust emission, we can derive the ratio
of the dust extinction coefficients at 14mu and 1.3mm and obtain kappa(14mu) /
kappa(1300mu) ~ 470. Because models for the dust in the diffuse interstellar
medium predict a ratio of around 2000, our value points to fluffy composite
grains which are expected to prevail in dense and cold environments. First mid
infrared polarisation images of pre--stellar absorbing cores are presented. At
12mu and 14mu the polarisation of the region around HH108MMS is strong (> 15%)
and tightly correlated with the source triplet. We demonstrate that the high
degree of polarisation can be explained by extinction of rotationally aligned
dust particles of moderate elongation.


title: A search for new gamma Doradus stars in the Geneva photometric database

abstract:
  We present a study of selected potential gamma Doradus stars observed in the
Geneva photometric system. Eleven stars were monitored at least during the last
year of functioning of the 70 cm Swiss telescope at La Silla, leading to about
one thousand photometric measurements and permitting a detailed analysis of
these stars. After the analysis, five stars are thought to be constant stars.
We report three new gamma Doradus stars. A spectroscopic campaign has been
started at La Silla with the new 1m20 Swiss telescope, equipped with the
spectrograph CORALIE, of which we show the results for the selected stars.


title:
CORMASS: A Compact and Efficient NIR Spectrograph for Studying Low-Mass
  Objects

abstract:
  CorMASS (Cornell Massachusetts Slit Spectrograph) is a compact,
low-resolution (R=300), double-pass prism cross-dispersed near-infrared (NIR)
spectrograph in operation on the Palomar Observatory 60-inch telescope. Its
2-dimensional spectral format provides simultaneous coverage from lambda ~ 0.75
microns to lambda ~ 2.5 microns (z'JHK bands). A remotely operated cold flip
mirror permits its NICMOS3 detector to function as a K_s slit viewer to assist
object placement into the 2 arcsec x 15 arcsec slit. CorMASS was primarily
designed for the rapid spectral classification of low-mass stellar and
sub-stellar objects identified by the Two-Micron All Sky Survey (2MASS).
CorMASS' efficiency and resolution also make it a versatile instrument for the
spectral observation and classification of many other types of bright objects
(K<14) including quasars, novae, and emission line objects.


title: Freely precessing neutron stars: Model and observations

abstract:
  We present a model of a freely precessing neutron star which is then compared
against pulsar observations. The aim is to draw conclusions regarding the
structure of the star, and test theoretical ideas of crust-core coupling and
superfluidity. We argue that, on theoretical grounds, it is likely that the
core neutron superfluid does not participate in the free precession of the
crust. We apply our model to the handful of proposed observations of free
precession that have appeared in the literature. Assuming crust-only
precession, we find that all but one of the observations are consistent with
there not being any pinned crustal superfluid at all; the maximum amount of
pinned superfluid consistent with the observations is about 10^-10 of the total
stellar moment of inertia. However, the observations do not rule out the
possibility that the crust and neutron superfluid core precess as a single
unit. In this case the maximum amount of pinned superfluid consistent with the
observations is about 10^-8 of the total stellar moment of inertia. Both of
these values are many orders of magnitude less than the 10^-2 value predicted
by many theories of pulsar glitches. We conclude that superfluid pinning, at
least as it affects free precession, needs to be reconsidered.


title:
The effect of turbulent pressure on the p-mode frequencies in stellar
  models

abstract:
  We have constructed models for the sun at three stages of its evolution: a
zero-age main sequence model, the present sun, and a subgiant model. For each
model, the turbulent pressure and turbulent kinetic energy were calculated from
3-d radiative hydrodynamical simulations (described in the poster by Robinson
et al.), and inserted into the 1-d stellar models. We note that in these
simulations, the turbulent pressure is not a free parameter, but can be
computed from the resulting velocity field. We show the calculated p-mode
frequencies for the model of the present sun, with and without turbulent
pressure, and compare them to the observed solar frequencies. When the
turbulent pressure is included in the models, the calculated frequencies are
brought closer to the observed frequencies in the sun by up to two $\mu Hz$,
strictly from structural effects. The effect of including turbulent pressure on
p-mode frequencies is also shown for the zero-age main sequence model. Our
models also suggest that the importance of turbulent pressure increases as the
star evolves into the subgiant region. We discuss the importance of also
including realistic turbulence as well as radiation in the non-adiabatic
calculation of oscillation frequencies.


title:
Radiative hydrodynamics in the highly super adiabatic layer of stellar
  evolution models

abstract:
  We present results of three dimensional simulations of the uppermost part of
the sun, at 3 stages of its evolution. Each model includes physically realistic
radiative-hydrodynamics (the Eddington approximation is used in the optically
thin region), varying opacities and a realistic equation of state (full
treatment of the ionization of H and He). In each evolution model, we
investigate a domain, which starts at the top of the photosphere and ends just
inside the convection zone (about 2400 km in the sun model). This includes all
of the super-adiabatic layer (SAL). Due to the different positions of the three
models in the $log (g) $ vs $log T_{eff}$ plane, the more evolved models have
lower density atmospheres. The reduction in density causes the amount of
overshoot into the radiation layer, to be greater in the more evolved models.


title:
The nature of the bright submillimeter galaxy population: a radio
  pre-selected sample with I>25

abstract:
  Deep submillimetre surveys have successfully detected distant, star-forming
galaxies, enshrouded in vast quantities of dust and which emit most of their
energy at far infrared wavelengths. These luminous galaxies are an important
constituent of the Universal star-formation history, and any complete model of
galaxy evolution must account for their existence. Although these sources have
been tentatively identified with very faint and sometimes very red optical
counterparts, their poorly constrained redshift distribution has made their
interpretation unclear. In particular, it was not understood if these galaxies
had been missed in previous surveys, or if they constituted a truly new class
of objects, undetectable at other wavelengths. By utilizing a radio selection
technique, we have isolated a sample of 20 sub-mm objects representative of the
850 micron population brighter than 5 mJy with z<~3. We show that these
galaxies are so heavily dust obscured that they remain essentially 'invisible'
to ultraviolet selection. Furthermore, relying on the radio-submillimeter flux
density ratio, we estimate their redshift distribution, finding a median of
two. While not a substitute for the thorough followup of blank field sub-mm
surveys, our results do shed light on a substantial portion of the luminous
sub-mm population with z<~3.


title: Baryon-poor outflows from rotating black holes

abstract:
  Cosmological gamma-ray bursts are probably powered by systems harboring a
rotating black hole. We show that frame-dragging creates baryon-poor outflows
in a differentially rotating gap along an open magnetic flux-tube with
dissipation $P=\Omega_T(\Omega_H-2\Omega_T)A_\phi^2$, where $2\pi A_\phi$
denotes the flux in the open tube, for angular velocities $\Omega_H$ and
$\Omega_T$ of the black hole and the torus, respectively. The output in
photon-pair outflow will be reprocessed in an intervening hypernova progenitor
wind or the ISM.


title:
The Formal Underpinnings of the Response Functions used in X-Ray
  Spectral Analysis

abstract:
  This work provides an in-depth mathematical description of the response
functions that are used for spatial and spectral analysis of X-ray data. The
use of such functions is well-known to anyone familiar with the analysis of
X-ray data where they may be identified with the quantities contained in the
Ancillary Response File (ARF), the Redistribution Matrix File (RMF), and the
Exposure Map. Starting from first-principles, explicit mathematical expressions
for these functions, for both imaging and dispersive modes, are arrived at in
terms of the underlying instrumental characteristics of the telescope including
the effects of pointing motion. The response functions are presented in the
context of integral equations relating the expected detector count rate to the
source spectrum incident upon the telescope. Their application to the analysis
of several source distributions is considered. These include multiple, possibly
overlapping, and spectrally distinct point sources, as well as extended
sources. Assumptions and limitations behind the usage of these functions, as
well as their practical computation are addressed.


title: The Angular Power Spectrum of EDSGC Galaxies

abstract:
  We determine the angular power spectrum, C_l, of the Edinburgh/Durham
Southern Galaxy Catalog (EDSGC) and use this statistic to constrain
cosmological parameters. Our methods for determining C_l, and the parameters
that affect it are based on those developed for the analysis of cosmic
microwave background maps. We expect them to be useful for future surveys.
Assuming flat cold dark matter models with a cosmological constant (constrained
by COBE/DMR and local cluster abundances), and a scale--independent bias, b, we
find good fits to the EDSGC angular power spectrum with 1.11 < b < 2.35 and 0.2
< Omega_m < 0.55 at 95% confidence. These results are not significantly
affected by the ``integral constraint'' or extinction by interstellar dust, but
may be by our assumption of Gaussianity.


title: Superluminal Recession Velocities

abstract:
  Hubble's Law, v=HD (recession velocity is proportional to distance), is a
theoretical result derived from the Friedmann-Robertson-Walker metric. v=HD
applies at least as far as the particle horizon and in principle for all
distances. Thus, galaxies with distances greater than D=c/H are receding from
us with velocities greater than the speed of light and superluminal recession
is a fundamental part of the general relativistic description of the expanding
universe. This apparent contradiction of special relativity (SR) is often
mistakenly remedied by converting redshift to velocity using SR. Here we show
that galaxies with recession velocities faster than the speed of light are
observable and that in all viable cosmological models, galaxies above a
redshift of three are receding superluminally.


title:
Formation of a Massive Black Hole at the Center of the Superbubble in
  M82

abstract:
  We performed 12CO(1-0), 13CO(1-0), and HCN(1-0) interferometric observations
of the central region (about 450 pc in radius) of M82 with the Nobeyama
Millimeter Array, and have successfully imaged a molecular superbubble and
spurs. The center of the superbubble is clearly shifted from the nucleus by 140
pc. This position is close to that of the massive black hole (BH) of >460 Mo
and the 2.2 micron secondary peak (a luminous supergiant dominated cluster),
which strongly suggests that these objects may be related to the formation of
the superbubble. Consideration of star formation in the cluster based on the
infrared data indicates that (1) energy release from supernovae can account for
the kinetic energy of the superbubble, (2) the total mass of stellar-mass BHs
available for building-up the massive BH may be much higher than 460 Mo, and
(3) it is possible to form the middle-mass BH of 100-1000 Mo within the
timescale of the superbubble. We suggest that the massive BH was produced and
is growing in the intense starburst region.


title:
Hydrodynamic Models of Line-Driven Accretion Disk Winds II: Adiabatic
  Winds from Nonisothermal Disks

abstract:
  We present here numerical hydrodynamic simulations of line-driven accretion
disk winds in cataclysmic variable systems. We calculate wind mass-loss rate,
terminal velocities, and line profiles for CIV (1550 A) for various viewing
angles. The models are 2.5-dimensional, include an energy balance condition,
and calculate the radiation field as a function of position near an optically
thick accretion disk. The model results show that centrifugal forces produce
collisions of streamlines in the disk wind which in turn generate an enhanced
density region, underlining the necessity of two dimensional calculations where
these forces may be represented. For disk luminosity Ldisk = Lsun, white dwarf
mass Mwd = 0.6 Msun, and white dwarf radii Rwd = 0.01 Rsun, we obtain a wind
mass-loss rate of dMwind/dt = 8.0E-12 Msun/yr, and a terminal velocity of ~3000
km/s. The line profiles we obtain are consistent with observations in their
general form, in particular in the maximum absorption at roughly half the
terminal velocity for the blue-shifted component, in the magnitudes of the wind
velocities implied by the absorption components, in the FWHM of the emission
components, and in the strong dependence in inclination angle.


title: The Red-Sequence Cluster Survey

abstract:
  The Red-Sequence Cluster Survey (RCS) is a new galaxy cluster survey designed
to provide a large sample of optically selected 0.1$<$z$<$1.4 clusters. The
planned survey data are 100 square degrees of two color ($R$ and $z'$) imaging,
with a 5$\sigma$ depth $\sim$2 mag past M$^{*}$ at $z=1$. The combined depth
and area of the RCS make it the widest field, moderately deep survey ever
undertaken using 4m class telescopes. This paper gives a brief outline of the
RCS survey, with particular emphasis on the data reduction strategy. The
remainder of the paper focuses on preliminary results from the first set of
completely reduced data ($\sim$10 deg$^2$, of the $\sim$60 deg$^2$ in hand). We
provide a new example of a rich $z>1$ cluster, illustrative of the dozens
discovered in the data so far. Some of the possible science to come from the
RCS is illustrated by a qualitative indication of $\Omega_{M}$ from the first
1/10th of the survey data. A high-precision measurement of the 2-point
correlation function of luminous early-type galaxies at $0.4<z<1.2$ is also
shown.


title: The Red-Sequence Cluster Survey: The Value of $\Omega_m$ and $\sigma_8$

abstract:
  The Red-Sequence Cluster Survey (RCS) is a 100 deg$^2$ optical survey for
high-redshift galaxy clusters. One of the goals of the survey is a measurement
of $\Omega_m$ and $\sigma_8$ via the evolution of the mass spectrum of galaxy
clusters. Herein we briefly describe how this will initially be done, and also
demonstrate the eventual power of the RCS for this type of measurement by a
qualitative analysis of the first 1/10th of the survey data.


title:
Fitting planes to early-type galaxies: MIST for the determination of the
  Fundamental Plane

abstract:
  The present study deals with the problem of deriving the coefficients of the
fundamental plane (FP) of early-type galaxies.
  We introduce statistical models of the FP and relative fitting methods: the
MIST (Measurement errors and Intrinsic Scatter Three dimensional) fits. The
MIST fits account for the measurement errors on the variables and their
correlations as well as for the intrinsic scatter. We show that the lack of a
model of the intrinsic scatter of the FP is the origin of the systematic
differences between the various fitting methods.
  We also address the problem of estimating the uncertainties of the FP
coefficients and determine a simple relation between the sample size and the
expected accuracy of the coefficients.
  The present study leads to define a `minimum sample size' for a correct
estimate of the uncertainties. For N < 30, both theoretical formulae and
re-sampling techniques, like the bootstrap, do not give reliable estimates.
  The question of the 'universality' of the FP is addressed by applying the
MIST fits to ten samples of cluster galaxies. The FP slopes are actually
consistent between the different samples, but, due to the large uncertainties,
they could also hide significant systematic differences.
  The feasibility of the measurement of the possible variations of the FP
slopes as a function of redshift is also proved.


title: Optical spectral variability of PG QSOs

abstract:
  In previous studies we have shown that the optical variability of quasars
increases, on average, with redshift. We explained this dependance in terms of
a hardening of the spectrum during bright phases, coupled with the increase of
the rest-frame frequency for increasing redshift. We re-analize now these
correlations on the basis of new light curves of PG quasars, recently published
by the Wise Observatory group.


title: Sub-mm clues to elliptical galaxy formation

abstract:
  There is growing evidence that, at the S(850) < 1 mJy level, the sub-mm
galaxy population (and hence a potentially significant fraction of the sub-mm
background) is associated with the star-forming Lyman-break population already
detected at optical wavelengths. However, the implied star-formation rates in
such objects (typically 3-30 solar masses per year) fall one or two orders of
magnitude short of the level of star-forming activity required to produce the
most massive elliptical galaxies on a timescale ~ 1 Gyr. If a significant
fraction of massive ellipticals did form the bulk of their stars in short-lived
massive starbursts at high redshift, then they should presumably be found among
the brighter, S(850) ~ 10 mJy sub-mm sources which are undoubtedly not part of
the Lyman-break population. A first powerful clue that this is indeed the case
comes from our major SCUBA survey of radio galaxies, which indicates that
massive dust-enshrouded star-formation in at least this subset of massive
ellipticals is largely confined to z > 2.5, with a mean redshift z = 3.5. While
radio selection raises concerns about bias, I argue that our current knowledge
of the brightest (S(850) ~ 10 mJy) sub-mm sources detected in unbiased SCUBA
imaging surveys indicates that they are also largely confined to this same
high-z regime. Consequently, while the most recent number counts imply such
extreme sources can contribute only 5-10% of the sub-mm background, their
comoving number density (in the redshift band 3 < z < 5) is 1-2 x 10^{-5} per
cubic megaparsec, sufficient to account for the formation of all ellipticals of
comparable mass to radio galaxies (~4L-star) in the present-day universe.


title:
Enhanced interactions, mergers and starbursts in dense cluster
  environments

abstract:
  Optical and X-ray studies have established the prevalence of significant
substructure in clusters of galaxies, indicating that clusters are young
systems, and that recent major mergers have occurred in many clusters.
Numerical simulations show that sub-cluster merging will result in significant
tidal forces on disk galaxies in accreting sub-groups, which is likely to lead
to the transformation of spirals to S0s in clusters. Simulations predict
simultaneous moderate starbursts in gas-rich disk galaxies in clusters which
show on-going or recent merger activity, as well as enhanced galaxy-galaxy
interactions and mergers. Observational data from studies of spectral
indicators, both of starburst activity in late-type galaxies in nearby
clusters, and of poststarburst activity in early-type galaxies in nearby and
intermediate redshift clusters, support this scenario.


title:
The Distribution of Dark Matter in Galaxies: Constant-Density Dark Halos
  Envelop the Stellar Disks

abstract:
  In this paper we review the main and the most recent evidence for the
presence of a core radius in the distribution of the dark matter around spiral
galaxies. Their rotation curves, coadded according to the galaxy luminosity,
conform to an Universal profile which can be represented as the sum of an
exponential thin disk term plus a spherical halo term with a flat density core.
  From dwarfs to giants, these halos feature a constant density region of size
r_0 and core density rho_0 related by rho_0= 4.5 10^{-2} (r_0/kpc)^{-2/3}M_sol
pc^{-3}. At the highest masses rho_0 decreases exponentially, with r_0
revealing a lack of objects with disk masses > 10^{11}M_sol and central
densities > 1.5 10^{-2}(r_0/kpc)^{-3} M_sol pc^{-3}, which implies a maximum
mass of ~2 10^{12} M_sol for halos hosting spirals. The fine structure of dark
matter halos is obtained from the kinematics of a number of suitable
low-luminosity disk galaxies. The inferred halo circular velocity increases
linearly with radius out to the edge of the stellar disk, implying a constant
dark halo density over the entire disk region. The structural properties of
halos around normal spirals are similar to those around dwarf and low surface
brightness galaxies; nevertheless they provide far more substantial evidence of
the discrepancy between the mass distributions predicted in the Cold Dark
Matter scenario and those actually detected around galaxies.


title: Monitoring and modeling radio flares from microquasars

abstract:
  We present results of long-term daily monitoring of a sample of Galactic
radio-emitting X-ray binaries showing relativistic jets (RJXRB): SS433, Cyg
X-3, and GRS 1915+105, with the RATAN-600 radio telescope in the 0.6-22 GHz
range. We carried out the modeling calculations to understand the temporal
(1--100 days) and spectral (1-22 GHz) dependence. We tested the finite jet
segment models and we found that the geometry of the conical hollow jets is
responsible for either a power law or an exponential decay of the flares. SS433
was monitored for 100 days in 1997 and 120 days in 1999. From the quiescent
radio light curves, we obtained clear evidence of a 6.04-day 10-15% modulation.
Three powerful flares (up to 13 Jy) from Cyg X-3 were detected in April 2000.


title: The helicity constraint in turbulent dynamos with shear

abstract:
  The evolution of magnetic fields is studied using simulations of forced
helical turbulence with strong imposed shear. After some initial exponential
growth, the magnetic field develops a large scale travelling wave pattern. The
resulting field structure possesses magnetic helicity, which is conserved in a
periodic box by the ideal MHD equations and can hence only change on a
resistive time scale. This constrains strongly the growth time of the large
scale magnetic field, but less strongly the length of the cycle period.
Comparing with the case without shear, the time scale for large scale field
amplification is shortened by a factor Q, which depends on the relative
importance of shear and helical turbulence, and which controls also the ratio
of toroidal to poloidal field. The results of the simulations can be reproduced
qualitatively and quantitatively with a mean-field alpha-Omega dynamo model
with alpha-effect and the turbulent magnetic diffusivity coefficients that are
less strongly quenched than in the corresponding alpha^2-dynamo.


title: Extremely red galaxy counterparts to 7C radio sources

abstract:
  We present RIJHK imaging of seven radio galaxies from the 7C Redshift Survey
(7CRS) which lack strong emission lines and we use these data to investigate
their spectral energy distributions (SEDs) with models which constrain their
redshifts. Six of these seven galaxies have extremely red colours (R-K>5.5) and
we find that almost all of them lie in the redshift range 1<z<2. We also
present near-infrared spectroscopy of these galaxies which demonstrate that
their SEDs are not dominated by emission lines, although tentative lines,
consistent with H-alpha at z=1.45 and z=1.61, are found in two objects.
Although the red colours of the 7CRS galaxies can formally be explained by
stellar populations which are either very old or young and heavily reddened,
independent evidence favours the former hypothesis. At z~1.5 at least 1/4 of
powerful radio jets are triggered in massive (>L*) galaxies which formed the
bulk of their stars several Gyr earlier, that is at epochs corresponding to
redshifts z>5. If a similar fraction of all z~1.5 radio galaxies are old, then
extrapolation of the radio luminosity function shows that, depending on the
radio source lifetimes, between 10-100% of the near-IR selected extremely red
object (ERO) population undergo a radio outburst at epochs corresponding to
1<z<2. An ERO found serendipitously in the field of one of the 7CRS radio
sources appears to be a radio-quiet analogue of the 7CRS EROs with an emission
line likely to be [OII] at z=1.20. The implication is that some of the most
massive elliptical galaxies formed the bulk of their stars at z>5 and these
objects probably undergo at least two periods of AGN activity: one at high
redshift during which the black hole forms and another one at an epoch
corresponding to z~1.5.


title: Nonlinear evolution of r-modes in rotating relativistic stars

abstract:
  A numerical study of nonlinear r-modes in isentropic, rapidly rotating
relativistic stars, via 3-D general-relativistic hydrodynamical evolutions, is
presented. On dynamical timescales, we find no evidence for strong coupling of
r-modes to other modes at amplitudes of order one or larger. Therefore, unless
nonlinear saturation sets in on longer timescales, the maximum r-mode amplitude
is of order one. An absolute upper limit on the amplitude is set by causality.
Our simulations also show that r-modes and inertial modes in isentropic stars
are discrete modes, with no evidence for the existence of a continuous part in
the spectrum.


title: Analysis of CMB foregrounds using a database for Planck

abstract:
  Within the scope of the Planck IDIS (Integrated Data Information System)
project we have started to develop the data model for time-ordered data and
full-sky maps. The data model is part of the Data Management Component (DMC), a
software system designed according to a three-tier architecture which allows
complete separation between data storage and processing. The DMC is already
being used for simulation activities and the modeling of some foreground
components. We have ingested several Galactic surveys into the database and
used the science data-access interface to process the data. The data structure
for full-sky maps utilises the HEALPix tessellation of the sphere. We have been
able to obtain consistent measures of the angular power spectrum of the
Galactic radio continuum emission between 408 MHz and 2417 MHz.


title: Surface photometry of NGC 3077

abstract:
  We present surface photometry of the irregular galaxy NGC 3077 using two data
sets: photographic plates and CCD images. Isophotal contours, luminosity and
colour distributions as well as position angle and ellipticity curves show that
NGC 3077 is similar to an elliptical galaxy in the outer regions with a
disturbed blue centre. The outer isophotes 22-25 mag/arcsec^2 are approximately
centred on the dynamical centre, the inner ones are disturbed by the dominant
contribution of a reddened young population.


title:
XMM- Newton Observation of the Coma Galaxy Cluster: The temperature
  structure in the central region

abstract:
  We present a temperature map and a temperature profile of the central part (r
< 20' or 1/4 virial radius) of the Coma cluster. We combined 5 overlapping
pointings made with XMM/EPIC/MOS and extracted spectra in boxes of 3.5' X 3.5'.
The temperature distribution around the two central galaxies is remarkably
homogeneous (r<10'), contrary to previous ASCA results, suggesting that the
core is actually in a relaxed state. At larger distance from the cluster center
we do see evidence for recent matter accretion. We confirm the cool area in the
direction of NGC 4921, probably due to gas stripped from an infalling group. We
find indications of a hot front in the South West, in the direction of NGC4839,
probably due to an adiabatic compression.


title: Stellar Population analysis from Broad-Band Colours

abstract:
  We have developed an analytical method to investigate the stellar populations
in a galaxy using the broad-band colours. The method enables us to determine
the relative contribution, spatial distribution and age for different stellar
populations and gives a hint about the dust distribution in a galaxy. We apply
this method to the irregular galaxy NGC 3077, using CCD images in U, B, V and R
filters.


title:
Period-Luminosity-Colour distribution and classification of Galactic
  oxygen-rich LPVs II

abstract:
  The kinematic and Period-Luminosity-Colour distribution of O-rich Long-Period
Variable stars of the solar neighbourhood is interpreted in terms of pulsation
modes, masses and metallicities. It is first shown that, because of input
physics imperfections, the periods and mean colours derived from the existing
linear and nonlinear nonadiabatic models must significantly depart from the
actual behaviour of the stars. As a consequence systematic corrections have to
be applied, as a first approximation, to our linear model grid. These free
parameters, as well as the mixing length, are calibrated on the LPVs of the LMC
and of some globular clusters, assuming a mean mass of one solar mass for the
LMC Mira-like stars. Then, the masses and metallicities corresponding to the
four kinematic/photometric populations of local LPVs are evaluated. The
possibility of a varying mixing-length parameter is discussed and taken into
account.


title: Inner disk oscillations

abstract:
  The RXTE observations of GRS 1915+105 have given a new impulse to the study
of spectral and timing properties of the X-ray emission of black hole
candidates. At variance with any other known source, GRS 1915+105 shows
dramatic changes on time scales as short as a tenth of a second. These changes
are associated to marked spectral changes which have been interpreted as
changes of the observable inner radius of the accretion disk. I review the
existing results and discuss the current evidence for such disk oscillations.
Independently of the precise theoretical models, the detailed study of these
fast variations can provide an extremely valuable insight on the accretion
processes onto black holes. Making use of these results, I compare the
properties of GRS 1915+105 with those of other black hole


title:
What May We Learn from Multi-wavelength Observations of Active Galactic
  Nuclei

abstract:
  We discuss how several of the questions that remain unclear on the physics of
Active Galactic Nuclei may find elements of answers when using in the coming
years the extraordinary set of instruments that will be flying simultaneously
to observe in all bands of the electromagnetic spectrum.
  The choice of questions mentioned here is personal and not exhaustive.


title: On the Origin of the Fanaroff-Riley Dichotomy

abstract:
  A small fraction of double radio sources show a peculiar and striking hybrid
morphology; they have a distinctly FR I structure on one side of the nucleus,
and a FR II structure on the other. We argue that the mere existence of these
HYMORS is quite incompatible with the theoretical explanations for the
Fanaroff-Riley dichotomy that are based upon the nature of the jet plasma, or
those invoking an intrinsic property of the central engine. Rather, these
HYMORS strongly support models that explain the difference between FR I and FR
II sources in terms of asymmetry of interaction of the jets with the external
environments. We further show that a model for radio source dynamics we had
earlier proposed can neatly reproduce the observed dependence of the radio
power dividing the two FR classes on the optical luminosity of the host galaxy,
as found by Owen & White and Ledlow & Owen


title:
The DEEP Groth Strip Survey X: Number Density and Luminosity Function of
  Field E/S0 Galaxies at z < 1

abstract:
  We present the luminosity function and color-redshift relation of a
magnitude-limited sample of 145 mostly red field E/S0 galaxies at z < 1 from
the DEEP Groth Strip Survey (GSS). Most of the E/S0s (86%) form a red envelope
in the redshift-color diagram, consistent with predictions of spectral
synthesis models in which the dominant stellar population is formed at
redshifts z > 1.5. Constructing a luminosity function of the full sample of
  145 E/S0s, we find that there is about 1.1--1.9 magnitude brightening in
rest-frame B band luminosity back to z = 0.8 from z=0, consistent with other
studies.
  Together with the red colors, this brightening favors models in which the
bulk of stars in red field E/S0s formed before z_{for} > 1.5 and have been
evolving rather quiescently with few large starbursts since then.
  Evolution in the number density of field E/S0 galaxies is harder to measure,
and uncertainties in the raw counts and their ratio to local samples might
amount to as much as a factor of two.
  Within that uncertainty, the number density of red E/S0s to z = 0.8 seems
relatively static, being comparable to or perhaps moderately less than that of
local E/S0s depending on the assumed cosmology. A doubling of E/S0 number
density since z = 1 can be ruled out with high confidence (97%) if
\Omega_{m}=1.
  Taken together, our results are consistent with the hypothesis that the
majority of luminous field E/S0s were already in place by z = 1, that the bulk
of their stars were already fairly old, and that their number density has not
changed by large amounts since then.


title:
New Observations of Extra-Disk Molecular Gas in Interacting Galaxy
  Systems, Including a Two-Component System in Stephan's Quintet

abstract:
  We present new CO (1 - 0) observations of eleven extragalactic tails and
bridges in nine interacting galaxy systems, almost doubling the number of such
features with sensitive CO measurements. Eight of these eleven features were
undetected in CO to very low CO/HI limits, with the most extreme case being the
NGC 7714/5 bridge. This bridge contains luminous H II regions and has a very
high HI column density (1.6 X 10^21 cm^-2 in the 55" CO beam), yet was
undetected in CO to rms T(R)* = 2.4 mK. The HI column density is higher than
standard H2 and CO self-shielding limits for solar-metallicity gas, suggesting
that the gas in this bridge is metal-poor and has an enhanced N(H2)/I(CO) ratio
compared to the Galactic value. Only one of the eleven features in our sample
was unambiguously detected in CO, a luminous HI-rich star formation region near
an optical tail in the compact group Stephan's Quintet. We detect CO at two
widely separated velocities in this feature, at ~6000 km/s and ~6700 km/s. Both
of these components have HI and H-alpha counterparts. These velocities
correspond to those of galaxies in the group, suggesting that this gas is
material that has been removed from two galaxies in the group. The
CO/HI/H-alpha ratios for both components are similar to global values for
spiral galaxies.


title: Stellar population synthesis models at low and high redshift

abstract:
  The basic assumptions behind Population Synthesis and Spectral Evolution
models are reviewed. The numerical problems encountered by the standard
population synthesis technique when applied to models with truncated star
formation rates are described. The Isochrone Synthesis algorithm is introduced
as a means to circumvent these problems. A summary of results from the
application of this algorithm to model galaxy spectra by Bruzual and Charlot
(1993, 2000) follows. I present a comparison of these population synthesis
model predictions with observed spectra and color magnitude diagrams for
stellar systems of various ages and metallicities. It is argued that models
built using different ingredients differ in the resulting values of some basic
quantities (e.g. $M/L_V$), without need to invoking violations of physical
principles. The range of allowed colors in the observer frame is explored for
several galaxy redshifts.


title: CMB Signatures of a Primordial Magnetic Field

abstract:
  A primordial stochastic magnetic field will induce temperature and
polarization fluctuations in the cosmic microwave background. We outline a
calculation of the resulting fluctuation power spectra and present numerical
results.


title: LRG J0239-0134: A Ring Galaxy or a Pair of Superbubbles at z=1 ?

abstract:
  The unusual morphology of LRG J0239$-$0134 at $z$ =1.062 has been interpreted
as a ring galaxy. Here we propose an alternative idea that the ring-like
morphology is attributed to a pair of superbubbles driven by the intense
starburst in the central region of this galaxy. Supporting evidence for a
superbubble model is; 1) the poststarburst nature in the central body suggests
that a burst of supernova explosions could occur at least $\sim 10^7$ yr ago,
2) the dark lane seen in the central body suggests that we observe this object
from a nearly edge-on view, and, 3) the ring-like morphology is not
inconsistent with an idea that it is a pair of superbubbles. All these pieces
of evidence for the superbubble model seem circumstantial. However, if this is
the case, this galaxy provides an important example of the superwind activity
at high redshift.


title:
Local Dynamical Instabilities in Magnetized, Radiation Pressure
  Supported Accretion Disks

abstract:
  We present a general linear dispersion relation which describes the coupled
behavior of magnetorotational, photon bubble, and convective instabilities in
weakly magnetized, differentially rotating accretion disks. We presume the
accretion disks to be geometrically thin and supported vertically by radiation
pressure. We fully incorporate the effects of a nonzero radiative diffusion
length on the linear modes. In an equilibrium with purely vertical magnetic
field, the vertical magnetorotational modes are completely unaffected by
compressibility, stratification, and radiative diffusion. However, in the
presence of azimuthal fields, which are expected in differentially rotating
flows, the growth rate of all magnetorotational modes can be reduced
substantially below the orbital frequency. This occurs if diffusion destroys
radiation sound waves on the length scale of the instability, and the magnetic
energy density of the azimuthal component exceeds the non-radiative thermal
energy density. While sluggish in this case, the magnetorotational instability
still persists and will still tap the free energy of the differential rotation.
Photon bubble instabilities are generically present in radiation pressure
dominated flows where diffusion is present. We show that their growth rates are
limited to a maximum value which is reached at short wavelengths where the
modes may be viewed as unstable slow magnetosonic waves. We also find that
vertical radiation pressure destabilizes upward propagating fast waves, and
that Alfv\'en waves can be unstable. These instabilities typically have smaller
growth rates than the photon bubble/slow modes. We discuss how all these modes
behave in various regimes of interest, and speculate how they may affect the
dynamics of real accretion disk flows.


title:
The Interaction between the ISM and Star Formation in the Dwarf
  Starburst Galaxy NGC 4214

abstract:
  We present the first interferometric study of the molecular gas in the
metal-poor dwarf starburst galaxy NGC 4214. Our map of the 12CO(1-0) emission,
obtained at the OVRO millimeter array, reveals an unexpected structural wealth.
We detected three regions of molecular emission in the north-west (NW),
south-east (SE) and centre of NGC 4214 which are in very different and distinct
evolutionary stages (total molecular mass: 5.1 x 10^6 M_sun). These differences
are apparent most dramatically when the CO morphologies are compared to optical
ground based and HST imaging: massive star formation has not started yet in the
NW region; the well-known starburst in the centre is the most evolved and star
formation in the SE complex started more recently. We derive a star formation
efficiency of 8% for the SE complex. Using high--resolution VLA observations of
neutral hydrogen HI and our CO data we generated a total gas column density map
for NGC 4214 (HI + H_2). No clear correlation is seen between the peaks of HI,
CO and the sites of ongoing star formation. This emphasizes the irregular
nature of dwarf galaxies. The HI and CO velocities agree well, so do the
H-alpha velocities. In total, we cataloged 14 molecular clumps in NGC 4214. Our
results from a virial mass analysis are compatible with a Galactic CO-to-H_2
conversion factor for NGC 4214 (lower than what is usually found in metal-poor
dwarf galaxies).


title: On the multi-periodicities in the X-ray dipper XB 1916-053

abstract:
  Using the Rossi X-ray Timing Explorer and the Nordic Optical Telescope we
have obtained the highest ever quality X-ray/white-light high-speed photometry
of XB 1916-053. We refine the X-ray period (P_X) to 3000.6+/-0.2s via a
restricted cycle counting approach. Using our complete optical lightcurve, we
have extended the optical period (P_opt) ephemeris by another 4 years,
providing further evidence for its stability, although a slightly longer period
of 3027.555+/-0.002s now provides a marginally better fit. Moreover,
modulations at both P_X and P_opt are present in the optical data, with the
former dominating the nightly lightcurves (i.e. a few cycles of data). We have
also attempted to determine the ``beat'' period, as seen in the repeating
evolution of the X-ray dip structure, and the variation in primary dip phase.
We find that a quasi-period of 4.74+/-0.05d provides the best fit to the data,
even then requiring phase shifts between cycles, with the expected 3.90d
``beat'' of P_X and P_opt appearing to be less likely.
  Finally, considering the nature of each of these temporal phenomena, we
outline possible models, which could explain all of the observed behaviour of
this enigmatic source, focusing on which of P_X or P_opt is the binary period.


title:
Detection of Intracluster Gas Bulk Velocities in the Perseus and
  Centaurus Clusters

abstract:
  We report the results of spatially resolved X-ray spectroscopy of 8 different
ASCA pointings distributed symmetrically around the center of the Perseus
cluster. The outer region of the intracluster gas is roughly isothermal, with
temperature ~6-7 keV, and metal abundance ~ 0.3 Solar. Spectral analysis of the
central pointing is consistent with the presence of a cooling flow and a
central metal abundance gradient.
  A significant velocity gradient is found along an axis highly discrepant with
the major axis of the X-ray elongation. The radial velocity difference is found
to be greater than 1000 km/sMpc at the 90% confidence level. Simultaneous
fittings of GIS 2 & 3 indicate that two symmetrically opposed regions have
different radial velocities at the 95% confidence level and the F-test rules
out constant velocities for these regions at the 99% level. Intrinsic short and
long term variations of gain are unlikely (P < 0.03) to explain the velocity
discrepancies. We also report the preliminary results of a similar analysis
carried out for the Centaurus cluster, where long-exposure SIS data is
available. We also find a significant velocity gradient near the central
regions (3'-8') of Centaurus. If attributed to bulk rotation the correspondent
circular velocity is ~1500+-150km/s (at 90% confidence). The line of maximum
velocity gradient in Centaurus is near-perpendicular to the infalling galaxy
group associated with NGC 4709.


title:
Ultraviolet Signposts of Resonant Dynamics in the Starburst-Ringed Sab
  Galaxy, M94 (NGC 4736)

abstract:
  M94 (NGC 4736) is investigated using images from the Ultraviolet Imaging
Telescope (FUV-band), Hubble Space Telescope (NUV-band), Kitt Peak 0.9-m
telescope (H-alpha, R, and I bands), and Palomar 5-m telescope (B-band), along
with spectra from the International Ultraviolet Explorer and Lick 1-m
telescopes. The wide-field UIT image shows FUV emission from (a) an elongated
nucleus, (b) a diffuse inner disk, where H-alpha is observed in absorption, (c)
a bright inner ring of H II regions at the perimeter of the inner disk (R = 48
arcsec. = 1.1 kpc), and (d) two 500-pc size knots of hot stars exterior to the
ring on diametrically opposite sides of the nucleus (R= 130 arcsec. = 2.9 kpc).
The HST/FOC image resolves the NUV emission from the nuclear region into a
bright core and a faint 20 arcsec. long ``mini-bar'' at a position angle of 30
deg. Optical and IUE spectroscopy of the nucleus and diffuse inner disk
indicates an approximately 10^7 or 10^8 yr-old stellar population from
low-level starbirth activity blended with some LINER activity. Analysis of the
H-alpha, FUV, NUV, B, R, and I-band emission along with other observed tracers
of stars and gas in M94 indicates that most of the star formation is being
orchestrated via ring-bar dynamics involving the nuclear mini-bar, inner ring,
oval disk, and outer ring. The inner starburst ring and bi-symmetric knots at
intermediate radius, in particular, argue for bar-mediated resonances as the
primary drivers of evolution in M94 at the present epoch. Similar processes may
be governing the evolution of the ``core-dominated'' galaxies that have been
observed at high redshift. The gravitationally-lensed ``Pretzel Galaxy''
(0024+1654) at a redshift of approximately 1.5 provides an important precedent
in this regard.


title:
Detectability of the Parallax-induced Deviations in the Astrometric
  Centroid Shift Trajectories of Gravitational Microlensing Events

abstract:
  The uncertainty of the lens mass can be substantially reduced if it is
determined from the lens proper motion obtained from astrometric measurements
of the source image centroid shifts, $\vdelta\vtheta_c$, by using high
precision interferometers. However, for the complete resolution of the lens
parameter degeneracy it is required to determine the lens parallax by measuring
the parallax-induced deviations in the centroid shifts trajectory, $\vDelta
\vdelta \vtheta_c$. In this paper, we investigate the detectabilities of
$\vdelta\vtheta_c$ and $\vDelta\vdelt\vtheta_c$ by determining the
distributions of the maximum centroid shifts and the average maximum deviations
expected for different types of Galactic microlensing events caused by various
masses. From this investigation, we find that as long as sources are bright
enough for astrometric observations it is expected that $\vdeltavxtheta_c$ for
most events caused by masses greater than 0.1 M_\odot regardless of the event
types can be easily detected from observations by using not only the Space
Interfeormetry Mission (SIM, with a detection threshold ~ 3 \mu-as) but also
the ground-based interferometers (with a threshold ~30 \mu-as). However,
detection of $\vDelta\vdelta\vtheta_c$ from ground-based observations will be
difficult for nearly all Galactic bulge self-lensing events, and will be
restricted only for small fractions of disk-bulge and halo-LMC events, for
which the deviations are relatively large. From observations by using the SIM,
on the other hand, detecting $\vDelta\vdelta\vtheta_c$ will be possible for
majority of disk-bulge and halo-LMC events and even for some fraction of bulge
self-lensing events. For the complete resolution of the lens parameter
degeneracy, therefore, SIM observations (or equivalent) will be essential.


title:
Dynamics of low-energy nuclear forces and Solar Neutrino Problems in the
  Nambu-Jona-Lasinio model of light nuclei

abstract:
  The Solar Neutrino Problems (SNP's) are analysed in the Nambu-Jona-Lasinio
model of light nuclei. In this model a possible clue to the solution of the
SNP's is in the reduction of the solar neutrino fluxes relative to the
predicted by the Standard Solar Model through the decrease of the solar core
temperature. The former can be realized through the enhancement of the
astrophysical factor for the solar proton burning. The enhancement the upper
bound of which is restricted by the helioseismological data goes dynamically
via the contribution of the nucleon tensor current coupled to the deuteron. The
agreement of the reduced solar neutrino fluxes with the experimental data can
be reached within a scenario of vacuum two-flavour neutrino oscillations
without a fine tuning of the neutrino-flavour oscillation parameters. In the
Nambu-Jona-Lasinio model of light nuclei an enhancement of the astrophysical
factor for the solar proton burning entails a change of the cross sections for
neutrino and anti-neutrino disintegration of the deuteron at low energies. This
provides a theoretical foundation for a new check of a value of the
astrophysical factor in terrestrial laboratories.


title:
Microslit Nod-shuffle Spectroscopy - a technique for achieving very high
  densities of spectra

abstract:
  We describe a new approach to obtaining very high surface densities of
optical spectra in astronomical observations with extremely accurate
subtraction of night sky emission. The observing technique requires that the
telescope is nodded rapidly between targets and adjacent sky positions; object
and sky spectra are recorded on adjacent regions of a low-noise CCD through
charge shuffling. This permits the use of extremely high densities of small
slit apertures (`microslits') since an extended slit is not required for sky
interpolation. The overall multi-object advantage of this technique is as large
as 2.9x that of conventional multi-slit observing for an instrument
configuration which has an underfilled CCD detector and is always >1.5 for high
target densities. The `nod-shuffle' technique has been practically implemented
at the Anglo-Australian Telescope as the `LDSS++ project' and achieves
sky-subtraction accuracies as good as 0.04%, with even better performance
possible. This is a factor of ten better than is routinely achieved with
long-slits. LDSS++ has been used in various observational modes, which we
describe, and for a wide variety of astronomical projects. The nod-shuffle
approach should be of great benefit to most spectroscopic (e.g. long-slit,
fiber, integral field) methods and would allow much deeper spectroscopy on very
large telescopes (10m or greater) than is currently possible. Finally we
discuss the prospects of using nod-shuffle to pursue extremely long
spectroscopic exposures (many days) and of mimicking nod-shuffle observations
with infrared arrays.


title: Where is the [O III]4363 emitting region in active galactic nuclei?

abstract:
  The emission-line flux ratio of [O III]4363/[O III]5007 (R_OIII)is a useful
diagnostic for the ionization mechanism and physical properties of
emission-line regions in active galactic nuclei (AGNs). However, it is known
that simple photoionization models underpredict the [O III]4363 intensity,
being inconsistent with observations. In this paper, we report on several
pieces of evidence that a large fraction of the [O III]4363 emission arises
from the dense gas obscured by putative tori: (1) the visibility of high-R_OIII
regions is correlated to that of broad-line regions, (2) higher-R_OIII objects
show hotter mid-infrared colors, (3) higher-R_OIII objects show stronger
highly-ionized emission lines such as [Fe VII]6087 and [Fe X]6374, and (4)
higher-R_OIII objects have broader line width of [O III]4363 normalized by that
of [O III]5007. To estimate how such a dense component contributes to the total
emission-line flux, dual-component photoionization model calculations are
performed. It is shown that the observed values of R_OIII of type 1 AGNs may be
explained by introducing a 5% - 20% contribution from the dense component while
those of type 2 AGNs may be explained by introducing a 0% - 2% contribution. We
also discuss the [O III]4363 emitting regions in LINERs in the framework of our
dual-component model.


title: From the Galaxy to the Edge of the Universe: Plausible Sources of UHECRs

abstract:
  The lack of a high energy cutoff in the cosmic ray spectrum together with an
apparently isotropic distribution of arrival directions for the highest energy
events have strongly constrained most models proposed for the generation of
these particles. An overview of the theoretical proposals are presented along
with their most general signatures. Future experimental tests of the different
proposals are discussed.


title: Maximally incompressible neutron star matter

abstract:
  Relativistic kinetic theory, based on the Grad method of moments as developed
by Israel and Stewart, is used to model viscous and thermal dissipation in
neutron star matter and determine an upper limit on the maximum mass of neutron
stars. In the context of kinetic theory, the equation of state must satisfy a
set of constraints in order for the equilibrium states of the fluid to be
thermodynamically stable and for perturbations from equilibrium to propagate
causally via hyperbolic equations. Application of these constraints to neutron
star matter restricts the stiffness of the most incompressible equation of
state compatible with causality to be softer than the maximally incompressible
equation of state that results from requiring the adiabatic sound speed to not
exceed the speed of light. Using three equations of state based on experimental
nucleon-nucleon scattering data and properties of light nuclei up to twice
normal nuclear energy density, and the kinetic theory maximally incompressible
equation of state at higher density, an upper limit on the maximum mass of
neutron stars averaging 2.64 solar masses is derived.


title:
The Density Probability Distribution Function in Turbulent, Isothermal,
  Magnetized Flows in Slab Geometry

abstract:
  We investigate the behavior of the magnetic pressure, $b^2$, in fully
turbulent MHD flows in ``1+2/3'' dimensions by means of its effect on the
probability density function (PDF) of the density field. We start by reviewing
our previous results for general polytropic flows, according to which the value
of the polytropic exponent $\gamma$ determines the functional shape of the PDF.
A lognormal density PDF appears in the isothermal ($\gamma=1$) case, but a
power-law tail at either large or small densities appears for large Mach
numbers when $\gamma >1$ and $\gamma < 1$, respectively. In the isothermal
magnetic case, the relevant parameter is the field fluctuation amplitude,
$\dbb$. A lognormal PDF still appears for small field fluctuations (generally
the case for {\it large mean fields}), but a significant low-density excess
appears at large fluctuation amplitudes ({\it weak mean fields}), similar to
the behavior at $\gamma > 1$ of polytropic flows. We interpret these results in
terms of simple nonlinear MHD waves, for which the magnetic pressure behaves
linearly with the density in the case of the slow mode, and quadratically in
the case of the fast wave. Finally, we discuss some implications of these
results, in particular the fact that the effect of the magnetic field in
modifying the PDF is strongest when the mean field is weak.


title:
The Dyer-Roeder distance in quintessence cosmology and the estimation of
  H_0 through time-delays

abstract:
  We calculate analytically and numerically the Dyer-Roeder distance in perfect
fluid quintessence models and give an accurate fit to the numerical solutions
for all the values of the density parameter and the quintessence equation of
state. Then we apply our solutions to the estimation of $H_{0}$ from multiple
image time delays and find that the inclusion of quintessence modifies sensibly
the likelihood distribution of $H_{0}$, generally reducing the best estimate
with respect to a pure cosmological constant. Marginalizing over the other
parameters ($\Omega_{m}$ and the quintessence equation of state), we obtain
$H_{0}=71\pm 6$ km/sec/Mpc for an empty beam and $H_{0}=64\pm 4$ km/sec/Mpc for
a filled beam. We also discuss the future prospects for distinguishing
quintessence from a cosmological constant with time delays.


title:
New class of low frequency QPOs: signature of nuclear burning or
  accretion disk instabilities?

abstract:
  We report the discovery of a new class of low frequency quasi--periodic
variations of the X-ray flux in the X-ray bursters 4U1608-52 and 4U1636-536. We
also report an occasional detection of a similar QPO in Aql X-1. The QPOs,
associated with flux variations at the level of percents, are observed at a
frequency of 7-9 mHz. While usually the relative amplitude of flux variations
increases with energy, the newly discovered QPOs are limited to the softest
energies (1-5 keV). The observations of 4U1608-52 suggest that these QPOs are
present only when the source X-ray luminosity is within a rather narrow range
and they disappear after X-ray bursts. Approximately at the same level of the
source luminosity, type I X-ray bursts cease to exist.
  Judging from this complex of properties, we speculate that a special mode of
nuclear burning at the neutron star surface is responsible for the observed
flux variations. Alternatively, some instabilities in the accretion disk may be
responsible for these QPOs.


title:
Eclipsing Broad Emission Lines in Hercules X-1: Evidence for a Disk
  Wind?

abstract:
  We present disk wind model calculations for the broad emission lines seen in
the ultraviolet spectra of the X-ray binary Hercules X-1. Recent HST/STIS
observations of these lines suggest that they are kinematically linked to the
orbital motion of the neutron star and exhibit a red-shifted to blue-shifted
evolution of the line shape during the progression of the eclipse from ingress
to egress which is indicative of disk emission. Furthermore, these lines are
single-peaked which implies that they may be formed in a disk wind similar to
those we have proposed as producing the broad emission lines seen in the UV
spectra of active galactic nuclei. We compute line profiles as a function of
eclipse phase and compare them to the observed line profiles. Various effects
may modify the appearance of the lines including resonant scattering in the
wind itself, self-shadowing of the warped disk from the central continuum, and
self-obscuration of parts of the disk along the observer's line-of-sight. These
latter two effects can cause orbital and precessional phase dependent
variations in the emission lines. Hence, examination of the line profiles as a
function of these phases can, in principle, provide additional information on
the characteristics of the disk warp.


title: A Near-Infrared Imaging Survey of the Chamaeleon I Dark Cloud

abstract:
  We describe a near-infrared imaging survey covering approximately 1 square
deg of the Chamaeleon I dark cloud. The survey is complete for K < 15.0, H <
16.0, and J < 16.5, roughly two magnitudes more sensitive than previous large
scale surveys. We use the large number of background stars detected to derive
an accurate near-infrared extinction law for the cloud and select new candidate
members with near-infrared color excesses. We list about 100 candidates of the
cloud with K > 12.0, based on their positions in the J-H, H-K color-color
diagram. These new stars have low luminosities (K > 12 -- 16, H-K > 0.5 -- 1.5)
and may have masses close to or even below the hydrogen burning limit.


title: Structure of the Galactic Stellar Halo Prior to Disk Formation

abstract:
  We develop a method for recovering the global density distribution of the
ancient Galactic stellar halo prior to disk formation, based on the present
orbits of metal-poor stars observed in the solar neighborhood. The method
relies on the adiabatic invariance of the action integrals of motion for the
halo population during the slow accumulation of a disk component, subsequent to
earlier halo formation. The method is then applied to a sample of local stars
with [Fe/H]<=-1.5, likely to be dominated by the halo component, taken from
Beers et al.'s recently revised and supplemented catalog of metal-poor stars
selected without kinematic bias. We find that even if the Galactic potential is
made spherical by removing the disk component in an adiabatic manner, the halo
density distribution in the inner halo region (R <= 15 kpc) remains moderately
flattened, with axial ratio of about 0.8 for stars in the abundance range
[Fe/H]<=-1.8 and about 0.7 for the more metal-rich interval -1.8<[Fe/H]<=-1.5.
The outer halo remains spherical for both abundance intervals. We also find
that this initial flattening of the inner halo is caused by the anisotropic
velocity dispersions of the halo stars. These results suggest that the
two-component nature of the present-day stellar halo, characterized by a highly
flattened inner halo and nearly spherical outer halo, is a consequence of both
an initially two-component density distribution of the halo (perhaps a
signature of dissipative halo formation) and of the adiabatic flattening of the
inner part by later disk formation. Further implications of our results for the
formation of the Galaxy are also discussed, in particular in the context of the
hierarchical clustering scenario of galaxy formation.


title: A shock-excited OH maser in a post-AGB envelope ?

abstract:
  We have observed a sample of OH 1612-MHz masing objects in all four OH
ground--state transitions with the Australia Telescope Compact Array. One
likely post-AGB object is found to emit in the 1612-MHz, 1665-MHz and 1720-MHz
transitions. We discuss the evidence that this object may be an early post-AGB
object and the possibility for such a circumstellar envelope to harbour a
1720-MHz maser. We argue that during a very brief period, just after the star
has left the thermally-pulsing phase of the AGB and the wind velocity starts to
increase, post-AGB objects might show \sath emission. The best objects to
search for such emission would be those that are masing at 1612 MHz and 1665
MHz, but not at 1667 MHz nor in the 22-GHz H2O transition.


title: Star Forming Objects in the Tidal Tails of Compact Groups

abstract:
  A search for star forming objects belonging to tidal tails has been carried
out in a sample of deep Halpha images of 16 compact groups of galaxies. A total
of 36 objects with Halpha luminosity larger than 10^38 erg s-1 have been
detected in five groups. The fraction of the total Halpha luminosity of their
respective parent galaxies shown by the tidal objects is always below 5% except
for the tidal features of HCG95, whose Halpha luminosity amounts to 65% of the
total luminosity. Out of this 36 objects, 9 star forming tidal dwarf galaxy
candidates have been finally identified on the basis of their projected
distances to the nuclei of the parent galaxies and their total Halpha
luminosities. Overall, the observed properties of the candidates resemble those
previously reported for the so-called tidal dwarf galaxies.


title: Disk-corona interactions in soft spectral states of black hole binaries

abstract:
  Re-analysis of some archival X-ray data of black hole binaries in soft
spectral states is presented. Results of detailed spectral fitting, including
proper physical description of the X-ray reprocessed component, indicate that
in most cases the soft, thermal disk emission cannot be described by a simple
multi-color blackbody model. Additional Comptonization of those seed photons
provides an acceptable description of the soft component, implying a presence
of a warm (kT~1 keV), mildly optically thick (tau~10) phase of accreting
plasma.
  Combined spectral/temporal analysis of GS 1124-68 during 'flip-flop'
transitions in Very High State suggests that the optically thick accretion flow
can proceed in (at least) two modes giving the same time-integrated behaviour
(i.e. energy spectra) but very different timing behaviour.


title: XMM-Newton EPIC Observation of SMC SNR 0102-72.3

abstract:
  Results from observations of the young oxygen-rich supernova remnant SNR
0102-72.3 in the Small Magellanic Cloud during the calibration phase of the
XMM-Newton Observatory are presented. Both EPIC-PN and MOS observations show a
ringlike structure with a radius of ~15'' already known from Einstein, ROSAT
and Chandra observations. Spectra of the entire SNR as well as parts in the
eastern half were analyzed confirming shocked hot plasma in non-uniform
ionization stages as the origin of the X-ray emission. The spectra differ in
the northeastern and the southeastern part of the X-ray ring, showing emission
line features of different strength. The temperature in the northeastern part
is significantly higher than in the southeast, reflected by the lines of higher
ionization stages and the harder continuum. Comparison to radio data shows the
forward shock of the blast wave dominating in the northern part of the SNR,
while the southern emission is most likely produced by the recently formed
reverse shock in the ejecta. In the case of the overall spectrum of SNR
0102-72.3, the two-temperature non-equilibrium ionization model is more
consistent with the data in comparison to the single plane-parallel shock
model. The structure of SNR 0102-72.3 is complex due to variations in shock
propagation leading to spatially differing X-ray spectra.


title:
The heavy-element abundances of AGB stars and the angular momentum
  conservation model of wind accretion for barium stars

abstract:
  Adpoting new s-process nucleosynthesis scenario and branch s-process path, we
calculate the heavy-element abundances and C/O ratio of solar metallicity
3M_sun TP-AGB stars. The evolutionary sequence from M to S to C stars of AGB
stars is explained naturally by the calculated results. Then combining the
angular momentum conservation model of wind accretion with the heavy-element
abundances on the surface of TP-AGB stars, we calculate the heavy-element
overabundances of barium stars via successive pulsed accreting and mixing. Our
results support that the barium stars with longer orbital period, P>1600 days,
form through wind accretion scenario.


title:
UV observations of the galaxy cluster Abell 1795 with the optical
  monitor on XMM-Newton

abstract:
  We present the results of an analysis of broad band UV observations of the
central regions of Abell 1795 observed with the optical monitor on XMM-Newton.
As have been found with other UV observations of the central regions of
clusters of galaxies, we find evidence for star formation. However, we also
find evidence for absorption in the cD galaxy on a more extended scale than has
been seen with optical imaging. We also report the first UV observation of part
of the filamentary structure seen in H$\alpha$, X-rays and very deep U band
imaging. The part of the filament we see is very blue with UV colours
consistent with a very early (O/B) stellar population. This is the first direct
evidence of a dominant population of early type stars at the centre of Abell
1795 and implies very recent star formation at the centre of this cluster


title:
Orbital elements of barium stars formed through a wind accretion
  scenario

abstract:
  Taking the total angular momentum conservation in place of the tangential
momentum conservation, and considering the square and higher power terms of
orbital eccentricity e, the changes of orbital elements of binaries are
calculated for wind accretion scenario. These new equations are used to
quantitatively explain the observed (e,logP) properties of normal G, K giants
and barium stars. Our results reflect the evolution from G, K giant binaries to
barium binaries, moreover, the barium stars with longer orbital periods P>1600
days may be formed by accreting part of the ejecta from the intrinsic AGB stars
through wind accretion scenario.