title: The Starlab Environment for Dense Stellar Systems

abstract:
  Traditionally, a simulation of a dense stellar system required choosing an
initial model, running an integrator, and analyzing the output. Almost all of
the effort went into writing a clever integrator that could handle binaries,
triples and encounters between various multiple systems efficiently. Recently,
the scope and complexity of these simulations has increased dramatically, for
three reasons: 1) the sheer size of the data sets, measured in Terabytes, make
traditional `awking and grepping' of a single output file impractical; 2) the
addition of stellar evolution data brings qualitatively new challenges to the
data reduction; 3) increased realism of the simulations invites realistic forms
of `SOS': Simulations of Observations of Simulations, to be compared directly
with observations. We are now witnessing a shift toward the construction of
archives as well as tailored forms of visualization including the use of
virtual reality simulators and planetarium domes, and a coupling of both with
budding efforts in constructing virtual observatories. This review describes
these new trends, presenting Starlab as the first example of a full software
environment for realistic large-scale simulations of dense stellar systems.


title: Detection of HD in emission towards Sagittarius B2

abstract:
  The giant molecular cloud Sagittarius B2, located near the Galactic Centre,
has been observed in the far-infrared by the ISO Long Wavelength Spectrometer.
Wavelengths in the range 47-196 microns were covered with the high resolution
Fabry-Perot spectrometer, giving a spectral resolution of 30-40 km/s. The J=1-0
and J=2-1 rotational transitions of HD fall within this range at 112 microns
and 56 microns. A probable detection was made of the ground state J=1-0 line in
emission but the J=2-1 line was not detected above the noise. This allowed us
to calculate an upper limit on the temperature in the emitting region of
approximately 80 K and a value for the deuterium abundance in the Sgr B2
envelope of D/H=(0.2-11)x10^-6.


title: Discovery of the neutron star nature of SLX 1737-282

abstract:
  SLX 1737-282 is a persistent moderately bright X-ray source 1.2 deg from the
Galactic center. X-ray observations with the Wide Field Cameras on BeppoSAX
have for the first time revealed the true nature of SLX 1737-282: a 15-min long
thermonuclear flash was detected exposing the source as a neutron star in a
binary system. The flash was Eddington-limited constraining the distance to
between 5 and 8 kpc. We analyze BeppoSAX, ROSAT, and RXTE data on SLX 1737-282.
The persistent 0.5-200 keV luminosity is close to or less than 1% of the
Eddington limit which implies a rarely-seen circumstance for thermonuclear
flash activity.


title:
Bow shocks, Wiggling Jets, and Wide-Angle Winds: A High Resolution Study
  of the Entrainment Mechanism of the PV Ceph Molecular (CO) Outflow

abstract:
  We present a new set of high-resolution molecular line maps of the gas
immediately surrounding various Herbig-Haro (HH) knots of the giant HH flow HH
315, from the young star PV Cephei. The observations, aimed at studying the
entrainment mechanism of the 2.6 pc-long HH 315 flow, include IRAM 30m maps of
the 12CO(2-1), 12CO(1-0), and 13CO(1-0) lines, with beam sizes of 11'', 21'',
and 22'', respectively. We compare the morphology and the kinematics of the
outflow gas, as well as the temperature and momentum distribution of the
molecular outflow with those predicted by different entrainment models. With
our detailed study we are able to conclude that jet bow shock entrainment by an
episodic stellar wind, with a time-varying axis, produces most of the
high-velocity molecular outflow observed far from the source. In addition, near
PV Cephei we find evidence for a poorly collimated, wide-angle, molecular
outflow and a collimated wiggling jet-like molecular outflow. We propose that
the poorly collimated component is entrained by a wide-angle wind, and the
collimated component is entrained by a variable jet with internal working
surfaces. If this picture is true, then a stellar wind model which allows for
the coexistence of a wide-angle component and a collimated (jet-like) stellar
wind component is needed to explain the observed properties of the PV Ceph
outflow. The wiggling axis of the redshifted molecular outflow lobe indicates
that the outflow ejection axis is changing over time. We find that the
time-scale of the axis variation shown by the molecular outflow lobe is about a
factor of 10 less than that shown by the large-scale optical HH knots.


title: Inner Molecular Rings in Barred Galaxies: BIMA SONG CO Observations

abstract:
  Although inner star-forming rings are common in optical images of barred
spiral galaxies, observational evidence for the accompanying molecular gas has
been scarce. In this paper we present images of molecular inner rings, traced
using the CO (1-0) emission line, from the
Berkeley-Illinois-Maryland-Association Survey of Nearby Galaxies (BIMA SONG).
We detect inner ring CO emission from all five SONG barred galaxies classified
as inner ring (type (r)). We also examine the seven SONG barred galaxies
classified as inner spiral (type (s)); in one of these, NGC 3627, we find
morphological and kinematic evidence for a molecular inner ring. Inner ring
galaxies have been classified as such based on optical images, which emphasize
recent star formation. We consider the possibility that there may exist inner
rings in which star formation efficiency is not enhanced. However, we find that
in NGC 3627 the inner ring star formation efficiency is enhanced relative to
most other regions in that galaxy. We note that the SONG (r) galaxies have a
paucity of CO and H alpha emission interior to the inner ring (except near the
nucleus), while NGC 3627 has relatively bright bar CO and H alpha emission; we
suggest that galaxies with inner rings such as NGC 3627 may be misclassified if
there are significant amounts of gas and star formation in the bar.


title: The luminosity density of red galaxies

abstract:
  A complete sample of $7.7\times 10^4$ galaxies with five-band imaging and
spectroscopic redshifts from the Sloan Digital Sky Survey is used to determine
the fraction of the optical luminosity density of the Local Universe (redshifts
$0.02<z<0.22$) emitted by red galaxies. The distribution in the space of
rest-frame color, central surface brightness, and concentration is shown to be
highly clustered and bimodal; galaxies fall primarily into one of two distinct
classes. One class is red, concentrated and high in surface brightness; the
other is bluer, less concentrated, and lower in central surface brightness.
Elliptical and bulge-dominated galaxies preferentially belong to the red class.
Even with a very restrictive definition of the red class that includes limits
on color, surface brightness and concentration, the class comprises roughly one
fifth of the number density of galaxies more luminous than $0.05 \Lstar$ and
produces two fifths of the total cosmic galaxy luminosity density at $0.7
\mathrm{\mu m}$. The natural interpretation is that a large fraction of the
stellar mass density of the Local Universe is in very old stellar populations.


title:
An Optical Ultra-High-Resolution Cross-dispersed Echelle Spectrograph
  with Adaptive Optics

abstract:
  A prototype cross-dispersed optical echelle spectrograph of very high
resolution has been designed and built at Steward Observatory and tested at the
Starfire Optical Range (SOR) 1.5 m telescope. It is the first spectrograph to
take advantage of diffraction-limited images provided by adaptive optics in
order to achieve a potential resolving power of $R \sim 600,000$. The
wavelength coverage in a single exposure is about 300 \AA, which is
approximately 100 times that of conventional spectrographs operating at
comparable resolution. This was achieved by recording 60 cross-dispersed orders
across the $18\times 18$ mm$^2$ area of the CCD detector. The total efficiency
of the system, including the sky and telescope transmission, spectrograph and
CCD detector, is measured to be 1.3% at peak, much higher than that of other
ultra-high-resolution spectrographs. Sample stellar spectra with $R \sim
250,000$ are presented.


title:
New Limits on the Polarized Anisotropy of the Cosmic Microwave
  Background at Subdegree Angular Scales

abstract:
  We update the limit from the 90 GHz PIQUE ground-based polarimeter on the
magnitude of any polarized anisotropy of the cosmic microwave radiation. With a
second year of data, we have now limited both Q and U on a ring of 1 degree
radius. The window functions are broad: for E-mode polarization, the effective
l is <l> = 191 +143 -132. We find that the E-mode signal can be no greater than
8.4 microK (95% CL), assuming no B-mode polarization. Limits on a possible
B-mode signal are also presented.


title: The Evolution of Shocks in Blazar Jets

abstract:
  We consider the shock structures that can arise in blazar jets as a
consequence of variations in the jet flow velocity. There are two possible
cases: (1) A double shock system consisting of both a forward and reverse shock
(2) A single shock (either forward or reverse) together with a rarefaction
wave. These possibilities depend upon the relative velocity of the two
different sections of jet. Using previously calculated spherical models for
estimates of the magnetic field and electron number density of the emission
region in the TeV blazar Markarian 501, we show that this region is in the form
of a thin disk, in the plasma rest frame. It is possible to reconcile spectral
and pair opacity constraints for MKN 501 for Doppler factors in the range of
10--20. This is easiest if the corrections for TeV absorption by the infrared
background are not as large as implied by recent models.


title:
The Halo Stars in NGC 5128. III: An Inner-Halo Field and the Metallicity
  Distribution

abstract:
  We present new HST/WFPC2 (V,I) photometry for the red-giant stars in NGC 5128
at a projected distance of 8 kpc from the galaxy center, which probe a mixture
of its inner halo and outer bulge. The color-magnitude diagram shows an old
red-giant branch which is even broader in color than our two previously studied
outer-halo fields (at 21 and 31 kpc), with significant numbers of stars
extending to Solar metallicity and higher. The peak frequency of the
metallicity distribution function (MDF) is at [m/H] ~ -0.4, with even fewer
metal-poor stars than in the outer-halo fields. We find that the main features
of the halo MDF can be reproduced by a simple chemical evolution model in which
early star formation goes on simultaneously with an initial stage of rapid
infall of very metal-poor gas, after which the infall dies away exponentially.
A comparison with the MDF for the NGC 5128 globular clusters indicates that
there is a clear decrease of specific frequency $S_N$ (number of clusters per
unit halo light) with increasing metallicity, from S_N ~ 4-8 at [Fe/H] < -1.6
down to S_N = 1.5 at [Fe/H] > -1. This trend may indicate that globular cluster
formation efficiency is a strong function of the metallicity of the
protocluster gas.


title: A Spectral Diagnostic for Density-Bounded HII Regions

abstract:
  The existence of density-bounded HII regions in spiral galaxies is supported
by means of a spectral indicator based on the intensity of the [OI]6300A
forbidden line. A grid of photoionization models providing spectral information
of density-bounded nebulae is presented in order to test the validity of our
indicator. The indicator is applicable to typical observed HII regions with
solar or higher metallicities, and for the range of ages observed in normal HII
regions. When applying the diagnostic to a large sample of HII regions of
spiral galaxies taken from the literature, we find that a fraction of the
selected HII regions with emission detected in the [OI]6300A line turn out to
be consistent with the predictions of density-bounded photoionization models.
Preliminary estimates of the fraction of Lyman continuum photons escaping
ranges from 20% to 40%. The number of density-bounded HII regions could be even
larger after confirmation of those regions for which the [OI] line was not
detected, provided they are good density-bounded candidates. We stress the
importance of having combined information on both good measurements or reliable
upper limits for the intensity of this line, and good determinations of the
Halpha luminosity for complete samples of HII regions in galaxies in order to
make proper estimations as to whether UV photons escaping from HII regions are
the main source of ionization of the diffuse ionized medium in galaxies.


title:
Variable circular polarisation associated with relativistic ejections
  from GRS 1915+105

abstract:
  We report the discovery of variable circularly polarised radio emission
associated with relativistic ejections from GRS 1915+105, based on observations
with the Australia Telescope Compact Array (ATCA) and the Multi-Element
Radio-Linked Interferometer Network (MERLIN). Following a radio flare in 2001
January, significant and variable circular polarisation, at a fractional level
of 0.2-0.4%, was measured with ATCA at four frequencies between 1-9 GHz.
Following an additional outburst 65 days later in 2001 March, further ATCA
observations measured a comparable sign and level of circular polarisation at
two frequencies. At this second epoch, contemporaneous MERLIN observations
directly imaged a relativistic ejection event and allowed us to confidently
associate both the circularly and linearly polarised emission with the
relativistic ejecta, allowing a detailed measurement of the full polarisation
properties in the optically thin phase. The fractional circular polarisation
spectrum appears to flatten at higher frequencies in 2001 January, when there
is strong evidence for multiple components at different optical depths. While
we cannot conclusively distinguish between synchrotron or propagation-induced
conversion as the origin of the circularly polarised component, we do not
consider that coherent or birefringent scintillation mechanisms are likely. The
implication is therefore that the ejections from GRS 1915+105 are associated
with a significant population of low-energy electrons, with associated
consequences for the energetics of relativistic ejection events. [abridged]


title: On the interaction of FR-II radio sources with the intracluster medium

abstract:
  The effect of the expansion of powerful FR-II radio sources into a cluster
environment is discussed. The analysis considers both the thermal and temporal
evolution of the ICM which has passed through the bow shock of the radio source
and the effect of this swept-up gas on the dynamics of the radio source itself.
The final state of the swept-up ICM is critcally dependent on the thermal
conductivity of the gas. If the gas behind the bow shock expands adiabatically,
and the source is expanding into a steeply falling atmosphere, then a narrow
dense layer will form as the radio source lifts gas out of the cluster
potential. This layer has a cooling time very much less than that of the gas
just ahead of the radio source. This effect does not occur if the thermal
conductivity of the gas is high, or if the cluster atmosphere is shallow. The
swept-up gas also affects the dyamics of the radio source especially as it
slows towards sub-sonic expansion. The preferential accumulation of the
swept-up gas to the sides of the cocoon leads to the aspect ratio of the source
increasing. Eventually the contact surface must become Rayleigh-Taylor unstable
leading both to inflow of the swept-up ICM into the cavity created by the
cocoon, but also substantial mixing of the cooler denser swept-up gas with the
ambient ICM thereby creating a multi-phase ICM. The radio source is likely to
have a marked effect on the cluster on timescales long compared to the age of
the source.


title:
On the atmospheric limitations of ground-based submillimetre astronomy
  using array receivers

abstract:
  The calibration of ground-based submillimetre observations has always been a
difficult process. We discuss how to overcome the limitations imposed by the
submillimetre atmosphere. Novel ways to improve line-of-sight opacity estimates
are presented, resulting in tight relations between opacities at different
wavelengths. The submillimetre camera SCUBA, mounted on the JCMT, is the first
large-scale submillimetre array, and as such is ideal for combatting the
effects of the atmosphere. For example, we find that the off-source pixels are
crucial for removing sky-noise. Benefitting from several years of SCUBA
operation, a database of deep SCUBA observations has been constructed to better
understand the nature of sky-noise and the effects of the atmosphere on
instrument sensitivity. This has revealed several results. Firstly, there is
evidence for positive correlations between sky-noise and seeing and sky-noise
and sky opacity. Furthermore, 850-micron and 450-micron sky-noise are clearly
correlated, suggesting that 450-micron data may be used to correct 850-micron
observations for sky-noise. Perhaps most important of all: if off-source
bolometers are used for sky-noise removal, there is no correlation between
instrument sensitivity and chop throw, for chop throws out to 180 arcsec.
Understanding the effects of submillimetre seeing is also important, and we
find that the JCMT beam is not significantly broadened by seeing, nor is there
an obvious correlation between seeing and pointing excursions.


title: A Very Large Glitch in PSR J1806-2125

abstract:
  PSR J1806-2125 is a pulsar discovered in the Parkes multibeam pulsar survey
with a rotational period of 0.4s and a characteristic age of 65kyr. Between
MJDs 51462 and 51894 this pulsar underwent an increase in rotational frequency
of $\Delta \nu/\nu \approx 16 \times 10^{-6}$. The magnitude of this glitch is
approximately 2.5 times greater than any previously observed in any pulsar and
16 times greater than the mean glitch size. This letter gives the parameters of
the glitch and compares its properties to previously observed events. The
existence of such large and rare glitches offers new hope for attempts to
observe thermal X-ray emission from the internal heat released following a
glitch, and suggests that pulsars which previously have not been observed to
glitch may do so on long timescales.


title:
Studying the Dynamics of Star Forming and IR Luminous Galaxies with
  Infrared Spectroscopy

abstract:
  With the advent of efficient near-IR spectrometers on 10m-class telescopes,
exploiting the new generation of low readout noise, large format detectors, OH
avoidance and sub-arcsecond seeing, 1-2.4 micron spectroscopy is becoming a key
means of obtaining detailed galaxy dynamics and for studies of high-z galaxies.
In the following we present the results of three recent IR spectroscopy studies
on the dynamics of ULIRG mergers, super star clusters in the Antennae, and on
the properties of the rotation curves of z~1 disk galaxies, carried out with
ISAAC on the VLT and NIRSPEC on the Keck.


title: The ERE of the "Red Rectangle" revisited

abstract:
  We present in this paper high signal-to-noise long-slit optical spectra of
the Extended Red Emission (ERE) in the "Red Rectangle" (RR) nebula. These
spectra, obtained at different positions in the nebula, reveal an extremely
complex emission pattern on top of the broad ERE continuum. It is well known
that three features converge at large distance from the central object, in
wavelength and profile to the diffuse interstellar bands (DIBs) at 5797, 5849.8
and 6614 ang., (e.g. Sarre et al., 1995). In this paper we give a detailed
inventory of all spectral subfeatures observed in the 5550--6850 ang. spectral
range. Thanks to our high S/N spectra, we propose 5 new features in the RR that
can be associated with DIBs. For the 5550--6200 ang. spectral range our slit
position was on top of the NE spike of the X shaped nebula. A detailed
description of the spatial profile-changes is given of the strongest features
revealing that even far out in the nebula at 24 arcsec from the central star,
there remains a small shift in wavelength of 1 respectively 2 ang between the
ERE subfeatures and the DIB wavelengths of 5797.11 and 5849.78 ang.


title: Triply deuterated ammonia in NGC 1333

abstract:
  The Caltech Submillimeter Observatory has detected triply deuterated ammonia,
ND3, through its 10a-00s transition near 310 GHz. Emission is found in the NGC
1333 region, both towards IRAS 4A and a position to the South-East where DCO+
peaks. In both cases, the hyperfine ratio indicates that the emission is
optically thin. Column densities of ND3 are 3--6 x 10^11 cm^-2 for T_ex=10 K
and twice as high for T_ex=5 K. Using a Monte Carlo radiative transfer code and
a model of the structure of the IRAS source with temperature and density
gradients, the estimated ND3 abundance is 3.2 x 10^-12 if ND3/H2 is constant
throughout the envelope. In the more likely case that ND3/H2D+ is constant,
ND3/H2 peaks in the cold outer parts of the source at a value of 1.0 x 10^-11.
To reproduce the observed NH3/ND3 abundance ratio of ~1000, grain surface
chemistry requires an atomic D/H ratio of ~0.15 in the gas phase, >10 times
higher than in recent chemical models. More likely, the deuteration of NH3
occurs by ion-molecule reactions in the gas phase, in which case the data
indicate that deuteron transfer reactions are much faster than proton
transfers.


title: Do dusty A stars exhibit accretion signatures in their photospheres?

abstract:
  We determined abundances of O, Ca, Fe, Ba and Y for a sample of dusty and
dust-free A stars, taken from the list of Cheng et al. (1992). Five of the
stars have an infrared-excess due to circumstellar dust. Ongoing accretion from
their circumstellar surroundings might have modified the abundances in the
photospheres of these stars, but our results clearly show, that there is no
difference in the photospheric composition of the dusty and dust-free stars.
Instead all of them show the typical diffusion pattern which diminishes towards
larger rotational velocities.


title: Magnetic helicity in galactic dynamos

abstract:
  Magnetic fields correlated on kiloparsec scales are seen in spiral galaxies.
Their origin could be due to amplification of a small seed field by a turbulent
galactic dynamo. We review the current status of the galactic dynamo,
especially the constraints imposed by magnetic helicity conservation. We
estimate the minimal strength of the large-scale magnetic field which could
arise inspite of the helicity constraint.


title:
Quantification of Uncertainty in the Measurement of Magnetic Fields in
  Clusters of Galaxies

abstract:
  We assess the principal statistical and physical uncertainties associated
with the determination of magnetic field strengths in clusters of galaxies from
measurements of Faraday rotation (FR) and Compton-synchrotron emissions. In the
former case a basic limitation is noted, that the relative uncertainty in the
estimation of the mean-squared FR will generally be at least one third. Even
greater uncertainty stems from the crucial dependence of the Faraday-deduced
field on the coherence length scale characterizing its random orientation; we
further elaborate this dependence, and argue that previous estimates of the
field are likely to be too high by a factor of a few. Lack of detailed spatial
information on the radio emission--and the recently deduced nonthermal X-ray
emission in four clusters--has led to an underestimation of the mean value of
the field in cluster cores. We conclude therefore that it is premature to draw
definite quantitative conclusions from the previously-claimed
seemingly-discrepant values of the field determined by these two methods.


title: Galactic halo cusp-core: tidal compression in mergers

abstract:
  We explain in simple terms how the buildup of dark haloes by merging compact
satellites, as in the CDM cosmology, inevitably leads to an inner cusp of
density profile $\rho \propto r^{-\alpha}$ with $\alpha \gsim 1$, as seen in
cosmological N-body simulations. A flatter halo core with $\alpha <1$ exerts on
the satellites tidal compression in all directions, which prevents deposit of
stripped satellite material in the core region. This makes the satellite orbits
decay from the radius where $\alpha \sim 1$ to the halo centre with no local
tidal mass transfer and thus causes a rapid steepening of the inner profile to
$\alpha >1$. These tidal effects, the resultant steepening of the profile to a
cusp, and the stability of this cusp to tandem mergers with compact satellites,
are demonstrated using N-body simulations. The transition at $\alpha \sim 1$ is
then addressed using toy models in the limiting cases of impulse and adiabatic
approximations and using tidal radii for satellites on radial and circular
orbits. In an associated paper we address the subsequent slow convergence from
either side to an asymptotic stable cusp with $\alpha \gsim 1$. Our analysis
thus implies that an inner cusp is enforced when small haloes are typically
more compact than larger haloes, as in the CDM scenario, such that enough
satellite material makes it intact into the inner halo and is deposited there.
We conclude that a necessary condition for maintaining a flat core, as
indicated by observations, is that the inner regions of the CDM satellite
haloes be puffed up by about 50% such that when they merge into a bigger halo
they would be disrupted outside the halo core. This puffing up could be due to
baryonic feedback processes in small haloes, which may be stimulated by the
tidal compression in the halo cores.


title: Blazhko stars: always distorted?

abstract:
  Reexamination of the amplitude ratios of the photometric and radial velocity
changes of Blazhko RRab stars in their different Blazhko phases shows that a
normal amplitude ratio occurs near the phase of maximum amplitude. Checking the
Fourier parameters of maximum amplitude light curves with different methods
proved, however, that none of these light curves can be regarded as a normal RR
Lyrae type light curve.


title: Will Jets Identify the Progenitors of Type Ia Supernovae?

abstract:
  We use the fact that a Type Ia supernova has been serendipitously discovered
near the jet of the active galaxy 3C 78 to examine the question of whether jets
can enhance accretion onto white dwarfs. One interesting outcome of such a
jet-induced accretion process is an enhanced rate of novae in the vicinity of
jets. We present results of observations of the jet in M87 which appear to have
indeed discovered 11 novae in close proximity to the jet. We show that a
confirmation of the relation between jets and novae and Type Ia supernovae can
finally identify the elusive progenitors of Type Ia supernovae.


title:
The Effects of Planets and Brown Dwarfs on Stellar Rotation and
  Mass-Loss

abstract:
  We examine the effects of the engulfment of planets by giant stars on the
evolution of late-type stars. We show that the rate at which dynamo-generated
magnetic energy is being released exceeds 10% of the wind kinetic energy when
the orbital angular momentum of the engulfed planet is more than ten times the
angular momentum of the star as it leaves the main sequence. A significant
enhancement in the mass-loss rate may be expected in this case, due to the
formation of cool magnetic spots. We use the existing sample of extrasolar
planets to estimate that at least 3.5% of the evolved solar-type stars will be
significantly affected by the presence of planetary companions.


title:
Can Any "Invariants" Be Revealed in Quasi-periodic Phenomena Observed
  From Sco X-1?

abstract:
  Using large number of Rossi X-ray Time Explorer observations of Sco X-1 we
present a detailed investigation of the transition layer (TL) and the
relativistic precession (RP) models. These models predict the existence of the
invariant quantities: an inclination angle delta of the magnetospheric axis
with the normal to the disk for the TLM and a neutron star (NS) mass M_{NS} for
the RPM. Theoretical predictions of both models are tested and their
self-consistency is checked. We establish that: (1) The inferred delta angle is
5.56+/-0.09 degrees. Correlation of the delta-values with the horizontal branch
oscillation (HBO) frequency is rather weak. (2) There is a strong correlation
between an inferred M_{NS} and the HBO frequency in the RPM frameworks. (3) We
infer M_{NS} for different assumptions regarding the relations between the HBO
frequency and the nodal frequency. We find that the inferred M_{NS}=2.7+/-0.1
M_sun cannot be consistent with any EOS of NS matter. We conclude that RPM
fails to describe the data while TLM seems to be compatible.


title:
A Bayesian approach to discrete object detection in astronomical
  datasets

abstract:
  A Bayesian approach is presented for detecting and characterising the signal
from discrete objects embedded in a diffuse background. The approach centres
around the evaluation of the posterior distribution for the parameters of the
discrete objects, given the observed data, and defines the
theoretically-optimal procedure for parametrised object detection. Two
alternative strategies are investigated: the simultaneous detection of all the
discrete objects in the dataset, and the iterative detection of objects. In
both cases, the parameter space characterising the object(s) is explored using
Markov-Chain Monte-Carlo sampling. For the iterative detection of objects,
another approach is to locate the global maximum of the posterior at each
iteration using a simulated annealing downhill simplex algorithm. The
techniques are applied to a two-dimensional toy problem consisting of Gaussian
objects embedded in uncorrelated pixel noise. A cosmological illustration of
the iterative approach is also presented, in which the thermal and kinetic
Sunyaev-Zel'dovich effects from clusters of galaxies are detected in microwave
maps dominated by emission from primordial cosmic microwave background
anisotropies.


title:
Using peak distribution of the cosmic microwave background for MAP and
  Planck data analysis: formalism and simulations

abstract:
  We implement and further refine the recently proposed method (Kashlinsky,
Hern\'andez-Monteagudo & Atrio-Barandela, 2001 - KHA) for a time efficient
extraction of the power spectrum from future cosmic microwave background (CMB)
maps. The method is based on the clustering properties of peaks and troughs of
the Gaussian CMB sky. The procedure takes only ${1/2}[f(\nu)]^2N^2$ steps where
$f(\nu)$ is the fraction of pixels with $|\delta T|\geq\nu$ standard deviations
in the map of $N$ pixels. We use the new statistic introduced in KHA,
$\xi_\nu$, which characterizes spatial clustering of the CMB sky peaks of
progressively increasing thresholds. The tiny fraction of the remaining pixels
(peaks and troughs) contains the required information on the CMB power spectrum
of the entire map. The threshold $\nu$ is the only parameter that determines
the accuracy of the final spectrum. We performed detailed numerical simulations
for parameters of the two-year WMAP and Planck CMB sky data including
cosmological signal, inhomogeneous noise and foreground residuals. In all cases
we find that the method can recover the power spectrum out to the Nyquist scale
of the experiment channel. We discuss how the error bars scale with $\nu$
allowing to decide between accuracy and speed. The method can determine with
significant accuracy the CMB power spectrum from the upcoming CMB maps in only
$\sim(10^{-5}-10^{-3})\times N^2$ operations.


title: Inhomogeneous Big Bang Nucleosynthesis and Mutual Ion Diffusion

abstract:
  We present a study of inhomogeneous big bang nucleosynthesis with emphasis on
transport phenomena. We combine a hydrodynamic treatment to a nuclear reaction
network and compute the light element abundances for a range of inhomogeneity
parameters. We find that shortly after annihilation of electron-positron pairs,
  Thomson scattering on background photons prevents the diffusion of the
remaining electrons. Protons and multiply charged ions then tend to diffuse
into opposite directions so that no net charge is carried. Ions with Z>1 get
enriched in the overdense regions, while protons diffuse out into regions of
lower density. This leads to a second burst of nucleosynthesis in the overdense
regions at T<20 keV, leading to enhanched destruction of deuterium and lithium.
We find a region in the parameter space at 2.1E-10<eta<5.2E-10 where
constraints
  7Li/H<10^{-9.7} and D/H<10^{-4.4} are satisfied simultaneously.


title: High redshift galaxies and the Lyman-alpha forest in a CDM universe

abstract:
  We use a cosmological hydrodynamic simulation of a cold dark matter universe
to investigate theoretically the relationship between high redshift galaxies
and the Lyman=alpha forest at redshift z=3. Galaxies in the simulation are
surrounded by halos of hot gas, which nevertheless contain enough neutral
hydrogen to cause a Ly-alpha flux decrement, its strength increasing with
galaxy mass. A comparison with recent observational data by Adelberger et. al
on the Ly-alpha forest around galaxies reveals that actual galaxies may have
systematically less Ly-alpha absorption within 1 Mpc of them than our simulated
galaxies. In order to investigate this possibility, we add several simple
prescriptions for galaxy feedback on the IGM to the evolved simulation. These
include the effect of photoionizing background radiation coming from galactic
sources, galactic winds whose only effect is to deposit thermal energy into the
IGM, and another, kinetic model for winds, which are assumed to evacuate
cavities in the IGM around galaxies. We find that only the latter is able to
produce a large effect, enough to match the tentative observational data, given
the energy available from star formation in the simulated galaxies. Another
intriguing possibility is that a selection effect is responsible, so that
galaxies with low
  Ly-alpha absorption are preferentially included in the sample. This is also
viable, but predicts very different galaxy properties (including clustering)
than the other scenarios.


title:
Small Scale Structure at High Redshift: IV. Low Ionization Gas
  Intersecting Three Lines of Sight to Q2237+0305

abstract:
  We have obtained Keck HIRES spectra of three images of the gravitationally
lensed QSO 2237+0305 to study low ionization absorption systems and their
differences in terms of projected velocity and column density across the lines
of sight. We detect CaII absorption from our Galaxy, and a system of High
Velocity Clouds from the lensing galaxy (z=0.039). CaII components with total
equivalent widths similar to those of Galactic intermediate and high velocity
clouds are spread out over several hundred km/s at impact parameters of less
than one kpc from the center of the lensing galaxy. We have also studied three
low ionization MgII-FeII systems in detail. All three systems cover all three
lines of sight, suggesting that the gaseous structures giving rise to MgII
complexes are larger than about 0.5 kpc. However, in most cases it is difficult
to trace individual MgII `cloudlets' over distances larger than 200-300 pc,
indicating that typical sizes of the MgII cloudlets are smaller than the sizes
inferred earlier for the individual CIV high ionization gas clouds. We
tentatively interpret the absorption pattern of the strongest MgII system in
terms of an expanding bubble or galactic wind and show that the possible loci
occupied by the model bubble in radius-velocity space overlap with the observed
characteristics of Galactic supershells. (abridged).


title: Chandra Survey of Radio-quiet, High-redshift Quasars

abstract:
  We observed 17 optically-selected, radio-quiet high-redshift quasars with the
Chandra Observatory ACIS, and detected 16 of them. The quasars have redshift
between 3.70 and 6.28 and include the highest redshift quasars known. When
compared to low-redshift quasars observed with ROSAT, these high redshift
quasars are significantly more X-ray quiet. We also find that the X-ray
spectral index of the high redshift objects is flatter than the average at
lower redshift. These trends confirm the predictions of models where the
accretion flow is described by a cold, optically-thick accretion disk
surrounded by a hot, optically thin corona, provided the viscosity parameter
alpha >= 0.02. The high redshift quasars have supermassive black holes with
masses ~10^{10} M_{sun}, and are accreting material at ~0.1 the Eddington
limit. We detect 10 X-ray photons from the z=6.28 quasar SDS 1030+0524, which
may have a Gunn-Peterson trough and be near the redshift of reionization of the
intergalactic medium. The X-ray data place an upper limit on the optical depth
of the intergalactic medium tau(IGM) < 10^6, compared to the lower limit from
the spectrum of Lyalpha and Lybeta, which implies tau(IGM) > 20.


title:
Developing Diagnostics of Molecular Clouds Using Numerical MHD
  Simulations

abstract:
  An important aspect of astrophysical MHD turbulence research is developing
diagnostics to connect simulations with the observable universe. Turbulent
systems are by definition structurally complex in all fluid variables (density,
velocity, and magnetic field), such that they must be described statistically.
By developing and applying diagnostic tools to simulation data, it is possible
to interpret empirical laws for the statistical properties of observed systems
in terms of fundamental dynamical processes, and to identify and calibrate
robust probes of physical parameters that cannot be measured directly. Using
several different examples, I describe how structural diagnostic analyses have
already yielded significant insights into the nature of turbulent molecular
clouds. I review results from several different groups, and discuss directions
for future diagnostics to enhance our understanding of cloud structure and
constrain models of the evolutionary course that governs star formation.


title: Optical spectroscopy of the M15 intermediate velocity cloud

abstract:
  We present echelle spectrograph observations in NaD, at resolutions of
6.2-8.5 km/s, for 11 stars located in the line-of-sight to the M15 intermediate
velocity cloud, which has a radial velocity of 70 km/s. This cloud is a part of
IVC Complex gp. The targets range in magnitude from V=13.3-14.8. Seven of the
observed stars are in the M15 globular cluster, the remaining four being field
stars. Column density ratios of log(N cm^-2)=11.8-12.5 are derived. Combining
the current sightlines with previously-existing data, we find the NaD/HI ratio
in the IVC varies by upto a factor of 25. One cluster star, M15 ZNG-1, was also
observed in Calcium. We find N(CaI)/N(CaII)<0.03 and NaI/CaII=0.25, similar to
values seen in the local ISM. Finally, we detect tentative evidence for IV
absorption in KI towards 3 cluster stars.


title: NICMOS Images of the GG Tau Circumbinary Disk

abstract:
  We present deep, near-infrared images of the circumbinary disk surrounding
the pre-main-sequence binary star, GG Tau A, obtained with NICMOS aboard the
Hubble Space Telescope. The spatially resolved proto-planetary disk scatters
roughly 1.5% of the stellar flux, with a near-to-far side flux ratio of ~1.4,
independent of wavelength, and colors that are comparable to the central
source; all of these properties are significantly different from the earlier
ground-based observations. New Monte Carlo scattering simulations of the disk
emphasize that the general properties of the disk, such as disk flux, near side
to far side flux ratio and integrated colors, can be approximately reproduced
using ISM-like dust grains, without the presence of either circumstellar disks
or large dust grains, as had previously been suggested. A single parameter
phase function is fitted to the observed azimuthal variation in disk flux,
providing a lower limit on the median grain size of 0.23 micron. Our analysis,
in comparison to previous simulations, shows that the major limitation to the
study of grain growth in T Tauri disk systems through scattered light lies in
the uncertain ISM dust grain properties. Finally, we use the 9 year baseline of
astrometric measurements of the binary to solve the complete orbit, assuming
that the binary is coplanar with the circumbinary ring. We find that the
estimated 1 sigma range on disk inner edge to semi-major axis ratio, 3.2 <
Rin/a < 6.7, is larger than that estimated by previous SPH simulations of
binary-disk interactions.


title:
A Search for Radio Emission from Supernovae With Ages from About One
  Week to More Than 80 Years

abstract:
  We report VLA radio observations of 29 SNe with ages ranging from 10 days to
about 90 years past explosion. These observations significantly contribute to
the existing data pool on such objects. Included are detections of known radio
SNe~1950B, 1957D, 1970G, 1983N, the suspected radio SN 1923A, and the possible
radio SN 1961V. None of the remaining 23 observations resulted in detections,
providing further evidence to support the observed trend that most SNe are not
detectable radio emitters. To investigate the apparent lack of radio emission
from the SNe reported here, we have followed standard practice and used
Chevalier's ``standard model'' to derive (upper limits to) the mass-loss rates
for the super nova progenitors. These upper limits to the fluxes are consistent
with a lack of circumstellar material needed to provide detectable radio
emission for SNe at these ages and distances. Comparison of the radio
luminosities of these supernovae as a function of age past explosion to other
well-observed radio SNe indicates that the Type II SNe upper limits are more
consistent with the extrapolated light curves of SN 1980K than of SN 1979C,
suggesting that SN 1980K may be a more typical radio emitter than SN 1979C. For
completeness, we have included an appendix where the results of analyses of the
non-SN radio sources are presented. Where possible, we make (tentative)
identifications of these sources using various methods.


title:
Deep CCD Surface Photometry of Galaxy Clusters I: Methods and Initial
  Studies of Intracluster Starlight

abstract:
  We report the initial results of a deep imaging survey of galaxy clusters.
The primary goals of this survey are to quantify the amount of intracluster
light as a function of cluster properties, and to quantify the frequency of
tidal debris. We outline the techniques needed to perform such a survey, and we
report findings for the first two galaxy clusters in the survey: Abell 1413,
and MKW 7 . These clusters vary greatly in richness and structure. We show that
our surface photometry reliably reaches to a surface brightness of \mu_v = 26.5
mags per arcsec. We find that both clusters show clear excesses over a
best-fitting r^{1/4} profile: this was expected for Abell 1413, but not for MKW
7. Both clusters also show evidence of tidal debris in the form of plumes and
arc-like structures, but no long tidal arcs were detected. We also find that
the central cD galaxy in Abell 1413 is flattened at large radii, with an
ellipticity of $\approx 0.8$, the largest measured ellipticity of any cD galaxy
to date.


title: Galaxies on the Blue Edge

abstract:
  We have successfully constructed a catalog of HI-rich galaxies selected from
the Minnesota Automated Plate Scanner Catalog of the Palomar Observatory Sky
Survey (POSS I) based solely on optical criteria. We identify HI-rich
candidates by selecting the bluest galaxies at a given apparent magnitude,
those galaxies on the "blue edge" of POSS I color-magnitude parameter space.
Subsequent 21-cm observations on the upgraded Arecibo 305m dish detected over
50% of the observed candidates. The detected galaxies are HI-rich with HI
masses comparable to "normal" high surface brightness disk galaxies and they
have gas mass-to-light ratios ranging from 0.1 to 4.8 (in solar units).
Comparison of our candidate galaxies with known low surface brightness galaxies
(hereafter LSBs) shows that they exhibit similar optical and HI properties to
that population. We also show that previously identified LSBs, including
several LSBs with red B-V colors, preferentially occupy the "blue edge" of POSS
I color-magnitude parameter space. Their presence on the "blue edge" appears to
be a selection effect due to differing plate limits in the two POSS I
bandpasses. This suggests the POSS I is a good filter for separating galaxies
on the higher surface brightness end of the LSB population from the general
population of galaxies in the night sky.


title: Optical and Infrared Observations of Radioactive Elements in Supernovae

abstract:
  At late phases the powering of supernova light curves is often provided by
the decay of radioactive elements synthesized in the explosions. This is
unambiguously revealed when the light curve decline follows the half life time
of the decaying elements, and the bolometric luminosity then directly provides
the mass of ejected radioactive material. I will focus on the best observed
element, Nickel-56, and demonstrate that different supernovae eject different
amounts of this element. SN 1994W ejected very small amounts of nickel,
possibly caused by black hole formation. SN 1998bw may instead have ejected
more Nickel-56 than any other supernova to date.
  I will also discuss our ISO non-detection of [Fe II] 26 micron in SN 1987A,
which can be used to estimate an upper limit on the mass of ejected radioactive
Titanium-44.


title: Simulation Software: Then, Now and Virtual Observatory

abstract:
  Like hardware, evolution of software has had a major impact on the field of
particle simulations. This paper illustrates how simulation software has
evolved, and where it can go. In addition, with the various ongoing Virtual
Observatory efforts, producers of theory data should think more about sharing
their data! Some examples are given of what we can do with our data and how to
share it with our colleagues and observers. In the Appendix we summarize the
findings of an informal data and software usage survey that we took during this
conference.


title: Velocity Fields of Disk Galaxies

abstract:
  Two dimensional velocity fields have been an important tool for nearly 30
years and are instrumental in understanding galactic mass distributions and
deviations from an ideal galactic disk. Recently a number of new instruments
have started to produce more detailed velocity fields of the disks and nuclear
regions of galaxies. This paper summarizes some of the underlying techniques
for constructing velocity fields and deriving rotation curves. It also urges to
simulate observations from the data-cube stage to reject subtle biases in
derived quantities such as rotation curves.


title: A Young Very Low-Mass Object surrounded by warm dust

abstract:
  We present a complete low-resolution (R~100) near-infrared spectrum of the
substellar object GY11, member of the rho-Ophiuchi young association. The
object is remarkable because of its low estimated mass and age and because it
is associated with a mid-infrared source, an indication of a surrounding dusty
disk. Based on the comparison of our spectrum with similar spectra of field
M-dwarfs and atmospheric models, we obtain revised estimates of the spectral
type, effective temperature and luminosity of the central object. These
parameters are used to place the object on a Hertzprung-Russell diagram and to
compare with the prediction of pre-main sequence evolutionary models. Our
analysis suggests that the central object has a very low mass, probably below
the deuterium burning limit and in the range 8-12MJupiter, and a young age,
less than 1Myr. The infrared excess is shown to be consistent with the emission
of a flared, irradiated disk similar to those found in more massive brown dwarf
and TTauri systems. This result suggests that substellar objects, even the
so-called isolated planetary mass objects, found in young stellar associations
are produced in a similar fashion as stars, by core contraction and
gravitational collapse.


title: Measuring the black hole masses of high redshift quasars

abstract:
  A new technique is presented for determining the black-hole masses of
high-redshift quasars from optical spectroscopy. The new method utilizes the
full-width half maximum (FWHM) of the low-ionization MgII emission line and the
correlation between broad-line region (BLR) radius and continuum luminosity at
3000 Angstroms. Using archival UV spectra it is found that the correlation
between BLR radius and 3000 Angstrom luminosity is tighter than the established
correlation with 5100 Angstrom luminosity. Furthermore, it is found that the
correlation between BLR radius and 3000 Ang luminosity is consistent with a
relation of the form $R_{BLR} \propto lambda L_{lambda}^{0.5}$, as expected for
a constant ionization parameter. Using a sample of objects with broad-line
radii determined from reverberation mapping it is shown that the FWHM of MgII
and H beta are consistent with following an exact one-to-one relation, as
expected if both H beta and MgII are emitted at the same radius from the
central ionizing source. The resulting virial black-hole mass estimator based
on rest-frame UV observables is shown to reproduce black-hole mass measurements
based on reverberation mapping to within a factor of 2.5 (1 sigma). Finally,
the new UV black-hole mass estimator is shown to produce identical results to
the established optical (H beta) estimator when applied to 128
intermediate-redshift (0.3<z<0.9) quasars drawn from the Large Bright Quasar
Survey and the radio-selected Molonglo quasar sample. We therefore conclude
that the new UV virial black-hole mass estimator can be reliably used to
estimate the black-hole masses of quasars from z~0.25 through to the peak epoch
of quasar activity at z~2.5 via optical spectroscopy alone.


title: On the radio afterglow of gamma ray bursts

abstract:
  We use the cannonball (CB) model of gamma ray bursts (GRBs) to predict the
spectral and temporal behaviour of their radio afterglows (AGs). A single
simple expression describes the AGs at all times and frequencies; its
high-frequency limit reproduces the successful CB model predictions for optical
and X-ray AGs. We analyze all of the observed radio AGs of GRBs with known
redshifts, including those of the exceptionally close-by GRB 980425. We also
study in detail the time-evolution of the AGs' spectral index. The agreement
between theory and observations is excellent, even though the CB model is
extremely frugal in the number of parameters required to explain the radio
observations. We propose to use the scintillations in the radio AGs of GRBs to
verify and measure the hyperluminal speed of their jetted CBs, whose apparent
angular velocity is of the same order of magnitude as that of galactic pulsars,
consistently measured directly, or via scintillations.


title: Production of ring-like structure in the cocoon of Hercules A

abstract:
  The radio lobes of the radio galaxy Hercules A contain intriguing ring-like
structures concentric with the jet axis. To investigate the occurrence of such
features, we have used hydrodynamic simulations of jets with a range of Mach
numbers (from M=2 to 50) and densities (down to a ratio of 1E-4 relative to the
background) to generate ray-traced images simulating synchrotron emission from
the time-dependent shock structures. We compare these images with observations
of Hercules A, and consider the physical nature and temporal evolution of the
most plausible configurations. We find that the observed ring-like structures
are well explained as nearly annular shocks propagating in the backflow
surrounding the jet. We infer that the jet is oriented at between 30 and 70
degrees to the line of sight, consistent with radio depolarisation observations
of Gizani & Leahy. The observational lack of hot-spots at the extremities of
the radio lobes, and the possible presence of a buried hot-spot near the base
of the western lobe, are explained in terms of the intrinsic brightness
fluctuations and dynamics of the terminal shock of an ultra-light, low Mach
number jet that surges along its axis due to intermittent pinching and
obstruction by turbulent backflow in the cocoon. We conclude from the
appearance of both sides of the Hercules A, that both jets are on the
borderline of becoming fully turbulent.


title:
A New Feature in the Interstellar Extinction Curve at 2700 A: Diamonds
  in the Rough?

abstract:
  Space Telescope Imaging Spectrograph (STIS) and archival International
Ultraviolet Explorer (IUE) data were used to search for structure in the
ultraviolet interstellar extinction curve. Between 1250 and 3200 A, in addition
to the well-known 2175 A bump, there is only one fairly small (10%) absorption
feature at 2700 A. The feature is very broad (>400 A). It coincides extremely
well in position and shape with laboratory measurements of presolar diamond
grains found in meteorites. As this feature appears in both the new STIS and
archival IUE data, it is unlikely to be an instrumental effect. This feature
appears to be ubiquitous in the ISM as it is seen along sightlines toward
various clouds with reddenings in the range of E(B-V) = 0.35 to 1.73 mag. The
identification with diamonds remains tentative since it is based on a single,
weak feature. If the feature is due to interstellar diamonds then they require
an order of magnitude more absorption strength per gram/cm^2 than the presolar
meteoritic diamonds measured in the lab.


title: Extraordinary Late-Time Infrared Emission of Type IIn Supernovae

abstract:
  Near-Infrared (NIR) observations are presented for five Type IIn supernovae
(SN 1995N, SN 1997ab, SN 1998S, SN 1999Z, and SN 1999el) that exhibit strong
infrared excesses at late times (t >= 100 d). H- and K-band emission from these
objects is dominated by a continuum that rises toward longer wavelengths. The
data are interpreted as thermal emission from dust, probably situated in a
pre-existing circumstellar nebula. The IR luminosities implied by single
temperature blackbody fits are quite large,> 10^(41 - 42) erg s^-1, and the
emission evolves slowly, lasting for years after maximum light. For SN 1995N,
the integrated energy release via IR dust emission was 0.5 -- 1 * 10^50 erg. A
number of dust heating scenarios are considered, the most likely being an
infrared echo poweredby X-ray and UV emissions from the shock interaction with
a dense circumstellar medium.


title: Planetary Microlensing at High Magnification

abstract:
  Simulations of planetary microlensing at high magnification that were carried
out on a cluster computer are presented. It was found that the perturbations
due to two-thirds of all planets occur in the time interval [-0.5t_FWHM, 0.5t_
FWHM] with respect to the peak of the microlensing light curve, where t_FWHM is
typically about 14 hours. This implies that only this restricted portion of the
light curve need be intensively monitored for planets, a very significant
practical advantage. Nearly all planetary detections in high magnification
events will not involve caustic crossings. We discuss the issues involved in
determining the planetary parameters in high magnification microlensing events.
Earth mass planets may be detected with 1-m class telescopes if their projected
orbital radii lie within about 1.5 - 2.5 AU. Giant planets are detectable over
a much larger region. For multi-planet systems the perturbations due to
individual planets can be separated under certain conditions. The size of the
source star needs to be determined independently, but the presence of spots on
the source star is likely to be negligible, as is the effect of planetary
motion during an event.


title: The Cyclic Universe: An Informal Introduction

abstract:
  The Cyclic Model is a radical, new cosmological scenario which proposes that
the Universe undergoes an endless sequence of epochs which begin with a `big
bang' and end in a `big crunch.' When the Universe bounces from contraction to
re-expansion, the temperature and density remain finite. The model does not
include a period of rapid inflation, yet it reproduces all of the successful
predictions of standard big bang and inflationary cosmology. We point out
numerous novel elements that have not been used previously which may open the
door to further alternative cosmologies. Although the model is motivated by
M-theory, branes and extra-dimensions, here we show that the scenario can be
described almost entirely in terms of conventional 4d field theory and 4d
cosmology.


title: The largest virialized dark halo in the universe

abstract:
  Using semi-analytic approach, we present an estimate of the properties of the
largest virialized dark halos in the present universe for three different
scenarios of structure formation: SCDM, LCDM and OCDM models. The resulting
virial mass and temperature increase from the lowest values of $1.6 \times
10^{15}h^{-1}M_{\odot}$ and 9.8 keV in OCDM, the mid-range values of $9.0
\times 10^{15}h^{-1}M_{\odot}$ and 31 keV in LCDM, to the highest values of
$20.9 \times 10^{15}h^{-1}M_{\odot}$, 65 keV in SCDM. As compared with the
largest virialized object seen in the universe, the richest clusters of
galaxies, we can safely rule out the OCDM model. In addition, the SCDM model is
very unlikely because of the unreasonably high virial mass and temperature. Our
computation favors the prevailing LCDM model in which superclusters may be
marginally regarded as dynamically-virialized systems.


title:
The X-ray jet in the Crab Nebula: radical implications for pulsar
  theory?

abstract:
  The recent Chandra image of the Crab nebula shows a striking, axisymmetric
polar jet. It is shown that jets are formed in axisymmetric, magnetized pulsar
winds and that the jet luminosity scales relative to the total as
(\gamma_0\sigma_{eq})^{-4/3}, where \sigma_{eq} is the ratio of Poynting flux
to particle kinetic energy output at the equator at the base of the flow and
\gamma_0 the initial Lorentz factor of the flow. The results are applied to the
image of the Crab nebula, and the limit is set for the Crab pulsar of
\sigma_{eq} \leq 100. It is argued that conventional pulsar theory needs to be
reexamined in light of these limits.


title: The Sun and the Newton Constant

abstract:
  Several properties of the solar interior are determined with a very high
accuracy, which in some cases is comparable to that achieved in the
determination of the Newton constant $G_N$. We find that the present
uncertainty $\Delta G_N/G_N=\pm 1.5\cdot 10^{-3}$ has significant effects on
the profile of density and pressure, however it has negligible influence on the
solar properties which can be measured by means of helioseismology and $^8{\rm
B}$ neutrinos. Our result do not support recent claims that observational solar
data can be used to determine the value of $G_N$ with an accuracy of few part
in $10^{-4}$. Present data cannot constrain $G_N$ to much better than
$10^{-2}$.


title:
High speed photometry of faint Cataclysmic Variables: II. RS Car, V365
  Car,] V436 Car, AP Cru, RR Cha, BI Ori, CM Phe and V522 Sgr

abstract:
  Short time scale photometric properties of eight faint Cataclysmic Variable
(CV) stars are presented. Nova Carinae 1895 (RS Car) has a photometric
modulation at 1.977 h which could be either an orbital or a superhump period.
Nova Carinae 1948 (V365 Car) shows flickering, but any orbital modulation has a
period in excess of 6 h. The nova-like variable and X-ray source V436 Car has
an orbital modulation at P(orb) = 4.207 h, no detectable period near 2.67 h
(which had previously given it a possible intermediate polar classification),
and Dwarf Nova Oscillations (DNOs) at ~40 s. Nova Crucis 1936 (AP Cru) has a
double humped ellipsoidal modulation at P(orb) = 5.12 h and a stable modulation
at 1837 s characteristic of an intermediate polar. Nova Chamaeleontis 1953 (RR
Cha) is an ecliping system with P(orb) = 3.362 h, but at times shows negative
superhumps at 3.271 h and positive superhumps at 3.466 h. In addition it has a
stable period at 1950 s, characteristic of an intermediate polar. BI Ori is a
dwarf nova which we observed at quiescence and outburst without detecting any
orbital modulation. CM Phe is a nova-like variable for which we confirm Hoard,
Wachter & Kim-Quijano's (2001) value of P(orb) = 6.454 h. We have identified
the remnant of Nova Saggitarii 1931 (V522 Sgr) with a flickering source ~2.2
mag fainter than the previously proposed candidate (which we find to be
non-variable).


title:
Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic
  Variables: II. A Low Inertia Magnetic Accretor Model

abstract:
  The Dwarf Nova Oscillations observed in Cataclysmic Variable (CV) stars are
interpreted in the context of a Low Inertia Accretor model, in which accretion
on to an equatorial belt of the white dwarf primary causes the belt to vary its
angular velocity. The rapid deceleration phase is attributed to propellering.
Evidence that temporary expulsion rather than accretion of gas occurs during
this phase is obtained from the large drop in EUV flux.
  We show that the QPOs are most probably caused by a vertical thickening of
the disc, moving as a travelling wave near the inner edge of the disc. This
alternately obscures and `reflects' radiation from the central source, and is
visible even in quite low inclination systems. A possible excitation mechanism,
caused by winding up and reconnection of magnetic field lines, is proposed.
  We apply the model, deduced largely from VW Hyi observations, to re-interpret
observations of SS Cyg, OY Car, UX UMa, V2051 Oph, V436 Cen and WZ Sge. In the
last of these we demonstrate the existence of a 742 s period in the light
curve, arising from obscuration by the travelling wave, and hence show that the
two principal oscillations are a DNO and its reprocessed companion.


title: Luminosity Effects in Projected Fractals

abstract:
  We analyze examples of projected two dimensional fractals for the case where
the objects studied have a Schechter luminosity function. Our results indicate
that two dimensional catalogues of sources could be of value in detecting the
effects of luminosity functions as well as of large scale structure.


title: Could supermassive black holes be quintessential primordial black holes?

abstract:
  There is growing observational evidence for a population of supermassive
black holes (SMBHs) in galactic bulges. We examine in detail the conditions
under which these black holes must have originated from primordial black holes
(PBHs). We consider the merging and accretion history experienced by SMBHs to
find that, whereas it is possible that they were formed by purely astrophysical
processes, this is unlikely and most probably a populations of primordial
progenitors is necessary. We identify the mass distribution and comoving
density of this population and then propose a cosmological scenario producing
PBHs with the right properties. Although this is not essential we consider PBHs
produced at the end of a period of inflation with a blue spectrum of
fluctuations. We constrain the value of the spectral tilt in order to obtain
the required PBH comoving density. We then assume that PBHs grow by accreting
quintessence showing that their mass scales like the horizon mass while the
quintessence field itself is scaling. We find that if scaling is broken just
before nucleosynthesis (as is the case with some attractive non-minimally
coupled models) we obtain the appropriate PBH mass distribution. Hawking
evaporation is negligible in most cases, but we also discuss situations in
which the interplay of accretion and evaporation is relevant.


title: Parameter estimation for Galactic binaries by LISA

abstract:
  We calculate how accurately parameters of the short-period binaries $(10^{-4}
{Hz} \lsim f\lsim 10^{-2} {Hz})$ will be determined from the gravitational
waves by LISA. In our analysis the chirp signal ${\dot f}$ is newly included as
a fitting parameters and dependence on observational period or wave frequency
is studied in detail. Implications for gravitational wave astronomy are also
discussed quantitatively.


title: Chandra reveals a double-sided X-ray jet in the quasar 3C9 at z=2.012

abstract:
  A Chandra observation of the radio-loud quasar 3C9 at redshift z=2.012 has
revealed extended X-ray emission coincident with the radio jet. Of particular
interest is the appearance of both jet and counterjet, which argues against the
X-ray emission being highly beamed. We present the properties of the jets and
discuss possible scenarios for the X-ray emission, contrasting them with the
single sided jet found in PKS 0637-752, which has a similar X-ray luminosity.
The jet X-ray emission in 3C9 is likely to be due to either nonthermal emission
from a sheath with bulk Lorentz factor less than 1.5, or thermal emission from
shocked cold gas surrounding the quasar. The thermal possibility implies a high
mass for the cold gas unless it is highly clumped.


title: Is the EGRET source 3EG J1621+8203 the radio galaxy NGC 6251?

abstract:
  We discuss the nature of the unidentified EGRET source 3EG J1621+8203. In an
effort to identify the gamma-ray source, we have examined X-ray images of the
field from ROSAT PSPC, ROSAT HRI, and ASCA GIS. Of the several faint X-ray
point sources in the error circle of 3EG J1621+8203, most are stars or faint
radio sources, unlikely to be counterparts to the EGRET source. The most
notable object in the gamma-ray error box is the bright FR I radio galaxy NGC
6251. If 3EG J1621+8203 corresponds to NGC 6251, then it would be the second
radio galaxy to be detected in high energy gamma rays, after Cen A, which
provided the first clear evidence of the detection above 100 MeV of an AGN with
a large-inclination jet. If the detection of more radio galaxies by EGRET has
been limited by its threshold sensitivity, there exists the exciting
possibility that new high energy gamma-ray instruments, with much higher
sensitivity, will detect a larger number of radio galaxies in the future.


title:
Multiwavelength optical observations of chromospherically active binary
  systems. IV. The X-ray/EUV selected binary BK Psc (2RE J0039+103)

abstract:
  We present high resolution echelle spectra taken during four observing runs
from 1999 to 2001 of the recently X-ray/EUV selected chromospherically active
binary BK Psc (2RE J0039+103). Our observations confirm the single-lined
spectroscopic binary(SB1) nature of this system and allow us to obtain, for the
first time,the orbital solution of the system as in the case of a SB2 system.
We have determined precise radial velocities of both components: for the
primary by using the cross correlation technique, and for the secondary by
using its chromospheric emission lines. We have obtained a circular orbit with
an orbital period of 2.1663 days, very close to its photometric period of 2.24
days (indicating synchronous rotation). The spectral type (K5V) we determined
for our spectra and the mass ratio (1.8) and minimum masses (Msin^{3}i)
resulting from the orbital solution are compatible with the observed K5V
primary and an unseen M3V secondary. Using this spectral classification, the
projected rotational velocity (vsini, of 17.1 km/s}) obtained from the width of
the cross-correlation function and the data provided by Hipparcos, we have
derived other fundamental stellar parameters. The kinematics and the
non-detection of the LiI line indicate that it is an old star. The analysis of
the optical chromospheric activity indicators from the CaII H & K to CaII IRT
lines, by using the spectral subtraction technique, indicates that both
components of the binary system show high levels of chromospheric activity.
H_alpha emission above the continuum from both components is a persistent
feature of this system during the period 1999 to 2001 of our observations as
well as in previous observations.


title: Non-emission line young stars of intermediate mass

abstract:
  We present optical spectra of four intermediate mass candidate young stellar
objects that have often been classified as Herbig Ae/Be stars. Typical Herbig
Ae/Be emission features are not present in the spectra of these stars. Three of
them, HD 36917, HD 36982 and HD 37062 are members of the young Orion Nebula
Cluster (ONC). This association constrains their ages to be < 1 Myr. The lack
of appreciable near infrared excess in them suggests the absence of hot dust
close to the central star. But they do possess significant amounts of cold and
extended dust component as revealed by the large excess emission observed at
far infrared wavelengths. Fractional infrared luminosity $L_{ir}/L_{\star}$ and
the dust masses computed from IRAS fluxes are systematically lower than that
found for Herbig Ae/Be stars but higher than those for Vega-like stars. These
stars may then represent the youngest examples of Vega phenomenon known so far.
In contrast, the other star in our sample, HD 58647, is more likely to be a
classical Be star as evident from the low $L_{ir}/L_{\star}$, scarcity of
circumstellar dust, low polarization, presence of H$\alpha$ emission and near
infrared excess and far infrared spectral energy distribution consistent with
free-free emission similar to other well known classical Be stars.


title: A cosmological surprise: the universe accelerates

abstract:
  Review article on the cosmological implications of Type Ia Supernovae for
Europhysics News.


title: Galaxy groups in the 2dF redshift survey: The catalogue

abstract:
  We construct a galaxy groups catalogue from the public 100K data release of
the 2dF galaxy redshift survey. The group identification is carried out using a
slightly modified version of the group finding algorithm developed by Huchra &
Geller. Several tests using mock catalogues allow us to find the optimal
conditions to increase the reliability of the final group sample. A minimum
number of 4 members, an outer number density enhancement of 80 and a linking
radial cutoff of $200 km sec^{-1}$, are the best obtained values from the
analysis. Using these parameters, approximately 90% of groups identified in
real space have a redshift space counterpart. On the other hand the level of
contamination in redshift space reaches to 30 % including a $\sim 6%$ of
artificial groups and $\sim 24%$ of groups associated with binaries or triplets
in real space. The final sample comprise 2209 galaxy groups covering the sky
region described by Colless et al. spanning over the redshift range of $0.003
\leq z \leq 0.25$ with a mean redshift of 0.1.


title: Neutron Star Binaries as Central Engines of GRBs

abstract:
  We describe the results high resolution, hydrodynamic calculations of neutron
star mergers. The model makes use of a new, nuclear equation of state, accounts
for multi-flavour neutrino emission and solves the equations of hydrodynamics
using the smoothed particle hydrodynamics method with more than $10^6$
particles. The merger leaves behind a strongly differentially rotating central
object of $\sim 2.5$ M$_{\odot}$ together with a distribution of hot debris
material. For the most realistic case of initial neutron star spins, no sign of
a collapse to a black hole can be seen. We argue that the differential rotation
stabilizes the central object for $\sim 10^2$ s and leads to superstrong
magnetic fields. We find the neutrino emission from the hot debris around the
freshly-formed, supermassive neutron star to be substantially lower than
predicted previously. Therefore the annihilation of neutrino anti-neutrino
pairs will have difficulties to power very energetic bursts ($\gg 10^{49}$
erg).


title: Transient X-ray Binaries in Elliptical Galaxies

abstract:
  Chandra observations of elliptical galaxies have revealed large numbers of
Low Mass X-ray Binaries (LMXBs) accreting at rates above 10^-9 solar masses per
year. One scenario which generates this transfer rate from an old stellar
population is nuclear driven mass transfer onto a neutron star or black hole
from a Roche lobe filling red giant. However, in our Galaxy, most of these
systems accrete sporadically as transients due to a thermal instability in the
accretion disk. Using the common criterion for disk instability (including
irradiation), we find that this mode of mass transfer leads to transient
accretion for at least 75% of the binary's life. Repeated Chandra observations
of elliptical galaxies should reveal this population. The recurrence times
might exceed 1000 years (depending on the orbital period at the onset of mass
transfer), and outbursts might last for 1-100 years. Mass transfering binaries
can also be formed in old populations via interactions in dense stellar
environments, such as globular clusters. These tend to have shorter orbital
periods and are more likely stable accretors, making them apparently a large
fraction of the elliptical's LMXB population.


title: The Crab pulsar and its environment

abstract:
  We present new data of the Crab pulsar and its environment. Images taken in
the infrared with ISAAC allow us to measure the pulsar spectrum and to reveal
the red knot close to the pulsar. Complementary optical data from VLT and HST
are presented.
  The full article, with full resolution nice color images, is presented in
Messenger, 107, 32


title: Dynamic nonlinearity in large scale dynamos with shear

abstract:
  We supplement the mean field dynamo growth equation with the total magnetic
helicity evolution equation. This provides an explicitly time dependent model
for alpha quenching in dynamo theory. For dynamos without shear, this approach
accounts for the observed large scale field growth and saturation in numerical
simulations. After a significant kinematic phase, the dynamo is resistively
quenched, i.e. the saturation time depends on the microscopic resistivity. This
is independent of whether or not the turbulent diffusivity is resistively
quenched. We find that the approach is also successful for dynamos that include
shear and exhibit migratory waves (cycles). In this case however, whether or
not the cycle period remains of the order of the dynamical time scale at large
magnetic Reynolds numbers does depend how on how the turbulent magnetic
diffusivity quenches. Since this is unconstrained by magnetic helicity
conservation, the diffusivity is presently an input parameter. Comparison to
current numerical experiments suggests a turbulent diffusivity that depends
only weakly on the magnetic Reynolds number, but higher resolution simulations
are needed.


title: Supernova 1998bw - The final phases

abstract:
  The probable association with GRB 980425 immediately put SN 1998bw at the
forefront of supernova research. Here, we present revised late-time BVRI light
curves of the supernova, based on template images taken at the VLT. To follow
the supernova to the very last observable phases we have used HST/STIS. Deep
images taken in June and November 2000 are compared to images taken in August
2001. The identification of the supernova is firmly established. This allows us
to measure the light curve to about 1000 days past explosion. The main features
are a rapid decline up to more than 500 days after explosion, with no sign of
complete positron trapping from the Cobolt-56 decay. Thereafter, the light
curve flattens out significantly. One possible explanation is powering by more
long lived radioactive isotopes, if they are abundantly formed in this
energetic supernova.


title: An Inversion Method for Measuring Beta in Large Redshift Surveys

abstract:
  A precision method for determining the value of Beta= Omega_m^{0.6}/b, where
b is the galaxy bias parameter, is presented. In contrast to other existing
techniques that focus on estimating this quantity by measuring distortions in
the redshift space galaxy-galaxy correlation function or power spectrum, this
method removes the distortions by reconstructing the real space density field
and determining the value of Beta that results in a symmetric signal. To remove
the distortions, the method modifies the amplitudes of a Fourier plane-wave
expansion of the survey data parameterized by Beta. This technique is not
dependent on the small-angle/plane-parallel approximation and can make full use
of large redshift survey data. It has been tested using simulations with four
different cosmologies and returns the value of Beta to +/- 0.031, over a factor
of two improvement over existing techniques.


title: X-ray Emission from Early-Type Galaxies in Groups and Poor Clusters

abstract:
  We present the study of three bright Early-Type galaxies hosted in groups or
poor clusters: NGC 1399, NGC 1404 and NGC 507. We used ROSAT HRI, PSPC and,
when available, higher resolution Chandra data to study the structure of the
X-ray halo. The halo center of NGC 1399 and NGC 507 is dominated by a bright
emission peak coincident with the position of the optical galaxy. This central
peak is not explained by cooling flow models and is likely to be produced by
kinetically heated stellar material. Within the effective radius, the hot gas
distribution is tracing the galactic potential due to luminous matter. At
larger distances the halo dynamics is dominated by dark matter extending on
group and cluster scales. The NGC 1399 complex morphology further requires that
the dark matter distribution has a hierarchical structure or that environmental
effects are producing departures from hydrostatic equilibrium. We found
significant density fluctuations in the hot gas distribution of both NGC 1399
and NGC 507, some of which are explained by the interaction of the
radio-emitting plasma with the surrounding ISM. The remaining structures may be
the result of galaxy-galaxy encounters, wakes produced by the motion of the
galaxy through the ICM or may reflect the inhomogeneity of the cooling process
invoked by many authors to explain the failure of the standard cooling-flow
models. NGC 1404 represents a puzzling case since, despite its similarity with
dominant cluster members, significant differences are found in the hot gas
properties. These conflicting evidences can be explained by environmental
effects, such as stifling of galactic winds by the ICM. Finally, we studied the
population of discrete sources found in proximity of the two dominant galaxies.


title:
The Amplitude Evolution and Harmonic Content of Millisecond Oscillations
  in Thermonuclear X-ray Bursts

abstract:
  We present a comprehensive observational and theoretical analysis of the
amplitudes and profiles of oscillations that occur during thermonuclear X-ray
bursts from weakly-magnetized neutron stars in low mass X-ray binaries. Our
sample contains 59 oscillations from six sources observed with the Rossi X-ray
Timing Explorer. The oscillations that we examined occurred primarily during
the decaying portions of bursts, and lasted for several seconds each. We find
that the oscillations are as large as 15% during the declines of the bursts,
and they appear and disappear due to intrinsic variations in their fractional
amplitudes. However, the maxima in the amplitudes are not related to the
underlying flux in the burst. We derive folded profiles for each oscillation
train to study the pulse morphologies. The mean rms amplitudes of the
oscillations are 5%, although the eclipsing source MXB 1659-298 routinely
produces 10% oscillations in weak bursts. We also produce combined profiles
from all of the oscillations from each source. Using these pulse profiles, we
place upper limits on the fractional amplitudes of harmonic and half-frequency
signals of 0.3% and 0.6%, respectively (95% confidence). We then compare the
pulse morphologies to theoretical profiles from models with one or two
antipodal bright regions on the surface of a rotating neutron star. We find
that if one bright region is present on the star, it must either lie near the
rotational pole or cover nearly half the neutron star in order to be consistent
with the observed lack of harmonic signals. If an antipodal pattern is present,
the hot regions must form very near the rotational equator. We discuss how
these geometric constraints challenge current models for the production of
brightness variations on the surface of a neutron star. (abridged)


title:
Red Giant Branch Stars as Probes of Stellar Populations I: 2MASS
  Calibration and Application to 2MASS GC01

abstract:
  The near-infrared behavior of the red giant branch (RGB hereafter) as a
function of abundance is examined with an unprecedented large sample of 27
Galactic globular clusters with Two Micron All Sky Survey photometry. We
propose a new simplified analyses, involving the zero point of the RGB slope
fit, and derive calibrations for the RGB slope, zero point, and tip. The weak
metallicity sensitivity of the zero point leads to a ``fan''-like diagram for
obtaining the abundance distributions in resolved stellar systems, and
reddening estimates. Finally, we apply the new calibrations to the recently
discovered Galactic globular cluster 2MASS GC01, to derive
[Fe/H]_H96=-1.19+/-0.38 mag. The uncertainty is dominated by the severe
foreground contamination. We estimate an extinction of A_V=21.07+/-2.20 mag
toward the cluster.


title:
Hiding in Plain Sight: Chandra Observations of the Quiescent Neutron
  Star 4U 2129+47 in Eclipse

abstract:
  During a previous outburst phase, the neutron star 4U 2129+47 exhibited
evidence for a spatially extended corona via broad, partial X-ray eclipses
occurring periodically on the 5.24 hr orbit. Since 1983, however, 4U 2129+47
has entered a quiescent state several orders of magnitude fainter. We have
performed a 37 ksec Chandra observation of 4U 2129+47 to determine whether an
extended coronal structure also exists in quiescence. Total eclipses are found,
and the rapidity of the eclipse ingress and egress are used to place upper
limits on the size of the X-ray source. The spectrum is comprised of a soft
component plus a fairly hard power law tail. The former is seen to be
sinusoidally modulated over the orbital period in a manner consistent with
neutral column variations, possibly due to the interaction of an accretion
stream with a (small) disk about the neutron star. We fit realistic atmosphere
models to the soft spectra, and comment on the consistency of the spectra with
cooling neutron star models. It has been suggested that the 4U 2129+47 system
is a hierarchical triple, with the outer body being an F star. We use
differential astrometry to show that the X-ray point source and F star are
spatially coincident to within 0.1". We further compare newly determined upper
limits for the extrinsic neutral column to the reddening of the F star.
Finally, we discuss how future X-ray observations can further constrain models
of quiescent neutron star emission, as well as directly verify the triple
hypothesis.


title:
Quintessence, super-quintessence and observable quantities in
  Brans-Dicke and non-minimally coupled theories

abstract:
  The different definitions for the equation of state of a non-minimally
coupled scalar field that have been introduced in the literature are analyzed.
Particular emphasis is made upon those features that could yield to an
observable way of distinguishing non-minimally coupled theories from General
Relativity, with the same or with alternate potentials. It is found that some
earlier claims on that super-quintessence, a stage of super-accelerated
expansion of the universe, is possible within realistic non-minimally coupled
theories are the result of an arguable definition of the equation of state. In
particular, it is shown that these previous results do not import any
observable consequence, i.e. that the theories are observationally identical to
General Relativity models and that super-quintessence is not more than a
mathematical outcome. Finally, in the case of non-minimally coupled theories
with coupling $F=1+\xi \phi^2$ and tracking potentials, it is shown that no
super-quintessence is possible.


title: Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04-012502.2

abstract:
  We obtained near-infrared spectroscopy of the z=5.74 QSO, SDSSp
J104433.04-012 502.2 with the Infrared Camera and Spectrograph of the Subaru
telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr
for the current Lambda-dominated cosmology. We found a similar strength of the
Fe II (3000-3500 A) emission lines in SDSSp J104433.04-012502.2 as in low
redshift QSOs. This is the highest redshift detection of iron. We subtracted a
power-law continuum from the spectrum and fitted model Fe II emission and
Balmer continuum. The rest equivalent width of Fe II (3000-3500 A) is ~30 A
which is similar to those of low redshift QSOs measured by the same manner. The
chemical enrichment models that assume the life time of the progenitor of SNe
Ia is longer than 1 Gyr predict that weaker Fe II emission than low red shift.
However, none of the observed high redshift (z > 3) QSOs show a systematic dec
rease of Fe II emission compared with low redshift QSOs. This may due to a
shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood.
Another reason of strong Fe II emission at z=5.74 may be longer cosmological
age due to smaller Omega_M.


title:
Circumstellar disks around Herbig Ae/Be stars: polarization, outflows
  and binary orbits

abstract:
  The geometrical relationship between the distribution of circumstellar
matter, observed optical linear polarization, outflows and binary orbital plane
in Herbig Ae/Be stars is investigated. Optical linear polarization measurements
carried out for a number of Herbig Ae/Be stars that are either known to be in
binary systems and/or have bipolar jets are presented in this paper. Available
information on the position angles of polarization, outflows and binary
companions for Herbig Ae/Be stars is compiled and analysed for any possible
correlations. In $\approx 85%$ of the sources the outflow position angle is
within $30^{\circ}$ of being parallel or perpendicular to the polarization
position angle. In $\approx 81%$ of the sources the binary position angle is
within $30^{\circ}$ of being parallel or perpendicular to the polarization
position angle. Out of 15 sources with bipolar outflows, 10 sources have the
binary position angle within $30^{\circ}$ of being perpendicular to the outflow
position angle. These results favour those binary formation mechanisms in which
the binary components and the disks around individual stars or circumbinary
disks are coplanar.


title: The very local Hubble flow

abstract:
  We present Hubble Space Telescope/WFPC2 images of eighteen galaxies situated
in the vicinity of the Local Group (LG) as part of an ongoing snapshot survey
of nearby galaxies. Their distances derived from the magnitude of the tip of
the red giant branch are 1.92+-0.10 Mpc (ESO 294-010), 3.06+-0.37 (NGC404),
3.15+-0.32 (UGCA105), 1.36+-0.07 (SexB), 1.33+-0.08 (NGC3109), 2.64+-0.21
(UGC6817), 2.86$+-0.14 (KDG90), 2.27+-0.19 (IC3104), 2.54+-0.17 (UGC7577),
2.56$+-0.15 (UGC8508), 3.01+-0.29 (UGC8651), 2.61+-0.16 (KKH86), 2.79$+-0.26
(UGC9240), 1.11+-0.07 (SagDIG), 0.94+-0.04 (DDO210), 2.07$+-0.18 (IC5152),
2.23+-0.15 (UGCA438), and 2.45+-0.13 (KKH98).
  Based on the velocity-distance data for 36 nearest galaxies around the LG, we
find the radius of the zero-velocity surface of the LG to be R_0 = (0.94+-0.10)
Mpc, which yields a total mass M_{LG} = (1.3+-0.3)*10^{12} M_{\sun}. The galaxy
distribution around the LG reveals a Local Minivoid which does not contain any
galaxy brighter than M_V=-10 mag within a volume of ~100 Mpc^3. The local
Hubble flow seems to be very cold, having a one-dimensional mean random motion
of ~30 km/s. The best-fit value of the local Hubble parameter is 73+-15 km/s
Mpc^{-1}.
  The luminosity function for the nearby field galaxies is far less steep than
one for members of the nearest groups.


title: Confronting Neutron Star Cooling Theories with New Observations

abstract:
  With the successful launch of Chandra and XMM/Newton X-ray space missions
combined with the lower-energy band observations, we are in the position where
careful comparison of neutron star cooling theories with observations will make
it possible to distinguish among various competing theories. For instance, the
latest theoretical and observational developments already exclude both nucleon
and kaon direct URCA cooling. In this way we can now have realistic hope for
determining various important properties, such as the composition, degree of
superfluidity, the equation of state and steller radius. These developments
should help us obtain better insight into the properties of dense matter.


title: The X-ray jet and halo of PKS 0521-365

abstract:
  Chandra ACIS observations of PKS 0521-365 find that the X-ray emission of
this BL Lac object consists of emission from an unresolved core, a diffuse
halo, and a 2 arcsec jet feature coincident with the inner radio/optical jet. A
comparison with a new ATCA 8.6-GHz map also finds X-ray emission from the
bright hotspot south-east of the nucleus. The jet spectrum, from radio to
X-ray, is probably synchrotron emission from an electron population with a
broken power-law energy distribution, and resembles the spectra seen from the
jets of low-power (FR I) radio galaxies. The hotspot X-ray flux is consistent
with the expectations of synchrotron self-Compton emission from a plasma close
to equipartition, as seen in studies of high-power (FR II) radio galaxies.
While the angular structure of the halo is similar to that found by an analysis
of the ROSAT HRI image, its brightness is seen to be lower with Chandra, and
the halo is best interpreted as thermal emission from an atmosphere of similar
luminosity to the halos around FR I radio galaxies. The X-ray properties of PKS
0521-365 are consistent with it being a foreshortened, beamed, radio galaxy.


title:
Chandra observation of Abell 1689: New determination of mass
  distribution and comparison to lensing measurements

abstract:
  We present a new estimate of the projected X-ray mass of Abell 1689 observed
with Chandra, in an attempt to clarify the issue of whether or not there exists
a discrepancy between X-ray and gravitational lensing mass estimates claimed in
previous investigations based on {\it Einstein}, {\it ROSAT} and {\it ASCA}
observations. A particular attention is paid to examining if there is an offset
between X-ray centroid and central dominant cD galaxy, which may be an
indicator of the presence of local dynamical activities of intracluster gas in
the central core and therefore, explain the discrepancy between X-ray and
lensing mass estimates, if any. The unprecedentedly high spatial resolution
achieved by Chandra allows us to precisely localize the X-ray centroid of Abell
1689, which appears to coincide perfectly with the central cD galaxy. This
fact, along with the symmetry and regularity of the X-ray surface brightness
and temperature distributions, suggests that Abell 1689 is a fully-relaxed
cluster. We thus employ hydrostatic equilibrium hypothesis to determine the
projected mass profile of Abell 1689, and compare it with the results obtained
by different lensing techniques available in the literature. Our analysis
confirms the existance of the discrepancy of a factor of $\sim2$ between X-ray
and lensing mass estimates in the central region of $r\approx0.2$ Mpc, although
the two methods yield essentially consistent result on large radii. If the
perfect coincidence between the X-ray center and the cD galaxy of Abell 1689
detected by Chandra observation is not a projection effect, the central mass
discrepancy between X-ray and lensing measurements may pose a challenge to our
conventional understanding of dynamical evolution of the intracluster gas in
the central regions of clusters.


title: Formation of the binary pulsars J1141-6545 and B2023+46

abstract:
  The binaries PSR J1141-6545 and PSR B2303+46 each appear to contain a white
dwarf which formed before the neutron star. We describe an evolutionary pathway
to produce these two systems. In this scenario, the primary transfers its
envelope onto the secondary which is then the more massive of the two stars,
and indeed sufficiently massive later to produce a neutron star via a
supernova. The core of the primary produces a massive white dwarf which enters
into a common envelope with the core of the secondary when the latter evolves
off the main sequence. During the common envelope phase, the white dwarf and
the core of the secondary spiral together as the envelope is ejected. The
evolutionary history of PSR J1141-6545 and PSR B2303+46 differ after this
phase. In the case of PSR J1141--6545, the secondary (now a helium star)
evolves into contact transferring its envelope onto the white dwarf. We propose
that the vast majority of this material is in fact ejected from the system. The
remains of the secondary then explode as a supernova producing a neutron star.
Generally the white dwarf and neutron star will remain bound in tight, often
eccentric, systems resembling PSR J1141-6545. These systems will spiral in and
merge on a relatively short timescale and may make a significant contribution
to the population of gamma ray burst progenitors. In PSR B2303+46, the
helium-star secondary and white dwarf never come into contact. Rather the
helium star loses its envelope via a wind, which increases the binary
separation slightly. Only a small fraction of such systems will remain bound
when the neutron star is formed (as the systems are wider). Those systems which
are broken up will produce a population of high-velocity white dwarfs and
neutron stars.


title: Waiting for the Big One: A New Class of SGR Outbursts?

abstract:
  It is suggested that magnetars eventually become unstable to a dynamic
overturning instability that destroys most of their dipole moment in a single
event. It is further suggested that such an instability would produce a
supergiant version of the largest soft gamma ray bursts that have thus far been
observed, and that they could be observed out to tens or even $10^2$ Mpc.
Persistent emission and afterglows from the fireball might confirm positive
identification with nearby galaxies and perhaps provide other distinguishing
features as well.


title: A Computer Program to Visualize Gravitational Lenses

abstract:
  Gravitational lenses are presently playing an important role in astrophysics.
By means of these lenses the parameters of the deflector such as its mass,
ellipticity, etc. and Hubble's constant can be determined. Using C, Xforms,
Mesa and Imlib a computer program to visualize this lens effect has been
developed. This program has been applied to generate sequences of images of a
source object and its corresponding images. It has also been used to visually
test different models of gravitational lenses.


title: The BeppoSAX spectrum of the composite galaxy Mrk609

abstract:
  We present Bepposax observations of the starburst/Seyfert composite galaxy
Mrk609. This enigmatic object has an optical spectrum dominated by the features
of starburst galaxies, yet its X-ray luminosity (6.3$\times10^{42}$\lunits) is
typical of an AGN. The X-ray spectrum of Mrk609 can be parameterised by a
single power-law model with a photon index $\Gamma\sim1.6\pm0.1$ and no
evidence for significant absorption above the Galactic value. Long term
variability in both the 0.1-2 keV and 2-10 keV energy bands is detected, again
suggesting that the X-ray emission is dominated by an AGN. The observed broad
Ha component is a factor of 40 below that predicted by the
  X-ray flux implying a deficit of ionizing UV photons.


title:
Two-phase equilibrium and molecular hydrogen formation in damped
  Lyman-alpha systems

abstract:
  Molecular hydrogen is quite underabundant in damped Lyman-alpha systems at
high redshift, when compared to the interstellar medium near the Sun. This has
been interpreted as implying that the gas in damped Lyman-alpha systems is
warm. like the nearby neutral intercloud medium, rather than cool, as in the
clouds which give rise to most H I absorption in the Milky Way. Other lines of
evidence suggest that the gas in damped Lyman-alpha systems -- in whole or part
-- is actually cool; spectroscopy of neutral and ionized carbon, discussed
here, shows that the damped Lyman-alpha systems observed at lower redshift z
$<$ 2.3 are largely cool, while those seen at z $>$ 2.8 are warm (though not
devoid of H2). To interpret the observations of carbon and hydrogen we
constructed detailed numerical models of H2 formation under the conditions of
two-phase thermal equilibrium, like those which account for conditions near the
Sun, but with varying metallicity, dust-gas ratio, $etc$. We find that the low
metallicity of damped Lyman-alpha systems is enough to suppress H2 formation by
many orders of magnitude even in cool diffuse clouds, as long as the ambient
optical/uv radiation field is not too small. For very low metallicity and under
the most diffuse conditions, H2 formation will be dominated by slow gas-phase
processes not involving grains, and a minimum molecular fraction in the range
$10^{-8}-10^{-7}$ is expected.


title:
Galaxy groups in the 2dF redshift survey: Effects of Environment on Star
  Formation

abstract:
  We estimate the fraction of star forming galaxies in a catalogue of groups,
constructed from the 2dF galaxy redshift survey by Merch\'an & Zandivarez. We
use the $\eta$ spectral type parameter of galaxies and subdivide the sample of
galaxies in groups into four types depending on the values of the $\eta$
parameter following Madgwick et al. We obtain a strong correlation between the
relative fraction of galaxies with high star formation and the parent group
virial mass. We find that even in the environment of groups with low virial
mass $M \sim 10^{13} M_{\odot}$ the star formation of their member galaxies is
significantly suppressed. The relation between the fraction of early-type
galaxies and the group virial mass obeys a simple power law spanning over three
orders of magnitude in virial mass. Our results show quantitatively the way
that the presence of galaxies with high star formation rates is inhibited in
massive galaxy systems.


title:
Nonlinear image processing based on optimization of generalized
  information methods

abstract:
  A range of nonlinear image reconstruction procedures based on extremizing the
generalized Shannon entropy, Kullback-Leibler cross-entropy and Renyi
information measures and proposed by the author in early papers is presented.
The ``generalization'' assumes search for the solution over the space of real
bipolar or complex functions. Such an approach allows, first, to reconstruct
signals of any type and physical nature and, secondly, to decrease nonlinear
intensity image distortions caused by measurement errors. All the elaborated
procedures are contained in VLBI ``IMAGE'' program package developed in IAA
RAS.