title:
Spectral Energy Distributions and Age Estimates of 172 Globular Clusters
  in M31

abstract:
  In this paper we present CCD multicolor photometry for 172 globular clusters
(GCs), taken from the Bologna catalog (Battistini et al. 1987), in the nearby
spiral galaxy M31. The observations were carried out by using the National
Astronomical Observatories 60/90 cm Schmidt Telescope in 13 intermediate-band
filters, which covered a range of wavelength from 3800 to 10000A. This provides
a multicolor map of M31 in pixels of 1.7"*1.7". By aperture photometry, we
obtain the spectral energy distributions (SEDs) for these GCs. Using the
relationship between the BATC intermediate-band system used for the
observations and the UBVRI broad-band system, the magnitudes in the B and V
bands are derived. The computed V and B-V are in agreement with the values
given by Battistini et al. (1987) and Barmby et al. (2000). Finally, by
comparing the photometry of each GC with theoretical stellar population
synthesis models, we estimate ages of the sample GCs for different
metallicities. The results show that nearly all our sample GCs have ages more
than 10^{9} years, and most of them are around 10^{10} years old. Also, we find
that GCs fitted by the metal-poor model are generally older than ones fitted by
the metal-rich model.


title: The Frequency of Active and Quiescent Galaxies with Companions

abstract:
  We study the percentage of active, HII and quiescent galaxies with companions
in the Palomar survey. We find that when we separate the galaxies by their
morphological types (ellipticals or spirals), to avoid morphology-density
effects, there is no difference in the percentage of galaxies with companions
among the different activity types.


title:
The Orientation of Accretion Disks Relative to Dust Disks in Radio
  Galaxies

abstract:
  We study the orientation of accretion disks, traced by the position angle of
the jet, relative to the dust disk major axis in a sample of 20 nearby Radio
Galaxies. We find that the observed distribution of angles between the jet and
dust disk major axis is consistent with jets homogeneously distributed over a
polar cap of 77 degrees.


title: CH Cygni I: Observational Evidence for a Disk-Jet Connection

abstract:
  We investigate the role of accretion in the production of jets in the
symbiotic star CH Cygni. Assuming that the rapid stochastic optical variations
in CH Cygni come from the accretion disk, as in cataclysmic variables, we use
changes in this flickering to diagnose the state of the disk in 1997. At that
time, CH Cyg dropped to a very low optical state, and Karovska et al. report
that a radio jet was produced. For approximately one year after the jet
production, the amplitude of the fastest (time scales of minutes) variations
was significantly reduced, although smooth, hour-time-scale variations were
still present. This light curve evolution indicates that the inner disk may
have been disrupted, or emission from this region suppressed, in association
with the mass-ejection event. We describe optical spectra which support this
interpretation of the flickering changes. The simultaneous state change, jet
ejection, and disk disruption suggests a comparison between CH Cygni and some
black-hole-candidate X-ray binaries that show changes in the inner disk radius
in conjunction with discrete ejection events on a wide range of time scales
(e.g., the microquasar GRS 1915+105 and XTE J1550-564).


title: CH Cygni II: Optical Flickering from an Unstable Disk

abstract:
  CH Cygni began producing rapid, stochastic optical variations with the onset
of symbiotic activity in 1963. We use changes in this flickering between 1997
and 2000 to diagnose the state of the accretion disk during this time. In the
1998 high state, the luminosity of the B-band flickering component was
typically more than 20 times higher than in the 1997 and 2000 low states.
Therefore, the physical process or region that produces the flickering was also
primarily responsible for the large optical flux increase in the 1998 high
state. Assuming that the rapid, stochastic optical variations in CH Cygni come
from the accretion disk, as in cataclysmic variable stars, a change in the
accretion rate through the disk led to the 1998 bright state. All flickering
disappeared in 1999, when the accreting WD was eclipsed by the red giant
orbiting with a period of approximately 14 yr, according to the ephemeris of
Hinkle et al. and the interpretation of Eyres et al. We did not find any
evidence for periodic or quasi-periodic oscillations in the optical emission
from CH Cygni in either the high or low state, and we discuss the implications
for magnetic propeller models of this system. As one alternative to propeller
models, we propose that the activity in CH Cygni is driven by accretion through
a disk with a thermal-viscous instability, similar to the instabilities
believed to exist in dwarf novae and suggested for FU Ori pre-main-sequence
stars and soft X-ray transients.


title: Variable stars in the globular cluster M13

abstract:
  Results of a search for variable stars in the central region of the globular
cluster M13 are presented. Prior to this study, 36 variable and suspected
variable stars were known in this cluster (Osborn 2000; Clement et al. 2001).
Of these stars, five were not observed by us. We find v3, v4, v10, v12, and v13
to be constant in light. Surprisingly, only two out of the ten variable star
candidates of Kadla et al. (1980) appear to be variable. Both are RRc
variables. Additionally, three RR Lyrae stars and one SX Phoenicis variable are
discovered. Three close frequencies are detected for an RRc star v36. It
appears that this variable is another multi-periodic RR Lyrae star pulsating in
non-radial modes. Light curves of the three known BL Herculis stars and all
known RR Lyrae stars are presented. The total number of known RR Lyrae stars in
M13 is now nine. Only one is an RRab star. The mean period of RRc variables
amounts to 0.36 +/- 0.05 d, suggesting that M13 should be included in the group
of Oosterhoff type II globular clusters. Mean V magnitudes and ranges of
variation are derived for seven RR Lyrae and three BL Herculis variables.
Almost all observed bright giants show some degree of variability. In
particular, we confirm the variability of two red giants announced to be
variable by Osborn (2000) and in addition find five new cases.


title: The Line Elements in the Hubble Expansion

abstract:
  In this lecture I present the line elements that express the Hubble
expansion. The coordinates here are the spatial coordinates $x$, $y$, $z$, and
the velocity coordinate $v$, which are actually what astronomers use in their
measurements. Two such line elements are presented: the first is the empty
space (no matter exists), and the second with matter filling up the Universe.
These line elements are the comparable to the standard ones, the Minkowski and
the FRW line elements in ordinary general relativity theory.


title:
The FORS Deep Field: Field selection, photometric observations and
  photometric catalog

abstract:
  The FORS Deep Field project is a multi-colour, multi-object spectroscopic
investigation of an approx. 7 times 7 region near the south galactic pole based
mostly on observations carried out with the FORS instruments attached to the
VLT telescopes. It includes the QSO Q 0103-260 (z = 3.36). The goal of this
study is to improve our understanding of the formation and evolution of
galaxies in the young Universe. In this paper the field selection, the
photometric observations, and the data reduction are described. The source
detection and photometry of objects in the FORS Deep Field is discussed in
detail. A combined B and I selected UBgRIJKs photometric catalog of 8753
objects in the FDF is presented and its properties are briefly discussed. The
formal 50% completeness limits for point sources, derived from the co-added
images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and 21.57 in U, B, g, R,
I, J and Ks (Vega-system), respectively. A comparison of the number counts in
the FORS Deep Field to those derived in other deep field surveys shows very
good agreement.


title: Mass of BL Lacs from the Velocity Dispersion of the Host Galaxy

abstract:
  We report on new measurements of the stellar velocity dispersion of 4 BL Lac
objects for which optical spectroscopy was gathered at the ESO 3.6m using
EFOSC2. Assuming the M(BH)--(sigma) relation is valid also for ellipticals
hosting active nuclei we estimate the central BH mass of these BL Lacs.


title: Fast magnetosonic waves in pulsar winds

abstract:
  Fast magnetosonic waves in a magnetically-dominated plasma are investigated.
In the pulsar wind, these waves may transport a significant fraction of the
energy flux. It is shown that the nonlinear steepening and subsequent formation
of multiple shocks is a viable mechanism for the wave dissipation in the pulsar
wind. The wave dissipation both in the free pulsar wind and beyond the wind
termination shock is considered.


title:
Dynamical Evolution of Globular Clusters in the Magellanic Clouds and
  Other Local Systems

abstract:
  Observations of rich LMC and SMC clusters reveal an increasing spread in core
radius with age. This trend likely represents real physical evolution in these
systems. Old Magellanic Cloud clusters appear either extended or compact.
Similar core radius distributions are observed for the Fornax and Sagittarius
dSph cluster systems and in the ``young'' halo Milky Way subsystem. These
observations have implications for both the formation of the Galaxy and the
dynamical evolution of globular clusters.


title: Hipparcos red stars in the HpV_{T2} and VI_C systems

abstract:
  For Hipparcos M, S, and C spectral type stars, we provide calibrated
instantaneous (epoch) Cousins $V-I$ color indices using newly derived
$HpV_{T2}$ photometry. Three new sets of ground-based Cousins $VI$ data have
been obtained for more than 170 carbon and red M giants. These datasets in
combination with the published sources of $VI$ photometry served to obtain the
calibration curves linking Hipparcos/Tycho $Hp-V_{T2}$ with the Cousins $V-I$
index. In total, 321 carbon stars and 4464 M- and S-type stars have new $V-I$
indices. The standard error of the mean $V-I$ is about 0.1 mag or better down
to $Hp\approx9$ although it deteriorates rapidly at fainter magnitudes. These
$V-I$ indices can be used to verify the published Hipparcos $V-I$ color
indices. Thus, we have identified a handful of new cases where, instead of the
real target, a random field star has been observed. A considerable fraction of
the DMSA/C and DMSA/V solutions for red stars appear not to be warranted. Most
likely such spurious solutions may originate from usage of a heavily biased
color in the astrometric processing.


title:
X-rays in the Orion Nebula Cluster: Constraints on the origins of
  magnetic activity in pre-main sequence stars

abstract:
  A recent Chandra/ACIS observation of the Orion Nebula Cluster detected 1075
sources (Feigelson et al. 2002), providing a uniquely large and well-defined
sample to study the dependence of magnetic activity on bulk properties for
stars descending the Hayashi tracks. The following results are obtained: (1)
X-ray luminosities L_t in the 0.5-8 keV band are strongly correlated with
bolometric luminosity with <log L_t/L_bol> = -3.8 for stars with masses 0.7<M<2
Mo, an order of magnitude below the main sequence saturation level; (2) the
X-ray emission drops rapidly below this level in some or all stars with 2<M<3
Mo; (3) the presence or absence of infrared circumstellar disks has no apparent
relation to X-ray levels; and (4) X-ray luminosities exhibit a slight rise as
rotational periods increase from 0.4 to 20 days. This last finding stands in
dramatic contrast to the strong anticorrelation between X-rays and period seen
in main sequence stars.
  The absence of a strong X-ray/rotation relationship in PMS stars, and
particularly the high X-ray values seen in some very slowly rotating stars, is
a clear indication that the mechanisms of magnetic field generation differ from
those operating in main sequence stars. The most promising possibility is a
turbulent dynamo distributed throughout the deep convection zone, but other
models such as alpha-Omega dynamo with `supersaturation' or relic core fields
are not immediately excluded. The drop in magnetic activity in
intermediate-mass stars may reflect the presence of a significant radiative
core. The evidence does not support X-ray production in large-scale star-disk
magnetic fields.


title:
Stellar Archaeology: a Keck Pilot Program on Extremely Metal- Poor Stars
  From the Hamburg/ESO Survey. III. The Lead (Pb) Star HE 0024-2523

abstract:
  We present a detailed abundance analysis, including spectral syntheses, of a
very metal-poor ([Fe/H]= -2.7), peculiar main sequence star, HE0024-2523
detected during the course of the Keck Pilot Program. Radial velocities of this
star were obtained during four different observing runs over a time span of 1.1
years, and demonstrate that it is clearly a short period spectroscopic binary.
An orbital solution was obtained, and orbital parameters were determined with
high precision. The rotational velocity was also measured (vsin i=9.7$\pm$1.5
kms); rotation appears likely to be synchronous with the orbit. The abundance
analysis and spectral syntheses indicate that the object is a CH star
characterized by extreme s-process enrichment, likely due to mass accretion
from an evolved companion which has now probably become a white dwarf. The lead
(Pb) abundance of HE0024-2523 is very high, the same as that of the recently
discovered lead-rich metal-poor star CS 29526-110, [Pb/Fe]=+3.3. The abundance
ratio of the heavy-s to light-s elements, as characterized by Pb and Ba,
[Pb/Ba]=+1.9, is the highest yet found for any metal-poor star, and is about
0.7 dex higher than that of CS29526-110. On the basis of the measured isotopic
ratio of carbon (12C/13C about 6) we argue that the mass donor must have had an
original mass of at least 3 Msun. The unusually short period of this CH star
suggests that it underwent a past common-envelope phase with its evolved
companion. Our results are compared to the latest available models for AGB
yields and s-process nucleosynthesis. We also discuss the possible connection
between HE0024-2523 the lithium depletion of halo stars, and halo blue
straggler formation.


title: Ultra-High Energy Gamma Rays in Geomagnetic Field and Atmosphere

abstract:
  The nature and origin of ultra-high energy (UHE: reffering to > 10^19 eV)
cosmic rays are great mysteries in modern astrophysics. The current theories
for their explanation include the so-called "top-down" decay scenarios whose
main signature is a large ratio of UHE gamma rays to protons. Important step in
determining the primary composition at ultra-high energies is the study of air
shower development. UHE gamma ray induced showers are affected by the
Landau-Pomeranchuk-Migdal (LPM) effect and the geomagnetic cascading process.
In this work extensive simulations have been carried out to study the
characteristics of air showers from UHE gamma rays. At energies above several
times 10^19 eV the shower is affected by geomagnetic cascading rather than by
the LPM effect. The properties of the longitudinal development such as average
depth of the shower maximum or its fluctuations depend strongly on both primary
energy and incident direction. This feature may provide a possible evidence of
the UHE gamma ray presence by fluorescence detectors.


title:
The warm-hot intergalactic medium at z~2.2: Metal enrichment and
  ionization source

abstract:
  Results are presented for our search for warm-hot gas towards the quasar Q
0329-385. We identify ten OVI systems of which two are within 5000 km/s of z_em
and a third one should be of intrinsic origin. The seven remaining systems have
HI column densities 10^13.7<N(HI)<10^15.6 cm^-2. At least ~1/3 of the
individual OVI sub-systems have temperatures T<1x10^5 K and cannot originate in
collisionally ionized gas. Photoionization by a hard UV background field
reproduces well the ionic ratios for metallicities in the range 10^-2.5 -
10^-0.5 solar, with possibly sub-solar N/C relative abundance. For [O/C]=0, the
sizes inferred for the OVI clouds are in some cases larger than the maximum
extent implied by the Hubble flow. This constraint is fulfilled assuming a
moderate overabundance of oxygen relative to carbon. For a soft UV ionizing
spectrum, an overabundance of O/C is required, [O/C]~0.0-1.3. For a hard(soft)
UV spectrum and [O/C]=0(1), the OVI regions have overdensities in 10-40.


title: Black Hole Entropy: Linear or Quadratic?

abstract:
  The entropy S of any mass M can be interpreted as a linear relation with
mass, S of order kM/mg an extensive property with mg the mass of the quantum of
gravity. One can extend this relation to black holes and then we get a
different result, as compared with the "standard" relation S of order k/hc
GM^2, which is quadratic in the mass. We discuss both approaches and apply it
to cosmology.


title:
Jet formation as a result of magnetic flux tube--Kerr black hole
  interaction

abstract:
  Relativistic magnetohydrodynamics can be reformulated in terms of magnetic
flux tubes which turn out to obey equations of non-linear strings. The string
approach is applied to study how a test flux tube falls into a Kerr black hole.
Analytical treatment and numerical simulations show that the leading portion of
the falling tube loses angular momentum and energy as the string breaks, and to
compensate for this loss, momentum and energy has to be generated to conserve
energy and momentum for the tube. Inside the ergosphere the energy of the
leading part can be negative, and the rest of the tube then extracts energy
from the hole. Increasing centrifugal forces eject the part of the tube with
extra positive energy from the ergosphere after a time producing a relativistic
jet.


title:
The Analysis of Isochrone Fitting Methods for Red Giant Branch
  Photometry, and Tip Red Giant Branch Distance Determination

abstract:
  We consider the procedure of isochrone fitting and its application to the
study of red giant branch (RGB) photometry in old stellar populations. This is
extended to consider the problems introduced by the inclusion of
lower-magnitude regions of the Colour Magnitude Diagram (CMD). We refer
especially to our previous paper Frayn & Gilmore (2002), where the details of
our isochrone interpolation and fitting code are explained.
  We address the systematic errors inherent in the process of isochrone
fitting, and investigate the extent to which simple stellar populations can be
recovered from noisy photometric data. We investigate the effects caused by
inaccurate distance estimates, isochrone model variation and photometric
errors. We present results from two studies of approximately coeval stellar
populations, those of the Milky Way Globular Cluster System (MWGCS), and the
Ursa Minor dwarf spheroidal galaxy.
  In addition, we introduce a new method for estimating distances using
photometry of the tip of the RGB which is significantly more robust than the
standard edge-detection filter.


title: Transient chaos and resonant phase mixing in violent relaxation

abstract:
  This paper explores how orbits in a galactic potential can be impacted by
large amplitude time-dependences of the form that one might associate with
galaxy or halo formation or strong encounters between pairs of galaxies. A
period of time-dependence with a strong, possibly damped, oscillatory component
can give rise to large amounts of transient chaos, and it is argued that
chaotic phase mixing associated with this transient chaos could play a major
role in accounting for the speed and efficiency of violent relaxation. Analysis
of simple toy models involving time-dependent perturbations of an integrable
Plummer potential indicates that this chaos results from a broad, possibly
generic, resonance between the frequencies of the orbits and harmonics thereof
and the frequencies of the time-dependent perturbation. Numerical computations
of orbits in potentials exhibiting damped oscillations suggest that, within a
period of 10 dynamical times t_D or so, one could achieve simultaneously both
`near-complete' chaotic phase mixing and a nearly time-independent, integrable
end state.


title: Gravitational waves from instabilities in relativistic stars

abstract:
  This article provides an overview of stellar instabilities as sources of
gravitational waves. The aim is to put recent work on secular and dynamical
instabilities in compact stars in context, and to summarize the current
thinking about the detectability of gravitational waves from various scenarios.
As a new generation of kilometer length interferometric detectors are now
coming online this is a highly topical theme. The review is motivated by two
key questions for future gravitational-wave astronomy: Are the gravitational
waves from various instabilities detectable? If so, what can these
gravitational-wave signals teach us about neutron star physics? Even though we
may not have clear answers to these questions, recent studies of the dynamical
bar-mode instability and the secular r-mode instability have provided new
insights into many of the difficult issues involved in modelling unstable stars
as gravitational-wave sources.


title:
Initial conditions, Discreteness and non-linear structure formation in
  cosmology

abstract:
  In this lecture we address three different but related aspects of the initial
continuous fluctuation field in standard cosmological models. Firstly we
discuss the properties of the so-called Harrison-Zeldovich like spectra. This
power spectrum is a fundamental feature of all current standard cosmological
models. In a simple classification of all stationary stochastic processes into
three categories, we highlight with the name ``super-homogeneous'' the
properties of the class to which models like this, with $P(0)=0$, belong. In
statistical physics language they are well described as glass-like. Secondly,
the initial continuous density field with such small amplitude correlated
Gaussian fluctuations must be discretised in order to set up the initial
particle distribution used in gravitational N-body simulations. We discuss the
main issues related to the effects of discretisation, particularly concerning
the effect of particle induced fluctuations on the statistical properties of
the initial conditions and on the dynamical evolution of gravitational
clustering.


title:
A detailed study of G35.2-0.7N: collimated outflows in a cluster of
  high-mass young stellar objects

abstract:
  We present a series of JCMT, BIMA and VLA observations of the massive
star-forming region associated with G35.2--0.7N. These new observations shed
considerable light on the nature of the outflows in this region. The
combination of our CO, SiO and radio data suggest that there are perhaps as
many as four outflows emanating from the core containing G35.2--0.7N. The most
striking result is that the radio jet is ruled out as the driving source of the
large-scale CO flow. The jet drives its own highly-collimated CO outflow.
Molecular line emission from H13CN and H13CO+ peaks towards the centre of the
large-scale CO outflow, but no radio source is detected within. A third flow
may be seen in SiO emission, which appears to be centred on another peak in
H13CO+. The fourth flow is not seen in CO or SiO, but is inferred from previous
L'-band data and the discovery of a radio source at the proposed centre of this
flow.


title: The disruption time of clusters in selected regions of four galaxies

abstract:
  If the cluster formation rate is constant and the disruption time of clusters
depends on their initial mass as t_dis= t_4 x (M_i/10^4 Msun)^gamma, where M_i
is the initial mass of a cluster, t_4 is the disruption time of a cluster of
M_i=10^4 Msun and gamma is an exponent, then the values of t_4 and gamma can be
derived in a very simple way from the age and mass histograms of large
homogeneous samples of clusters with reliable age and/or mass determinations.
We demonstrate the method and derive the values of t_4 and gamma from cluster
samples in selected fields of four galaxies: M51, M33, SMC and the solar
neighbourhood. The values of the exponent gamma are the same within their
uncertainties in the four galaxies with gamma = 0.62 +- 0.06. However, the
disruption time t_4 of clusters of 10^4 Msun is very different in the different
locations. It is shortest in the inner region of M51 (t_4 = 40 Myr) and highest
in the SMC (t_4=8 Gyr).


title: Jovian dust streams: Probes of the Io plasma torus

abstract:
  Jupiter was discovered to be a source of high speed dust particles by the
Ulysses spacecraft in 1992. These dust particles originate from the volcanic
plumes on Io. They collect electrostatic charges from the plasma environment,
gain energy from the co-rotating electric field of the magnetosphere, and leave
Jupiter with escape speeds over $\rm 200 km s^{-1}$. The dust streams were also
observed by the Galileo and Cassini spacecraft. While Ulysses and Cassini only
had a single encounter with Jupiter, Galileo has continuously monitored the
dust streams in the Jovian magnetosphere since 1996. The observed dust fluxes
exhibit large orbit-to-orbit variability due to both systematic and stochastic
changes. By combining the entire data set, the variability due to stochatic
processes can be approximately removed and a strong variation with Jovian local
time is found. This result is consistent with theoretical expectations and
confirms that the majority of the Jovian dust stream particles originate from
Io rather than other potential sources.


title: Massive Star Evolution Through the Ages

abstract:
  We review the current basic picture of the evolution of massive stars and how
their evolution and structure changes as a function of initial mass. We give an
overview of the fate of modern (Pop I) and primordial (Pop III) stars with
emphasis on massive and very massive stars. For single stars we show how the
type of explosions, the type of remnant and their frequencies changes for
different initial metallicities.


title: Gamma-Ray Bursts and Jet-Powered Supernovae

abstract:
  The last five years have seen growing challenges to the traditional paradigm
of a core collapse supernova powered by the neutrino emission of a young
proto-neutron star. Chief among these challenges are gamma-ray bursts (GRBs)
and the supernovae that seem to accompany them. Here we review some recent -
and not so recent - models for GRBs and supernovae in which strong magnetic
fields, rotation, or accretion into a black hole play a role. The conditions
for these energetic explosions are special and, at this point, there is no
compelling reason to invoke them in the general case. That is, 99% of
supernovae may still operate in the traditional fashion.


title: The Rest of the Story: Radio Pulsars and IR through Gamma-Ray Emission

abstract:
  Recent observations have detected a number of young pulsars from the power
peak in the gamma-ray band to the incoherent photon peak in the optical/IR. We
have made progress on the multiwavelength phenomenology of pulsar emission and
beaming, but a wide variation of light curves between different objects and
different energy bands makes the full story complex. I sketch here a `Unified
Model' of pulsar beaming and summarize the radiation mechanisms and their
interplay in outer magnetosphere models of pulsar high energy emission.


title: Cosmological Perturbation Theory Using the Schr\"odinger Equation

abstract:
  We introduce the theory of non-linear cosmological perturbations using the
correspondence limit of the Schr\"odinger equation. The resulting formalism is
equivalent to using the collisionless Boltzman (or Vlasov) equations which
remain valid during the whole evolution, even after shell crossing. Other
formulations of perturbation theory explicitly break down at shell crossing,
e.g. Eulerean perturbation theory, which describes gravitational collapse in
the fluid limit. This paper lays the groundwork by introducing the new
formalism, calculating the perturbation theory kernels which form the basis of
all subsequent calculations. We also establish the connection with conventional
perturbation theories, by showing that third order tree level results, such as
bispectrum, skewness, cumulant correlators, three-point function are exactly
reproduced in the appropriate expansion of our results. We explicitly show that
cumulants up to N=5 predicted by Eulerian perturbation theory for the dark
matter field $\delta$ are exactly recovered in the corresponding limit. A
logarithmic mapping of the field naturally arises in the Schr\"odinger context,
which means that tree level perturbation theory translates into (possibly
incomplete) loop corrections for the conventional perturbation theory. We show
that the first loop correction for the variance is $\sigma^2 = \sigma_L^2+
(-1.14+n)\sigma_L^4$ for a field with spectral index $n$. This yields 1.86 and
0.86 for $n=-3,-2$ respectively, and to be compared with the exact loop order
corrections 1.82, and 0.88. Thus our tree-level theory recovers the dominant
part of first order loop corrections of the conventional theory, while
including (partial) loop corrections to infinite order in terms of $\delta$.


title: Topological Defects in Contracting Universes

abstract:
  We study the behaviour and consequences of cosmic string networks in
contracting universes. They approximately behave during the collapse phase as a
radiation fluids. Scaling solutions describing this are derived and tested
against high-resolution numerical simulations. A string network in a
contracting universe, together with the gravitational radiation it generates,
can affect the dynamics of the universe both locally and globally, and be an
important source of radiation, entropy and inhomogeneity. We discuss possible
implications for bouncing and cyclic models.


title:
Mirror matter in the solar system: New evidence for mirror matter from
  Eros

abstract:
  Mirror matter is an entirely new form of matter predicted to exist if mirror
symmetry is a fundamental symmetry of nature. Mirror matter has the right broad
properties to explain the inferred dark matter of the Universe and might also
be responsible for a variety of other puzzles in particle physics,
astrophysics, meteoritics and planetary science. It is known that mirror matter
can interact with ordinary matter non-gravitationally via photon-mirror photon
kinetic mixing. The strength of this possibly fundamental interaction depends
on the (theoretically) free parameter $\epsilon$. We consider various proposed
manifestations of mirror matter in our solar system examining in particular how
the physics changes for different possible values of $\epsilon$. We find new
evidence for mirror matter in the solar system coming from the observed sharp
reduction in crater rates (for craters less than about 100 meters in diameter)
on the asteroid 433 Eros. We also re-examine various existing ideas including
the mirror matter explanation for the anomalous meteorite events, anomalous
slow-down of Pioneer spacecraft etc.


title: The Phoenix Deep Survey: The 1.4 GHz microJansky catalogue

abstract:
  The initial Phoenix Deep Survey (PDS) observations with the Australia
Telescope Compact Array have been supplemented by additional 1.4 GHz
observations over the past few years. Here we present details of the
construction of a new mosaic image covering an area of 4.56 square degrees, an
investigation of the reliability of the source measurements, and the 1.4 GHz
source counts for the compiled radio catalogue. The mosaic achieves a 1-sigma
rms noise of 12 microJy at its most sensitive, and a homogeneous radio-selected
catalogue of over 2000 sources reaching flux densities as faint as 60 microJy
has been compiled. The source parameter measurements are found to be consistent
with the expected uncertainties from the image noise levels and the Gaussian
source fitting procedure. A radio-selected sample avoids the complications of
obscuration associated with optically-selected samples, and by utilising
complementary PDS observations including multicolour optical, near-infrared and
spectroscopic data, this radio catalogue will be used in a detailed
investigation of the evolution in star-formation spanning the redshift range 0
< z < 1. The homogeneity of the catalogue ensures a consistent picture of
galaxy evolution can be developed over the full cosmologically significant
redshift range of interest. The 1.4 GHz mosaic image and the source catalogue
are available on the web at http://www.atnf.csiro.au/~ahopkins/phoenix/ or from
the authors by request.


title:
The Cosmic Lens All-Sky Survey:II. Gravitational lens candidate
  selection and follow-up

abstract:
  We report the final results of the search for gravitationally lensed
flat-spectrum radio sources found in the combination of CLASS (Cosmic Lens All
Sky Survey) and JVAS (Jodrell-Bank VLA Astrometric Survey). VLA observations of
16,503 sources have been made, resulting in the largest sample of arcsec-scale
lens systems available. Contained within the 16,503 sources is a complete
sample of 11,685 sources having two-point spectral indices between 1.4 and 5
GHz flatter than -0.5 and 5 GHz flux densities $\geq$30 mJy. A subset of 8,958
sources form a well-defined statistical sample suitable for analysis of the
lens statistics. We describe the systematic process by which 149 candidate
lensed sources were picked from the statistical sample on the basis of
possessing multiple compact components in the 0.2 arcsec-resolution VLA maps.
Candidates were followed up with 0.05 arcsec resolution MERLIN and 0.003 arcsec
VLBA observations at 5 GHz and rejected as lens systems if they failed
well-defined surface brightness and/or morphological tests. Maps for all the
candidates can be found on the World Wide Web at
http://www.jb.man.ac.uk/research/gravlens/index.html We summarize the
properties of each of the 22 gravitational lens systems in JVAS/CLASS. Twelve
are double-image systems, nine are four-image systems and one is a six-image
system. Thirteen constitute a statistically well-defined sample giving a
point-source lensing rate of 1:690$\pm$190. The interpretation of the results
in terms of the properties of the lensing galaxy population and cosmological
parameters will be published elsewhere. (Abridged)


title: Chandra Studies of the X-ray Point Source Luminosity Functions of M31

abstract:
  Three different M31 disk fields, spanning a range of stellar populations,
were observed by Chandra. We report the X-ray point source luminosity function
(LF) of each region, and the LF of M31's globular clusters, and compare these
with each other and with the LF of the galaxy's bulge. To interpret the results
we also consider tracers of the stellar population, such as OB associations and
supernova remnants. We find differences in the LFs among the fields, but cannot
definitively relate them to the stellar content of the fields. We find that
stellar population information, average and maximum source luminosities, X-ray
source densities, and slopes of the LF are useful in combination.


title:
On the Evolution of the Ionizing Emissivity of Galaxies and Quasars
  Required by the Hydrogen Reionization

abstract:
  The average rate of emission of ionizing radiation per unit volume (or
emissivity) in the universe can be calculated as the ratio of the intensity of
the ionizing background to the mean free path of ionizing photons. The
intensity of the background is measured from the mean transmitted flux of the
Lya forest, and the mean free path is measured from the abundance of Lyman
limit systems, which has been observed so far up to z=4. This yields an
emissivity that is not larger than 7 ionizing photons per Hubble time for each
atom in the universe at z=4, which may reasonably arise from QSOs and
star-forming galaxies. In order for the reionization to end by z=6, and
assuming that the clumping factor of ionized gas during the reionization epoch
is close to unity, this ionizing emissivity cannot decline from z=4 up to z ~ 9
by more than a factor 1.5. If the clumping factor were much larger than unity,
then the emissivity would need to rapidly increase with redshift. Unless the
ionizing emissivity increases substantially from z=4 to z ~ 10 - 20, the
Thomson optical depth to the CMB must be in the range 0.045 < tau < 0.09.


title: Three Emission-Line Galaxies at z~2.4

abstract:
  We present Keck near-infrared and WIYN optical photometry of a sample of
galaxies detected by near-infrared narrowband imaging in the fields of quasar
metal absorption line systems at z~2.4. Wide separations (0.6-1.6/h Mpc) from
the quasars indicates that they are not directly responsible for the absorption
systems. From the color excess of the galaxies we derived line fluxes, star
formation rates, and equivalent widths. The data are consistent with one source
having an active nucleus and two sources containing regions of star formation.
The blue (R-K) colors for the sources suggest relatively lesser dust content.
We discuss possible projects using current wide-field infrared instruments,
which can cover an order of magnitude greater area with modest allocations of
telescope time.


title: The Cosmic Lens All-Sky Survey: I. Source selection and observations

abstract:
  The Cosmic Lens All-Sky Survey (CLASS) is an international collaborative
program which has obtained high-resolution radio images of over 10000
flat-spectrum radio sources in order to create the largest and best studied
statistical sample of radio-loud gravitationally lensed systems. With this
survey, combined with detailed studies of the lenses found therein, constraints
can be placed on the expansion rate, matter density, and dark energy (e.g.
cosmological constant, quintessence) content of the Universe that are
complementary to and independent of those obtained through other methods. CLASS
is aimed at identifying lenses where multiple images are formed from compact
flat-spectrum radio sources, which should be easily identifiable in the radio
maps. Because CLASS is radio-based, dust obscuration in lensing galaxies is not
a factor, and the relative insensitivity of the instrument to environmental
conditions leads to nearly uniform sensitivity and resolution over the entire
survey. In four observing seasons from 1994-1999, CLASS has observed 13783
radio sources with the VLA at 8.4 GHz at 0.2 arcsecond resolution. When
combined with the JVAS survey, the CLASS sample contains over 16,000 images. A
complete sample of 11685 flat-spectrum sources was observed, selected from GB6
catalogue at 4.85 GHz and the NVSS at 1.4 GHz. So far, CLASS has found 16 new
gravitational lens systems, and the JVAS/CLASS survey contains a total of 22
lenses. (Abridged)


title: Hubble Space Telescope Imaging of Brightest Cluster Galaxies

abstract:
  We used the HST WFPC2 to obtain I-band images of the centers of 81 brightest
cluster galaxies (BCGs), drawn from a volume-limited sample of nearby BCGs. The
images show a rich variety of morphological features, including multiple or
double nuclei, dust, stellar disks, point source nuclei, and central surface
brightness depressions. High resolution surface brightness profiles could be
inferred for 60 galaxies. Of those, 88% have well-resolved cores. Twelve
percent of the BCG sample lacks a well-resolved core; all but one of these BCGs
have ``power-law'' profiles. Some of these galaxies have higher luminosities
than any power-law galaxy identified by Faber et al. (1997), and have physical
upper limits on the break radius well below the values observed for core
galaxies of the same luminosity. These results support the idea that the
central structure of early-type galaxies is bimodal in its physical properties,
but also suggest that there exist high luminosity galaxies with power-law
profiles (or unusually small cores). The BCGs in the latter category tend to
fall at the low end of the BCG luminosity function and tend to have low values
of the quantity alpha (the logarithmic slope of the metric luminosity as a
function of radius, at 10 kpc). Since theoretical calculations have shown that
the luminosities and alpha values of BCGs grow with time as a result of
accretion, this suggests a scenario in which elliptical galaxies evolve from
power-law profiles to core profiles through accretion and merging. This is
consistent with theoretical scenarios that invoke the formation of massive
black hole binaries during merger events (Abridged).


title:
The Properties of Microjansky Radio Sources in the HDF-N, SSA13, and
  SSA22 Fields

abstract:
  (abridged) We present multiwavelength observations for a large sample of
microjansky radio sources detected in ultradeep 1.4GHz maps centered on the
Hubble Deep Field-North (HDF-N) and the Hawaii Survey Fields SSA13 and SSA22.
Our spectroscopic redshifts for 169 radio sources reveal a flat median redshift
distribution, and these sources are hosted by similarly luminous optical L*
galaxies, regardless of redshift. This is a serious concern for radio estimates
of the local star formation rate density, as a substantial fraction of the
ultraviolet luminosity density is generated by sub-L* galaxies at low
redshifts. From our submillimeter measurements for 278 radio sources, we find
error-weighted mean 850micron fluxes of 1.72$\pm$0.09 mJy for the total sample,
2.37$\pm$0.13 mJy for the optically-faint (I>23.5) subsample, and 1.04$\pm$0.13
mJy for the optically-bright (I<23.5) subsample. We significantly (>3\sigma)
detect in the submillimeter 50 of the radio sources, 38 with I>23.5.
Spectroscopic redshifts for three of the I<23.5 submillimeter-detected radio
sources are in the range z=1.0-3.4, and all show AGN signatures. Using only the
submillimeter mapped regions we find that 69\pm9% of the submillimeter-detected
radio population are at I>23.5. We also find that 66\pm7% of the S850>5 mJy
(>4\sigma) sources are radio-identified. We find that millimetric redshift
estimates at low redshifts are best made with a FIR template intermediate
between a Milky Way type galaxy and a starburst galaxy, and at high redshifts
with an Arp220 template.


title: The Dynamics of Known Centaurs

abstract:
  We have numerically investigated the long term dynamical behavior of known
Centaurs. This class of objects is thought to constitute the transitional
population between the Kuiper Belt and the Jupiter-family comets (JFCs). In our
study, we find that over their dynamical lifetimes, these objects diffuse into
the JFCs and other sinks, and also make excursions into the Scattered Disk, but
(not surprisingly) do not diffuse into the parameter space representing the
main Kuiper Belt. These Centaurs spend most of their dynamical lifetimes in
orbits of eccentricity 0.2-to-0.6 and perihelion distance 12-to-30 AU. Their
orbital evolution is characterized by frequent close encounters with the giant
planets. Most of these Centaurs will escape from the solar system (or enter the
Oort Cloud), while a fraction will enter the JFC population and a few percent
will impact a giant planet. Their median dynamical lifetime is 9 Myr, although
there is a wide dispersion in lifetimes, ranging from less than 1 Myr to more
than 100 Myr. We find the dynamical evolution of this sample of Centaurs to be
less orderly than the planet-to-planet "hand-off" described in previous
investigations. We discuss the implications of our study for the spatial
distribution of the Centaurs as a whole.


title:
An enshrouded AGN in the merging starburst system Arp~299 revealed by
  BeppoSAX

abstract:
  Using a long (=150 ksec), broad-band (0.1--40 keV) BeppoSAX observation of
the merging starburst system Arp 299 (=IC 694 + NGC 3690) we found the first
unambiguous evidence of the presence of a deeply buried (N_H = 2.5E24 cm-2) AGN
having an intrinsic luminosity of L(0.5-100 keV) = 1.9E43 cgs. The X-ray
spectral properties of this AGN are discussed in detail as well as the thermal
component detected at soft X-ray energies which, most likely, is associated
with the starburst.


title:
New Planetary Nebulae in the Galactic Bulge region with l>0deg - I.
  Discovery method and first results

abstract:
  We present the first results of an [O III] 5007 A interference filter survey
for Planetary Nebulae (PNe) in the Galactic bulge. Covering (at first) the 66
per cent of the survey area, we detected a total of 90 objects, including 25
new PNe, 57 known PNe and 8 known PNe candidates. Deep Halpha+[N II] CCD images
have been obtained as well as low resolution spectra for the newly discovered
PNe. Their spectral signature suggests that the detected emission originates
from a photoionized nebula. In addition, absolute line fluxes have been
measured and the electron densities are given. Accurate optical positions and
optical diameters were also determined.


title: Measurements of group velocity of light in the lake Baikal water

abstract:
  The results of direct measurements of group velocity of light in the lake
Baikal water at the depth of 1100 m are presented. The lake Baikal water
dispersion has been measured at three wavelengths: 370 nm, 470 nm and 525 nm.
The results are in a rather good agreement with theoretical predictions.


title: Photometric Redshifts for the SDSS Early Data Release

abstract:
  The Early Data Release from the Sloan Digital Sky survey provides one of the
largest multicolor photometric catalogs currently available to the astronomical
community. In this paper we present the first application of photometric
redshifts to the $\sim 6$ million extended sources within these data (with 1.8
million sources having $r' < 21$). Utilizing a range of photometric redshift
techniques, from empirical to template and hybrid techniques, we investigate
the statistical and systematic uncertainties present within the redshift
estimates for the EDR data. For $r'<21$ we find that the redshift estimates
provide realistic redshift histograms with an rms uncertainty in the
photometric redshift relation of 0.035 at $r'<18$ and rising to 0.1 at $r'<21$.
We conclude by describing how these photometric redshifts and derived
quantities, such as spectral type, restframe colors and absolute magnitudes,
are stored within the SDSS database. We provide sample queries for searching on
photometric redshifts and list the current caveats and issues that should be
understood before using these photometric redshifts in statistical analyses of
the SDSS galaxies.


title: The XMM-Newton Bright Serendipitous Source Sample

abstract:
  We summarize here the current status of the XMM BSS: a large (about 1000
sources) sample of bright serendipitous XMM sources at high galactic latitude
(|b| > 20 deg).


title: Mid-Infrared Imaging of the Protostellar Binary L1448N--IRS3(A,B)

abstract:
  Mid-infrared (10-25 \micron) imaging of the protostellar binary system
L1448N-IRS3(A,B) is presented. Only one source, IRS3(A), was detected at
mid-infrared wavelengths -- all of the mid-infrared emission from IRS3(A,B)
emanates from IRS3(A). The mid-infrared luminosity of IRS3(A) is $L_{midir} =
1.3(\frac{d}{300\rm{pc}})^2 L_\sun$, which yields a central source mass,
depending on the mass infall rate, of $M_* = 0.2 M_\sun \frac{10^{-6}M_\sun
yr^{-1}}{\dot M}$. The envelope mass surrounding IRS3(A) is $\sim 0.15 M_\sun$,
suggesting that the central source and the envelope are of comparable mass. The
locations of IRS3(A) and IRS3(B) on an $M_{env} - L_{bol}$ diagram indicate
that IRS3(A) and IRS3(B) appear to be class I and class 0 protostars,
respectively.


title: Multi-band optical micro-variability observations of BL Lacertae

abstract:
  We have observed BL Lacertae in the B, R and I bands for 2 nights in July,
1999, and 3 nights in July, 2001. The observations resulted in almost evenly
sampled light curves, with an average sampling interval of ~5 min. The source
is significantly variable in all bands. On average, the variability amplitude
increases from ~5% in the I band, to ~5.5% in the R and ~6.5% in the B band
light curves. The rising and decaying time scales are comparable within each
band, but they increase from the B, to R and I band light curves. The optical
power spectrum shows a red noise component with a slope of ~ -2.
Cross-correlation analysis shows that in most cases the delay between the
variations in the B and I band light curves is less than ~ 0.4 hrs. The
cross-correlation functions are asymmetric, implying complex delays of the I
band variations with respect to the B band variations. Furthermore, in one case
we find that the I band variations are significantly delayed (by ~0.2 hrs) with
respect to the B band variations. We also detect significant spectral
variations: the spectrum becomes steeper as the flux increases, and the
flattest spectral index corresponds to the maximum B band flux. Our results
imply that the fast, intra-night variations of the source correspond to
perturbations of different regions in the jet which cause localized injections
of relativistic particles on time scales much sorter that the average sampling
interval of the light curves. The variations are controlled by the cooling and
light crossing time scales, which are probably comparable.


title: Exploring dark energy using the Statefinder

abstract:
  Observations of high redshift supernovae indicate that the universe is
accelerating. The hypothesis of `Dark energy' (cosmological constant, scalar
field tracker potentials, braneworld models, etc.) has been advanced to explain
this phenomenon. Sensitive tests of dark energy which can differentiate between
rival models are clearly the need of the hour. The statefinder pair $\lbrace
r,s\rbrace$ is a geometrical diagnostic which can play this role. $r$ & $s$
depend upon the third time derivative of the scale factor $\stackrel{...}{a}$
and provide the next logical step in the hierarchy of the cosmological
parameter set after $H$ and $q$. The statefinder pair $\lbrace r,s\rbrace$ can
be determined to high accuracy from a SNAP type experiment and allows us to
successfully differentiate between dark energy models having constant as well
as time-varying equations of state.


title: Microquasars as sources of high energy phenomena

abstract:
  Relativistic outflows are a common phenomenon in accreting black holes.
Despite the enormous differences in scale, accreting stellar-mass black holes
(X-ray binaries, collapsars) and super-massive black holes produce jets with
analogous physical properties. Here I review microquasars as sources of
relativistic jets, gamma-rays, cosmic rays, and high energy neutrinos.


title:
The 0.4-Mo Eclipsing Binary CU Cancri: Absolute Dimensions, Comparison
  with Evolutionary Models and Possible Evidence for a Circumstellar Dust Disk

abstract:
  Photometric observations in the R and I bands of the detached M-type
double-lined eclipsing binary CU Cnc have been acquired and analysed. The
photometric elements obtained from the analysis of the light curves have been
combined with an existing spectroscopic solution to yield high-precision
(errors<2%) absolute dimensions: M_A=0.4333+/-0.0017 Mo, M_B=0.3980+/-0.0014
Mo, R_A=0.4317+/-0.0052 Ro, and R_B=0.3908+/-0.0094 Ro. The mean effective
temperature of the system has been estimated to be Teff=3140+/-150 K by
comparing multi-band photometry with synthetic colors computed from model
atmospheres. Additionally, we have been able to obtain an estimate for the age
(~320 Myr) and chemical composition ([Fe/H]~0.0) of the binary system through
its membership of the Castor moving group. With all these observational
constraints, we have carried out a critical test of recent stellar models for
low-mass stars. The comparison reveals that most evolutionary models
underestimate the radius of the stars by as much as 10%, thus confirming the
trend observed by Torres & Ribas (2002) for YY Gem and V818 Tau. In the
mass-absolute magnitude diagram, CU Cnc is observed to be dimmer than other
stars of the same mass. After ruling out a number of different scenarios, the
apparent faintness of CU Cnc can be explained if its components are some 10%
cooler than similar-mass stars or if there is some source of circumstellar dust
absorption. The latter could be a tantalizing indirect evidence for a coplanar
(Vega-like) dusty disk around this relatively young M-type binary.


title:
Linear wave spectrum associated with collective neutrino-plasma
  interactions in the early universe

abstract:
  The effects of collective neutrino-plasma interactions on the linear wave
spectrum supported by a magnetized electron-positron plasma in the presence of
a neutrino-antineutrino medium are investigated. When a pair-symmetric
background neutrino-plasma medium is perturbed by space-charge waves
(electrostatic waves associated with electron-positron charge separation), our
analysis shows that the neutrino and antineutrino fluids also separate and the
pair symmetry of the background medium is broken. The cosmological implications
of this pair-symmetry breaking mechanism are briefly discussed.


title:
The effect of cooling on the global stability of self-gravitating
  protoplanetary discs

abstract:
  Using a local model Gammie (2001) has shown that accretion discs with cooling
times t_cool <= 3/Omega fragment into gravitationally bound objects, while
those with cooling times t_cool > 3/Omega evolve into a quasi-steady state. We
use three-dimensional smoothed particle hydrodynamic simulations of
protoplanetary accretion discs to test if the local results hold globally. We
find that for disc masses appropriate for T Tauri discs, the fragmentation
boundary still occurs at a cooling time close to t_cool = 3/Omega. For more
massive discs, which are likely to be present at an earlier stage of the star
formation process, fragmentation occurs for longer cooling times, but still
within a factor of two of that predicted using a local model. These results
have implications not only for planet formation in protoplanetary discs and
star formation in AGN discs, but also for the redistribution of angular
momentum which could be driven by the presence of relatively massive objects
within the accretion disc.


title: VLT Observations of Two Unusual BAL Quasars

abstract:
  Among the unusual broad absorption line quasars being found by the Sloan
Digital Sky Survey (SDSS) are objects with much stronger absorption in Fe III
than Fe II. These unusual line ratios require a high density in the outflow
(n_H >= 3 x 10^{10} cm^{-3}). They should also appear for only a limited range
of outflow column densities, which explains their rarity. Previously we
suggested that the Fe III line ratios were also affected by a resonance; we now
believe this is an artifact of structure in the underlying Fe II + Fe III
pseudocontinuum. The SDSS is also discovering objects with absorption in rarely
seen transitions such as He I. VLT+UVES high-resolution spectra of one such
object, the mini-BAL quasar SDSS 1453+0029, show that it has two He I
absorption systems with considerably different properties separated by only 350
km/s.


title:
The power spectrum amplitude from clusters revisited: \sigma_8 using
  simulations with preheating and cooling

abstract:
  The amplitude of density perturbations, for the currently-favoured LambdaCDM
cosmology, is constrained using the observed properties of galaxy clusters. The
catalogue used is that of Ikebe et al. (2002). The cluster temperature to mass
relation is obtained via N-body/hydrodynamical simulations including radiative
cooling and preheating of cluster gas, which we have previously shown to
reproduce well the observed temperature--mass relation in the innermost parts
of clusters (Thomas et al. 2002). We generate and compare mock catalogues via a
Monte Carlo method, which allows us to constrain the relation between X-ray
temperature and luminosity, including its scatter, simultaneously with
cosmological parameters. We find a luminosity-temperature relation in good
agreement with the results of Ikebe et al. (2002), while for the matter power
spectrum normalization, we find $\sigma_8 = 0.78_{-0.06}^{+0.30}$ at 95 per
cent confidence for $\Omega_0 = 0.35$. Scaling to WMAP's central value of
$\Omega_0 = 0.27$ would give a best-fit value of $\sigma_8 \simeq 0.9$.


title: Discrete Intrinsic Redshifts from Quasars to Normal Galaxies

abstract:
  It is pointed out that the discrete velocities found by Tifft in galaxies are
harmonically related to the discrete intrinsic redshifts found in quasars. All
are harmonically related to the constant 0.062 +/- 0.001, and this is the
fourth independent analysis in which the redshift increment 0.062 has been
shown to be significant. It is concluded that there is a quantized component in
the redshift of both quasars and galaxies that has a common origin and is
unlikely to be Doppler-related.


title: Pycnonuclear burning and accreting neutron stars

abstract:
  We outline the phenomenon of deep crustal heating in transiently accreting
neutron stars. It is produced by nuclear transformations (mostly, by
pycnonuclear reactions) in accreted matter while this matter sinks to densities
rho > 10^{10} g/cc under the weight of freshly accreted material. We consider
then thermal states of transiently accreting neutron stars (with mean mass
accretion rates \dot{M}=(10^{-14}-10^{-9}) M_\odot/yr) determined by deep
crustal heating. In a simplified fashion we study how the thermal flux emergent
from such stars depends on the properties of superdense matter in stellar
interiors. We analyze the most important regulators of the thermal flux: strong
superfluidity in the cores of low-mass stars and fast neutrino emission (in
nucleon, pion-condensed, kaon-condensed, or quark phases of dense matter) in
the cores of high-mass stars. We compare the results with observations of soft
X-ray transients in quiescent states.


title: On the Antenna Beam Shape Reconstruction Using Planet Transit

abstract:
  The calibration of the in-flight antenna beam shape and possible
beamdegradation is one of the most crucial tasks for the upcoming Planck
mission. We examine several effects which could significantly influence the
in-flight main beam calibration using planet transit: the problems of the
variability of the Jupiter's flux, the antenna temperature and passing of the
planets through the main beam. We estimate these effects on the antenna beam
shape calibration and calculate the limits on the main beam and far sidelobe
measurements, using observations of Jupiter and Saturn. We also discuss
possible effects of degradation of the mirror surfaces and specify
corresponding parameters which can help us to determine these effects.


title: Optical Photometry of GRB 021004: The First Month

abstract:
  We present U,B,V,R_C,and I_C photometry of the optical afterglow of the
gamma-ray burst GRB 021004 taken at the Nordic Optical Telescope between
approximately eight hours and 30 days after the burst. This data is combined
with an analysis of the 87 ksec Chandra X-ray observations of GRB 021004 taken
at a mean epoch of 33 hours after the burst to investigate the nature of this
GRB. We find an intrinsic spectral slope at optical wavelengths of beta_UH =
0.39 +/- 0.12 and an X-ray slope of beta_X = 0.94 +/- 0.03. There is no
evidence for colour evolution between 8.5 hours and 5.5 days after the burst.
The optical decay becomes steeper approximately five days after the burst. This
appears to be a gradual break due to the onset of sideways expansion in a
collimated outflow. Our data suggest that the extra-galactic extinction along
the line of sight to the burst is between A_V = 0.3 and A_V = 0.5 and has an
extinction law similar to that of the Small Magellanic Cloud. The optical and
X-ray data are consistent with a relativistic fireball with the shocked
electrons being in the slow cooling regime and having an electron index of p =
1.9 +/- 0.1. The burst occurred in an ambient medium that is homogeneous on
scales larger than approximately 10e18 cm but inhomogeneous on smaller scales.
The mean particle density is similar to what is seen for other bursts (0.1 < n
< 100 cm^{-3}). Our results support the idea that the brightening seen
approximately 0.1 days was due to interaction with a clumpy ambient medium
within 10^{17} and 10^{18} cm of the progenitor. The agreement between the
predicted optical decay and that observed approximately ten minutes after the
burst suggests that the physical mechanism controlling the observed flux
approximately ten minutes is the same as the one operating at t > 0.5 days.


title:
CMB Polarization towards Clusters as a Probe of the Integrated
  Sachs-Wolfe Effect

abstract:
  The scattering of temperature anisotropy quadrupole by free electrons in
galaxy clusters leads to a now well-known polarization signal in the cosmic
microwave background (CMB) fluctuations. Using multi-frequency polarization
data, one can extract the temperature quadrupole and separate it from the
contaminant polarization associated with the kinematic quadrupole due to
transverse motion of clusters. At low redshifts, the temperature quadrupole
contains a significant contribution from the integrated Sachs-Wolfe effect
(ISW) associated with the growth of density fluctuations. Using polarization
data from a sample of clusters over a wide range in redshift, one can
statistically establish the presence of the ISW effect and determine the
redshift dependence of the ISW contribution to the rms quadrupole. Given the
strong dependence of the ISW effect on the background cosmology, the cluster
polarization can eventually be used as a probe of the dark energy.


title: Correlations of Richness and Global Properties in Galaxy Clusters

abstract:
  We measure the optical richness of galaxy clusters from the CNOC1 cluster
redshift survey using the galaxy-cluster center correlation amplitude B_gc. We
show that the B_gc values measured using photometric catalogs are consistent
with those derived from redshift catalogs, indicating that richness can be
measured reliably from photometric data alone, even at moderate redshifts of
\~0.6. We establish the correlations between optical richness and other
important attributes of a galaxy cluster, such as velocity dispersion, mass,
radius, and X-ray temperature and luminosity. We find that the scaling
relations of these quantities with richness are entirely consistent with those
derived by assuming a simple mass density profile at 0.5 Mpc of rho~r^{-1.8}.
The excellent correlations between B_gc and velocity dispersion and X-ray
temperature allow one to use richness, an easily measurable quantity using
relatively shallow optical imaging data alone, as a predictor of these
quantities at moderate redshifts. The B_gc parameter can be used to estimate
the velocity dispersion of a cluster to a precision of approximately 15%
(~+/-100 km/s), and X-ray temperature to about 20%. Similar correlations, but
with larger scatter, are also obtained between richness and the characteristic
radius and mass of the clusters. We compare the relative merits of B_gc, T_x,
and L_x as predictors of the dynamical mass, and find that they are comparable,
providing estimates at an accuracy of ~30%. We also perform similar analyses of
correlations between richness and velocity dispersion, T_x and L_x with a
sample of low-redshift Abell clusters and find consistent results, but with
larger scatter, which may be the result of a less homogeneous database, or
sample-dependent effects.


title:
Missing Mass and the Acceleration of the Universe. Is Quintessence the
  only Explanation?

abstract:
  Detailed observations of the temperature fluctuations in the microwave
background radiation indicate that we live in an open universe. From the size
of these fluctuations it is concluded that the geometry of the universe is
quite close to Euclidean. In terms Friedmann models, this implies a mass
density within 10% of the critical density required for a flat universe.
Observed mass can only account for 30% of this mass density. Recently, an
outstanding observation revealed that cosmos is accelerating. This motivated
some astronomers to explain the missing 70% as some exotic dark energy called
quintessence. In this essay, we present an alternative explanation to these
cosmological issues in terms of the Friedmann Thermodynamics. This model has
the capability of making definite predictions about the geometry of the
universe, the missing mass problem, and the acceleration of the universe
in-line with the recent observations. For future observations, we also predict
where this model will start differing from the quintessence models.
  (This essay received an honorable mention in the Annual Essay Competition of
the Gravity Research Foundation for the year 2002-- Ed)


title: PLANET II: A Microlensing and Transit Search for Extrasolar Planets

abstract:
  Due to their extremely small luminosity compared to the stars they orbit,
planets outside our own Solar System are extraordinarily difficult to detect
directly in optical light. Careful photometric monitoring of distant stars,
however, can reveal the presence of exoplanets via the microlensing or
eclipsing effects they induce. The international PLANET collaboration is
performing such monitoring using a cadre of semi-dedicated telescopes around
the world. Their results constrain the number of gas giants orbiting 1--7 AU
from the most typical stars in the Galaxy. Upgrades in the program are opening
regions of ``exoplanet discovery space'' -- toward smaller masses and larger
orbital radii -- that are inaccessible to the Doppler velocity technique.


title: The topology of weak lensing field in the neighborhood of MS1054-03

abstract:
  We report the first measurement of genus curves for the two-dimensional mass
map in the neighborhood of rich, X-ray luminous galaxy cluster MS1054-03 at
z=0.83, reconstructed from weak lensing data obtained by Suprime-Cam on the
prime focus of 8.2m Subaru telescope. We find that the genus curve measured in
the whole survey field deviates from that expected from a random Gaussian
field. We show that this non-Gaussianity is induced by the rich cluster in this
region, and that the genus curve for the region without the cluster is
consistent with the prediction for a random Gaussian field. The results
demonstrate the feasibility of the genus statistics to examine the
non-Gaussianity due to the large scale structures and to probe the statistical
properties of the large scale clustering.


title: Infrared Light Curves of Type Ia Supernovae

abstract:
  This paper provides a progress report on a collaborative program at the Las
Campanas and Cerro Tololo Observatories to observe the near-IR light curves of
Type Ia supernovae. We discuss how the morphologies of the JHK light curves
change as a function of the decline rate. Evidence is presented which indicates
that the absolute magnitudes in the H band have little or no dependence on the
decline rate, suggesting that SNe Ia may be nearly perfect cosmological
standard candles in the near-IR. A preliminary Hubble diagram in the H band is
presented and compared with a similar diagram in V for the same objects.
Finally, observations of two peculiar supernovae, 1999ac and 2001ay, are
briefly discussed.


title: The XMM-Newton view of the radio-quiet neutron star 1E 1207.4-5209

abstract:
  We have observed the radio-quiet X-ray pulsar 1E 1207.4-5209 with the high
throughput EPIC cameras onboard XMM-Newton. The spectrum of this peculiar
source is characterized by two broad absorption features which present
significant substructures and show a clear phase-dependence. We believe that
these features represent a strong evidence for the presence of a magnetized
atmosphere containing heavy elements.


title: On the stability of thick accretion disks around black holes

abstract:
  Discerning the likelihood of the so-called runaway instability of thick
accretion disks orbiting black holes is an important issue for most models of
cosmic gamma-ray bursts. To this aim we investigate this phenomenon by means of
time-dependent, hydrodynamical simulations of black hole plus torus systems in
general relativity. The evolution of the central black hole is assumed to be
that of a sequence of Kerr black holes of increasing mass and spin, whose
growth rate is controlled by the transfer of mass and angular momentum from the
material of the disk spiralling in through the event horizon of the black hole.
The self-gravity of the disk is neglected. We find that when the black hole
mass and spin are allowed to increase, constant angular momentum disks undergo
a runaway instability on a dynamical timescale (a few orbital periods).
However, our simulations show that a slight increase of the specific angular
momentum of the disk outwards has a dramatic stabilizing effect. Our results,
obtained in the framework of general relativity, are in broad agreement with
earlier studies based both on stationary models and on time-dependent
simulations with Newtonian and pseudo-Newtonian gravitational potentials.


title: HST proper motion confirms the optical detection of PSR B1929+10

abstract:
  We have measured the proper motion of the candidate optical counterpart of
the old, nearby pulsar PSR B1929+10, using a set of HST/STIS images collected
in 2001, 7.2 years after the epoch of the original FOC detection (Pavlov et al.
1996). The yearly displacement, mu=107.3+/-1 mas/yr along a position angle of
64.6+/-0.6 deg, is fully consistent with the most recent VLBA radio
measurement. This result provides a robust confirmation of the identification
of PSR B1929+10 in the optical band.


title: Reduction of CCD observations with scanning Fabry-Perot interferometer

abstract:
  The algorithms used for reduction of data obtained in a Fabry-Perot
interferometer mode of the new focal reducer of the 6m telescope SCORPIO are
described. The main attention is focused on the procedures of photometry
correction of channels and night sky emission subtraction, which is especially
important for observations with a CCD in comparison with a photon counter. The
influence of various sources of errors on measurements of radial velocities in
a data cube is investigated. Examples of velocity field construction by using
emission lines in the galaxy NGC 6951 and absorption lines in the globular
cluster M 71 are presented.


title: Two-dimensional spectroscopy of double-barred galaxies

abstract:
  We describe the results of our spectroscopy for a sample of barred galaxies
whose inner regions exhibit an isophotal twist commonly called a secondary bar.
The line-of-sight velocity fields of the ionized gas and stars and the
light-of-sight velocity dispersion fields of the stars were constructed from
two-dimensional spectroscopy with the 6m Special Astrophysical Observatory
telescope. We detected various types of non-circular motions of ionized gas:
radial flows within large-scale bars, counter-rotation of the gas and stars at
the center of NGC 3945, a polar gaseous disk in NGC 5850, etc. Our analysis of
the optical and near-infrared images (both ground-based and those from the
Hubble Space Telescope) revealed circumnuclear minispirals in five objects. The
presence of an inner (secondary) bar in the galaxy images is shown to have no
effect on the circumnuclear kinematics of the gas and stars. Thus, contrary to
popular belief, the secondary bar is not a dynamically decoupled galactic
structure. We conclude that the so-called double-barred galaxies are not a
separate type of galaxies but are a combination of objects with distinctly
different morphology of their circumnuclear regions.


title: Can cosmology detect hierarchical neutrino masses?

abstract:
  We have carefully analysed the potential of future Cosmic Microwave
Background (CMB) and Large Scale Structure (LSS) measurements to probe neutrino
masses. We perform a Fisher matrix analysis on a 9-dimensional cosmological
parameter space and find that data from the Planck CMB experiment combined with
the Sloan Digital Sky Survey (SDSS) can measure a neutrino mass of 0.12 eV at
95% conf. This is almost at the level of the 0.06 eV mass suggested by current
neutrino oscillation data. A future galaxy survey with an order of magnitude
larger survey volume than the SDSS would allow for a neutrino mass
determination of 0.03-0.05 eV (95% conf.).


title: The cosmological dependence of weak interactions

abstract:
  A model for the cosmological time dependence of weak interactions is discused
and some experimental tests suggested.


title:
Optical observations of the bright long duration peculiar GRB 021004
  afterglow

abstract:
  The CCD magnitudes in Johnson $B,V$ and Cousins $R$ and $I$ photometric
passbands are determined for the bright long duration GRB 021004 afterglow from
2002 October 4 to 16 starting $\sim$ 3 hours after the $\gamma-$ray burst.
Light curves of the afterglow emission in $B$,$V$,$R$ and $I$ passbands are
obtained by combining these measurements with other published data. The
earliest optical emission appears to originate in a revese shock. Flux decay of
the afterglow shows a very uncommon variation relative to other well-observed
GRBs. Rapid light variations, especially during early times ($\Delta t < 2$
days) is superposed on an underlying broken power law decay typical of a jetted
afterglow. The flux decay constants at early and late times derived from least
square fits to the light curve are $0.99\pm0.05$ and $2.0\pm0.2$ respectively,
with a jet break at around 7 day. Comparison with a standard fireball model
indicates a total extinction of $E(B-V)=0.20$ mag in the direction of the
burst. Our low-resolution spectra corrected for this extinction provide a
spectral slope $\beta = 0.6\pm0.02$. This value and the flux decay constants
agree well with the electron energy index $p\sim 2.27$ used in the model. The
derived jet opening angle of about $7^{\circ}$ implies a total emitted
gamma-ray energy $E_{\gamma} = 3.5\times10^{50}$ erg at a cosmological distance
of about 20 Gpc. Multiwavelength observations indicate association of this GRB
with a star forming region, supporting the case for collapsar origin of long
duration GRBs.


title:
Novae In External Galaxies From The POINT-AGAPE Survey And The Liverpool
  Telescope

abstract:
  We have recently begun a search for Classical Novae in M31 using three years
of multicolour data taken by the POINT-AGAPE microlensing collaboration with
the 2.5m Isaac Newton Telescope (INT) on La Palma. This is a pilot program
leading to the use of the Liverpool Telescope (LT) to systematically search for
and follow novae of all speed classes in external galaxies to distances up to
around 5Mpc.


title: Diagnosing magnetars with transient cooling

abstract:
  Transient X-ray emission, with an approximate t^{-0.7} decay, was observed
from SGR 1900+14 over 40 days following the the giant flare of 27 Aug 1998. We
calculate in detail the diffusion of heat to the surface of a neutron star
through an intense 10^{14}-10^{15} G magnetic field, following the release of
magnetic energy in its outer layers. We show that the power law index, the
fraction of burst energy in the afterglow, and the return to persistent
emission can all be understood if the star is composed of normal baryonic
material.


title: Iron abundances in hydrodynamical simulations of galaxy clusters

abstract:
  Hydrodynamical SPH simulations of galaxy clusters are used to investigate the
metal enrichment of the intracluster medium. The final metallicity abundances
of the simulated clusters are determined according to the numerical resolution
and a number of model parameters. For a fiducial set of model prescriptions the
results of the simulations indicate iron abundances in broad agreement with
data. Final X-ray properties are not sensitive to the heating of the ICM. This
supports a scenario where the ICM evolution of cool clusters is driven by
radiative cooling.


title:
A Chandra detection of diffuse hard X-ray emission associated with the
  lobes of the radio galaxy 3C 452

abstract:
  An 80 ksec Chandra ACIS observation of the radio galaxy 3C 452 is reported. A
diffuse X-ray emission associated with the lobes has been detected with high
statistical significance, together with the X-ray nucleus of the host galaxy.
The 0.5--5 keV ACIS spectrum of the diffuse emission is described by a
two-component model, consisting of a soft thermal plasma emission from the host
galaxy halo and a hard non-thermal power-law component. The hard component is
ascribed to the inverse Comptonization of cosmic microwave background photons
by the synchrotron emitting electrons in the lobes, because its spectral energy
index, 0.68+-0.28, is consistent with the radio synchrotron index, 0.78. These
results reveal a significant electron dominance in the lobes. The electrons are
inferred to have a relatively uniform distribution, while the magnetic field is
compressed toward the lobe periphery.


title:
Non-Keplerian rotation in the nucleus of NGC 1068: evidence for a
  massive accretion disk?

abstract:
  The nucleus of the Seyfert galaxy NGC 1068 is believed to host a supermassive
black hole. Evidence for the presence of a massive central object is provided
by water maser emission, which displays a linear pattern in the sky, suggestive
of a rotating disk. The rotating disk hypothesis is further strengthened by the
declining shape of the derived rotation curve. Similar maser emission from NGC
4258 has led to a reliable estimate of the mass of the central black hole,
because in this case the rotation curve is Keplerian. In the case of NGC 1068
the rotation curve traced by the water maser is non-Keplerian. In this paper we
provide an interpretation of the non-Keplerian rotation in NGC 1068 by means of
a self-gravitating accretion disk model. We obtain a good fit to the available
data and derive a black hole mass M_{bh}=(8.0\pm 0.3) 10^6M_{sun}. The
resulting disk mass is comparable to the black hole mass. As an interesting
by-product of our fitting procedure, we are able to estimate the viscosity
parameter, which turns out to be \alpha\approx 10^{-2}, in line with some
theoretical expectations.


title: Recent highlights in the X-ray study of blazars

abstract:
  Blazars exhibit flux and spectral variations of largest amplitude at the
highest frequencies. Therefore, monitoring their variability at X- and
gamma-rays is the most effective tool to peer into the mighty powerhouse of
these sources. High energy observations of the brightest blazars with the
latest generation of satellites have allowed a detailed study of their behavior
and have critically improved our understanding of the physics of blazar jets. I
will review some of the recent results of blazar multiwavelength monitoring
with emphasis on the X-ray campaigns accomplished with BeppoSAX and I will
describe some of the future programs for blazar investigation from space,
particularly with INTEGRAL.


title: Lithium Depletion Boundary in a Pre-Main Sequence Binary System

abstract:
  A lithium depletion boundary is detected in HIP 112312 (GJ 871.1 A and B), a
\~12 Myr old pre-main sequence binary system. A strong (EW 300 mA) Li 6708 A
absorption feature is seen at the secondary (~M4.5) while no Li 6708 A feature
is detected from the primary (~M4). The physical companionship of the two stars
is confirmed from common proper motions. Current theoretical pre-main sequence
evolutionary models cannot simultaneously match the observed colors,
brightnesses, and Li depletion patterns of this binary system. At the age upper
limit of 20 Myr, contemporary theoretical evolutionary models predict too slow
Li depletion. If true Li depletion is a faster process than predicted by
theoretical models, ages of open clusters (Pleiades, alpha Persei, and IC 2391)
estimated from the Li depletion boundary method are all overestimated. Because
of the importance of the open cluster age scale, development of self-consistent
theoretical models to match the HIP 112312 data is desirable.


title: The Magnetic Field in the Convection Zone

abstract:
  One of the key questions in solar physics that remains to be answered
concerns the strength and the distribution of the magnetic fields at the base
of the convection zone. The flux tube dynamics requires that toroidal fields of
strength as large as 100 kilogauss be present at the base of the convection
zone. The kinetic-magnetic equipartition argument leads to smaller field
strengths. For possible detection of these relatively small (compared to
pressure effects) fields by helioseismic methods it is important to know the
range of the field strengths and their distribution.
  We estimate a range for the toroidal magnetic field strengths at the base of
the convection zone using dynamo simulations in a spherical shell. These
simulations involve the distribution of rotation provided by helioseismic
inversions of the GONG and MDI data. Combining the simulations with the
observed line-of-sight surface poloidal field we extract the spatial pattern
and magnitude of the mean toroidal magnetic field at the base of the convection
zone.


title:
The 2MASS Wide-Field T Dwarf Search. I. Discovery of a Bright T Dwarf
  Within 10 pc of the Sun

abstract:
  We present the discovery of a bright (J = 13.94$\pm$0.03) T dwarf, 2MASS
1503+2525, identified in a new, wide-field search for T dwarfs using the
recently completed Two Micron All Sky Survey (2MASS). The 1--2.5 $\micron$
spectrum of this object exhibits the strong H$_2$O and CH$_4$ bands
characteristic of mid- and late-type T dwarfs, and we derive a spectral type of
T5.5 using both the Burgasser et al. and the Geballe et al. classification
schemes. Based on its spectral type and the absolute magnitudes of known T
dwarfs, we estimate the distance of this object as 8$\pm$3 pc if it is single,
likely within 10 pc of the Sun. Our new 2MASS search, which covers 74% of the
sky and greatly expands on earlier color constraints, should identify 15--25
new T dwarfs with J $\leq$ 16. Combined with the 20 known members of this class
that already fall within our search criteria, our new sample will provide
improved statistics for such key quantities as the binary fraction and the
field substellar mass function. Furthermore, multiple detections from
overlapping 2MASS scans provide multiple epoch astrometry and photometry, and
we present proper motions for five T dwarfs in our sample.


title: The Independence of AGN Black Hole Mass and Radio-Loudness

abstract:
  We revisit the issue of whether radio loudness in AGN is associated with
central black hole mass, as has been suggested in the literature. We present
new estimates of black hole mass for 295 AGN (mostly radio-quiet), calculating
their radio loudnesses from published radio and optical fluxes, and combine
with our previously published values, for a sample of 452 AGN for which both
black hole mass and radio loudness (or upper limits thereto) are known. Among
the radio-quiet AGN, there are now many black holes with mass larger than
$10^{9}$ $M_{\odot}$, extending to the same high black hole masses as
radio-loud AGN of the same redshifts. Over the full sample, the black hole
masses of radio-loud and radio-quiet AGN span the same large range, $10^6 -
10^{10} M_\odot$. We conclude that radio loudness in AGN does not depend
strongly on central black hole mass.


title:
The Search for the Sidereal and Solar Diurnal Modulations in the Total
  MACRO Muon Data Set

abstract:
  We have analyzed 44.3M single muons collected by MACRO from 1991 through 2000
in 2,145 live days of operation. We have searched for the solar diurnal,
apparent sidereal, and pseudo-sidereal modulation of the underground muon rate
by computing hourly deviations of the muon rate from 6 month averages. We find
evidence for statistically significant modulations with the solar diurnal and
the sidereal periods. The amplitudes of these modulations are <0.1%, and are at
the limit of the detector statistics. The pseudo-sidereal modulation is not
statistically significant.
  The solar diurnal modulation is due to the daily atmospheric temperature
variations at 20 km, the altitude of primary cosmic ray interactions with the
atmosphere; MACRO is the deepest experiment to report this result. The sidereal
modulation is in addition to the expected Compton-Getting modulation due to
solar system motion relative to the Local Standard of Rest; it represents
motion of the solar system with respect to the galactic cosmic rays toward the
Perseus spiral arm.


title: H1320+551: A Seyfert 1.8/1.9 galaxy with an unabsorbed X-ray spectrum

abstract:
  We present new optical spectroscopic and XMM-Newton X-ray observations of the
Active Galactic Nucleus H1320+551. The optical data (consistent with but of
better quality than a previously published spectrum) show this source to be a
Seyfert 1.8/1.9 galaxy at z=0.0653. The narrow line region is significantly
reddened, with a Balmer decrement Ha/Hb~6 and the broad line region, with a
barely detectable Hb broad component, shows a much pronnounced Balmer decrement
(Ha/Hb>27). In spite of this, the EPIC-pn X-ray spectrum exhibits a power-law
continuum with a soft excess that is well fitted by a black body, with no
photoelectric absorption above the Galactic value. A Fe K emission line is also
seen at a rest-frame energy ~6.5 keV with an equivalent width of ~400 eV, far
too weak for the source being Compton-thick. Reconciling the optical and X-ray
data requires the narrow line region being internally reddened but with small
covering factor over the nuclear emission and the Balmer decrement of the broad
line region being an intrinsic property rather than caused by
reddening/absorption. The H1320+551 Seyfert 1.8/1.9 galaxy is not consistent
with being an obscured Seyfert 1 nucleus, i.e., it does not match the basic AGN
unified scheme hypothesis.


title: Lightcurve Classification in Massive Variability Surveys

abstract:
  This paper pioneers the use of neural networks to provide a fast and
automatic way to classify lightcurves in massive photometric datasets. As an
example, we provide a working neural network that can distinguish microlensing
lightcurves from other forms of variability, such as eruptive, pulsating,
cataclysmic and eclipsing variable stars. The network has five input neurons, a
hidden layer of five neurons and one output neuron. The five input variables
for the network are extracted by spectral analysis from the lightcurve
datapoints and are optimised for the identification of a single, symmetric,
microlensing bump. The output of the network is the posterior probability of
microlensing. The committee of neural networks successfully passes tests on
noisy data taken by the MACHO collaboration. When used to process 5000
lightcurves on a typical tile towards the bulge, the network cleanly identifies
the single microlensing event. When fed with a sub-sample of 36 lightcurves
identified by the MACHO collaboration as microlensing, the network corroborates
this verdict in the case of 27 events, but classifies the remaining 9 events as
other forms of variability. For some of these discrepant events, it looks as
though there are secondary bumps or the bump is noisy or not properly
contained. Neural networks naturally allow for the possibility of novelty
detection -- that is, new or unexpected phenomena which we may want to follow
up. The advantages of neural networks for microlensing rate calculations, as
well as the future developments of massive variability surveys, are both
briefly discussed.


title: Evolution of the accretion disk in the nucleus of NGC 1097

abstract:
  We discuss the long-term evolution of the broad double-peaked H alpha profile
of the LINER/Seyfert 1 nucleus of NGC 1097. Besides the previously known
variation of the relative intensities of the blue and red peaks, the profile
has recently shown an increasing separation between the two peaks, at the same
time as the integrated flux has decreased. We successfully model these
variations using a precessing asymmetric accretion disk with a varying
emissivity law. We interpret the emissivity variation as due to the fact that
the source of ionization is getting dimmer, causing the region of maximum
emission to drift inwards (and thus to regions of higher velocities). In
addition, in the last 3 yrs of observations, the central wavelength of the
double-peaked line has shifted to bluer wavelengths, which may be due to a wind
from the disk. It is the first time that such evolution is observed so clearly,
giving additional support for an accretion disk as the origin of the
double-peaked profile in NGC 1097.


title:
Multiple Methods for Estimating the Bispectrum of the Cosmic Microwave
  Background with Application to the MAXIMA Data

abstract:
  We describe different methods for estimating the bispectrum of Cosmic
Microwave Background data. In particular we construct a minimum variance
estimator for the flat-sky limit and compare results with previously-studied
frequentist methods. Application to the MAXIMA dataset shows consistency with
primordial Gaussianity. Weak quadratic non-Gaussianity is characterised by a
tunable parameter $f_{NL}$, corresponding to non-Gaussianity at a level $\sim
10^{-5}f_{NL}$ (ratio of non-Gaussian to Gaussian terms), and we find limits of
$|f_{NL}|<950$ for the minimum-variance estimator and $|f_{NL}|<1650$ for the
usual frequentist estimator. These are the tightest limits on primordial
non-Gaussianity which include the full effects of the radiation transfer
function.


title: XTE J1946+274 = GRO J1944+26: An Enigmatic Be/X-ray Binary

abstract:
  XTE J1946+274 = GRO J1944+26 is a 15.8 s Be/X-ray pulsar discovered
simultaneously in 1998 September with the Burst and Transient Source Experiment
(BATSE) on the Compton Gamma Ray Observatory (CGRO) and the All-Sky Monitor
(ASM) on the Rossi X-ray Timing Explorer (RXTE). Here we present new results
from BATSE and {\em RXTE} including a pulse timing analysis, spectral analysis,
and evidence for an accretion disk. Our pulse timing analysis yielded an
orbital period of 169.2 days, a moderate eccentricity of 0.33, and implied a
mass function of 9.7 M_sun. We observed evidence for an accretion disk, a
correlation between measured spin-up rate and flux, which was fitted to obtain
a distance estimate of 9.5 +/- 2.9 kpc. XTE J1946+274 remained active from 1998
September - 2001 July, undergoing 13 outbursts that were not locked in orbital
phase. Comparing RXTE PCA observations from the initial bright outburst in 1998
and the last pair of outbursts in 2001, we found energy and intensity dependent
pulse profile variations in both outbursts and hardening spectra with
increasing intensity during the fainter 2001 outbursts. In 2001 July, optical
Halpha observations indicate a density perturbation appeared in the Be disk as
the X-ray outbursts ceased. We propose that the equatorial plane of the Be star
is inclined with respect to the orbital plane in this system and that this
inclination may be a factor in the unusual outburst behavior of the system.


title:
X-ray emission from radio-quiet quasars in the SDSS Early Data Release.
  The alpha_ox dependence upon UV luminosity

abstract:
  We investigate the X-ray properties of the color-selected radio-quiet quasars
(RQQs) in the Sloan Digital Sky Survey (SDSS) Early Data Release using ROSAT,
Chandra, and XMM-Newton data. In the 0.16-6.28 redshift range, 136 RQQs have
X-ray detections (69 from the ROSAT All-Sky Survey, RASS), while for 70 RQQs
X-ray upper limits are obtained. The well-defined selection method utilized by
the SDSS, coupled with the tight radio constraints from the FIRST/NVSS surveys,
allow us to define a representative sample of optically selected RQQs whose
broad-band spectral energy distributions (characterized by means of the
optical-to-X-ray spectral index, alpha_ox) can be studied as a function of
rest-frame ultraviolet (UV) luminosity and redshift. A partial correlation
analysis applied to the SDSS sample (including the upper limits, but excluding
the biased subsample of RASS detections) shows that alpha_ox is a function of
rest-frame UV luminosity (i.e., alpha_ox steepens at high UV luminosities);
this correlation is significant at the 3.7 sigma level. We do not detect a
highly significant redshift dependence of alpha_ox. We also find a significant
(7.8 sigma level) correlation between UV and X-ray luminosity. This
correlation, parameterized by Lx \propto Luv^{0.75+/-0.06}, extends previous
results to the highest redshifts.


title:
Gravitationally redshifted absorption lines in the X-ray burst spectra
  of a neutron star

abstract:
  The fundamental properties of neutron stars provide a direct test of the
equation of state of cold nuclear matter, a relationship between pressure and
density that is determined by the physics of the strong interactions between
the particles that constitute the star. The most straightforward method of
determining these properties is by measuring the gravitational redshift of
spectral lines produced in the neutron star photosphere. The equation of state
implies a mass-radius relation, while a measurement of the gravitational
redshift at the surface of a neutron star provides a direct constraint on the
mass-to-radius ratio. Here we report the discovery of signficant absorption
lines in the spectra of 28 bursts of the low-mass X-ray binary EXO 0748-676. We
identify the most signficant features with the Fe XXVI and XXV n=2-3 and O VIII
n=1-2 transitions, all with a redshift of z=0.35, identical within small
uncertainties for the respective transitions. For an astrophysically plausible
range of masses (M ~ 1.3-2.0 M_solar), this value is completely consistent with
models of neutron stars composed of normal nuclear matter, while it excludes
some models in which the neutron stars are made of more exotic matter.


title: Galaxy Clustering Evolution in the UH8K Weak Lensing Fields

abstract:
  We present measurements of the two-point galaxy angular correlation function
as a function of apparent magnitude, color, and morphology. We present new
galaxy number counts to limiting magnitudes of I=24.0 and V=25.0. We find
$\omega(\theta)$ to be well described by a power-law of slope -0.8. We find the
amplitude of the correlation function to decrease monotonically with
increasingly faint apparent magnitude. We compare with predictions utilizing
redshift distributions based on deep spectroscopic observations. We conclude
that simple redshift-dependent models which characterize evolution by means of
the epsilon parameter inadequately describe the observations. We find a strong
clustering dependence on V-I color because galaxies of extreme color lie at
similar redshifts and the angular correlation functions for these samples are
minimally diluted by chance projections.
  We then present the first attempt to investigate the redshift evolution of
clustering, utilizing a population of galaxies of the same morphological type
and absolute luminosity. We study the dependence of $\omega(\theta)$ on
redshift for Lstar early-type galaxies in the redshift range 0.2<z<0.9.
Although uncertainties are large, we find the evolution in the clustering of
these galaxies to be consistent with stable clustering [epsilon=0]. We find
Lstar early-type galaxies to cluster slightly more strongly (rnought =
5.25\pm0.28 \hMpc assuming epsilon=0) than the local full field population.
This is in good agreement with the 2dFGRS value for Lstar early-type galaxies
in the local universe (abridged).


title: Shadowing-based reliability decay in softened n-body simulations

abstract:
  A shadow of a numerical solution to a chaotic system is an_exact_ solution to
the equations of motion that remains close to the numerical solution for a long
time. In a collisionless n-body system, we know that particle motion is
governed by the global potential rather than by inter-particle interactions. As
a result, the trajectory of each individual particle in the system is
independently shadowable. It is thus meaningful to measure the number of
particles that have shadowable trajectories as a function of time. We find that
the number of shadowable particles decays exponentially with time as exp(-mu
t), and that for eps in [~0.2,1] (in units of the local mean inter-particle
separation $\bar n$), there is an explicit relationship between the decay
constant mu, the timestep h of the leapfrog integrator, the softening eps, and
the number of particles N in the simulation. Thus, given N and eps, it is
possible to pre-compute the timestep h necessary to acheive a desired fraction
of shadowable particles after a given length of simulation time. We demonstrate
that a large fraction of particles remain shadowable over ~100 crossing times
even if particles travel up to about 1/3 of the softening length per timestep.
However, a sharp decrease in the number of shadowable particles occurs if the
timestep increases to allow particles to travel further than 1/3 the softening
length in one timestep, or if the softening is decreased below ~0.2$\bar n$.


title: X-ray background synthesis: the infrared connection

abstract:
  We present a synthesis model of the X-ray background based on the
cross-correlation between mid-infrared and X-ray surveys, where the
distribution of type 2 sources is assumed to follow that of luminous infrared
galaxies while type 1 sources are traced by the observed ROSAT distribution.
The best fits to both the X-ray number counts and background spectrum require
at least some density evolution. We explore a limited range of parameter space
for the evolutionary variables of the type 2 luminosity function. Matching the
redshift distribution to that observed in deep Chandra and XMM fields, we find
weak residuals as a signature of Fe emission from sources in a relatively
peaked range of redshift. This extends the recent work of Franceschini et al.,
and emphasizes the possible correlation between obscured AGN and star-forming
activity.


title:
The unusual optical afterglow of the gamma-ray burst GRB 021004: Color
  changes and short-time-scale variability

abstract:
  We report UBVRI observations of the optical afterglow of the gamma-ray burst
GRB 021004. We observed significant (10-20%) deviations from a power law decay
on several time scales, ranging from a few hours down to 20-30 minutes. We also
observed a significant color change starting ~1.5 days after the burst,
confirming the spectroscopic results already reported by Matheson et al.
(2002). We discuss these results in the context of several models that have
recently been proposed to account for the anomalous photometric behavior of
this event.