title:
The 2dF QSO Redshift Survey - II. Structure and evolution at high
  redshift

abstract:
  We present a clustering analysis of QSOs over the redshift range z=0.3-2.9.
We use a sample of 10558 QSOs taken from the preliminary catalogue of the 2dF
QSO Redshift Survey (2QZ). The two-point redshift-space correlation function of
QSOs is shown to follow a power law on scales s~1-35h-1Mpc. Fitting a power law
to QSO clustering averaged over the redshift interval 0.3<z<2.9 we find
s_0=3.99+0.28-0.34h-1Mpc and gamma=1.58+0.10-0.09 for an Einstein-de Sitter
cosmology (EdS). With Omega_0=0.3 and lambda_0=0.7 the power law extends to
s~60h-1Mpc with a best fit of s_0=5.69+0.42-0.50h-1Mpc and
gamma=1.56+0.10-0.09. These values, measured at a mean redshift of z=1.49, are
comparable to the clustering of local optically selected galaxies. We measure
the evolution of QSO clustering as a function of redshift. For an EdS cosmology
there is no evolution in comoving coordinates over the redshift range of the
2QZ. For Omega_0=0.3 and lambda_0=0.7 QSO clustering shows a marginal increase
at high redshift. Although the clustering of QSOs is measured on large scales
where linear theory should apply, the evolution of QSO clustering does not
follow the linear theory predictions for growth via gravitational instability
(rejected at the >99 per cent confidence level). A redshift dependent bias is
required to reconcile QSO clustering observations with theory. A simple biasing
model, in which QSOs have cosmologically long lifetimes (or alternatively form
in peaks above a constant threshold in the density field) is acceptable in an
EdS cosmology, but is only marginally acceptable if Omega_0=0.3 and
lambda_0=0.7. Biasing models which assume QSOs form over a range in redshift,
based on the Press-Schechter formalism are approximately consistent with QSO
clustering evolution (abridged).


title:
Final Results from the Hubble Space Telescope Key Project to Measure the
  Hubble Constant

abstract:
  We present here the final results of the Hubble Space Telescope Key Project
to measure the Hubble constant. We summarize our method, the results and the
uncertainties, tabulate our revised distances, and give the implications of
these results for cosmology. The analysis presented here benefits from a number
of recent improvements and refinements, including (1) a larger LMC Cepheid
sample to define the fiducial period-luminosity (PL) relations, (2) a more
recent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration,
(3) a correction for Cepheid metallicity, and (4) a correction for
incompleteness bias in the observed Cepheid PL samples. New, revised distances
are given for the 18 spiral galaxies for which Cepheids have been discovered as
part of the Key Project, as well as for 13 additional galaxies with published
Cepheid data. The new calibration results in a Cepheid distance to NGC 4258 in
better agreement with the maser distance to this galaxy. Based on these revised
Cepheid distances, we find values (in km/sec/Mpc) of H0 = 71 +/- 2 (random) +/-
6 (systematic) (type Ia supernovae), 71 +/- 2 +/- 7 (Tully-Fisher relation), 70
+/- 5 +/- 6 (surface brightness fluctuations), 72 +/- 9 +/- 7 (type II
supernovae), and 82 +/- 6 +/- 9 (fundamental plane). We combine these results
for the different methods with 3 different weighting schemes, and find good
agreement and consistency with H0 = 72 +/- 8. Finally, we compare these results
with other, global methods for measuring the Hubble constant.


title: A revised Cepheid distance to NGC 4258 and a test of the distance scale

abstract:
  In a previous paper (Maoz et al. 1999), we reported a Hubble Space Telescope
(HST) Cepheid distance to the galaxy NGC 4258 obtained using the calibrations
and methods then standard for the Key Project on the Extragalactic Distance
Scale. Here, we reevaluate the Cepheid distance using the revised Key Project
procedures described in Freedman et al. (2001). These revisions alter the zero
points and slopes of the Cepheid Period-Luminosity (P-L) relations derived at
the Large Magellanic Cloud (LMC), the calibration of the HST WFPC2 camera, and
the treatment of metallicity differences. We also provide herein full
information on the Cepheids described in Maoz et al. 1999. Using the refined
Key Project techniques and calibrations, we determine the distance modulus of
NGC 4258 to be 29.47 +/- 0.09 mag (unique to this determination) +/- 0.15 mag
(systematic uncertainties in Key Project distances), corresponding to a metric
distance of 7.8 +/- 0.3 +/- 0.5 Mpc and 1.2 sigma from the maser distance of
7.2 +/- 0.5 Mpc. We also test the alternative Cepheid P-L relations of Feast
(1999), which yield more discrepant results. Additionally, we place weak limits
upon the distance to the LMC and upon the effect of metallicity in Cepheid
distance determinations.


title: Cooling a Hot Disk Around a Supermassive Black Hole by a Star

abstract:
  If a supermassive black hole resides in the centers of galaxies, there are
several effects expected to be observed. It is likely that accretion disks are
around the supermassive black hole. Stellar interactions with the accretion
flows around the supermassive black hole play a role in that an flying-by star
may cool a hot accretion disk as a result of Comptonization. It is shown that
the Comptonization of the stellar emission will take place in a hot accretion
disk such as the ADAFs around the supermassive black hole and become a
relatively important source of the accretion disk cooling when the mass
accretion rate is low, and stars are passing outer parts of the hot accretion
disk. We suggest that such a stellar cooling can be observed in the radio
frequency regime since synchrotron luminosity of the ADAFs depends strongly on
the electron temperature and occurs much more frequently than a tidal
disruption event.


title: The standstill luminosity in Z Cam systems

abstract:
  We consider accretion discs in close binary systems. We show that heating of
a disc at the impact point of the accretion stream contributes significantly to
the local energy budget at its outer edge. As a result the thermal balance
relation between local accretion rate and surface density (the `S-curve')
changes; the critical mass transfer rate above which no dwarf nova outbursts
occur can be up to 40% smaller than without impact heating. Standstills in ZCam
systems thus occur at smaller mass transfer rates than otherwise expected, and
are rather fainter than the peak luminosity during the dwarf nova phase as a
result.


title: Galactic Black HOle Binary Systems

abstract:
  I review observations of the X-ray spectra of Galactic Black Hole Candidates,
and theoretical ideas as to how these can be produced. X-ray reflection should
enable different source geometries to be distinguished, but the ionisation
instability of X-ray irradiated material in hydrostatic equilibrium gives rise
to large ambiguities in interpretation. It is not currently possible to
determine whether the underlying emission mechanism in the low state is an
advective flow or magnetic reconnection above the disk, but more detailed
modelling of the ionisation instability {\it may} allow us to distinguish
between these scenarios.


title:
Dynamical family properties and dark halo scaling relations of giant
  elliptical galaxies

abstract:
  Based on a uniform dynamical analysis of line-profile shapes for 21 luminous
round elliptical galaxies, we have investigated the dynamical family relations
of ellipticals: (i) The circular velocity curves (CVCs) of elliptical galaxies
are flat to within ~10% for R>~0.2R_e. (ii) Most ellipticals are moderately
radially anisotropic; their dynamical structure is surprisingly uniform. (iii)
Elliptical galaxies follow a Tully-Fisher (TF) relation, with v_c^max=300 km/s
for an L_B^* galaxy. At given v_c^max, they are ~1 mag fainter in B and appear
to have slightly lower baryonic mass than spirals even for maximum M/L_B. (iv)
The luminosity dependence of M/L_B is confirmed. The tilt of the Fundamental
Plane is not caused by dynamical non-homology, nor only by an increasing dark
matter fraction with L. It is, however, consistent with stellar population
models based on published metallicities and ages. The main driver is therefore
probably metallicity, and a secondary population effect is needed to explain
the K-band tilt. (v) These results make it likely that elliptical galaxies have
nearly maximal M/L_B (minimal halos). (vi) Despite the uniformly flat CVCs,
there is a spread in cumulative M/L_B(r). Some galaxies have no indication for
dark matter within 2R_e, whereas others have local M/L_Bs of 20-30 at 2R_e.
(vii) In models with maximum stellar mass, the dark matter contributes ~10-40%
of the mass within R_e. (viii) The corresponding halo core densities and
phase-space densities are at least ~25 times larger and the halo core radii ~4
times smaller than in spiral galaxies of the same v_c^max. The increase in M/L
sets in at ~10 times larger acceleration than in spirals. This could imply that
elliptical galaxy halos collapsed at high redshift or that some of the dark
matter in ellipticals might be baryonic. (abridged)


title: Big Bang nucleosynthesis and the baryonic content of the universe

abstract:
  A review of the latest measurements of the primordial abundances of the light
nuclei D, 3He, 4He and 7Li is given. We discuss in particular the primordial
abundance Yp of 4He as measured in blue compact dwarf galaxies. We argue that
the best measurements now give a ``high'' value of Yp along with a ``low''
value of D/H, and that the two independent measurements are consistent within
the framework of standard Big Bang nucleosynthesis with a number of light
neutrino species Nnu = 3.0+/-0.3 (2sigma).


title:
BeppoSAX study of the broad-band properties of luminous globular cluster
  X-ray sources

abstract:
  We have performed a detailed study of the broadband spectra of the luminous
globular cluster X-ray sources using BeppoSAX. With the exception of X2127+119,
located in NGC7078, all the other spectra are well represented by a two
component model consisting of a disk-blackbody and Comptonized emission. The
measured low-energy absorptions are in good agreement with those predicted from
optical measurements of the host globular clusters. This implies that there is
little intrinsic X-ray absorption within the binaries themselves, and that the
above spectral model provides a good representation of the low-energy continua.
The sources can be divided into two groups. In the first group, composed of 3
ultra-compact (orbital period <1hr) sources, the disk-blackbody temperatures
and inner-radii appear physically realistic and the Comptonization seed photons
temperatures and radii of the emission areas are consistent with the disk
temperatures and inner radii. For all the other sources, the disk-blackbody
parameters appear not to be physically realistic and the Comptonization
parameters are unrelated to those of the disk-blackbody emission. If this is a
spectral signature of ultra-compact binaries, this implies that no other
ultra-compact binaries are present among those studied here. It is unclear why
this difference between the two types of binaries should exist.


title: Suggestions for Identifying the Primary of Post-GZK Air Showers

abstract:
  A procedure is suggested for systematically narrowing the choice of possible
primaries for (UHECR) air showers with energies beyond the
Greisen-Zatsepin-Kuz'min cut-off of $4 \times 10^{19} eV$.


title: Nonthermal X-ray emission from young Supernova Remnants

abstract:
  The cosmic-ray spectrum up to the knee ($E\sim 10^{15}$ eV) is attributed to
acceleration processes taking place at the blastwaves which bound supernova
remnants. Theoretical predictions give a similar estimate for the maximum
energy which can be reached at supernova remnant shocks by particle
acceleration. Electrons with energies of the order $\sim 10^{15}$ eV should
give a nonthermal X-ray component in young supernova remnants. Recent
observations of SN1006 and G347.3-0.5 confirm this prediction. We present a
method which uses hydrodynamical simulations to describe the evolution of a
young remnant. These results are combined with an algorithm which
simultaneously calculates the associated particle acceleration. We use the test
particle approximation, which means that the back-reaction on the dynamics of
the remnant by the energetic particles is neglected. We present synchrotron
maps in the X-ray domain, and present spectra of the energies of the electrons
in the supernova remnant. Some of our results can be compared directly with
earlier semi-analytical work on this subject by Reynolds [1].


title:
The consequences of ram pressure stripping on the Virgo cluster spiral
  galaxy NGC 4522

abstract:
  New H-alpha Fabry-Perot interferometer observations of the Virgo cluster
spiral galaxy NGC 4522 are presented. A velocity field up to a radius of 60''
was obtained. The observed rotation curve is symmetric. It is not perturbed in
the inner disk. For radii >50'' it shows a solid body rotation. We compare
these data with a numerical model which includes the effects of ram pressure
stripping. The model can reproduce the main characteristics of the H-alpha
emission distribution and velocity field. We therefore conclude that the
stripping event which caused the HI deficiency and the distorted H-alpha
distribution and velocity field has been due to ram pressure. The closest
passage of the galaxy to the cluster center is estimated to be approx. 6.5 10^8
yr ago. The observed recent star formation is due to the re-accretion of gas
clouds which were accelerated to velocities below the escape velocity during
the stripping event. Furthermore, the gas which is located at radii >60'' is
part of an asymmetric expanding ring of gas clouds. A substantial part of these
clouds is located above the disk plane. We predict the HI gas distribution and
velocity field as it would be observed by deep 21 cm observations.


title: Chandra Observations of M31

abstract:
  As part of the Chandra GTO program we are monitoring and surveying M31 using
the HRC and ACIS cameras. These observations have resolved the nuclear X-ray
source into five separate sources, one of which is very soft and may (or may
not!) be associated with the central super-massive black hole. In addition, the
superb spatial resolution and low scattering of the Chandra telescope allows us
to unambiguously resolve the diffuse emission from the point sources. This
emission is clearly softer than the point sources, and also increases with
temperature radially. The monitoring nature of the observations allows detailed
study of the variability of the point sources.


title:
Signatures of Galaxy-Cluster Interactions: Spiral Galaxy Rotation Curve
  Asymmetry, Shape, and Extent

abstract:
  The environmental dependencies of the characteristics of spiral galaxy
rotation curves are studied in this work. We use our large, homogeneously
collected sample of 510 cluster spiral galaxy rotation curves to test the claim
that the shape of a galaxy's rotation curve strongly depends on its location
within the cluster, and thus presumably on the strength of the local
intracluster medium and on the frequency and strength of tidal interactions
with the cluster and cluster galaxies. Our data do not corroborate such a
scenario, consistent with the fact that Tully-Fisher residuals are independent
of galaxy location within the cluster; while the average late-type spiral
galaxy shows more rise in the outer parts of its rotation curve than does the
typical early-type spiral galaxy, there is no apparent trend for either subset
with cluster environment. We also investigate as a function of cluster
environment rotation curve asymmetry and the radial distribution of H II region
tracers within galactic disks. Mild trends with projected cluster-centric
distance are observed: (i) the (normalized) radial extent of optical line
emission averaged over all spiral galaxy types shows a 4%+/-2% increase per Mpc
of galaxy-cluster core separation, and (ii) rotation curve asymmetry falls by a
factor of two between the inner and outer cluster for early-type spirals (a
negligible decrease is found for late-type spirals). Such trends are consistent
with spiral disk perturbations or even the stripping of the diffuse, outermost
gaseous regions within the disks as galaxies pass through the dense cluster
cores.


title: Young star clusters in the Large Magellanic Cloud: NGC 1805 and NGC 1818

abstract:
  We present colour-magnitude diagrams for two rich (~10^4 Msun) Large
Magellanic Cloud star clusters with ages ~10^7 years, constructed from optical
and near-infrared data obtained with the Hubble Space Telescope. These data are
part of an HST project to study LMC clusters with a range of ages. In this
paper we investigate the massive star content of the young clusters, and
determine the cluster ages and metallicities, paying particular attention to Be
star and blue straggler populations and evidence of age spreads. We compare our
data to detailed stellar population simulations to investigate the turn-off
structure of ~25 Myr stellar systems, highlighting the complexity of the blue
straggler phenomenon.


title: Gravitational lensing in eclipsing binary stars

abstract:
  I consider the effect of the gravitational deflection of light upon the light
curves of eclipsing binary stars, focussing mainly upon systems containing at
least one white dwarf component. In absolute terms the effects are small,
however they are strongest at the time of secondary eclipse when the white
dwarf transits its companion, and act to reduce the depth of this feature. If
not accounted for, this may lead to under-estimation of the radius of the white
dwarf compared to that of its companion. I show that the effect is significant
for plausible binary parameters, and that it leads to ~25% reduction in the
transit depth in the system KPD 1930+2752. The reduction of eclipse depth is
degenerate with the stellar radius ratio, and therefore cannot be used to
establish the existence of lensing. A second order effect of the light bending
is to steepen the ingress and egress features of the secondary eclipse relative
to the primary eclipse, although it will be difficult to see this in practice.
I consider also binaries containing neutron stars and black-holes. I conclude
that, although relatively large effects are possible in such systems, a
combination of rarity, faintness and intrinsic variability make it unlikely
that lensing will be detectable in them.


title: Dynamical Relaxation and Massive Extrasolar Planets

abstract:
  Following the suggestion of Black (1997) that some massive extrasolar planets
may be associated with the tail of the distribution of stellar companions, we
investigate a scenario in which 5 < N < 100 planetary mass objects are assumed
to form rapidly through a fragmentation process occuring in a disc or
protostellar envelope on a scale of 100 au.
  These are assumed to have formed rapidly enough through gravitational
instability or fragmentation that their orbits can undergo dynamical relaxation
on a timescale of about 100 orbits.
  Under a wide range of initial conditions and assumptions the relaxation
process ends with either (i) one potential 'hot Jupiter' plus up to two
'external' companions, i.e. planets orbiting near the outer edge of the initial
distribution; (ii) one or two 'external' planets or even none at all; (iii) one
planet on an orbit with a semi--major axis 10 to a 100 times smaller than the
outer boundary radius of the inital distribution together with an 'external'
companion. Most of the other objects are ejected and could contribute to a
population of free floating planets. Apart from the potential 'hot Jupiters',
all the bound objects are on highly eccentric orbits. We found that, apart from
the close orbiters, the probability of ending up with a planet orbiting at a
given distance from the central star increases with the distance. This is
because of the tendency of the relaxation process to lead to collisions with
the central star.
  We discuss the application of these results to some of the more massive
extrasolar planets.


title: Properties of the Chandra Sources in M81

abstract:
  The Chandra X-ray Observatory obtained a 50-ks observation of the central
region of M81 using the ACIS-S in imaging mode. The global properties of the 97
x-ray sources detected in the inner 8.3x8.3 arcmin field of M81 are examined.
Roughly half the sources are concentrated within the central bulge. The
remainder are distributed throughout the disk with the brightest disk sources
lying preferentially along spiral arms. The average hardness ratios of both
bulge and disk sources are consistent with power law spectra of index Gamma~1.6
indicative of a population of x-ray binaries. A group of much softer sources
are also present. The background source-subtracted logN-logS distribution of
the disk follows a power law of index ~ -0.5 with no change in slope over three
decades in flux. The logN-logS distribution of the bulge follows a similar
shape but with a steeper slope above ~4.0e+37 ergs/s. There is unresolved x-ray
flux from the bulge with a radial profile similar to that of the bulge sources.
This unresolved flux is softer than the average of the bulge sources and
extrapolating the bulge logN-logS distribution towards weaker sources can only
account for 20% of the unresolved flux. No strong time variability was observed
for any source with the exception of one bright, soft source.


title: A potential WIMP signature for the caustic ring halo model

abstract:
  Weakly Interacting Massive Particle (WIMP) direct detection event rate
calculations usually rely on fairly simple, essentially static, analytic halo
models. This is largely since the resolution of numerical simulations is not
yet large enough to allow the full numerical calculation of the WIMP density
and velocity distribution. In this paper we study the direct detection rate, in
particular its energy dependence and annual modulation, for the caustic ring
halo model. In this model, which uses simple assumptions to model the infall of
dark matter onto the halo, the distribution of the cold dark matter particles
at the Earth's location has a series of peaks in velocity space. We find that
the sign of the annual modulation in the event rate changes as a function of
recoil energy. These effects provide a potentially distinctive experimental
signal.


title: Spin and magnetism in old neutron stars

abstract:
  The thermal, spin and magnetic evolution of neutron stars in the old low mass
binaries is first explored. Recycled to very short periods via accretion
torques, the neutron stars lose their magnetism progressively. If accretion
proceeds undisturbed for 100 Myrs these stars can rotate close to break up with
periods far below the minimum observed of 1.558 ms. We investigate their
histories using population synthesis models to show that a tail should exist in
the period distribution below 1.558 ms. The search of these ultrafastly
spinning neutron stars as pulsars can help discriminating among the various
equations of state for nuclear matter, and can shed light into the physics of
binary evolution.
  The evolution of isolated neutron stars in the Galaxy is explored beyond the
pulsar phase. Moving through the tenuous interstellar medium, these old
solitary neutron stars lose their rotational energy. Whether also their
magnetism fades is still a mystery. A population synthesis model has revealed
that only a tiny fraction of them is able to accrete from the interstellar
medium, shining in the X-rays. There is the hope that these solitary stars will
eventually appear as faint sources in the Chandra sky survey. This might give
insight on the long term evolution of the magnetic field in isolated objects.


title:
Performance of the Light Trigger System in the Liquid Xenon Gamma-Ray
  Telescope LXeGRIT

abstract:
  LXeGRIT is a balloon-borne Compton telescope for MeV gamma-ray astrophysics,
based on a liquid xenon time projection chamber with charge and light readout.
The energy and direction of an incident gamma-ray is reconstructed from the
three-dimensional locations and energy deposits of individual interactions
taking place in the homogeneous detector volume. While the charge signals
provide energy information and X-Y positions, the fast xenon scintillation
light signal is used to trigger the detector. The drift time measurement,
referred to the time of the trigger signal, gives the Z-position with the known
drift velocity. The light is detected by four UV-sensitive photomultiplier
tubes (PMTs). The logical OR of the PMT signals triggers the data acquisition
system with an efficiency which depends on the event energy and location, as
well as on the discriminator thresholds used on the individual PMTs. Results
from experiments with a tagged 22Na source give the spatial distribution of the
light trigger efficiency for 511 keV gamma-rays. When averaged over the whole
sensitive volume amd all PMTs, the trigger efficiency is 47% or 40% for two
discriminator windows used during the LXeGRIT balloon flight of 1999. These
values are strongly affected by the different sensitivity of each PMT. The
corresponding average efficiency at 511 keV for the best of the four PMTs is in
fact 63%, and approaches 100% for interactions taking place in a small volume
right above the PMT.


title:
Winds from massive stars: implications for the afterglows of gamma-ray
  bursts

abstract:
  Recent observations suggest that long-duration gamma-ray bursts (GRBs) and
their afterglows are produced by highly relativistic jets emitted in
core-collapse explosions. The pre-explosive ambient medium provides a natural
test for the most likely progenitors of GRBs. Those stars that shed their
envelopes most readily have short jet crossing times and are more likely to
produce a GRB. We construct a simple computational scheme to explore the
expected contribution of the presupernova ejecta of single Wolf-Rayet (WR)
stars to the circumstellar environment. Using detailed stellar tracks for the
evolution of massive stars, we discuss the effects that the initial main
sequence mass, metallicity, rotation and membership in a binary system have on
the ambient medium. We extend the theory of GRB afterglows in winds to consider
the effect of the relativistic fireball propagating through the WR ejecta. We
make specific predictions for the interaction of the relativistic blast wave
with the density bumps that arise when the progenitor star rapidly loses a
large fraction of its initial mass or when the ejected wind interacts with the
external medium and decelerates. A re-brightening of the afterglow with a
spectrum redder than the typical synchrotron spectrum (as seen in GRB 970508,
GRB 980326 and GRB 000911) is predicted. We also calculate the luminosity of
the reflected echo that arises when circumstellar material Compton-scatters the
prompt radiation and examine the spectral signatures expected from the
interaction of the GRB afterglow with the ejected medium.


title: MERLIN imaging of the maser flare in Markarian 348

abstract:
  MERLIN images of Mrk 348 at 22 GHz show water maser emission at 0.02 - 0.11
Jy, within approximately 0.8 pc of the nucleus. This is the first direct
confirmation that molecular material exists close to the Seyfert 2 nucleus. Mrk
348 was observed in 2000 May one month after Falcke et al. (2000) first
identified the maser in single-dish spectra. The peak maser flux density has
increased about threefold. The masing region is < 0.6 pc in radius. The flux
density of radio continuum emission from the core has been rising for about 2
years. The maser-core separation is barely resolved but at the 3 sigma
significance level they are not coincident along the line of sight. The masers
lie in the direction of the northern radio lobes and probably emanate from
material shocked by a jet with velocity close to c. The correlation between the
radio continuum increase and maser flare is explained as arising from high
level nuclear activity through a common excitation mechanism although direct
maser amplification of the core by masers tracing a Keplerian disc is not
completely ruled out.


title:
Preliminary Results from the 1999 Balloon Flight of the Liquid Xenon
  Gamma-Ray Imaging Telescope (LXeGRIT)

abstract:
  LXeGRIT is a balloon-borne Compton telescope employing a large volume liquid
xenon time projection chamber (LXeTPC) as the central gamma-ray detector. It is
designed to image gamma rays in the energy range of 200 keV to 20 MeV, with an
angular resolution of about 3 degrees (1 sigma) at 2 MeV, within a
field-of-view (FOV) of about 1 sr. The detector's energy and three-dimensional
spatial resolution as measured during pre-flight calibration experiments, are
$\Delta E_\mathrm{lxe}/E=8.8% : \sqrt{1\MeV /E}$ and < 1mm RMS, respectively.
The detection efficiency for Compton events varies between 1.5% and 4%
depending on energy and event selection. We describe the instrument as flown on
May 7, 1999 and review its overall performance at balloon altitude. The launch
occurred at 13:26:54 UT from Ft. Sumner, New Mexico and the flight was
terminated about 9 hours later. The Crab was in the instrument FOV for a few
hours. Analysis of these data is in progress.


title:
An Estimate of the Age Distribution of Terrestrial Planets in the
  Universe: Quantifying Metallicity as a Selection Effect

abstract:
  Planets like the Earth cannot form unless elements heavier than helium are
available. These heavy elements, or `metals', were not produced in the big
bang. They result from fusion inside stars and have been gradually building up
over the lifetime of the Universe. Recent observations indicate that the
presence of giant extrasolar planets at small distances from their host stars,
is strongly correlated with high metallicity of the host stars. The presence of
these close-orbiting giants is incompatible with the existence of earth-like
planets. Thus, there may be a Goldilocks selection effect: with too little
metallicity, earths are unable to form for lack of material, with too much
metallicity giant planets destroy earths. Here I quantify these effects and
obtain the probability, as a function of metallicity, for a stellar system to
harbour an earth-like planet. I combine this probability with current estimates
of the star formation rate and of the gradual build up of metals in the
Universe to obtain an estimate of the age distribution of earth-like planets in
the Universe. The analysis done here indicates that three quarters of the
earth-like planets in the Universe are older than the Earth and that their
average age is 1.8 +/- 0.9 billion years older than the Earth. If life forms
readily on earth-like planets - as suggested by the rapid appearance of life on
Earth - this analysis gives us an age distribution for life on such planets and
a rare clue about how we compare to other life which may inhabit the Universe.


title:
The Quiescent X-Ray Spectrum of the Neutron Star in Cen X-4 Observed
  with Chandra/ACIS-S

abstract:
  We report on spectral and intensity variability analysis from a
Chandra/ACIS-S observation of the transient, type-I X-ray bursting low-mass
X-ray binary Cen X-4. The quiescent X-ray spectrum during this observation is
statistically identical to one observed previously with Beppo/SAX, and close,
but not identical, to one observed previously with ASCA. The X-ray spectrum is
best described as a pure Hydrogen atmosphere thermal spectrum plus a power-law
component that dominates the spectrum above 2 keV. The best-fit radius of the
neutron star is r=12.9+/-2.6 (d/1.2 kpc) km if the interstellar absorption is
fixed at the value implied by the optical reddening. Allowing the interstellar
absorption to be a free parameter yields r=19+45-10 (d/1.2 kpc) km (90%
confidence). The thermal spectrum from the neutron star surface is inconsistent
with a solar metallicity. We find a 3sigma upper-limit of root-mean-square
variability <18% (0.2-2.0 keV; 0.0001-1 Hz) during the observation. On the
other hand, the 0.5-10.0 keV luminosity decreased by 40+/-8% in the 4.9 years
between the Asca and Chandra observations. This variability can be attributed
to the power-law component. Moreover, we limit the variation in thermal
temperature to <10% over these 4.9 years. The stability of the thermal
temperature and emission area radius supports the interpretation that the
quiescent thermal emission is due to the hot neutron star core.


title: Search for a TeV gamma-ray halo of Mkn 501

abstract:
  For distant extragalactic sources of gamma-rays in the PeV energy range,
interactions of the gamma rays with intergalactic diffuse radiation fields will
initiate a pair cascade. Depending on the magnetic fields in the vicinity of
the source, the cascade can either result in an isotropic halo around an
initially beamed source, or remain more or less collimated. Data recorded by
the HEGRA system of imaging atmospheric Cherenkov telescopes are used to derive
limits on the halo flux from the AGN Mrk 501. This is achieved by comparing the
angular distribution of TeV gamma-rays during the 1997 burst phase -- where
direct photons should dominate -- with the distribution during the 1998/99
quiescent state, where a steady-state halo contribution should be most
pronounced. The results depend on the assumptions concerning the angular
distribution of the halo; limits on the halo flux within 0.5 to 1 degr. from
the source range between 0.1% and 1% of the peak burst flux.


title: Galactic and extragalactic magnetic fields

abstract:
  The current state of research of the Galactic magnetic field is reviewed
critically. The average (equipartition) strength of the total field derived
from radio synchrotron data is 6 +/- 2 muG locally and about 10 +/- 3 muG at 3
kpc Galactic radius. These values agree well with the estimates using the
locally measured cosmic-ray energy spectrum and the radial variation of protons
derived from gamma-rays. Optical and synchrotron polarization data yield a
strength of the local regular field of 4 +/- 1 muG, but this value is an upper
limit if the field strength fluctuates within the beam or if anisotropic fields
are present. Pulsar rotation measures, on the other hand, give only 1.4 +/- 0.2
muG, a lower limit if fluctuations in regular field strength and thermal
electron density are anticorrelated along the pathlength. The local regular
field may be part of a 'magnetic arm' between the optical arms. However, the
global structure of the regular Galactic field is not yet known. Several
large-scale field reversals in the Galaxy were detected from rotation measure
data, but a similar phenomenon was not observed in external galaxies. The
Galactic field may be young in terms of dynamo action so that reversals from
the chaotic seed field are preserved, or a mixture of dynamo modes causes the
reversals, or the reversals are signatures of large-scale anisotropic field
loops. The Galaxy is surrounded by a thick disk of radio continuum emission of
similar extent as in edge-on spiral galaxies. While the local field in the thin
disk is of even symmetry with respect to the plane (quadrupole), the global
thick-disk field may be of dipole type. The Galactic center region hosts highly
regular fields of up to milligauss strength which are oriented perpendicular to
the plane.


title:
Stellar features in integrated starburst spectra as stellar population
  diagnostics

abstract:
  We review the main stellar features observed in starburst spectra from the UV
to the near-IR and their use as fundamental tools to determine the properties
of stellar populations from integrated spectra.
  The origin and dependence of the features on stellar properties are
discussed, and we summarise existing modeling techniques used for quantitative
analysis.
  Recent results from studies based on UV, optical and near-IR observations of
starbursts and active galaxies are summarised. Finally, we briefly discuss
combined starburst + photoionisation models including also observations from
nebular emission lines. The present review is complementary to the recent
summary by Schaerer (2000) (http://xxx.lpthe.jussieu.fr/abs/astro-ph/0007307)
discussing more extensively nebular analysis of starbursts and related objects.


title:
Signatures in a Giant Radio Galaxy of a Cosmological Shock Wave at
  Intersecting Filaments of Galaxies

abstract:
  Sensitive images of low-level, Mpc-sized radio cocoons offer new
opportunities to probe large scale intergalactic gas flows outside clusters of
galaxies. New radio images of high surface brightness sensitivity at
strategically chosen wavelengths of the giant radio galaxy NGC 315 (Mack et al.
1997,1998) reveal significant asymmetries and particularities in the
morphology, radio spectrum and polarization of the ejected radio plasma. We
argue that the combination of these signatures provides a sensitive probe of an
environmental shock wave. Analysis of optical redshifts in NGC 315 vicinity
confirms its location to be near, or at a site of large-scale flow collisions
in the 100 Mpc sized Pisces-Perseus Supercluster region. NGC 315 resides at the
intersection of several galaxy filaments, and its radio plasma serves there as
a `weather station' (Burns 1998) probing the flow of the elusive and previously
invisible IGM gas. If our interpretation is correct, this is the first
indication for a shock wave in flows caused by the cosmological large scale
structure formation, which is located in a filament of galaxies. The
possibility that the putative shock wave is a source of gamma-rays and ultra
high energy cosmic rays is briefly discussed.


title: Molecular Carbon Chains and Rings in TMC-1

abstract:
  We present mapping results in several rotational transitions of HC3N, C6H,
both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the
filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The
spatial distribution of the cumulene carbon chain propadienylidene H2C3
(hereafter l-C3H2) is found to deviate significantly from the distributions of
the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The
cyclic over linear abundance ratio of C3H2 increases by a factor of 3 across
the filament, with a value of 28 at the cyanopolyyne peak. This abundance ratio
is an order of magnitude larger than the range (3 to 5) we observed in the
diffuse interstellar medium. The cyclic over linear abundance ratio of C3H also
varies by ~2.5 in TMC-1, reaching a maximum value (13) close to the
cyanopolyyne peak. These behaviors might be related to competitive processes
between ion-neutral and neutral-neutral reactions for cyclic and linear
species.


title: Supermassive Black Holes from the SUNNS survey

abstract:
  We report three new accurate mass measurements for the supermassive black
holes hosted by the early-type disk galaxies NGC2787, NGC4459 and NGC4596. The
targets were selected from a larger set of long-slit spectra obtained with the
Hubble Space Telescope as part of the Survey of Nearby Nuclei with STIS
(SUNNS). They display symmetric gas velocity curves that could be modeled as a
rotating disk in the joint potential of the stellar bulge and a putative
central black hole. They also show regular dust lane patterns that could be
used to infer the nuclear disk orientation. These three galaxies fall in the
black-hole mass vs. central stellar velocity dispersion plane in agreement with
the recently reported relation between these two quantities.


title:
Compression and Classification Methods for Galaxy Spectra in Large
  Redshift Surveys

abstract:
  Methods for compression and classification of galaxy spectra, which are
useful for large galaxy redshift surveys (such as the SDSS, 2dF, 6dF and
VIRMOS), are reviewed. In particular, we describe and contrast three methods:
(i) Principal Component Analysis, (ii) Information Bottleneck, and (iii) Fisher
Matrix. We show applications to 2dF galaxy spectra and to mock semi-analytic
spectra, and we discuss how these methods can be used to study physical
processes of galaxy formation, clustering and galaxy biasing in the new large
redshift surveys.


title: Continuum Variability of Active Galactic Nuclei in the Optical-UV Range

abstract:
  The variability of the continuum spectral energy distribution has been
analyzed for a complete magnitude-limited sample of quasars in Selected Area
57, observed at two epochs in the photographic $U$, $B_J$, $F$ and $N$ bands
with the Mayall 4m telescope at Kitt Peak. Changes $\delta \alpha$ of the
spectral slope $\alpha$ appear correlated with brightness variations $\delta
log f_{\nu}$ indicating an average hardening of the spectrum in the bright
phases. This confirms that the correlation of variability with redshift, found
in a single observing band, is due to intrinsic spectral changes. The average
observed $\delta \alpha - \delta log f_{\nu}$ relation is consistent with the
spectral change due to temperature variation of a black body of about $2.5
\cdot 10^4 K$.


title:
Post-Starburst Populations Near and Far - The Potential of Near-IR
  Spectroscopy

abstract:
  The efficient use of near-IR data in studies of external stellar populations
depends on our ability to recognize the nature of the predominant sources of
light, and to interprete these findings in terms of age and metallicity. Here
we focus on elderly post-starburst populations, with ages of 0.1-1 Gyr. New
models confirm that they are indeed expected to display specific spectral
signatures in the near-IR, due to variable M stars of the asymptotic giant
branch and to carbon stars. The signatures depend on age and metallicity. We
summarize the status of current quantitative predictions and emphasize the
importance of an empirical calibration of the spectral synthesis models.


title:
An attempt to identify the extended synchrotron structure associated
  with the micro-quasar GRS 1915+105

abstract:
  The energy ejected from the galaxy micro-quasar GRS1915+105 in the form of
jets is expected to lead to formation of an extended double lobe/hot-spot
structure with the energy content comparable to an average supernova remnant.
We used the Effelsberg 100m telescope at 10.45 GHz in attempt to identify such
structures. For this distant galactic plane source any definite identification
was not possible due to high confusion by numerous background sources, however,
a few suspect structures were pointed out.


title: The emission regions in X-ray binaries: dipping as a diagnostic

abstract:
  X-ray dipping in the black hole binary Cygnus X-1, the Galactic jet source
GRO J1655-40 and in low mass X-ray binaries is discussed. It is shown that
spectral analysis strongly constrains emission models. Measurement of dip
ingress/egress times allows the sizes of extended emission regions to be
determined, notably for the Accretion Disk Corona which is responsible for
Comptonization in X-ray binaries. In LMXB, the radius of the ADC is shown to be
between ~ 10^9 and ~ 5x10^10 cm, an appreciable fraction of the accretion disk
radius. This is inconsistent with Comptonization models requiring a localized
Comptonizing region, for example, in the immediate neighbourhood of the neutron
star. Results from a survey of LMXB using ASCA and BeppoSAX reveal an
approximate equality between the height of the blackbody emission region on the
neutron star and the height of the inner radiatively-supported disk, suggesting
either that there is a direct causal link, such as a radial accretion flow
between the inner disk edge and the star, or an indirect link, as in the case
of accretion flow creep on the surface of the neutron star as suggested by
Inogamov & Sunyaev. Finally, the survey shows that the blackbody cannot
originate on the accretion disk as the required inner radii in many sources are
substantially less than the neutron star radius.


title: Can We Date Starbursts?

abstract:
  Age dating starbursts is an exercise with many caveats. We attempt to
summarise a discussion session that was lead along a rather optimistic
guideline: the aim was to highlight that current age estimates, despite
undeniable uncertainties, do provide constraints on the physics of starbursts.
In many cases, better starburst theories will be needed before the improvement
of empirical timelines becomes crucial.


title:
FUSE Observations of an X-Ray Bright Region in the Vela Supernova
  Remnant

abstract:
  We present the results of a FUSE observation of an X-ray selected knot in the
Vela supernova remnant. Spectra were obtained through the 30"x30" low
resolution aperture and the 4"x20" medium resolution aperture. O VI 1032,1038
and C III 977 are detected strongly in both spectra, and S VI 933,944 is
detected weakly only in the larger aperture spectrum. We also report the first
detection of C II 1037 emission in a supernova remnant. The spectra show the
presence of two kinematic components along the line of sight - one with both
low and high excitation emission centered at a velocity of -50 km/s and another
with only low excitation emission centered at a velocity of +100 km/s. We
associate the -50 km/s component with the observed X-ray knot, and find a
dynamical pressure of 3.7x10^{-10} dyne cm^{-2} driving the shock. We compare
our results with data obtained using the Hopkins Ultraviolet Telescope at
nearby locations and find that differences in the spectra imply the existence
of two emitting components in the X-ray knot. Based on the X-ray morphology
seen in a ROSAT HRI image, we identify two distinct regions which can be
associated with these two components whose ultraviolet emission differs
dramatically. These observations demonstrate the importance of high spectral
resolution in understanding the proper physical relationships between the
various emitting components in supernova remnants.


title: PSR J1740-3052 - a pulsar with a massive companion

abstract:
  We report on the discovery of a binary pulsar, PSR J1740-3052, during the
Parkes multibeam survey. Timing observations of the 570-ms pulsar at Jodrell
Bank and Parkes show that it is young, with a characteristic age of 350 kyr,
and is in a 231-day, highly eccentric orbit with a companion whose mass exceeds
11 M_sun. An accurate position for the pulsar was obtained using the Australia
Telescope Compact Array. Near-infrared 2.2-um observations make with the
telescopes at the Siding Spring observatory reveal a late-type star coincident
with the pulsar position. However, we do not believe that this star is the
pulsar's companion, because a typical star of this spectral type and required
mass would extend beyond the pulsar's orbit. Furthermore, the measured advance
of periastron of the pulsar suggests a more compact companion, for example, a
main-sequence star with radius only a few times that of the sun. Such a
companion is also more consistent with the small dispersion measure variations
seen near periastron. Although we cannot conclusively rule out a black-hole
companion, we believe the companion is probably an early B star, making the
system similar to the binary PSR J0045-7319.


title: Substructure and dynamics of the Fornax Cluster

abstract:
  We present the first dynamical analysis of a galaxy cluster to include a
large fraction of dwarf galaxies. Our sample of 108 Fornax Cluster members
measured with the UK Schmidt Telescope FLAIR-II spectrograph contains 55 dwarf
galaxies (15.5>bj>18.0 or -16>Mb>-13.5). Halpha emission shows that 36+/-8 per
cent of the dwarfs are star-forming, twice the fraction implied by
morphological classifications. The total sample has a mean velocity of
1493+/-36 km/s and a velocity dispersion of 374+/-26 km/s. The dwarf galaxies
form a distinct population: their velocity dispersion (429+/-41 km/s) is larger
than that of the giants (308+/-30 km/s) at the 98 per cent confidence level.
This suggests that the dwarf population is dominated by infalling objects
whereas the giants are virialized.
  The Fornax system has two components; the main Fornax Cluster centered on NGC
1399 with mean velocity 1478 km/s and velocity dispersion 370 km/s, and a
subcluster centered 3 degrees to the south-west including NGC 1316 with mean
velocity 1583 km/s and velocity dispersion 377 km/s. This partition is
preferred over a single cluster at the 99 per cent confidence level. The
subcluster, a site of intense star formation, is bound to Fornax and probably
infalling towards the cluster core for the first time. We discuss the
implications of this substructure for distance estimates of the Fornax Cluster.


title:
Advanced methods for cosmic microwave background data analysis: the big
  N^3 and how to beat it

abstract:
  In this talk I propose the first fast methods which can analyze CMB data
taking into account correlated noise, arbitrary beam shapes, non-uniform
distribution of integration time on the sky, and partial sky coverage, without
the need for approximations. These ring torus methods work by performing the
analysis in the time ordered domain (TOD) rather than on the sky map of
fluctuations. They take advantage of the simplicity of noise correlations in
the TOD as well as certain properties of the group of rotations SO(3). These
properties single out a family of scanning strategies as favorable, namely
those which scan on rings and have the geometry of an n-torus. This family
includes the strategies due to TOPHAT, MAP and Planck. I first develop the
tools to model the time ordered signal, using Fast Fourier Transform methods
for convolution of two arbitrary functions on the sphere (Wandelt and G\'orski
2000). Then I apply these ideas to show that in the case of a 2-torus one can
reduce the time taken for CMB power spectrum analysis from an unfeasible order
N^3 to order N^2, where N ~ 10^5-10^8 is the number of resolution elements
(Wandelt and Hansen, in preparation).


title: Evidence for solar-like oscillations in beta Hydri

abstract:
  We have made a clear detection of excess power, providing strong evidence for
solar-like oscillations in the G2 subgiant beta Hyi. We observed this star over
five nights with the UCLES echelle spectrograph on the 3.9-m Anglo-Australian
Telescope, using an iodine absorption cell as a velocity reference. The time
series of 1196 velocity measurements shows an rms scatter of 3.30 m/s, and the
mean noise level in the amplitude spectrum at frequencies above 0.5 mHz is 0.11
m/s. We see a clear excess of power centred at 1.0 mHz, with peak amplitudes of
about 0.5 m/s, in agreement with expectations for this star. Fitting the
asymptotic relation to the power spectrum indicates the most likely value for
the large separation is 56.2 microHz, also in good agreement with the known
properties of beta Hyi.


title:
From the time-ordered data to the Maximum-Likelihood temperature maps of
  the Cosmic Microwave Backgorund anisotropy

abstract:
  We review selected methods of the Cosmic Microwave Background data analysis
appropriate for the analysis of the largest currently available data sets. We
focus on techniques of the time-ordered data manipulation and map making
algorithms based on the maximum-likelihood approach. The presented methods have
been applied to the MAXIMA data analysis (Hanany et al 2000) and the
description of the algorithms is illustrated with the examples drawn from that
experience. The more extensive presentation of the here-mentioned issues will
be given in the forthcoming paper (Stompor et al 2001).


title:
Possible evidence for a variable fine structure constant from QSO
  absorption lines: motivations, analysis and results

abstract:
  An experimental search for variation in the fundamental coupling constants is
strongly motivated by modern high-energy physics theories. Comparison of quasar
absorption line spectra with laboratory spectra provides a sensitive probe for
variability of the fine structure constant, alpha, over cosmological
time-scales. We have previously developed and applied a new method providing an
order of magnitude gain in precision over previous optical astrophysical
constraints. Here we extend that work by including new quasar spectra of damped
Lyman-alpha absorption systems. We also re-analyse our previous lower redshift
data and confirm our initial results. The constraints on alpha come from
simultaneous fitting of absorption lines of subsets of the following species:
Mg I, Mg II, Al II, Al III, Si II, Cr II, Fe II, Ni II and Zn II. We present a
detailed description of our methods and results based on an analysis of 49
quasar absorption systems (towards 28 QSOs) covering the redshift range 0.5 < z
< 3.5. There is statistical evidence for a smaller alpha at earlier epochs:
da/a = (-0.72 +/- 0.18) * 10^{-5}. The new and original samples are independent
but separately yield consistent and significant non-zero values of da/a. We
summarise the results of a thorough investigation of systematic effects
published in a companion paper. The value we quote above is the raw value, not
corrected for any of these systematic effects. The only significant systematic
effects so far identified, if removed from our data, would lead to a more
significant deviation of da/a from zero.

categories: astro-ph gr-qc hep-th nucl-th physics.atom-ph


title:
Possible evidence for a variable fine structure constant from QSO
  absorption lines: systematic errors

abstract:
  Comparison of quasar absorption spectra with laboratory spectra allow us to
probe possible variations in the fundamental constants over cosmological
time-scales. In a companion paper we present an analysis of Keck/HIRES spectra
and report possible evidence suggesting that the fine structure constant,
alpha, may have been smaller in the past: da/a = (-0.72 +/- 0.18) * 10^{-5}
over the redshift range 0.5 < z < 3.5. In this paper we describe a
comprehensive investigation into possible systematic effects. Most of these do
not significantly influence our results. When we correct for those which do
produce a significant systematic effect in the data, the deviation of da/a from
zero becomes more significant. We are lead increasingly to the interpretation
that alpha was slightly smaller in the past.


title:
Further constraints on variation of the fine structure constant from
  alkali doublet QSO absorption lines

abstract:
  Comparison of quasar absorption line spectra with laboratory spectra provides
a precise probe for variability of the fine structure constant, alpha, over
cosmological time-scales. We constrain variation in alpha in 21 Keck/HIRES Si
IV absorption systems using the alkali doublet (AD) method in which changes in
alpha are related to changes in the doublet spacing. The precision obtained
with the AD method has been increased by a factor of 3: da/a = (-0.5 +/- 1.3) *
10^{-5}. We also analyse potential systematic errors in this result. Finally,
we compare the AD method with the many-multiplet method which has achieved an
order of magnitude greater precision and we discuss the future of the AD
method.


title:
Relativistic effects in Ni II and the search for variation of the fine
  structure constant

abstract:
  Theories unifying gravity and other interactions suggest the possibility of
spatial and temporal variation of physical ``constants'' in the Universe.
Detection of high redshift absorption systems intersecting the sight lines
towards distant quasars provide a powerful tool for measuring these variations.
In the present paper we demonstrate that high sensitivity to variation of the
fine structure constant alpha can be obtained by comparing cosmic and
laboratory spectra of the Ni II ion. Relativistic effects in Ni II reveal many
interesting features. The Ni II spectrum exhibits avoided level crossing
phenomenon under variation of alpha and the intervals between the levels have
strong nonlinear dependencies on relativistic corrections. The values of the
transition frequency shifts, due to the change of alpha, vary significantly
from state to state including change of the sign. This enhances the sensitivity
to the variation of alpha and reduces possible systematic errors. The
calculations of alpha-dependence of the nickel ion spectral lines that are
detectable in quasar absorption spectra have been performed using a
relativistic configuration interaction method.


title: Gravitational Lensing - A brief review

abstract:
  Gravitational lensing has established itself as a valuable tool in many
astrophysical fields in the roughly 20 years of its existence as an
observational science. In this brief review, first the basics of lensing are
introduced. Then it is shown that the two propagation effects, gravitational
lensing and interstellar scintillation, have a number of properties in common.
Finally, various lensing phenomena are discussed with emphasis on recent
observations.


title:
Strongly coupled Coulomb and nuclear plasma in inner crusts of neutron
  stars

abstract:
  Matter of subnuclear density in the inner crusts of neutron stars consists of
neutron-rich atomic nuclei immersed in strongly degenerate relativistic gas of
electrons and strongly nonideal liquid of neutrons. We give a brief account of
thermodynamic and kinetic properties of this matter which are greatly affected
by Coulomb and nuclear interactions (a companion paper on the outer envelopes
is astro-ph/0012316) and show how they can be studied from observations of
thermal radiation of young (age < 100 yr) neutron stars (for a discussion of
the latter possibility, see astro-ph/0012306).


title: The Cuspy LINER Nucleus of the S0/a Galaxy NGC 2681

abstract:
  The nucleus of the bulge-dominated, multiply-barred S0/a galaxy NGC 2681 is
studied in detail, using high resolution Hubble Space Telescope FOC and NICMOS
imaging and FOS spectroscopy. The ionised gas central velocity dispersion is
found to increase by a factor ~2 when narrowing the aperture from R~1.5"
(ground) to R~0.1" (FOS). Dynamical modeling of these velocity dispersions
suggests that NGC 2681 does host a supermassive black hole (BH) for which one
can estimate a firm mass upper limit M_BH < 6*10^7 Solar Masses. This upper
limit is consistent with the relation between the central BH mass and velocity
dispersion M_BH - sigma known for other galaxies. The emission line ratios
place the nucleus of NGC 2681 among LINERs. It is likely that the emission line
region comes from a rather mild, but steady, feeding of gas to the central BH
in this galaxy. The inner stellar population lacks any measurable color
gradient (to a radius of 0.6 kpc) from the infrared to the ultraviolet,
consistently with FOC, FOS and IUE data, all indicating that this system
underwent a starburst ~1 Gyr ago that encompassed its whole interior, down to
its very center. The most likely source of such a widely-distributed starburst
is the dumping of tidally-extruded gas from a galaxy neighbor. If so, then NGC
2681 can be considered as the older brother of M82, seen face-on as opposed to
the edge-on view we have for M82.


title:
High velocity structures in, and the X-ray emission from the LBV nebula
  around Eta Carinae

abstract:
  The Luminous Blue Variable star Eta Carinae is one of the most massive stars
known. It underwent a giant eruption in 1843 in which the Homunculus nebula was
created. ROSAT and ASCA data indicate the existence of a hard and a soft X-ray
component which appear to be spatially distinct: a softer diffuse shell of the
nebula around Eta Carinae and a harder point-like source centered on the star
Eta Car. Astonishingly the morphology of the X-ray emission is very different
from the optical appearance of the nebula. We present a comparative analysis of
optical morphology, the kinematics, and the diffuse soft X-ray structure of the
nebula around Eta Carinae. Our kinematic analysis of the nebula shows extremely
high expansion velocities. We find a strong correlation between the X-ray
emission and the knots in the nebula and the largest velocities, i.e. the X-ray
morphology of the nebula around Eta Carinae is determined by the interaction
between material streaming away from Eta Car and the ambient medium.


title: Radial Oscillations of Rotating Strange Stars in Strong Magnetic Fields

abstract:
  In this paper we study radial oscillations of rotating strange stars in
strong magnetic fields in the Density Dependent Quark Mass (DDQM) model. We see
that increase of frequency i.e. difference in frequency of rotating and
non-rotating stars is more for higher magnetic fields. The change is small for
low mass stars but it increases with the mass of the star. This change of
frequency is significant for maximum mass whereas it is marginal for a 1.4
solar mass star.


title: High frequency peakers. I. The bright sample

abstract:
  Here we present a sample of sources with convex radio spectra peaking at
frequencies above a few GHz. We call these radio sources High Frequency Peakers
(HFPs). This sample extends to higher turnover frequencies than the samples of
Compact Steep Spectrum (CSS) and GHz Peaked Spectrum (GPS) radio sources. HFPs
are rare due to the strong bias against them caused by their turnover occurring
at frequencies about one order of magnitude higher than in CSS-GPS samples. The
sample has been selected by a comparison between the Green Bank survey (87GB)
at 4.9 GHz and the NRAO VLA Sky Survey (NVSS) at 1.4 GHz. Then the candidates
have been observed with the VLA at 1.365, 1.665, 4.535, 4.985, 8.085, 8.485,
14.96 and 22.46 GHz in order to derive a simultaneous radio spectrum, and
remove variable sources from the sample. The final list of genuine HFP sources
consists of 55 objects with flux density exceeding 300 mJy at 4.9 GHz at the
time of the 87GB observation. Optical identifications are available for 29 of
them; 24 are high redshift quasars, 3 are galaxies (one of them has indeed
broad lines in the optical spectrum) and 2 are BL Lac objects. The remaining
sources are mostly empty fields (17) on the digitised POSS or have uncertain
classification (9).


title:
The 2dF Galaxy Redshift Survey: Near Infrared Galaxy Luminosity
  Functions

abstract:
  We combine the 2MASS extended source catalogue and the 2dFGRS to produce an
IR selected galaxy catalogue with 17,173 measured redshifts. We use this
extensive dataset to estimate the J and K-band galaxy luminosity functions. The
LFs are fairly well fit by Schechter functions with J: M*-5log h=
-22.36+/-0.02, alpha= -0.93+/-0.04, Phi=0.0104+/-0.0016 h^3/Mpc^3 and K:
M*-5log h= -23.44+/-0.03, alpha=-0.96+/-0.05, Phi=0.0108+/-0.0016 h^3/Mpc^3
(2MASS Kron magnitudes). These parameters assume a cosmological model with
Omega=0.3 and Lambda=0.7. With datasets of this size, systematic rather than
random errors are the dominant source of uncertainty in the determination of
the LF. We carry out a careful investigation of possible systematic effects in
our data. The surface brightness distribution of the sample shows no evidence
that significant numbers of low surface brightness or compact galaxies are
missed by the survey. We estimate the present-day distributions of B-K and J-K
colours as a function of absolute magnitude and use models of the galaxy
stellar populations, constrained by the observed optical and infrared colours,
to infer the galaxy stellar mass function. Integrated over all galaxy masses,
this yields a total mass fraction in stars (in units of the critical mass
density) of Omega_*.h= (1.6+/-0.24)/10^3 for a Kennicutt IMF and Omega_*.h=
(2.9+/-0.43)/10^3 for a Salpeter IMF. These values agree with those inferred
from observational estimates of the star formation history of the universe
provided that dust extinction corrections are modest.


title:
R-mode oscillations of differentially and rapidly rotating Newtonian
  polytropic stars

abstract:
  For the analysis of the r-mode oscillation of hot young neutron stars, it is
necessary to consider the effect of it differential rotation, because viscosity
is not strong enough for differentially rotating young neutron stars to be lead
to uniformly rotating configurations on a very short time scale after their
birth. In this paper, we have developed a numerical scheme to solve r-mode
oscillations of differentially rotating polytropic inviscid stars. This is the
extended version of the method which was applied to compute r-mode oscillations
of uniformly rotating Newtonian polytropic stars. By using this new method, we
have succeeded in obtaining eigenvalues and eigenfunctions of r-mode
oscillations of differentially rotating polytropic stars. Our numerical results
show that as the degree of differential rotation is increased, it becomes more
difficult to solve r-mode oscillations for slightly deformed configurations
from sphere compared to solving r-mode oscillations of considerably deformed
stars. One reason for it seems that for slightly deformed stars corotation
points appear near the surface region if the degree of differential rotation is
strong enough. This is similar to the situation that the perturbational
approach of r-mode oscillations for it slowly rotating stars in general
relativity results in a singular eigenvalue problem.


title: A comment on trans-Planckian physics in inflationary universe

abstract:
  There are several works searching for a clue of trans-Planckian physics on
the primordial density perturbation spectrum. Here we would like to point out
an important aspect which has been overlooked so far. When we consider a model
in which the primordial density perturbation spectrum is modified due to
trans-Planckian physics, the energy density of fluctuations of the inflaton
field necessarily becomes significantly large, and hence its back reaction to
the cosmic expansion rate cannot be neglected.


title: Asymmetry in Isolated, Morphologically Normal Sa Galaxies

abstract:
  We have examined the morphological and dynamical HI symmetry properties of a
sample of moderately inclined Sa galaxies which are classified as
morphologically normal. The sample galaxies were known a prior to exhibit
kinematic peculiarities ranging from warps to independent, wholly decoupled
disks, and are possibly the remnants of minor mergers. We compare the asymmetry
of the rotation curves to global kinematic asymmetry, and find a relationship
between rotation curve asymmetry and the kinematic n=2 mode. We have also
examined the kinematics of these galaxies following the discussion of Briggs
(1990) and find that the warps observed in the HI disks of these galaxies
deviate significantly from the simple rules for warps that commonly apply.


title:
The effect of bias and redshift distortions on a geometric test for the
  cosmological constant

abstract:
  We revisit the feasibility of a cosmological test with the geometric
distortion focusing on an ambiguous factor of the evolution of bias. Starting
from defining estimators for the spatial two-point correlation function and the
power spectrum, in a rigorous manner, we derive useful formulas for the
two-point clustering statistics which take the light-cone effect and the
redshift-space distortions into account. Then we investigate how the predicted
correlation functions are affected by the redshift-space distortions and the
bias assuming quasar samples which roughly match the 2dF survey. Effect of the
bias is crucial, in particular, on anisotropic component of the clustering
statistics in redshift-space. By surveying behavior of the predicted
correlation functions to parameters of a phenomenological model for the
evolution of bias, it is shown that the correlation functions on the light-cone
is sensitive to a mean amplitude of the bias and rather insensitive to the
speed of its redshift-evolution. This feature is useful for an analysis of the
geometric test.


title:
Self-Similar Evolution of Wind-Blown Bubbles with Mass-loading by
  Conductive Evaporation

abstract:
  We present similarity solutions for mass-loaded adiabatic bubbles that are
blown by winds having time dependent mechanical luminosities. We consider
mass-loading through conductive evaporation of clumps. In the limit of little
mass loading a similarity solution found by Dyson (1973) for expansion into a
smooth ambient medium is recovered. We find that the Mach number in the shocked
mass-loaded wind shows a radial dependence that varies qualitatively from
solution to solution. In some cases it is everywhere less than unity in the
frame of the clumps being evaporated, while in others it is everywhere greater
than unity. In some solutions the mass-loaded shocked wind undergoes one or two
sonic transitions in the clump frame. Maximum possible values of the ratio of
evaporated mass to stellar wind mass are found as a consequence of the
evaporation rates dependence on temperature and the lowering of the temperature
by mass-loading. Mass-loading tends to reduce the emissivity in the interior of
the bubble relative to its limb, whilst simultaneously increasing the central
temperature relative to the limb temperature.


title:
Probing the Stellar Surface of HD 209458 from Multicolor Transit
  Observations

abstract:
  Multicolor photometric observations of a planetary transit in the system HD
209458 are analyzed. The observations, made in the Stromgren photometric
system, allowed a recalculation of the basic physical properties of the
star-planet system. This includes derivation of linear limb-darkening values of
HD 209458, which is the first time that a limb-darkening sequence has
observationally been determined for a star other than the Sun. As the derived
physical properties depend on assumptions that are currently known with limited
precision only, scaling relations between derived parameters and assumptions
are given. The observed limb-darkening is in good agreement with theoretical
predictions from evolutionary stellar models combined with ATLAS model
atmospheres, verifying these models for the temperature (Teff ~ 6000K), surface
gravity (log g ~ 4.3) and mass (~ 1.2 Msol) of HD 209458.


title: Galactic dynamos with captured magnetic flux and an accretion flow

abstract:
  We examine the behaviour of an axisymmetric galactic dynamo model with a
radial accretion flow in the disc. We also introduce a vertical magnetic flux
through the galactic midplane, to simulate the presence of a large scale
magnetic field trapped by the galaxy when forming. The trapped vertical flux is
conserved and advected towards the disc centre by the radial flow. We confirm
that accretion flows of magnitude several km/s through a significant part of
the galactic disc can markedly inhibit dynamo action. Moreover, advection of
the vertical flux in general results in mixed parity galactic fields. However,
the effect is nonlinear and non-additive -- global magnetic field energies are
usually significantly smaller that the sum of purely dynamo generated and
purely advected field energies. For large inflow speeds, a form of
`semi-dynamo' action may occur.
  We apply our results to the accumulation and redistribution, by a radial
inflow, of a vertical magnetic flux captured by the Galactic disc. Taking
representative values, it appears difficult to obtain mean vertical fields near
the centre of the Milky Way that are much in excess of 10 microgauss, largely
because the galactic dynamo and turbulent magnetic diffusion modify the
external magnetic field before it can reach the disc centre.


title: Classification of multifluid CP world models

abstract:
  Various classification schemes exist for homogeneous and isotropic (CP) world
models, which include pressureless matter (so-called dust) and Einstein's
cosmological constant Lambda. We here classify the solutions of more general
world models consisting of up to four non-interacting fluids, each with
pressure P, energy density epsilon and an equation of state P = (gamma - 1)
epsilon with 0 <= gamma <= 2.
  In addition to repulsive fluids with negative pressure and positive energy
density, which generalize the classical repulsive (positive) Lambda component,
we consider fluids with negative energy density as well. The latter generalize
a negative Lambda component. This renders possible new types of models that do
not occur among the classical classifications of world models. Singularity-free
periodic solutions as well as further `hill-type', `hollow-type' and
`shifting-type' models are feasible.
  However, if one only allows for three components (dust, radiation and one
repulsive component) in a spatially flat universe the repulsive classical
Lambda fluid (with Lambda > 0) tends to yield the smoothest fits of the
Supernova Ia data from Perlmutter et al. (1999). Adopting the SN Ia
constraints, exotic negative energy density components can be fittingly
included only if the universe consists of four or more fluids.


title:
On the Influence of Magnetic Fields on the Structure of Protostellar
  Jets

abstract:
  We here present the first results of fully three-dimensional (3-D) MHD
simulations of radiative cooling pulsed (time-variable) jets for a set of
parameters which are suitable for protostellar outflows. Considering different
initial magnetic field topologies in approximate $equipartition$ with the
thermal gas, i.e., (i) a longitudinal, and (ii) a helical field, both of which
permeating the jet and the ambient medium; and (iii) a purely toroidal field
permeating only the jet, we find that the overall morphology of the pulsed jet
is not very much affected by the presence of the different magnetic field
geometries in comparison to a nonmagnetic calculation. Instead, the magnetic
fields tend to affect essentially the detailed structure and emission
properties behind the shocks at the head and at the pulse-induced internal
knots, particularly for the helical and toroidal geometries. In these cases, we
find, for example, that the $H_\alpha$ emissivity behind the internal knots can
be about three to four times larger than that of the purely hydrodynamical jet.
We also find that some features, like the nose cones that often develop at the
jet head in 2-D calculations involving toroidal magnetic fields, are smoothed
out or absent in the 3-D calculations.


title: X-ray Clusters of Galaxies as Tracers of Structure in the Universe

abstract:
  Clusters of galaxies outline the network of the distribution of visible
matter in the Universe, marking the highest-mass knots where filamentary
structures join together. If we observe the sky in X rays, clusters of galaxies
stand out as cosmic lighthouses by virtue of a thin gas trapped and heated
within their gravitational potential wells. This powerful emission is directly
linked to the total gravitating mass they contain, such that they can be
efficiently used as tracers of the cosmic mass distribution within a sizeable
fraction of the observable Universe. Recent observational campaigns have for
the first time used X-ray clusters to map cosmic structures on scales
approaching 3 billion light years. The emerging picture is remarkably
consistent with the expectation of a low-density Universe dominated by cold
dark matter.


title: Pulsar wind nebulae in supernova remnants

abstract:
  A spherically symmetric model is presented for the interaction of a pulsar
wind with the associated supernova remnant. This results in a pulsar wind
nebula whose evolution is coupled to the evolution of the surrounding supernova
remnant. This evolution can be divided in three stages. The first stage is
characterised by a supersonic expansion of the pulsar wind nebula into the
freely expanding ejecta of the progenitor star. In the next stage the pulsar
wind nebula is not steady; the pulsar wind nebula oscillates between
contraction and expansion due to interaction with the reverse shock of the
supernova remnant: reverberations which propagate forward and backward in the
remnant. After the reverberations of the reverse shock have almost completely
vanished and the supernova remnant has relaxed to a Sedov solution, the
expansion of the pulsar wind nebula proceeds subsonically. In this paper we
present results from hydrodynamical simulations of a pulsar wind nebula through
all these stages in its evolution. The simulations were carried out with the
Versatile Advection Code.


title: IY UMa: accretion disc evolution after superoutburst

abstract:
  CCD photometry of the newly discovered eclipsing dwarf nova IY UMa is used to
study the physical properties of the accretion disc in the late decline and
quiescence stages. Eclipse mapping analysis shows that in these stages the
accretion disc is cool with approximately flat radial brightness temperature
distribution and T_BR about 5000-5500 K. The hot spot is found to lie close
along the stream trajectory at distance 0.36a and 0.25a from the disc center in
February and March. The orbital hump strength decreases by about 30 % in a
month. Taking the smallest possible size of the hot spot, we derive an upper
limit for its brightness temperature, 15900 K and 13800 K, respectively.


title:
Long-term Optical Variability of Radio-Selected Quasars from the FIRST
  Survey

abstract:
  We have obtained single-epoch optical photometry for 201 quasars, taken from
the FIRST Bright Quasar Survey, which span a wide range in radio loudness.
Comparison with the magnitudes of these objects on the POSS-I plates provides
by far the largest sample of long-term variability amplitudes for
radio-selected quasars yet produced. We find the quasars to be more variable in
the blue than in the red band, consistent with work on optically selected
samples. The previously noted trend of decreasing variability with increasing
optical luminosity applies only to radio-quiet objects. Furthermore, we do not
confirm a rise in variability amplitude with redshift, nor do we see any
dependence on radio flux or luminosity. The variability over a radio-optical
flux ratio range spanning a factor of 60,000 from radio-quiet to extreme
radio-loud objects is largely constant, although there is a suggestion of
greater variability in the extreme radio-loud objects. We demonstrate the
importance of Malmquist bias in variability studies, and develop a procedure to
correct for the bias in order to reveal the underlying variability properties
of the sample.


title:
Optical Seeing and Infrared Atmospheric Transparency in the Upper
  Atacama Desert

abstract:
  With plans to build a large IR/optical telescope in the Atacama Desert, a
site survey campaign has been underway since 1998 to characterize the optical
seeing and the IR transparency in the Chajnantor Plateau region. Preliminary
results indicate that the Chajnantor region offers excellent astronomical
observing conditions in the optical and IR. The region is isolated yet easy to
reach, and high quality services are available nearby. We can expect to find:
median optical FWHM seeing approaching values of 0.5"--0.6", a percentage of
photometric nights of 65% or better, of astronomically useful nights in excess
of 80% and median PWV well below 1 mm (with best quartile below 0.5 mm).


title: A Dynamic Interstellar Medium: Recent Numerical Simulations

abstract:
  Recent numerical simulations of the interstellar medium driven by energy
input from supernovae and stellar winds indicate that HI clouds can be formed
by compression in shock waves and colliding turbulent streams without any help
from thermal and gravitational instabilities. The filling factor of the hot
phase in these models does not exceed 20-40% at the midplane. The hot gas is
involved in a systematic vertical outflow at |z|<1-3 kpc, similar to that
expected for galactic fountains, whereas the warm component may remain in
hydrostatic equilibrium. The turbulent velocity is larger in the warmer phases,
being 3, 10 and 40 km/s in the cool, warm and hot phases, respectively,
according to one of the simulations. The models exhibit global variability in
the total kinetic and thermal energy and star formation rate at periods of
(0.4-4)x10^8 yr. Current models are still unable to reproduce dynamo action in
the interstellar gas; we briefly discuss implications of the dynamo theory for
turbulent interstellar magnetic fields.


title: A 2MASS L Dwarf Companion to the Nearby K Dwarf GJ 1048

abstract:
  We report the discovery of a probable L1 companion to the nearby K2 dwarf GJ
1048 using the Two Micron All-Sky Survey (2MASS). This source, 2MASSI
J0235599-233120 or GJ 1048B, has 2MASS near-infrared colors and absolute
magnitudes consistent with an early L dwarf companion with a projected
separation of 250 A.U. The L1 spectral type is confirmed by far-red optical and
low-resolution IR spectroscopy. We present evidence that GJ 1048 is a young
(<~1 Gyr) system, and that GJ 1048B may be a high-mass brown dwarf below the
hydrogen-burning limit. Additional studies of the GJ 1048 system will help
constrain the characteristics of L dwarfs as a function of age and mass.


title: The Second APM UKST Colour Survey for z>4 Quasars

abstract:
  We present the spectra, positions, and finding charts for 31 bright (R<19.3)
colour-selected quasars covering the redshift range z=3.85-4.78, with 4 having
redshifts z>4.5. The majority are in the southern sky (dec<-25 deg). The quasar
candidates were selected for their red (B-R > 2.5) colours from UK or POSSII
Schmidt Plates scanned at the Automated Plate Measuring facility in Cambridge.
Low resolution (~> 10A) spectra were obtained to identify the quasars,
primarily at the Las Campanas Observatory. The highest redshift quasar in our
survey is at z ~ 4.8 (R = 18.7) and its spectrum shows a damped Lyman-alpha
absorption system at z = 4.46. This is currently the highest redshift damped
Lyman-alpha absorber detected. Five of these quasars exhibit intrinsic broad
absorption line features. Combined with the previously published results from
the first part of the APM UKST survey we have now surveyed a total of ~8000 squ
deg of sky i.e. 40% of the high galactic latitude (|b|>30 deg) sky, resulting
in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of
which have z>=4.00.


title: Numerical Analysis of Magnetic Field Amplification by Turbulence

abstract:
  We apply a Fourier spectral numerical method to 3D incompressible MHD
turbulence with a magnetic Prandtl number $Pr \geq 1$. We examine the processes
by which an initially weak, large-scale seed magnetic field and an initially
weak, small-scale, impulse-like seed magnetic field are amplified. We find that
in both cases the magnetic energy spectrum grows at all scales. The growth
rates at different amplification stages are analyzed. For a large-scale seed
magnetic field, the magnetic energy density grows as $\sim t^2$ for the first
few turbulence eddy turnover times, followed by a dynamic growth stage, where
nonlinear interactions between different scales of the turbulence contribute to
an exponential growth rate that is largely determined by the turbulence eddy
turnover time. For a seed magnetic field that is initially set up at a small
scale in the turbulence, during the kinematic development stage, the growth
rate of magnetic energy is $\propto 1/\tau_{max}$, where $\tau_{max}$ is the
eddy turnover time of the smallest eddies of the turbulence. The kinematic
growth stage is followed by a dynamic growth stage, where nonlinearity plays
important role. During such dynamic growth stage, the growth rate of total
magnetic energy is determined by both the magnetic energy amplification within
the turbulence inertial range and that within the turbulence dissipation range.


title: X-ray variability of AGN and correlations with spectral properties

abstract:
  Rapid flux changes in the X-ray emission from active galactic nuclei are
commonly observed. The power-density spectra show a pseudo power-law form with
a turnover at low frequencies and a high frequency break, similar to galactic
black-hole candidates. There have been a few claims for periodicities but these
are not a well-established property of the class. The amplitude of variability
depends on a number of source parameters, including luminosity and spectral
properties. The variability amplitude is correlated with X-ray spectral index,
and anti-correlated with the width of the permitted optical lines. In one
particularly well-observed case, NGC 7469, we see a relationship between the
X-ray and UV variability, which indicates that the dominant emission process
for the X-rays is thermal Comptonization. Variations in the X-ray emission are
related to changes in the UV seed photons, but it appears there must also be a
mechanism - perhaps that which heats the Comptonizing corona - that induces
rapid variability intrinsic to the X-rays.


title:
Colors of 2625 Quasars at 0<z<5 Measured in the Sloan Digital Sky Survey
  Photometric System

abstract:
  We present an empirical investigation of the colors of quasars in the Sloan
Digital Sky Survey (SDSS) photometric system. The sample studied includes 2625
quasars with SDSS photometry. The quasars are distributed in a 2.5 degree wide
stripe centered on the Celestial Equator covering $\sim529$ square degrees.
Positions and SDSS magnitudes are given for the 898 quasars known prior to SDSS
spectroscopic commissioning. New SDSS quasars represent an increase of over
200% in the number of known quasars in this area of the sky. The ensemble
average of the observed colors of quasars in the SDSS passbands are well
represented by a power-law continuum with $\alpha_{\nu} = -0.5$ ($f_{\nu}
\propto \nu^{\alpha}$). However, the contributions of the $3000 {\rm \AA}$ bump
and other strong emission lines have a significant effect upon the colors. The
color-redshift relation exhibits considerable structure, which may be of use in
determining photometric redshifts for quasars. The range of colors can be
accounted for by a range in the optical spectral index with a distribution
$\alpha_{\nu}=-0.5\pm0.65$ (95% confidence), but there is a red tail in the
distribution. This tail may be a sign of internal reddening. Finally, we show
that there is a continuum of properties between quasars and Seyfert galaxies
and we test the validity of the traditional division between the two classes of
AGN.


title: Early dust evolution in protostellar accretion disks

abstract:
  We investigate dust dynamics and evolution during the formation of a
protostellar accretion disk around intermediate mass stars via 2D numerical
simulations. Using three different detailed dust models, compact spherical
particles, fractal BPCA grains, and BCCA grains, we find that even during the
early collapse and the first 10,000 yr of dynamical disk evolution, the initial
dust size distribution is strongly modified. Close to the disk's midplane
coagulation produces dust particles of sizes of several 10 micons (for compact
spherical grains) up to several mm (for fluffy BCCA grains), whereas in the
vicinity of the accretion shock front (located several density scale heights
above the disk), large velocity differences inhibit coagulation. Dust particles
larger than about 1 micron segregate from the smaller grains behind the
accretion shock. Due to the combined effects of coagulation and grain
segregation the infrared dust emission is modified. Throughout the accretion
disk a MRN dust distribution provides a poor description of the general dust
properties. Estimates of the consequences of the "freezing out" of molecules in
protostellar disks should consider strongly modified grains. Physical model
parameters such as the limiting sticking strength and the grains' resistivity
against shattering are crucial factors determining the degree of coagulation
reached. In dense regions (e.g. in the mid-plane of the disk) a steady-state is
quickly attained. High above the equatorial plane coagulation equilibrium is
not reached due to the much lower densities. Here, the dust size distribution
is affected primarily by differential advection, rather than coagulation.


title: Searching for Baryons with Chandra

abstract:
  At low redshifts, measurements of the total baryon content in stars, atomic
and molecular hydrogen, and cluster gas fall a factor of two to four below the
baryon density derived from observed light-element ratios and nucleosynthesis
arguments. A possible hiding place for a significant fraction of the missing
baryons is in the warm/hot gas at temperatures T = 10^{5}-10^{7}K. We present
predictions of the contribution to the soft X-ray background from warm/hot gas
emission calculated using new hydrodynamical simulations and discuss the
possibility of detecting the spectral signature of this gas using the Chandra
X-ray Observatory.


title: New Evidence for Black Hole Event Horizons from Chandra

abstract:
  Previously we claimed that Black Hole X-ray Novae (BHXN) in quiescence are
much less luminous than equivalent Neutron Star X-ray Novae (NSXN). This claim
was based on the quiescent detection of a single short period BHXN (A0620-00,
P(orb)=7.8 hrs) and two longer period BHXN (GRO J1655-40, P(orb)=62.9 hrs; V404
Cyg, P(orb)=155.3 hrs), along with sensitive upper limits. We announce the
detection of two more short period BHXN (GRO J0422+32, P(orb)=5.1 hrs; GS
2000+25, P(orb)=8.3 hrs), an upper limit for a third which is improved by two
orders of magnitude (4U 1543-47, P(orb)=27.0 hrs) and a new, much lower
quiescent measurement of GRO J1655-40. Taken together, these new Chandra
measurements confirm that the quiescent X-ray luminosities of BHXN are
significantly lower than those of NSXN. We argue that this provides strong
evidence for the existence of event horizons in BHXN.


title: Searches for Rare and New Types of Objects

abstract:
  Systematic exploration of the observable parameter space, covered by large
digital sky surveys spanning a range of wavelengths, will be one of the primary
modes of research with a Virtual Observatory (VO). This will include searches
for rare, unusual, or even previously unknown types of astronomical objects and
phenomena, e.g. as outliers in some parameter space of measured properties,
both in the catalog and image domains. Examples from current surveys include
high-redshift quasars, type-2 quasars, brown dwarfs, and a small number of
objects with puzzling spectra. Opening of the time domain will be especially
interesting in this regard. Data-mining tools such as unsupervised clustering
techniques will be essential in this task, and should become an important part
of the VO toolkit.


title: The Evolution of Starburst Galaxies

abstract:
  I review the properties of starburst galaxies in the nearby and distant
universe to decipher their evolution as a distinct extragalactic class. The
physical processes and environments of massive star-formation appear to be
similar out to z = 4, although the modes of triggering are likely quite
different, varied, and still evolving. This is argued with the use of a
structural system that measures the physical conditions of galaxies. This
system provides evidence that starbursts at high-z are triggered by merging,
while nearby starbursts have a host of different triggering mechanisms, none of
which, besides merging, are currently known to exist at z > 2.


title: Supernova types and rates

abstract:
  We review the basic properties of the different supernova types identified in
the current taxonomy, with emphasis on the more recent developments. To help
orienting in the variegate zoo, the optical photometric and spectroscopic
properties of the different supernova types are presented in a number of
summary figures. We also report the latest estimates of the supernova rates and
stress the need for a dedicated effort to measure SN rates at high redshift.


title:
The Peculiar Motions of Early-Type Galaxies in Two Distant Regions VI:
  The Maximum Likelihood Gaussian Algorithm

abstract:
  The EFAR project is designed to measure the properties and peculiar motions
of early-type galaxies in two distant regions. Here we describe the maximum
likelihood algorithm we developed to investigate the correlations between the
parameters of the EFAR database. One-, two-, and three-dimensional gaussian
models are constructed to determine the mean value and intrinsic spread of the
parameters, and the slopes and intrinsic parallel and orthogonal spread of the
Mgb'-Mg2, Mg2-sigma, Mgb'-sigma relations, and the Fundamental Plane. In the
latter case, the cluster peculiar velocities are also determined. We show that
this method is superior to ``canonical'' approaches of least-squares type,
which give biased slopes and biased peculiar velocities. We test the algorithm
with Monte Carlo simulations of mock EFAR catalogues and derive the systematic
and random errors on the estimated parameters. We find that random errors are
always dominant. We estimate the influence of systematic errors due to the way
clusters were selected and the hard limits and uncertainties in the selection
function parameters for the galaxies. We explore the influence of uniform
distributions in the Fundamental Plane parameters and the errors. We conclude
that the mean peculiar motions of the EFAR clusters can be determined reliably.
In particular, the placement of the two EFAR sample regions relative to the
Lauer and Postman dipole allows us to strongly constrain the amplitude of the
bulk motion in this direction.


title:
The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in
  Globular Clusters

abstract:
  High dispersion spectra (R>40,000) for a quite large number of stars at the
main sequence turn-off and at the base of the subgiant branch in NGC6397 and
NGC6752 were obtained with the UVES on Kueyen (VLT UT2). The [Fe/H] values we
found are -2.03+/-0.02+/-0.04 and -1.42+/-0.02+/-0.04 for NGC6397 and NGC6752
respectively, where the first error bars refer to internal errors and the
second ones to systematic errors. In both clusters the [Fe/H] obtained for
TO-stars agree perfectly (within a few per cents) with that obtained for stars
at the base of the RGB. The [O/Fe]=0.21+/-0.05 value we obtain for NGC6397 is
quite low, but it agrees with previous results obtained for giants in this
cluster; also, the star-to-star scatter in both O and Fe is very small,
indicating that this small mass cluster is chemically very homogenous. On the
other side, our results show clearly and for the first time that the O-Na
anticorrelation (up to now seen only for stars on the red giant branches of
globular clusters) is present among unevolved stars in the globular cluster
NGC6752, a more massive cluster than NGC6397. A similar anticorrelation is
present also for Mg and Al, and C and N. It is very difficult to explain the
observed Na-O, and Mg-Al anticorrelation in NGC6752 stars by a deep mixing
scenario; we think it requires some non internal mechanism.


title: Density waves in the shearing sheet I. Swing amplification

abstract:
  The shearing sheet model of a galactic disk is studied anew. The theoretical
description of its dynamics is based on three building blocks: Stellar orbits,
which are described here in epicyclic approximation, the collisionless
Boltzmann equation determining the distribution function of stars in phase
space, and the Poisson equation in order to take account of the self-gravity of
the disk. Using these tools I develop a new formalism to describe perturbations
of the shearing sheet. Applying this to the unbounded shearing sheet model I
demonstrate again how the disturbances of the disk evolve always into `swing
amplified' density waves, i.e. spiral-arm like, shearing density enhancements,
which grow and decay while the wave crests swing by from leading to trailing
orientation. Several examples are given how such `swing amplification' events
are incited in the shearing sheet.


title: Structures in the RM sky

abstract:
  Coherent structures in the distribution of the Faraday rotation measure of
extragalactic radio sources are isolated using wavelet transformation
technique. Signatures of the magnetic fields in the local (Orion) spiral arm,
the Sagittarius and Carina arms, the synchrotron Loop I and, possibly, the
Perseus arm have been revealed using the RM catalogues of Simard-Normandin et
al. (1981, 551 source)and Broten et al. (1988, 663 sources). Unlike earlier
analyses of the RM sky, our approach has allowed us to assess the stability of
the results with respect to modifications of the data sample.
  We estimate the mean magnetic field strength in the Orion arm as 1.4\pm0.3
mkGauss and find clear indication of a magnetic field reversal at a distance of
0.6-1 kpc towards the Galactic centre. Our analysis has revealed for the first
time the extension of the reversal in the Carina arm. The direction of magnetic
field in the Perseus arm is reversed with respect to that in the Orion arm. The
average pitch angle of magnetic field in the nearby spiral arms is 15^\circ,
and the mean field strength in the Sagittarius-Carina and Perseus arms is
1.7\pm0.3 mkGauss and 1.4\pm1.2 mkGauss, respectively. The line-of-sight
magnetic field in Loop I is estimated as 0.9\pm0.3 mkGauss. We find firm
evidence of a dominant even symmetry of the local mean field with respect to
the galactic equator.


title:
Global Magnetic Structures in Spiral Galaxies: Evidence for Dynamo
  Action

abstract:
  Observational evidence for dynamo action in spiral galaxies is reviewed, and
the capabilities of various theories in explaining the basic features of
galactic magnetic fields are discussed. Mean-field dynamo models appear to be
unique in providing a coherent explanation of a wide variety of magnetic
features in spiral galaxies.
  Reliable modelling of global magnetic structures, such as the magnetic ring
in M31, requires detailed knowledge of the rotation curve, the magnitude and
radial profile of turbulent and noncircular systematic velocities, the scale
height of the warm ionized layer, the total gas density, the turbulent scale
and their variations with galactocentric radius. More detailed models involving
the effects of the spiral arms on magnetic field require the knowledge of the
arm-interarm contrasts in the above quantities.


title: The parsec-scale central components of FR I radio galaxies

abstract:
  A majority of a complete sample of 3CR FR I radio galaxies show unresolved
optical nuclear sources on the scales of 0.1 arcsec. About half of the 3CR FR
II radio galaxies observed with the HST also show Compact Central Cores (CCC).
These CCCs have been interpreted as the optical counterparts of the non-thermal
radio cores in these radio galaxies (Chiaberge, Capetti, & Celotti 1999). We
show that the optical flux density of the CCCs in FR Is is correlated with the
radio core prominence. This correlation supports the argument of Chiaberge et
al. that the CCC radiation is of a non-thermal synchrotron origin, which is
relativistically beamed along with the radio emission.


title: Ultra-High Energy Cosmic Rays and Symmetries of Spacetime

abstract:
  High energy cosmic rays allow probing phenomena that are inacessible to
accelerators. Observation of cosmic rays, presumebly protons, with energies
beyond $4 \times 10^{19} eV$, the so-called Greisen-Zatsepin-Kuzmin (GZK)
cut-off, give origin to two puzzles: How do particles accelerate to such
energies ? Are their sources within $50 - 100 Mpc$ from Earth, or Lorentz
invariance is actually a broken symmetry ?